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                                                                  Exhibit 10.1

8/6/04
NWPLSMT.N

                                 NORTHWEST PARK

                                      LEASE

                                    ARTICLE 1

                                 REFERENCE DATA

1.1       SUBJECT REFERRED TO.

          Each reference in this Lease to any of the following subjects shall be
          construed to incorporate the data stated for that subject in this
          Section 1.l.

                  DATE OF THIS LEASE:    August 9, 2004

                  BUILDING:              The two-story building in Northwest
                                         Park in Burlington, Massachusetts
                                         (hereinafter referred to as the "Park")
                                         located on that certain parcel of land
                                         and known as 71 Third Avenue (the
                                         Building and such parcel of land
                                         hereinafter being collectively referred
                                         to as the "Property").

                  PREMISES:              The entire Building, substantially as
                                         shown on Exhibit A attached hereto.

                  RENTABLE FLOOR
                  AREA OF PREMISES:      Approximately 43,061 square feet

                  LANDLORD:              Seventy One Limited Liability Company

                  ORIGINAL NOTICE
                  ADDRESS OF LANDLORD:   c/o Nordblom Management Company, Inc.
                                         15 Third Avenue
                                         Burlington, Massachusetts 01803

                  TENANT:                Acme Packet, Inc., a Delaware
                                         corporation

                  NOTICE
                  ADDRESS OF TENANT
                  PRIOR TO TAKING
                  POSSESSION OF
                  THE PREMISES:          130 New Boston Street
                                         Woburn, MA 01801

                  NOTICE ADDRESS OF
                  TENANT AFTER TAKING
                  POSSESSION OF THE
                  PREMISES:              71 Third Avenue
                                         Burlington, MA 01803

                  COMMENCEMENT DATE:     See Section 2.2

                  EXPIRATION DATE:       June 30, 2010

                  RENT COMMENCEMENT
                  DATE:                  The later of (i) July 1, 2005 or (ii)
                                         the date on which Landlord's Work (as
                                         defined below) has been "substantially
                                         completed".

                  DELIVERY DATE:         On or about January 15, 2005.

                  ANNUAL FIXED RENT
                  RATE:                  $516,732.00 during the first lease
                                         year; $559,788.00 during the second
                                         lease year; $602,844.00 during the
                                         third lease year; $645,912.00 during
                                         the fourth lease year; and $688,968.00
                                         during the fifth lease year.

                  MONTHLY FIXED RENT
                  RATE:                  $43,061.00 during the first lease year;
                                         $46,649.00 during the second lease
                                         year; $50,237.00 during the third lease
                                         year; $53,826.00 during the fourth
                                         lease year; and $57,414.00 during the
                                         fifth lease year.

                  LETTER OF CREDIT
                  AMOUNT:                $300,000.00 (subject to reduction
                                         pursuant to Section 4.4)

                  INITIAL ESTIMATE OF
                  TAXES FOR THE TAX
                  YEAR:                  $81,804.00

                  INITIAL ESTIMATE OF
                  OPERATING COSTS FOR
                  THE CALENDAR YEAR:     $70,200.00

                  PERMITTED USES:        General offices, research and
                                         development, and light manufacturing,
                                         and shipping and receiving ancillary
                                         thereto.

                  PUBLIC LIABILITY INSURANCE LIMITS:

                      COMMERCIAL GENERAL LIABILITY: $1,000,000 per occurrence
                                                    $2,000,000 general aggregate

1.2       EXHIBITS.

          The Exhibits listed below in this section are incorporated in this
          Lease by reference and are to be construed as a part of this Lease.

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                   EXHIBIT A                  Plan showing the Premises.
                   EXHIBIT B                  Commencement Date Notification
                   EXHIBIT C                  Plans and Specifications
                   EXHIBIT D                  Work Change Order
                   EXHIBIT E                  Form of Letter of Credit
                   EXHIBIT F                  Rules and Regulations
                   EXHIBIT G                  Form Tenant Estoppel Certificate
                   EXHIBIT H                  Initial Tenant's Work

1.3       TABLE OF ARTICLES AND SECTIONS.

          ARTICLE 1 -- REFERENCE DATA

          1.1      Subjects Referred To
          1.2      Exhibits
          1.3      Table of Articles and Sections

          ARTICLE 2 -- PREMISES AND TERM

          2.1      Premises
          2.2      Term
          2.3      Extension Option

          ARTICLE 3 -- IMPROVEMENTS

          3.1      Performance of Work and Approval of Landlord's Work
          3.2      Acceptance of the Premises
          3.3      Pre-Commencement Entry by Tenant

          ARTICLE 4 -- RENT

          4.1      The Fixed Rent
          4.2      Additional Rent
                   4.2.1      Real Estate Taxes
                   4.2.2      Personal Property Taxes
                   4.2.3      Operating Costs
                   4.2.4      Insurance
                   4.2.5      Utilities
          4.3      Late Payment of Rent
          4.4      Letter of Credit
                   4.4.1      Amount of Letter of Credit
                   4.4.2      Renewal of Letter of Credit
                   4.4.3      Draws to Cure Defaults
                   4.4.4      Draws to Pay Damages
                   4.4.5      Draws for Failure to Deliver Substitute Letter of
                              Credit
                   4.4.6      Transferability
                   4.4.7      Return of Letter of Credit at End of Term

          ARTICLE 5 -- LANDLORD'S COVENANTS

          5.1      Affirmative Covenants
                   5.1.1      Heat and Air Conditioning
                   5.1.2      Electricity
                   5.1.3      Cleaning; Water
                   5.1.4      Fire Alarm
                   5.1.5      Repairs
                   5.1.6      Landlord's Insurance
                   5.1.7      Landlord's Indemnification
          5.2      Interruption
          5.3      Outside Services

          ARTICLE 6 -- TENANT'S ADDITIONAL COVENANTS

          6.1      Affirmative Covenants
                   6.1.1      Perform Obligations
                   6.1.2      Use
                   6.1.3      Repair and Maintenance
                   6.1.4      Compliance with Law
                   6.1.5      Indemnification
                   6.1.6      Landlord's Right to Enter
                   6.1.7      Personal Property at Tenant's Risk
                   6.1.8      Payment of Landlord's Cost of Enforcement
                   6.1.9      Yield Up
                   6.1.10     Rules and Regulations
                   6.1.11     Estoppel Certificate
                   6.1.12     Landlord's Expenses Re: Consents

          6.2      Negative Covenants
                   6.2.1      Assignment and Subletting
                   6.2.2      Nuisance
                   6.2.3      Hazardous Wastes and Materials
                   6.2.4      Floor Load; Heavy Equipment
                   6.2.5      Installation, Alterations or Additions
                   6.2.6      Abandonment
                   6.2.7      Signs
                   6.2.8      Parking and Storage

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          ARTICLE 7 -- CASUALTY OR TAKING

          7.1         Termination
          7.2         Restoration.
          7.3         Award
          7.4         Disbursement of Insurance Proceed

          ARTICLE 8 -- DEFAULTS

          8.1         Events of Default
          8.2         Remedies
          8.3         Remedies Cumulative
          8.4         Landlord's Right to Cure Defaults
          8.5         Effect of Waivers of Default
          8.6         No Waiver, etc.
          8.7         No Accord and Satisfaction

          ARTICLE 9 -- RIGHTS OF MORTGAGE HOLDERS

          9.1         Rights of Mortgage Holders
          9.2         Lease Superior or Subordinate to Mortgages

          ARTICLE 10 -- MISCELLANEOUS PROVISIONS

          10.1        Notices From One Party to the Other
          10.2        Quiet Enjoyment
          10.3        Lease Not to be Recorded
          10.4        Limitation of Landlord's Liability
          10.5        Acts of God
          10.6        Landlord's Default
          10.7        Brokerage
          10.8        Applicable Law and Construction

                                    ARTICLE 2

                                PREMISES AND TERM

2.1       PREMISES. Landlord hereby leases to Tenant and Tenant hereby leases
          from Landlord, subject to and with the benefit of the terms,
          covenants, conditions and provisions of this Lease, the Premises,
          excluding, however, the use of the roof of the Building for
          telecommunications equipment, Landlord reserving the right from time
          to time, without unreasonable interference with Tenant's use of the
          Premises, to install, use and repair telecommunications equipment on
          the roof of the Building. Except in the case of an emergency, Landlord
          shall use reasonable efforts to provide Tenant with notice prior to
          Landlord's installation, use or repair of telecommunication equipment
          on the roof of the Building.

          Tenant shall be permitted to use up to 150 parking spaces in the
          parking area serving the Building subject to reduction as may occur on
          account of Tenant's utilization of the shipping and receiving area.

          Landlord reserves the right from time to time, without unreasonable
          interference with Tenant's use of the Premises: (a) to install, use,
          maintain, repair, replace and relocate for service to the Premises and
          other parts of the Building, or either, pipes, ducts, conduits, wires
          and appurtenant fixtures, wherever located in the Premises or
          Building, (b) to make any repairs and replacements to the Premises
          which Landlord may deem necessary, and (c) in connection with any
          excavation made upon adjacent land of Landlord or others, to enter,
          and to license others to enter, upon the Premises to do such work as
          the person causing such excavation deems necessary to preserve the
          wall of the Building from injury or damage and to support the same.
          Except in the case of an emergency, Landlord shall use reasonable
          efforts to provide Tenant with notice prior to entering the Building
          in connection with Landlord's exercise of its rights under this
          paragraph.

2.2       TERM. TO HAVE AND TO HOLD for a term beginning on the date (the
          "Commencement Date") on which Tenant first occupies all or any portion
          of the Premises for the conduct of its business, provided Landlord's
          Work has been substantially completed (defined below), and ending on
          the Expiration Date, unless sooner terminated as hereinafter provided.
          The Commencement Date is estimated to occur 100 days after the
          issuance of the building permit for Landlord's Work. When the
          Commencement Date has been determined, such date shall be evidenced by
          a document, in the form attached hereto as Exhibit B, which Landlord
          shall complete and deliver to Tenant, and which shall be deemed
          conclusive unless Tenant shall notify Landlord of any disagreement
          therewith within ten (10) days of receipt. The term "substantially
          completed" as used herein shall mean that (i) the work to be performed
          by Landlord pursuant to Exhibit C has been completed with the
          exception of minor items which can be fully completed without material
          interference with Tenant and other items which because of the season
          or weather or the nature of the item are not practicable to do at the
          time, provided that none of said items is necessary to make the
          Premises tenantable for the Permitted Uses, and (ii) a temporary or
          permanent certificate of occupancy shall have been issued for the
          Premises. However, the Landlord's Work shall be deemed to be
          "substantially completed" on the date that such work would have been
          substantially completed but for any delays caused by Tenant, but
          Landlord shall not be relieved from the obligation to actually
          complete Landlord's Work.

          The term "lease year" as used herein shall mean a period of twelve
          (12) consecutive full calendar months. The first lease year shall
          begin on the Rent Commencement Date if the Rent Commencement Date is
          the first day of a calendar month; if not, then the first lease year
          shall commence upon the first day of the calendar month next following
          the Rent Commencement Date. Each succeeding lease year shall commence
          upon the anniversary date of the first lease year.

2.3       EXTENSION OPTION. Tenant shall have the right to extend the term of
          this Lease for one additional period of five (5) years, to begin
          immediately upon the expiration of the original term of this Lease
          (the "extended term"), provided that each of the following conditions
          has been satisfied:

                   (i) As of the date of the Extension Notice (defined below)
                   and as of the commencement of the extended term, Tenant shall
                   not be in default and shall not have previously been in
                   default of its obligations under this Lease beyond any
                   applicable grace period;

                   (ii) Tenant shall have had a net income for the 12-month
                   period immediately preceding the date of the Extension Notice
                   and for the 12-month period immediately preceding the
                   commencement of the extended term, or in the alternative,
                   Tenant shall have sufficient income or financial resources to
                   meet Tenant's obligations under this Lease during the
                   extended term; and

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                   (iii) simultaneously with the delivery of the Extension
                   Notice and also at the commencement of the extended term,
                   Tenant shall have delivered to Landlord an audited statement,
                   prepared by Tenant's accountant using generally accepted
                   accounting principles either (x) evidencing such net income
                   during each of the periods specified above, or (y)
                   demonstrating to Landlord's reasonable satisfaction that
                   Tenant has sufficient income or financial resources to meet
                   Tenant's obligations under this Lease during the extended
                   term.

          All of the terms, covenants and provisions of this Lease shall apply
          to such extended term except that the Annual Fixed Rent Rate for such
          extension period shall be the market rate for comparable buildings in
          the Burlington area at the commencement of such extended term, as
          designated by Landlord. If Tenant shall elect to exercise the
          aforesaid option, it shall do so by giving Landlord written notice
          (the "Extension Notice") of its intention to do so not later than one
          (1) year prior to the expiration of the original term of this Lease.
          If Tenant gives such notice and satisfies the conditions specified
          above, the extension of this Lease shall be automatically effected
          without the execution of any additional documents. The original term
          and the extended term are hereinafter collectively called the "term".

          If Tenant properly exercises the aforesaid option, then not later than
          eleven (11) months prior to the expiration of the original term of
          this Lease Landlord shall give written notice to Tenant of Landlord's
          designation of the market rate. Within fifteen (15) days following
          Landlord's notice, Tenant shall either propose its designation of the
          market rate by giving notice thereof to Landlord or shall accept
          Landlord's designation. Failure on the part of Tenant to give such
          notice of its designation shall bind Tenant to Landlord's designation.
          If Tenant proposes its designation of the market rate, then Landlord
          and Tenant shall attempt to agree upon a market rate. If the parties
          have been unable to reach agreement within thirty (30) days following
          Tenant's designation, then the market rate may be submitted to
          arbitration by either party as follows: market rate shall he
          determined by impartial arbitrators, one to be chosen by the Landlord,
          one to be chosen by Tenant, and a third to be selected, if necessary,
          as below provided. The unanimous written decision of the two first
          chosen, without selection and participation of a third arbitrator, or
          otherwise, the written decision of a majority of three arbitrators
          chosen and selected as aforesaid, shall be conclusive and binding upon
          Landlord and Tenant. Landlord and Tenant shall each notify the other
          of its chosen arbitrator within ten (10) days following the call for
          arbitration and, unless such two arbitrators shall have reached a
          unanimous decision within thirty (30) days after their designation,
          they shall so notify the then President of the Boston Bar Association
          and request him to select an impartial third arbitrator, who shall be
          another office building owner, a real estate counsellor or a broker
          dealing with like types of properties, to determine market rate as
          herein defined. Such third arbitrator and the first two chosen shall
          hear the parties and their evidence and render their decision within
          thirty (30) days following the conclusion of such hearing and notify
          Landlord and Tenant thereof. Landlord and Tenant shall share equally
          the expense of the third arbitrator (if any). If the dispute between
          the parties as to a market rate has not been resolved before the
          commencement of Tenant's obligation to pay Fixed Rent based upon such
          market rate, then Tenant shall pay Fixed Rent under the Lease based
          upon the market rate designated by Landlord until either the agreement
          of the parties as to the market rate, or the decision of the
          arbitrators, as the case may be, at which time Tenant shall pay any
          underpayment of Fixed Rent to Landlord, or Landlord shall refund any
          overpayment of Fixed Rent to Tenant.

          In any event, the Annual Fixed Rent Rate for the extended term shall
          not be less than the Annual Fixed Rent Rate in effect immediately
          prior to such extended term.

                                    ARTICLE 3

                                  IMPROVEMENTS

3.1       PERFORMANCE OF WORK AND APPROVAL OF LANDLORD'S WORK. Landlord shall
          cause to be performed the work desired by Tenant to prepare the
          Premises for Tenant's use and occupancy in accordance with the plans
          and specifications attached hereto as Exhibit C (the "Landlord's
          Work"). All such work shall be done in a good and workmanlike manner
          employing good materials and so as to conform to all applicable
          building laws. Landlord agrees to deliver the Premises on the date
          Landlord's Work is substantially completed in compliance with the
          Massachusetts building code. All other work and installations which
          are necessary or desirable to prepare the Premises for Tenant's use
          and occupancy shall be performed by Tenant at Tenant's expense,
          including without limitation the installation of furniture, fixtures
          and equipment, all voice wiring, security systems, and any specialty
          HVAC and plumbing (the "Tenant's Work"). Tenant agrees that Landlord
          may make any changes in such work which may become reasonably
          necessary or advisable, other than substantial changes, without
          approval of Tenant, provided written notice is promptly given to
          Tenant; and Landlord may make substantial changes in such work, with
          the written approval of Tenant, which shall not be unreasonably
          withheld or delayed. Landlord shall use diligence to cause Landlord's
          work to be substantially completed by the Delivery Date, subject to
          the provisions of Section 10.5 hereof and any delays caused by action
          or inaction of Tenant. Landlord agrees that Tenant may make changes in
          such work with the approval of Landlord and the execution by Landlord
          and Tenant of a Work Change Order, in the form attached hereto as
          Exhibit D. Notwithstanding anything to the contrary contained herein,
          if Landlord's Work is not substantially completed by that date (the
          "Outside Date") which is 60 days from the Delivery Date and such
          failure is not the result of delays caused by Tenant, Tenant shall
          have the right to terminate this Lease by giving written notice to
          Landlord within five (5) days following the Outside Date, such
          termination to be effective at the expiration of thirty (30) days from
          the giving of such notice, and if prior to the expiration of the
          aforesaid thirty (30) day period the work has not been substantially
          completed, this Lease shall thereupon terminate. If Tenant does not
          exercise said termination right within said five (5) day period,
          Tenant shall be deemed to have waived its right to terminate this
          Lease and this Lease shall continue in full force and effect as
          between the parties.

          If Landlord has not obtained the applicable and necessary permits for
          the performance of Landlord's Work by November 15, 2004, either party
          shall have the right to terminate this Lease by giving written notice
          to the other no later than November 20, 2004, whereupon this Lease
          shall terminate. If neither party exercises its respective termination
          right as set forth in the preceding sentence by November 20, 2004,
          then the aforesaid termination right shall be void and this Lease
          shall continue in full force and effect as between the parties.
          Notwithstanding the foregoing, if Tenant does not execute and deliver
          an original of this Lease to Landlord and sign the plans and
          specifications attached hereto as Exhibit C (which signature shall
          evidence Tenant's agreement to the scope of Landlord's Work) by August
          15, 2004, Tenant shall be deemed to have waived its right to terminate
          this Lease as set forth in this paragraph.

3.2       ACCEPTANCE OF THE PREMISES. Tenant or its representatives may, at
          reasonable times, enter upon the Premises during the progress of the
          work to inspect the progress thereof and to determine if the work is
          being performed in accordance with the requirements of Section 3.1.
          Tenant shall promptly give to Landlord notices of any alleged failure
          by Landlord to comply with those requirements. Landlord's Work shall
          be deemed approved by Tenant upon the date Tenant takes occupancy of
          the Premises for the conduct of its business, except for items of
          Landlord's Work which are uncompleted or do not conform to Exhibit C
          and as to which Tenant shall, in either case, have given written
          notice to Landlord prior to such occupancy. A certificate of
          completion by a licensed architect or registered engineer shall be
          conclusive evidence that Landlord's Work has been completed except for
          items stated in such certificate to be incomplete or not in conformity
          with Exhibit C.

3.3       PRE-COMMENCEMENT ENTRY BY TENANT. With Landlord's prior consent, which
          shall not be unreasonably withheld or delayed, Tenant shall have the
          right to enter the Premises during the performance of Landlord's Work,
          during normal business hours and without payment of rent, but
          otherwise subject to all the terms and conditions of this Lease,
          including Sections 4.2.4 and 6.2.5, to perform the Tenant's Work, so
          long as such work does not interfere with the performance of
          Landlord's Work.

                                    ARTICLE 4

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                                      RENT

4.1       THE FIXED RENT. Commencing on the Rent Commencement Date, Tenant
          covenants and agrees to pay rent to Landlord at the Original Address
          of Landlord or at such other place or to such other person or entity
          as Landlord may by notice in writing to Tenant from time to time
          direct, at the Annual Fixed Rent Rate, in equal installments at the
          Monthly Fixed Rent Rate (which is 1/12th of the Annual Fixed Rent
          Rate), in advance, without notice or demand, and without setoff,
          abatement, suspension, deferment, reduction or deduction, except as
          otherwise expressly provided herein, on the first day of each calendar
          month included in the term; and for any portion of a calendar month
          following the Rent Commencement Date, at the rate for the first lease
          year payable in advance for such portion. It is the intention of the
          parties hereto that the obligations of Tenant hereunder shall be
          separate and independent covenants and agreements, that the Annual
          Fixed Rent, the Additional Rent and all other sums payable by Tenant
          to Landlord shall continue to be payable in all events and that the
          obligations of Tenant hereunder shall continue unaffected, unless the
          requirement to pay or perform the same shall have been terminated or
          abated pursuant to an express provision of this Lease.

          If Landlord shall give notice to Tenant that all rent and other
          payments due hereunder are to be made to Landlord by electronic funds
          transfers, so called, or by similar means, Tenant shall make all such
          payments as shall be due after receipt of said notice by means of said
          electronic funds transfers (or such similar means as designated by
          Landlord).

4.2       ADDITIONAL RENT. Commencing on the Commencement Date, but in no event
          later than the Rent Commencement Date, Tenant covenants and agrees to
          pay, as Additional Rent, insurance costs, utility charges, personal
          property taxes and taxes and operating costs with respect to the
          Premises as provided in this Section 4.2 as follows:

          4.2.1     REAL ESTATE TAXES. Tenant shall pay to Landlord, as
                    additional rent, for each tax period partially or wholly
                    included in the term, payments on account of Taxes (as
                    hereinafter defined) assessed against the Property during
                    any fiscal tax year during the term (a "Tax Year"). Tenant
                    shall remit to Landlord, on the first day of each calendar
                    month, estimated payments on account of Taxes, such monthly
                    amounts to be sufficient to provide Landlord, by the time
                    real estate TAX payments are due and payable to any
                    governmental authority responsible for collection of same, a
                    sum equal to the Taxes, as reasonably estimated by Landlord
                    from time to time on the basis of the most recent tax data
                    available. The initial calculation of the monthly estimated
                    payments shall be based upon the Initial Estimate of Taxes
                    for the Tax Year and upon quarterly payments being due to
                    the governmental authority on August 1, November 1, February
                    1 and May 1, and shall be made when the Commencement Date
                    has been determined. Upon written request from Tenant to
                    Landlord, Tenant shall have the right, within sixty (60)
                    days following the end of each fiscal year, to review a copy
                    of the tax bill for the preceding fiscal year at Landlord's
                    offices. If the total of such monthly remittances for any
                    Tax Year is greater than the actual Taxes for such Tax Year,
                    Landlord shall credit against the next accruing payments to
                    be made by Tenant pursuant to this subsection 4.2.1, the
                    difference, unless Tenant requests in writing that Landlord
                    pay any such difference to Tenant; if the total of such
                    remittances is less than the actual Taxes for such Tax Year,
                    Tenant shall pay the difference to Landlord at least ten
                    (10) days prior to the date or dates within such Tax Year
                    that Taxes become due and payable to the governmental
                    authority (but in any event no earlier than ten (10) days
                    following a written notice to Tenant, which notice shall set
                    forth the manner of computation of Tenant's Percentage of
                    Taxes).

                    If, after Tenant shall have made reimbursement to Landlord
                    pursuant to this subsection 4.2.1, Landlord shall receive a
                    refund of any portion of Taxes paid by Tenant with respect
                    to any Tax Year during the term hereof as a result of an
                    abatement of such Taxes by legal proceedings, settlement or
                    otherwise (without either party having any obligation to
                    undertake any such proceedings), Landlord shall credit
                    against the next accruing payments to be made by Tenant
                    pursuant to this subsection 4.2.1, such refund (less the
                    expenses, including attorneys' fees and appraisers' fees,
                    incurred in connection with obtaining any such refund), as
                    relates to Taxes paid by Tenant to Landlord with respect to
                    any Tax Year for which such refund is obtained, unless
                    Tenant requests in writing that Landlord pay any such refund
                    to Tenant.

                    In the event this Lease shall commence, or shall end (by
                    reason of expiration of the term or earlier termination
                    pursuant to the provisions hereof), on any date other than
                    the first or last day of the Tax Year, or should the Tax
                    Year or period of assessment of real estate taxes be changed
                    or be more or less than one (1) year, as the case may be,
                    then the amount of Taxes which may be payable by Tenant as
                    provided in this subsection 4.2.1 shall be appropriately
                    apportioned and adjusted.

                    The term "Taxes" shall mean all taxes, assessments,
                    betterments and other charges and impositions (including,
                    but not limited to, fire protection service fees and similar
                    charges) levied, assessed or imposed at any time during the
                    term by any governmental authority upon or against the
                    Property, or taxes in lieu thereof, and additional types of
                    taxes to supplement real estate taxes due to legal limits
                    imposed thereon. If, at any time during the term of this
                    Lease, any tax or excise on rents or other taxes, however
                    described, are levied or assessed against Landlord with
                    respect to the rent reserved hereunder, either wholly or
                    partially in substitution for, or in addition to, real
                    estate taxes assessed or levied on the Property, such tax or
                    excise on rents shall be included in Taxes; however, Taxes
                    shall not include franchise, estate, inheritance,
                    succession, capital levy, transfer, income or excess profits
                    taxes assessed on Landlord. Taxes shall include any
                    estimated payment made by Landlord on account of a fiscal
                    tax period for which the actual and final amount of taxes
                    for such period has not been determined by the governmental
                    authority as of the date of any such estimated payment.

          4.2.2     PERSONAL PROPERTY TAXES. Tenant shall pay all taxes charged,
                    assessed or imposed upon the personal property of Tenant in
                    or upon the Premises.

          4.2.3     OPERATING COSTS. Tenant shall pay to Landlord the Operating
                    Costs (as hereinafter defined) incurred by Landlord in any
                    calendar year. Tenant shall remit to Landlord, on the first
                    day of each calendar month, estimated payments on account of
                    Operating Costs, such monthly amounts to be sufficient to
                    provide Landlord, by the end of the calendar year, a sum
                    equal to the Operating Costs, as reasonably estimated by
                    Landlord from time to time. The initial monthly estimated
                    payments shall be in an amount equal to 1/12th of the
                    Initial Estimate of Operating Costs for the calendar year.
                    Following the end of each calendar year, including the first
                    calendar year, Landlord shall deliver to Tenant a reasonably
                    detailed statement of the Operating Costs payable under this
                    Section 4.2.3 for such calendar year, prepared, allocated
                    and computed in accordance with generally accepted
                    accounting principles (the "Annual Operating Statement").
                    If, at the expiration of the calendar year in respect of
                    which monthly installments of Operating Costs shall have
                    been made as aforesaid, the total of such monthly
                    remittances is greater than the actual Operating Costs for
                    such calendar year, Landlord shall credit against the next
                    accruing payments to be made by Tenant pursuant to this
                    subsection 4.2.3, the difference, unless Tenant requests in
                    writing that Landlord pay any such difference to Tenant; if
                    the total of such remittances is less than the Operating
                    Costs for such calendar year, Tenant shall pay the
                    difference to Landlord within twenty (20) days from the date
                    Landlord furnishes to Tenant the Annual Operating Statement.
                    Any reimbursement for Operating Costs due and payable by
                    Tenant with respect to periods of less than twelve (12)
                    months shall be equitably prorated.

                    The term "Operating Costs" shall mean all costs and expenses
                    incurred for the operation, cleaning, maintenance, repair
                    and upkeep of the Property, and the portion of such costs
                    and expenses with regard to the common areas, facilities and
                    amenities of the Park which is equitably allocable to the
                    Property, including, without limitation, all costs of
                    maintaining and repairing the Property and the Park
                    (including snow removal, landscaping and grounds
                    maintenance, operation and maintenance of parking lots,
                    sidewalks, walking paths, access roads and driveways,
                    security, operation and repair of heating and
                    air-conditioning equipment, elevators, lighting and any
                    other Building equipment or systems) and of all repairs and
                    replacements (other than repairs or replacements for which
                    Landlord has received full reimbursement from contractors or
                    from others) necessary to keep the Property and the Park in
                    good working order, repair, appearance and condition; all

                                        5
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                    costs, including material and equipment costs, for window
                    cleaning of the Building; all costs of any reasonable
                    insurance carried by Landlord relating to the Property; all
                    costs related to provision of heat (including oil, electric,
                    steam and/or gas), air-conditioning, and water (including
                    sewer charges) and other utilities to the Building; payments
                    under all service contracts relating to the foregoing; all
                    compensation, fringe benefits, payroll taxes and workmen's
                    compensation insurance premiums related thereto with respect
                    to any employees of Landlord or its affiliates engaged in
                    security and maintenance of the Property and the Park;
                    attorneys' fees and disbursements (exclusive of any such
                    fees and disbursements incurred in tax abatement
                    proceedings) and auditing and other professional fees and
                    expenses incurred in connection with the Park; and a
                    reasonable management fee consistent with management fees
                    charged by landlord's of comparable buildings in the
                    Burlington area.

                    There shall not be included in such Operating Costs (i)
                    brokerage fees (including rental fees) related to the
                    operation of the Building; (ii) interest and depreciation
                    charges incurred on the Property; (iii) expenditures made by
                    Tenant with respect to (a) cleaning, maintenance and upkeep
                    of the Premises, except to the extent provided by Landlord
                    at Tenant's request or pursuant to the terms and conditions
                    of this Lease, and (b) the provision of electricity to the
                    Premises; (iv) mortgage charges (including principal and
                    interest); (v) the cost of work done or services supplied by
                    Landlord for a particular tenant in the Park for which
                    Landlord has the right to be reimbursed by such tenant; (vi)
                    any cost incurred by the gross negligence or willful
                    misconduct of the Landlord, its agents and employees; (vii)
                    except to the extent caused by or attributable to Tenant,
                    penalties, fines and other costs incurred due to violation
                    by the Landlord of any lease or any laws, rules, regulations
                    or ordinances applicable to the Building and any interest or
                    penalties due for late payment by Landlord of any of the
                    expenses; (viii) expenses to prepare, renovate, repaint,
                    redecorate or perform any other work in any space leased to
                    an existing or prospective tenant or other occupant of the
                    Park other than Tenant (except as otherwise agreed to); (ix)
                    expenses incurred by Landlord to resolve disputes, enforce
                    or negotiate lease terms with prospective or existing
                    tenants other than Tenant or in connection with any
                    financing, sale or syndication of the Building; (x) fees
                    paid to affiliates of Landlord to the extent that such fees
                    exceed the customary amount charged for the services
                    provided by unaffiliated persons or entities of similar
                    skill, competence and experience; (xi) to the extent that
                    insurance proceeds are unavailable due to Landlord's failure
                    to maintain replacement cost insurance, costs and expenses
                    incurred by Landlord in connection with the repair of damage
                    to the Building caused by fire or other casualty, insured or
                    required to be insured against hereunder; (xii) reserves for
                    Operating Costs; (xiii) amortization and depreciation of the
                    Building (except as set forth below with respect to capital
                    items); (xiv) costs to repair any items related to the
                    Building or the Property covered by warranty; and (xv)
                    except as stated below, capital expenditures.

                    If, during the term of this Lease, Landlord shall replace
                    any capital items or make any capital expenditures in order
                    to comply with laws in effect after the Commencement Date,
                    or to effect savings in Operating Costs, or to replace
                    worn-out items (collectively, the "capital expenditures")
                    the total amount of which is not properly included in
                    Operating Costs for the calendar year in which they were
                    made, there shall nevertheless be included in Operating
                    Costs for each calendar year in which and after such capital
                    expenditure is made the annual charge-off of such capital
                    expenditure. (Annual charge-off shall be determined by (i)
                    dividing the original cost of the capital expenditure by the
                    number of years of useful life thereof [The useful life
                    shall be reasonably determined by Landlord in accordance
                    with generally accepted accounting principles and practices
                    in effect at the time of acquisition of the capital item.];
                    and (ii) adding to such quotient an interest factor computed
                    on the unamortized balance of such capital expenditure based
                    upon an interest rate reasonably determined by Landlord as
                    being the interest rate then being charged for long-term
                    mortgages by institutional lenders on like properties within
                    the locality in which the Building is located.) Provided,
                    further, that if Landlord reasonably concludes on the basis
                    of engineering estimates that a particular capital
                    expenditure will effect savings in Operating Costs and that
                    such annual projected savings will exceed the annual
                    charge-off of capital expenditure computed as aforesaid,
                    then and in such events, the annual charge-off shall be
                    determined by dividing the amount of such capital
                    expenditure by the number of years over which the projected
                    amount of such savings shall fully amortize the cost of such
                    capital item or the amount of such capital expenditure; and
                    by adding the interest factor, as aforesaid.

                    Upon Tenant's written request (the "Tenant's Audit Notice"),
                    which request must be made by Tenant within sixty (60) days
                    after Landlord delivers to Tenant the Annual Operating
                    Statement, Tenant shall have the right to inspect or audit
                    Landlord's books of account with respect to matters set
                    forth in the Annual Operating Statement. Tenant's audit or
                    inspection shall commence no later than thirty (30) days
                    after Tenant's Audit Notice and shall be conducted only at
                    Landlord's offices where said books of account are kept
                    during business hours reasonably designated by Landlord.
                    Tenant shall pay all costs of such audit or inspection.
                    Tenant may not conduct an inspection or have an audit
                    performed under this Section 4.2.3 more than once with
                    respect to any period covered by any Annual Operating
                    Statement from Landlord. Landlord shall keep full and
                    accurate books of account covering the Operating Costs and
                    the Annual Operating Statement shall accurately reflect the
                    same and Tenant's share thereof. Such audit or inspection
                    may only be made by Tenant or a nationally, recognized
                    certified public accounting firm or a reputable auditing
                    company which is not compensated on a contingency fee basis.
                    All non-public information about Landlord and/or the
                    Property discovered during the course of such examination
                    shall be kept confidential.

          4.2.4     INSURANCE. Tenant shall, at its expense, as Additional Rent,
                    take out and maintain throughout the term the following
                    insurance protecting Landlord:

                    4.2.4.1   Commercial general liability insurance naming
                              Landlord, Tenant, and Landlord's managing agent
                              and any mortgagee of which Tenant has been given
                              notice as insureds or additional insureds and
                              indemnifying the parties so named against all
                              claims and demands for death or any injury to
                              person or damage to property which may be claimed
                              to have occurred on the Premises (or the Property,
                              insofar as used by customers, employees, servants
                              or invitees of the Tenant), in amounts which
                              shall, at the beginning of the term, be at least
                              equal to the limits set forth in Section 1.1, and,
                              which, from time to time during the term, shall be
                              for such higher limits, if any, as are customarily
                              carried in the area in which the Premises are
                              located on property similar to the Premises and
                              used for similar purposes; $5,000,000.00 umbrella
                              liability for bodily injury, personal injury and
                              property damage, naming Landlord, and its managing
                              agent and mortgagee, as additional insureds; and
                              workmen's compensation insurance with statutory
                              limits covering all of Tenant's employees working
                              on the Premises.

                    4.2.4.2   Fire insurance with the usual extended coverage
                              endorsements covering all Tenant's furniture,
                              furnishings, fixtures and equipment, the Tenant's
                              Work and any other contents or improvements in the
                              Premises installed at Tenant's expense by or on
                              behalf of Tenant during the term.

                    4.2.4.3   All such policies shall be obtained from
                              responsible companies qualified to do business and
                              in good standing in Massachusetts, which companies
                              and the amount of insurance allocated thereto
                              shall be subject to Landlord's reasonable
                              approval. Tenant agrees to furnish Landlord with
                              certificates evidencing all such insurance prior
                              to the beginning of the term hereof and evidencing
                              renewal thereof just prior to the expiration of
                              any such policy. Each such policy shall be
                              non-cancelable with respect to the interest of
                              Landlord without at least ten (10) days' prior
                              written notice thereto. In the event provision for
                              any such insurance is to be by a blanket insurance
                              policy, the policy shall allocate a specific and
                              sufficient amount of coverage to the Premises.

                    4.2.4.4   All insurance which is carried by either party
                              with respect to the Building, Premises or to
                              furniture, furnishings, fixtures, or equipment
                              therein or alterations or improvements thereto,
                              whether or not required, shall include provisions
                              which either designate the other party as one of
                              the insured or deny to the insurer acquisition by
                              subrogation of rights of recovery against the
                              other party to the extent such rights have been
                              waived by the insured party prior to occurrence of
                              loss or injury, insofar as, and to the extent
                              that, such provisions may be effective without
                              making it impossible to obtain insurance coverage
                              from responsible companies qualified to do

                                        6
<Page>

                              business in the state in which the Premises are
                              located (even though extra premium may result
                              therefrom). In the event that extra premium is
                              payable by either party as a result of this
                              provision, the other party shall reimburse the
                              party paying such premium the amount of such extra
                              premium. If at the request of one party, this
                              non-subrogation provision is waived, then the
                              obligation of reimbursement shall cease for such
                              period of time as such waiver shall be effective,
                              but nothing contained in this subsection shall
                              derogate from or otherwise affect releases
                              elsewhere herein contained of either party for
                              claims. Each party shall be entitled to have
                              certificates of any policies containing such
                              provisions. Each party hereby waives all rights of
                              recovery against the other for loss or injury
                              against which the waiving party is protected by
                              insurance containing said provisions, reserving,
                              however, any rights with respect to any excess of
                              loss or injury over the amount recovered by such
                              insurance. Tenant shall not acquire as insured
                              under any insurance carried on the Premises any
                              right to participate in the adjustment of loss or
                              to receive insurance proceeds and agrees upon
                              request promptly to endorse and deliver to
                              Landlord any checks or other instruments in
                              payment of loss in which Tenant is named as payee.

          4.2.5     UTILITIES. Tenant shall pay all charges made by public
                    authority or utility for the cost of electricity furnished
                    or consumed on the Premises, all charges for any utilities
                    supplied by Landlord pursuant to Subsections 5.1.1 and 5.1.3
                    which are separately metered, and all charges for telephone
                    and other utilities or services not supplied by Landlord
                    pursuant to Subsections 5.1.1 and 5.1.3, whether designated
                    as a charge, tax, assessment, fee or otherwise, all such
                    charges to be paid as the same from time to time become due.

4.3       LATE PAYMENT OF RENT. If any installment of rent is paid after the
          date the same was due, and if on a prior occasion in the twelve (12)
          month period prior to the date such installment was due an installment
          of rent was paid after the same was due, then Tenant shall pay
          Landlord a late payment fee equal to five (5%) percent of the overdue
          payment.

4.4       LETTER OF CREDIT. The performance of Tenant's obligations under this
          Lease shall be secured by a letter of credit throughout the term
          hereof in accordance with and subject to the following terms and
          conditions:

          4.4.1     AMOUNT OF LETTER OF CREDIT. (a) Concurrently with Tenant's
                    execution and delivery of this Lease, Tenant shall deliver
                    to Landlord an irrevocable standby letter of credit (the
                    "Original Letter of Credit") which shall be (i) in the form
                    of Exhibit F attached to this Lease or in a form reasonably
                    acceptable to both Landlord and Tenant (the "Form LC"), (ii)
                    issued by a bank reasonably satisfactory to Landlord upon
                    which presentment may be made in Boston, Massachusetts,
                    (iii) in the amount equal to the Letter of Credit Amount,
                    and (iv) for a term of at least 1 year, subject to the
                    provisions of Section 4.4.2 below. The Original Letter of
                    Credit, any Additional Letters(s) of Credit and Substitute
                    Letter(s) of Credit are referred to herein as the "Letter of
                    Credit."

                    (b) On the condition that (i) Tenant is not in default under
                    this Lease at the time of the reduction, and (ii) either (x)
                    Tenant has achieved a profitable calendar year and Tenant
                    provides Landlord with an audited statement reporting such
                    profitable calendar year, which statement shall be prepared
                    by Tenant's accountant using generally accepted accounting
                    principles, or (y) Tenant has a minimum of $10,000,000.00 of
                    unrestricted cash and securities at any time after the end
                    of the 3RD lease year and provides Landlord with reasonable
                    evidence of the same, then the Letter of Credit Amount shall
                    be reduced to $150,000.00. This reduction shall only be
                    effected one time during the term of this Lease.

          4.4.2     RENEWAL OF LETTER OF CREDIT. Each Letter of Credit shall be
                    automatically renewable in accordance with the second to
                    last paragraph of the Form LC; provided however, that Tenant
                    shall be required to deliver to Landlord a new letter of
                    credit (a "Substitute Letter of Credit") satisfying the
                    requirements for the Original Letter of Credit under Section
                    4.4.1 on or before the date 30 days prior to the expiration
                    of the term of the Letter of Credit then in effect, if the
                    issuer of such Letter of Credit gives notice of its election
                    not to renew such Letter of Credit for any additional period
                    pursuant thereto. Should any Letter of Credit contain a
                    final expiration date, in addition to a current expiration
                    date, such final expiration date shall be no earlier than 45
                    days following the Expiration Date of this Lease.

          4.4.3     DRAWS TO CURE DEFAULTS. If the Fixed Rent, Additional Rent
                    or any other sum payable to Landlord hereunder shall be
                    overdue and unpaid or should Landlord make payments on
                    behalf of the Tenant, or Tenant shall fail to perform any of
                    the terms of this Lease in all cases beyond the expiration
                    of all applicable notice and cure periods, then Landlord
                    shall have the right, at any time thereafter to draw down
                    from the Letter of Credit the amount necessary to cure such
                    default. In the event of any such draw by the Landlord,
                    Tenant shall, within 30 days of written demand therefor,
                    deliver to Landlord an additional Letter of Credit
                    ("Additional Letter of Credit") satisfying the requirements
                    for the Original Letter of Credit, except that the amount of
                    such Additional Letter of Credit shall be the amount of such
                    draw.

          4.4.4     DRAWS TO PAY DAMAGES. In addition, if (i) this Lease shall
                    have been terminated as a result of Tenant's default under
                    this Lease beyond the expiration of the applicable cure
                    period, and/or (ii) this Lease shall have been rejected in a
                    bankruptcy or other creditor-debtor proceeding, then
                    Landlord shall have the right at any time thereafter to draw
                    down from the Letter of Credit an amount sufficient to pay
                    any and all damages payable by Tenant on account of such
                    termination or rejection, as the case may be, pursuant to
                    Article 8 hereof. In the event of bankruptcy or other
                    creditor-debtor proceeding against Tenant, all proceeds of
                    the Letter of Credit shall be deemed to be applied first to
                    the payment of rent and other charges due Landlord for all
                    periods prior to the filing of such proceedings.

          4.4.5     DRAWS FOR FAILURE TO DELIVER SUBSTITUTE LETTER OF CREDIT. If
                    Tenant fails timely to deliver to Landlord a Substitute
                    Letter of Credit, then Landlord shall have the right, at any
                    time thereafter, without giving any notice to Tenant, to
                    draw down the Letter of Credit and to hold the proceeds
                    thereof ("Security Proceeds") in a bank account in the name
                    of Landlord, which may be withdrawn and applied by Landlord
                    under the same circumstances and for the same purposes as if
                    the Security Proceeds were a Letter of Credit. Upon any such
                    application of Security Proceeds by Landlord, Tenant shall,
                    within 30 days of written demand therefor, deliver to
                    Landlord an Additional Letter of Credit in the amount of
                    Security Proceeds so applied.

          4.4.6     TRANSFERABILITY. Landlord shall (i) transfer its beneficial
                    interest under the Letter of Credit or any Security Proceeds
                    in connection with Landlord's sale or transfer of the
                    Building, or (ii) be entitled to transfer its beneficial
                    interest under the Letter of Credit or any Security proceeds
                    in connection with the addition, deletion or modification of
                    any beneficiaries under the Letter of Credit, and the Letter
                    of Credit shall specifically state on its face that it is
                    transferable by Landlord, its successors and assigns. Tenant
                    agrees to pay Landlord upon demand, as Additional Rent, all
                    costs and fees charged to effect such transfer.

          4.4.7     RETURN OF LETTER OF CREDIT AT END OF TERM. Within 30 days
                    after the expiration of the term, to the extent Landlord has
                    not previously drawn upon any Letter of Credit or Security
                    Proceeds held by Landlord, Landlord shall return the same to
                    Tenant provided that there is not at such time any
                    continuing default of any of Tenant's obligations under this
                    Lease.

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                                    ARTICLE 5

                              LANDLORD'S COVENANTS

5.1       AFFIRMATIVE COVENANTS. Landlord covenants with Tenant:

          5.1.1     HEAT AND AIR-CONDITIONING. To furnish to the Premises,
                    separately metered and at the direct expense of Tenant as
                    hereinabove provided, heat and air-conditioning (reserving
                    the right, at any time, to change energy or heat sources)
                    sufficient to maintain the Premises at comfortable
                    temperatures (subject to all federal, state, and local
                    regulations relating to the provision of heat), during such
                    hours of the day and days of the year that the Building is
                    normally open.

          5.1.2     ELECTRICITY. To furnish to the Premises, separately metered
                    and at the direct expense of Tenant as hereinabove provided,
                    reasonable electricity for Tenant's Permitted Uses. If
                    Tenant shall require electricity in excess of reasonable
                    quantities for Tenant's Permitted Uses and if (i) in
                    Landlord's reasonable judgment, Landlord's facilities are
                    inadequate for such excess requirements, or (ii) such excess
                    use shall result in an additional burden on the Building
                    utilities systems and additional cost to Landlord on account
                    thereof, as the case may be, (a) Tenant shall, upon demand,
                    reimburse Landlord for such additional cost, as aforesaid,
                    or (b) Landlord, upon written request, and at the sole cost
                    and expense of Tenant, will furnish and install such
                    additional wire, conduits, feeders, switchboards and
                    appurtenances as reasonably may be required to supply such
                    additional requirements of Tenant (if electricity therefor
                    is then available to Landlord), provided that the same shall
                    be permitted by applicable laws and insurance regulations
                    and shall not cause permanent damage or injury to the
                    Building or cause or create a dangerous or hazardous
                    condition or entail excessive or unreasonable alterations or
                    repairs.

          5.1.3     WATER. To furnish water for ordinary cleaning, lavatory,
                    toilet and shower facilities and for all kitchen appliances
                    and sinks.

          5.1.4     FIRE ALARM. To maintain fire alarm systems within the
                    Building.

          5.1.5     REPAIRS. Except as otherwise expressly provided herein, to
                    make such repairs and replacements to the roof, exterior
                    walls, floor slabs and other structural components of the
                    Building, and to the plumbing, electrical, heating,
                    ventilating and air-conditioning systems of the Building as
                    may be necessary to keep them in good repair and condition
                    (exclusive of equipment installed by Tenant and except for
                    those repairs required to be made by Tenant pursuant to
                    Section 6.1.3 hereof and repairs or replacements occasioned
                    by any act or negligence of Tenant, its servants, agents,
                    customers, contractors, employees, invitees, or licensees).

          5.1.6     LANDLORD'S INSURANCE. To take out and maintain throughout
                    the term all-risk casualty insurance in an amount equal to
                    100% of the replacement cost of the Building but
                    specifically excluding the Tenant's Work and any
                    improvements installed by Tenant during the term.

          5.1.7     LANDLORD'S INDEMNIFICATION. To save Tenant harmless, and to
                    exonerate and indemnify Tenant from and against any and all
                    claims, liabilities or penalties asserted by or on behalf of
                    any person, firm, corporation or public authority on account
                    of injury, death, damage or loss to the person or property
                    in or upon the common areas of the Property arising out of
                    the negligence, fault or misconduct of Landlord, its agents,
                    servants, employees or contractors. In respect of all of the
                    foregoing, Landlord shall indemnify Tenant from and against
                    all costs, expenses (including reasonable attorneys' fees),
                    and liabilities incurred in or in connection with any such
                    claim, action or proceeding brought thereon; and, in case of
                    any action or proceeding brought against Tenant by reason of
                    any such claim, Landlord, upon notice from Tenant and at
                    Landlord's expense, shall resist or defend such action or
                    proceeding and employ counsel therefor reasonably
                    satisfactory to Tenant.

5.2       INTERRUPTION. Landlord shall be under no responsibility or liability
          for failure or interruption of any of the above-described services,
          repairs or replacements caused by breakage, accident, strikes,
          repairs, inability to obtain supplies, labor or materials, or for any
          other causes beyond the control of the Landlord, and in no event for
          any indirect or consequential damages to Tenant; and failure or
          omission on the part of the Landlord to furnish any of same for any of
          the reasons set forth in this paragraph shall not be construed as an
          eviction of Tenant, actual or constructive, nor entitle Tenant to an
          abatement of rent, nor render the Landlord liable in damages, nor
          release Tenant from prompt fulfillment of any of its covenants under
          this Lease.

          Notwithstanding the foregoing, if Landlord fails to provide any
          service that it is required to provide above so that Tenant's ability
          to conduct business at the Premises is materially adversely affected
          for a period of five (5) consecutive business days after written
          notice thereof from Tenant to Landlord, then, provided that such
          failure or Landlord's inability to cure such condition is not (i) due
          to a cause beyond Landlord's reasonable control and/or (ii) generally
          affecting other buildings in the vicinity of the Premises (such as a
          neighborhood power outage or a water main break) or a fire or other
          casualty or taking (which shall be governed by Article 7 below) or the
          fault or negligence of Tenant or any of its agents, employees or
          contractors, the Fixed Rent and Additional Rent shall be equitably
          abated based upon the impact thereof on Tenant's ability to conduct
          business in the Premises until such service(s) is restored to their
          level prior to the interruption.

5.3       OUTSIDE SERVICES. In the event Tenant wishes to provide outside
          services for the Premises over and above those services to be provided
          by Landlord as set forth herein, Tenant shall first obtain the prior
          written approval of Landlord for the installation and/or utilization
          of such services ("Outside services" shall include, but shall not be
          limited to, cleaning services, television, so-called "canned music"
          services, security services, catering services and the like.) In the
          event Landlord approves the installation and/or utilization of such
          services, such installation and utilization shall be at Tenant's sole
          cost, risk and expense.

                                    ARTICLE 6

                          TENANT'S ADDITIONAL COVENANTS

6.1       AFFIRMATIVE COVENANTS. Tenant covenants at all times during the term
          and for such further time (prior or subsequent thereto) as Tenant
          occupies the Premises or any part thereof:

          6.1.1     PERFORM OBLIGATIONS.To perform promptly all of the
                    obligations of Tenant set forth in this Lease; and to pay
                    when due the Fixed Rent and Additional Rent and all charges,
                    rates and other sums which by the terms of this Lease are to
                    be paid by Tenant.

          6.1.2     USE. To use the Premises only for the Permitted Uses, and
                    from time to time to procure all licenses and permits
                    necessary therefor, at Tenant's sole expense. As of the Date
                    of this Lease, Landlord represents and warrants that the
                    Permitted Uses are in compliance with all applicable zoning
                    codes With respect to any licenses or permits for which
                    Tenant may apply, pursuant to this subsection 6.1.2 or any
                    other provision hereof, Tenant shall furnish Landlord copies
                    of applications therefor on or before their submission to
                    the governmental authority.

          6.1.3     REPAIR AND MAINTENANCE. To maintain the Premises in neat
                    order and condition and to perform all routine and ordinary
                    repairs to the Premises and to any plumbing, heating,
                    electrical, ventilating and air-conditioning systems
                    installed by Tenant such as are necessary to keep them in
                    good working order, appearance and condition, as the case
                    may require,

                                        8
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                    reasonable use and wear thereof and damage by fire or by
                    unavoidable casualty only excepted; to keep all glass in
                    windows and doors of the Premises (except glass in the
                    exterior walls of the Building) whole and in good condition
                    with glass of the same quality as that injured or broken;
                    and to make as and when needed as a result of misuse by, or
                    neglect or improper conduct of Tenant or Tenant's servants,
                    employees, agents, invitees or licensees or otherwise, all
                    repairs necessary, which repairs and replacements shall be
                    in quality and class equal to the original work. (Landlord,
                    upon default of Tenant hereunder and upon prior notice to
                    Tenant, may elect, at the expense of Tenant, to perform all
                    such cleaning and maintenance and to make any such repairs
                    or to repair any damage or injury to the Building or the
                    Premises caused by moving property of Tenant in or out of
                    the Building, or by installation or removal of furniture or
                    other property, or by misuse by, or neglect, or improper
                    conduct of, Tenant or Tenant's servants, employees, agents,
                    contractors, customers, patrons, invitees, or licensees.)

          6.1.4     COMPLIANCE WITH LAW. To make all repairs, alterations,
                    additions or replacements to the Premises required by any
                    law or ordinance or any order or regulation of any public
                    authority to the extent the same are Tenant's responsibility
                    under this Lease; to keep the Premises equipped with all
                    safety appliances so required; and to comply with the orders
                    and regulations of all governmental authorities with respect
                    to zoning, building, fire, health and other codes,
                    regulations, ordinances or laws applicable to Tenant's
                    particular use of the Premises, except that Tenant may defer
                    compliance so long as the validity of any such law,
                    ordinance, order or regulations shall be contested by Tenant
                    in good faith and by appropriate legal proceedings, if
                    Tenant first gives Landlord appropriate assurance or
                    security against any loss, cost or expense on account
                    thereof.

          6.1.5     INDEMNIFICATION. To save harmless, exonerate and indemnify
                    Landlord, its agents (including, without limitation,
                    Landlord's managing agent) and employees (such agents and
                    employees being referred to collectively as the "Landlord
                    Related Parties") from and against any and all claims,
                    liabilities or penalties asserted by or on behalf of any
                    person, firm, corporation or public authority on account of
                    injury, death, damage or loss to person or property in or
                    upon the Premises and the Property arising out of the use or
                    occupancy of the Premises by Tenant or by any person
                    claiming by, through or under Tenant (including, without
                    limitation, all patrons, employees and customers of Tenant),
                    or arising out of any delivery to or service supplied to the
                    Premises, or on account of or based upon anything whatsoever
                    done on the Premises, except if the same was caused by the
                    willful negligence, fault or misconduct of Landlord or the
                    Landlord Related Parties. In respect of all of the
                    foregoing, Tenant shall indemnify Landlord and the Landlord
                    Related Parties from and against all costs, expenses
                    (including reasonable attorneys' fees), and liabilities
                    incurred in or in connection with any such claim, action or
                    proceeding brought thereon; and, in case of any action or
                    proceeding brought against Landlord or the Landlord Related
                    Parties by reason of any such claim, Tenant, upon notice
                    from Landlord and at Tenant's expense, shall resist or
                    defend such action or proceeding and employ counsel therefor
                    reasonably satisfactory to Landlord.

          6.1.6     LANDLORD'S RIGHT TO ENTER. To permit Landlord and its agents
                    to enter into and examine the Premises at reasonable times
                    and to show the Premises, and to make repairs to the
                    Premises and to install, use and repair telecommunications
                    equipment on the roof of the Building, provided that
                    Landlord agrees not to unreasonably interfere with Tenant's
                    use of the Premises while exercising its right to enter
                    pursuant to this subsection 6.1.6, and, during the last six
                    (6) months prior to the expiration of this Lease, to keep
                    affixed in suitable places notices of availability of the
                    Premises. Except in the case of an emergency, Landlord shall
                    use reasonable efforts to provide Tenant with notice prior
                    to Landlord exercising its right to enter the Premises
                    pursuant to this subsection 6.1.6. However, notwithstanding
                    the foregoing, Landlord shall give Tenant reasonable prior
                    notice whenever Landlord requires access to the Premises to
                    show the Premises.

          6.1.7     PERSONAL PROPERTY AT TENANT'S RISK. All of the furnishings,
                    fixtures, equipment, effects and property of every kind,
                    nature and description of Tenant and of all persons claiming
                    by, through or under Tenant which, during the continuance of
                    this Lease or any occupancy of the Premises by Tenant or
                    anyone claiming under Tenant, may be on the Premises, shall
                    be at the sole risk and hazard of Tenant and if the whole or
                    any part thereof shall be destroyed or damaged by fire,
                    water or otherwise, or by the leakage or bursting of water
                    pipes, steam pipes, or other pipes, by theft or from any
                    other cause, no part of said loss or damage is to be charged
                    to or to be borne by Landlord, except that Landlord shall in
                    no event be indemnified or held harmless or exonerated from
                    any liability to Tenant or to any other person, for any
                    injury, loss, damage or liability to the extent prohibited
                    by law.

          6.1.8     PAYMENT OF LANDLORD'S COST OF ENFORCEMENT. To pay on demand
                    Landlord's expenses, including reasonable attorneys' fees,
                    incurred in enforcing any obligation of Tenant under this
                    Lease or in curing any default by Tenant under this Lease as
                    provided in Section 8.4.

          6.1.9     YIELD UP. At the expiration of the term or earlier
                    termination of this Lease: to surrender all keys to the
                    Premises; to remove all of its trade fixtures and personal
                    property in the Premises; to deliver to Landlord stamped
                    architectural plans showing the Premises at yield up (which
                    may be the initial plans if Tenant has made no installations
                    after the Commencement Date); to remove such installations
                    made by it as Landlord may request (including computer and
                    telecommunications wiring and cabling, it being understood
                    that if Tenant leaves such wiring and cabling in a useable
                    condition, Landlord, although having the right to request
                    removal thereof, is less likely to so request) and all
                    Tenant's signs wherever located; to repair all damage caused
                    by such removal and to yield up the Premises (including all
                    installations and improvements made by Tenant except for
                    trade fixtures and such of said installations or
                    improvements as Landlord shall request Tenant to remove),
                    broom-clean and in the same good order and repair in which
                    Tenant is obliged to keep and maintain the Premises by the
                    provisions of this Lease, reasonable wear and tear, and
                    damage by casualty and condemnation excepted. Tenant, at the
                    time of making any installation, may request in writing
                    Landlord's written permission to leave such installation in
                    the Premises at the expiration or earlier termination of
                    this Lease, and if Landlord so notifies Tenant that such
                    installation may remain in the Premises at the expiration or
                    earlier termination of this Lease, then Landlord shall
                    thereafter not be permitted to request or require that such
                    installation be removed at the expiration or earlier
                    termination of the Lease. Any property not so removed shall
                    be deemed abandoned and, if Landlord so elects, deemed to be
                    Landlord's property, and may be retained or removed and
                    disposed of by Landlord in such manner as Landlord shall
                    determine and Tenant shall pay Landlord the entire cost and
                    expense incurred by it in effecting such removal and
                    disposition and in making any incidental repairs and
                    replacements to the Premises and for use and occupancy
                    during the period after the expiration of the term and prior
                    to its performance of its obligations under this subsection
                    6.1.9. Tenant shall further indemnify Landlord against all
                    loss, cost and damage resulting from Tenant's failure and
                    delay in surrendering the Premises as above provided.
                    Landlord hereby confirms that the Landlord's Work (defined
                    in Article 3) shall not be required to be removed by Tenant
                    at the end of the term.

                    Once Tenant submits plans for Tenant's Work to Landlord for
                    Landlord's approval, Landlord will identify those portions
                    of Tenant's Work which Tenant will be permitted to leave in
                    the Premises at the end of the term, which identified
                    portions of Tenant's Work will be itemized in an exhibit
                    entitled "Initial Tenant's Work" prepared by Landlord and
                    attached to this Lease as Exhibit H.

                    If the Tenant remains in the Premises beyond the expiration
                    or earlier termination of this Lease, such holding over
                    shall be without right and shall not be deemed to create any
                    tenancy, but the Tenant shall be a tenant at sufferance only
                    at a daily rate of rent equal to two (2) times the rent and
                    other charges in effect under this Lease as of the day prior
                    to the date of expiration of this Lease.

          6.1.10    RULES AND REGULATIONS. To comply with the Rules and
                    Regulations set forth in Exhibit F, and with all reasonable
                    Rules and Regulations hereafter made by Landlord, of which
                    Tenant has been given notice.

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          6.1.11    ESTOPPEL CERTIFICATE. Upon not less than ten (10) days'
                    prior written request by Landlord, to execute, acknowledge
                    and deliver to Landlord a statement in writing, which may be
                    in the form attached hereto as Exhibit G or in another form
                    reasonably similar thereto, or such other form as Landlord
                    may provide from time to time, certifying all or any of the
                    following: (i) that this Lease is unmodified and in full
                    force and effect, (ii) whether the term has commenced and
                    Fixed Rent and Additional Rent have become payable hereunder
                    and, if so, the dates to which they have been paid, (iii)
                    whether or not Landlord is in default in performance of any
                    of the terms of this Lease, (iv) whether Tenant has accepted
                    possession of the Premises, (v) whether Tenant has made any
                    claim against Landlord under this Lease and, if so, the
                    nature thereof and the dollar amount, if any, of such claim,
                    (vi) whether there exist any offsets or defenses against
                    enforcement of any of the terms of this Lease upon the part
                    of Tenant to be performed, and (vii) such further
                    information with respect to the Lease or the Premises as
                    Landlord may reasonably request. Any such statement
                    delivered pursuant to this subsection 6.1 .I 1 may be relied
                    upon by any prospective purchaser or mortgagee of the
                    Premises, or any prospective assignee of such mortgage.
                    Tenant shall also deliver to Landlord such financial
                    information as may be reasonably required by Landlord to be
                    provided to any mortgagee or prospective purchaser of the
                    Premises, provided, further that the party provided with
                    such financial information agrees in a written document
                    reasonably acceptable to such party to keep the financial
                    information confidential.

          6.1.12    LANDLORD'S EXPENSES RE CONSENTS. To reimburse Landlord
                    promptly on demand for all reasonable legal expenses
                    incurred by Landlord in connection with all requests by
                    Tenant for consent or approval hereunder.

          6.1.13    CLEANING. Tenant shall clean the Premises in accordance with
                    cleaning and janitorial standards generally prevailing
                    throughout the term hereof in comparable office buildings
                    within the municipality in which the Building is located.

6.2       NEGATIVE COVENANTS. Tenant covenants at all times during the term and
          such further time (prior or subsequent thereto) as Tenant occupies the
          Premises or any part thereof:

          6.2.1     ASSIGNMENT AND SUBLETTING. Not to assign, transfer, mortgage
                    or pledge this Lease or to sublease (which term shall be
                    deemed to include the granting of concessions and licenses
                    and the like) all or any part of the Premises or suffer or
                    permit this Lease or the leasehold estate hereby created or
                    any other rights arising under this Lease to be assigned,
                    transferred or encumbered, in whole or in part, whether
                    voluntarily, involuntarily or by operation of law, or permit
                    the occupancy of the Premises by anyone other than Tenant
                    without the prior written consent of Landlord except for
                    Permitted Transfers (as hereinafter defined). In the event
                    Tenant desires to assign this Lease or sublet any portion or
                    all of the Premises, Tenant shall notify Landlord in writing
                    of Tenant's intent to so assign this Lease or sublet the
                    Premises and the proposed effective date of such subletting
                    or assignment, and shall request in such notification that
                    Landlord consent thereto. Except in the case of a Permitted
                    Transfer, Landlord may terminate this Lease in the case of a
                    proposed assignment, or suspend this Lease pro tanto for the
                    period and with respect to the space involved in the case of
                    a proposed subletting, by giving written notice of
                    termination or suspension to Tenant within thirty (30) days
                    of Tenant's notification to Landlord of Tenant's intent to
                    sublease or assign as aforesaid, with such termination or
                    suspension to be effective as of the effective date of such
                    assignment or subletting. If Tenant then chooses not to
                    assign or sublet, then such termination or suspension shall
                    not be effective as to that particular transaction for which
                    Tenant delivered notice of its intent to sublease or assign.
                    If Landlord does not so terminate or suspend, Landlord's
                    consent shall not be unreasonably withheld, conditioned or
                    delayed to an assignment or to a subletting, provided that
                    the following conditions are met:

                    1)      the assignee or subtenant shall use the Premises
                            only for the Permitted Uses or for any one of the
                            non-ancillary Permitted Uses individually;

                    (ii)    the proposed assignee or subtenant has a net worth
                            and creditworthiness reasonably acceptable to
                            Landlord;

                    (iii)   the amount of the aggregate rent to be paid by the
                            proposed subtenant is not less than the then current
                            market rate for comparable subleases of premises
                            substantially similar to the Premises; and

                    (iv)    the proposed assignee or subtenant is not then a
                            tenant in the Building or the Park, or an entity
                            with which Landlord is currently in negotiations
                            with or has negotiated with within the preceding six
                            months regarding the possibility of leasing space in
                            the Building or the Park.

                    Tenant shall furnish Landlord with any information
                    reasonably requested by Landlord to enable Landlord to
                    determine whether the proposed assignment or subletting
                    complies with the foregoing requirements, including without
                    limitation, financial statements relating to the proposed
                    assignee or subtenant.

                    Tenant shall, as Additional Rent, reimburse Landlord
                    promptly for Landlord's reasonable legal expenses incurred
                    in connection with any request by Tenant for such consent.
                    If Landlord consents thereto, or in the case of a Permitted
                    Transfer, no such subletting or assignment shall in any way
                    impair the continuing primary liability of Tenant hereunder
                    (unless otherwise explicitly agreed to by Landlord in its
                    consent), and no consent to any subletting or assignment in
                    a particular instance shall be deemed to be a waiver of the
                    obligation to obtain the Landlord's written approval in the
                    case of any other subletting or assignment.

                    If for any assignment or sublease consented to by Landlord
                    hereunder Tenant receives rent or other consideration,
                    either initially or over the term of the assignment or
                    sublease, in excess of the rent called for hereunder, or in
                    case of sublease of part, in excess of such rent fairly
                    allocable to the part, after appropriate adjustments to
                    assure that all other payments called for hereunder are
                    appropriately taken into account and after deduction for
                    Tenant's reasonable expenses incurred in connection with the
                    assignment or sublease (provided, however, all such costs
                    shall be amortized over the term of the sublease in
                    question), including brokerage commissions, marketing
                    expenses, tenant inducements consistent with inducements
                    being made by other similar tenants subletting or assigning
                    its lease for comparable premises in the Burlington area,
                    reasonable attorney's fees, and advertising fees, to pay to
                    Landlord as additional rent fifty (50%) percent of the
                    excess of each such payment of rent or other consideration
                    received by Tenant promptly after its receipt.

                    Whenever Tenant lists with a broker or brokers or otherwise
                    advertises, holds out or markets the Premises or any part
                    thereof for sublease or assignment, Tenant shall give
                    Nordblom Company, as brokers, a non-exclusive listing with
                    respect to such sublease or assignment.

                    If at any time during the term of this Lease, there is a
                    name change, reformation or reorganization of the Tenant
                    entity, Tenant shall so notify Landlord and deliver evidence
                    reasonably satisfactory to Landlord documenting such name
                    change, reformation or reorganization. If, at any time
                    during the term of this Lease, there is a transfer of a
                    controlling interest in the stock, membership or general
                    partnership interests of Tenant, Tenant shall so notify
                    Landlord and any such transfer shall be deemed an assignment
                    of this Lease.

                    With respect to any assignment or subletting during the
                    original term of this Lease, such assignment shall not
                    include the right granted to Tenant under Section 2.3
                    hereinabove to extend the term, and such sublease shall be
                    for a term expiring no later than the Expiration Date.

                    Notwithstanding the foregoing provisions of this Subsection
                    6.2.1, Tenant may assign this Lease or sublet the Premises,
                    without Landlord's consent, to any entity (a) which controls
                    or is controlled by or is under common control with Tenant;
                    or (b) which purchases all or substantially all of Tenant's
                    stock or assets; or (c) with or into which Tenant is merged
                    or consolidated, provided that (i) the assignee or sublessee
                    agrees to assume and perform, in full, the obligations of
                    Tenant

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                    under this Lease by written instrument in form satisfactory
                    to Landlord, which instrument shall be delivered to Landlord
                    at least fifteen (15) days prior to the effective date of
                    any such transaction, (ii) Tenant remains fully and
                    primarily liable under this Lease (unless otherwise agreed
                    to at the time), (iii) the use of the Premises remains
                    unchanged, (iv) the successor to Tenant has a net worth
                    computed in accordance with generally accepted accounting
                    principles at least equal to or greater than the net worth
                    of Tenant immediately prior to such merger, consolidation,
                    transfer or transaction permitted herein, and further
                    provided that proof reasonably satisfactory to Landlord of
                    such net worth shall have been delivered to Landlord at
                    least fifteen (15) days prior to the effective date of any
                    such transaction (the "Permitted Transfer").

          6.2.2     NUISANCE. Not to injure, deface or otherwise harm the
                    Premises; nor commit any nuisance; nor permit in the
                    Premises any vending machine (except such as is used for the
                    sale of merchandise to employees of Tenant) or inflammable
                    fluids or chemicals (except such as are customarily used in
                    connection with standard office equipment); nor permit any
                    cooking to such extent as requires special exhaust venting;
                    nor permit the emission of any objectionable noise or odor;
                    nor make, allow or suffer any waste; nor make any use of the
                    Premises which is improper, offensive or contrary to any law
                    or ordinance or which will invalidate any of Landlord's
                    insurance; nor conduct any auction, fire, "going out of
                    business" or bankruptcy sales.

          6.2.3     HAZARDOUS WASTES AND MATERIALS. Not to dispose of any
                    hazardous wastes, hazardous materials or oil on the Premises
                    or the Property, or into any of the plumbing, sewage, or
                    drainage systems thereon, and to indemnify and save Landlord
                    harmless from all claims, liability, loss or damage arising
                    on account of the use or disposal of hazardous wastes,
                    hazardous materials or oil, including, without limitation,
                    liability under any federal, state, or local laws,
                    requirements and regulations, or damage to any of the
                    aforesaid systems. Tenant shall comply with all governmental
                    reporting requirements with respect to hazardous wastes,
                    hazardous materials and oil, and shall deliver to Landlord
                    copies of all reports filed with governmental authorities.

          6.2.4     FLOOR LOAD: HEAVY EQUIPMENT. Not to place a load upon any
                    floor of the Premises exceeding the floor load per square
                    foot area which such floor was designed to carry and which
                    is allowed by law. Landlord reserves the right to prescribe
                    the weight and position of all heavy business machines and
                    equipment, including safes, which shall be placed so as to
                    distribute the weight. Business machines and mechanical
                    equipment which cause vibration or noise shall be placed and
                    maintained by Tenant at Tenant's expense in settings
                    sufficient to absorb and prevent vibration, noise and
                    annoyance. Tenant shall not move any safe, heavy machinery,
                    heavy equipment, freight or fixtures into or out of the
                    Premises except in such manner and at such time as Landlord
                    shall in each instance authorize.

          6.2.5     INSTALLATION. ALTERATIONS OR ADDITIONS. Not to make any
                    installations, alterations or additions in, to or on the
                    Premises nor to permit the making of any holes in the walls
                    (except for normal office wall hangings, pictures, and the
                    like), partitions, ceilings or floors nor the installation
                    or modification of any locks or security devices without on
                    each occasion obtaining the prior written consent of
                    Landlord, and then only pursuant to plans and specifications
                    approved by Landlord in advance in each instance (which
                    consent and approval shall not be required for alterations
                    (i) that cost less than $5,000.00 and which do not alter the
                    Premises floor plan or impact the systems or structure of
                    the Building, or (ii) which are decorative or cosmetic in
                    nature, such as painting and carpeting); Tenant shall pay
                    promptly when due the entire cost of any work to the
                    premises undertaken by Tenant so that the Premises shall at
                    all times be free of liens for labor and materials, and at
                    Landlord's request Tenant shall furnish to Landlord a bond
                    or other security acceptable to Landlord assuring that any
                    work in excess of $5,000.00 commenced by Tenant will be
                    completed in accordance with the plans and specifications
                    theretofore approved by Landlord and assuring that the
                    Premises will remain free of any mechanics' lien or other
                    encumbrance arising out of such work. In any event, Tenant
                    shall forthwith bond against or discharge any mechanics'
                    liens or other encumbrances that may arise out of such work.
                    Tenant shall procure all necessary licenses and permits at
                    Tenant's sole expense before undertaking such work. All such
                    work shall be done in a good and workmanlike manner
                    employing materials of good quality and so as to conform
                    with all applicable zoning, building, fire, health and other
                    codes, regulations, ordinances and laws. Tenant shall save
                    Landlord harmless and indemnified from all injury, loss,
                    claims or damage to any person or property occasioned by or
                    growing out of such work.

                    Except for security interests granted prior to the Date of
                    this Lease, not to grant a security interest in, or to
                    lease, any personal property being installed in the Premises
                    (including, without limitation, demountable partitions)
                    without first obtaining an agreement, for the benefit of
                    Landlord, from the secured party or lessor that such
                    property will be removed within ten (10) business days after
                    notice from Landlord of the expiration or earlier
                    termination of this Lease and that a failure to so remove
                    will subject such property to the provisions of subsection
                    6.1.9 of the Lease. In the event a security interest in
                    personal property has been granted by Tenant prior to the
                    Date of this Lease and Tenant has on or before the Date of
                    this Lease provided written notice to Landlord identifying
                    the Secured Party holding such security interest (which
                    notice shall contain such information reasonably requested
                    by Landlord), Landlord shall notify said Secured Party of
                    the expiration or early termination of this Lease and shall
                    provide said Secured Party with ten (10) business days to
                    remove the personal property from the Premises after the
                    expiration or early termination of this Lease. If Tenant
                    fails to provide such notice to Landlord as aforesaid,
                    Landlord shall not be obligated to provide any notice to the
                    Secured Party as aforesaid and such property upon the
                    expiration or earlier termination of the Lease shall be
                    subject to the provisions of subsection 6.1.9.

          6.2.6     ABANDONMENT. Not to vacate the Premises during the term.

          6.2.7     SIGNS. Not without Landlord's prior written approval, which
                    approval shall not be unreasonably withheld, to paint or
                    place any signs or place any curtains, blinds, shades,
                    awnings, aerials, or the like, visible from outside the
                    Premises. Notwithstanding the foregoing, Tenant may erect
                    one (1) identifying sign on the Building facing the interior
                    of the Park and one (I) identifying sign on the Building
                    facing Route 3, provided any and all such signage complies
                    with the signage policy for Northwest Park and is in
                    compliance with all laws. All signage shall be at Tenant's
                    sole cost and expense and shall be maintained in good repair
                    by Tenant.

          6.2.8     PARKING AND STORAGE. Not to permit any storage of materials
                    outside of the Premises; nor to permit the use of the
                    parking areas for either temporary or permanent storage of
                    trucks; nor permit the use of the Premises for any use for
                    which heavy trucking would be customary.

                                    ARTICLE 7

                               CASUALTY OR TAKING

7.1       TERMINATION. A. In the event that the Premises, or any material part
          thereof, shall be taken by any public authority or for any public use,
          or shall be destroyed or damaged by fire or casualty, or by the action
          of any public authority, then this Lease may be terminated at the
          election of Landlord. Such election, which may be made notwithstanding
          the fact that Landlord's entire interest may have been divested, shall
          be made by the giving of notice by Landlord to Tenant within sixty
          (60) days after the date of the taking or casualty.

          B. In the event that the Premises are destroyed or damaged by fire or
          casualty, or by the action of public authority, and, in the reasonable
          opinion of an independent architect or engineer selected by Landlord,
          cannot be repaired or restored within two hundred seventy (270) days
          from the date of the casualty or taking, then this Lease may be
          terminated at the election of Landlord or Tenant, which election shall
          be made by the giving of notice to the other party within thirty (30)
          days after the date the opinion of the architect or engineer is made
          available to the parties. Landlord shall use reasonable efforts to
          obtain the estimate of the time for restoration

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          within thirty (30) days after the casualty or taking, but in any event
          shall provide such estimate within sixty (60) days after the taking or
          casualty.

7.2       RESTORATION. If neither party elects to so terminate as provided in
          this Article 7, this Lease shall continue in force and a just
          proportion of the rent reserved, according to the nature and extent of
          the damages sustained by the Premises, shall be suspended or abated
          until the Premises, or what may remain thereof, shall be put by
          Landlord in proper condition for use, which Landlord covenants to do
          with reasonable diligence to the extent permitted by the net proceeds
          of insurance recovered or damages awarded for such taking, destruction
          or damage and subject to zoning and building laws or ordinances then
          in existence. Landlord's restoration work shall exclude the Tenant's
          Work and any other improvements or installations made by or on behalf
          of Tenant. "Net proceeds of insurance recovered or damages awarded"
          refers to the gross amount of such insurance or damages less the
          reasonable expenses of Landlord incurred in connection with the
          collection of the same, including without limitation, fees and
          expenses for legal and appraisal services. If Landlord shall not have
          restored the Premises within two hundred seventy (270) days from the
          date of the taking or casualty, Tenant shall have the right to
          terminate this Lease by giving notice of such termination to Landlord,
          to be effective at the expiration of thirty (30) days from the giving
          of such notice; provided however, that such termination will be
          rendered ineffective if, prior to the expiration of said 30-day
          period, Landlord shall have completed such restoration.

7.3       AWARD. Irrespective of the form in which recovery may be had by law,
          all rights to damages or compensation shall belong to Landlord in all
          cases, except in the case of a taking by a public authority, awards
          made to Tenant for its personal property, fixtures and relocation
          expenses. Except for such awards, Tenant hereby grants to Landlord all
          of Tenant's rights to such damages and covenants to deliver such
          further assignments thereof as Landlord may from time to time request.

                                    ARTICLE 8

                                    DEFAULTS

8.1       EVENTS OF DEFAULT. (a) If Tenant shall default in the performance of
          any of its obligations to pay the Fixed Rent, Additional Rent or any
          other sum due Landlord hereunder and if such default shall continue
          for ten (10) days after written notice from Landlord designating such
          default or if within thirty (30) days after written notice from
          Landlord to Tenant specifying any other default or defaults Tenant has
          not commenced diligently to correct the default or defaults so
          specified or has not thereafter diligently pursued such correction to
          completion, or (b) if any assignment shall be made by Tenant or any
          guarantor of Tenant for the benefit of creditors, or (c) if Tenant's
          leasehold interest shall be taken on execution, or (d) if a lien or
          other involuntary encumbrance is filed against Tenant's leasehold
          interest or Tenant's other property (other than a landlord's lien),
          including said leasehold interest, and is not discharged within ten
          (10) days thereafter or otherwise dealt with to the satisfaction of
          Landlord, or (e) if a petition is filed by Tenant or any guarantor of
          Tenant for liquidation, or for reorganization or an arrangement under
          any provision of any bankruptcy law or code as then in force and
          effect, or (f) if an involuntary petition under any of the provisions
          of any bankruptcy law or code is filed against Tenant or any guarantor
          of Tenant and such involuntary petition is not dismissed within sixty
          (60) days thereafter, then, and in any of such cases, Landlord and the
          agents and servants of Landlord lawfully may, in addition to and not
          in derogation of any remedies for any preceding breach of covenant,
          immediately or at any time thereafter without demand or notice and
          with process of law enter into and upon the Premises or any part
          thereof in the name of the whole or mail a notice of termination
          addressed to Tenant, and repossess the same as of landlord's former
          estate and expel Tenant and those claiming through or under Tenant and
          remove its and their effects (forcibly, if necessary) without being
          deemed guilty of any manner of trespass and without prejudice to any
          remedies which might otherwise be used for arrears of rent or prior
          breach of covenants, and upon such entry or mailing as aforesaid this
          Lease shall terminate, Tenant hereby waiving all statutory rights to
          the Premises (including without limitation rights of redemption, if
          any, to the extent such rights may be lawfully waived) and Landlord,
          without notice to Tenant, may store Tenant's effects, and those of any
          person claiming through or under Tenant, at the expense and risk of
          Tenant, and, if Landlord so elects, may sell such effects at public
          auction or private sale and apply the net proceeds to the payment of
          all sums due to Landlord from Tenant, if any, and pay over the
          balance, if any, to Tenant.

8.2       REMEDIES. In the event that this Lease is terminated under any of the
          provisions contained in Section 8.1 or shall be otherwise terminated
          for breach of any obligation of Tenant, Tenant covenants to pay
          forthwith to Landlord, as compensation, the excess of the total rent
          reserved for the residue of the term over the rental value of the
          Premises for said residue of the term. In calculating the rent
          reserved there shall be included, in addition to the Fixed Rent and
          Additional Rent, the value of all other considerations agreed to be
          paid or performed by Tenant for said residue. Tenant further covenants
          as additional and cumulative obligations after any such termination,
          to pay punctually to Landlord all the sums and to perform all the
          obligations which Tenant covenants in this Lease to pay and to perform
          in the same manner and to the same extent and at the same time as if
          this Lease had not been terminated. In calculating the amounts to be
          paid by Tenant pursuant to the next preceding sentence Tenant shall be
          credited with any amount paid to Landlord as compensation as in this
          Section 8.2 provided and also with the net proceeds of any rent
          obtained by Landlord by reletting the Premises, after deducting all
          Landlord's expense in connection with such reletting, including,
          without limitation, all repossession costs, brokerage commissions,
          reasonable fees for legal services, and expenses of preparing the
          Premises for such reletting, it being agreed by Tenant that Landlord
          shall (i) use reasonable efforts to relet the Premises or any part or
          parts thereof, for a term or terms which may at Landlord's option be
          equal to or less than or exceed the period which would otherwise have
          constituted the balance of the term and may grant such concessions and
          free rent as Landlord in its sole judgment considers advisable or
          necessary to relet the same and (ii) make such alterations, repairs
          and decorations in the Premises as Landlord in its sole judgment
          considers advisable or necessary to relet the same, and no action of
          Landlord in accordance with the foregoing or failure to relet or to
          collect rent under reletting shall operate or be construed to release
          or reduce Tenant's liability as aforesaid. For the purposes of this
          paragraph, marketing of the Premises in a manner similar to the way
          Landlord markets its other premises in the suburban market shall be
          deemed to satisfy Landlord's obligation to use such "reasonable
          efforts." In no event shall Landlord be required (i) to solicit or
          entertain negotiations with any other prospective tenants for the
          Premises until Landlord obtains full and complete possession of the
          Premises including, without limitation, the undisputed right to re-let
          the Premises free of any claim of Tenant, (ii) to lease the Premises
          to a tenant whose proposed use, in Landlord's sole but bona fide
          judgment, would violate any restrictions by which Landlord is bound,
          (iii) to re-let the Premises before leasing other comparable vacant
          space in the Building, (iv) to lease the Premises for a rental less
          than the current fair market rental then prevailing for similar office
          space in the Building, or (v) to enter into a lease with any proposed
          tenant that does not have, in Landlord's reasonable opinion,
          sufficient financial resources or operating experience to operate the
          Premises in a manner comparable to other tenants in the Building. In
          no event, however, shall Tenant's liability hereunder be diminished or
          reduced if or to the extent such reasonable efforts of Landlord to
          re-let are not successful.

          Nothing contained in this Lease shall limit or prejudice the right of
          Landlord to prove for and obtain in proceedings for bankruptcy or
          insolvency by reason of the termination of this Lease, an amount equal
          to the maximum allowed by any statute or rule of law in effect at the
          time when, and governing the proceedings in which, the damages are to
          be proved, whether or not the amount be greater than, equal to, or
          less than the amount of the loss or damages referred to above.

8.3       REMEDIES CUMULATIVE. Any and all rights and remedies which Landlord
          may have under this Lease, and at law and equity, shall be cumulative
          and shall not be deemed inconsistent with each other, and any two or
          more of all such rights and remedies may be exercised at the same time
          insofar as permitted by law.

8.4       LANDLORD'S RIZHT TO CURE DEFAULTS. Landlord may, but shall not be
          obligated to, cure, at any time in emergency situations and after the
          expiration of all applicable grace periods hereunder in all other
          cases, without notice, any default by Tenant under this Lease; and

                                       12
<Page>

          whenever Landlord so elects, all costs and expenses incurred by
          Landlord, including reasonable attorneys' fees, in curing a default
          shall be paid, as Additional Rent, by Tenant to Landlord on demand,
          together with lawful interest thereon from the date of payment by
          Landlord to the date of payment by Tenant.

8.5       EFFECT OF WAIVERS OF DEFAULT. Any consent or permission by Landlord to
          any act or omission which otherwise would be a breach of any covenant
          or condition herein, shall not in any way be held or construed (unless
          expressly so declared) to operate so as to impair the continuing
          obligation of any covenant or condition herein, or otherwise, except
          as to the specific instance, operate to permit similar acts or
          omissions.

8.6       NO WAIVER. ETC. The failure of Landlord to seek redress for violation
          of, or to insist upon the strict performance of, any covenant or
          condition of this Lease shall not be deemed a waiver of such violation
          nor prevent a subsequent act, which would have originally constituted
          a violation, from having all the force and effect of an original
          violation. The receipt by Landlord of rent with knowledge of the
          breach of any covenant of this Lease shall not be deemed to have been
          a waiver of such breach by Landlord. No consent or waiver, express or
          implied, by Landlord to or of any breach of any agreement or duty
          shall be construed as a waiver or consent to or of any other breach of
          the same or any other agreement or duty.

8.7       NO ACCORD AND SATISFACTION. No acceptance by Landlord of a lesser sum
          than the Fixed Rent, Additional Rent or any other charge then due
          shall be deemed to be other than on account of the earliest
          installment of such rent or charge due, nor shall any endorsement or
          statement on any check or any letter accompanying any check or payment
          as rent or other charge 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 such installment or pursue
          any other remedy in this Lease provided.

                                    ARTICLE 9

                           RIGHTS OF MORTGAGE HOLDERS

9.1       RIGHTS OF MORTGAGE HOLDERS. The word "mortgage" as used herein
          includes mortgages, deeds of trust or other similar instruments
          evidencing other voluntary liens or encumbrances, and modifications,
          consolidations, extensions, renewals, replacements and substitutes
          thereof. The word "holder" shall mean a mortgagee, and any subsequent
          holder or holders of a mortgage. Until the holder of a mortgage shall
          enter and take possession of the Property for the purpose of
          foreclosure, such bolder shall have only such rights of Landlord as
          are necessary to preserve the integrity of this Lease as security.
          Upon entry and taking possession of the Property for the purpose of
          foreclosure, such holder shall have all the rights of Landlord. No
          such holder of a mortgage shall be liable either as mortgagee or as
          assignee, to perform, or be liable in damages for failure to perform,
          any of the obligations of Landlord unless and until such holder shall
          enter and take possession of the Property for the purpose of
          foreclosure. Upon entry for the purpose of foreclosure, such holder
          shall be liable to perform all of the obligations of Landlord, subject
          to and with the benefit of the provisions of Section 10.4, provided
          that a discontinuance of any foreclosure proceeding shall be deemed a
          conveyance under said provisions to the owner of the equity of the
          Property.

          The covenants and agreements contained in this Lease with respect to
          the rights, powers and benefits of a holder of a mortgage
          (particularly, without limitation thereby, the covenants and
          agreements contained in this Section 9.1) constitute a continuing
          offer to any person, corporation or other entity, which by accepting a
          mortgage subject to this Lease, assumes the obligations herein set
          forth with respect to such holder; such holder is hereby constituted a
          party of this Lease as an obligee hereunder to the same extent as
          though its name were written hereon as such; and such holder shall be
          entitled to enforce such provisions in its own name. Tenant agrees on
          request of Landlord to execute and deliver from time to time any
          agreement which may be necessary to implement the provisions of this
          Section 9.1.

9.2       LEASE SUPERIOR OR SUBORDINATE TO MORTGAGES. It is agreed that the
          rights and interest of Tenant under this Lease shall be (i) subject or
          subordinate to any present or future mortgage or mortgages and to any
          and all advances to be made thereunder, and to the interest of the
          holder thereof in the Premises or any property of which the Premises
          are a part if Landlord shall elect by notice to Tenant to subject or
          subordinate the rights and interest of Tenant under this Lease to such
          mortgage or (ii) prior to any present or future mortgage or mortgages,
          if Landlord shall elect, by notice to Tenant, to give the rights and
          interest of Tenant under this Lease priority to such mortgage; in the
          event of either of such elections and upon notification by Landlord to
          that effect, the rights and interest of Tenant under this Lease should
          be deemed to be subordinate to, or have priority over, as the case may
          be, said mortgage or mortgages, irrespective of the time of execution
          or time of recording of any such mortgage or mortgages (provided that,
          in the case of subordination of this Lease to any future mortgages,
          the holder thereof agrees not to disturb the possession of Tenant so
          long as Tenant is not in default hereunder and Tenant and the holder
          execute a so-called subordination, non-disturbance and attornment
          agreement in the holder's usual and customary form, with such
          commercially reasonable changes that are acceptable to the parties).
          Tenant agrees it will, upon not less than ten (10) days' prior written
          request by Landlord, execute, acknowledge and deliver any and all
          instruments deemed by Landlord necessary or desirable to give effect
          to or notice of such subordination or priority. Any mortgage to which
          this Lease shall be subordinated may contain such terms, provisions
          and conditions as the holder deems usual or customary.

                                   ARTICLE 10

                            MISCELLANEOUS PROVISIONS

10.1      NOTICES FROM ONE PARTV TO THE OTHER. All notices required or permitted
          hereunder shall be in writing and addressed, if to the Tenant, at the
          Original Notice Address of Tenant or such other address as Tenant
          shall have last designated by notice in writing to Landlord and, if to
          Landlord, at the Original Notice Address of Landlord or such other
          address as Landlord shall have last designated by notice in writing to
          Tenant. Any notice shall be deemed duly given when mailed to such
          address postage prepaid, by registered or certified mail, return
          receipt requested, or when delivered to such address by hand.

10.2      QUIET ENJOYMENT. Landlord agrees that upon Tenant's paying the rent
          and performing and observing the agreements, conditions and other
          provisions on its part to be performed and observed, Tenant shall and
          may peaceably and quietly have, hold and enjoy the Premises during the
          term hereof without any manner of hindrance or molestation from
          Landlord or anyone claiming under Landlord, subject, however, to the
          terms of this Lease.

10.3      LEASE NOT TO BE RECORDED. Tenant agrees that it will not record this
          Lease. Both parties shall, upon the request of either, execute and
          deliver a notice or short form of this Lease in such form, if any, as
          may be permitted by applicable statute.

10.4      LIMITATION OF LANDLORD'S LIABILITY. The term "Landlord" as used in
          this Lease, so far as covenants or obligations to be performed by
          Landlord are concerned, shall be limited to mean and include only the
          owner or owners at the time in question of the Property, and in the
          event of any transfer or transfers of title to said property, the
          Landlord (and in case of any subsequent transfers or conveyances, the
          then grantor) shall be concurrently freed and relieved from and after
          the date of such transfer or conveyance, without any further
          instrument or agreement of all liability as respects the performance
          of any covenants or obligations on the part of the Landlord contained
          in this Lease thereafter to be performed. Tenant, its successors and
          assigns, shall not assert nor seek to enforce any claim for breach
          of this Lease against any of Landlord's assets other than Landlord's
          interest in the Property and in the rents, issues and profits
          thereof, and Tenant agrees to look solely to such interest for the
          satisfaction of any liability or claim against Landlord under this
          Lease, it being specifically agreed that in no event whatsoever shall
          Landlord (which term shall include, without limitation, any

                                       13
<Page>

          general or limited partner, trustees, beneficiaries, officers,
          directors, or stockholders of Landlord) ever be personally liable for
          any such liability.

10.5      ACTS OF GOD. In any case where either party hereto is required to do
          any act, delays caused by or resulting from Acts of God, war, civil
          commotion, fire, flood or other casualty, labor difficulties,
          shortages of labor, materials or equipment, government regulations,
          unusually severe weather, or other causes beyond such party's
          reasonable control shall not be counted in determining the time during
          which work shall be completed, whether such time be designated by a
          fixed date, a fixed time or a "reasonable time," and such time shall
          be deemed to be extended by the period of such delay.

10.6      LANDLORD'S DEFAULT. Landlord shall not be deemed to be in default in
          the performance of any of its obligations hereunder unless it shall
          fail to perform such obligations and such failure shall continue for a
          period of thirty (30) days or such additional time as is reasonably
          required to correct any such default after written notice has been
          given by Tenant to Landlord specifying the nature of Landlord's
          alleged default. Landlord shall not be liable in any event for
          incidental or consequential damages to Tenant by reason of Landlord's
          default, whether or not notice is given. Except as otherwise set forth
          herein, Tenant shall have no right to terminate this Lease for any
          default by Landlord hereunder and no right, for any such default, to
          offset or counterclaim against any rent due hereunder.

10.7      BROKERAGE. Landlord and Tenant warrant and represent to the other that
          it has dealt with no broker in connection with the consummation of
          this Lease, other than Nordblom Company and Grubb & Ellis, and in the
          event of any brokerage claims, other than by Nordblom Company or Grubb
          & Ellis, against either party predicated upon prior dealings with the
          other party, Landlord and Tenant, as applicable, each agree to defend
          the same and indemnify and hold the other party harmless against any
          such claim. Tenant shall not be responsible for the payment of the
          broker's fee due to Nordblom Company or Grubb & Ellis.

10.8      APPLICABLE LAW AND CONSTRUCTION. This Lease shall be governed by and
          construed in accordance with the laws of the Commonwealth of
          Massachusetts and, if any provisions of this Lease shall to any extent
          be invalid, the remainder of this Lease shall not be affected thereby.
          There are no oral or written agreements between Landlord and Tenant
          affecting this Lease. This Lease may be amended, and the provisions
          hereof may be waived or modified, only by instruments in writing
          executed by Landlord and Tenant. The titles of the several Articles
          and Sections contained herein are for convenience only and shall not
          be considered in construing this Lease. Unless repugnant to the
          context, the words "Landlord" and "Tenant" appearing in this Lease
          shall be construed to mean those named above and their respective
          heirs, executors, administrators, successors and assigns, and those
          claiming through or under them respectively. If there be more than one
          tenant, the obligations imposed by this Lease upon Tenant shall be
          joint and several.

          WITNESS the execution hereof under seal on the day and year first
          above written:

                                          Landlord

                                          by Middlesex Turnpike Corp, Manager
                                          ------------------------------------
                                          President

                                          [ILLEGIBLE]
                                          ------------------------------------
                                          V.P.

                                          Tenant:

                                          ACME PACKET, INC.

                                          By:  Keith Seidman
                                             -----------------------------------

                                          Its: Chief Financial Officer.
                                              ----------------------------------
                                              Hereunto Duly Authorized

                                       14
<Page>

                                    EXHIBIT A

                            PLAN SHOWING THE PREMISES

[GRAPHIC]

[GRAPHIC]

<Page>

                                    EXHIBIT B

                         COMMENCEMENT DATE NOTIFICATION

To:
   ----------------------
          (Tenant)

           ("Landlord") and          ("Tenant") are parties to a lease ("Lease")
dated          of premises in a building known as             , Massachusetts.
Landlord hereby notifies Tenant that the term of the Lease commenced on and
will end on          and that the first lease year commenced on         and
will end on    . Although not required for this notification to be effective,
we would appreciate your confirming the foregoing by signing the enclosed
copy of this letter and returning it to us.

                                              --------------------
                                                   (Landlord)

                                              By:
                                                 -----------------

Confirmed:

   ----------------------
          (Tenant)

By:
   ----------------------


604048_4

<Page>

                                    EXHIBIT C

                             PLAN AND SPECIFICATIONS

                                FIRST FLOOR PLAN

[GRAPHIC]

<Page>

                                    EXHIBIT C

                             PLAN AND SPECIFICATIONS

                                SECOND FLOOR PLAN

[GRAPHIC]

<Page>

                                    EXHIBIT C
                            PLANS AND SPECIFICATIONS

With reference to Maugel Architect, Inc.'s Schematic Design #4 dated 7.15.04
incorporated herein with this Exhibit C (Exhibit C Plans), the Landlord's Work
will be performed according to the following specifications:

DRYWALL:            Tenant partitions to be 3 5/8" metal studs with one layer of
                    1/2" gypsum board on each side, and will be constructed in
                    accordance with the Exhibit C Plans. Except as is otherwise
                    indicated on the Exhibit C Plans, partitions will extend
                    from floor to underside of suspended ceiling. Those
                    partitions highlighted in yellow on Exhibit C Plans will be
                    constructed from floor to approximately 6" above the
                    suspended ceiling.

DOORS & FRAMES:     Interior doors to be 3'-0" x 7'-0" solid-core with
                    maple veneer in hollow metal welded 30" sidelight frames
                    with SchlageTM or equal standard cylindrical lever hardware.
                    Hardware to include 1/2" pair of butts, one standard duty
                    brushed-aluminum lever passage set and one door stop.

MILLWORK:           Maple veneer sills at all exterior windows. Kitchen (lst
                    Floor) millwork and Coffee Station (2nd Floor) to each
                    include up to ten (10) linear feet of upper and lower
                    kitchen cabinets with P-LAM countertops. Millwork to be
                    ADA-compliant, and be comprised of standard-sized, white,
                    off-white, or gray laminate cabinets, with custom plastic
                    laminate tops (color by Architect). Reception desk and
                    furniture by Tenant. No other millwork included.

APPLIANCES:         A dishwasher and a sink-mounted garbage disposal unit will
                    be installed in the first-floor kitchen.

CEILINGS:           New 2'x4' suspended Second Look or equivalent revealed-edge
                    ceiling tiles to be installed throughout Premises with the
                    following exceptions: the Main Conference Room on the first
                    floor and the Board Room on the second floor will each have
                    a 2'x2' "fine-line" suspended ceiling.

ELECTRIC:           LIGHTS: Standard will be 2' x 4' fluorescent light fixtures
                    with electronic ballasts (T8) and 18 cell parabolic lenses.
                    Typical density is one fixture per 80 square feet of usable
                    area. One of every 20 - 25 of these fixtures will be
                    provided with emergency battery backup, in accordance with
                    fire code requirements and final tenant partition layout. In
                    Board Room (2nd Floor) and Main Conference Room (1" Floor)
                    up to eight (8) each dimmable down lights ("cans") shall
                    also be provided on a separate wall switch.

                    WORKSTATIONS: Workstation wiring circuitry to be provided in
                    the ratio of one (1) 20 amp circuit for every three (3)
                    workstations. Tenant's partition furniture to be pre-wired
                    including whips. Landlord's electrician will make final
                    connection. Workstations to be fed from walls or columns, or
                    by power poles if provided by Tenant.

                    SWITCHES: One single-pole wall-mounted light switch pkr
                    +/-4,000 square feet of open area and one per private
                    office, conference room, or otherwise demised area.

                    OUTLETS: One (1) duplex wall utility receptacle per 500+/-
                    square feet of open area and two per private office (larger
                    offices may have three duplex wall utility receptacles).
                    Lights, outlets, and VAV boxes within Premises to be wired
                    to Tenant electric meter. No power poles we included. Floor-

<Page>

                    mounted electric/tel/data devices, one (1) each, will be
                    installed in Board Room (2nd Floor) and Main Conference Room
                    (lst Floor). At Tenant's election and cost, additional
                    floor-mounted electric/tel/data devices may be installed.
                    Electric panels and transformers requisite for Tenant
                    distribution to be located within Premises.

                    EXIT SIGNS
                    Per code.

                    FIRE ALARM
                    Per code.

                    TEL/DATA
                    Landlord to provide "rings & strings" from above-finished
                    ceiling to in-wall junction boxes at locations denoted by
                    Architect. All other telldata wiring and installation work
                    by Tenant.

HVAC:               New, TRANE gas-fired Variable-Air-Volume (VAV) HVAC rooftop
                    units (RTU's) on galvanized structural steel grillage. RTU's
                    employ electric cooling, and gas-fired early morning warm-up
                    cycles. HVAC distribution to meet Class-A suburban office
                    standards, and be engineered by Landlord's mechanical
                    subcontractor. No other HVAC systems are included. Per
                    Tenant's request, TestingICustomer Service Lab to be zoned
                    with dedicated VAV boxes.

FLOORING:           A carpet allowance of $20 per square yard installed will be
                    provided for office areas. Resilient flooring (VCT) to be
                    installed in the Kitchen. At Tenant's election VCT may be
                    substituted in other appropriate areas; i.e:, Communication
                    Room, Storage Room, etc. 24"x 24" Lan carpet tile Cortez
                    (Black Forest) or equivalent, anti-static carpet will be
                    installed in the Manufacturinglstorage area and the
                    Testing/Customer Service Lab. Vinyl wall base shall be
                    installed throughout in a color specified by Architect and
                    approved by Tenant and Landlord.

WALL FINISHES:      All wall surfaces shall receive two coats of latex
                    paint with an eggshell finish using not more than four (4)
                    readily available colors. Hardwood doors and windowsills
                    shall receive two coats of clear polyurethane. All door
                    frames shall receive two coats of semi-gloss enamel. All
                    colors will be specified by Architect and approved by Tenant
                    and Landlord. No wall coverings will be provided.

SPRINKLER:          Entire building to have wet pipe system for Ordinary Hazard
                    Group 11.

WINDOWS:            All exterior windows will have 3" perforated PVC vertical
                    blinds in type and color selected by architect. No interior
                    blinds provided.

NOTE:               TELEPHONE WIRING, DATA WIRING, SECURITY SYSTEM, AND
                    DEDICATED HVAC SYSTEMS, ARE NOT INCLUDED IN THE PROPOSED
                    WORK.

<Page>

                                    EXHIBIT D

                                WORK CHANGE ORDER

Lease Date: __________________________    Date: ________________________________

Landlord: ____________________________    Work Change Order No.: _______________

Tenant: ______________________________    Building Address: ____________________

                                          Premises: ____________________________

________________________________________________________________________________
Tenant directs Landlord to make the following additions to Landlord's work:


Description of additional work:


Work Change Order Amount:
________________________________________________________________________________

Amount of Previous Work Change Orders:
This Work Change Order:
Total Amount of Work Change Orders :

Landlord approves this Work Change Order and Tenant agrees to pay to Landlord
the Total Amount of Work Change Orders at the earlier of ten days following
receipt of the Certificate of Occupancy of the premises or occupancy of the
premises by Tenant.


Tenant:                                 Landlord:

By: _____________________________       By: ____________________________

Title: __________________________       Title: _________________________

<Page>

                                    EXHIBIT E

                            FORM OF LETTER OF CREDIT


BENEFICIARY:                             ISSUANCE DATE:_______________, ____

____________________                     IRREVOCABLE STANDBY
                                         LETTER OF CREDIT NO.________

ACCOUNTEE/APPLICANT:                     MAXIMUM/AGGREGATE
                                         CREDIT AMOUNT:
___________________                      USD $_________
___________________
___________________


GENTLEMEN:


We hereby establish our irrevocable letter of credit in your favor for account
of the applicant up to an aggregate amount not to exceed _______________________
US Dollars ($____________) available by your draft(s) drawn on ourselves at
sight accompanied by:

Your statement, signed by a purportedly authorized officer/official certifying
that the Beneficiary is entitled to draw upon this Letter of Credit (in the
amount of the draft submitted herewith) pursuant to Section 4.4 of the lease
(the "Lease") dated _______ __, _____ by and between ______________,as Landlord,
and _______________, as Tenant, relating to the premises at___________________.

Draft(s) must indicate name and issuing bank and credit number and must be
presented at this office.

You shall have the right to make partial draws against this Letter of Credit,
from time to time.

Except as otherwise expressly stated herein, this Letter of Credit is subject to
the "Uniform Customs and Practice for Documentary Credits, International Chamber
of Commerce, Publication No. 500 (1993 Revision)."

This Letter of Credit shall expire at our office on _______________, _____ (the
"Stated Expiration Date"). It is a condition of this Letter of Credit that the
Stated Expiration Date shall be deemed automatically extended without amendment
for successive one (1) year periods from such Stated Expiration Date, unless at
least forty-five (45) days prior to such Stated Expiration Date) or any
anniversary thereof) we shall notify the Beneficiary and the Accountee/Applicant
in writing by registered mail (return receipt) that we elect not to consider
this Letter of Credit extended for any such additional one (1) year period.

We engage with you that all drafts drawn under and in compliance with the terms
of this letter of credit will be duly honored on presentation to US.

                                                 Very truly yours,


                                                 Authorized Signatory

<Page>

                                    EXHIBIT F

                              RULES AND REGULATIONS

1.   The sidewalks, entrances, passages, corridors, vestibules, halls,
     elevators, or stairways in or about the Building shall not be obstructed by
     Tenant.

2.   Tenant shall not place objects against glass partitions, doors or windows
     which would be unsightly from the Building corridor or from the exterior of
     the Building.

3.   Tenant shall not waste electricity or water in the Building premises and
     shall cooperate fully with Landlord to assure the most effective operation
     of the Building heating and air conditioning systems. All regulating and
     adjusting of heating and air-conditioning apparatus shall be done by the
     Landlord's agents or employees.

4.   Tenant shall not use the Premises so as to cause any increase above normal
     insurance premiums on the Building.

5.   No bicycles, vehicles, or animals of any kind shall be brought into or kept
     in or about the Premises. No space in the Building shall be used for the
     sale of merchandise of any kind at auction or for storage thereof
     preliminary to such sale.

6.   Tenant shall cooperate with Landlord in minimizing loss and risk thereof
     from fire and associated perils.

7.   The water and wash closets and other plumbing fixtures shall not be used
     for any purposes other than those for which they were designed and
     constructed and no sweepings, rubbish, rags, acid or like substance shall
     be deposited therein. All damages resulting from any misuse of the fixtures
     shall be borne by the Tenant.

8.   Landlord reserves the right to establish, modify, and enforce reasonable
     parking rules and regulations, provided such rules and obligations do not
     diminish Tenant's rights under the Lease.

9.   Landlord reserves the right at any time to rescind, alter or waive any rule
     or regulation at any time prescribed for the Building and to impose
     additional reasonable rules and regulations when in its judgment deems it
     necessary, desirable or proper for its best interest.

10.  Tenant acknowledges that the Building has been designated a non-smoking
     building. At no time shall Tenant permit its agents, employees,
     contractors, guests or invitees to smoke in the Building or, except in
     specified locations, directly outside the Building.

<Page>

                                    EXHIBIT G

                           TENANT ESTOPPEL CERTIFICATE


TO: ________________________("Mortgagee" or "Purchaser")

THIS IS TO CERTIFY THAT:

     1.   The undersigned is the tenant (the "Tenant") under that certain lease
(the "Lease") dated _________,20__, by and between ____________ as landlord (the
"Landlord"), and the undersigned, as Tenant, covering those certain premises
commonly known and designated as _______________ (the "Premises") in the
building located at _______________, ____________, Massachusetts.

     2.   The Lease is attached hereto as Exhibit A and (i) constitutes the
entire agreement between the undersigned and the Landlord with respect to the
Premises, (ii) is the only Lease between the undersigned and the Landlord
affecting the Premises and (iii) has not been modified, changed, altered or
amended in any respect, except (if none, so state):
          _____________________________________
          _____________________________________
          _____________________________________

     3.   The undersigned has accepted and now occupies the Premises as of the
date hereof, and all improvements, if any, required by the terms of the Lease to
be made by the Landlord have been completed and all construction allowances to
be paid by Landlord have been paid. In addition, the undersigned has made no
agreement with Landlord or any agent, representative or employee of Landlord
concerning free rent, partial rent, rebate of rental payments or any other type
of rental or other economic inducement or concession except (if none, so state):
          _____________________________________
          _____________________________________
          _____________________________________

     4.   1.   The term of the Lease began (or is scheduled to begin) on ______,
               20__ and will expire on _________,20__;

          2.   The fixed rent for the Premises has been paid to and including
               ___________, 20__;

          3.   The fixed rent being paid pursuant to the Lease is at the annual
               rate of $_____________; and

          4.   The escalations payable by Tenant under the Lease are currently
               $_________, based on a pro rata share of _________%, and have
               been reconciled through __________,20__.

     5.   (i) No party to the Lease is in default, (ii) the Lease is in full
force and effect, (iii) the rental payable under the Lease is accruing to the
extent therein provided thereunder, (iv) as of the date hereof the undersigned
has no charge, lien or claim of off-set (and no claim for any credit or
deduction) under the Lease or otherwise, against rents or other charges due or
to become due thereunder or on account of any prepayment of rent more than one
(1) month in advance of its due date, and (v) Tenant has no claim against
Landlord for any security, rental, cleaning or other deposits, except (if none,
so state):
          _____________________________________
          _____________________________________

     6.   Since the date of the Lease there are no actions, whether voluntary or
otherwise, pending against the undersigned under the bankruptcy, reorganization,
arrangement, moratorium or similar laws of the United States, any state thereof
of any other jurisdiction.

     7.   Tenant has not sublet, assigned or hypothecated or otherwise
transferred all or any portion of Tenant's leasehold interest.

     8.   Neither Tenant nor Landlord has commenced any action or given or
received any notice for the purpose of terminating the Lease, nor does Tenant
have any right to terminate the Lease, except (if none, so state):
          _____________________________________
          _____________________________________

     9.   Tenant has no option or preferential right to purchase all or any part
of the Premises (or the real property of which the Premises are a part) nor any
right or interest with respect to the Premises or the real property of which the
Premises are a part. Tenant has no right to renew or extend the term of the
Lease or expand the Premises except (if none, so state):
          _____________________________________
          _____________________________________

     10.  The undersigned acknowledges that the parties named herein are relying
upon this estoppel certificate and the accuracy of the information contained
herein in making a loan secured by the Landlord's interest in the Premises, or
in connection with the acquisition of the Property of which the Premises is a
part.

     EXECUTED UNDER SEAL AS OF ______________,20__.

                                                TENANT:

                                                ______________________________

                                                By: __________________________
                                                    Name:
                                                    Title:
                                                    Duly Authorized

<Page>

                                    EXHIBIT H

                              INITIAL TENANT'S WORK

<Page>

                                    EXHIBIT D

                                WORK CHANGE ORDER


<Table>
<S>                                                <C>
Lease Date:      AUGUST 9, 2004 _______            Date:   _________________ NOVEMBER 30,2004

Landlord:    SEVENTY ONE LIMITED LIABILITY COMPANY Work Change Order No.:  _____________ 1

Tenant:      ACME PACKET, INC.____________         Building Address: 52 THIRD AVE., BURLINGTON, MA

                                                   Premises:            43,061 SF_______
</Table>

Tenant directs Landlord to make the following additions to Landlord's work:


Description of additional work:

TENANT-REQUESTED ADDITIONAL WORK AS DETAILED ON ATTACHED SHEET FROM ERLAND
CONSTRUCTION.


Work Change Order Amount:

$225,671.43

________________________________________________________________________________

<Table>
<S>                                                                 <C>
Amount of Previous Work Change Orders:  ..........................  $          0
This Work Change Order:  .........................................  $ 225,671.43
Total Amount of Work Change Orders: ..............................  $ 225,671.43
</Table>

Landlord approves this Work Change Order and Tenant agrees to pay to Landlord
the Total Amount of Work Change Orders at the earlier of ten days following
receipt of the Certificate of Occupancy of the premises or occupancy of the
premises by Tenant.


Tenant:                                  Landlord:

By: /s/ [ILLEGIBLE]                      By: /s/ [ILLEGIBLE]
    --------------------------               -----------------------------
                                             [ILLEGIBLE]
Title: Chief Financial Officer           Title:
       -----------------------                  --------------------------
                                         VP Development, Agent for N.W. 37 Trust

<Page>

                           TENANT ESTOPPEL CERTIFICATE

To:  Middlesex Savings Bank
     6 Main Street
     Natick, MA 01760 ("Lender")

Acme Packet, Inc., a Delaware corporation having an address 130 New Boston
Street, Woburn, MA 01801, ("Tenant") hereby certifies as follows:

1.   That the undersigned is the Tenant under that certain Lease dated August
     9,2004 (the "Lease") executed by Seventy One LLC) ("Landlord") as Landlord
     and the undersigned as Tenant, covering the property known as Building 37
     and located at 71 Third Avenue, Burlington, Massachusetts (the "Property").

2.   A. That, pursuant to the Lease, Tenant has leased approximately 43,061
     square feet of space at the Property) and, as security for Tenant's
     performance of its obligations under the Lease, has delivered to Landlord
     an Irrevocable Standby Letter of Credit No. SVBSF002998 dated August
     19,2004 issued by Silicon Valley Bank in the amount of $300,000.00; that
     the tern of the Lease is scheduled to commence on the "Commencement Date"
     as said tern is defined in the Lease and a fixed monthly rental payment in
     the amount of $43,061.00 is due on the later of (i) July 1,2005 or (ii) the
     date on which "Landlord's Work" (as defined in the Lease) has been
     substantially completed under the Lease; that Tenant is required to pay as
     "Additional Rent" (as said term is defined in the Lease)all annual
     operating expenses, real estate taxes for the building of which the demised
     premises are a part and other charges, all as provided in the Lease, on an
     estimated basis, on the first day of each month commencing on the later of
     (i) and (ii) hereinabove, all as provided in the Lease.

     B.   That Tenant will not make any payment under the Lease more than one
          (1) month in advance of the due date thereunder.

3.   That the Lease is in full force and effect and there are no amendments,
     modifications or supplements thereto, whether oral or written.

4.   The Lease does not provide for an option to purchase the Property, or any
     part thereof.

5.   That true, correct and complete copies of the Lease and all amendments,
     modifications and supplements thereto are attached hereto as Exhibit A; and
     that the Lease, as so amended, modified and supplemented, is in full force
     and effect and represents the entire agreement between Tenant and Landlord
     with respect to the demised premises and the Property.

6.   That, to Tenant's knowledge, all conditions under the Lease to be performed
     by Landlord as of the date hereof, except for the work or improvements
     described in Exhibit C hereto, have been satisfied.

<Page>

7.   That, upon substantial completion of the Landlord's Work (as defined in the
     Lease), Tenant is prepared to take occupancy of the demised premised under
     the terms of the Lease.

8.   That, to Tenant's knowledge, Landlord is not in any respect in default in
     the performance of the terms and provisions of the Lease, and no event has
     occurred which with the giving of notice or the passage of time, or both,
     will constitute a default by the Landlord under the Lease, nor does the
     Tenant claim any such default.

9.   That, to Tenant's knowledge, Tenant is not in any respect in default under
     the Lease and no event has occurred which with the giving of notice or the
     passage of time, or both, will constitute a default by Tenant under the
     Lease, and Tenant has not assigned, transferred, encumbered or hypothecated
     the Lease or any interest therein or subleased all or any portion of the
     demised premises.

10.  That, to Tenant's knowledge, there are no offsets or credits against
     rentals payable under the Lease and no free rent periods or rental
     concessions have been granted to Tenant except the following: that Tenant
     does not commence paying rent for the Premises until the later of (i) July
     1,2005 or (ii) the date that Landlord's Work (as defined in the Lease) has
     been "substantially completed" (as defined in the Lease).

11.  That except as expressly provided in the Lease, and other documents
     attached hereto, Tenant does not have any right or option to renew or
     extend the term of my Lease, to lease other space at the Property, nor any
     preferential right to lease or purchase all or any part of the demised
     premises or the Property.

12.  That Tenant has no right to terminate the Lease except as set forth in the
     Lease.

13.  That neither Tenant nor any guarantor of Tenant's obligations under the
     Lease is the subject of any bankruptcy, insolvency or creditors' rights
     proceedings.

14.  That, except as permitted under the Lease, Tenant has no actual or
     knowledge of the unlawful presence, use, storage, disposal, release or
     treatment of any hazardous or toxic materials or substances at, on or
     beneath the demised premises or Property.

                [THE BALANCE OF THIS PAGE IS INTENTIONALLY BLANK]

                                        2
<Page>

This Certificate is given to Lender with the understanding that Lender or its
designee will rely hereon in connection with the financing of the Property
including, without limitation, in connection without a $4,200,000.00 mortgage
loan from Lender to Landlord. Following any such financing, the Lease shall
remain in full force and effect.

     Executed under seal as of December 22, 2004.


WITNESS:                             TENANT

                                     ACME PACKET, INC., a Delaware corporation

/s/ Robin Pancygrau                     By:/s/ Keith Seidman
----------------------------            ------------------------------------
Name: Robin Pancygrau                   Name: Keith Seidman
                                        Title: Chief Financial Officer
                                        duly authorized

                                        3
<Page>

                                    EXHIBIT A

                [ATTACH LEASE AND AMENDMENTS TO THIS CERTIFICATE]

                                        4
<Page>

             NON-DISTURBANCE, ATTORNMENT AND SUBORDINATION AGREEMENT

     THIS AGREEMENT is made and entered into as of this          day of
December, 2004, by and among MIDDLESEX SAVINGS BANK (hereinafter called the
"Lender"), and ACME PACKET, INC., a Delaware corporation having an address at
130 New Boston Street, Woburn, MA 01801 (hereinafter called the "Tenant"), and
SEVENTY ONE LLC, a Massachusetts limited liability company having an address c/o
Nordblom Management Company, Inc., 15 Third Avenue, Burlington, MA 01803
(hereinafter called the "Landlord").

                               W I T N E S S E T H:

     WHEREAS, Landlord owns certain real property located in Middlesex County,
Massachusetts, and more particularly described in EXHIBIT A attached hereto and
made a part hereof (said property being hereinafter called the "Property"); and

     WHEREAS, Landlord and Tenant made and entered into that certain Lease,
dated the 9th day of August, 2004, with respect to the Property (said Lease
being hereinafter called the "Lease" and said premises being hereinafter called
the "Leased Premises"); and

     WHEREAS, on or about the date hereof, Landlord has entered into and
delivered that certain Mortgage and Security Agreement in favor of Lender to be
recorded in the Middlesex Registry of Deeds and filed in the Middlesex South
County Registry District of the Land Court prior to the recording of this
Agreement (said Mortgage and Security Agreement and all amendments, renewals,
increases, modifications, replacements, substitutions, extensions, spreaders,
restatements, and consolidations thereof and all re-advances and advances
thereunder and additions thereto being hereinafter called the "Security Deed"),
conveying the Property to secure the payment of the indebtedness described in
the Security Deed; and

     WHEREAS, on or about the date hereof, Landlord has entered into and
delivered that certain Collateral Assignment of Leases and Rents in favor of
Lender to be recorded in the Middlesex Registry of Deeds and filed in the
Middlesex South County Registry District of the Land Court prior to the
recording of this Agreement (said Assignment of Leases and Rents being
hereinafter called the "Assignment of Leases"), assigning all of Landlord's
right, title and interest as lessor under the Lease to further secure the
Secured Debt, as described and defined in the Security Deed; and

     WHEREAS, the parties hereto desire to enter into this Non-Disturbance,
Attornment and Subordination Agreement;

     NOW, THEREFORE, for and in consideration of the mutual covenants
hereinafter set forth and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, Lender, Tenant, and Landlord each
hereby covenants and agrees as follows:

1.   NON-DISTURBANCE. So long as no default exists, nor any event has occurred
     which has continued to exist for such period of time (after notice, if any,
     required by the Lease) as would entitle the lessor under the Lease to
     terminate the Lease or would cause, without any further action on the part
     of such lessor, the termination of the Lease or would entitle such lessor
     to dispossess the lessee thereunder, the Lease shall not be terminated, nor
     shall such lessee's use, possession or enjoyment of the Leased Premises or
     rights under the Lease be interfered with in any foreclosure or other
     action or proceeding in the nature

                                       -1-
<Page>

     of foreclosure instituted under or in connection with the Security Deed or
     in the event that Lender takes possession of the Property pursuant to any
     provisions of the Security Deed or the Assignment of Leases, unless the
     lessor under the Lease would have had such right if the Security Deed or
     the Assignment of Leases had not been made, except that neither the person
     or entity acquiring the interest of the lessor under the Lease as a result
     of any such action or proceeding or deed in lieu of any such action or
     proceeding (hereinafter called the "Purchaser") nor Lender if Lender takes
     possession of the Property shall be (a) liable for any act or omission of
     any prior lessor under the Lease other than defaults of a continuing nature
     that (i) exist as of the date Purchaser or Lender takes possession or
     becomes owner of the Property for which notice to Lender has been duly
     given by either Landlord or Tenant and (ii) constitute a breach of
     Landlord's obligations under Sections 2.1, Article 5 and Article 10, for
     which Lender's or Purchaser's liability shall be limited to the period of
     time after Lender or Purchaser acquire the interest of Landlord under the
     Lease or Lender takes possession of the Property, and shall be limited _ as
     is otherwise provided herein; or (b) liable for the return of any security
     deposit or letter of credit which lessee under the Lease has paid or
     delivered to any prior lessor under the Lease unless such is held by Lender
     and, in addition, in the case of a letter of credit, has been issued in
     Lender's name; or (c) subject to any offsets or defenses which the lessee
     under the Lease might have against any prior lessor under the Lease; or (d)
     bound by any base rent, percentage rent or any other payments which the
     lessee under the Lease might have paid for more than the current month to
     Landlord or any prior lessor under the Lease; or (e) bound by any amendment
     or modification of any material term of the Lease made without Lender's
     prior written consent; or (f) personally liable for any default under the
     Lease or any covenant or obligation on its part to be performed thereunder
     as lessor, it being acknowledged and agreed that (i) Tenant's sole remedy
     in the event of such default shall be to proceed against Purchaser's or
     Lender's interest in the Property and (ii) Lender's liability under the
     Lease shall be limited to Lender's interest in the Property and in no event
     shall Lender be liable for indirect or consequential damages.
     Notwithstanding anything contained herein to be contrary, Lender shall have
     absolutely no obligation to perform any of Landlord's construction
     covenants under the Lease, provided that if Lender shall not perform such
     covenants in the event of foreclosure or deed in lieu thereof and within a
     reasonable time following taking of possession by Lender, then Tenant shall
     have the right to terminate its obligations under the Lease and to pursue
     any and all legal remedies it may have against Landlord and any third
     parties other than Lender.

2.   ATTORNMENT. Unless the Lease is terminated in accordance with Paragraph 1,
     if the interests of the lessor under the Lease shall be transferred by
     reason of the exercise of the power of sale contained in the Security Deed
     (if applicable), or by any foreclosure or other proceeding for enforcement
     of the Security Deed, or by deed in lieu of foreclosure or such other
     proceeding, or if Lender takes possession of the Property pursuant to any
     provisions of the Security Deed or the Assignment of Leases, the lessee
     thereunder shall be bound to the Purchaser or Lender, as the case may be,
     under all of the terms, covenants and conditions of the Lease for the
     balance of the term thereof and any extensions or renewals thereof which
     may be effected in accordance with any option therefor in the Lease, with
     the same force and effect as if the Purchaser or Lender were

                                       -2-
<Page>

     the lessor under the Lease, and Tenant, as lessee under the Lease, does
     hereby attorn to the Purchaser and Lender if it takes possession of the
     Property, as its lessor under the Lease. Purchaser, and Lender if it takes
     possession of the Property, hereby further agree that it will accept such
     attornment and, subject to the provisions of this Agreement including,
     without limitation, the provisions of paragraph 1 hereinabove, as of the
     date of such purchase or possession and for any obligations of Landlord
     that arise under the Lease from and after such date, it will assume and
     perform (but only while the owner or in possession of the Property) all of
     Landlord's obligations under the Lease and be bound to Tenant under the
     provisions of the Lease for the balance of the term thereof and any
     extensions or renewals thereof which may be effected in accordance with any
     option therefor in the Lease, with the same force and effect as if the
     Purchaser or Lender were the Landlord under the Lease, except as otherwise
     provided in this Agreement. Such attornment shall be effective and
     self-operative without the execution of any further instruments upon the
     succession by Purchaser to the interest of the lessor under the Lease or
     the taking of possession of the Property by Lender. Nevertheless, Tenant
     shall, from time to time, execute and deliver such instruments evidencing
     such attornment as Purchaser or Lender may require in forms reasonably
     acceptable to Lender and Tenant. The respective rights and obligations of
     Purchaser, Lender and of the lessee under the Lease upon such attornment,
     to the extent of the then remaining balance of the term of the Lease and
     any such extensions and renewals, shall be and are the same as now set
     forth in the Lease except as otherwise expressly provided in Paragraph 1.

3.   SUBORDINATION. Tenant hereby subordinates all of its right, title and
     interest as lessee under the Lease as the same may be modified, amended or
     extended, to the right, title and interest of Lender under the Security
     Deed and to each and every advance heretofore made or hereafter made under
     the Security Deed, and Tenant further agrees that the Lease now is and
     shall at all times continue to be subject and subordinate in each and every
     respect to the Security Deed and to any and all increases, renewals,
     modifications, extensions, substitutions, replacements and/or
     consolidations of the Security Deed.

4.   ASSIGNMENT OF LEASES. Tenant hereby acknowledges that all of Landlord's
     right, title and interest as lessor under the Lease is being duly assigned
     to Lender pursuant to the terms of the Security Deed and the Assignment of
     Leases, and that pursuant to the terms thereof all rental payments under
     the Lease shall continue to be paid to Landlord in accordance with the
     terms of the Lease unless and until Tenant is otherwise notified in writing
     by Lender. Upon receipt of any such written notice from Lender, Tenant
     covenants and agrees to make payment of all rental payments then due or to
     become due under the Lease, including, without limitation, any and all
     payments provided in Section 8.2 of the Lease, directly to Lender or to
     Lender's agent designated in such notice and to continue to do so until
     otherwise notified in writing by Lender. Landlord hereby irrevocably
     directs and authorizes Tenant to make rental payments directly to Lender
     following receipt of such notice, and Landlord covenants and agrees that
     Tenant shall have the right to rely on such notice without any obligation
     to inquire as to whether any default exists under the Security Deed or the
     Assignment of Leases or the indebtedness secured thereby, and
     notwithstanding any notice or claim of Landlord to the contrary, and that
     Landlord shall have no right or claim against Tenant for or by reason of
     any rental payments made by Tenant to Lender following receipt of such
     notice. Lender and

                                       -3-
<Page>

     Landlord further agree that Tenant shall be credited under the Lease for
     any rental payment received by Lender pursuant to such written notice.

5.   NOTICE OF DEFAULT BY LANDLORD. Tenant, as lessee under the Lease, hereby
     covenants and agrees to give Lender written notice properly specifying
     wherein the lessor under the Lease has failed to perform any of the
     covenants or obligations of the lessor under the Lease, simultaneously with
     the giving of any notice of such default to the lessor under the provisions
     of the Lease. Tenant agrees that Lender shall have the right, but not the
     obligation, within ten (10) days after the expiration of any cure period
     provided to Landlord under the Lease for such cure (or for such additional
     time as is reasonably required to cure such default provided that Lender
     has given notice to Tenant of Lender's intent to cure such default and
     Lender is diligently proceeding to cure such default) to correct or remedy,
     or cause to be corrected or remedied, each such default before the lessee
     under the Lease may take any action under the Lease by reason of such
     default. In addition, Landlord shall provide to Lender, simultaneously with
     its delivery of said document to the Tenant, a copy of any "Commitment Date
     Notification" provided by Landlord under the Lease and a copy of any such
     notification signed by Tenant Such notices to Lender shall be delivered in
     duplicate to:

               Middlesex Savings Bank
               6 Main Street
               Natick, Massachusetts 01760
               Attn: Mr. Patrick M. Lee

     or to such other address as the Lender shall have designated to Tenant by
     giving written notice to Tenant, prior to possession by Tenant under the
     Lease at 130 New Boston Street, Woburn, MA 01801, and, after possession by
     Tenant under the Lease at 71 Third Avenue, Burlington, MA 01801 Attention:
     CFO, or to such other address as may be designated by written notice from
     Tenant to Lender.

6.   NO FURTHER SUBORDINATION. Except as expressly provided to the contrary in
     Paragraph 4 hereof, Landlord and Tenant covenant and agree with Lender that
     there shall be no further subordination of the interest of lessee under the
     Lease to any lender or to any other party without first obtaining the prior
     written consent of Lender. Any attempt to effect a further subordination of
     lessee's interest under the Lease without first obtaining the prior written
     consent of Lender shall be null and void.

7.   TITLE OF PARAGRAPHS. The titles of the paragraphs of this agreement are for
     convenience and reference only, and the words contained therein shall in no
     way be held to explain, modify, amplify or aid in the interpretation,
     construction or meaning of the provisions of this agreement.

8.   GOVERNING LAW. This agreement shall be governed by and construed in
     accordance with the laws of The Commonwealth of Massachusetts.

9.   PROVISIONS BINDING. The terms and provisions hereof shall be binding upon
     and shall inure to the benefit of the heirs, executors, administrators,
     successors and permitted assigns, respectively, of Lender, Tenant and
     Landlord. The reference contained to

                                       -4-
<Page>

     successors and assigns of Tenant is not intended to constitute and does not
     constitute a consent by Landlord or Lender to an assignment by Tenant, but
     has reference only to those instances in which the lessor under the Lease
     and Lender shall have given written consent to a particular assignment by
     Tenant thereunder.

10.  CASUALTY INSURANCE PROCEEDS AND CONDEMNATION AWARDS. Notwithstanding
     anything to the contrary contained in this Agreement or in the Lease, the
     Tenant agrees that (i) the provisions of the Security Deed shall govern
     with regard to casualty insurance proceeds and condemnation awards, and
     (ii) in the event the casualty insurance proceeds or condemnation awards
     are not made available for restoration of the Premises, such proceeds or
     awards shall be paid to the Lender.

11.  JURY TRIAL. Both the Tenant and the Lender hereby irrevocably waive all
     right to trial by jury in any action, proceeding or counterclaim arising
     out of or relating to the Lease or this Agreement.

                                       -5-
<Page>

     IN WITNESS WHEREOF, the parties have hereunto set their respective hands
and seals as of the day, month and year first above written.

                                     LENDER:

                                     MIDDLESEX SAVINGS BANK


                                     By:
                                        -------------------------
                                          Title:


                                     TENANT:

                                     ACME PACKET, INC., a Delaware
                                     corporation


                                     By:   /s/ Keith Seidman
                                           ------------------------------
                                           Title: Chief Financial Officer

                                       -6-
<Page>

                           LANDLORD:

                           SEVENTY ONE LLC, a Massachusetts limited
                           liability company

                           By: MTP Limited Partnership, a Massachusetts limited
                               partnership, its Manager

                               By: Middlesex Turnpike Corp., a Massachusetts
                                   corporation, its General Partner

                                   By:
                                        -----------------------
                                        Name:  Peter C. Nordblom
                                        Title: Its President


                                   By:
                                        -----------------------
                                        Name:  John D. Macomber
                                        Title: Its Duly Authorized Person

                           By: Middlesex Turnpike Corp., a Massachusetts
                               corporation, its Manager

                               By:
                                     --------------------------
                               Name: Peter C. Nordblom
                               Title: Its President

                                       -7-
<Page>

COMMONWEALTH OF MASSACHUSETTS

COUNTY OF

          On this ______ day of December, 2004, before me, the undersigned
notary public, personally appeared ________________, as _____________ of
Middlesex Savings Bank, proved to me through satisfactory evidence of
identification, which were ______________, to be the person whose name is signed
on the preceding or attached document and acknowledged to me that he signed it
voluntarily for its stated purpose.

                         ---------------------------------

                             (official signature and seal

                             and stamp of notary public)

                         My Commission Expires: __________


COMMONWEALTH OF MASSACHUSETTS

COUNTY OF

          On this 22nd day of December, 2004, before me, the undersigned notary
public, personally appeared [ILLEGIBLE], as C.F.O of Acme Packet, Inc., proved
to me through satisfactory evidence of identification, which were [ILLEGIBLE] be
the person whose name is signed on the preceding or attached document and
acknowledged to me that he signed it voluntarily for its stated purpose.

                            /s/ Gina A. Lazaris
                            ---------------------------------
                                (official signature and seal

                                and stamp of notary public)

                            My Commission Expires:        GINA A. LAZARIS
                                                           Notary Public
                                                   Commonwealth of Massachusetts
                                               [SEAL]    My Commission Expires
                                                           October 2, 2009

                                       -8-
<Page>

COMMONWEALTH OF MASSACHUSETTS

COUNTY OF

          On this ______ day of December, 2004, before me, the undersigned
notary public, personally appeared ______________, as the President of Middlesex
Turnpike Corp., (i) the general partner of MTP Limited Partnership, the manager
of Seventy One LLC and (ii) the manager of Seventy One LLC, proved to me through
satisfactory evidence of identification, which were _______________,to be the
person whose name is signed on the preceding or attached document and
acknowledged to me that he signed it voluntarily for its stated purpose.


                                    ---------------------------------------

                                             (official signature and seal
                                             and stamp of notary public)

                                    My Commission Expires: ________________


COMMONWEALTH OF MASSACHUSETTS

COUNTY OF

          On this _____ day of December, 2004, before me, the undersigned notary
public, personally appeared _______________, as duly authorized person of
Middlesex Turnpike Corp., the general partner of MTP Limited Partnership, the
manager of Seventy One LLC, proved to me through satisfactory evidence of
identification, which were _________________, to be the person whose name is
signed on the preceding or attached document and acknowledged to me that he
signed it voluntarily for its stated purpose.



                                    ---------------------------------------

                                             (official signature and seal
                                             and stamp of notary public)

                                    My Commission Expires: ________________

                                       -9-
<Page>

                                   EXHIBIT "A"

Two certain parcels of land with the buildings thereon in Burlington, Middlesex
County, Massachusetts, bounded and described as follows:

Parcel 1:   (Registered Land)

Said parcel comprises Lot 88 on a plan drawn by Charles A. Perkins Co., Inc.,
Surveyor dated April 1973, as approved by the Land Court, filed in the Land
Registration Office as No. 6728-9, a copy of a portion of which is filed in
Middlesex South Registry of Deeds District of the Land Court with Certificate
Number 12333 1, Book 746, Page 18 1.

Parcel 11:  (Recorded Land)

A certain parcel of land, situated in said Burlington, shown as Lot K-4 on a
plan entitled "Land in Burlington, Mass. Surveyed for Middlesex Turnpike
Industrial Trust" prepared by Charles A. Perkins Co. Inc., Engineers and
Surveyors, dated March 1973, the original linen tracing of which is recorded
with Middlesex South Registry of Deeds at the end of Book 12454, to which plan
reference is made for a more particular description, and containing 2 acres and
28,791 square feet, according to said plan.

Together with the benefits of that certain Access Easement Agreement dated
December 5,2000 by and between Rodger P. Nordblom, Peter C. Nordblom, George
Macomber and John D. Macomber as Trustees of Middlesex Turnpike Industrial Trust
("Fee Owners") and Rodger P. Nordblom, Peter C. Nordblom and George Macomber as
Trustees of N.W. Building 38 Associates ("Ground Lessees") and Seventy One LLC
("Grantees") recorded in Middlesex South District Registry of Deeds in Book 32
168, Page 584.

                                      -10-