Document:

<PAGE>

                                                                      1999 LEASE

                                TABLE OF CONTENTS

1.    LEASE OF PREMISES .............................................  1

2.    DEFINITIONS ...................................................  1

3.    EXHIBITS AND ADDENDA ..........................................  3

4.    DELIVERY OF POSSESSION ........................................  3

5.    INTENDED USE OF THE PREMISES ..................................  3

6.    RENT ..........................................................  3
      6.1.    Payment of Rent .......................................  3
      6.2.    Adjusted Base Rent ....................................  3
      6.3.    Additional Rent for Increases in Tax Costs and
              Operating Expenses ....................................  4
      6.4.    Definition of Rent ....................................  6
      6.5.    Taxes on Tenant's Use and Occupancy ...................  6

7.    LATE CHARGES ..................................................  6

8.    SECURITY DEPOSIT ..............................................  6

9.    TENANT'S USE OF THE PREMISES ..................................  7
      9.1.    Use ...................................................  7
      9.2.    Observance of Law .....................................  7
      9.3.    Insurance .............................................  7
      9.4.    Nuisance and Waste ....................................  8
      9.5.    Load and Equipment Limits .............................  8
      9.6.    Hazardous Material ....................................  8

10.   SERVICES AND UTILITIES ........................................  8

11.   REPAIRS AND MAINTENANCE .......................................  9
      11.1.   Landlord's Obligations ................................  9
      11.2.   Tenant's Obligations ..................................  9
      11.3.   Compliance with Law ................................... 10
      11.4.   Notice of Defect ...................................... 10
      11.5.   Landlord's Liability .................................. 10

12.   CONSTRUCTION, ALTERATIONS AND ADDITIONS ....................... 10
      12.1.   Landlord's Construction Obligations ................... 10
      12.2.   Tenant's Construction Obligations ..................... 10
      12.3.   Tenant's Alterations and Additions .................... 10
      12.4.   Payment ............................................... 11
      12.5.   Property of Landlord .................................. 11

13.   LEASEHOLD IMPROVEMENTS; TENANT'S PROPERTY ..................... 11
      13.1.   Leasehold Improvements ................................ 11
      13.2.   Tenant's Property ..................................... 11

14.   INDEMNIFICATION ............................................... 11
      14.1.   Tenant Indemnification ................................ 11
      14.2.   Landlord Not Liable ................................... 11

15.   TENANT'S INSURANCE ............................................ 12
      15.1.   Insurance Requirement ................................. 12
      15.2.   Minimum Scope of Coverage ............................. 12
      15.3.   Minimum Limits of Insurance ........................... 13
      15.4.   Deductible and Self-Insured Retention ................. 13
      15.5.   Increases in Insurance Policy Limits .................. 13
      15.6.   Waiver of Subrogation ................................. 13
      15.7.   Landlord's Right to Obtain Insurance for Tenant ....... 13

16.   DAMAGE OR DESTRUCTION ......................................... 13
      16.1.   Damage ................................................ 13
      16.2.   Repair of Premises in Excess of One Hundred
              Eighty Days ........................................... 13
      16.3.   Repair Outside Premises ............................... 14
      16.4.   Tenant Repair ......................................... 14
      16.5.   Election Not to Perform Landlord's Work ............... 14
      16.6.   Express Agreement ..................................... 14

17.   EMINENT DOMAIN ................................................ 14
      17.1.   Whole Taking .......................................... 14
      17.2.   Partial Taking ........................................ 14
      17.3.   Proceeds .............................................. 14
      17.4.   Landlord's Restoration ................................ 14

                                       i
<PAGE>

18. ASSIGNMENT AND SUBLETTING ....................................... 15
      18.1.   No Assignment or Subletting ........................... 15
      18.2.   Landlord's Consent .................................... 15
      18.3.   Tenant Remains Responsible ............................ 16
      18.4.   Conversion to a Limited Liability Entity .............. 16
      18.5.   Payment of Fees ....................................... 16

19.   DEFAULT ....................................................... 16
      19.1.   Tenant's Default ...................................... 16
      19.2.   Landlord Remedies ..................................... 17
      19.3.   Damages Recoverable ................................... 18
      19.4.   Landlord's Right to Cure Tenant's Default ............. 18
      19.5.   Landlord's Default .................................... 18
      19.6.   Mortgagee Protection .................................. 18
      19.7.   Tenant's Right to Cure Landlord's Default ............. 18

20.   WAIVER ........................................................ 18

21.   SUBORDINATION AND ATTORNMENT .................................. 19

22.   TENANT ESTOPPEL CERTIFICATES .................................. 19
      22.1.   Landlord Request for Estoppel Certificate ............. 19
      22.2.   Failure to Execute .................................... 19

23.   NOTICE ........................................................ 19

24.   TRANSFER OF LANDLORD'S INTEREST ............................... 20

25.   SURRENDER OF PREMISES ......................................... 20
      25.1.   Clean and Same Condition .............................. 20
      25.2.   Failure to Deliver Possession ......................... 20
      25.3.   Property Abandoned .................................... 20

26.   HOLDING OVER .................................................. 20

27.   RULES AND REGULATIONS ......................................... 20

28.   CERTAIN RIGHTS RESERVED BY LANDLORD ........................... 21

29.   ADVERTISEMENTS AND SIGNS ...................................... 21

30.   RELOCATION OF PREMISES ........................................ 21

31.   GOVERNMENT ENERGY OR UTILITY CONTROLS ......................... 21

32.   FORCE MAJEURE ................................................. 22

33.   BROKERAGE FEES ................................................ 22

34.   QUIET ENJOYMENT ............................................... 22

35.   TELECOMMUNICATIONS ............................................ 22
      35.1.   Telecommunications Companies .......................... 22
      35.2.   Tenant's Obligations .................................. 22
      35.3.   Landlord's Consent .................................... 23
      35.4.   Indemnification ....................................... 23
      35.5.   Landlord's Operation of Building Telecommunications
              Lines and Systems ..................................... 23

36.   MISCELLANEOUS ................................................. 23
      36.1.   Accord and Satisfaction; Allocation of Payments ....... 23
      36.2.   Addenda ............................................... 23
      36.3.   Attorneys' Fees ....................................... 24
      36.4.   Captions and Section Numbers .......................... 24
      36.5.   Changes Requested by Lender ........................... 24
      36.6.   Choice of Law ......................................... 24
      36.7.   Consent ............................................... 24
      36.8.   Authority ............................................. 24
      36.9.   Waver of Right to Jury Trial .......................... 24
      36.10.  Counterparts .......................................... 24
      36.11.  Execution of Lease; No Option ......................... 24
      36.12.  Furnishing of Financial Statements; Tenant's
              Representations ....................................... 24
      36.13.  Further Assurances .................................... 24
      36.14.  Prior Agreements; Amendments .......................... 24
      36.15.  Recording ............................................. 25
      36.16.  Severability .......................................... 25
      36.17.  Successors and Assigns ................................ 25
      36.18.  Time of the Essence ................................... 25

                                       ii
<PAGE>

                                      LEASE

This lease (the Lease) between Glenborough Fund V, Limited Partnership, a
Delaware limited partnership (herein Landlord), and Sonus Networks, Inc., a
Delaware Corporation (herein Tenant), is dated for reference purposes only as of
this 21st day of January, 1999.

1.    LEASE OF PREMISES.

In consideration of the Rent (as defined in Section 6.) and the provisions of
this Lease, Landlord leases to Tenant and Tenant leases from Landlord the
Premises shown by diagonal lines on the floor plan attached hereto as Exhibit
"A", and further described in Section 2.13. The Premises are located within the
Building and Project (as described in Sections 2.13. and 2.14.). Tenant shall
have the nonexclusive right (unless otherwise provided herein) in common with
Landlord, other tenants, subtenants and invitees, to use the Common Area (as
defined in Section 2.5.).

2.    DEFINITIONS.

As used in this Lease the following terms shall have the following meanings:

      2.2.  ANNUAL BASE RENT:

          $664,640.00 beginning April 1, 1999 ending March 31, 2000
          $685,410.00 beginning April 1, 2000 ending March 31, 2001
          $706,180.00 beginning April 1, 2001 ending March 31, 2002
          $726,950.00 beginning April 1, 2002 ending March 31, 2003
          $747,720.00 beginning April 1, 2003 ending March 31, 2004

      2.3.  BASE YEAR (Section 6.3.): operating expenses calendar year 1999
                                      Real Estate taxes fiscal year 1999.

      2.4.  COMMENCEMENT DATE: April 1, 1999. If the Commencement Date is other
            than the first day of a month, then the Expiration Date of the Lease
            shall be extended to the last day of the month in which the Lease
            expires.

      2.5.  COMMON AREA: The building lobbies, common corridors and hallways,
            rest rooms, parking areas and other generally understood public or
            common areas.

      2.6.  EXPIRATION DATE: March 31, 2004, unless otherwise sooner terminated
            in accordance with the provisions of this Lease.

      2.8.  LANDLORD'S ADDRESS FOR NOTICE:

               Glenborough Properties, L.P.
               c/o Glenborough Realty Trust Incorporated
               400 South El Camino Real, Suite 1100
               San Mateo, CA 94402-1708
               Attn: Legal Department

            RENT PAYMENT ADDRESS:

               Glenborough Fund V, L.P. c/o
               Glenborough Realty Trust, Inc.
               300 Nickerson Road
               Marlborough, MA 01752

            TENANT'S MAILING ADDRESS:

               Sonus Networks, Inc.
               5 Carlisle Road
               Westford, MA 01886

                                       1
<PAGE>

      2.9.  LISTING AND LEASING AGENT(S): Boston Real Estate Partners

      2.10. MONTHLY INSTALLMENTS OF BASE RENT:

           $55,386.67 beginning  April 1, 1999  ending  March 31, 2000
           $57,117.50 beginning  April 1, 2000  ending  March 31, 2001
           $58,848.33 beginning  April 1, 2001  ending  March 31, 2002
           $60,579.17 beginning  April 1, 2002  ending  March 31, 2003
           $62,310.00 beginning  April 1, 2003  ending  March 31, 2004

      2.11. NOTICE: Except as otherwise provided herein, Notice shall mean any
            notices, approvals and demands permitted or required to be given
            under this Lease. Notice shall be given in the form and manner set
            forth in Section 23.

      2.12. PARKING: Tenant shall be entitled to the nonexclusive use of 125
            parking spaces. The charge for parking shall be 0 per month per
            parking space. Landlord may permit Tenant to rent additional spaces,
            if available, at the then current parking rate. Each such additional
            parking space, however, shall not be a part of this Lease, and
            Landlord reserves the right to adjust the parking rate for each
            additional parking space at any time and to terminate the rental of
            such additional parking spaces at any time.

      2.13. PREMISES: That portion of the 2nd floor(s) of the Building located
            at 5 Carlisle Road, Westford, MA, commonly referred to as Suite(s)
            2E-01 & 2W-01, as shown by diagonal lines on Exhibit "A". For
            purposes of this Lease, the Premises is deemed to contain
            approximately 41,540.00 square feet of Rentable Area.

      2.14. PROJECT: The building of which the Premises are a part (the
            Building) and any other buildings or improvements on the real
            property (the Property) located at 5 Carlisle Road, Westford, MA
            01886 and further described in Exhibit "B". The Project is commonly
            known as Phase 1, Westford Corporate Center.

      2.15. RENTABLE AREA: As to both the Premises and the Project, the
            respective measurements of floor area as may from time to time be
            subject to lease by Tenant and all tenants of the Project,
            respectively, as determined by Landlord and applied on a consistent
            basis throughout the Project.

      2.16. SECURITY DEPOSIT (Section 8.): $166,160.01.

      2.17. STATE: The Commonwealth of Massachusetts.

      2.19. TENANT'S PROPORTIONATE SHARE: 50.89%. Such share is a fraction, the
            numerator of which is the Rentable Area of the Premises, and the
            denominator of which is the Rentable Area of the Project, as
            determined by Landlord from time to time. The Project consists of 1
            Building(s), and, for purposes of this Lease, the Building(s) are
            deemed to contain approximately 81,615 square feet of Rentable Area.

      2.20. TENANT'S USE (Section 9.): General Office and Light Manufacturing,
            final test, assembly and distribution of Telecommunications
            Equipment.

      2.21. TERM: The period commencing on the Commencement Date and expiring at
            midnight on the Expiration Date.

                                       2
<PAGE>

3.    EXHIBITS AND ADDENDA.

The exhibits and addenda listed below (unless lined out) are attached hereto and
incorporated by reference in this Lease:

      3.1.  Exhibit A - Floor Plan showing the Premises.
      3.2.  Exhibit B - Site Plan of the Project.
      3.3.  Exhibit C - Building Standard Tenant Improvements.
      3.4.  Exhibit D - Work Letter and Drawings.
      3.5.  Exhibit E - Rules and Regulations.
      3.6.  Addenda: Attached hereto and made a part of this Lease by reference
            are Sections 37-42.

4.    DELIVERY OF POSSESSION.

If for any reason Landlord does not deliver possession of the Premises to Tenant
on the Commencement Date, and such failure is not caused by an act or omission
of Tenant, the Expiration Date shall be extended by the number of days the
Commencement Date has been delayed and the validity of this Lease shall not be
impaired nor shall Landlord be subject to any liability for such failure; but
Rent shall be abated until delivery of possession. Provided, however, if the
Commencement Date has been delayed by an act or omission of Tenant then Rent
shall not be abated until delivery of possession and the Expiration Date shall
not be extended. Delivery of possession shall be deemed to occur on the earlier
of the date Landlord receives a Certificate of Occupancy or upon substantial
completion of the Premises (as certified by Landlord's architect). If Landlord
permits Tenant to enter into possession of the Premises before the Commencement
Date, such possession shall be subject to the provisions of this Lease,
including, without limitation, the payment of Rent (unless otherwise agreed in
writing).

Within ten (10) days of delivery of possession Landlord shall deliver to Tenant
and Tenant shall execute an Acceptance of Premises in which Tenant shall
certify, among other things, that (a) Landlord has satisfactorily completed
Landlord's Work to the Premises pursuant to Exhibit "D", unless written
exception is set forth thereon, and (b) that Tenant accepts the Premises.
Tenant's failure to execute and deliver the Acceptance of Premises shall be
conclusive evidence, as against Tenant, that Landlord has satisfactorily
completed Landlord's Work to the Premises pursuant to Exhibit "D".

In the event Tenant fails to take possession of the Premises following execution
of this Lease, Tenant shall reimburse Landlord promptly upon demand for all
costs incurred by Landlord in connection with entering into this Lease
including, but not limited to, broker fees and commissions, sums paid for the
preparation of a floor and/or space plan for the Premises, costs incurred in
performing Landlord's Work pursuant to Exhibit "D", loss of rental income,
attorneys' fees and costs, and any other damages for breach of this Lease
established by Landlord.

5.    INTENDED USE OF THE PREMISES.

The statement in this Lease of the nature of the business to be conducted by
Tenant in the Premises does not constitute a representation or guaranty by
Landlord as to the present or future suitability of the Premises for the conduct
of such business in the Premises, or that it is lawful or permissible under the
certificate of occupancy issued for the Building, or is otherwise permitted by
law. Tenant's taking possession of the Premises shall be conclusive evidence, as
against Tenant, that, at the time such possession was taken, the Premises were
satisfactory for Tenant's intended use.

6.    RENT.

      6.1. Payment of Rent. Tenant shall pay Rent for the Premises. Monthly
Installments of Rent shall be payable in advance on the first day of each
calendar month of the Term. If the Term begins (or ends) on other than the first
(or last) day of a calendar month, Rent for the partial month shall be prorated
based on the number of days in that month. Rent shall be paid to Landlord at the
Rent Payment Address set forth in Section 2.8., or to such other person at such
place as Landlord may from time to time designate in writing, without any prior
demand therefor and without deduction or offset, in lawful money of the United
States of America. Tenant shall pay Landlord the first Monthly Installment of
Base Rent upon execution of this Lease.

                                       3
<PAGE>

      6.3. Additional Rent for Increases in Tax Costs and Operating Expenses.
If, in any calendar year during the Term of this Lease, Landlord's Tax Costs and
Operating Expenses (as hereinafter defined) for the Project (hereinafter
sometimes together referred to as Direct Costs) shall be higher than in the Base
Year specified in Section 2.3., Additional Rent for such Direct Costs payable
hereunder shall be increased by an amount equal to Tenant's Proportionate Share
of the difference between Landlord's actual Direct Costs for such calendar year
and the actual Direct Costs of the Base Year. However, if during any calendar
year of the Term the occupancy of the Project is less than ninety-five percent
(95%), then Landlord shall make an appropriate adjustment of the variable
components of Operating Expenses, as reasonably determined by Landlord, to
determine the amount of Operating Expenses that would have been incurred had the
Project been ninety-five percent (95%) occupied during that calendar year. This
estimated amount shall be deemed the amount of Operating Expenses for that
calendar year. For purposes hereof, "variable components" shall include only
those Operating Expenses that are affected by variations in occupancy levels.

            6.3.1. Definitions. As used in this Section 6.3., the following
      terms shall have the following meanings:

                  6.3.1.1. Tax Costs shall mean any and all real estate taxes,
            other similar charges on real property or improvements, assessments,
            and all other charges (but in no event Landlord's income or estate
            taxes) assessed, levied, imposed or becoming a lien upon part or all
            of the Project or the appurtenances thereto, or attributable
            thereto, or on the rents, issues, profits or income received or
            derived therefrom which may be imposed, levied, assessed or charged
            by the United States or the state, county or city in which the
            Project is located, or any other local government authority or
            agency or political subdivision thereof. Tax Costs for each tax year
            shall be apportioned to determine the Tax Costs for the subject
            calendar years.

                        Landlord, at Landlord's reasonable discretion, may
            contest any taxes levied or assessed against the Building or Project
            during the Term. If Landlord contests any taxes levied or assessed
            during the Term, Tenant shall pay Landlord Tenant's Proportionate
            Share of all reasonable costs incurred by Landlord in connection
            with the contest.

                  6.3.1.2. Operating Expenses shall mean any and all expenses
            incurred by Landlord in connection with the management, maintenance,
            operation, and repair of the Project, the equipment, adjacent walks,
            Common Area, parking areas, the roof, landscaped areas, including,
            but not limited to, salaries, wages, benefits, pension payments,
            payroll taxes, worker's compensation, and other costs related to
            employees engaged in the management, operation, maintenance and/or
            repair of the Project; any and all assessments or costs incurred
            with respect to Covenants, Conditions and/or Restrictions,
            Reciprocal Easement Agreements or similar documents affecting the
            Building or Project, if any; the cost of all charges to Landlord for
            electricity, natural gas, air conditioning, steam, water, and sewer,
            and other utilities furnished to the Project including any taxes
            thereon; reasonable attorneys' fees and/or consultant fees incurred
            by Landlord in contracting with a company or companies to provide
            electricity (or any other utility) to the Project, any fees for the
            installation, maintenance, repair or removal of related equipment,
            and any exit fees or stranded cost charges mandated by the State;
            the cost and expense for third-party consultants, accountants and
            attorneys; a management fee; energy studies and the amortized cost
            of any energy or other cost saving equipment used by Landlord to
            provide services pursuant to the terms of the Lease (including the
            amortized cost to upgrade the efficiency or capacity of Building
            telecommunication lines and systems if responsibility therefor is
            assumed by Landlord as discussed in Section 35. hereof); the cost of
            license fees related to the Project; the cost of all charges for
            property (all risk), liability, rent loss and all other insurance
            for the Project to the extent that such insurance is required to be
            carried by Landlord under any lease, mortgage or deed of trust
            covering the whole or a substantial part of the Project or the
            Building, or, if not required under any such lease, mortgage or deed
            of trust, then to the extent such insurance is carried by owners of
            properties comparable to the Project; the cost of all building and
            cleaning supplies and materials; the cost of all charges for
            security services, cleaning, maintenance and service contracts and
            other services with independent contractors, including but not
            limited to the maintenance, operation and repair of all electrical,
            plumbing and mechanical systems of the Project and maintenance,
            repair and replacement of any intrabuilding cabling

                                       4
<PAGE>

            network (ICN), if any; and the cost of any janitorial, utility or
            other services to be provided by Landlord.

                  Notwithstanding the foregoing, the following shall not be
            included within Operating Expenses: (i) costs of capital
            improvements (except any improvements that might be deemed "capital
            improvements" related to the enhancement or upgrade of the ICN and
            related equipment) and costs of curing design or construction
            defects; (ii) depreciation; (iii) interest and principal payments on
            mortgages and other debt costs and ground lease payments, if any,
            and any penalties assessed as a result of Landlord's late payments
            of such amounts; (iv) real estate broker leasing commissions or
            compensation; (v) any cost or expenditure (or portion thereof) for
            which Landlord is reimbursed, whether by insurance proceeds or
            otherwise; (vi) attorneys' fees, costs, disbursements, advertising
            and marketing and other expenses incurred in connection with the
            negotiation of leases with prospective tenants of the Building;
            (vii) rent for space which is not actually used by Landlord in
            connection with the management and operation of the Building; (viii)
            all costs or expenses (including fines, penalties and legal fees)
            incurred due to the violation by Landlord, its employees, agents,
            contractors or assigns of the terms and conditions of the Lease, or
            any valid, applicable building code, governmental rule, regulation
            or law; (ix) except for the referenced management compensation, any
            overhead or profit increments to any subsidiary or affiliate of
            Landlord for services on or to the Building, to the extent that the
            costs of such services exceed competitive costs for such services;
            (x) the cost of constructing tenant improvements for Tenant or any
            other tenant of the Building or Project; (xi) Operating Expenses
            specially charged to and paid by any other tenant of the Building or
            Project; and (xii) the cost of special services, goods or materials
            provided to any other tenant of the Building or Project.

            6.3.2. Determination and Payment of Tax Costs and Operating
            Expenses.

                  6.3.2.1. On or before the last day of each December during the
            Term of this Lease, Landlord shall furnish to Tenant a written
            statement showing in reasonable detail Landlord's projected Direct
            Costs for the succeeding calendar year. If such statement of
            projected Direct Costs indicates the Direct Costs will be higher
            than in the Base Year, then the Rent due from Tenant hereunder for
            the next succeeding year shall be increased by an amount equal to
            Tenant's Proportionate Share of the difference between the projected
            Direct Costs for the calendar year and the Base Year. If during the
            course of the calendar year Landlord determines that actual Direct
            Costs will vary from its estimate by more than five percent (5%),
            Landlord may deliver to Tenant a written statement showing
            Landlord's revised estimate of Direct Costs. On the next payment
            date for Monthly Installments of Rent following Tenant's receipt of
            either such statement, Tenant shall pay to Landlord an additional
            amount equal to such monthly Rent increase adjustment or a reduced
            amount if Landlord estimates of direct costs is lower (as set forth
            on Landlord's statement). Thereafter, the monthly Rent adjustment
            payments becoming due shall be in the amount set forth in such
            projected Rent adjustment statement from Landlord. Neither
            Landlord's failure to deliver nor late delivery of such statement
            shall constitute a default by Landlord or a waiver of Landlord's
            right to any Rent adjustment provided for herein.

                  6.3.2.2. On or before the first day of each April during the
            Term of this Lease, Landlord shall furnish to Tenant a written
            statement of reconciliation (the Reconciliation) showing in
            reasonable detail Landlord's actual Direct Costs for the prior year,
            together with a full statement of any adjustments necessary to
            reconcile any sums paid as estimated Rent adjustments during the
            prior year with those sums actually payable for such prior year. In
            the event such Reconciliation shows that additional sums are due
            from Tenant, Tenant shall pay such sums to Landlord within ten (10)
            days of receipt of such Reconciliation. In the event such
            Reconciliation shows that a credit is due Tenant, such credit shall
            be credited against the sums next becoming due from Tenant, unless
            this Lease has expired or been terminated pursuant to the terms
            hereof (and all sums due Landlord have been paid), in which event
            such sums shall be refunded to Tenant. Neither Landlord's failure to
            deliver nor late delivery of such Reconciliation to Tenant by April
            first shall constitute a default by Landlord or operate as a waiver
            of Landlord's right to collect all Rent due hereunder.

                  6.3.2.3. So long as Tenant is not in default under the terms
            of the Lease and provided Notice of Tenant's request is given to
            Landlord within thirty (30) days after Tenant's receipt of the
            Reconciliation, Tenant may inspect Landlord's Reconciliation
            accounting records relating to Direct Costs at Landlord's corporate
            office, during normal business hours, for the purpose of verifying
            the charges contained in such statement. The audit must be completed
            within sixty (60) days of Landlord's receipt of Tenant's Notice,
            unless such period is extended by Landlord (in Landlord's reasonable
            discretion). Before conducting any audit however, Tenant must pay in
            full the amount of Direct Costs billed.

                                       5
<PAGE>

            Tenant may only review those records that specifically relate to
            Direct Costs. Tenant may not review any other leases or Landlord's
            tax returns or financial statements. In conducting an audit, Tenant
            must utilize an independent certified public accountant experienced
            in auditing records related to property operations. The proposed
            accountant is subject to Landlord's reasonable prior approval. The
            audit shall be conducted in accordance with generally accepted rules
            of auditing practices. Tenant may not conduct an audit more often
            than once each calendar year. Tenant may audit records relating to a
            calendar year only one time. No audit shall cover a period of time
            other than the calendar year from which Landlord's Reconciliation
            was generated. Upon receipt thereof, Tenant shall deliver to
            Landlord a copy of the audit report and all accompanying data.
            Tenant and Tenant's auditor shall keep confidential any agreements
            involving the rights provided in this section and the results of any
            audit conducted hereunder. As a condition precedent to Tenant's
            right to conduct an audit, Tenant's auditor shall sign a
            confidentiality agreement in a form reasonably acceptable to
            Landlord. However, Tenant shall be permitted to furnish information
            to its attorneys, accountants and auditors to the extent necessary
            to perform their respective services for Tenant. Notwithstanding
            anything herein to the contrary, if the results of Tenant's audit
            show that Tenant was overcharged, then, there shall be a credit for
            such amounts against the next installments of Operating Expenses due
            from Tenant. Also, if the overcharge is greater than 5% of total
            Operating Expenses then, Landlord shall pay Tenant reasonable costs
            of such audit, excluding travel expenses.

      6.4. Definition of Rent. All costs and expenses which Tenant assumes or
agrees or is obligated to pay to Landlord under this Lease shall be deemed
Additional Rent (which, together with the Base Rent is sometimes referred to as
Rent).

      6.5. Taxes on Tenant's Use and Occupancy. In addition to Rent and other
charges to be paid by Tenant hereunder, Tenant shall pay Landlord upon demand
any and all taxes payable by Landlord (other than net income taxes) which are
not otherwise reimbursable under this Lease, whether or not now customary or
within the contemplation of the parties, where such taxes are upon, measured by
or reasonably attributable to (a) the cost or value of Tenant's equipment,
furniture, fixtures and other personal property located in the Premises, or the
cost or value of any leasehold improvements made in or to the Premises by or for
Tenant, other than Building Standard Tenant Improvements made by Landlord,
regardless of whether title to such improvements is held by Tenant or Landlord;
(b) the gross or net Rent payable under this Lease, including, without
limitation, any rental or gross receipts tax levied by any taxing authority with
respect to the receipt of Rent hereunder; (c) the possession, leasing,
operation, management, maintenance, alteration, repair, use or occupancy by
Tenant of the Premises or any portion thereof; or (d) this transaction or any
document to which Tenant is a party creating or transferring an interest or an
estate in the Premises. If it becomes unlawful for Tenant to reimburse Landlord
for any costs as required under this Lease, Base Rent shall be revised to net
Landlord the same net Rent after imposition of any tax or other charge upon
Landlord as would have been payable to Landlord but for the reimbursement being
unlawful.

7.    LATE CHARGES.

If Tenant fails to pay when due any Rent or other amounts or charges which
Tenant is obligated to pay under the terms of this Lease, then Tenant shall pay
Landlord a late charge equal to ten percent (10%) of each such installment if
any such installment is not received by Landlord within five (5) days from the
date it is due. Tenant acknowledges that the late payment of any Rent will cause
Landlord to lose the use of that money and incur costs and expenses not
contemplated under this Lease including, without limitation, administrative
costs and processing and accounting expenses, the exact amount of which is
extremely difficult to ascertain. Landlord and Tenant agree that this late
charge represents a reasonable estimate of such costs and expenses and is fair
compensation to Landlord for the loss suffered from such nonpayment by Tenant.
However, the late charge is not intended to cover Landlord's attorneys' fees and
costs relating to delinquent Rent. Acceptance of any late charge shall not
constitute a waiver of Tenant's default with respect to such nonpayment by
Tenant nor prevent Landlord from exercising any other rights or remedies
available to Landlord under this Lease. Late charges are deemed Additional Rent.

In no event shall this provision for the imposition of a late charge be deemed
to grant to Tenant a grace period or an extension of time within which to pay
any Rent due hereunder or prevent Landlord from exercising any right or remedy
available to Landlord upon Tenant's failure to pay such Rent when due.

8.    SECURITY DEPOSIT.

Upon execution of this Lease, Tenant agrees to deposit with Landlord a Security
Deposit in the amount set forth in Section 2.16. as security for Tenant's
performance of its obligations under this Lease. Landlord and Tenant agree that
the Security Deposit may be commingled with funds of Landlord and Landlord shall
have no obligation or liability for payment of interest on such deposit. Tenant
shall not mortgage, assign, transfer or encumber the Security Deposit without
the prior written consent of Landlord and any attempt by Tenant to do so shall
be void, without force or effect and shall not be binding upon Landlord.

Notwithstanding anything herein to the contrary, in the event that Tenant has
not been in default under the Lease at such time, Landlord will refund one-third
1/3 of Tenant's Security Deposit ($55,386.67) after the twelth (12th) full month
of the Lease Term. Further, if Tenant has still not been in default at such
time, then Landlord will refund another one-third (1/3) of Tenant's Security
Deposit ($55,386.67) after the twenty fourth (24th) month of the Lease Term.

                                       6
<PAGE>

If Tenant fails to timely pay any Rent or other amount due under this Lease,
or fails to perform any of the terms hereof after the expiration of notice
and grace period per paragraph 19, Landlord may, at its option and without
prejudice to any other remedy which Landlord may have, appropriate and apply
or use all or any portion of the Security Deposit for Rent payments or any
other amount then due and unpaid, for payment of any amount for which
Landlord has become obligated as a result of Tenant's default or breach, and
for any loss or damage sustained by Landlord as a result of Tenant's default
or breach. If Landlord so uses any of the Security Deposit, Tenant shall,
within ten (10) days after written demand therefor, restore the Security
Deposit to the full amount originally deposited. Tenant's failure to do so
shall constitute an act of default hereunder and Landlord shall have the
right to exercise any remedy provided for in Section 19. hereof.

If Tenant defaults under this Lease more than two (2) times during any calendar
year, irrespective of whether such default is cured, then, without limiting
Landlord's other rights and remedies, Landlord may, in Landlord's sole
discretion, modify the amount of the required Security Deposit. Within ten (10)
days after Notice of such modification, Tenant shall submit to Landlord the
required additional sums. Tenant's failure to do so shall constitute an act of
default, and Landlord shall have the right to exercise any remedy provided for
in Section 19. hereof. Notwithstanding the foregoing, Tenant's secutirity
deposit may be increased by a maximum of two (2) months additional rent.

If Tenant complies with all of the terms and conditions of this Lease, and
Tenant is not in default on any of its obligations hereunder, then within the
time period statutorily prescribed after Tenant vacates the Premises, Landlord
shall promptly return to Tenant (or, at Landlord's option, to the last subtenant
or assignee of Tenant's interest hereunder) the Security Deposit less any
expenditures made by Landlord to repair damages to the Premises caused by Tenant
and to clean the Premises upon expiration or earlier termination of this Lease.

In the event of bankruptcy or other debtor-creditor proceedings against Tenant,
such Security Deposit shall be deemed to be applied first to the payment of Rent
and other sums due Landlord for all periods prior to the filing of such
proceedings.

9.    TENANT'S USE OF THE PREMISES.

The provisions of this Section are for the benefit of the Landlord and are not
nor shall they be construed to be for the benefit of any tenant of the Building
or Project.

      9.1. Use. Tenant shall use the Premises solely for the purposes set forth
in Section 2.20. No change in the Use of the Premises shall be permitted, except
as provided in this Section 9.

            9.1.1. If, at any time during the Term hereof, Tenant desires to
      change the Use of the Premises, including any change in Use associated
      with a proposed assignment or sublet of the Premises, Tenant shall provide
      Notice to Landlord of its request for approval of such proposed change in
      Use. Tenant shall promptly supply Landlord with such information
      concerning the proposed change in Use as Landlord may reasonably request.
      Landlord shall have the right to approve such proposed change in Use,
      which approval shall not be unreasonably withheld. Landlord's consent to
      any change in Use shall not be construed as a consent to any subsequent
      change in Use.

      9.2. Observance of Law. Tenant shall not use or occupy the Premises or
permit anything to be done in or about the Premises in violation of any
declarations, covenant, condition or restriction, or law, statute, ordinance or
governmental rules, regulations or requirements now in force or which may
hereafter be enacted or promulgated. Tenant shall, at its sole cost and expense,
upon Notice from Landlord, immediately discontinue any use of the Premises which
is declared by any governmental authority having jurisdiction to be a violation
of law or of the Certificate of Occupancy. Tenant shall promptly comply, at its
sole cost and expense, with all laws, statutes, ordinances and governmental
rules, regulations or requirements now in force or which may hereafter be
imposed which shall by reason of Tenant's Use or occupancy of the Premises,
impose any duty upon Tenant or Landlord with respect to Tenant's Use or
occupation. Further, Tenant shall, at Tenant's sole cost and expense, bring the
Premises into compliance with all such laws, including the Americans With
Disabilities Act of 1990, as amended (ADA), whether or not the necessity for
compliance is triggered by Tenant's Use, and Tenant shall make, at its sole cost
and expense, any changes to the Premises required to accommodate Tenant's
employees with disabilities (any work performed pursuant to this Section shall
be subject to the terms of Section 12. hereof). The judgment of any court of
competent jurisdiction or the admission by Tenant in any action or proceeding
against Tenant, whether Landlord is a party thereto or not, that Tenant has
violated any such law, statute, ordinance, or governmental regulation, rule or
requirement in the use or occupancy of the Premises, Building or Project shall
be conclusive of that fact as between Landlord and Tenant. Notwithstanding the
foregoing, Tenant shall not be responsible for bringing into complance existing
doors with the Tenant's premises.

      9.3. Insurance. Tenant shall not do or permit to be done anything which
will contravene, invalidate or increase the cost of any insurance policy
covering the Building or Project and/or property located therein, and shall
comply with all rules, orders, regulations, requirements and recommendations of
Landlord's Insurance carrier(s) or any board of fire insurance underwriters or
other similar body now or hereafter constituted, relating to or affecting the
condition, use or occupancy of the Premises, excluding structural changes not

                                       7
<PAGE>

related to or affected by Tenant's improvements or acts. Tenant shall promptly
upon demand reimburse Landlord for any additional premium charged for violation
of this Section.

      9.4. Nuisance and Waste. Tenant shall not do or permit anything to be done
in or about the Premises which will in any way obstruct or interfere with the
rights of other tenants or occupants of the Building or Project, or injure them,
or use or allow the Premises to be used for any improper, unlawful or
objectionable purpose. Tenant shall not cause, maintain or permit any nuisance
in, on or about the Premises. Tenant shall not commit or suffer to be committed
any waste in or upon the Premises.

      9.5. Load and Equipment Limits. Tenant shall not place a load upon any
floor of the Premises which exceeds the load per square foot which such floor
was designed to carry as determined by Landlord or Landlord's structural
engineer. The cost of any such determination made by Landlord's structural
engineer in connection with Tenant's occupancy shall be paid by Tenant upon
Landlord's demand. Tenant shall not install business machines or mechanical
equipment which will in any manner cause noise objectionable to other tenants or
injure, vibrate or shake the Premises or Building.

      9.6. Hazardous Material. Tenant shall not create, generate, use, bring,
allow, emit, dispose, or permit on the Premises, Building or Project any toxic
or hazardous gaseous, liquid, or solid material or waste, or any other hazardous
material defined or listed in any applicable federal, state or local law, rule,
regulation or ordinance except for de minimis amounts of hazardous materials
contained in ordinary office products or use an ordinary course of tenant's
business provided that such usage shall be in compliance with all laws, and
shall be subject to Tenant's indemnity obligations hereunder. Tenant shall
comply with all applicable laws with respect to such hazardous material,
including all laws affecting the use, storage and disposal thereof. If the
presence of any hazardous material brought to the Premises, Building or Project
by Tenant or Tenant's employees, agent or contractors results in contamination,
Tenant shall promptly take all actions necessary, at Tenant's sole cost and
expense, to remediate the contamination and restore the Premises, Building or
Project to the condition that existed before introduction of such hazardous
material. Tenant shall first obtain Landlord's approval of the proposed remedial
action and shall keep Landlord informed during the process of remediation.

Tenant shall indemnify, defend and hold Landlord harmless from any claims,
liabilities, costs or expenses incurred or suffered by Landlord arising from
such bringing, allowing, using, permitting, generating, creating, emitting, or
disposing of toxic or hazardous material whether or not consent to same has been
granted by Landlord. Tenant's duty to defend, hold-harmless and indemnify
Landlord hereunder shall survive the expiration or termination of this Lease.
The consent requirement contained herein shall not apply to ordinary office
products that may contain de minimis quantities of hazardous material; however,
Tenant's indemnification obligations are not diminished with respect to the
presence of such products. Tenant acknowledges that Tenant has an affirmative
duty to immediately notify Landlord of any release or suspected release of
hazardous material in the Premises or on or about the Project.

Medical waste and any other waste, the removal of which is regulated, shall be
contracted for and disposed of by Tenant, at Tenant's expense, in accordance
with all applicable laws and regulations. No material shall be placed in Project
trash boxes, receptacles or Common Areas if the material is of such a nature
that it cannot be disposed of in the ordinary and customary manner of removing
and disposing of trash and garbage in the State without being in violation of
any law or ordinance.

10.   SERVICES AND UTILITIES.

Landlord agrees to furnish services and utilities to the Premises during
normal business hours on generally recognized business days subject to the
Rules and Regulations of the Building or Project. Services and utilities
shall include reasonable quantities of heating, ventilation and air
conditioning (HVAC) as required in Landlord's reasonable judgment for the
comfortable use and occupancy of the Premises; lighting replacement for
building standard lights; window washing and janitor services in a manner
that such services are customarily furnished to comparable office buildings
in the area. Landlord shall supply common area water for drinking, cleaning
and restroom purposes only. Tenant, at Tenant's sole cost and expense, shall
supply all paper and other products used within the Premises. During normal
business hours on generally recognized business days, Landlord shall also
maintain and keep lighted the common stairs, common entries and restrooms in
the Building and shall furnish elevator service and restroom supplies.
Further, Landlord shall also be responsible for snow and ice removal. If
Tenant desires HVAC or other services at any other time, Landlord shall use
reasonable efforts to furnish such service upon reasonable notice from
Tenant, and Tenant shall pay Landlord's charges therefor on demand. Landlord
may provide telecommunications lines and systems as discussed in Section 35.
hereof. Notwithstanding the foregoing, the Premises will be seperately
metered for lighting, plugs and HVAC. Further, Landlord shall also be
responsible for snow and ice removal.

Notwithstanding the foregoing, Tenant shall obtain from Landlord at Tenant's
sole cost and expense all electric utilities used at the Premises.

If permitted by law, Landlord shall have the right, in Landlord's reasonable
discretion, at any time and from time to time during the Term, to contract for
the provision of electricity (or any other utility) with, and to switch from,
any company providing such utility. Tenant shall cooperate with Landlord and any
such utility provider at all times, and, as reasonably

                                       8
<PAGE>

necessary, Tenant shall allow such parties access to the electric (or other
utility) lines, feeders, risers, wiring and other machinery located within the
Premises.

Landlord shall not be in default hereunder or be liable for any damages directly
or indirectly resulting from, nor shall Rent be abated by reason of (a) the
installation, use or interruption of use of any equipment in connection with the
furnishing of any of the foregoing services, or (b) failure to furnish or delay
in furnishing any such services where such failure or delay is caused by
accident or any condition or event beyond the reasonable control of Landlord, or
by the making of necessary repairs or improvements to the Premises, Building or
Project, or (c) any change, failure, interruption, disruption or defect in the
quantity or character of the electricity (or other utility) supplied to the
Premises or Project, or (d) the limitation, curtailment or rationing of, or
restrictions on, use of water, electricity, gas or any other form of energy
serving the Premises, Building or Project. Landlord shall not be liable under
any circumstances for a loss of or injury to property or business, however
occurring, through, in connection with or incidental to the failure to furnish
any such services. Notwithstanding the foregoing, Landlord shall use reasonable
efforts to remedy the cause of interruption of services set forth herein.

Tenant shall not, without the prior written consent of Landlord, use any
apparatus or device in the Premises, including, without limitation, electronic
data processing machines, punch card machines, word processing equipment,
personal computers, or machines using in excess of 120 volts, which consumes
more electricity than is usually furnished or supplied for the use of desk top
office equipment and photocopy equipment ordinarily in use in premises
designated as general office space, as determined by Landlord. Tenant shall not
connect any apparatus to electric current except through existing electrical
outlets in the Premises.

Tenant shall not consume electric current in excess of that usually furnished or
supplied for the use of premises as office space (as determined by Landlord),
without first procuring the written consent of Landlord, which Landlord may
refuse. In the event of consent, electrical current shall be separately metered
in Tenant's name and paid for by Tenant. The cost or any such meter and its
installation, maintenance and repair shall be paid by Tenant.

Notwithstanding anything contained herein to the contrary, if Tenant is granted
the right to purchase electricity from a provider other than the company or
companies used by Landlord, Tenant shall indemnify, defend, and hold harmless
Landlord from and against all losses, claims, demands, expenses and judgments
caused by, or directly or indirectly arising from, the acts or omissions of
Tenant's electricity provider (including, but not limited to, expenses and/or
fines incurred by Landlord in the event Tenant's electricity provider fails to
provide sufficient power to the Premises, as well as damages resulting from the
improper or faulty installation or construction of facilities or equipment in or
on the Premises by Tenant or Tenant's electricity provider.

Nothing contained in this Section shall restrict Landlord's right to require at
any time separate metering of utilities furnished to the Premises. If the
separate metering of utilities furnished to the Premises is due to Tenant's
excessive use of electric current, then the cost of any such meter and its
installation, maintenance and repair shall be paid by Tenant. If Landlord
requires separate metering for reasons other than Tenant's excessive consumption
of electric current, then the cost of any such meter and its installation,
maintenance and repair shall be paid by Landlord. In either event, accounts for
all such separately metered utilities shall be in Tenant's name and paid for by
Tenant. Notwithstanding the foregoing, the premise are currently seperately
metered.

If Tenant uses heat generating machines or equipment in the Premises which
effect the temperature otherwise maintained by the HVAC system, Landlord
reserves the right to install supplementary air conditioning units in the
Premises and the cost thereof, including the cost of installation, operation and
maintenance thereof, shall be paid by Tenant to Landlord upon demand therefor.

11.   REPAIRS AND MAINTENANCE.

      11.1. Landlord's Obligations. Landlord shall make, at Landlord's sole
expense, all structural repairs except as specified herein and shall maintain in
good order, condition and repair the Building and all other portions of the
Premises not the obligation of Tenant or of any other tenant in the Building. If
applicable, Landlord shall also maintain in good order, condition and repair the
ICN, the cost of which is reimbursable pursuant to Section 6.3.1.2. unless
responsibility therefor is assigned to a particular tenant.

      11.2. Tenant's Obligations.

            11.2.1. Tenant shall, at Tenant's sole expense and except for
      services furnished by Landlord pursuant to Section 10. hereof, maintain
      the Premises in good order, condition and repair. For the purposes of this
      Section 11.2.1., the term Premises shall be deemed to include all items
      and equipment installed by or for the benefit of or at the expense of
      Tenant, including without limitation the interior surfaces of the
      ceilings, walls and floors; all doors; all interior windows; dedicated
      heating, ventilating and air conditioning equipment; all plumbing, pipes
      and fixtures; electrical switches and fixtures; internal wiring as it
      connects to the ICN (if applicable); and Building Standard Tenant
      Improvements. Notwithstanding the foregoing, Landlord represents that all
      HVAC systems shall be in good working order as of the Lease Commencement
      Date.

                                       9
<PAGE>

            11.2.2. Tenant shall be responsible for all repairs and alterations
      in and to the Premises, Building and Project and the facilities and
      systems thereof to the satisfaction of Landlord, the need for which arises
      out of (a) Tenant's use or occupancy of the Premises, (b) the
      installation, removal, use or operation of Tenant's Property (as defined
      in Section 13.) in the Premises, (c) the moving of Tenant's Property into
      or out of the Building, or (d) the act, omission, misuse or negligence of
      Tenant, its agents, contractors, employees or invitees.

            11.2.3. If Tenant fails to maintain the Premises in good order,
      condition and repair, Landlord shall give Notice to Tenant to do such acts
      as are reasonably required to so maintain the Premises. If Tenant fails to
      promptly commence such work and diligently prosecute it to completion,
      then Landlord shall have the right to do such acts and expend such funds
      at the expense of Tenant as are reasonably required to perform such work.

      11.3. Compliance with Law. Landlord and Tenant shall each do all acts
necessary to comply with all applicable laws, statutes, ordinances, and rules of
any public authority relating to their respective maintenance obligations as set
forth herein. The provisions of Section 9.2. are deemed restated here.

      11.4. Notice of Defect. If it is Landlord's obligation to repair, Tenant
shall give Landlord prompt Notice, regardless of the nature or cause, of any
damage to or defective condition in any part or appurtenance of the Building's
mechanical, electrical, plumbing, HVAC or other systems serving, located in, or
passing through the Premises.

      11.5. Landlord's Liability. Except as otherwise expressly provided in this
Lease, Landlord shall have no liability to Tenant nor shall Tenant's obligations
under this Lease be reduced or abated in any manner by reason of any
inconvenience, annoyance, interruption or injury to business arising from
Landlord's making any repairs or changes which Landlord is required or permitted
by this Lease or by any other tenant's lease or required by law to make in or to
any portion of the Project, Building or Premises. Landlord shall nevertheless
use reasonable efforts to minimize any interference with Tenant's conduct of its
business in the Premises.

12.   CONSTRUCTION, ALTERATIONS AND ADDITIONS.

      12.1. Landlord's Construction Obligations. Landlord shall perform
Landlord's Work to the Premises as described in Exhibit "D".

      12.2. Tenant's Construction Obligations. Tenant shall perform Tenant's
Work to the Premises as described in Exhibit "D" and shall comply with all of
the provisions of this Section 12.

      12.3. Tenant's Alterations and Additions. Except as provided in Section
12.2. above, and except for alterations which cost is less than $10,000 and
which do not effect the HVAC, electrical, plumbing, structural or mechanical
systems, Tenant shall not make any other additions, alterations or improvements
to the Premises without obtaining the prior written consent of Landlord.
Landlord's consent may be conditioned, without limitation, on Tenant removing
any such additions, alterations or improvements upon the expiration of the Term
and restoring the Premises to the same condition as on the date Tenant took
possession. All work with respect to Tenant's Work described in Exhibit "D", as
well as any addition, alteration or improvement, shall comply with all
applicable laws, ordinances, codes and rules of any public authority (including,
but not limited to the ADA) and shall be done in a good and professional manner
by properly qualified and licensed personnel approved by Landlord. All work
shall be diligently prosecuted to completion. Upon completion, Tenant shall
furnish Landlord "as-built" plans. Prior to commencing any such work, Tenant
shall furnish Landlord with plans and specifications; names and addresses of
contractors; copies of all contracts; copies of all necessary permits; evidence
of contractor's and subcontractor's insurance coverage for Builder's Risk at
least as broad as Insurance Services Office (ISO) special causes of loss form CP
10 30, Commercial General Liability at least as broad as ISO CG 00 01, workers'
compensation, employer's liability and auto liability, all in amounts reasonably
satisfactory to Landlord; and indemnification in a form reasonably satisfactory
to Landlord. The work shall be performed in a manner that will not interfere
with the quiet enjoyment of the other tenants in the Building in which the
Premises is located.

Landlord may require, in Landlord's sole discretion and at Tenant's sole cost
and expense, that Tenant provide Landlord with a lien and completion bond in an
amount equal to at least one and one-half (1-1/2) times the total estimated cost
of any additions, alterations or improvements to be made in or to the Premises
if alterations will exceed $10,000. Nothing contained in this Section 12.3.
shall relieve Tenant of its obligation under Section 12.4. to keep the Premises,
Building and Project free of all liens.

                                       10
<PAGE>

      12.4. Payment. Subject to the Tenant Improvement Allowance set forth in
Section 37 hereof. Tenant shall pay the costs of any work done on the Premises
pursuant to Sections 12.2. and 12.3., and shall keep the Premises, Building and
Project free and clear of liens of any kind. Tenant hereby indemnifies, and
agrees to defend against and keep Landlord free and harmless from all liability,
loss, damage, costs, attorneys' fees and any other expense incurred on account
of claims by any person performing work or furnishing materials or supplies for
Tenant or any person claiming under Tenant.

Tenant shall give Notice to Landlord at least ten (10) business days prior to
the expected date of commencement of any work relating to alterations, additions
or improvements to the Premises. Landlord retains the right to enter the
Premises and post such notices as Landlord deems proper at any reasonable time.

      12.5. Property of Landlord. Except as otherwise set forth herein, all
additions, alterations and improvements made to the Premises shall become the
property of Landlord and shall be surrendered with the Premises upon the
expiration of the Term unless their removal is required by Landlord as provided
in Section 12.3.; provided, however, Tenant's equipment, machinery and trade
fixtures shall remain the Property of Tenant and shall be removed, subject to
the provisions of Section 13.2.

13.   LEASEHOLD IMPROVEMENTS; TENANT'S PROPERTY.

      13.l. Leasehold Improvements. All fixtures, equipment (including
air-conditioning or heating systems), improvements and appurtenances attached to
or built into the Premises and/or Building at the commencement or during the
Term of the Lease (Leasehold Improvements), whether or not by or at the expense
of Tenant, shall be and remain a part of the Premises, shall be the property of
Landlord and shall not be removed by Tenant, except as expressly provided in
Section 13.2., unless Landlord, by Notice to Tenant not later than thirty (30)
days prior to the expiration of the Term, elects to have Tenant remove any
Leasehold Improvements installed by Tenant. In such case, Tenant, at Tenant's
sole cost and expense and prior to the expiration of the Term, shall remove the
Leasehold Improvements and repair any damage caused by such removal.

      13.2. Tenant's Property. All signs, notices, displays, movable partitions,
business and trade fixtures, machinery and equipment (excluding air-conditioning
or heating systems, whether installed by Tenant or not), Tenant's personal
telecommunications equipment and office equipment located in the Premises and
acquired by or for the account of Tenant, without expense to Landlord, which can
be removed without structural damage to the Building, and all furniture,
furnishings and other articles of movable personal property owned by Tenant and
located in the Premises (collectively, Tenant's Property) shall be and shall
remain the property of Tenant and may be removed by Tenant at any time during
the Term; provided that if any of Tenant's Property is removed, Tenant shall
promptly repair any damage to the Premises or to the Building resulting from
such removal, including without limitation repairing the flooring and patching
and painting the walls where required by Landlord to Landlord's reasonable
satisfaction, all at Tenant's sole cost and expense.

14.   INDEMNIFICATION.

      14.1. Tenant Indemnification. Tenant shall indemnify and hold Landlord
harmless from and against any and all liability and claims of any kind for loss
or damage to any person or property arising out of: (a) Tenant's use and
occupancy of the Premises, or the Building or Project, or any work, activity or
thing done, allowed or suffered by Tenant in, on or about the Premises, the
Building or the Project; (b) any breach or default by Tenant of any of Tenant's
obligations under this Lease; or (c) any negligent or otherwise tortious act or
omission of Tenant, its agents, employees, subtenants, licensees, customers,
guests, invitees or contractors (including agents or contractors who perform
services or work outside of the Premises for Tenant). At Landlord's request,
Tenant shall, at Tenant's expense, and by counsel satisfactory to Landlord,
defend Landlord in any action or proceeding arising from any such claim. Tenant
shall indemnify Landlord against all costs, attorneys' fees, expert witness fees
and any other expenses or liabilities incurred in such action or proceeding. As
a material part of the consideration for Landlord's execution of this Lease,
Tenant hereby assumes all risk of damage or injury to any person or property in,
on or about the Premises from any cause and Tenant hereby waives all claims in
respect thereof against Landlord, except in connection with damage or injury
resulting solely from the gross negligence or willful misconduct of Landlord or
its authorized agents.

      14.2. Landlord Not Liable. Landlord shall not be liable for injury or
damage which may be sustained by the person or property of Tenant, its
employees, invitees or customers, or any other person in or about the Premises,
caused by or resulting from fire, steam, electricity, gas, water or rain which
may leak or flow from or into any part of the Premises, or from the breakage,
leakage, obstruction or other defects of pipes, sprinklers, wires, appliances,
plumbing, air conditioning, lighting fixtures or mechanical or electrical
systems, whether such damage or injury results from conditions arising upon the
Premises or upon other portions of the Building or Project or from other
sources, unless the condition was the result of Landlord's negligence or willful
misconduct. Landlord shall not be liable for any damages arising from any act or
omission of any other tenant of the Building or Project or for

                                       11
<PAGE>

the acts of persons in, on or about the Premises, Building or the Project who
are not the authorized agents of Landlord or for losses due to theft, vandalism
or like causes.

Tenant acknowledges that Landlord's election to provide mechanical surveillance
or to post security personnel in the Building or on the Project is solely within
Landlord's discretion. Landlord shall have no liability in connection with the
decision whether or not to provide such services, and, to the extent permitted
by law, Tenant hereby waives all claims based thereon.

15.   TENANT'S INSURANCE.

      15.1. Insurance Requirement. Tenant shall procure and maintain insurance
coverage in accordance with the terms hereof, either as specific policies or
within blanket policies. Coverage shall begin on the date Tenant is given access
to the Premises for any purpose and shall continue until expiration of the Term,
except as otherwise set forth in the Lease. The cost of such insurance shall be
borne by Tenant.

Insurance shall be with insurers licensed to do business in the State, and
reasonably acceptable [ILLEGIBLE] Landlord. The insurers must have a current
A.M. Best's rating of not less than A:VII, or equivalent (as reasonably
determined by Landlord) if the Best's rating system is discontinued.

Tenant shall furnish Landlord with original certificates and amendatory
endorsements effecting coverage required by this Section 15. before the date
Tenant is first given access to the Premises. All certificates and endorsements
are to be received and approved by Landlord before any work commences. Landlord
reserves the right to inspect and/or copy any insurance policy required to be
maintained by Tenant hereunder, or to require complete, certified copies of all
required insurance policies, including endorsements effecting the coverage
require herein at any time. Tenant shall comply with such requirement within
thirty (30) days of demand therefor by Landlord. Tenant shall furnish Landlord
with renewal certificates and amendments or a "binder" of any such policy at
least twenty (20) days prior to the expiration thereof. Each insurance policy
required herein shall be endorsed to state that coverage shall not be canceled,
except after thirty (30) days' prior written notice to Landlord and Landlord's
lender (if such lender's address is provided).

The Commercial General Liability policy, as hereinafter required, shall contain,
or be endorsed to contain, the following provisions: (a) Landlord and any
parties designated by Landlord shall be covered as additional insureds as their
respective interests may appear; and (b) Tenant's insurance coverage shall be
primary insurance as to any insurance carried by the parties designated as
additional insureds. Any insurance or self-insurance maintained by Landlord
shall be excess of Tenant's insurance and shall not contribute with it.

      15.2. Minimum Scope of Coverage. Coverage shall be at least as broad as
set forth herein. However, if, because of Tenant's Use or occupancy of the
Premises, Landlord determines, in Landlord's reasonable judgment, that
additional insurance coverage or different types of insurance are necessary,
then Tenant shall obtain such insurance at Tenant's expense in accordance with
the terms of this Section 15.

            15.2.1. Commercial General Liability (ISO occurrence form CG 00 01)
      which shall cover liability arising from Tenant's Use and occupancy of the
      Premises, its operations therefrom, Tenant's independent contractors,
      products-completed operations, personal injury and advertising injury, and
      liability assumed under an insured contract.

            15.2.2. Workers' Compensation insurance as required by law, and
      Employers Liability insurance.

            15.2.3. Commercial Property Insurance (ISO special causes of loss
      form CP 10 30) against all risk of direct physical loss or damage
      (including flood, if applicable), earthquake excepted, for: (a) all
      leasehold improvements (including any alterations, additions or
      improvements made by Tenant pursuant to the provisions of Section 12.
      hereof) in, on or about the Premises; and (b) trade fixtures, merchandise
      and Tenant's Property from time to time in, on or about the Premises. The
      proceeds of such property insurance shall be used for the repair or
      replacement of the property so insured. Upon termination of this Lease
      following a casualty as set forth herein, the proceeds under (a) shall be
      paid to Landlord, and the proceeds under (b) above shall be paid to
      Tenant.

            15.2.4. Business Auto Liability.

Landlord shall, during the term hereof, maintain in effect similar insurance on
the Building and Common Area.

            15.2.5. Business Interruption and Extra Expense Insurance.

                                       12
<PAGE>

            15.3. Minimum Limits of Insurance. Tenant shall maintain limits not
      less than:

                  15.3.1. Commercial General Liability: $1,000,000 per
            occurrence. If the insurance contains a general aggregate limit,
            either the general aggregate limit shall apply separately to this
            location or the general aggregate limit shall be at least twice the
            required occurrence limit.

                  15.3.2. Employer's Liability: $1,000,000 per accident for
            bodily injury or disease.

                  15.3.3. Commercial Property Insurance: 100% replacement cost
            with no coinsurance penalty provision.

                  15.3.4. Business Auto Liability: $1,000,000 per accident.

                  15.3.5. Business Interruption and Extra Expense Insurance: In
            a reasonable amount and comparable to amounts carried by comparable
            tenants in comparable projects.

      15.4. Deductible and Self-Insured Retention. Any deductible or
self-insured retention in excess of $5,000 per occurrence must be declared to
and approved by Landlord. At the option of Landlord, either the insurer shall
reduce or eliminate such deductible or self-insured retention or Tenant shall
provide separate insurance conforming to this requirement.

      15.5. Increases in Insurance Policy Limits. If the coverage limits set
forth in this Section 15. are deemed inadequate by Landlord or Landlord's
lender, then Tenant shall increase the coverage limits to the amounts reasonably
recommended by either Landlord or Landlord's lender. Landlord agrees that any
such required increases in coverage limits shall not occur more frequently than
once every three (3) years.

      15.6. Waiver of Subrogation. Landlord and Tenant each hereby waive all
rights of recovery against the other and against the officers, employees, agents
and representatives, contractors and invitees of the other, on account of loss
by or damage to the waiving party or its property or the property of others
under its control, to the extent that such loss or damage is insured against
under any insurance policy which may have been in force at the time of such loss
or damage.

      15.7. Landlord's Right to Obtain Insurance for Tenant. If Tenant fails to
obtain the insurance coverage or fails to provide certificates and endorsements
as required by this Lease, Landlord may, at its option, obtain such insurance
for Tenant. Tenant shall pay, as Additional Rent, the reasonable cost thereof
together with a twenty-five percent (25%) service charge.

16.   DAMAGE OR DESTRUCTION.

      16.1. Damage. If, during the term of this Lease, the Premises or the
portion of the Building necessary for Tenant's occupancy is damaged by fire or
other casualty covered by fire and extended coverage insurance carried by
Landlord, Landlord shall promptly repair the damage provided (a) such repairs
can, in Landlord's opinion, be completed, under applicable laws and regulations,
within one hundred eighty (180) days of the date a permit for such construction
is issued by the governing authority, (b) insurance proceeds are available to
pay eighty percent (80%) or more of the cost of restoration, and (c) Tenant
performs its obligations pursuant to Section 16.4. hereof. In such event, this
Lease shall continue in full force and effect, except that Tenant shall be
entitled to a proportionate reduction of Rent to the extent Tenant's use at the
Premises is impaired, commencing with the date of damage and continuing until
completion of the repairs required of Landlord under Section 16.4.

Notwithstanding anything contained in the Lease to the contrary, in the event of
partial or total damage or destruction of the Premises during the last twelve
(12) months of the Term, either party shall have the option to terminate this
Lease upon thirty (30) days prior Notice to the other party provided such Notice
is served within thirty (30) days after the damage or destruction. For purposes
of this Section 16.1., "partial damage or destruction" shall mean the damage or
destruction of at least thirty-three and one-third percent (33 and 1/3%) of the
Premises, as determined by Landlord in Landlord's reasonable discretion.

      16.2. Repair of Premises in Excess of One Hundred Eighty Days. If in
Landlord's opinion, such repairs to the Premises or portion of the Building
necessary for Tenant's occupancy cannot be completed under applicable laws and
regulations within one hundred eighty (180) days of the date a permit for such
construction is issued by the governing authority, Landlord may elect, upon
Notice to Tenant given within thirty (30) days after the date of such fire or
other casualty, to repair such damage and to diligently prosecute repair to
completion, in which event this Lease shall continue in full force and effect,
but the Rent shall be partially abated as provided in Section 16.1. If Landlord
does not so elect to make such repairs, this Lease shall terminate as of the
date of such fire or other casualty.

                                       13
<PAGE>

      16.3. Repair Outside Premises. If any other portion of the Building or
Project is totally destroyed or damaged to the extent that in Landlord's opinion
repair thereof cannot be completed under applicable laws and regulations within
one hundred eighty (180) days of the date a permit for such construction is
issued by the governing authority, Landlord may elect upon Notice to Tenant
given within thirty (30) days after the date of such fire or other casualty, to
repair such damage, in which event this Lease shall continue in full force and
effect, but the Rent shall be partially abated as provided in Section 16.1. If
Landlord does not elect to make such repairs, this Lease shall terminate as of
the date of such fire or other casualty.

      16.4. Tenant Repair. If the Premises are to be repaired under this Section
16., Landlord shall repair at its cost any injury or damage to the Building and
Building Standard Tenant Improvements, if any. Notwithstanding anything
contained herein to the contrary, Landlord shall not be obligated to perform
work other than Landlord's Work performed previously pursuant to Section 12.1.
hereof. Tenant shall be responsible at its sole cost and expense for the repair,
restoration and replacement of any other Leasehold Improvements and Tenant's
Property (as well as reconstructing and reconnecting Tenant's internal
telecommunication wiring and related equipment). Landlord shall not be liable
for any loss of business, inconvenience or annoyance arising from any repair or
restoration of any portion of the Premises, Building or Project as a result of
any damage from fire or other casualty.

      16.5. Election Not to Perform Landlord's Work. Notwithstanding anything to
the contrary contained herein, Landlord shall provide Notice to Tenant of its
intent to repair or replace the Premises (if Landlord elects to perform such
work), and, within ten (10) days of its receipt of such Notice, Tenant shall
provide Notice to Landlord of its intent to reoccupy the Premises. Should Tenant
fail to provide such Notice to Landlord, then such failure shall be deemed an
election by Tenant not to re-occupy the Premises and Landlord may elect not to
perform the repair or replacement of the Premises. Such election shall not
result in a termination of this Lease and all obligations of Tenant hereunder
shall remain in full force and effect, including the obligation to pay Rent.

      16.6. Express Agreement. This Lease shall be considered an express
agreement governing any case of damage to or destruction of the Premises,
Building or Project by fire or other casualty, and any present or future law
which purports to govern the rights of Landlord and Tenant in such circumstances
in the absence of express agreement shall have no application.

17.   EMINENT DOMAIN.

      17.1. Whole Taking. If the whole of the Building or Premises is lawfully
taken by condemnation or in any other manner for any public or quasi-public
purpose, this Lease shall terminate as of the date of such taking, and Rent
shall be prorated to such date.

      l7.2. Partial Taking. If less than the whole of the Building or Premises
is so taken, this Lease shall be unaffected by such taking, provided that (a)
Tenant shall have the right to terminate this Lease by Notice to Landlord given
within ninety (90) days after the date of such taking if twenty percent (20%) or
more of the Premises is taken and the remaining area of the Premises is not
reasonably sufficient for Tenant to continue operation of its business, and (b)
Landlord shall have the right to terminate this Lease by Notice to Tenant given
within ninety (90) days after the date of such taking. If either Landlord or
Tenant so elects to terminate this Lease, the Lease shall terminate on the
thirtieth (30th) calendar day after either such Notice. Rent shall be prorated
to the date of termination. If this Lease continues in force upon such partial
taking, Rent and Tenant's Proportionate Share shall be equitably adjusted
according to the remaining Rentable Area of the Premises and Project.

      17.3. Proceeds. In the event of any taking, partial or whole, all of the
proceeds of any award, judgment or settlement payable by the condemning
authority shall be the exclusive property of Landlord, and Tenant hereby assigns
to Landlord all of its right, title and interest in any award, judgment or
settlement from the condemning authority; however, Tenant shall have the right,
to the extent that Landlord's award is not reduced or prejudiced, to claim from
the condemning authority (but not from Landlord) such compensation as may be
recoverable by Tenant in its own right for relocation expenses and damage to
Tenant's Property and damage to Leasehold Improvements installed at the sole
expense of Tenant.

      17.4. Landlord's Restoration. In the event of a partial taking of the
Premises which does not result in a termination of this Lease, Landlord shall
restore the remaining portion of the Premises as nearly as practicable to its
condition prior to the condemnation or taking; provided however, Landlord shall
not be obligated to perform work other than Landlord's Work performed previously
pursuant to Section 12.1. hereof. Tenant shall be responsible at its sole cost
and expense for the repair, restoration and replacement of Tenant's Property and
any other Leasehold Improvements.

                                       14
<PAGE>

18.   ASSIGNMENT AND SUBLETTING.

No assignment of this Lease or sublease of all or any part of the Premises shall
be permitted, except as provided in this Section 18.

      18.1. No Assignment or Subletting. Tenant shall not, without the prior
written consent of Landlord, assign or hypothecate this Lease or any interest
herein or sublet the Premises or any part thereof, or permit the use of the
Premises or any part thereof by any party other than Tenant. Any of the
foregoing acts without such consent shall be voidable and shall, at the option
of Landlord, constitute a default hereunder. This Lease shall not, nor shall any
interest of Tenant herein, be assignable by operation of law without the prior
written consent of Landlord.

            18.1.1. For purposes of this Section 18., the following shall be
      deemed an assignment:

                  18.1.1.1. If Tenant is a partnership, any withdrawal or
            substitution (whether voluntary, involuntary, or by operation of
            law, and whether occurring at one time or over a period of time) of
            any partner(s) owning twenty-five (25%) or more (cumulatively) of
            any interest in the capital or profits of the partnership, or the
            dissolution of the partnership;

                  18.1.1.2. If Tenant is a corporation, any dissolution, merger,
            consolidation, or other reorganization of Tenant, any sale or
            transfer (or cumulative sales or transfers) of the capital stock of
            Tenant in excess of twenty-five percent (25%), or any sale (or
            cumulative sales) or transfer of fifty-one (51%) or more of the
            value of the assets of Tenant provided, however, the foregoing shall
            not apply to corporations the capital stock of which is publicly
            traded.

      18.2. Landlord's Consent. If, at any time or from time to time during the
Term hereof, Tenant desires to assign this Lease or sublet all or any part of
the Premises, and if Tenant is not then in default under the terms of the Lease,
Tenant shall submit to Landlord a written request for approval setting forth the
terms and provisions of the proposed assignment or sublease, the Identity of the
proposed assignee or subtenant, and a copy of the proposed form of assignment or
sublease. Tenant's request for consent shall be submitted to Landlord at least
thirty (30) days prior to the intended date of such transfer. Tenant shall
promptly supply Landlord with such information concerning the business
background and financial condition of such proposed assignee or subtenant as
Landlord may reasonably request. Landlord shall have the right to approve such
proposed assignee or subtenant, which approval shall not be unreasonably
withheld or delayed. Landlord's consent to any assignment shall not be construed
as a consent to any subsequent assignment, subletting, transfer of partnership
interest or stock, occupancy or use.

            18.2.1. Landlord's approval shall be conditioned, among other
      things, on Landlord's receiving adequate assurances of future performance
      under this Lease and any sublease or assignment. In determining the
      adequacy of such assurances, Landlord may base its decision on such
      factors as it deems appropriate, including but not limited to:

                  18.2.1.1. that the source of rent and other consideration due
            under this Lease, and, in the case of assignment, that the financial
            condition and operating performance and business experience of the
            proposed assignee and its guarantors, if any, shall be equal to or
            greater than the financial condition and operating performance and
            experience of Tenant and its guarantors, if any, as of the time
            Tenant became the lessee under this Lease;

                  18.2.1.2. that any assumption or assignment of this Lease will
            not result in increased cost or expense, wear and tear, greater
            traffic or demand for services and utilities provided by Landlord
            pursuant to Section 10. hereof and will not disturb or be
            detrimental to other tenants of Landlord;

                  18.2.1.3. whether the proposed assignee's use of the Premises
            will include the use of Hazardous Material, or will in any way
            increase any risk to Landlord relating to Hazardous Material; and

                  18.2.1.4. that assumption or assignment of such lease will not
            disrupt any tenant mix or balance in the Project.

            18.2.2. Thc assignment or sublease shall be on the same terms and
      conditions set forth in the written request for approval given to
      Landlord, or, if different, upon terms and conditions consented to by
      Landlord;

            18.2.3. No assignment or sublease shall be valid and no assignee or
      sublessee shall take possession of the Premises or any part thereof until
      an executed counterpart of such assignment or sublease has been delivered
      to Landlord;

                                       15
<PAGE>

            18.2.4. No assignee or sublessee shall have a further right to
      assign or sublet except on the terms herein contained;

            18.2.5. Any sums or other economic considerations received by Tenant
      as a result of such assignment or subletting, however denominated under
      the assignment or sublease, which exceed, in the aggregate (a) the total
      sums which Tenant is obligated to pay Landlord under this Lease (prorated
      to reflect obligations allocable to any portion of the Premises
      subleased), plus (b) any real estate brokerage commissions or fees payable
      to third parties in connection with such assignment or subletting, shall
      be shared equally by Tenant and Landlord as Additional Rent under this
      Lease without effecting or reducing any other obligations of Tenant
      hereunder.

If Landlord consents to the proposed transfer, Tenant shall deliver to Landlord
three (3) fully executed original documents (in the form previously approved by
Landlord) and Landlord shall attach its consent thereto. Landlord shall retain
one (1) fully executed original document. No transfer of Tenant's interest in
this Lease shall be deemed effective until the terms and conditions of this
Section 18. have been fulfilled.

      18.3. Tenant Remains Responsible. No subletting or assignment shall
release Tenant of Tenant's obligations under this Lease or alter the primary
liability of Tenant to pay the Rent and to perform all other obligations to be
performed by Tenant hereunder. The acceptance of Rent by Landlord from any other
person shall not be deemed to be a waiver by Landlord of any provision hereof.
Consent to one assignment or subletting shall not be deemed consent to any
subsequent assignment or subletting. In the event of default by an assignee or
subtenant of Tenant or any successor of Tenant in the performance of any of the
terms hereof, Landlord may proceed directly against Tenant without the necessity
of exhausting remedies against such assignee, subtenant or successor. Landlord
may consent to subsequent assignments or sublets of the Lease or amendments or
modifications to the Lease with assignees of Tenant, without notifying Tenant,
or any successor of Tenant, and without obtaining its or their consent thereto
and any such actions shall not relieve Tenant of liability under this Lease.

      18.4. Conversion to a Limited Liability Entity. Notwithstanding anything
contained herein to the contrary, if Tenant is a limited or general partnership
(or is comprised of two (2) or more persons, individually or as co-partners, or
entities), the change or conversion of Tenant to (a) a limited liability
company, (b) a limited liability partnership, or (c) any other entity which
possesses the characteristics of limited liability (any such limited liability
entity is collectively referred to herein as a "Successor Entity") shall be
prohibited unless the prior written consent of Landlord is obtained, which
consent may be withheld in Landlord's sole discretion.

            18.4.1. Notwithstanding Section 18.4., Landlord agrees not to
      unreasonably withhold or delay such consent provided that:

                  18.4.1.1. The Successor Entity succeeds to all or
            substantially all of Tenant's business and assets;

                  18.4.1.2. The Successor Entity shall have a tangible net worth
            (Tangible Net Worth), determined in accordance with generally
            accepted accounting principles, consistently applied, of not less
            than the greater of the Tangible Net Worth of Tenant on (a) the date
            of execution of the Lease, or (b) the day immediately preceding the
            proposed effective date of such conversion; and

                  18.4.1.3. Tenant is not in default of any of the terms,
            covenants, or conditions of this Lease on the propose effective date
            of such conversion.

      18.5. Payment of Fees. If Tenant assigns the Lease or sublets the Premises
or requests the consent of Landlord to any assignment, subletting or conversion
to a limited liability entity, then Tenant shall, upon demand, pay Landlord,
whether or not consent is ultimately given, an administrative fee of Three
Hundred and 00/100 Dollars ($300.00) plus costs and other reasonable expenses
incurred by Landlord in connection with each such act or request.

19.   DEFAULT.

      19.1. Tenant's Default. The occurrence of any one or more of the following
events shall constitute a default and breach of this Lease by Tenant.

            19.1.1. If Tenant abandons or vacates the Premises, and fails to pay
      rent therefor.

            19.1.2. If Tenant fails to pay any Rent or Additional Rent or any
      other charges required to be paid by Tenant under this Lease and such
      failure continues for three (3) days after receipt of Notice thereof from
      Landlord to Tenant.

                                       16
<PAGE>

            19.1.3. If Tenant fails to promptly and fully perform any other
      covenant, condition or agreement contained in this Lease and such failure
      continues for thirty (30) days after Notice thereof from Landlord to
      Tenant, or, if such default cannot reasonably be cured within thirty (30)
      days, if Tenant fails to commence to cure within that thirty (30) day
      period and diligently prosecute to completion.

            19.1.4. Tenant's failure to occupy the Premises within ten (10) days
      after delivery of possession (as defined in Section 4. hereof).

            19.1.5. Tenant's failure to provide any document, instrument or
      assurance as required by Sections 12., 15., 18. and/or 35. if the failure
      continues for ten (10) days after receipt of Notice from Landlord to
      Tenant.

            19.1.6. To the extent provided by law:

                  19.1.6.1. If a writ of attachment or execution is levied on
            this Lease or on substantially all of Tenant's Property; or

                  19.1.6.2. If Tenant or Tenant's Guarantor makes a general
            assignment for the benefit of creditors; or

                  19.1.6.3. If Tenant files a voluntary petition for relief or
            if a petition against Tenant in a proceeding under the federal
            bankruptcy laws or other insolvency laws is filed and not withdrawn
            or dismissed within sixty (60) days thereafter, or if under the
            provisions of any law providing for reorganization or winding up of
            corporations, any court of competent jurisdiction assumes
            jurisdiction, custody or control of Tenant or any substantial part
            of its property and such jurisdiction, custody or control remains in
            force unrelinquished, unstayed or unterminated for a period of sixty
            (60) days; or

                  19.1.6.4. If in any proceeding or action in which Tenant is a
            party, a trustee, receiver, agent or custodian is appointed to take
            charge of the Premises or Tenant's Property (or has the authority to
            do so); or

                  19.1.6.5. If Tenant is a partnership or consists of more than
            one (1) person or entity, if any partner of the partnership or other
            person or entity is involved in any of the acts or events described
            in Sections 19.1.6.1. through 19.1.6.4. above.

      19.2. Landlord Remedies. In the event of Tenant's default hereunder, then,
in addition to any other rights or remedies Landlord may have under any law or
at equity, Landlord shall have the right to collect interest on all past due
sums (at the maximum rate permitted by law to be charged by an individual), and,
at Landlord's option and without further notice or demand of any kind, to do the
following:

            19.2.1. Terminate this Lease and Tenant's right to possession of the
      Premises and reenter the Premises and take possession thereof, and Tenant
      shall have no further claim to the Premises or under this Lease; or

            19.2.2. Continue this Lease in effect, reenter and occupy the
      Premises for the account of Tenant, and collect any unpaid Rent or other
      charges which have or thereafter become due and payable; or

            l9.2.3. Reenter the Premises under the provisions of Section
      19.2.2., and thereafter elect to terminate this Lease and Tenant's right
      to possession of the Premises.

If Landlord reenters the Premises under the provisions of Sections 19.2.2. or
19.2.3. above, Landlord shall not be deemed to have terminated this Lease or the
obligation of Tenant to pay any Rent or other charges thereafter accruing unless
Landlord notifies Tenant in writing of Landlord's election to terminate this
Lease. Acts of maintenance, efforts to relet the Premises or the appointment of
a receiver on Landlord's initiative to protect Landlord's interest under this
Lease shall not constitute a termination of Tenant's obligations under the
Lease. In the event of any reentry or retaking of possession by Landlord,
Landlord shall have the right, but not the obligation, to remove all or any part
of Tenant's Property in the Premises and to place such property in storage at a
public warehouse at the expense and risk of Tenant. Landlord shall use
reasonable efforts to relet the Premises. If Landlord relets the Premises for
the account of Tenant, the rent received by Landlord from such reletting shall
be applied as follows: first, to the payment of any indebtedness other than Rent
due hereunder from Tenant to Landlord; second, to the payment of reasonable any
costs of such reletting; third, to the payment of the cost of any alterations or
repairs to the Premises; fourth to the payment of Rent due and unpaid hereunder;
and the balance, if any, shall be held by Landlord and applied in payment of
future Rent as it becomes due. If that portion of Rent received from the
reletting which is applied against the Rent due hereunder is less than the
amount of the Rent due, Tenant shall pay the deficiency to Landlord promptly
upon demand by Landlord. Such deficiency shall be calculated and paid monthly.
Tenant shall also pay to Landlord, as soon as determined, any costs and expenses
incurred by Landlord in connection with such reletting or in making alterations
and repairs to the Premises which are not covered by the rent received from the
reletting.

                                       17
<PAGE>

      19.3. Damages Recoverable. Should Landlord elect to terminate this Lease
under the provisions of Section 19.2., Landlord may recover as damages from
Tenant the following:

            19.3.1. Past Rent. The worth at the time of the award of any unpaid
      Rent that had been earned at the time of termination including the value
      of any Rent that was abated during the Term of the Lease (except Rent that
      was abated as a result of damage or destruction or condemnation); plus

            19.3.2. Rent Prior to Award. The worth at the time of the award of
      the amount by which the unpaid Rent that would have been earned between
      the time of the termination and the time of the award exceeds the amount
      of unpaid Rent that Tenant proves could reasonably have been avoided; plus

            19.3.3. Rent After Award. The worth at the time of the award of the
      amount by which the unpaid Rent for the balance of the Term after the time
      of award exceeds the amount of the unpaid Rent that Tenant proves could be
      reasonably avoided; plus

            19.3.4. Proximately Caused Damages. Any other amount necessary to
      compensate Landlord for all detriment proximately caused by Tenant's
      failure to perform its obligations under this Lease or which in the
      ordinary course of things would be likely to result therefrom, including,
      but not limited to, any costs or expenses (including attorneys' fees),
      incurred by Landlord in (a) retaking possession of the Premises, (b)
      maintaining the Premises after Tenant's default, (e) preparing the
      Premises for reletting to a new tenant, including any repairs or
      alterations, and (d) reletting the Premises, including brokers'
      commissions.

"The worth at the time of the award" as used in Sections 19.3.1. and 19.3.2.
above, is to be computed by allowing interest at the maximum rate permitted by
law to be charged by an individual. "The worth at the time of the award" as used
in Section 19.3.3. above, is to be computed by discounting the amount at the
discount rate of the Federal Reserve Bank situated nearest to the Premises at
the time of the award plus one percent (1%).

      19.4. Landlord's Right to Cure Tenant's Default. If Tenant defaults in the
performance of any of its obligations under this Lease and Tenant has not timely
cured the default after Notice, Landlord may (but shall not be obligated to),
without waiving such default, perform the same for the account and at the
expense of Tenant. Tenant shall pay Landlord all costs of such performance
immediately upon written demand therefor, and if paid at a later date these
costs shall bear interest at the maximum rate permitted by law to be charged by
an individual.

      19.5. Landlord's Default. If Landlord fails to perform any covenant,
condition or agreement contained in this Lease within thirty (30) days after
receipt of Notice from Tenant specifying such default, or, if such default
cannot reasonably be cured within thirty (30) days if Landlord fails to commence
to cure within that thirty (30) day period and diligently prosecute to
completion, then Landlord shall be liable to Tenant for any damages sustained by
Tenant as a result of Landlord's breach; provided, however, it is expressly
understood and agreed that if Tenant obtains a money judgment against Landlord
resulting from any default or other claim arising under this Lease, that
judgment shall be satisfied only out of the rents, issues, profits, and other
income actually received on account of Landlord's right, title and interest in
the Premises, Building or Project, and no other real, personal or mixed property
of Landlord (or of any of the partners which comprise Landlord, if any),
wherever situated, shall be subject to levy to satisfy such judgment.

      19.6. Mortgagee Protection. Tenant agrees to send by certified or
registered mail to any first mortgagee or first deed of trust beneficiary of
Landlord whose address has been furnished to Tenant, a copy of any notice of
default served by Tenant on Landlord. If Landlord fails to cure such default
within the time provided for in this Lease, then such mortgagee or beneficiary
shall have such additional time to cure the default as is reasonably necessary
under the circumstances.

      19.7. Tenant's Right to Cure Landlord's Default. If, after Notice to
Landlord of default, Landlord (or any first mortgagee or first deed of trust
beneficiary of Landlord) fails to cure the default as provided herein, then
Tenant shall have the right to cure that default at Landlord's expense. Tenant
shall not have the right to terminate this Lease or to withhold, reduce or
offset any amount against any payments of Rent or any other charges due and
payable under this Lease except as otherwise specifically provided herein.
Tenant expressly waives the benefits of any statute now or hereafter in effect
which would otherwise afford Tenant the right to make repairs at Landlord's
expense or to terminate this Lease because of Landlord's failure to keep the
Premises in good order, condition and repair. Notwithstanding anything herein to
the contrary, Landlord shall use reasonable efforts to relet the Premises and to
otherwise mitigate its damages following a Tenants default.

20.   WAIVER.

No delay or omission in the exercise of any right or remedy of Landlord upon any
default by Tenant shall impair such right or remedy or be construed as a waiver
of such default. The receipt and acceptance by Landlord of delinquent Rent shall
not constitute a waiver of any

                                       18
<PAGE>

other default; it shall constitute only a waiver of timely payment for the
particular Rent payment involved (excluding the collection of a late charge or
interest).

No act or conduct of Landlord, including, without limitation, the acceptance of
keys to the Premises, shall constitute an acceptance of the surrender of the
Premises by Tenant before the expiration of the Term. Only written
acknowledgement from Landlord to Tenant shall constitute acceptance of the
surrender of the Premises and accomplish a termination of this Lease.

Landlord's consent to or approval of any act by Tenant requiring Landlord's
consent or approval shall not be deemed to waive or render unnecessary
Landlord's consent to or approval of any subsequent act by Tenant.

Any waiver by Landlord of any default must be in writing and shall not be a
waiver of any other default concerning the same or any other provision of this
Lease.

21.   SUBORDINATION AND ATTORNMENT.

This Lease is and shall be subject and subordinate to all ground or underlying
leases (including renewals, extensions, modifications, consolidations and
replacements thereof) which now exist or may hereafter be executed affecting the
Building or the land upon which the Building is situated, or both, and to the
lien of any mortgages or deeds of trust in any amount or amounts whatsoever
(including renewals, extensions, modifications, consolidations and replacements
thereof) now or hereafter placed on or against the Building or on or against
Landlord's interest or estate therein, or on or against any ground or underlying
lease, without the necessity of the execution and delivery of any further
instruments on the part of Tenant to effectuate such subordination.
Nevertheless, Tenant covenants and agrees to execute and deliver upon demand,
without charge therefor, such further instruments evidencing such subordination
of this Lease to such ground or underlying leases, and to the lien of any such
mortgages or deeds of trust as may be required by Landlord. Notwithstanding the
foregoing, Landlord will use reasonable efforts to help Tenant obtain a
Subordination and Non-Disturbance Agreement, at no cost to Landlord.

Notwithstanding anything contained herein to the contrary, if any mortgagee,
trustee or ground lessor shall elect that this Lease is senior to the lien of
its mortgage, deed of trust or ground lease, and shall give written notice
thereof to Tenant, this Lease shall be deemed prior to such mortgage, deed of
trust or ground lease, whether this Lease is dated prior or subsequent to the
date of said mortgage, deed of trust, or ground lease, or the date of the
recording thereof.

In the event of any foreclosure sale, transfer in lieu of foreclosure or
termination of the lease in which Landlord is lessee, Tenant shall attorn to the
purchaser, transferee or lessor as the case may be, and recognize that party as
Landlord under this Lease, provided such party acquires and accepts the Premises
subject to this Lease.

22.   TENANT ESTOPPEL CERTIFICATES.

      22.1. Landlord Request for Estoppel Certificate. Within fifteen (15) days
after written request from Landlord, Tenant shall execute and deliver to
Landlord or Landlord's designee, in the form requested by Landlord, a written
statement certifying, among other things, (a) that this Lease is unmodified and
in full force and effect, or that it is in full force and effect as modified and
stating the modifications; (b) the amount of Base Rent and the date to which
Base Rent and Additional Rent have been paid in advance; (c) the amount of any
security deposited with Landlord; and (d) that Landlord is not in default
hereunder or, if Landlord is claimed to be in default, stating the nature of any
claimed default. Any such statement may be conclusively relied upon by a
prospective purchaser, assignee or encumbrancer of the Premises.

      22.2. Failure to Execute. Tenant's failure to execute and deliver such
statement within the time required shall at Landlord's election be a default
under this Lease (within five (5) days of Landlord giving Tenant a Notice of
Default and an opportunity to cure) and shall also be conclusive upon Tenant
that: (a) this Lease is in full force and effect and has not been modified
except as represented by Landlord; (b) there are no uncured defaults in
Landlord's performance and that Tenant has no right of offset, counter-claim or
deduction against Rent and (c) not more than one month's Rent has been paid in
advance.

23.   NOTICE.

Notice shall be in writing and shall be deemed duly served or given if
personally delivered, sent by certified or registered U.S. Mail, postage prepaid
with a return receipt requested, or sent by overnight courier service, fee
prepaid with a return receipt requested, as follows: (a) if to Landlord, to
Landlord's Address for Notice with a copy to the Building manager, and (b) if to
Tenant, to Tenant's Mailing Address; provided, however, Notices to Tenant shall
be deemed duly served or given if delivered or sent to Tenant at the Premises.
Landlord and Tenant may from time to time by Notice to the other designate
another place for receipt of future Notice. Notwithstanding anything contained
herein to the contrary, when an applicable

                                       19
<PAGE>

State statute requires service of Notice in a particular manner, service of that
Notice in accordance with those particular requirements shall replace rather
than supplement any Notice requirement set forth in the Lease.

24.   TRANSFER OF LANDLORD'S INTEREST.

In the event of any sale or transfer by Landlord of the Premises, Building or
Project, and assignment of this Lease by Landlord, Landlord shall be and is
hereby entirely freed and relieved of any and all liability and obligations
contained in or derived from this Lease arising out of any act, occurrence or
omission relating to the Premises, Building, Project or Lease occurring after
the consummation of such sale or transfer, provided the purchaser shall
expressly assume all of the covenants and obligations of Landlord under this
Lease. This Lease shall not be affected by any such sale and Tenant agrees to
attorn to the purchaser or assignee provided all Landlord's obligation hereunder
are assumed by such transferee. If any security deposit or prepaid Rent has been
paid by Tenant, Landlord shall transfer the security deposit or prepaid Rent to
Landlord's successor and upon such transfer, Landlord shall be relieved of any
and all further liability with respect thereto.

25.   SURRENDER OF PREMISES.

      25.1. Clean and Same Condition. Upon the Expiration Date or earlier
termination of this Lease, Tenant shall peaceably surrender the Premises to
Landlord clean and in the same condition as when received, except for (a)
reasonable wear and tear, (b) loss by fire or other casualty, and (c) loss by
condemnation. Tenant shall remove Tenant's Property no later than the Expiration
Date. If Tenant is required by Landlord to remove any additions, alterations, or
improvements under Section 12.3., Tenant shall complete such removal no later
than the Expiration Date. Any damage to the Premises, including any structural
damage, resulting from removal of any addition, alteration, or improvement made
pursuant to Section 12.3. and/or from Tenant's use or from the removal of
Tenant's Property pursuant to Section 13.2. shall be repaired (in accordance
with Landlord's reasonable direction) no later than the Expiration Date by
Tenant at Tenant's sole cost and expense. On the Expiration Date Tenant shall
surrender all keys to the Premises.

      25.2. Failure to Deliver Possession. If Tenant fails to vacate and deliver
possession of the Premises to Landlord on the expiration or sooner termination
of this Lease as required by Section 25.1., Tenant shall indemnify, defend and
hold Landlord harmless from all claims, liabilities and damages resulting from
Tenant's failure to vacate and deliver possession of the Premises, including,
without limitation, claims made by a succeeding tenant resulting from Tenant's
failure to vacate and deliver possession of the Premises and rental loss which
Landlord suffers.

      25.3. Property Abandoned. If Tenant abandons or surrenders the Premises,
or is dispossessed by process of law or otherwise, any of Tenant's Property left
on the Premises shall be deemed to be abandoned, and, at Landlord's option,
title shall pass to Landlord under this Lease as by a bill of sale. If Landlord
elects to remove all or any part of such Tenant's Property, the cost of removal,
including repairing any damage to the Premises or Building caused by such
removal, shall be paid by Tenant.

26.   HOLDING OVER.

Tenant shall not occupy the Premises after the Expiration Date without
Landlord's consent. If after expiration of the Term, Tenant remains in
possession of the Premises with Landlord's permission (express or implied),
Tenant shall become a tenant from month to month only upon all the provisions of
this Lease (except as to the term and Base Rent). Monthly installments of Base
Rent payable by Tenant during this period shall be increased to one hundred
fifty percent (150%) of the Monthly Installments of Base Rent payable by Tenant
in the final month of the Term. Such monthly rent shall be payable in advance on
or before the first day of each month. The tenancy may be terminated by either
party by delivering a thirty (30) day Notice to the other party. Nothing
contained in this Section 26. shall be construed to limit or constitute a waiver
of any other rights or remedies available to Landlord pursuant to this Lease or
at law.

27.   RULES AND REGULATIONS.

Tenant agrees to comply with (and cause its agents, contractors, employees and
invitees to comply with) the rules and regulations attached hereto as Exhibit
"E" and with such reasonable modifications thereof and additions thereto as
Landlord may from time to time make. Landlord agrees to enforce the rules and
regulations uniformly against all tenants of the Project. Landlord shall not be
liable, however, for any violation of said rules and regulations by other
tenants or occupants of the Building or Project.

                                       20
<PAGE>

28.   CERTAIN RIGHTS RESERVED BY LANDLORD.

Landlord reserves the following rights, exercisable without (a) liability to
Tenant for damage or injury to property, person or business; (b) being found to
have caused an actual or constructive eviction from the Premises; or (c) being
found to have disturbed Tenant's use or possession of the Premises.

      28.1. To name the Building and Project and to change the name or street
address of the Building or Project.

      28.2. To install and maintain all signs on the exterior and interior of
the Building and Project.

      28.3. To have pass keys to the Premises and all doors within the Premises,
excluding Tenant's files, vaults and safes.

      28.4. To stripe or re-stripe, re-surface, enlarge, change the grade or
drainage of and control access to the parking lot; to assign and reassign spaces
for the exclusive or nonexclusive use of tenants (including Tenant); and to
locate or relocate parking spaces assigned to Tenant.

      28.5. At any time during the Term, and on prior telephonic notice to
Tenant, to inspect the Premises, and to show the Premises to any person having
an existing or prospective interest in the Project or Landlord, and during the
last six months of the Term, to show the Premises to prospective tenants
thereof.

      28.6. To enter the Premises for the purpose of making inspections,
repairs, alterations, additions or improvements to the Premises or the Building
(including, without limitation, checking, calibrating, adjusting or balancing
controls and other parts of the HVAC system), and to take all steps as may be
necessary or desirable for the safety, protection, maintenance or preservation
of the Premises or the Building or Landlord's interest therein, or as may be
necessary or desirable for the operation or improvement of the Building or in
order to comply with laws, orders or requirements of governmental or other
authority. Landlord agrees to use its best efforts (except in an emergency) to
minimize interference with Tenant's business in the Premises in the course of
any such entry.

      28.7. To exclusively regulate and control use of the Common Area.

29.   ADVERTISEMENTS AND SIGNS.

Tenant shall not affix, paint, erect or inscribe any sign, projection, awning,
signal or advertisement of any kind to any part of the Premises, Building or
Project, including without limitation the inside or outside of windows or doors,
without the prior written consent of Landlord. Landlord shall have the right to
remove any signs or other matter installed without Landlord's permission,
without being liable to Tenant by reason of such removal, and to charge the cost
of removal to Tenant as Additional Rent hereunder, payable within ten (10) days
of written demand by Landlord. Landlord shall remove the existing outside sign
on the property. Tenant shall have the right to place a sign on the outside of
the Building, at no cost to the Landlord, subject to the rules and regulations
of the Town of Westford and the State of Massachusetts if applicable.

31.   GOVERNMENT ENERGY OR UTILITY CONTROLS.

In the event of imposition of federal, state or local government controls,
rules, regulations, or restrictions on the use or consumption of energy or other
utilities (including telecommunications) during the Term, both Landlord and
Tenant shall be bound thereby. In the event of a difference in interpretation by
Landlord and Tenant of any such controls, the interpretation of Landlord shall
prevail and Landlord shall have the right to enforce compliance therewith,
including the right of entry into the Premises to effect compliance.

                                       21
<PAGE>

32.   FORCE MAJEURE.

Any prevention, delay or stoppage of work to be performed by Landlord or Tenant
which is due to strikes, labor disputes, inability to obtain labor, materials,
equipment or reasonable substitutes therefor, acts of God, governmental
restrictions or regulations or controls, judicial orders, enemy or hostile
government actions, civil commotion, fire or other casualty, or other causes
beyond the reasonable control of the party obligated to perform hereunder, shall
excuse performance of the work by that party for a period equal to the duration
of that prevention, delay or stoppage. Nothing in this Section 32. shall excuse
or delay Tenant's obligation to pay Rent or other charges under this Lease.

33.   BROKERAGE FEES.

Tenant warrants and represents that it has not dealt with any real estate broker
or agent in connection with this Lease or its negotiation except the Listing and
Leasing Agent(s) set forth in Section 2.9. of this Lease. Tenant shall
indemnify, defend and hold Landlord harmless from any cost, expense or liability
(including costs of suit and reasonable attorneys' fees) for any compensation,
commission or fees claimed by any other real estate broker or agent in
connection with this Lease or its negotiation by reason of any act of Tenant.

34.   QUIET ENJOYMENT.

Tenant shall, upon payment of Rent and performance of all of its obligations
under this Lease, peaceably, quietly and exclusively enjoy possession of the
Premises without unwarranted interference by Landlord or anyone acting or
claiming through Landlord, subject to the terms of this Lease and to any
mortgage, lease, or other agreement to which this Lease may be subordinate.

35.   TELECOMMUNICATIONS.

      35.1. Telecommunications Companies. Tenant and Tenant's telecommunications
companies, including but not limited to local exchange telecommunications
companies and alternative access vendor services companies ("Telecommunications
Companies"), shall have no right of access to and within the lands or Buildings
comprising the Project for the installation and operation of telecommunications
lines and systems including but not limited to voice, video, data, and any other
telecommunications services provided over wire, fiber optic, microwave, wireless
and any other transmission systems, for part or all of Tenant's
telecommunications within the Building and from the Building to any other
location (hereinafter collectively referred to as "Telecommunications Lines"),
without Landlord's prior written consent, which Landlord may withhold in its
sole and absolute discretion. Notwithstanding the foregoing, Tenant may perform
any installation, repair and maintenance to its Telecommunications Lines without
Landlord's consent where the equipment being installed, repaired or maintained
is not located in an area in which the Telecommunications Lines or any part
thereof of any other tenant or of Landlord are located.

      35.2. Tenant's Obligations. If at any time, Tenant's Telecommunications
Companies or appropriate governmental authorities relocate the point of
demarcation from the location of Tenant's telecommunications equipment in
Tenant's telephone equipment room or other location, to some other point, or in
any other manner transfer any obligations or liabilities for telecommunications
to Landlord or Tenant, whether by operation of law or otherwise, upon Landlord's
election, Tenant shall, at Tenant's sole expense and cost: (1) within thirty
(30) days after notice is first given to Tenant of Landlord's election, cause to
be completed by an appropriate telecommunications engineering entity approved in
advance in writing by Landlord, all details of the Telecommunications Lines
serving Tenant in the Building which details shall include all appropriate
plans, schematics, and specifications; and (2) if Landlord so elects,
immediately undertake the operation, repair and maintenance of the
Telecommunications Lines serving Tenant in the Building; and (3) upon the
termination of the Lease for any reason, or upon expiration of the Lease,
immediately effect the complete removal of all or any portion or portions of the
Telecommunications Lines serving Tenant in the Building and repair any damage
caused thereby (to Landlord's reasonable satisfaction).

      Prior to the commencement of any alterations, additions, or modifications
to the Telecommunications Lines serving Tenant in the Building, except for minor
changes, Tenant shall first obtain Landlord's prior written consent by written
request accompanied by detailed plans, schematics, and specifications showing
all alterations, additions and modifications to be performed, with the time
schedule for completion of the work, and the identity of the entity which will
perform the work, for which, except as otherwise provided in Section 35.3.
below, Landlord may withhold consent in its sole and absolute discretion.

                                       22
<PAGE>

      35.3. Landlord's Consent. Without in any way limiting Landlord's right to
withhold its consent to a proposed request for access, or for alterations,
additions or modifications of the Telecommunications Lines serving Tenant in the
Building, Landlord shall consider the following factors in making its
determination:

            35.3.1. If the proposed actions of Tenant and its Telecommunications
      Companies will impose new obligations on Landlord, or expose Landlord to
      liability of any nature or description, or increase Landlord's insurance
      costs for the Building, or create liabilities for which Landlord is unable
      to obtain insurance protection, or imperil Landlord's insurance coverage;

            35.3.2. If Tenant's Telecommunications Companies are unwilling to
      pay reasonable monetary compensation for the use and occupation of the
      Building for the Telecommunications Lines;

            35.3.3. If Tenant and its Telecommunications Companies would cause
      any work to be performed that would adversely affect the land and Building
      or any space in the Building in any manner;

            35.3.4. If Tenant encumbers or mortgages its interest in any
      telecommunications wiring or cabling; or

            35.3.5. If Tenant is in default under this Lease.

      35.4. Indemnification. Tenant shall indemnify, defend and hold harmless
Landlord and its employees, agents, officers, and directors from and against any
claims, demands, penalties, fines, liabilities, settlements, damages, costs, or
expenses of any kind or nature, known or unknown, contingent or otherwise,
arising out of or in any way related to the acts and omissions of Tenant,
Tenant's officers, directors, employees, agents, contractors, subcontractors,
subtenants, and invitees with respect to (1) any Telecommunications Lines
serving Tenant in the Building which are on, from, or affecting the Project and
Building; (2) any bodily injury (including wrongful death) or property damage
(real or personal) arising out of or related to any Telecommunications Lines
serving Tenant in the Building which are on, from, or affecting the Building;
(3) any lawsuit brought or threatened, settlement reached, or governmental order
relating to such Telecommunications Lines; (4) any violations of laws, orders,
regulations, requirements, or demands of governmental authorities, or any
reasonable policies or requirements of Landlord, which are based upon or in any
way related to such Telecommunications Lines, including, without limitation,
attorney and consultant fees, court costs, and litigation expenses. This
indemnification and hold harmless agreement will survive this Lease. Under no
circumstances shall Landlord be required to maintain, repair or replace any
Building systems or any portions thereof, when such maintenance, repair or
replacement is caused in whole or in part by the failure of any such system or
any portions thereof, and/or the requirements of any governmental authorities.
Under no circumstances shall Landlord be liable for interruption in
telecommunications services to Tenant or any other entity affected, for
electrical spikes or surges, or for any other cause whatsoever, whether by Act
of God or otherwise, even if the same is caused by the ordinary negligence of
Landlord, Landlord's contractors, subcontractors, or agents or other tenants,
subtenants, or their contractors, subcontractors, or agents.

      35.5. Landlord's Operation of Building Telecommunications Lines and
Systems. Notwithstanding anything contained herein to the contrary, if the point
of demarcation is relocated, Landlord may, but shall not be obligated to,
undertake the operation, repair and maintenance of telecommunications lines and
systems in the Building. If Landlord so elects, Landlord shall give Notice of
its intent to do so, and Landlord shall, based on Landlord's sole business
discretion, make such lines and systems available to tenants of the Building
(including Tenant) in the manner it deems most prudent. Landlord may include in
Operating Expenses all or a portion of the expenses related to the operation,
repair and maintenance of the telecommunications lines and systems.

36.   MISCELLANEOUS.

      36.1. Accord and Satisfaction; Allocation of Payments. No payment by
Tenant or receipt by Landlord of a lesser amount than the Rent provided for in
this Lease shall be deemed to be other than on account of the earliest due Rent,
nor shall any endorsement or statement on any check or letter accompanying any
check or payment as Rent be deemed an accord and satisfaction, and Landlord may
accept such check or payment without prejudice to Landlord's right to recover
the balance of the Rent or pursue any other remedy provided for in this Lease.
In connection with the foregoing, Landlord shall have the absolute right in its
sole discretion to apply any payment received from Tenant to any account or
other payment of Tenant then not current and due or delinquent.

      36.2. Addenda. If any provision contained in an addendum to this Lease is
inconsistent with any other provision herein, the provision contained in the
addendum shall control, unless otherwise provided in the addendum.

                                       23
<PAGE>

      36.3. Captions and Section Numbers. The captions appearing in the body of
this Lease have been inserted as a matter of convenience and for reference only
and in no way define, limit or enlarge the scope or meaning of this Lease. All
references to Section numbers refer to Sections in this Lease.

      36.4. Changes Requested by Lender. Neither Landlord nor Tenant shall
unreasonably withhold its consent to changes or amendments to this Lease
requested by the lender on Landlord's interest, so long as such changes do not
alter the basic business terms of this Lease or otherwise materially diminish
any rights or materially increase any obligations of the party from whom consent
to such change or amendment is requested.

      36.5. Choice of Law. This Lease shall be construed and enforced in
accordance with the Laws of the State.

      36.6. Consent. Notwithstanding anything contained in this Lease to the
contrary, Tenant shall have no claim, and hereby waives the right to any claim
against Landlord for money damages, by reason of any refusal, withholding or
delay by Landlord of any consent, approval or statement of satisfaction, and, in
such event, Tenant's only remedies therefor shall be an action for specific
performance, injunction or declaratory judgment to enforce any right to such
consent, approval or statement of satisfaction.

      36.7. Authority. If Tenant is not an individual signing on his or her own
behalf, then each individual signing this Lease on behalf of the business entity
that constitutes Tenant represents and warrants that the individual is duly
authorized to execute and deliver this Lease on behalf of the business entity,
and that this Lease is binding on Tenant in accordance with its terms. Tenant
shall, at Landlord's request, deliver a certified copy of a resolution of its
board of directors, if Tenant is a corporation, or other memorandum of
resolution if Tenant is a limited partnership, general partnership or limited
liability entity, authorizing such execution.

      36.8. Waiver of Right to Jury Trial. Landlord and Tenant hereby waive
their respective rights to a trial by jury of any claim, action, proceeding or
counterclaim by either party against the other on any matters arising out of or
in any way connected with this Lease, the relationship of Landlord and Tenant,
and/or Tenant's Use or occupancy of the Premises, Building or Project (including
any claim of injury or damage or the enforcement of any remedy under any current
or future laws, statutes, regulations, codes or ordinances).

      36.9. Counterparts. This Lease may be executed in multiple counterparts,
all of which shall constitute one and the same Lease.

      36.10. Execution of Lease; No Option. The submission of this Lease to
Tenant shall be for examination purposes only and does not and shall not
constitute a reservation of or option for Tenant to Lease, or otherwise create
any interest of Tenant in the Premises or any other premises within the Building
or Project. Execution of this Lease by Tenant and its return to Landlord shall
not be binding on Landlord, notwithstanding any time interval, until Landlord
has in fact signed and delivered this Lease to Tenant.

      36.11. Furnishing of Financial Statements; Tenant's Representations. In
order to induce Landlord to enter into this Lease, Tenant agrees that it shall
promptly furnish Landlord, from time to time, upon Landlord's written request,
with financial statements reflecting Tenant's current financial condition.
Tenant represents and warrants that all financial statements, records and
information furnished by Tenant to Landlord in connection with this Lease are
true, correct and complete in all respects. Notwithstanding anything in this
section of 36.11 to the contrary, Tenant shall only be required to provide
financial statements to Landlord if (i) Tenant is in default under the Lease, or
(ii) such financial statements are requested by a prospective lender or
purchaser of the Project or Building.

      36.12. Further Assurances. The parties agree to promptly sign all
documents reasonably requested to give effect to the provisions of this Lease.

      36.13. Prior Agreements; Amendments. This Lease and the schedules and
addenda attached, if any, form a part of this Lease together with the rules and
regulations set forth on Exhibit "E" attached hereto, and set forth all the
covenants, promises, assurances, agreements, representations, conditions,
warranties, statements, and understandings (Representations) between Landlord
and Tenant concerning the Premises and the Building and Project, and there are
no Representations, either oral or written, between them other than those in
this Lease.

This Lease supersedes and revokes all previous negotiations, arrangements,
letters of intent, offers to lease, lease proposals, brochures, representations,
and information conveyed, whether oral or in writing, between the parties hereto
or their respective representatives or any other person purporting to represent
Landlord or Tenant. Tenant acknowledges that it has not been induced to enter
into this Lease by any Representations not set forth in this Lease, and that it
has not relied on any such Representations. Tenant further acknowledges that no
such Representations shall be used in the interpretation or construction of this
Lease, and that Landlord shall have no liability for any consequences arising as
a result of any such Representations.

Except as otherwise provided herein, no subsequent alteration, amendment,
change, or addition to this Lease shall be binding upon Landlord or Tenant
unless it is in writing and signed by each party.

                                       24
<PAGE>

      36.14. Recording. Tenant shall not record this Lease without the prior
written consent of Landlord. Tenant, upon the request of Landlord, shall execute
and acknowledge a short form memorandum of this Lease for recording purposes.

      36.15. Severability. A final determination by a court of competent
jurisdiction that any provision of this Lease is invalid shall not affect the
validity of any other provision, and any provision so determined to be invalid
shall, to the extent possible, be construed to accomplish its intended effect.

      36.16. Successors and Assigns. This Lease shall apply to and bind the
heirs, personal representatives, and successors and assigns of the parties.

      36.17. Time of the Essence. Time is of the essence of this Lease.

      IN WITNESS WHEREOF, the parties hereto have executed this Lease as of the
date first set forth on Page 1.

LANDLORD:

GLENBOROUGH FUND V, LIMITED PARTNERSHIP,
a Delaware limited partnership

By:   GRTV, Inc.,
      a Delaware corporation
      Its General Partner

      By:  ____________________________
           Its ________________________

TENANT:

Sonus Networks, Inc.
a Delaware Corp.

By:   /s/ Harris Fishman
      ---------------------------------
      Its Chief Financial Officer

By:   /s/ [Illegible]
      ---------------------------------
      Its _____________________________

                                       25
<PAGE>

                           ADDENDUM TO LEASE BETWEEN
                    GLENBOROUGH FUND V, LIMITED PARTNERSHIP,
                a Delaware limited partnership ("Landlord"), and
                              SONUS NETWORKS, INC.,
                        a Delaware corporation ("Tenant")

                             DATED January 21, 1999

37.   TENANT IMPROVEMENTS

Section 37. adds to and amends the Lease as follows:

      a.    Landlord shall construct Tenant Improvements to the Premises in
            accordance with Exhibit D attached hereto and made a part hereof.

      b.    Landlord shall contribute a total maximum amount of $83,080.00
            ("Tenant Improvement Allowance") toward the cost of constructing
            such Tenant Improvements. Landlord shall pay the Tenant Improvement
            Allowance directly to any contractors and/or subcontractors
            performing the Tenant Improvements in the Premises on behalf of
            Landlord.

      c.    If the actual cost of completing the Tenant Improvements is less
            than the Tenant Improvement Allowance, then Landlord shall retain
            the difference and no credit shall be due Tenant. Notwithstanding
            the foregoing, however, Tenant shall have until December 31, 1999 to
            request payment of all or part of the Tenant Improvement Allowance.

      d.    If the cost of completing the Tenant Improvements exceeds the Tenant
            Improvement Allowance, any such excess shall be Tenant's
            responsibility and Tenant shall reimburse Landlord (as "Additional
            Rent") within twenty (20) days after Tenant's receipt of Landlord's
            invoice.

      e.    Notwithstanding anything herein to the contrary, Landlord and Tenant
            may agree in the future that Tenant shall construct all or a portion
            of the Tenant Improvements set forth in Exhibit D. In such event,
            Landlord shall pay the portion of the Tenant Improvement Allowance
            attributable to such Tenant Improvements constructed by Tenant
            directly to Tenant. Such payment will be made by Landlord within
            (30) days of Landlord's receipt of paid receipts for such work,
            together with final lien releases therefor.

38.   RIGHT OF FIRST OFFER

Section 38. adds to and amends the Lease as follows:

During the initial Term of the Lease, Landlord hereby grants to Tenant the right
to receive Landlord's first offer to lease any available space on the first
(1st) floor of 5 Carlisle Road or in the entire building located at 3 Carlisle
Road. The term "available space" means all such space, the lease term (including
renewal options) of which expires, and all such space vacated by any tenant. As
to any such available space, Landlord shall promptly deliver to Tenant Notice of
availability and an offer to Tenant to lease the space as part of the Premises
coterminously with the Term of this Lease at the then current market rental rate
(subject to adjustment in accordance with the terms of the Lease). Other
significant terms and conditions shall be included in the notice. Within fifteen
(15) days after receipt of Landlord's Notice, Tenant shall provide Landlord
Notice of its acceptance or rejection of the offer. If Tenant indicates by
Notice to Landlord of its agreement to lease the available space, the parties
shall immediately execute an amendment to this Lease stating the addition of the
space to the Premises. If Tenant does not accept the offer within the allotted
time, Tenant shall be deemed to have rejected the offer. With respect to any
rejection by Tenant, the right to receive an offer to lease shall be of no
further force or effect as to the space in question, provided that Landlord then
proceeds within six (6) months of Landlord's Notice to Tenant to lease such
available space to a third party on substantially similar terms as offered to
Tenant [ILLEGIBLE]
<PAGE>

This Right of First Offer is granted by Landlord to Sonus Networks, Inc., a
Delaware corporation (or to any entity which is duly assigned the Lease
hereunder after having purchased all or substantially all of the capital stock
of Tenant), and is personal as to such party(ies) and shall not be exercised or
assigned, voluntarily or involuntarily, by or to anyone other than such
party(ies). Any assignment of this Right of First Offer without Landlord's prior
written consent shall be void and, at Landlord's election, shall be a default on
the Lease.

39.   PARKING

Section 39. adds to and amends Section 2.12. of the Lease as follows:

Notwithstanding anything in Section 2.12. of the Lease to the contrary, subject
to Section 6.3. of the Lease, Landlord shall use reasonable efforts to increase
the parking ratio of the Building to a minimum of four (4) parking spaces per
thousand square feet of net rentable area of the Building. Such efforts may
include, but shall not be limited to, (i) exploring expanding the Building
parking by contacting the Town of Westford to seek authorization for additional
parking, (ii) re-lining the existing parking spaces and/or negotiating with
Sentry Insurance for a reduction in its current parking ratio. Any parking
spaces which are not allocated to a particular tenant or tenants shall be made
available on a first come, first served basis.

Landlord agrees to commence its efforts to obtain the above-referenced
additional parking promptly upon the execution of this Lease, and to diligently
pursue such efforts. Landlord shall be responsible for all costs and expenses
incurred in attempting to obtain the additional parking (collectively, the
"Parking Expenses"). The term "reasonable efforts" shall require Landlord to pay
all necessary Parking Expenses, but in no event shall Landlord be required to
spend in excess of $45,000.00 therefor. All Parking Expenses shall be included
in Operating Expenses for calendar year 1999, regardless of when such expenses
are incurred.

Upon obtaining additional parking, Tenant shall be entitled to the nonexclusive
use of a total of up to 166 parking spaces located at the Project at no charge.

40.   LANDLORD'S INDEMNIFICATION OBLIGATIONS

Section 40. adds to and amends Section 14.1. of the Lease as follows:

Notwithstanding anything in Section 14.1. of the lease to the contrary, and
subject to any sections of the Lease specifically limiting Landlord's liability,
Landlord shall indemnify and hold harmless Tenant from and against all losses,
claims, costs, damage, liability or expenses, including but not limited to
reasonable attorneys' fees, to the extent such losses, claims, costs, damage,
liability or expenses arise out of the negligence or willful misconduct of
Landlord, its agents, employees or contractors.

41.   PERMITTED TRANSFERS

This Section 41. adds to and amends Section 18.1. of the Lease as follows:

Tenant shall be permitted to assign or sublet the Premises, or any portion
thereof, without Landlord's consent, if such assignment or sublease is to any
corporation or other entity which (i) is a parent or subsidiary of Tenant, (ii)
controls, is controlled by, or is under common control with Tenant, (iii) is the
product of a merger with Tenant (provided that such entity maintains a net worth
at least equal to that of Tenant just prior to such merger), or (iv) is the
purchaser of substantially all of Tenant's assets and/or capital stock,
provided, however, that upon any such assignment or sublease, Tenant shall
promptly provide notice to Landlord as to the name of the assignee or sublessee,
as well as a copy of the document effectuating such assignment or sublet.

                                       2
<PAGE>

42.   DAMAGE AND DESTRUCTION

This Section 42. adds to and amends Section 16.2. of the Lease as follows:

Notwithstanding anything in Section 16.2. of the Lease to the contrary, in the
event that Landlord determines that repairs to the Premises or portion of the
Building necessary for Tenant's occupancy cannot be completed under applicable
laws and regulations within three hundred sixty (360) days of the date a permit
for such construction is issued by the governing authority, then Tenant may
elect, upon Notice to Landlord given within thirty (30) days after the date of
such fire or other casualty, to terminate the Lease. Such termination shall be
effective as of the date of damage or destruction.

      IN WITNESS WHEREOF, the parties have executed this Addendum to Lease as of
the date first above written.

LANDLORD:

GLENBOROUGH FUND V, Limited Partnership,
a Delaware limited partnership

By:    GRTV, Inc.,
       a Delaware corporation
       Its General Partner

       By:__________________________
          Its_______________________

TENANT:

SONUS NETWORKS, INC.,
a Delaware corporation

By: /s/ Harris Fishman
    ---------------------------
    Its Chief Financial Officer

By: /s/ [Illegible]
    ---------------------------
    Its
       ------------------------

                                       3
<PAGE>

                                   EXHIBIT C
                     BUILDING STANDARD TENANT IMPROVEMENTS

1.    Partitions

      Ceiling height partitions consisting of 3 5/8" 20-gauge metal studs at 16"
      O.C. with 5/8" gypsum board each side, taped and sanded to receive paint.
      Maximum: One (1) lineal foot per 16 square feet of area.

2.    Doors and Frames

      Tenant entry door shall be solid core with lockset and door closer. Tenant
      is allowed one (1) entry door per suite up to 15,000 square feet of area,
      and an additional entry door is allowed for suites greater than 15,000
      square feet.

      Tenant is allowed one (1) interior passage door for every 300 square feet
      of area. All interior passage doors to be given standard latchset
      hardware, and shall be 1 3/4" solid core oak veneer door 7'0" x 3'0" with
      metal welded frame.

3.    Ceiling

      Suspended Building Standard 24" x 24" grid configuration with Armstrong
      705 acoustical lay-in panels will be used throughout the premises.

4.    Lighting

      24" x 48" Building Standard four (4) tube 40 watt recessed fluorescent
      fixtures with lenses. One (1) fixture per 80 square feet of area.

      Any alterations or additions to said existing Building Standard pattern
      required to accommodate Tenant Improvements shall be at Tenant's sole
      expense.

      Elevator lobbies and common toilet facilities will have lighting selected
      by Landlord.

5.    Light Switches

      One (1) Building Standard single pole wall mounted light switch per 300
      square feet of area.

6.    Electrical Outlets

      One (1) Building Standard 120V Duplex electrical wall mounted outlet for
      each 175 square feet of area. Each outlet is 120 volts and is circuited
      with similar outlets on a 20 amp circuit.

7.    Lighted Exit Lights

      Building Standard exit signs are provided in the Premises to meet any
      requirements by code.

8.    Floor Covering and Base

      Carpeting in elevator lobbies and common corridors on all multiple-tenancy
      office floors in color and type as selected by Landlord; carpeting within
      office space as required and selected by Tenant from Building Standard
      selection of 28oz. loop carpeting.

      Maximum: Two Hundred(200) lineal feet of base per twelve hundred(1200)
      square feet of space.
<PAGE>

9.    Paint

      All wall surfaces except doors finished with one (1) coat primer sealer
      and one (1) coat flat latex paint in colors to be selected by Tenant from
      Building Standard selection, with not more than one (1) color to be in
      premises.

10.   Window Covering

      Building Standard vertical blinds on all exterior windows. No deletions or
      substitutions allowed.

11.   HVAC

      A complete year-round HVAC system engineered to handle normal office
      usage, with ducted supply air through ceiling diffusers, zoned and located
      in existing Building Standard pattern. Return air through exhaust vents.
      Any alterations or additions to said system required to accommodate Tenant
      Improvements shall be at Tenant's sole expense and must be done by
      Landlord-Approved Contractor.

12.   Tenant Signage

      One (1) Building Standard tenant identification sign at Tenant's entry
      door and inclusion in building lobby directory.
<PAGE>

                                 [PLAN OMITTED]

                           Westford Corporate Center

                         Building One - 5 Carlisle Road
                               SECOND FLOOR PLAN

                                      B-2
<PAGE>

Exhibit B

                              [AREA PLAN OMITTED]
<PAGE>

                                   Exhibit D

                            Work Letter and Drawing

1. Demolish approx. 146 linear feet of drywall partitioning, including removal
of five 3' x 7' doors.

2. Fix suspended acoustical ceiling where walls penetrated.

3. Remove carpet/tile and replace with ESD conductive tile, approx. 4300 square
feet.

4. Construct approx. 80 linear feet of new drywall partitioning, to underside of
acoustical ceiling. Cove base included.

5. Install approx. 128 square feet of clear, laminated glass in new wall.
Approx. 4 panes, 4' high by 8' long.

6. Install five new 3' x 7' and one 6' x 7' double solid core doors with hollow
metal frames and hardware.

7. Paint new walls, and existing walls affected by construction, as required.

8. Misc. mechanical: Adjust sprinkler heads to conform to new layout. Adjust
supply and return diffusers and move thermostats for even distribution. Adjust
general outlets, lighting fixtures and switches.

9. Install approx. 375 feet of cable tray, similar to what exists in the current
Sonus lab areas.

10. Electrical: Install 40 quad 20 amp ceiling drops distributed over the 2500
sq. ft. production floor area, including required distribution panels, etc.
Install 20 duplex outlets in new walls.

11. Security: Install card access control on one new door (at end of hallway
leading to the freight elevator) and on the freight elevator at the first floor.
We want it so that only Sonus employees can access the freight elevator from the
first floor. When you step out of the freight elevator on the second floor you
will be in the Sonus space (the shipping/receiving area).

12. Voice/data wiring for the area.
<PAGE>

NOTES: (A) - IF ELEVATOR (C) TRAVEL FROM FLOOR 1 TO FLOOR 2 CAN BE CARD-ACCESS
            CONTROLLED BY SONUS (DESIRED), THEN DOOR (A) NEEDS TO BE ADDED WITH
            CARD ACCESS. IF NOT, DOUBLE DOORS (B) NEED TO BE ADDED.

       (D)  ALL WALLS TO BE DEMOLISHED [as indicated in Floor Plan].

       (E)  ADD WALLS - POSSIBLE GLASS WINDOWS TO LET LIGHT IN.

       (F)  DOOR(S) AS REQUIRED FOR FIRE CODE.

       (G)  FLOORS TO BE ESD TILE THRUOUT ENCLOSED [ILLEGIBLE] AREA

                              [FLOOR PLAN OMITTED]
<PAGE>

                                   EXHIBIT E

                             RULES AND REGULATIONS

1.    The entrances, lobbies, passages, corridors, elevators, halls, courts,
      sidewalks, vestibules, and stairways shall not be encumbered or obstructed
      by Tenant, Tenant's agents, servants, employees, licensees or visitors or
      used by them for any purposes other than ingress or egress to and from the
      Premises.

2.    The moving in or out of all safes, freight, furniture, or bulky matter of
      any description shall take place during the hours which Landlord may
      determine from time to time. Landlord reserves the right to inspect all
      freight and bulky matter to be brought into the Building and to exclude
      from the Building all freight and bulky matter which violates any of these
      Rules and Regulations or the Lease of which these Rules and Regulations
      are a part.

3.    Tenant, or the employees, agents, servants, visitors or licensees of
      Tenant shall not at any time place, lease or discard any rubbish, paper,
      articles, or objects of any kind whatsoever outside the doors of the
      Premises or in the corridors or passageways of the Building. No animals or
      birds shall be brought or kept in or about the Building. Bicycles shall
      not be permitted in the Building.

4.    Tenant shall not place objects against glass partitions or doors or
      windows or adjacent to any common space which would be unsightly from the
      Building corridors or from the exterior of the Building and will promptly
      remove the same upon notice from Landlord.

5.    Tenant shall not make noises, cause disturbances, create vibrations, odors
      or noxious fumes or use or operate any electric or electrical devices or
      other devices that emit sound waves or are dangerous to other tenants and
      occupants of the Building or that would interfere with the operation of
      any device or equipment or radio or television broadcasting or reception
      from or within the Building or elsewhere, or with the operation of roads
      or highways in the vicinity of the Building, and shall not place or
      install any projections, antennae, aerials, or similar devices inside or
      outside of the Premises, without the prior written approval of Landlord.

6.    Tenant shall not: (a) use the Premises for lodging, manufacturing or for
      any immoral or illegal purposes; (b) use
<PAGE>

      the Premises to engage in the manufacture or sale of, or permit the use of
      spirituous, fermented, intoxicating or alcoholic beverages on the
      Premises; (c) use the Premises to engage in the manufacture or sale of, or
      permit the use of, any illegal drugs on the Premises.

7.    No awning or other projections shall be attached to the outside walls or
      windows. No curtains, blinds, shades, screens or signs other than those
      furnished by Landlord shall be attached to, hung in, or used in connection
      with any window or door of the Premises without prior written consent of
      Landlord.

8.    No signs, advertisement, object, notice or other lettering shall be
      exhibited, inscribed, painted or affixed on any part of the outside or
      inside of the Premises if visible from outside of the Premises. Interior
      signs on doors shall be painted or affixed for Tenant by Landlord or by
      sign painters first approved by Landlord at the expense of Tenant and
      shall be of a size, color and style acceptable to Landlord.

9.    Tenant shall not use the name of the Building or use pictures or
      illustrations of the Building in advertising or other publicity without
      prior written consent of Landlord. Landlord shall have the right to
      prohibit any advertising by Tenant which, in Landlord's reasonable
      opinion, tends to impair the reputation of the Building or its
      desirability for offices, and, upon written notice from Landlord, Tenant
      will refrain from or discontinue such advertising.

10.   Door keys for doors in the Premises will be furnished at the Commencement
      of the Lease by Landlord. Tenant shall not affix additional locks on doors
      and shall purchase duplicate keys only from Landlord and will provide to
      Landlord, prior to termination, the means of opening of safes, cabinets,
      or vaults to be left on the Premises after termination. In the event of
      the loss of any keys so furnished by Landlord, Tenant shall pay to
      Landlord the cost thereof.

11.   Tenant shall cooperate and participate in all security programs affecting
      the Building.

12.   Tenant assumes full responsibility for protecting its space from theft,
      robbery and pilferage, which includes keeping doors locked and other means
      of entry to the Premises closed and secured.

13.   Tenant shall not make any room-to-room canvass to solicit business from
      other tenants in the Building, and shall not exhibit, sell or offer to
      sell, use, rent or exchange any item or services in or from the Premises
      unless ordinarily embraced within Tenant's use of the Premises as
      specified in

                                       2
<PAGE>

      its Lease. Canvassing, soliciting and peddling in the Building are
      prohibited and Tenant shall cooperate to prevent the same. Peddlers,
      solicitors and beggars shall be reported to the Management Office.

14.   Tenant shall not waste electricity or water and agrees to cooperate fully
      with Landlord to assure the most effective operation of the Building's
      heating and air conditioning and shall refrain from attempting to adjust
      controls. Tenant shall keep corridor doors closed except when being used
      for access.

15.   The water and wash closets and other plumbing fixtures shall not be used
      for any purposes other than those for which they were constructed, and no
      sweepings, rubbish, rags, or other substances shall be thrown therein.

16.   Building employees shall not be required to perform, and shall not be
      requested by any tenant or occupant to perform, any work outside of their
      regular duties, unless under specific instructions from the office of the
      Managing Agent of the Building.

17.   Tenant may request heating and/or air conditioning during other periods in
      addition to normal working hours by submitting its request in writing to
      the office of the Managing Agent of the Building no later than 2:00 p.m.
      the preceding work day (Monday through Friday). The request shall clearly
      state the start and stop hours of the "off-hour" service. Tenant shall
      submit to the Building Manager a list of personnel authorized to make such
      request. When applicable, Tenant shall be charged for such operation in
      the form of additional rent.

18.   Tenant covenants and agrees that its use of the Premises shall not cause a
      discharge of sanitary (non-industrial) sewage which will result in a
      violation of the sewage discharge permit(s) for the Building. Discharges
      in excess of that amount, and any discharge of industrial sewage, shall
      only be permitted if Tenant, at its sole expense, shall have obtained all
      necessary permits and licenses therefor, including without limitation
      permits from state and local authorities having jurisdiction thereof.
      Tenant shall submit to Landlord on December 31 of each year of the Term of
      this Lease a statement, certified by an authorized officer of Tenant,
      which contains the following information: name of all chemicals, gases,
      and hazardous substances, used, generated, or stored on the Premises; type
      of substance (liquid, gas or granular); quantity used, stored or generated
      per year; method of disposal; permit number, if any, attributable to each
      substance, together with copies of all permits for such substance; and
      permit expiration date for each substance.

                                       3<PAGE>

                                                                    Exhibit 10.4

                  SERIES A PREFERRED STOCK PURCHASE AGREEMENT

      This Agreement dated as of November 18, 1997 is entered into by and among
Sonus Networks, Inc., a Delaware corporation (the "Company"), Rubin Gruber,
Michael G. Hluchyj and Kwok P. Wong (individually, a "Founder" and,
collectively, the "Founders"), and the persons and entities listed on Schedule I
attached hereto (individually, a "Purchaser" and, collectively, the
"Purchasers")

      In consideration of the mutual promises and covenants contained in this
Agreement, the parties hereto agree as follows:

      1. Authorization and Sale of Shares.

            1.1 Authorization. The Company has duly authorized the sale and
issuance, pursuant to the terms of this Agreement, of 7,100,000 shares of its
Series A Preferred Stock, $0.01 par value per share (the "Series A Preferred
Stock"), having the rights, restrictions, privileges and preferences set forth
in the Certificate of Designations attached hereto as Exhibit A (the
"Certificate of Designations"). The Company has adopted and filed the
Certificate of Designations with the Secretary of State of the State of
Delaware.

            1.2 Sale of Shares. Subject to the terms and conditions of this
Agreement the Company will issue and sell to each Purchaser, and each Purchaser
will purchase, for a purchase price of $1.00 per share, such number of shares of
Series A Preferred Stock as is set forth opposite such Purchaser's name on
Schedule I attached hereto. The shares of Series A Preferred Stock being sold
under this Agreement are referred to as the "Shares." The Company's agreement
with each of the Purchasers is a separate agreement, and the sale of Shares to
each of the Purchasers is a separate sale.

            1.3 Use of Proceeds. The Company will use the proceeds from the sale
of the Shares for working capital purposes.

      2. The Closing. The closing (the "Closing") of the sale and purchase of
the Shares under this Agreement shall take place at the offices of Hale and Dorr
LLP, 60 State Street, Boston, Massachusetts at 9:00 a.m. on the date of this
Agreement, or at such, other time, date and place as are mutually agreeable to
the Company and the Purchasers. The date of the Closing is hereinafter referred
to as the "Closing Date." At the Closing:

                  (a) the Company shall deliver to the Purchasers a certificate,
as of the most recent practicable date, as to the corporate good standing of the
Company issued by the Secretary of State of the State of Delaware;

                                     - 1 -
<PAGE>

                  (b) the Company shall deliver to the Purchasers the
Certificate of Incorporation of the Company, as amended and in effect as of the
Closing Date (including the Certificate of Designations), certified by the
Secretary of State of the State of Delaware;

                  (c) the Company shall deliver to the Purchasers a Certificate
of the Secretary of the Company attesting as to (i) the By-laws of the Company,
and (ii) resolutions of the Board of Directors of the Company authorizing and
approving all matters in connection with this Agreement and the transactions
contemplated hereby;

                  (d) Bingham Dana LLP, counsel for the Company, shall deliver
to the Purchasers an opinion, dated the Closing Date, in the form attached
hereto as Exhibit B;

                  (e) the Company, the Founders and the Purchasers shall execute
and deliver the Investor Rights Agreement in the form attached hereto as Exhibit
C (the "Investor Agreement");

                  (f) the Company; the Founders and the Purchasers shall execute
and deliver the Right of First Refusal and Co-Sale Agreement in the form
attached hereto as Exhibit D (the "Right of First Refusal Agreement");

                  (g) the Company shall deliver to each Purchaser a certificate
for the number of Shares being purchased by such Purchaser, registered in the
name of such Purchaser;

                  (h) each Purchaser shall pay to the Company the purchase price
for the Shares being purchased by such Purchaser, by wire transfer or certified
check; and

                  (i) the Company and the Purchasers shall execute and deliver a
Cross-Receipt.

      3. Representations of the Company. Subject to and except as disclosed by
the Company in the Disclosure Schedule attached hereto (the "Disclosure
Schedule"), the Company hereby represents and warrants to the Purchasers as
follows:

            3.1 Organization and Standing. The Company is a corporation duly
organized, validly existing and in good standing under the laws of the State of
Delaware and has full corporate power and authority to conduct its business as
presently conducted and as proposed to be conducted by it and to enter into and
perform this Agreement and to carry out the transactions contemplated by this
Agreement. The Company is duly qualified to do business as a foreign corporation

                                     - 2 -
<PAGE>

and is in good standing in the Commonwealth of Massachusetts and in any other
jurisdiction in which the failure to so qualify would have a material adverse
effect on the operations or financial condition of the Company. The Company has
furnished to special counsel to the Purchasers true and complete copies of its
Certificate of Incorporation and By-laws, each as amended to date and presently
in effect.

            3.2 Capitalization. The authorized capital stock of the Company
(immediately prior to the Closing) consists of (i) 15,000,000 shares of common
stock, $0.001 par value per share (the "Common Stock"), of which 3,282,093
shares are issued and outstanding, 2,467,907 shares have been reserved for
issuance pursuant to the Company's 1997 Stock Incentive Plan and 7,100,000
shares have been reserved for issuance upon the conversion of the Shares, and
(b) 10,000,000 shares of preferred stock, $0.01 par value per share (of which
7,100,000 shares have been designated as Series A Preferred Stock), none of
which are issued or outstanding. At the Closing, the Common Stock and the Series
A Preferred Stock will have the voting powers, designations, preferences, rights
and qualifications, and limitations or restrictions set forth in the Certificate
of Incorporation, as amended by the Certificate of Designations. All of the
issued and outstanding shares of Common Stock have been duly authorized and
validly issued and are fully paid and nonassessable. Except as contemplated by
this Agreement, (i) no subscription, warrant, option, convertible security or
other right (contingent or otherwise) to purchase or acquire any shares of
capital stock of the Company is authorized or outstanding, (ii) the Company has
no obligation (contingent or otherwise) to issue any subscription, warrant,
option, convertible security or other such right or to issue or distribute to
holders of any shares of its capital stock any evidences of indebtedness or
assets of the Company, and (iii) the Company has no obligation (contingent or
otherwise) to purchase, redeem or otherwise acquire any shares of its capital
stock or any interest therein or to pay any dividend or make any other
distribution in respect thereof. All of the issued and outstanding shares of
capital stock of the Company have been offered, issued and sold by the Company
in compliance with applicable Federal and state securities laws.

            3.3 Subsidiaries, Etc. The Company has no subsidiaries and does not
own or control, directly or indirectly, any shares of capital stock of any other
corporation or any interest in any partnership, joint venture or other
non-corporate business enterprise.

            3.4 Stockholder List and Agreements. Section 3.4 of the Disclosure
Schedule sets forth a true and complete list of the stockholders of the Company,
showing the number of shares of Common Stock or other securities of the Company
held by each stockholder immediately prior to the execution of this Agreement
and the consideration paid to the Company therefor. Except as listed in Section
3.4 of the Disclosure Schedule or as contemplated by this Agreement, there are
no agreements, written or oral, between the Company and any holder of its
capital stock, or, to the

                                     - 3 -
<PAGE>

best of the Company's knowledge, among any holders of its capital stock,
relating to the acquisition (including without limitation rights of first
refusal or pre-emptive rights), disposition, registration under the Securities
Act of 1933, as amended (the "Securities Act"), or voting of the capital stock
of the Company.

            3.5 Issuance of Shares. The issuance, sale and delivery of the
Shares in accordance with this Agreement, and the issuance and delivery of the
shares of Common Stock issuable upon conversion of the Shares, have been duly
authorized by all necessary corporate action on the part of the Company, and all
such shares have been duly reserved for issuance. The Shares when so issued,
sold and delivered against payment therefor in accordance with the provisions of
this Agreement, and the shares of Common Stock issuable upon conversion of the
Shares, when issued upon such conversion, will be duly and validly issued, fully
paid and non-assessable.

            3.6 Authority for Agreement. The execution, delivery and performance
by the Company of this Agreement and all other agreements required to be
executed by the Company at the Closing pursuant to Section 2 (the "Ancillary
Agreements"), and the consummation by the Company of the transactions
contemplated hereby and thereby, have been duly authorized by all necessary
corporate action. This Agreement and the Ancillary Agreements have been duly
executed and delivered by the Company and constitute valid and binding
obligations of the Company enforceable in accordance with their respective
terms. The execution of and performance of the transactions contemplated by this
Agreement and the Ancillary Agreements and compliance with their provisions by
the Company will not violate any provision of applicable law and will not
conflict with or result in any breach of any of the terms, conditions or
provisions of, or constitute a default under, or require a consent or waiver
under, its Certificate of Incorporation or By-laws (each as amended to date) or
any material indenture, lease, agreement or other instrument to which the
Company is a party or by which it or any of its properties is bound, or any
decree, judgment, order, statute, rule or regulation applicable to the Company
which would have a material adverse effect on the business, properties or
results of operations of the Company (a "Material Adverse Effect").

            3.7 Governmental Consents. No consent, approval, order or
authorization of, or registration, qualification, designation, declaration or
filing with, any governmental authority is required on the part of the Company
in connection with the execution and delivery of this Agreement, the offer,
issuance, sale and delivery of the Shares, or the other transactions to be
consummated at the Closing, as contemplated by this Agreement, except such
filings as shall have been made prior to and shall be effective on and as of the
Closing. Based on the representations made by the Purchasers in Section 5 of
this Agreement, the offer and sale of the Shares to the Purchasers will be
exempt from the registration requirements of applicable Federal and state
securities laws.

                                     - 4 -
<PAGE>

            3.8 Litigation. Except as set forth in the Disclosure Schedule,
there is no action, suit or proceeding, or governmental inquiry or
investigation, pending, or, to the best of the Company's knowledge, any basis
therefor or threat thereof, against the Company or any of the Founders, which
questions the validity of this Agreement or the right of the Company or the
Founders to enter into it, or which might result, either individually or in the
aggregate, in any material adverse change in the business, assets or condition,
financial or otherwise, of the Company, nor is there any litigation pending, or,
to the best of the Company's knowledge, any basis therefor or threat thereof,
against the Company or the Founders by reason of the past employment
relationships of the Founders, the proposed activities of the Company, or
negotiations by the Company and/or the Founders with possible investors in the
Company.

            3.9 Financial Statements. The Company has not prepared and does not
otherwise have available any financial statements.

            3.10 Absence of Liabilities. Except as set forth in Section 3.10 of
the Disclosure Schedule, the Company does not have any liabilities of any type,
whether absolute or contingent, which in the aggregate exceed $1,000.

            3.11 Taxes. The Company has not been obligated to file any Federal,
state, county, local and foreign tax returns. Neither the Company nor any of its
stockholders has ever filed (a) an election pursuant to Section 1362 of the
Internal Revenue Code of 1986, as amended (the "Code"), that the Company be
taxed as an S Corporation, or (b) consent pursuant to Section 341(f) of the Code
relating to collapsible corporations.

            3.12 Property and Assets. The Company does not own any material
properties or assets.

            3.13 Intellectual Property.

                  (a) To the best of the Company's knowledge, no third party has
claimed or has reason to claim that any person employed by or affiliated with
the Company, in connection with his or her employment by or affiliation with the
Company, (i) has violated or is violating any of the terms or conditions of his
employment, non-competition or non-disclosure agreement with such third party,
(ii) has disclosed or is disclosing or has utilized or is utilizing any trade
secret or proprietary information or documentation of such third party or (iii)
has interfered or is interfering in the employment relationship between such
third party and any of its present or former employees. No third party has
requested information from the Company which suggests that such a claim might be
contemplated. To the best of the Company's knowledge, no person employed by or
affiliated with the Company has employed or proposes to employ any trade secret
or any information or

                                     - 5 -
<PAGE>

documentation proprietary to any former employer, and to the best of the
Company's knowledge, no person employed by or affiliated with the Company has
violated any confidential relationship which such person may have had with any
third party, in connection with the development, manufacture or sale or any
product or proposed product or the development or sale of any service or
proposed service of the Company, and the Company has no reason to believe there
will be any such employment or violation. To the best of the Company's
knowledge, none of the execution or delivery of this Agreement, or the carrying
on of business of the Company as officers, employees or agents by any officer,
director or key employee of the Company, or the conduct or proposed conduct of
the business of the Company, will conflict with or result in a breach of the
terms, conditions or provisions of or constitute a default under any contract,
covenant or instrument under which any such person is obligated which would have
a Material Adverse Effect.

                  (b) Set forth in Section 3.13 of the Disclosure Schedule is a
list of all domestic and foreign patents, patent rights, patent applications,
trademarks, trademark applications, service marks, service mark applications,
trade names and copyrights, and all applications for such which are currently in
the process of being prepared, owned by or registered in the name of the
Company, or of which the Company is a licensor or licensee or in which the
Company has any right, and in each case a brief description of the nature of
such right. Except as set forth in Section 3.13(b) of the Disclosure Schedule,
the Company owns or possesses adequate licenses or other rights to use all
patents, patent applications, trademarks, trademark applications, service marks,
service mark applications, trade names, copyrights, manufacturing processes,
formulae, trade secrets, customer lists and know-how (collectively,
"Intellectual Property") necessary for the conduct of its business as conducted
and as proposed to be conducted. Except as otherwise provided in the Disclosure
Schedule, no claim is pending or, to the best of the Company's knowledge,
threatened to the effect that the operations of the Company infringe upon or
conflict with the asserted rights of any other person under any Intellectual
Property, and, to the best of the Company's knowledge, there is no basis for any
such claim (whether or not pending or threatened). No claim is pending or, to
the knowledge of the Company, threatened to the effect that any such
Intellectual Property owned or licensed by the Company, or which the Company
otherwise has the right to use, is invalid or unenforceable by the Company, and,
to the best of the Company's knowledge, there is no basis for any such claim
(whether or not pending or threatened). To the best of the Company's knowledge,
all technical information developed by and belonging to the Company which has
not been patented has been kept confidential. The Company has not granted or
assigned to any other person or entity any right to manufacture, have
manufactured, assemble or sell the products or proposed products or to provide
the services or proposed services of the Company.

            3.14 Material Contracts and Obligations. Except as contemplated by
this Agreement or as listed in Section 3.14 of the Disclosure Schedule, the
Company

                                     - 6 -
<PAGE>

is not a party to any material agreement or commitment of any nature, including
without limitation (a) any agreement which requires future expenditures by the
Company in excess of $20,000, (b) any employment or consulting agreement,
employee benefit, bonus, pension, profit-sharing, stock option, stock purchase
or similar plan or arrangement, or distributor or sales representative
agreement, (c) any agreement with any stockholder, officer or director of the
Company, or any "affiliate" or "associate" of such persons (as such terms are
defined in the rules and regulations promulgated under the Securities Act),
including without limitation any agreement or other arrangement providing for
the furnishing of services by, rental of real or personal property from, or
otherwise requiring payments to, any such person or entity or (d) any agreement
relating to the intellectual property rights of the Company.

            3.15 Compliance. The Company has, to its knowledge, in all material
respects, complied with all laws, regulations and orders applicable to its
present and proposed business and has all material permits and governmental
licenses required thereby. There is no term or provision of any mortgage,
indenture, contract, agreement or instrument to which the Company is a party or
by which it is bound, or, to the best of the Company's knowledge, of any
provision of any state or Federal judgment, decree, order, statute, rule or
regulation applicable to or binding upon the Company, which materially adversely
affects or, so far as the Company may now foresee, in the future is reasonably
likely to materially adversely affect, the business, assets or condition,
financial or otherwise, of the Company. To the best of the Company's knowledge,
neither the Founders nor any other employee of the Company is in violation of
any term of any contract or covenant (either with the Company or with another
entity) relating to employment, patents, proprietary information disclosure,
non-competition or non-solicitation.

            3.16 Employees and Founders.

                  (a) The Founders and the other holders of Common Stock have
executed and delivered to the Company a Stock Repurchase Agreement in
substantially the form attached hereto as Exhibit E and Exhibit F, respectively,
and all of such agreements are in full force and effect.

                  (b) Each employee of the Company (including the Founders) has
executed and delivered to the Company a Noncompetition and Confidentiality
Agreement covering a period of one year following the termination of such
employee's employment with the Company, in substantially the form attached
hereto as Exhibit G, and all of such agreements are in full force and effect.

                  (c) None of the employees of the Company is represented by any
labor union, and there is no labor strike or other labor trouble pending with

                                     - 7 -
<PAGE>

respect to the Company (including, without limitation, any organizational drive)
or, to the best of the Company's knowledge, threatened.

            3.17 ERISA. The Company does not have or otherwise contribute to or
participate in any employee benefit plan subject to the Employee Retirement
Income Security Act of 1974.

            3.18 Books and Records. The minute books of the Company contain
complete and accurate records of all meetings and other corporate actions of its
stockholders and its Board of Directors and committees thereof. The stock ledger
of the Company is complete and reflects all issuances, transfers, repurchases
and cancellations of shares of capital stock of the Company.

            3.19 Board of Directors. Effective upon the Closing, the Board of
Directors shall be comprised of up to five members, and consist of (a) the Chief
Executive Officer of the Company, (b) one additional designee of the Company,
(c) one director designated by North Bridge Venture Partners, (d) one director
designed by Matrix Partners, and (e) one outside Director designated by mutual
agreement of the other four directors.

            3.20 U.S. Real Property Holding Corporation. The Company is not now
and has never been a "United States Real Property Holding Corporation" as
defined in Section 897(c)(2) of the Code and Section 1.897-2(b) of the
Regulations promulgated by the Internal Revenue Service.

            3.21 Disclosures. Neither this Agreement nor any Schedule or Exhibit
hereto, nor any certificate or instrument furnished to the Purchasers at the
Closing or as required by the terms of this Agreement, when read together,
contains or will contain any untrue statement of a material fact or omits or
will omit to state a material fact necessary in order to make the statements
contained herein or therein, in light of the circumstances under which they were
made, not misleading.

      4. Representations of Founders. Each Founder represents and warrants to
the Purchasers as follows:

            4.1 Conflicting Agreements. Except as set forth in the Disclosure
Schedule, such Founder is not, as a result of the nature of the business
conducted or proposed to be conducted by the Company, in violation of (i) any
fiduciary or confidential relationship, (ii) any term of any contract or
covenant (either with the Company or with another entity) relating to
employment, patents, proprietary information disclosure, non-competition or
non-solicitation, or (iii) any other contract or agreement, or any judgment,
decree or order of any court or administrative agency relating to or affecting
the right of such Founder to be employed by the Company, which violation would
have a Material Adverse Effect.

                                     - 8 -
<PAGE>

            4.2 Litigation. Except as set forth in the Disclosure Schedule,
there is no action, suit or proceeding, or governmental inquiry or
investigation, pending or, to the knowledge of such Founder, threatened against
such Founder.

            4.3 Stockholder Agreements. Except as contemplated by or disclosed
in this Agreement, such Founder is not a party to any agreements, written or
oral, relating to the acquisition, disposition, registration under the
Securities Act, or voting of the capital stock of the Company.

            4.4 Representations. To the best knowledge of such Founder, the
Representations of the Company in Sections 3.8 (Litigation) and 3.13
(Intellectual Property) are true and correct.

            4.5 Disclosure. To the knowledge of such Founder, neither this
Agreement nor any Schedule or Exhibit hereto, nor any certificate or instrument
furnished to the Purchasers at the Closing or as required by the terms of this
Agreement, when read together, contains or will contain any untrue statement of
a material fact or omits or will omit to state a material fact necessary in
order to make the statements contained herein or therein, in light of the
circumstances under which they were made, not misleading.

      5. Representations of the Purchasers. Each Purchaser represents and
warrants to the Company as follows:

            5.1 Investment. Such Purchaser is acquiring the Shares, and the
shares of Common Stock into which the Shares may be converted, for its or his
own account for investment and not with a view to, or for sale in connection
with, any distribution thereof, nor with any present intention of distributing
or selling the same; and such Purchaser has no present or contemplated
agreement, undertaking, arrangement, obligation, indebtedness or commitment
providing for the disposition thereof. Such Purchaser acknowledges that the
Shares are restricted securities as defined under the Securities Act and shall
bear the legends set forth in Section 7.3 hereof.

            5.2 Authority. Such Purchaser has full power and authority to enter
into and to perform this Agreement in accordance with its terms. Such Purchaser
represents that it has not been organized, reorganized or recapitalized
specifically for the purpose of investing in the Company. This Agreement and the
Ancillary Agreement to be executed by such Purchaser have been duly executed and
delivered by such Purchaser and constitute valid and binding obligations of such
Purchaser enforceable in accordance with their respective terms. The execution
of and performance of the transactions contemplated by this Agreement and the
Ancillary Agreements to be executed by such Purchaser and compliance with their
provisions by such Purchaser will not violate any provision of law and will not
conflict with or

                                     - 9 -
<PAGE>

result in any breach of any of the terms, conditions or provisions of, or
constitute a default under, or require a consent or waiver under, its
organizational documents (each as amended to date) or any indenture, lease,
agreement or other instrument to which the Purchaser is a party or by which it
or any of its properties is bound, or any decree, judgment, order, statute, rule
or regulation applicable to such Purchaser.

            5.3 Experience. Such Purchaser has carefully reviewed the
representations concerning the Company contained in this Agreement and has made
detailed inquiry concerning the Company, its business and its personnel; the
officers of the Company have made available to such Purchaser any and all
written information which it has requested and have answered to such Purchaser's
satisfaction all inquiries made by such Purchaser; and such Purchaser has
sufficient knowledge and experience in investing in companies similar to the
Company so as to be able to evaluate the risks and merits of its investment in
the Company and is able financially to bear the risks thereof, including a
complete loss of its investment. Such Purchaser understands that an investment
in the Company involves a high degree of risk in view of the fact that the
Company is a start-up enterprise with no operating history, and there may never
be an established market for the Company's capital stock.

            5.4 Status. Such Purchaser is an "accredited Investor" as that term
is defined in Rule 501 of Regulation D promulgated under the Securities Act.

      6. Covenants of the Company.

            6.1 Inspection. The Company shall permit each Purchaser, or any
authorized representative thereof, to visit and inspect the properties of the
Company, including its corporate and financial records, and to discuss its
business and finances with officers of the Company, during normal business hours
following reasonable notice and as often as may be reasonably requested, without
interruption of the business of the Company and subject to the confidentiality
obligations of Section 8.2 hereof.

            6.2 Financial Statements and Other Information.

                  (a) So long as a Purchaser (or any of its affiliates) holds at
least 355,000 shares of Series A Preferred Stock, the Company shall deliver to
such Purchaser:

                        (i) within 90 days after the end of each fiscal year of
the Company, an audited balance sheet of the Company as at the end of such year,
and audited statements of income and of cash flows of the Company for such year,
certified by certified public accountants of established national reputation
selected by

                                     - 10 -
<PAGE>

the Company, and prepared in accordance with generally accepted accounting
principles; and

                        (ii) within 45 days after the end of each fiscal quarter
of the Company, an unaudited balance sheet of the Company as at the end of such
quarter, and unaudited statements of income and of cash flows of the Company for
such fiscal quarter and for the current fiscal year to the end of such fiscal
quarter.

                  (b) So long as a Purchaser (or any of its affiliates) holds at
least 355,000 shares of Series A Preferred Stock (as adjusted for stock splits,
stock dividends, recapitalizations and similar events), the Company shall
deliver to such Purchaser:

                        (i) within 30 days after the end of each month, an
unaudited balance sheet of the Company as at the end of such month and unaudited
statements of income and of cash flows of the Company for such month and for the
current fiscal year to the end of such month, setting forth in comparative form
the Company's projected financial statements for the corresponding periods for
the current fiscal year;

                        (ii) as soon as available, but in any event within 30
days after commencement of each new fiscal year, a budget, consisting of a
business plan and projected financial statements for such fiscal year; and

                        (iii) with reasonable promptness, such other notices,
information and data with respect to the Company as the Company delivers to the
holders of its Common Stock, and such other information and data as such
Purchaser may from time to time reasonably request.

                  (c) The foregoing financial statements shall be prepared on a
consolidated basis if the Company then has any subsidiaries. The financial
statements delivered pursuant to clause (ii) of paragraph (a) and clause (i) of
paragraph (b) shall be accompanied by a certificate of the chief financial
officer of the Company stating that such statements have been prepared in
accordance with generally accepted accounting principles consistently applied
(except as noted) and fairly present the financial condition and results of
operations of the Company at the date thereof and for the periods covered
thereby.

            6.3 Material Changes and Litigation. The Company shall promptly
notify the Purchasers of any material adverse change in the business, assets or
condition, financial or otherwise, of the Company and of any litigation or
governmental proceeding or investigation brought or, to the best of the
Company's knowledge, threatened against the Company, or against the Founders or
an officer, director, key employee or principal stockholder of the Company
materially adversely

                                     - 11 -
<PAGE>

affecting or which, if adversely determined, would materially adversely affect
its business, prospects, assets or condition, financial or otherwise.

            6.4 Insurance.

                  (a) The Company shall procure, within a reasonable period of
time following the Closing, and shall maintain for a period of at least three
years, term life insurance upon the lives of each of the Founders, in the amount
of $1,000,000, with the proceeds payable to the Company.

                  (b) The Company shall procure, promptly following the Closing,
and shall maintain in effect, policies of workers' compensation insurance and of
insurance with respect to its properties and business of the kinds and in the
amounts not less than is customarily obtained by corporations engaged in the
same or similar business and similarly situated, including, without limitation,
insurance against loss, damage, fire, theft, public liability and other risks.

            6.5 Employee Agreements. The Company shall require all employees
hereafter employed or engaged by the Company who are at or above the director
level or other key employees to enter into a Noncompetition and Confidentiality
Agreement covering a period of one year following the termination of such
employee's employment with the Company, substantially in the form attached
hereto as Exhibit G or in such other form as may be approved by the Board of
Directors. The Company shall require all employees not covered by the foregoing
sentence to enter into a Confidentiality Agreement substantially in the form
attached hereto as Exhibit H or in such other form as may be approved by the
Board of Directors.

            6.6 Related Party Transactions. The Company shall not enter into
any agreement with any stockholder, officer or director of the Company, or any
"affiliate" or "associate" of such persons (as such terms are defined in the
rules and regulations promulgated under the Securities Act), including without
limitation any agreement or other arrangement providing for the furnishing of
services by, rental of real or personal property from, or otherwise requiring
payments to, any such person or entity, without the consent of at least a
majority of the members of the Company's Board of Directors having no interest
in such agreement or arrangement.

            6.7 Directors.

                  (a) The Company shall use reasonable efforts to cause the
election to the Board of Directors, as soon as practicable following the
Closing, of one independent director mutually agreeable to the other directors,
as set forth in Section 3.19.

                                     - 12 -
<PAGE>

                  (b) The Company shall promptly reimburse in full each director
of the Company who is not an employee of the Company and who was elected as a
director solely by the holders of the Series A Preferred Stock for all of his
reasonable out-of-pocket expenses incurred in attending each meeting of the
Board of Directors of the Company or any committee thereof.

            6.8 Option Shares and Restricted Stock. The Company has reserved an
aggregate of 2,467,907 shares of Common Stock for issuance to employees and
consultants of the Company pursuant to the 1997 Stock Incentive Plan of the
Company.

                  (a) Unless otherwise agreed by the Board of Directors, all
options granted under the 1997 Stock Incentive Plan shall become exercisable at
the rate of 20% on the first anniversary of grant and 1.6667% per month
thereafter over the subsequent four years so long as the optionee continues to
be an employee or consultant of the Company, subject to acceleration by one year
of the unvested portion of such options in the event of (i) as to all optionees,
an Acquisition Event (as defined in the standard form of stock option agreements
for the grant of options under such Plan), and (ii) in the case of the Founders
only, also in the event of the death or disability of a Founder.

                  (b) Restricted stock awards under the 1997 Stock Option Plan
shall be issued pursuant to a Stock Repurchase Agreement in the form of Exhibit
F attached hereto, or such other form as may be approved by the Board of
Directors of the Company.

            6.9 Reservation of Common Stock. The Company shall reserve and
maintain a sufficient number of shares of Common Stock for issuance upon
conversion of all of the outstanding Shares.

            6.10 Termination of Covenants. The covenants of the Company
contained in Sections 6.1 through 6.9 shall terminate, and be of no further
force or effect, upon the closing of the Company's first offering of Common
Stock, resulting in net proceeds to the Company of at least $10,000,000, and at
a price per share of at least $5.00 (as adjusted for stock splits, stock
dividends, recapitalizations and similar events) or, at such time as the
Purchasers (together with any affiliated entities to whom Shares have been
transferred) own less than an aggregate of 1,775,000 shares of Series A
Preferred Stock (as adjusted for stock splits, stock dividends,
recapitalizations and similar events), unless the Company has, prior to such
time, failed to redeem shares of Series A Preferred Stock when such redemption
was due in accordance with Section 6 of Article III of the Company's Certificate
of Incorporation, which failure continues.

                                     - 13 -
<PAGE>

            6.11 Qualified Small Business Stock. The Company shall submit to its
stockholders (including the Purchasers) and to the Internal Revenue Service any
reports that may be required under Section 1202(d)(1)(C) of the Code and the
Regulations promulgated thereunder. In addition, within ten days after a
Purchaser's written request therefor, the Company shall deliver to such
Purchaser a written statement indicating whether such Purchaser's interest in
the Company constitutes "qualified small business stock" as defined in Section
1202(c) of the Code.

      7. Transfer of Shares.

            7.1 Restricted Shares. "Restricted Shares" means (i) the Shares,
(ii) the shares of Common Stock issued or issuable upon conversion of the
Shares, (iii) any shares of capital stock of the Company acquired by a Purchaser
pursuant to the Investor Agreement or the Right of First Refusal Agreement, and
(iv) any other shares of capital stock of the Company issued in respect of such
shares (as a result of stock splits, stock dividends, reclassifications,
recapitalizations, or similar events); provided, however, that shares of Common
Stock which are Restricted Shares shall cease to be Restricted Shares (i) upon
any sale pursuant to a registration statement under the Securities Act, or under
Section 4(1) of the Securities Act or Rule 144 under the Securities Act, or (ii)
at such time as they become eligible for sale under Rule 144(k) under the
Securities Act.

            7.2 Requirements for Transfer.

                  (a) Restricted Shares shall not be sold or transferred unless
(1) either (i) they first shall have been registered under the Securities Act,
or (ii) the Company first shall have been furnished with an opinion of legal
counsel, reasonably satisfactory to the Company, to the effect that such sale or
transfer is exempt from the registration requirements of the Securities Act and
(2) such actions are in compliance with applicable state securities laws.

                  (b) Notwithstanding the foregoing, no registration or opinion
of counsel shall be required for (i) a transfer by a Purchaser which is a
partnership to a partner of such partnership or a retired partner of such
partnership who retires after the date hereof, or to the estate of any such
partner or retired partner, if the transferee agrees in writing to be subject to
the terms of this Section 7 to the same extent as if he were an original
Purchaser hereunder, or (ii) a transfer made in accordance with Rule 144 under
the Securities Act.

            7.3 Legend. Each certificate representing Restricted Shares shall
bear a legend substantially in the following form:

      "The shares represented by this certificate have not been registered under
      the Securities Act of 1933, as amended, and may not be offered, sold or
      otherwise

                                     - 14 -
<PAGE>

      transferred, pledged or hypothecated unless and until such shares are
      registered under such Act or an opinion of counsel satisfactory to the
      Company is obtained to the effect that such registration is not required."

      The foregoing legend shall be removed from the certificates representing
any Restricted Shares, at the request of the holder thereof, at such time as
they become eligible for resale pursuant to Rule 144(k) under the Securities
Act.

            7.4 Rule 144A Information. The Company shall, at all times during
which it is neither subject to the reporting requirements of Section 13 or 15(d)
of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), nor
exempt from reporting pursuant to Rule 12g3-2(b) under the Exchange Act, upon
the written request of a Purchaser, provide in writing to such Purchaser, and to
any prospective transferee of any Restricted Shares of such Purchaser, the
information concerning the Company described in Rule 144A(d)(4) under the
Securities Act ("Rule 144A Information"). The Company also shall, upon the
written request of a Purchaser, cooperate with and assist such Purchaser or any
member of the National Association of Securities Dealers, Inc. PORTAL system in
applying to designate and thereafter maintain the eligibility of the Restricted
Shares for trading through PORTAL. The Company's obligations under this Section
7.4 shall at all times be contingent upon receipt from the prospective
transferee of Restricted Shares of a written agreement to take all reasonable
precautions to safeguard the Rule 144A Information from disclosure to anyone
other than persons who will assist such transferee in evaluating the purchase of
any Restricted Shares and to use such Rule 144A Information only for such
evaluation purposes.

      8. Miscellaneous.

            8.1 Successors and Assigns. This Agreement, and the rights and
obligations of a Purchaser hereunder, may be assigned by such Purchaser to any
person or entity to which at least 355,000 Shares, as adjusted for stock splits,
stock dividends, recapitalizations and similar events (or 100% of the Shares
originally purchased hereunder by such Purchaser, if less than 355,000 Shares),
are transferred by such Purchaser, and such transferee shall be deemed a
"Purchaser" for purposes of this Agreement; provided that the transferee
provides written notice of such assignment to the Company and agrees to be bound
by the terms and conditions set forth herein.

            8.2 Confidentiality. The Purchasers agree that they will keep
confidential and will not disclose or divulge any confidential, proprietary or
secret information which they may obtain from the Company pursuant to financial
statements, reports and other materials submitted by the Company to the
Purchasers pursuant to this Agreement, or pursuant to visitation or inspection
rights granted hereunder, unless such information is known, or until such
information becomes

                                     - 15 -
<PAGE>

known, to the public; provided, however, that a Purchaser may disclose such
information (i) to its attorneys, accountants, consultants, and other
professionals to the extent necessary to obtain their services in connection
with its investment in the Company, (ii) to any prospective purchaser of any
Shares from such Purchaser as long as such prospective purchaser agrees in
writing to be bound by the provisions of this Section, or (iii) to any affiliate
of such Purchaser or to a partner, shareholder or subsidiary of such Purchaser;
subject to the agreement of such party to keep such information confidential as
set forth herein.

            8.3 Survival of Representations and Warranties. All agreements,
representations and warranties contained herein shall survive the execution and
delivery of this Agreement and the closing of the transactions contemplated
hereby.

            8.4 Expenses. The Company shall pay, at the Closing, the reasonable
costs and expenses of Hale and Dorr LLP, counsel to the Purchasers, not to
exceed $15,000, in connection with the preparation of this Agreement and the
other agreements and documents contemplated hereby and the closing of the
transactions contemplated hereby.

            8.5 Notices. All notices, requests, consents, and other
communications under this Agreement shall be in writing and shall be delivered
by hand, sent via a reputable nationwide overnight courier service or mailed by
first class certified or registered mail, return receipt requested, postage
prepaid:

      If to the Company, at Sonus Networks, Inc., 5 Carlisle Road, Westford, MA
01886, Attn: President, or at such other address or addresses as may have been
furnished in writing by the Company to the Purchasers, with a copy to Bingham
Dana LLP, 150 Federal Street, Boston, MA 02110, Attn: David L. Engel, Esq.

      If to a Purchaser, at its address as set forth on Schedule I attached
hereto, or at such other address or addresses as may have been furnished to the
Company in writing by such Purchaser, with a copy to Hale and Dorr LLP, 60 State
Street, Boston, MA 02109, Attn: John M. Westcott, Jr., Esq.

      If to a Founder, at his address as set forth on Schedule II attached
hereto, or at such other address or addresses as may have been furnished in
writing by such Founder to the Company and the Purchasers.

      Notices provided in accordance with this Section 8.5 shall be deemed
delivered upon personal delivery, one business day after being sent via a
reputable nationwide overnight courier service, or five business days after
deposit in the mail.

            8.6 Brokers. The Company, the Founders and the Purchasers each (i)
represents and warrants to the other parties hereto that he, she or it has
retained

                                     - 16 -
<PAGE>

no finder or broker in connection with the transactions contemplated by this
Agreement, and (ii) will indemnify and save the other parties harmless from and
against any and all claims, liabilities or obligations with respect to brokerage
or finders' fees or commissions in connection with the transactions contemplated
by this Agreement asserted by any person on the basis of any agreement,
statement or representation alleged to have been made by such indemnifying
party.

            8.7 Entire Agreement. This Agreement and the Ancillary Agreements
embody the entire agreement and understanding between the parties hereto with
respect to the subject matter hereof and supersedes all prior agreements and
understandings relating to such subject matter.

            8.8 Amendments and Waivers. Except as otherwise expressly set forth
in this Agreement, any term of this Agreement may be amended and the observance
of any term of this Agreement may be waived (either generally or in a particular
instance and either retroactively or prospectively), with the written consent of
the Company and the holders of at least 66 2/3% of the shares of Common Stock
issued or issuable upon conversion of the Shares, provided, however, that no
consent shall be required in order to add additional Purchasers pursuant to
Section 1.2(b) hereof, or to revise Schedule I in connection therewith. Any
amendment or waiver effected in accordance with this Section 8.8 shall be
binding upon each holder of any Shares (including shares of Common Stock into
which such Shares have been converted), each future holder of all such
securities and the Company. No amendment shall increase any obligation of a
Founder hereunder without the express written consent of such Founder. No
waivers of or exceptions to any term, condition or provision of this Agreement,
in any one or more instances, shall be deemed to be, or construed as, a further
or continuing waiver of any such term, condition or provision.

            8.9 Counterparts. This Agreement may be executed in one or more
counterparts, each of which shall be deemed to be an original, but all of which
shall be one and the same document.

            8.10 Section Headings. The section headings are for the convenience
of the parties and in no way alter, modify, amend, limit, or restrict the
contractual obligations of the parties.

            8.11 Severability. The invalidity or unenforceability of any
provision of this Agreement shall not affect the validity or enforceability of
any other provision of this Agreement.

            8.12 Governing Law. This Agreement shall be governed by and
construed in accordance with the laws of the State of Delaware.

                                     - 17 -
<PAGE>

Executed as of the date first written above.

SONUS NETWORKS, INC.

By: /s/ Rubin Gruber
    -------------------------------------
        Rubin Gruber
        President

FOUNDERS:

/s/ Rubin Gruber
-----------------------------------------
Rubin Gruber

/s/ M. G. Hluchyj
-----------------------------------------
Michael G. Hluchyj

/s/ Kwok P. Wong
-----------------------------------------
Kwok P. Wong

PURCHASERS:

North Bridge Venture Partners II, L.P.

By: North Bridge Venture Management II, L.P.,
    its General Partner

    By: /s/ Edward T. Anderson
        ---------------------------------
        Edward T. Anderson
        General Partner

Matrix Partners IV, L.P.

By: Matrix IV Management Co., L.P., its General Partner

    By: /s/ Paul J. Ferri
        ---------------------------------
        Paul J. Ferri
        General Partner

     [Signature Page 1 of 3 to Series A Preferred Stock Purchase Agreement]

                                     - 18 -
<PAGE>

Charles River Partnership VIII,
A Limited Partnership

By: Charles River VIII GP Limited Partnership,
    its General Partner

    By:
        ---------------------------------
        Richard M. Burnes
        General Partner

Bessemer Venture Venture Partners         BESSEMER VENTURE PARTNERS IV L.P.
                                          By: Deer IV & Co. LLC, General Partner
                                          By: /s/ Robert H. Buescher Manager

    By:                                                  Robert H. Buescher
        ---------------------------------

Bedrock Capital I, L.P.

    By: /s/ Thomas S. Volpe
        ---------------------------------

Bedrock Capital Side-by-Side, L.P.

    By: /s/ Thomas S. Volpe
        ---------------------------------

/s/ James Dolce Jr.
----------------------------------
Jim Dolce

/s/ Derek M. James
----------------------------------
Derek James

     [Signature Page 2 of 3 to Series A Preferred Stock Purchase Agreement]

                                     - 19 -

<PAGE>

----------------------------------
Rubin Gruber

/s/ Kwok P. Wong
----------------------------------
Kwok P. Wong

/s/ David L. Engel
----------------------------------
David L. Engel

/s/ David Rokoff
----------------------------------
David Rokoff

/s/ Anthony J. Risica
----------------------------------
Anthony J. Risica

----------------------------------
Cheng Wu

/s/ Mike G. Hluchyj
----------------------------------
Mike G. Hluchyj

/s/ Robert G. Gallager
----------------------------------
Robert G. Gallager

/s/ Barry Ross
----------------------------------
Barry Ross

/s/ Anthony S. Acampora
----------------------------------
Anthony S. Acampora

     [Signature Page 3 of 3 to Series A Preferred Stock Purchase Agreement]

                                     - 20 -

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00003-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00003-of-00352.parquet"}]]