Document:

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                                 EXHIBIT 10.18

                                GLOBAL AGREEMENT

     This Global Agreement (this "AGREEMENT") is being entered into effective as
of March 5, 2002 (the "EFFECTIVE DATE"), by and among TR Lookout Partners,
Ltd. ("TRLP"), Collins Campbell Joint Venture ("CCJV"), telecom technologies,
inc. ("TTI"), and Sonus Networks, Inc. ("SONUS"). TRLP, CCJV, TTI, and Sonus
shall be collectively referred to as the "PARTIES".

                                    RECITALS:

     WHEREAS, TTI has entered into several leases (the "LEASES") with TRLP and
CCJV, as landlords, and pursuant to the terms of the Leases, TTI is bound and
obligated to perform all of its obligations under the Leases for the remaining
terms of each of the Leases;

     WHEREAS, TTI is a wholly owned subsidiary of Sonus and due to economic
conditions, requires a reduction in its Richardson, Texas facilities under lease
with TRLP and CCJV (collectively, the "LANDLORDS");

     WHEREAS, the Landlords have agreed to certain lease terminations and/or
modifications in exchange for the agreements set forth herein, the payments by
Sonus to TRLP representing a reimbursement to CCJV of the cost of various tenant
improvements, lease termination, capital expenses, and build out costs in
connection with the premises covered by the lease terminated hereunder, all as
more fully described below, and such other good and valuable consideration; and

     NOW, THEREFORE, in consideration of the covenants and agreements
hereinafter set forth and for other good and valuable consideration, the receipt
and adequacy of which are hereby acknowledged, the Parties have agreed to the
above recitals and as follows:

     1.  Notwithstanding anything to the contrary in this Agreement (or any of
         the agreements including lease agreements referenced herein; hereafter
         such agreements, together with this Agreement, shall be collectively
         referred to as the "DOCUMENTS"), the Documents (inclusive of this
         Agreement) shall NOT be effective until the occurrence of each and
         every one of the following events: (A) the execution and delivery by
         the Parties to each other of (i) this Agreement; (ii) the Termination
         of Office Lease Agreement attached as EXHIBIT "A" hereto; (iii) the
         Termination of Office Lease Agreement, attached as EXHIBIT "B" hereto;
         (iv) the Fifth Amendment to Office Lease Agreement, attached as EXHIBIT
         "C" hereto; (v) the Guarantee, attached as EXHIBIT "D" hereto; (vi) the
         Bill of Sale, attached as EXHIBIT "E" hereto; (vii) the Storage
         Agreement with respect to the Personal Property, attached as EXHIBIT
         "F" hereto; (viii) the Guarantee of Sonus with respect to the
         obligations of TTI under the Bill of Sale and Storage Agreement,
         attached as EXHIBIT "G" hereto; (B) the indefeasible and irrevocable
         payment by Sonus of One Million Dollars ($1,000,000) to TRLP, in care
         of Thompson Realty Investment Corporation ("THOMPSON REALTY"),
         contemporaneous with the payment by TRLP to TTI of such payment
         described in subsection (D) immediately below; (C) the indefeasible and
         irrevocable payment by Sonus to Thompson Realty of $2,500.00,
         representing no less than fifty percent (50%) of all legal fees, costs
         and expenses incurred by counsel for Thompson Realty in connection with
         these matters; and (D) the wire transfer by TRLP at Closing to TTI of
         One Hundred Sixty Five Thousand Two Hundred Thirty-Six and 50/100
         Dollars ($165,236.50) as provided under EXHIBIT "A" to this Agreement,
         contemporaneous with the payment by Sonus to TRLP described in
         subsection (B) immediately above. At Closing, TRLP and CCJV shall
         deliver to Sonus and TTI consents from their respective lenders
         approving the termination, and amendments where applicable, of their
         respective Leases with TTI, as provided herein, which consents shall be
         in the form of EXHIBITS "H" and "I" hereto.

                                     Page 1
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     2.  On the Effective Date, that certain Office Lease Agreement, dated
         November 14, 2000, as amended by that certain First Amendment to Office
         Lease Agreement, dated as of January, 8, 2001, by and between TRLP and
         TTI, will be terminated and shall be of no further force and effect, in
         accordance with the terms set forth in the Termination of Office Lease
         Agreement, attached hereto as EXHIBIT "A" and incorporated herein for
         all purposes.

     3.  On the Effective Date, those certain Office Lease Agreements described
         below, by and between CCJV and TTI, will be modified and/or terminated
         in accordance with the agreements attached hereto as EXHIBIT "B", and
         EXHIBIT "C", each of which is incorporated herein for all purposes.
         These agreements generally provide for the following:

         a. Suite 1050, Richardson, Texas 75080, approximately 6,618 square feet
            - terminated;
         b. Suite 3000, Richardson, Texas 75080, approximately 38,016 square
            feet - modified to reduce the size of the premises ("LEASE 1");
         c. Suite 339, Richardson, Texas 75080, approximately 2,281 square feet
            - no change in terms ("LEASE 2"); and
         d. Suite 2400, Richardson, Texas 75080, approximately 2,055 square feet
            - no change in terms ("LEASE 3").

     4.  TTI hereby acknowledges and consents to all of the terms and conditions
         of Lease 1, Lease 2, and Lease 3 (collectively, the "OFFICE LEASES"),
         and TTI and Sonus each ratifies, reaffirms, and confirms the
         effectiveness of each of the Office Leases. TTI and Sonus each
         acknowledges that each such party has no claims, counterclaims,
         offsets, credits or defenses to the Leases, and each party's
         performance of its obligations thereunder (to the extent applicable),
         or if TTI or Sonus has any such claims, counterclaims, offsets, credits
         or defenses to the Leases or any transaction related to the Leases, the
         same are hereby waived, relinquished and released in consideration of
         the Parties' mutual agreements set forth in this Agreement.

     5.  On the Effective Date, Sonus will guarantee unconditionally all of the
         obligations and covenants of TTI to CCJV under the three (3) remaining
         leases at the "Atrium on Collins", in accordance with the terms of the
         Guarantee attached hereto as EXHIBIT "D" and incorporated herein for
         all purposes.

     6.  CCJV hereby agrees to exercise good faith efforts to reach a written
         agreement with Hamid Ansari and Anousheh Ansari (collectively, the
         "ANSARIS") providing for a release from the Ansaris in favor of CCJV,
         TTI, and Sonus, with respect to any obligations of such parties, if any
         (with respect to the payment of a profit fee), as provided in that
         certain letter agreement, dated April 4, 1997, executed by CCJV and the
         Ansaris, as amended by that certain letter agreement, dated November 1,
         2000, executed by CCJV and the Ansaris, each of which letter agreements
         was consented to by TTI; PROVIDED, HOWEVER, that if CCJV is unable to
         provide such release to Sonus and TTI, on or prior to the Effective
         Date, then CCJV shall indemnify Sonus and TTI in accordance with the
         terms of the agreement in the form attached hereto as EXHIBIT "J".

     7.  On the Effective Date, TTI agrees that (i) TTI shall transfer to CCJV
         on the earlier of (the "TRANSFER DATE") (A) the date that TTI vacates
         the premises at Suite 3000, 1701 North Collins Boulevard, Richardson,
         Texas 75080, or (B) April 30, 2003 (or such later date, as may be
         extended pursuant to an amendment to the lease, with respect to such
         premises, entered into by TTI and CCJV, thereby extending the term of
         such lease), all of TTI's right, title, and interest in and to certain
         furniture, fixtures, and equipment owned by TTI, substantially in
         accordance with the terms of the bill of sale attached hereto as
         EXHIBIT "E" incorporated herein for all purposes (the "BILL OF SALE"),
         and (ii) TTI shall enter into with CCJV a storage agreement, thereby
         agreeing to store such furniture, fixtures, and equipment, at Suites
         1050 and 2000, at 1701 North Collins Boulevard, Richardson, Texas
         75080, for the period from and after the Effective Date and continuing
         through the earlier of (the "REMOVAL DATE")

                                     Page 2
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         (A) April 30, 2003, or (B) twenty (20) calendar days after written
         notice from CCJV to TTI to remove such furniture, fixtures and
         equipment, and TTI and CCJV shall execute and deliver a storage
         agreement in the form attached hereto as EXHIBIT "F" and incorporated
         herein for all purposes (the "STORAGE AGREEMENT"). Such Bill of Sale
         and Storage Agreement shall be without recourse or liability to CCJV
         (or its assigns), and shall not constitute, nor be deemed to be, any
         assumption by CCJV (or its assigns) of any obligations, liabilities, or
         indebtedness of TTI (i) on or under such personal property leases or
         (ii) arising out of or in connection with the personal property to be
         transferred under the Bill of Sale. On the Effective Date, Sonus shall
         execute and deliver to CCJV a Guarantee in the form attached hereto as
         EXHIBIT "G", thereby guaranteeing all of TTI's obligations to CCJV (or
         its assigns) with respect to the Bill of Sale, the Storage Agreement,
         and TTI's obligations to CCJV (or its assigns) in this paragraph 7.

     8.  On the Effective Date, Sonus shall pay to Thompson Realty the sum of
         $2,500 representing no less than fifty percent (50%) of the legal fees
         incurred by counsel for Thompson Realty in connection with this these
         transactions and matters.

     9.  Each Party hereto hereby makes the following representations and
         warranties to each other Party, each of which is material, is being
         relied upon by each of the Parties hereto, and is true as of the date
         hereof: (i) this Agreement (and the Documents) has been duly and
         validly executed and delivered by such party; (ii) no further action of
         any kind or nature will be or is necessary on the part of such party,
         or any other person whomsoever, to make this Agreement (and the
         Documents) valid, binding and enforceable upon such party in accordance
         with the terms hereof; (iii) this Agreement (and the Documents) has
         been consented to by TRLP's and CCJV's lender and is thereby authorized
         by such lenders; and (iv) this Agreement (and the Documents)
         constitutes a legal, valid and binding obligation of such Party,
         enforceable in accordance with the terms hereof or as otherwise
         provided by law.

     10. It is the mutual intent of all of the Parties hereto that the Documents
         are, and shall be, final, conclusive, binding, enforceable and
         non-terminable as of, and from and after, the Effective Date, subject
         to the conditions precedent to paragraph 1 of this Agreement.

     11. Each of the Parties hereto hereby covenants and agrees to do such acts
         and things and, in connection therewith, to execute and deliver such
         documents and instruments as reasonably may be required for effecting
         and otherwise carrying out the purposes of the transactions covered and
         contemplated hereby.

     12. No Party hereto may assign any of its rights or delegate any of its
         duties hereunder without the prior written notice of the other Parties
         hereto, and any such assignment or delegation without the prior written
         notice shall be void ab initio.

     13. All terms and provisions of the Documents shall be binding upon and
         inure to the benefit of the respective Parties to each of the Documents
         and their respective transferees.

     14. The Documents may be executed in one or more counterparts, all of which
         taken together shall constitute one instrument. Signatures delivered by
         telecopy shall be binding, and the Parties hereto agree to send to the
         other originals of this Agreement (and the Documents) within
         twenty-four (24) hours of the closing of these transactions.

     15. The Documents are made and entered into in the State of Texas, and the
         laws of said state shall govern the validity and interpretation hereof
         and the performance of the Parties hereto of their respective duties
         and obligations hereunder.

     16. No breach of any provision hereof (or in the Documents) may be waived
         unless in writing executed by the affected Party(s) hereto and the
         waiver of any one breach shall not be deemed to be a waiver of any
         other breach of the same or any other provision hereof.

                                     Page 3
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     17. The Documents may be amended only by a written agreement executed by
         the respective Parties to each of this Agreement and the applicable
         Parties to the other Documents.

     18. The Documents are entered into for the express benefit of the Parties
         hereto, and it is not intended and shall not be deemed to create in any
         other person any rights or interest whatsoever, including without
         limitation, any rights to enforce the terms hereof.

     19. This Agreement (together with the other Documents) embodies the entire
         understanding of the Parties with respect to the matters set forth
         herein (and therein); and there are no further or other agreements or
         understandings, written or oral, in effect between the Parties hereto
         relating to the subject matter hereof, unless expressly referred to by
         reference herein or executed concurrently herewith.

     20. The Parties agree that the payments made, and obligations incurred, by
         Sonus to, or in favor of, TRLP constitutes reasonable equivalent value
         for the termination and modification of the lease agreements described
         herein, and agreements set forth herein (in accordance with the terms
         of this Agreement) and the restructuring of obligations provided for
         herein by TRLP and CCJV to Sonus and TTI. Sonus represents, warrants,
         and covenants that (i) the $1 million payment to TRLP as provided
         herein shall be paid solely from the funds of Sonus, and not the funds
         of TTI; (ii) the $1 million payment shall be wire-transferred by Sonus
         to TRLP, in care of Thompson Realty, on the Effective Date; and (iii)
         the $1 million payment represents a reasonable calculation of the costs
         to reimburse TRLP for its tenant improvements, lease termination costs,
         capital expenses, and build-out costs in connection with the premises
         covered by the leases terminated under this Agreement. The Parties
         agree that Hughes & Luce, L.L.P., shall serve as the escrow agent at
         the Closing of the transactions contemplated hereunder, and the escrow
         agent shall make the contemporaneous wire transfers described in this
         paragraph to the respective Parties at the Closing. At the Closing,
         CCJV shall wire transfer to TTI the sum of $165,236.50, as provided
         under EXHIBIT "A" of this Agreement, and Sonus shall wire transfer to
         TRLP, in care of Thompson Realty, the sum of $1,000,000, as provided in
         this Agreement.

     21. If the incurrence or payment of the obligations by either TTI or Sonus
         or the transfer to the Landlords of any property should for any reason
         subsequently be declared to be void or voidable under any state or
         federal law relating to creditors' rights, including provisions of the
         Bankruptcy Code relating to fraudulent conveyances, preferences, or
         other voidable or recoverable payments of money or transfers of
         property (collectively, a "VOIDABLE TRANSFER"), and if the Landlords
         are required to repay or restore, in whole or in part, any such
         Voidable Transfer, or elect to do so upon the reasonable advice of its
         or their counsel, then, as to any such Voidable Transfer, or the amount
         thereof that the Landlords are required or elect to repay or restore,
         and as to all reasonable costs, expenses, and attorneys fees of the
         Landlords related thereto, the liabilities and obligations of TTI and
         Sonus, arising out of or in any way related to the termination of lease
         obligations provided for above, or other releases granted in connection
         with this Agreement, automatically shall be revived, reinstated, and
         restored and shall exist as though such Voidable Transfer had never
         been made and this Agreement and the Documents had not been executed;
         provided, however, that notwithstanding the foregoing, (i) the payments
         made pursuant to paragraph 1 of this Agreement by the respective
         Parties hereto shall be returned or applied against any payments due or
         which became due after the Effective Date; (ii) all rights, titles, and
         interests of TTI in such leases terminated under the relevant Documents
         shall nonetheless be terminated and of no further force or effect upon
         the Effective Date of this Agreement; (iii) the Fifth Amendment to
         Office Lease Agreement shall remain in full force and effect and
         binding upon the Parties (but the liabilities of TTI with respect to
         such Office Lease Agreement prior to such Fifth Amendment shall be
         reinstated); and (iv) the Bill of Sale and Storage Agreement shall
         remain effective and binding upon such Parties.

                                     Page 4
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     22. TTI and Sonus each hereby acknowledges that as of the date hereof it
         has no defense, counterclaim, offset (except to the extent of payments
         made pursuant to this Agreement), cross-complaint, claim or demand of
         any kind or nature whatsoever that can be asserted to reduce or
         eliminate all or any part of its liability to repay the obligations or
         to seek affirmative relief or damages of any kind or nature from the
         Landlords or Thompson Realty, Thompson Realty Corporation, or each of
         the foregoing parties' respective affiliates, participants, partners,
         directors, officers, agents, employees, representatives or attorneys.
         TTI and Sonus each hereby voluntarily and knowingly releases and
         forever discharges the Landlords, Thompson Realty, Thompson Realty
         Corporation, and each of the foregoing parties' respective affiliates,
         participants, partners, agents, representatives, officers, directors,
         attorneys, employees, successors and assigns (collectively, the
         "LANDLORD RELEASEE GROUP"), from all possible claims, demands, actions,
         causes of action, damages, costs, expenses, and liabilities whatsoever,
         known or unknown, anticipated or unanticipated, suspected or
         unsuspected, fixed, contingent, or conditional, at law or in equity,
         originating in whole or in part on or before the date this Agreement
         becomes effective (collectively, the "LANDLORD CLAIMS"); PROVIDED,
         HOWEVER, that notwithstanding the foregoing, nothing herein shall
         release the Landlord Releasee Group from any obligations,
         representations, or covenants set forth in this Agreement, Leases 1, 2,
         and 3, or any of the other Documents, to the extent applicable to the
         particular member of the Landlord Releasee Group.

     23. Each of TTI and Sonus hereby covenants and agrees never to institute
         any action or suit at law or in equity, nor institute, prosecute, or in
         any way aid in the institution or prosecution of any claim, action or
         cause of action, rights to recover debts or demands of any nature
         against the Landlord Releasee Group, or any one of them, arising out of
         or related to the Landlord Claims.

     24. CCJV, TRLP, Thompson Realty, and Thompson Realty Corporation each
         hereby voluntarily and knowingly releases and forever discharges Sonus
         and TTI, and each of the foregoing parties' respective affiliates,
         participants, partners, agents, representatives, officers, directors,
         attorneys, employees, successors and assigns (collectively, the "TENANT
         RELEASEE GROUP"), from all possible claims, demands, actions, causes of
         action, damages, costs, expenses, and liabilities whatsoever, known or
         unknown, anticipated or unanticipated, suspected or unsuspected, fixed,
         contingent, or conditional, at law or in equity, originating in whole
         or in part on or before the date this Agreement becomes effective
         (collectively, the "TENANT CLAIMS"); PROVIDED, HOWEVER, that
         notwithstanding the foregoing, nothing herein shall release the Tenant
         Releasee Group from any obligations, representations, or covenants set
         forth in this Agreement, Lease 1, 2 and 3, the Guarantees, the Bill of
         Sale, the Storage Agreement, or any of the other Documents, to the
         extent applicable to the particular member of the Tenant Releasee
         Group.

     25. Each of CCJV, TRLP, Thompson Realty, and Thompson Realty Corporation
         hereby covenants and agrees never to institute any action or suit at
         law or in equity, nor institute, prosecute, or in any way aid in the
         institution or prosecution of any claim, action or cause of action,
         rights to recover debts or demands of any nature against the Tenant
         Releasee Group, or any one of them, arising out of or related to the
         Tenant Claims.

     This Agreement is executed as of March 5, 2002.

                        TR LOOKOUT PARTNERS, LTD.,
                         a Texas limited partnership

                        By:   Thompson Realty Investment Corporation,
                                general partner

                                     Page 5
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                                By:      /s/ W.T. Field
                                         ------------------------
                                         W.T. Field, President

                        COLLINS CAMPBELL JOINT VENTURE,
                            a Texas general partnership

                           By:      Jaytex Properties, Ltd.,
                                     a Texas limited partnership

                                    By:      JRS Management, Inc.

                                             By:      /s/ W.T. Field
                                                      ----------------------
                                                      W.T. Field, President

                           telecom technologies, inc.,
                            a Texas corporation

                           By:     /s/ G.M. Eastep
                                   ------------------------
                           Name:   G.M. Eastep
                                   ------------------------
                           Title:  Vice President and Chief Operating Officer
                                   -------------------------------------------

                           SONUS NETWORKS, INC.,
                            a Delaware corporation

                           By:     /s/ Peter S. Hemme
                                   ------------------------
                           Name:   Peter S. Hemme
                                   ------------------------
                           Title:  Vice President and Controller
                                   -----------------------------

AGREED AS TO PARAGRAPHS 24
AND 25 ONLY:

TH0MPSON REALTY INVESTMENT
CORPORATION, a Texas
corporation

By:     /s/ W.T. Field
        ------------------------
Name:   W.T. Field
        ------------------------
Title:  President
        ------------------------

TH0MPSON REALTY CORPORATION,
a Texas corporation

By:     /s/ W.T. Field
        ------------------------

                                     Page 6
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Name:   W.T. Field
        ------------------------
Title:  President
        ------------------------

                                     Page 7
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                                   EXHIBIT "A"

                      TERMINATION OF OFFICE LEASE AGREEMENT

     This Termination of Office Lease Agreement (this "Termination") is being
entered into as of February 28, 2002, by and between TR Lookout Partners, Ltd.
("Landlord") and telecom technologies, inc. ("Tenant").

                                R E C I T A L S:

     WHEREAS, Landlord and Tenant entered into that certain Office Lease
Agreement dated November 14, 2000, as amended by that certain First Amendment to
Office Lease Agreement dated as of January 8, 2001 (collectively, the "Lease")
with respect to approximately 119,966 square feet of space plus the Basement
Area (as defined and specified in the Lease) (the "Demised Premises") at 1301 E.
Lookout Drive, Richardson, Texas 75080;

     WHEREAS, Tenant has chosen not to occupy the Demised Premises;

     WHEREAS, Landlord and Tenant, among others, have entered into the terms of
a certain global agreement of even date herewith (the "Global Agreement"), and
Landlord and Tenant acknowledge and agree that the terms of the Global Agreement
shall be binding on the parties hereto;

     WHEREAS, Landlord and Tenant have reached certain agreements with respect
to the termination of the Lease; and

     WHEREAS, Landlord and Tenant now desire to set forth these certain
agreements with respect to the termination of the Lease and certain other
related matters.

     NOW, THEREFORE, in consideration of the covenants and agreements
hereinafter set forth and for other good and valuable consideration, the receipt
and adequacy of which are hereby acknowledged, Landlord and Tenant covenant and
agree to the above recitals and as follows:

     1.  Subject to the occurrence of all of the events set forth in the Global
Agreement in Paragraph 1 thereof, the Lease is terminated and Tenant shall no
longer have any right to occupy and/or use the Demised Premises.

     2.  Subject to the occurrence of all of the events set forth in the Global
Agreement in Paragraph 1 thereof, the Landlord hereby releases Tenant, Tenant's
parent company, Sonus Networks, Inc., and any and all guarantors of Tenant's
obligations under the Lease and from each and every obligation contained in the
Lease, including, but not limited to, the cost of various tenant improvements,
capital expenses, lease termination costs, and build out costs, or any guaranty
thereof. Subject to the occurrence of all of the events set forth in Paragraph 1
of the Global Agreement, Tenant hereby releases Landlord from any and all claims
Tenant might assert against Landlord relating in any way to the Lease or to
Tenant's occupancy of the Demised Premises. At closing, Landlord shall refund by
wire transfer to Tenant the prepaid rent held by Landlord in the amount of
$165,236.50.

     3.  The Global Agreement, and all of the terms therein, shall be
incorporated herein for all purposes.

                             EXHIBIT "A" Page 1 of 2
<Page>

     EXECUTED as of the date herein first written above.

                             LANDLORD:

                             TR Lookout Partners, Ltd.,
                              a Texas limited partnership

                             By:      Thompson Realty Investment Corporation,
                                          general partner

                                      By:     /s/ W.T. Field, President
                                              ------------------------
                                               W.T. Field, President

                             TENANT:

                             telecom technologies, inc.,
                               a Texas corporation

                             By:      /s/ G.M. Eastep
                                      --------------------------
                             Name:    G.M. Eastep
                                      --------------------------
                             Title:   Vice President and Chief
                                      Operating Officer
                                      --------------------------

                             EXHIBIT "A" Page 2 of 2
<Page>

                                   EXHIBIT "B"

                      TERMINATION OF OFFICE LEASE AGREEMENT

     This Termination of Office Lease Agreement (this "Termination") is being
entered into as of February 28, 2002, by and between Collins Campbell Joint
Venture ("Landlord") and telecom technologies, inc. ("Tenant").

                                R E C I T A L S:

     WHEREAS, Landlord and Tenant entered into that certain Office Lease
Agreement, dated January 25, 2000, as amended by that certain First Amendment to
Office Lease Agreement dated July 10, 2000 (collectively, the "Lease"),
concerning approximately 6,618 square feet of space (the "Premises") at 1701 N.
Collins, Suite 1050, Richardson, Dallas County, Texas 75080;

     WHEREAS, Tenant has chosen to vacate the Premises;

     WHEREAS, Landlord and Tenant, among others, have entered into the terms of
a certain global agreement of even date herewith (the "Global Agreement"), and
Landlord and Tenant acknowledge and agree that the terms of the Global Agreement
shall be binding on the parties hereto;

     WHEREAS, Landlord and Tenant have reached certain agreements with respect
to a termination of the Lease; and

     WHEREAS, Landlord and Tenant now desire to set forth these certain
agreements with respect to the termination of the Lease and certain other
related matters.

     NOW, THEREFORE, in consideration of the covenants and agreements
hereinafter set forth and for other good and valuable consideration, the receipt
and adequacy of which are hereby acknowledged, Landlord and Tenant covenant and
agree to the above recitals, and as follows:

     1.  Subject to the occurrence of all of the events set forth in the Global
Agreement in Paragraph 1 thereof, the Lease is terminated and Tenant shall no
longer have any right to occupy and/or use the Premises.

     2.  Subject to the occurrence of all of the events set forth in the Global
Agreement in Paragraph 1 thereof, Landlord hereby releases Tenant, Tenant's
parent company, Sonus Networks, Inc., and any and all guarantors of Tenant's
obligations under the Lease and from each and every obligation contained in the
Lease, including, but not limited to, the cost of various tenant improvements,
capital expenses, lease termination costs, and build out costs, or any guaranty
thereof. Subject to the occurrence of all of the events set forth in the Global
Agreement in Paragraph 1 thereof, Tenant hereby releases Landlord from any and
all claims Tenant might assert against Landlord relating in any way to the Lease
or to Tenant's occupancy of the Premises.

     3.  The Global Agreement, and all of the terms therein, shall be
incorporated herein for all purposes.

                             EXHIBIT "B" Page 1 of 2
<Page>

     EXECUTED as of the date herein first written above.

                             LANDLORD:

                             Collins Campbell Joint Venture,
                                     a Texas general partnership

                             By:      Jaytex Properties, Ltd.,
                                      a Texas limited partnership

                                      By:      JRS Management, Inc.,
                                               a Texas corporation

                                               By:      /s/ W.T. Field
                                                        ---------------------
                                                        W.T. Field, President

                             TENANT:

                             telecom technologies, inc.,
                              a Texas corporation

                             By:      /s/ G.M. Eastep
                                      --------------------------
                             Name:    G.M. Eastep
                                      --------------------------
                             Title:   Vice President and Chief Operating
                                      Officer
                                      ------------------------------------

                             EXHIBIT "B" Page 2 of 2
<Page>

                                   EXHIBIT "C"

                    FIFTH AMENDMENT TO OFFICE LEASE AGREEMENT

     THIS FIFTH AMENDMENT TO OFFICE LEASE AGREEMENT (this "Fifth Amendment") is
made and entered into effective as of February 28, 2002, by and between Collins
Campbell Joint Venture ("Landlord") and telecom technologies, inc. ("Tenant").

                                 R E C I T A L S

     WHEREAS, Landlord and Tenant entered into that certain Office Lease
Agreement, dated as of April 4, 1997, as amended by (i) that certain First
Amendment to Office Lease Agreement, dated as of November 1, 1997; (ii) those
certain Second and Third Amendments to Office Lease Agreement, each dated as of
July 1, 1998; and (iii) that certain Fourth Amendment to Office Lease Agreement,
dated February 1, 1999 (collectively, the "Lease"), with respect to certain
Premises defined therein and commonly known as Suite 3000 at 1701 North Collins
Blvd., Richardson, Dallas County, Texas 75080, which Lease is incorporated
herein by reference;

     WHEREAS, Landlord and Tenant, among others, have entered into the terms of
a certain global agreement of even date herewith (the "GLOBAL AGREEMENT"), and
Landlord and Tenant acknowledge and agree that the terms of the Global Agreement
shall be binding on the parties hereto;

     WHEREAS, Landlord and Tenant desire to further amend the Lease to reduce
the size of the Premises.

     NOW, THEREFORE, in consideration of the mutual agreements herein set forth,
the mutual agreements set forth in the Lease, and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged,
Landlord and Tenant have agreed, and do hereby agree, to the above Recitals, and
as follows, subject to the occurrence of all of the events set forth in
Paragraph 1 of the Global Agreement:

     1.  All terms used herein and not specifically defined shall have the same
         meanings herein as is ascribed to them in the Lease.

     2.  The Premises are hereby reduced to approximately 20,227 square feet of
         rentable area by deleting approximately 17,789 square feet of rentable
         area on the second floor, such "Give Back Space" being described on
         Exhibit "A", attached hereto and incorporated herein for all purposes.

     3.  Basic rental is decreased from $3,909,279.04 to $3,475,939.00.

     4.  The monthly rental installment is decreased as set forth below:

         Monthly from March 1, 2002 through October 31, 2002 - $35,043.28
         Monthly from November 1, 2002 through April 30, 2003 - $35,397.25

     5.  Tenant's option to extend the term of the Lease set forth in Rider 101
         is hereby eliminated and of no further force or effect.

     6.  Except as herein provided to the contrary, Tenant's lease of the
         Premises from Landlord shall be on the same terms and conditions as
         those specified in the Lease.

     7.  The Lease (as amended by this Fifth Amendment) remains in full force
         and effect and is hereby ratified and affirmed.

                             EXHIBIT "C" Page 1 of 2
<Page>

     8.  All notices required to be sent to the Tenant shall also be sent to
         Sonus Networks, Inc., 5 Carlisle Road, Westford, Massachusetts 01886;
         Attention: Chief Financial Officer.

     9.  The Global Agreement, and all of the terms therein, shall be
         incorporated herein for all purposes. To the extent that there is a
         conflict between the terms of this Fifth Amendment and the terms of the
         Global Agreement with respect to the relevant subject matter, the terms
         of this Fifth Amendment shall control.

     IN WITNESS WHEREOF, this Fifth Amendment is hereby executed as of the day
and year first set forth above.

                             LANDLORD:

                             COLLINS CAMPBELL JOINT VENTURE,
                              a Texas general partnership

                             By:  Jaytex Properties, Ltd.,
                                   a Texas limited partnership

                                  By:  JRS Management, Inc.

                                               By:      /s/ W.T. Field
                                                        ---------------------
                                                        W.T. Field, President

                             TENANT:

                             telecom technologies, inc.,
                              a Texas corporation

                             By:      /s/ G.M. Eastep
                                      --------------------------
                             Name:    G.M. Eastep
                                      --------------------------
                             Title:   Vice President and Chief Operating
                                      Officer
                                      ------------------------------------

                             EXHIBIT "C" Page 2 of 2
<Page>

            EXHIBIT "A" TO FIFTH AMENDMENT TO OFFICE LEASE AGREEMENT

          [DESCRIPTION OF "GIVE BACK SPACE" TO BE PROVIDE BY LANDLORD]'

      EXHIBIT "A" TO FIFTH AMENDMENT TO OFFICE LEASE AGREEMENT Page 1 of 2
<Page>

                                   EXHIBIT "D"

                                    GUARANTEE

     In connection with that certain Global Agreement, dated as of March 5,
2002, by and among TR Lookout Partners, Ltd., Collins Campbell Joint Venture,
telecom technologies, inc., Sonus Networks, Inc., the undersigned hereby
unconditionally guarantees the full payment and performance of and agrees to pay
and perform as primary obligor all liabilities, obligations and duties
(including, but not limited to, payment of rent) imposed upon telecom
technologies, inc. ("Tenant") under the terms of those three (3) certain leases
(collectively, the "Leases"), as more fully described below, as if the
undersigned had executed the Leases, as Tenant thereunder:

                                GUARANTEED LEASES

     1.  Office Lease Agreement, dated April 4, 1997, by and between Landlord
         and Tenant, as amended by that certain Fourth Amendment to Office Lease
         Agreement dated February 1, 1999, to be amended by that certain Fifth
         Amendment to Office Lease Agreement, concerning approximately 20, 227
         square feet, Suite 3000, Richardson, Texas 75080;

     2.  Office Lease Agreement, dated January 25, 2000, by and between Landlord
         and Tenant, concerning approximately 2,281 square feet, Suite 339,
         Richardson, Texas 75080; and

     3.  Office Lease Agreement, dated October 14, 1999, as amended by that
         certain First Amendment to Office Lease Agreement dated June 15, 2000,
         by and between Landlord and Tenant, concerning approximately 2,055
         square feet, Suite 2400, Richardson, Texas 75080.

     The undersigned hereby waives notice of acceptance of this guarantee and
all other notices in connection herewith or in connection with the liabilities,
obligations, and duties guaranteed hereby, including notices of default by
Tenant under the Leases, and waives diligence, presentment, and suit on the part
of Collins Campbell Joint Venture ("Landlord") in the enforcement of any
liability, obligation or duty guaranteed hereby.

     The undersigned further agrees that Landlord shall not be first required to
enforce against Tenant or any other person any liability, obligation or duty
guaranteed hereby before seeking enforcement thereof against the undersigned.
Suit may be brought and maintained against the undersigned by Landlord to
enforce any liability, obligation or duty guaranteed hereby without joinder of
Tenant or any other person. The liability of the undersigned shall not be
affected by any indulgence, compromise, settlement or variation of terms which
may be extended to the Tenant by the Landlord or agreed upon by the Landlord and
the Tenant, and shall not be affected by any termination of the Leases, to the
extent that the Tenant thereafter continues to be liable thereunder. Landlord
and Tenant, without notice to or consent by the undersigned, may at any time or
times enter into such modifications, extensions, amendments, or other covenants
respecting the Leases, as they may deem appropriate and the undersigned shall
not be released thereby, but shall continue to be fully liable for the payment
and performance of all liabilities, obligations and duties of Tenant under the
Leases, as so further modified, extended or amended; PROVIDED, HOWEVER, that the
undersigned shall not be bound by any modifications, extensions, amendments, or
any other covenants respecting the Leases prior to Landlord's notice to the
undersigned of same, and upon notice to the undersigned of the foregoing, the
undersigned shall be bound by and liable to Landlord under the terms thereof.
Notice to the undersigned shall be sufficient, if sent to Sonus Networks, Inc.,
5 Carlisle Road, Westford, Massachusetts 01886; Attention: Chief Financial
Officer.

     This agreement shall be binding upon the undersigned and the successors,
heirs, executors, and administrators of the undersigned, and shall inure to the
benefit of the Landlord and its heirs, executors, administrators and assigns.

                             EXHIBIT "D" Page 1 of 2
<Page>

     EXECUTED this 5th day of March, 2002.

                             Guarantor:

                             Sonus Networks, Inc.,
                              a Delaware corporation

                             By:      /s/ Peter S. Hemme
                                      --------------------------
                             Name:    Peter S. Hemme
                                      --------------------------
                             Title:   Vice President and Controller
                                      --------------------------

                             EXHIBIT "D" Page 2 of 2
<Page>

                                   EXHIBIT "E"

                    BILL OF SALE OF CERTAIN PERSONAL PROPERTY

     This Bill Of Sale Of Certain Personal Property (this "BILL OF SALE") is
made this 30th day of April, 2003, by telecom technologies, inc., a Texas
corporation ("SELLER"), to and in favor of Collins Campbell Joint Venture
("PURCHASER"), and Sonus Networks, Inc. ("SONUS").

     WHEREAS, Seller, Sonus, and Purchaser, among others, have entered into the
terms of a certain global agreement, dated March 5, 2002, (the "GLOBAL
AGREEMENT"), and Seller, Sonus, and Purchaser acknowledge and agree that the
terms of the Global Agreement shall be binding on the parties hereto;

     WHEREAS, Seller has sold to Purchaser, and Purchaser has agreed to purchase
from Seller, various items of furniture, fixtures, and equipment, and other
personal property located on the premises at Suite 3000, 1701 North Collins
Boulevard, Richardson, Texas 75080, which are more particularly described on
EXHIBIT "A" attached to this Bill of Sale and made a part hereof (collectively,
the "PERSONAL PROPERTY").

     NOW, THEREFORE, for and in consideration of the payment of in the amount of
Ten and No/100 Dollars ($10.00) and other good and valuable consideration,
including the mutual covenants and agreements between and among Seller, Sonus,
and Purchaser in the Global Agreement, the receipt and sufficiency of which are
hereby acknowledged, and in further consideration of the mutual covenants and
agreements contained herein, Seller, Sonus, and Purchaser hereby agree to the
above recitals, and Seller does hereby sell, assign, transfer and convey to
Purchaser and its successors and assigns, all of the Personal Property. The
parties hereto agree that to the extent that such sale of assets provided
hereunder requires that sales tax be paid to any appropriate taxing authorities
on account of such transaction, the Purchaser agrees to assume such obligations.

     TO HAVE AND TO HOLD the Personal Property unto Purchaser, its successors
and assigns, for their exclusive use and benefit forever. Seller warrants that
it has good and marketable title to the Personal Property, free and clear of all
mortgages, liens, charges and encumbrances (including any ad valorem taxes) as
of the effective date of this Bill of Sale.

     Seller hereby assigns to Purchaser any and all service agreements,
warranties, operating agreements, maintenance agreements, manuals, plans, and
all similar and other documents relating to the Personal Property which are in
the possession or under the control of Seller, to the extent that the same may
be assigned (collectively, "SERVICE AGREEMENTS"). Seller shall deliver to
Purchaser copies of all of the Service Agreements at the time of the closing of
the sale, unless otherwise agreed to by Seller and Purchaser in writing.

     Such transfers and assignments provided herein shall be without recourse or
liability to the Purchaser, and shall not constitute, nor be deemed to be, any
assumption by the Purchaser of any obligations, liabilities, or indebtedness of
the Seller arising out of or in connection with the Personal Property or Service
Agreements to be transferred under this Bill of Sale.

     This instrument and the Documents (as defined in the Global Agreement)
contain the entire agreement and understanding between Purchaser and Seller as
to the Personal Property conveyed by this Bill of Sale. No addition, or
amendment, alteration, modification or waiver of, any provisions of this Bill of
Sale shall be of any force or effect unless in writing and signed by Purchaser
and Seller or their duly authorized representatives.

                             EXHIBIT "E" Page 1 of 2
<Page>

     Sonus agrees to indemnify and hold harmless the Purchaser, and pay
Purchaser any losses, costs, fees, liabilities or expense (including attorney's
fees) arising out of Seller's failure to meet its obligations under this
agreement.

     IN WITNESS WHEREOF, Seller, Sonus, and Purchaser have caused this
instrument to be duly executed as of the date first written above.

                             SELLER:

                             telecom technologies, inc.,
                                a Texas corporation

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

                             SONUS:

                             SONUS NETWORKS, INC.,
                                a Delaware corporation

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

                             PURCHASER:

                             COLLINS CAMPBELL JOINT VENTURE,
                              a Texas general partnership

                             By:      Jaytex Properties, Ltd.,
                                       a Texas limited partnership

                                      By:      JRS Management, Inc.

                                               By:
                                                        ----------------------
                                                        W.T. Field, President

                             EXHIBIT "E" Page 2 of 2
<Page>

                           EXHIBIT "A" TO BILL OF SALE

                            LIST OF PERSONAL PROPERTY

                 [TO BE PROVIDED BY TELECOM TECHNOLOGIES, INC.]

                             EXHIBIT "E" Page 3 of 2
<Page>

                                   EXHIBIT "F"

                     STORAGE AGREEMENT OF PERSONAL PROPERTY

     This Storage Agreement of Personal Property (this "STORAGE AGREEMENT") is
made this 5th day of March, 2002, by telecom technologies, inc., a Texas
corporation ("TENANT"), to and in favor of Collins Campbell Joint Venture
("LANDLORD").

                                   WITNESSETH:

     That, for and in consideration of the sum of Ten and No/100 Dollars
($10.00) and other good and valuable consideration, the receipt and sufficiency
of which are hereby acknowledged by Tenant, Tenant and Landlord agree that
Tenant may store all of the personal property (the "PERSONAL PROPERTY"),
described on EXHIBIT "A" hereto.

     Tenant and Landlord agree that Tenant shall have the right to store the
Personal Property, without any fee or charge payable to Landlord, for the period
from the effective date of that certain Global Agreement of even date herewith,
by and among Tenant, Landlord, and others, and continuing for the period through
and including the earlier of (i) April 30, 2003, or (ii) the Removal Date (as
defined below).

     Upon twenty (20) calendar days' prior written notice by the Landlord to the
Tenant (the "REMOVAL DATE"), Tenant shall immediately thereafter remove all of
the Personal Property from the premises of the Landlord, and the Tenant shall
indemnify and hold harmless the Landlord from any damages, losses, or claims of
the Landlord, caused by the removal of the Personal Property from the premises
of the Landlord.

     At any time or from time to time after the date hereof, the parties shall
execute and deliver or cause to be executed and delivered to each other such
other instruments and take or cause to be taken such other actions as may
reasonably be requested in order to carry out the intent and purposes of this
Storage Agreement.

     During the term of this Storage Agreement, Tenant shall maintain and insure
the Personal Property.

     In the event that Landlord enters into a new lease with one or more tenants
for the space where the Personal Property is presently stored, Tenant agrees to
exercise best efforts to reach agreements with such Tenants for the sale and/or
lease of the Personal Property, upon reasonable commercial terms acceptable to
such parties, to facilitate the efforts of the Landlord in leasing such space to
the new tenants.

     Such right of storage shall be without recourse or liability to Landlord
(or its successors and assigns), and shall not constitute, nor be deemed to be,
any assumption by Landlord (or its successors and assigns) of any obligations,
liabilities, or indebtedness of Tenant on or under the Personal Property Leases.

     No addition, or amendment, alteration, modification or waiver of, any
provisions of this Storage Agreement shall be of any force or effect unless in
writing and signed by Tenant and Landlord or their duly authorized
representatives.

                             EXHIBIT "F" Page 1 of 2
<Page>

     IN WITNESS WHEREOF, the undersigned have caused this instrument to be duly
executed as of the date first written above.

                             TENANT:

                             telecom technologies, inc.,
                              a Texas corporation

                             By:     /s/ Peter S. Hemme
                                     ------------------------
                             Name:   Peter S. Hemme
                                     ------------------------
                             Title:  Treasurer
                                     ------------------------

                             LANDLORD:

                             COLLINS CAMPBELL JOINT VENTURE,
                              a Texas general partnership

                             By:      Jaytex Properties, Ltd.,
                                       a Texas limited partnership

                                      By:      JRS Management, Inc.

                                               By: /s/ Kelly P.B. Drabbs
                                                   ----------------------
                                                   Vice President

EXHIBITS

A    -   List of Personal Property [TO BE PROVIDED BY TENANT]

                             EXHIBIT "F" Page 2 of 2
<Page>

                                   EXHIBIT "G"

                                    GUARANTEE

     In connection with that certain Global Agreement, dated as of March 5,
2002 (the "Global Agreement"), by and among TR Lookout Partners, Ltd., Collins
Campbell Joint Venture ("CCJV"), telecom technologies, inc. ("TTI"), Sonus
Networks, Inc., the undersigned hereby unconditionally guarantees the full
payment and performance of and agrees to pay and perform as primary obligor all
liabilities, obligations and duties (including, but not limited to, payment of
rent) imposed upon telecom technologies, inc. ("TTI") under the terms of the
following agreements (collectively, the "Agreements"), as if the undersigned had
executed the Agreements:

                              GUARANTEED AGREEMENTS

     1.  The obligations of TTI to CCJV under Paragraph 7 of the Global
         Agreement;

     2.  The obligations of TTI to CCJV under the Bill of Sale, attached as
         Exhibit "E" to the Global Agreement; and

     3.  The obligations of TTI to CCJV under the Storage Agreement, attached as
         Exhibit "F" to the Global Agreement.

     The undersigned hereby waives notice of acceptance of this guarantee and
all other notices in connection herewith or in connection with the liabilities,
obligations, and duties guaranteed hereby, including notices of default by TTI
under the Agreements, and waives diligence, presentment, and suit on the part of
CCJV in the enforcement of any liability, obligation or duty guaranteed hereby.

     The undersigned further agrees that CCJV shall not be first required to
enforce against TTI or any other person, any liability, obligation or duty
guaranteed hereby before seeking enforcement thereof against the undersigned.
Suit may be brought and maintained against the undersigned by CCJV to enforce
any liability, obligation or duty guaranteed hereby without joinder of TTI or
any other person. The liability of the undersigned shall not be affected by any
indulgence, compromise, settlement or variation of terms which may be extended
to TTI by CCJV or agreed upon by CCJV and TTI, and shall not be affected by any
termination of and of the Agreements, to the extent that TTI thereafter
continues to be liable thereunder. CCJV and TTI, without notice to or consent by
the undersigned, may at any time or times enter into such modifications,
extensions, amendments, or other covenants respecting the Agreements, as they
may deem appropriate and the undersigned shall not be released thereby, but
shall continue to be fully liable for the payment and performance of all
liabilities, obligations and duties of TTI under the Agreements, as so further
modified, extended or amended; PROVIDED, HOWEVER, that the undersigned shall not
be bound by any modifications, extensions, amendments, or any other covenants
respecting the Agreements prior to CCJV's notice to the undersigned of same, and
upon notice to the undersigned of the foregoing, the undersigned shall be bound
by and liable to CCJV under the terms thereof. Notice to the undersigned shall
be sufficient, if sent to Sonus Networks, Inc., 5 Carlisle Road, Westford,
Massachusetts 01886; Attention: Chief Financial Officer.

     This agreement shall be binding upon the undersigned and the successors,
heirs, executors, and administrators of the undersigned, and shall inure to the
benefit of CCJV and its heirs, executors, administrators and assigns.

                             EXHIBIT "G" Page 1 of 2
<Page>

     EXECUTED this 5th day of March, 2002.

                             Guarantor:

                             Sonus Networks, Inc.,
                                a Delaware corporation

                             By:     /s/ Peter S. Hemme
                                     ------------------------
                             Name:   Peter S. Hemme
                                     ------------------------
                             Title:  Vice President and Controller
                                     -----------------------------

                             EXHIBIT "G" Page 2 of 2
<Page>

                                   EXHIBIT "H"

                     [CONSENT BY LENDER TO TRLP TERMINATION]

                                 March 5, 2002

James Reynolds
Texas Capital Bank, National Association
2100 McKinney Ave., Suite 900
Dallas, Texas 75201

RE:      Termination of Office Lease Agreement (the "Termination") by and
         between TR Lookout Partners, Ltd. ("Landlord") and telecom
         technologies, inc. ("Tenant")

Ladies and Gentlemen:

     The Termination attached hereto has been consented to by Texas Capital
Bank, National Association ("Lender"). Lender holds the first lien on the
building affected by the Termination. Please sign where indicated below to
evidence your consent in writing to the Termination.

                             Very truly yours

                             TR Lookout Partners, Ltd.,
                              a Texas limited partnership

                             By:      Thompson Realty Investment Corporation

                                      By:      /s/ W.T. Field
                                               ---------------------
                                               W.T. Field, President

                             telecom technologies, inc.,
                               a Texas corporation

                             By:    /s/ G.M. Eastep
                                    ---------------------
                              Name: G.M. Eastep
                                    ---------------------
                              Title: Vice President and Chief Operating
                                     Officer
                                    -----------------------------------

ACCEPTED AND AGREED TO:

Texas Capital Bank, National Association
By:  /s/ James R. Reynolds
     -----------------------------
Name: James R. Reynolds
         -------------------------
Title:  SVP
      ----------------------------

                             EXHIBIT "H" Page 1 of 1
<Page>

                                   EXHIBIT "I"

           [CONSENT BY LENDER TO CCJV TERMINATION AND FIFTH AMENDMENT]

                                 March 5, 2002

Principal Life Insurance Company
C/O Principal Financial Group
Des Moines, IA 50392-1360

RE:      Termination of Office Lease Agreement (the "Termination") and Fifth
         Amendment to Office Lease Agreement (the "Amendment"), both by and
         between Collins Campbell Joint Venture ("Landlord") and telecom
         technologies, inc. ("Tenant")

Ladies and Gentlemen:

     The Termination and the Amendment attached hereto have been consented to by
Principal Life Insurance Company ("Lender"). Lender holds the first lien on the
building affected by the Termination and the Amendment. Please sign where
indicated below to evidence your consent in writing to the Termination and the
Amendment.

                             Very truly yours

                             COLLINS CAMPBELL JOINT VENTURE,
                              a Texas general partnership
                             By:      Jaytex Properties, Ltd.,
                                      a Texas limited partnership
                             By:      JRS Management, Inc.

                                      By:      /s/ W.T. Field
                                               ---------------------
                                               W.T. Field, President

                             telecom technologies, inc.,
                              a Texas corporation

                             By:      /s/ G.M. Eastep
                                      -------------------
                             Name:    G.M. Eastep
                                      -------------------
                             Title:   Vice President and Chief
                                      Operating Officer
                                      ----------------------

ACCEPTED AND AGREED TO:

PRINCIPAL LIFE INSURANCE COMPANY,
 an Iowa corporation

By:  /s/ Deborah A. Reinhard
     -----------------------------
Name: Deborah A. Reinhard
     -----------------------------
Title: Senior Loan Administrator
      ----------------------------

                             EXHIBIT "I" Page 1 of 1
<Page>

                                   EXHIBIT "J"

                           LIMITED INDEMNITY AGREEMENT

     This Limited Indemnity Agreement (this "INDEMNITY") is entered into this
5th day of March, 2002, by and among Collins Campbell Joint Venture ("CCJV"),
telecom technologies, inc., a Texas corporation ("TTI"), and Sonus Networks,
Inc. ("SONUS").

     WHEREAS, CCJV entered into a certain letter agreement, dated April 4, 1997
(the "AGREEMENT"), with Hamid Ansari and Anousheh Ansari (collectively, the
"ANSARIS"), as amended by that certain letter agreement, dated November 1, 2000
(the "AMENDED AGREEMENT"), by and between the Ansaris and CCJV;

     WHEREAS, the Agreement and the Amended Agreement (collectively, the "LETTER
AGREEMENTS") provide for the payment by CCJV of a certain profit fee to the
Ansaris under certain conditions and circumstances more fully described in the
Letter Agreements, and which circumstances and conditions have not occurred as
of this date and may not occur;

     WHEREAS, TTI has consented to the terms of the Letter Agreements, but is
not obligated to make any payments under the same to the Ansaris, nor has TTI
agreed to perform any obligations under the Letter Agreements; and

     WHEREAS, CCJV, TTI, and Sonus, among others, have entered into the terms of
a certain global agreement, dated March 5, 2002, (the "GLOBAL AGREEMENT"), and
CCJV, TTI, and Sonus acknowledge and agree that the terms of the Global
Agreement shall be binding on the parties hereto;

     NOW, THEREFORE, for and in consideration of the payment in the amount of
Ten and No/100 Dollars ($10.00) and other good and valuable consideration,
including the mutual covenants and agreements between and among CCJV, TTI, and
Sonus in the Global Agreement, the receipt and sufficiency of which are hereby
acknowledged, and in further consideration of the mutual covenants and
agreements contained herein, CCJV, TTI, and Sonus hereby agree to the above
Recitals and as follows:

     1.  This Limited Indemnity Agreement shall be subject to the occurrence of
all of the events set forth in the Global Agreement in Paragraph 1 thereof.

     2.  Subject to paragraph 3 below, CCJV agrees to (i) defend Sonus and TTI
against any claims, suits or actions brought by the Ansaris (or either one of
them) against Sonus or TTI for performance of TTI's obligations, if any, in the
Letter Agreements (the "ANSARI CLAIMS"), and (ii) indemnify Sonus and TTI
against any damages, liabilities, costs and expenses (including reasonable
attorneys' fees) awarded by a court of final jurisdiction arising out of the
Ansari Claims. CCJV shall assume the defense of the Ansari Claims against Sonus
and TTI by counsel retained at CCJV's own expense.

     3.  CCJV's indemnification obligation is conditioned on Sonus' and TTI's
compliance with the following procedures: (a) Sonus and TTI will promptly notify
CCJV in writing of any claim or the commencement of any suit, action, proceeding
or threat that Sonus and TTI believe will result in costs for which TTI or Sonus
will be entitled to indemnification; (b) Sonus and TTI will tender to CCJV (and
its insurer) full authority to defend or settle any such claim; and (c) Sonus
and TTI shall cooperate in the defense of such claim. CCJV has no obligation to
indemnify Sonus and TTI in connection with any settlement made without CCJV's
written consent.

                             EXHIBIT "J" Page 1 of 2
<Page>

     IN WITNESS WHEREOF, CCJV, Sonus, and TTI have executed this Limited
Indemnity Agreement as of the date first written above.

                             TTI:

                             telecom technologies, inc.,
                               a Texas corporation

                             By:     /s/ G.M. Eastep
                                     -------------------------
                             Name:   G.M. Eastep
                                     -------------------------
                             Title:  Vice President and Chief Operating
                                     Officer
                                     -----------------------------------

                             SONUS:

                             SONUS NETWORKS, INC.,
                                a Delaware corporation

                             By:     /s/ Peter S. Hemme
                                     -------------------------
                             Name:   Peter S. Hemme
                                     -------------------------
                             Title:  Vice President and Controller
                                     ------------------------------

                             CCJV:

                             COLLINS CAMPBELL JOINT VENTURE,
                               a Texas general partnership

                             By:      Jaytex Properties, Ltd.,
                                       a Texas limited partnership

                                      By:      JRS Management, Inc.

                                               By:      /s/ W.T. Field
                                                        ----------------------
                                                        W.T. Field, President

                            EXHIBIT "J" Page 2 of 2<Page>

                                  EXHIBIT 10.25

                           LOAN AND SECURITY AGREEMENT

     This LOAN AND SECURITY AGREEMENT (this "Agreement") between SILICON
VALLEY BANK, a California chartered bank, with its principal place of
business at 3003 Tasman Drive, Santa Clara, California 95054 and with a loan
production office located at One Newton Executive Park, Suite 200, 2221
Washington Street, Newton, Massachusetts 02462, doing business under the name
"Silicon Valley East" ("Bank") and SONUS NETWORKS, INC., a Delaware
corporation with its chief executive office located at 5 Carlisle Road,
Westford, Massachusetts 01886 ("Borrower"), provides the terms on which Bank
shall lend to Borrower and Borrower shall repay Bank. The parties agree as
follows:

     1         ACCOUNTING AND OTHER TERMS

     Accounting terms not defined in this Agreement shall be construed following
GAAP. Calculations and determinations must be made following GAAP. The term
"financial statements" includes the notes and schedules, if any. The terms
"including" and "includes" always mean "including (or includes) without
limitation," in this or any Loan Document. Capitalized terms in this Agreement
shall have the meanings set forth in Section 13.

     2         LOAN AND TERMS OF PAYMENT

     2.1  PROMISE TO PAY. Borrower hereby unconditionally promises to pay Bank
the unpaid principal amount of all Credit Extensions and interest on the unpaid
principal amount of the Credit Extensions as and when due in accordance with
this Agreement.

     2.1.1     Revolving Advances.

               (a)  Bank shall make Advances not exceeding (i) the lesser of
Committed Revolving Line or, if Borrower's Tangible Net Worth at any time falls
below the TNW Threshold, the Borrowing Base, MINUS (ii) the amount of all
outstanding Letters of Credit (including drawn but unreimbursed Letters of
Credit), MINUS (iii) the FX Reserve, AND MINUS (iv) the aggregate outstanding
Advances hereunder (including any Cash Management Services). Amounts borrowed
under this Section may be repaid and reborrowed during the term of this
Agreement.

               (b)  To obtain an Advance, Borrower must notify Bank by facsimile
or telephone by 3:00 p.m. Eastern time on the Business Day the Advance is to be
made. If such notification is by telephone, Borrower must promptly confirm the
notification by delivering to Bank a completed Payment/Advance Form in the form
attached as EXHIBIT B. Bank shall credit Advances to Borrower's deposit account.
Bank may make Advances under this Agreement based on instructions from a
Responsible Officer or his or her designee or without instructions if the
Advances are necessary to meet Obligations which have become due. Bank may rely
on any telephone notice given by a person whom Bank reasonably believes is a
Responsible Officer or designee. Borrower shall indemnify Bank for any loss Bank
suffers due to such reliance.

               (c)  The Committed Revolving Line terminates on the Revolving
Maturity Date, when the principal amount of all Advances and the unpaid interest
thereon, shall be immediately payable.

LETTERS OF CREDIT SUBLIMIT.

               (d)  Subject to the availability of Credit Extensions in Section
2.1.1(a), Bank shall issue or have issued Letters of Credit for Borrower's
account not exceeding: (i) the lesser of Committed Revolving Line or, if
Borrower's Tangible Net Worth at any time falls below the TNW Threshold, the
Borrowing Base, MINUS (ii) the outstanding principal balance of any Advances
(including any Cash Management Services), MINUS (iii) the FX Reserve, MINUS (iv)
the amount of all Letters of Credit (including drawn but unreimbursed Letters of
Credit), PLUS (v) an amount equal to any Letter of Credit Reserves. Without
limiting the foregoing, the face amount of

<Page>

outstanding Letters of Credit (including drawn but unreimbursed Letters of
Credit and any Letter of Credit Reserve) may not exceed One Million Dollars
($1,000,000.00). Each Letter of Credit shall have an expiry date no later than
180 days after the Revolving Maturity Date provided Borrower's Letter of Credit
reimbursement obligation shall be secured by cash on terms acceptable to Bank at
all times on and after (i) the Revolving Maturity Date if the term of the
Committed Revolving Line is not extended by Bank, or (ii) the occurrence of an
Event of Default hereunder. All Letters of Credit shall be, in form and
substance, acceptable to Bank in its sole discretion and shall be subject to the
terms and conditions of Bank's form of standard Application and Letter of Credit
Agreement. Borrower agrees to execute any further documentation in connection
with the Letters of Credit as Bank may reasonably request.

               (e)  The obligation of Borrower to immediately reimburse Bank for
drawings made under Letters of Credit shall be absolute, unconditional and
irrevocable, and shall be performed strictly in accordance with the terms of
this Agreement and such Letters of Credit, under all circumstances whatsoever.
Borrower shall indemnify, defend, protect, and hold Bank harmless from any loss,
cost, expense or liability, including, without limitation, reasonable attorneys'
fees, arising out of or in connection with any Letters of Credit.

               (f)  Borrower may request that Bank issue a Letter of Credit
payable in a currency other than United States Dollars. If a demand for payment
is made under any such Letter of Credit, Bank shall treat such demand as an
Advance to Borrower of the equivalent of the amount thereof (plus cable charges)
in United States currency at the then prevailing rate of exchange in San
Francisco, California, for sales of that other currency for cable transfer to
the country of which it is the currency.

               (g)  Upon the issuance of any letter of credit payable in a
currency other than United States Dollars, Bank shall create a reserve (the
"Letter of Credit Reserve") under the Committed Revolving Line for letters of
credit against fluctuations in currency exchange rates, in an amount equal to
ten percent (10%) of the face amount of such letter of credit. The amount of
such reserve may be amended by Bank from time to time to account for
fluctuations in the exchange rate. The availability of funds under the Committed
Revolving Line shall be reduced by the amount of such reserve for so long as
such letter of credit remains outstanding.

FOREIGN EXCHANGE SUBLIMIT. If there is availability for Credit Extensions under
Section 2.1.1(a), then Borrower may enter in foreign exchange forward contracts
with the Bank under which Borrower commits to purchase from or sell to Bank a
set amount of foreign currency more than one business day after the contract
date (the "FX Forward Contract"). Bank shall subtract 10% of each outstanding FX
Forward Contract as the foreign exchange sublimit, which sublimit is a maximum
of One Million Dollars ($1,000,000.00) (the "FX Reserve"). The total FX Forward
Contracts at any one time may not exceed 10 times the amount of the FX Reserve.
Bank may terminate the FX Forward Contracts if an Event of Default occurs. Any
outstanding amounts payable to the Bank under the FX Forward Contracts shall be
paid in full, or, if agreed to by Bank, secured by cash on terms acceptable to
Bank at all times on and after (i) the Revolving Maturity Date if the term of
the Committed Revolving Line is not extended by Bank, or (ii) the occurrence of
an Event of Default hereunder.

     2.1.2     CASH MANAGEMENT SERVICES SUBLIMIT. Subject to the availability of
Credit Extensions in Section 2.1.1(a), Borrower may use up to Five Million
Dollars ($5,000,000.00) for the Bank's Cash Management Services, which may
include merchant services, direct deposit of payroll, business credit card, and
check cashing services identified in the various cash management services
agreements related to such services (the "Cash Management Services"). Such
aggregate amounts utilized under the Cash Management Services sublimit shall at
all times reduce the amount otherwise available for Credit Extensions under the
Committed Revolving Line. Any amounts Bank pays on behalf of Borrower or any
amounts that are not paid by Borrower for any Cash Management Services will be
treated as Advances under the Committed Revolving Line and will accrue interest
at the interest rate applicable to Advances. The balance of any Cash Management
Services payable to the Bank on the Revolving Maturity Date shall be paid in
full, or, if agreed to by Bank, secured by cash on terms acceptable to Bank at
all times on and after (i) the Revolving Maturity Date if the term of the
Committed Revolving Line is not extended by Bank, or (ii) the occurrence of an
Event of Default hereunder.

                                        2
<Page>

     2.1.3     EQUIPMENT ADVANCES.

               (a)  Through the date which is three hundred sixty-four (364)
days following the Closing Date (the "Equipment Availability End Date"), Bank
shall make advances ("Equipment Advance" and, collectively, "Equipment
Advances") to Borrower in an aggregate amount not exceeding the Committed
Equipment Line. To evidence the Equipment Advance or Equipment Advances,
Borrower shall deliver to Bank, at the time of each Equipment Advance request,
an invoice for the Eligible Equipment to be financed. Except as provided below,
the Equipment Advances may only be used to finance Eligible Equipment purchased
within ninety (90) days (determined based upon the applicable invoice date of
such Eligible Equipment) of each Equipment Advance request. Notwithstanding the
foregoing, the initial Equipment Advance may be used to finance Eligible
Equipment purchased on or after September 30, 2001 (determined based upon the
applicable invoice date of such Eligible Equipment). Equipment Advances shall
not exceed one hundred percent (100%) of the invoice amount of such Eligible
Equipment, excluding taxes, shipping, warranty charges, freight discounts and
installation expense relating to such Equipment. Expect as provided below, each
Equipment Advance under the Committed Equipment Line shall be made by Bank on
the first (1st) day of the month. Notwithstanding the foregoing, if Borrower
requests an Equipment Advance on a day other than the first (1st) day of the
month, such Equipment Advance shall be deemed to have occurred on and interest
shall be calculated beginning with the first day of such month. Each Equipment
Advance must be for a minimum amount of One Hundred Thousand Dollars
($100,000.00).

               (b)  Interest accrues from the date of each Equipment Advance at
the per annum rate described in Section 2.3(a), and shall be payable monthly on
the Payment Date of each month commencing with the initial Payment Date
following each such Equipment Advance. Each Equipment Advance shall be payable
in (i) thirty-six (36) equal monthly installments of principal, PLUS (ii)
monthly payments of accrued interest, beginning on the first Payment Date
following such Equipment Advance and continuing on each Payment Date thereafter
through the Equipment Maturity Date applicable to such Equipment Advance.
Borrower shall have the right to pre-pay Equipment Advances without penalty.
Equipment Advances when repaid may not be reborrowed.

               (c)  To obtain an Equipment Advance, Borrower must notify Bank
(the notice is irrevocable) by facsimile no later than 3:00 p.m. Eastern time
one (1) Business Day before the day on which the Equipment Advance is to be
made. The notice in the form of Exhibit B (Payment/Advance Form) must be signed
by a Responsible Officer or designee and include a copy of the invoice for the
Equipment being financed.

     2.1.4     UNDISBURSED CREDIT EXTENSIONS. The Bank's obligation to lend the
undisbursed portion of the Credit Extensions shall terminate if there has been a
Material Adverse Change, or there has been any material adverse deviation by
Borrower from the most recent business plan or budget of Borrower presented to
and accepted by Bank prior to the execution of this Agreement.

     2.2       OVERADVANCES. If Borrower's Tangible Net Worth at any time falls
below the TNW Threshold, then at all times thereafter Borrower must immediately
pay in cash to Bank the amount (if any) in which Borrower's aggregate
Obligations under Sections 2.1.1, 2.1.2, 2.1.3 and 2.1.4 exceed the Borrowing
Base.

     2.3       INTEREST RATE; PAYMENTS.

               (a)  INTEREST RATE. Advances under the Committed Revolving Line
shall accrue interest on the outstanding principal balance of the Committed
Revolving Line at a per annum rate described on the INTEREST RATE SUPPLEMENT TO
AGREEMENT attached hereto and incorporated by reference herein. Equipment
Advances under the Committed Equipment Line shall accrue interest on the
outstanding principal balance of the Committed Equipment Line at a per annum
rate equal to the Bank's Prime Rate. After an Event of Default, Obligations
shall bear interest at five percent (5.0%) above the rate effective immediately
before the Event of Default. The interest rate shall increase or decrease when
the Prime Rate changes. Interest is computed on the basis of a 360 day year for
the actual number of days elapsed.

               (b)  PAYMENTS. Interest is payable on all Credit Extensions under
this Agreement on the Payment Date of each month. Bank may debit any of
Borrower's deposit accounts including Account Number

                                        3
<Page>

____________________ for principal and interest payments or any amounts Borrower
owes Bank. Bank shall promptly notify Borrower when it debits Borrower's
accounts. These debits are not a set-off. Payments received after 12:00 noon
Eastern time are considered received at the opening of business on the next
Business Day; provided that this shall not apply if the Borrower had sufficient
cash in such account to make such payment in full at all times on the due date
therefore. When a payment is due on a day that is not a Business Day, the
payment is due the next Business Day and additional fees or interest, as
applicable, shall continue to accrue.

     2.4       FEES. Borrower shall pay to Bank:

               (a)  COMMITTED REVOLVING LINE FACILITY FEE. A fully earned,
non-refundable, one-time Committed Revolving Line facility fee of Fifty Thousand
Dollars ($50,000.00), due and payable on the Closing Date; and

               (b)  UNUSED COMMITTED EQUIPMENT LINE FACILITY FEE. As
compensation for the Bank's maintenance of sufficient funds available for such
purpose, the Bank shall have earned a facility fee on the Unused Committed
Equipment Line in an amount equal to one-half of one percent (0.50%) of the
Unused Committed Equipment Line on September 30, 2002, which Unused Committed
Equipment Line facility fee shall be due and payable by Borrower on September
30, 2002. If the Committed Equipment Line is terminated prior to September 30,
2002, the Unused Committed Equipment Line facility fee shall be equal to
one-half of one percent (0.50%) of the Unused Committed Equipment Line as of the
date of such termination, which fee shall be due and payable by Borrower on the
date of such termination. The Borrower shall not be entitled to any credit,
rebate or repayment of any facility fee previously earned by the Bank pursuant
to this Section notwithstanding any termination of the within Agreement, or
suspension or termination of the Bank's obligation to make loans and advances
hereunder; and

               (c)  LETTER OF CREDIT FEE. Except as provided below, Borrower
shall pay the Bank's customary fees and expenses for the issuance of Letters of
Credit, including, without limitation, a per annum fee for each Letter of Credit
equal to one percent (1.0%) of the face amount of each such Letter of Credit
issued, upon the issuance or renewal of such Letter of Credit by the Bank. The
Letter of Credit fees shall be due and fully earned upon Borrower's request for
each such Letter of Credit. Notwithstanding the foregoing, no Letter of Credit
fee shall be charged to the Borrower for the initial Five Hundred Fifty-Five
Thousand Dollars ($555,000.00) of Letters of Credit (the "Non-Fee Letters of
Credit") in the aggregate issued hereunder, nor shall any Letter of Credit fee
be charged to Borrower for any renewal of the Non-Fee Letters of Credit; and

               (d)  BANK EXPENSES. All Bank Expenses (including reasonable
attorneys' fees and expenses incurred through and after the Closing Date) when
due.

     2.5       ADDITIONAL COSTS. If any law or regulation increases Bank's costs
or reduces its income for any loan, Borrower shall pay the increase in cost or
reduction in income or additional expense PROVIDED, HOWEVER, that Borrower shall
not be liable for any amount attributable to any period before 180 days prior to
the date Bank notifies Borrower of such increased costs. Bank agrees that it
shall allocate any increased costs among its customers similarly affected in
good faith and in a manner consistent with Bank's customary practice.

     3         CONDITIONS OF LOANS

     3.1       CONDITIONS PRECEDENT TO INITIAL CREDIT EXTENSION. The obligation
of Bank to make the initial Credit Extension is subject to the condition
precedent that Bank shall have received, in form and substance satisfactory to
Bank, the following:

               (a)  this Agreement;

               (b)  Interest Rate Supplement to Agreement;

               (c)  Copy of Borrower's Certificate of Incorporation (certified
     by Secretary of State);

                                        4
<Page>

               (d)  a certificate of the Secretary of Borrower with respect to
     articles, bylaws, incumbency and resolutions authorizing the execution and
     delivery of this Agreement;

               (e)  Negative Pledge Agreement covering Intellectual Property;

               (f)  landlord's consent;

               (g)  a legal opinion of Borrower's counsel, in form and substance
     acceptable to Bank;

               (h)  financing statements (Forms UCC-1);

               (i)  Account Control Agreement/ Investment Account Control
     Agreement;

               (j)  Perfection Certificate;

               (k)  insurance certificate;

               (l)  results satisfactory to Bank in its sole discretion from the
     Initial Audit described in Section 6.2 prior to the initial Advance under
     the Committed Revolving Line;

               (m)  payment of the fees and Bank Expenses then due specified in
     Section 2.4 hereof;

               (n)  Certificate of Good Standing/Legal Existence (Long Form);

               (o)  Certificate of Foreign Qualification (if applicable); and

               (p)  such other documents, and completion of such other matters,
     as Bank may reasonably deem necessary or appropriate.

     3.2       CONDITIONS PRECEDENT TO ALL CREDIT EXTENSIONS. Bank's obligations
to make each Credit Extension, including the initial Credit Extension, is
subject to the following:

               (a)  timely receipt of any Payment/Advance Form; and

               (b)  the representations and warranties in Section 5 shall be
materially true on the date of the Payment/Advance Form and on the effective
date of each Credit Extension and no Event of Default shall have occurred and be
continuing as of such effective date, or result from the Credit Extension. Each
Credit Extension is Borrower's representation and warranty on that date that the
representations and warranties in Section 5 remain true.

     4         CREATION OF SECURITY INTEREST

     4.1       GRANT OF SECURITY INTEREST. Borrower hereby grants Bank, to
secure the payment and performance in full of all of the Obligations and the
performance of each of Borrower's duties under the Loan Documents, a continuing
security interest in, and pledges and assigns to the Bank, the Collateral,
wherever located, whether now owned or hereafter acquired or arising, and all
proceeds and products thereof. Borrower warrants and represents that the
security interest granted herein shall be a first priority security interest in
the Collateral. Upon and during the continuance of an Event of Default, Bank may
place a "hold" on any deposit account pledged as Collateral. Borrower agrees
that any disposition of the Collateral in violation of this Agreement, by either
the Borrower or any other Person, shall be deemed to violate the rights of the
Bank under the Code. If the Agreement is terminated, Bank's lien and security
interest in the Collateral shall continue until Borrower fully satisfies its
Obligations. If Borrower shall at any time, acquire a commercial tort claim,
Borrower shall promptly notify Bank in a writing signed by Borrower of the brief
details thereof and grant to Bank in such writing a security interest therein
and in the

                                        5
<Page>

proceeds thereof, all upon the terms of this Agreement, with such writing to
be in form and substance satisfactory to Bank.

     5         REPRESENTATIONS AND WARRANTIES

     Borrower represents and warrants as follows:

     5.1       DUE ORGANIZATION AND AUTHORIZATION. Borrower and each Subsidiary
is duly existing and in good standing in its state of formation and qualified
and licensed to do business in, and in good standing in, any state in which the
conduct of its business or its ownership of property requires that it be
qualified except where the failure to do so could not reasonably be expected to
cause a Material Adverse Change. In connection with this Agreement, the Borrower
delivered to the Bank a certificate signed by the Borrower and entitled
"Perfection Certificate". The Borrower represents and warrants to the Bank that:
(a) the Borrower's exact legal name is that indicated on the Perfection
Certificate and on the signature page hereof; and (b) the Borrower is an
organization of the type, and is organized in the jurisdiction, set forth in the
Perfection Certificate; and (c) the Perfection Certificate accurately sets forth
the Borrower's organizational identification number or accurately states that
the Borrower has none; and (d) the Perfection Certificate accurately sets forth
the Borrower's place of business, or, if more than one, its chief executive
office as well as the Borrower's mailing address if different, and (e) all other
information set forth on the Perfection Certificate pertaining to the Borrower
is accurate and complete. If the Borrower does not now have an organizational
identification number, but later obtains it, Borrower shall forthwith notify the
Bank or such organizational identification number.

     The execution, delivery and performance of the Loan Documents have been
duly authorized, and do not conflict with Borrower's organizational documents,
nor constitute an event of default under any material agreement by which
Borrower is bound. Borrower is not in default under any agreement to which or by
which it is bound in which the default could reasonably be expected to cause a
Material Adverse Change.

     5.2       COLLATERAL. Borrower has good title to the Collateral, free of
Liens except Permitted Liens. As of the Closing Date, Borrower has no other
deposit account, other than the deposit accounts with Bank and deposit accounts
described in the Perfection Certificate delivered to the Bank in connection
herewith. The Accounts are bona fide, existing obligations, and the service or
property has been performed or delivered to the account debtor or its agent for
immediate shipment to and unconditional acceptance by the account debtor. The
Collateral is not in the possession of any third party bailee (such as a
warehouse). In the event that Borrower, after the date hereof, intends to store
or otherwise deliver any portion of the Collateral to a bailee, then Borrower
will first receive the written consent of Bank and such bailee must acknowledge
in writing that the bailee is holding such Collateral for the benefit of Bank.
Borrower has no knowledge of any actual or imminent Insolvency Proceeding of any
account debtor whose accounts are an Eligible Account in any Borrowing Base
Certificate. All Inventory is in all material respects of good and marketable
quality, free from material defects.

     5.3       LITIGATION. Except as shown in the Schedule, there are no actions
or proceedings pending or, to the knowledge of Borrower's Responsible Officers,
threatened by or against Borrower or any Subsidiary in which an adverse decision
could reasonably be expected to cause a Material Adverse Change.

     5.4       NO MATERIAL DEVIATION IN FINANCIAL STATEMENTS. All consolidated
financial statements for Borrower and any Subsidiary delivered to Bank fairly
present in all material respects Borrower's consolidated financial condition and
Borrower's consolidated results of operations for the periods indicated. Such
monthly financial statements shall not include notes. There has not been any
material deterioration in Borrower's consolidated financial condition since the
date of the most recent financial statements submitted to Bank.

     5.5       SOLVENCY. Borrower is able to pay its debts (including trade
debts) as they mature.

     5.6       REGULATORY COMPLIANCE. Borrower is not an "investment company" or
a company "controlled" by an "investment company" under the Investment Company
Act. Borrower is not engaged as one of its important

                                        6
<Page>

activities in extending credit for margin stock (under Regulations T and U of
the Federal Reserve Board of Governors). Borrower has complied in all material
respects with the Federal Fair Labor Standards Act. Borrower has not violated
any laws, ordinances or rules, the violation of which could reasonably be
expected to cause a Material Adverse Change. None of Borrower's or any
Subsidiary's properties or assets has been used by Borrower or any Subsidiary
or, to the best of Borrower's knowledge, by previous Persons, in disposing,
producing, storing, treating, or transporting any hazardous substance other than
legally. Borrower and each Subsidiary has timely filed all required tax returns
and paid, or made adequate provision to pay, all material taxes, except those
being contested in good faith with adequate reserves under GAAP. Borrower and
each Subsidiary has obtained all consents, approvals and authorizations of, made
all declarations or filings with, and given all notices to, all government
authorities that are necessary to continue its business as currently conducted
except where the failure to make such declarations, notices or filings would not
reasonably be expected to cause a Material Adverse Change.

     5.7       SUBSIDIARIES. Borrower does not own any stock, partnership
interest or other equity securities except for Permitted Investments.

     5.8       FULL DISCLOSURE. No written representation, warranty or other
statement of Borrower in any certificate or written statement given to Bank
taken together with all such written certificates and written statements given
to Bank contains any untrue statement of a material fact or omits to state a
material fact necessary to make the statements contained in the certificates or
statements not misleading (it being recognized by Bank that the projections and
forecasts provided by Borrower in good faith and based upon reasonable
assumptions are not viewed as facts and that actual results during the period or
periods covered by such projections and forecasts may differ from the projected
or forecasted results).

     5.9       DESIGNATED SENIOR DEBT. All Obligations of the Borrower under or
arising in connection with this Agreement, as may be amended from time to time,
constitute "Designated Senior Debt" under and as defined in the 4.75%
Convertible Subordinated Note Due 2006 dated May 1, 2001 made by Borrower
payable to BellSouth Corporation issued pursuant to that certain Securities
Purchase Agreement dated as of May 1, 2001 between BellSouth Corporation and the
Borrower (hereinafter, said Note and Securities Purchase Agreement shall be
referred to as the "BellSouth Debt"). The Borrower hereby acknowledges, confirms
and agrees that the BellSouth Debt shall not be amended in any manner which
might adversely effect the Bank's interest as a holder of "Designated Senior
Debt", as such term is defined in the BellSouth Debt as of the Closing Date.

     6         AFFIRMATIVE COVENANTS

     Borrower shall do all of the following:

     6.1       GOVERNMENT COMPLIANCE. Except as permitted in Section 7.1 and
Section 7.3 with respect to Borrower's Subsidiaries, Borrower shall maintain its
and all Subsidiaries' legal existence and good standing in its jurisdiction of
formation and maintain qualification in each jurisdiction in which the failure
to so qualify would reasonably be expected to have a material adverse effect on
Borrower's business or operations. Borrower shall comply, and have each
Subsidiary comply, with all laws, ordinances and regulations to which it is
subject, noncompliance with which could have a material adverse effect on
Borrower's business or operations or be expected to cause a Material Adverse
Change.

     6.2       FINANCIAL STATEMENTS, REPORTS, CERTIFICATES.

               (a)  Borrower shall deliver to Bank: (i) as soon as available,
but no later than twenty-five (25) days after the last day of each month, a
company prepared unaudited consolidated balance sheet and unaudited income
statement covering Borrower's consolidated operations during the period
certified by a Responsible Officer and in a form acceptable to Bank and such
financial statements shall not include notes and shall be subject to year-end
and quarterly adjustments; (ii) on or before the earlier of: (A) forty-five (45)
days after the last day of each quarter or (B) five (5) days after filing with
the Securities and Exchange Commission, a copy of Borrower's Form 10-Q as filed
with the Securities and Exchange Commission; (iii) on or before the earlier of:
(A) one hundred twenty

                                        7
<Page>

(120) days after the last day of Borrower's fiscal year or (B) five (5) days
after filing with the Securities and Exchange Commission, a copy of Borrower's
Form 10-K as filed with the Securities and Exchange Commission, together with an
unqualified opinion on the financial statements from an independent certified
public accounting firm; (iv) within five (5) days of filing with the Securities
and Exchange Commission, a copy of Borrower's Form 8-K as filed with the
Securities and Exchange Commission; (v) as soon as available, but no later than
forty-five (45) days after the end of Borrower's fiscal year (and upon any
revisions to same which are approved by Borrower's Board of Directors), a
balance sheet, income statement and cash flow projections for the then current
fiscal year; (vi) within five (5) days of filing, copies of all statements,
reports and notices made available to Borrower's security holders or to any
holders of Subordinated Debt; (vii) a prompt report of any legal actions pending
or threatened against Borrower or any Subsidiary that could result in damages or
costs to Borrower or any Subsidiary of Five Hundred Thousand Dollars
($500,000.00) or more; and (viii) other financial information reasonably
requested by Bank.

               (b)  If Borrower's Tangible Net Worth as at the last day of a
month is below the TNW Threshold, Borrower shall deliver to Bank, within
twenty-five (25) days after the last day of each month thereafter in which
Advances were requested by Borrower or Obligations under the Committed Revolving
Line were outstanding, a Borrowing Base Certificate signed by a Responsible
Officer in the form of EXHIBIT C, with aged listings of accounts receivable.

               (c)  Within twenty-five (25) days after the last day of each
month, Borrower shall deliver to Bank with the monthly financial statements a
Compliance Certificate signed by a Responsible Officer in the form of EXHIBIT D.

               (d)  Allow Bank to audit Borrower's Collateral at Borrower's
expense. Such audits shall be conducted no more often than once every twelve
(12) months unless an Event of Default has occurred and is continuing. The
Borrower shall provide the Bank with access to all its records and financial
information so that the first such audit (the "Initial Audit") of Borrower's
Accounts shall be completed by Bank prior to the initial Advance under the
Committed Revolving Line.

     6.3       INVENTORY; RETURNS. Borrower shall keep all Inventory in good and
marketable condition, free from material defects. Returns and allowances between
Borrower and its account debtors shall follow Borrower's customary practices as
they exist at the Closing Date. Borrower must promptly notify Bank of all
returns, recoveries, disputes and claims that involve more than Two Hundred
Fifty Thousand Dollars ($250,000.00). The obligations under this Section 6.3
shall not apply to Inventory which is supplied to Borrower's customers for trial
or evaluation purposes.

     6.4       TAXES. Borrower shall make, and cause each Subsidiary to make,
timely payment of all material federal, state, and local taxes or assessments
(other than taxes and assessments which Borrower is contesting in good faith,
with adequate reserves maintained in accordance with GAAP) and will deliver to
Bank, on demand, appropriate certificates attesting to such payments.

     6.5       INSURANCE. Borrower shall keep its business and the Collateral
insured for risks and in amounts, standard for Borrower's industry. Insurance
policies shall be in a form, with companies, and in amounts that are reasonably
satisfactory to Bank. All property policies shall have a lender's loss payable
endorsement showing Bank as an additional loss payee and all liability policies
shall show the Bank as an additional insured and all policies shall provide that
the insurer must give Bank at least twenty (20) days notice before canceling its
policy. At Bank's request, Borrower shall deliver certified copies of policies
and evidence of all premium payments. Proceeds payable under any policy shall,
at Bank's option, be payable to Bank on account of the Obligations.
Notwithstanding the foregoing, so long as no Event of Default has occurred and
is continuing, Borrower shall have the option of applying the proceeds of any
casualty policy up to $25,000.00, in the aggregate, toward the replacement or
repair of destroyed or damaged property; provided that (i) any such replaced or
repaired property (a) shall be of equal or like value as the replaced or
repaired Collateral and (b) shall be deemed Collateral in which Bank has been
granted a first priority security interest and (ii) after the occurrence and
during the continuation of an Event of Default all proceeds

                                        8
<Page>

payable under such casualty policy shall, at the option of the Bank, be payable
to Bank on account of the Obligations. If Borrower fails to obtain insurance as
required under this Section or to pay any amount or furnish any required proof
of payment to third persons and the Bank, Bank may make all or part of such
payment or obtain such insurance policies required in this Section, and take any
action under the policies Bank deems prudent.

     6.6       PRIMARY ACCOUNTS. In order to permit the Bank to monitor the
Borrower's financial performance and condition, Borrower shall maintain its
primary operating accounts with Bank. In addition to the foregoing: (i) on the
Closing Date, Borrower shall maintain or have administered through the Bank not
less than Thirty-Five Million Dollars ($35,000,000.00) in cash or securities,
and (ii) at all times after the Closing Date and prior to the termination of
this Agreement, Borrower shall maintain or have administered through the Bank
not less than Twenty-Five Million Dollars ($25,000,000.00) in cash or securities
in excess of that amount used for Borrower's operations. Borrower shall identify
to Bank, in writing, of any bank or securities account opened by Borrower with
any institution other than Bank. In addition, for each such account that the
Borrower at any time opens or maintains, Borrower shall, at the Bank's request
and option, pursuant to an agreement in form and substance acceptable to the
Bank, cause the depository bank or securities intermediary to agree that such
account is the collateral of the Bank pursuant to the terms hereunder. The
provisions of this paragraph shall not apply to deposit accounts exclusively
used for payroll, payroll taxes and other employee wage and benefit payments to
or for the benefit of the Borrower's employees.

     6.7       FINANCIAL COVENANTS. Borrower shall maintain at all times, to be
tested as of the last day of each month, unless otherwise noted:

               (a)  QUICK RATIO. Borrower shall maintain a ratio of Quick Assets
     to Current Liabilities (less Deferred Maintenance Revenue), as of the last
     day of each month, of at least 1.5 to 1.0.

               (b)  TANGIBLE NET WORTH. Borrower shall maintain, as of the last
     day of each month, a Tangible Net Worth of at least: (i) Seventy Million
     Dollars ($70,000,000.00) for each month through the month ending March 31,
     2002, (ii) Sixty Million Dollars ($60,000,000.00) for each month from April
     30, 2002 through the month ending September 30, 2002, and (iii) Fifty
     Million Dollars ($50,000,000.00) for each month after September 30, 2002;
     PROVIDED THAT each of the threshold amounts listed in (i)-(iii) above shall
     be increased by fifty percent (50%) of the amount of the proceeds received
     by Borrower from equity issued by Borrower after the Closing Date.

     6.8       FURTHER ASSURANCES. Borrower shall execute any further
instruments and take further action as Bank reasonably requests to perfect or
continue Bank's security interest in the Collateral or to effect the purposes of
this Agreement.

     7         NEGATIVE COVENANTS

     Borrower shall not do any of the following without the Bank's prior written
consent which shall not be unreasonably withheld:

     7.1       DISPOSITIONS. Convey, sell, lease, transfer or otherwise dispose
of (collectively a "Transfer"), or permit any of its Subsidiaries to Transfer,
all or any part of its business or property, except for Transfers (i) of
Inventory in the ordinary course of business; (ii) of non-exclusive licenses and
similar arrangements for the use of the property of Borrower or its Subsidiaries
in the ordinary course of business; (iii) of worn-out or obsolete Equipment;
(iv) the discontinued products identified on the Schedule; and (v) furniture or
equipment owned by telecom technologies, inc. and other fixed assets to be
transferred to its landlord pursuant to a real property lease agreement; and
(vi) of assets from a Subsidiary of the Borrower to the Borrower or another
Subsidiary of the Borrower.

     7.2       CHANGES IN BUSINESS, OWNERSHIP, MANAGEMENT OR BUSINESS LOCATIONS.
Engage in or permit any of its Subsidiaries to engage in any business other than
the businesses currently engaged in by Borrower, or have a

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material change in management. Borrower shall not, without providing Bank with
written notice within fifteen (15) days thereafter: (i) relocate its chief
executive office, or add any new offices or business locations (unless such new
offices or business locations contain less than Fifty Thousand Dollars
($50,000.00) in Borrower's assets or property), or (ii) change its jurisdiction
of organization, or (iii) change its organizational structure or type, or (iv)
change its legal name, or (v) change any organizational number (if any) assigned
by its jurisdiction of organization.

     7.3       MERGERS OR ACQUISITIONS. Merge or consolidate, or permit any of
its Subsidiaries to merge or consolidate, with any other Person, or acquire, or
permit any of its Subsidiaries to acquire, all or substantially all of the
capital stock or property of another Person other than: (i) mergers of: (A)
Borrower's Subsidiaries with other of Borrower's Subsidiaries, or (B) Borrower's
Subsidiaries with and into the Borrower (provided that Borrower is the surviving
legal entity), and (ii) the dissolution of Borrower's Subsidiaries by Borrower.

     7.4       INDEBTEDNESS. Create, incur, assume, or be liable for any
Indebtedness, or permit any Subsidiary to do so, other than Permitted
Indebtedness.

     7.5       ENCUMBRANCE. Create, incur, or allow any Lien on any of its
property, or assign or convey any right to receive income, including the sale of
any Accounts, or permit any of its Subsidiaries to do so, except for Permitted
Liens, or permit any Collateral not to be subject to the first priority security
interest granted herein. The Collateral may also be subject to Permitted Liens.

     7.6       DISTRIBUTIONS; INVESTMENTS. (i) Directly or indirectly acquire or
own any Person, or make any Investment in any Person, other than Permitted
Investments, or permit any of its Subsidiaries to do so; or (ii) pay any cash
dividends or make any distribution (other than non-cash dividends) or payment or
redeem, retire or purchase any capital stock except for: (A) the repurchase by
Borrower of restricted stock owned by Borrower's terminated employees, and (B)
the purchase by Borrower of Borrower's common stock purchased in the open
market, except that the amount of Borrower's repurchases or purchases, as
applicable, of stock in (A) and (B) above shall not be greater than
$3,000,000.00 in the aggregate.

     7.7       TRANSACTIONS WITH AFFILIATES. Directly or indirectly enter or
permit any material transaction with any Affiliate, except transactions that are
in the ordinary course of Borrower's business, upon fair and reasonable terms
that are no less favorable to Borrower than would be obtained in an arm's length
transaction with a non-affiliated Person.

     7.8       SUBORDINATED DEBT. Make or permit any payment on any Subordinated
Debt, except under the terms of the Subordinated Debt, or amend any provision in
any document relating to the Subordinated Debt, without Bank's prior written
consent.

     7.9       COMPLIANCE. Become an "investment company" or a company
controlled by an "investment company", under the Investment Company Act of 1940
or undertake as one of its important activities extending credit to purchase or
carry margin stock, or use the proceeds of any Credit Extension for that
purpose; fail to meet the minimum funding requirements of ERISA, permit a
Reportable Event or Prohibited Transaction, as defined in ERISA, to occur; fail
to comply with the Federal Fair Labor Standards Act or violate any other law or
regulation, if the violation could reasonably be expected to have a material
adverse effect on Borrower's business or operations or would reasonably be
expected to cause a Material Adverse Change, or permit any of its Subsidiaries
to do so.

     8         EVENTS OF DEFAULT

     Any one of the following is an Event of Default:

     8.1       PAYMENT DEFAULT. Borrower fails to pay any of the Obligations
within three (3) Business Days after their due date. During the additional
period the failure to cure the default is not an Event of Default (but no Credit
Extension shall be made during the cure period);

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     8.2       COVENANT DEFAULT. Borrower does not perform any obligation in
Section 6 or violates any covenant in Section 7 or does not perform or observe
any other material term, condition or covenant in this Agreement, any Loan
Documents, or in any agreement between Borrower and Bank and as to any default
under a term, condition or covenant that can be cured, has not cured the default
within twenty (20) days after it occurs, or if the default cannot be cured
within such twenty (20) days or cannot be cured after Borrower's attempts in the
twenty (20) day period, and the default may be cured within a reasonable time,
then Borrower shall have additional time, (of not more than twenty (20) days) to
attempt to cure the default. Grace periods provided under this section shall not
apply, among other things, to financial covenants or any other covenants that
are required to be satisfied, completed or tested by a date certain. During the
additional period the failure to cure the default is not an Event of Default
(but no Credit Extensions shall be made during the cure period);

     8.3       MATERIAL ADVERSE CHANGE. A Material Adverse Change occurs;

     8.4       ATTACHMENT. (i) Any material portion of Borrower's assets is
attached, seized, levied on, or comes into possession of a trustee or receiver
and the attachment, seizure or levy is not removed in ten (10) days; (ii) the
service of process upon the Borrower seeking to attach, by trustee or similar
process any funds of the Borrower on deposit with the Bank; (iii) Borrower is
enjoined, restrained, or prevented by court order from conducting a material
part of its business; (iv) a judgment or other claim becomes a Lien on a
material portion of Borrower's assets; or (v) a notice of lien, levy, or
assessment is filed against any of Borrower's assets by any government agency
and not paid within ten (10) days after Borrower receives notice. These are not
Events of Default if stayed or if a bond is posted pending contest by Borrower
(but no Credit Extensions shall be made during the cure period);

     8.5       INSOLVENCY. (i) Borrower becomes insolvent; (ii) Borrower begins
an Insolvency Proceeding; or (iii) an Insolvency Proceeding is begun against
Borrower and not dismissed or stayed within forty-five (45) days (but no Credit
Extensions shall be made before any Insolvency Proceeding is dismissed);

     8.6       OTHER AGREEMENTS. If there is a default in any agreement to which
Borrower is a party with a third party or parties resulting in a right by such
third party or parties, whether or not exercised, to accelerate the maturity of
any Indebtedness in an amount in excess of Five Hundred Thousand Dollars
($500,000) or that could result in a Material Adverse Change;

     8.7       JUDGMENTS. Except with respect to a judgment specified on
SCHEDULE 8.7 with regard to Borrower's wholly-owned Subsidiary, telecom
technologies, inc., if a judgment or judgments for the payment of money in an
amount, individually or in the aggregate, of at least Five Hundred Thousand
Dollars ($500,000) shall be rendered against Borrower and shall remain
unsatisfied and unstayed for a period of ten (10) days (provided that no Credit
Extensions will be made prior to the satisfaction or stay of such judgment);

     8.8       MISREPRESENTATIONS. If Borrower or any Person acting for Borrower
makes any material misrepresentation or material misstatement now or later in
any warranty or representation in this Agreement or in any writing delivered to
Bank or to induce Bank to enter this Agreement or any Loan Document.

     9         BANK'S RIGHTS AND REMEDIES

     9.1       RIGHTS AND REMEDIES. When an Event of Default occurs and
continues Bank may, without notice or demand, do any or all of the following:

               (a)  Declare all Obligations immediately due and payable (but if
     an Event of Default described in Section 8.5 occurs all Obligations are
     immediately due and payable without any action by Bank);

               (b)  Stop advancing money or extending credit for Borrower's
     benefit under this Agreement or under any other agreement between Borrower
     and Bank;

                                       11
<Page>

               (c)  Settle or adjust disputes and claims directly with account
     debtors for amounts, on terms and in any order that Bank considers
     advisable;

               (d)  Make any payments and do any acts it considers necessary or
     reasonable to protect its security interest in the Collateral. Borrower
     shall assemble the Collateral if Bank requests and make it available as
     Bank designates. Bank may enter premises where the Collateral is located
     (to extent not prohibited by applicable law and as to Collateral in the
     possession of customers of Borrower, only after thirty (30) days prior
     written notice to Borrower), take and maintain possession of any part of
     the Collateral, and pay, purchase, contest, or compromise any Lien which
     appears to be prior or superior to its security interest and pay all
     expenses incurred. Borrower grants Bank a license to enter and occupy any
     of its premises, without charge, to exercise any of Bank's rights or
     remedies;

               (e)  Apply to the Obligations any (i) balances and deposits of
     Borrower it holds, or (ii) any amount held by Bank owing to or for the
     credit or the account of Borrower;

               (f)  Ship, reclaim, recover, store, finish, maintain, repair,
     prepare for sale, advertise for sale, and sell the Collateral. Bank is
     granted a non-exclusive, royalty-free license or other right to use,
     without charge, Borrower's labels, patents, copyrights, mask works, rights
     of use of any name, trade secrets, trade names, trademarks, service marks,
     and advertising matter, or any similar property as it pertains to the
     Collateral, in completing production of, advertising for sale, and selling
     any Collateral and, in connection with Bank's exercise of its rights under
     this Section, Borrower's rights under all licenses and all franchise
     agreements inure to Bank's benefit for the purposes described herein and to
     the extent not prohibited by the terms of any licenses or franchise
     agreements in effect on the date hereof and under which the Borrower is the
     licensee or franchisee, only to the extent such prohibitions are
     enforceable; and

               (g)  Dispose of the Collateral according to the Code.

     9.2       POWER OF ATTORNEY. Borrower hereby irrevocably appoints Bank as
its lawful attorney-in-fact, to be effective upon the occurrence and during the
continuance of an Event of Default, to: (i) endorse Borrower's name on any
checks or other forms of payment or security; (ii) sign Borrower's name on any
invoice or bill of lading for any Account or drafts against account debtors;
(iii) settle and adjust disputes and claims about the Accounts directly with
account debtors, for amounts and on terms Bank determines reasonable; (iv) make,
settle, and adjust all claims under Borrower's insurance policies; and (v)
transfer the Collateral into the name of Bank or a third party as the Code
permits. Borrower hereby appoints Bank as its lawful attorney-in-fact to sign
Borrower's name on any documents necessary to perfect or continue the perfection
of any security interest regardless of whether an Event of Default has occurred
until all Obligations have been satisfied in full and Bank is under no further
obligation to make Credit Extensions hereunder. Bank's foregoing appointment as
Borrower's attorney in fact, and all of Bank's rights and powers, coupled with
an interest, are irrevocable until all Obligations have been fully repaid and
performed and Bank's obligation to provide Credit Extensions terminates.

     9.3       ACCOUNTS COLLECTION. In the event that an Event of Default occurs
and is continuing, Bank may notify any Person owing Borrower money of Bank's
security interest in the funds and verify and/or collect the amount of the
Account. After the occurrence of an Event of Default, any amounts received by
Borrower shall be held in trust by Borrower for Bank, and, if requested by Bank,
Borrower shall immediately deliver such receipts to Bank in the form received
from the account debtor, with proper endorsements for deposit.

     9.4       BANK EXPENSES. Any amounts paid by Bank as provided herein are
Bank Expenses and are immediately due and payable, and shall bear interest at
the then applicable rate and be secured by the Collateral. No payments by Bank
shall be deemed an agreement to make similar payments in the future or Bank's
waiver of any Event of Default.

     9.5       BANK'S LIABILITY FOR COLLATERAL. So long as the Bank complies
with reasonable banking practices regarding the safekeeping of collateral, the
Bank shall not be liable or responsible for: (a) the safekeeping of the

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Collateral; (b) any loss or damage to the Collateral; (c) any diminution in the
value of the Collateral; or (d) any act or default of any carrier, warehouseman,
bailee, or other person. Borrower bears all risk of loss, damage or destruction
of the Collateral.

     9.6       REMEDIES CUMULATIVE. Bank's rights and remedies under this
Agreement, the Loan Documents, and all other agreements are cumulative. Bank has
all rights and remedies provided under the Code, by law, or in equity. Bank's
exercise of one right or remedy is not an election, and Bank's waiver of any
Event of Default is not a continuing waiver. Bank's delay is not a waiver,
election, or acquiescence. No waiver hereunder shall be effective unless signed
by Bank and then is only effective for the specific instance and purpose for
which it was given.

     9.7       DEMAND WAIVER. Borrower waives demand, notice of default or
dishonor, notice of payment and nonpayment, notice of any default, nonpayment at
maturity, release, compromise, settlement, extension, or renewal of accounts,
documents, instruments, chattel paper, and guarantees held by Bank on which
Borrower is liable.

     10        NOTICES

     All notices or demands by any party to this Agreement or any other related
agreement must be in writing and be personally delivered or sent by an overnight
delivery service, by certified mail, postage prepaid, return receipt requested,
or by telefacsimile at the addresses listed below. Either Bank or Borrower may
change its notice address by giving the other written notice.

                  If to Borrower:   Sonus Networks, Inc.
                                    5 Carlisle Road
                                    Westford, Massachusetts 01886
                                    Attn: Mr. Stephen J. Nill, CFO
                                    Fax: 978-692-9118

                  with a copy to:   Bingham Dana LLP
                                    150 Federal Street
                                    Boston, Massachusetts 02110
                                    Attn: Johan V. Brigham, Esquire
                                    Fax: 617-951-8736

                  If to Bank:       Silicon Valley Bank
                                    One Newton Executive Park, Suite 200
                                    2221 Washington Street
                                    Newton, Massachusetts  02462
                                    Attn: Ms. Pamela Braren
                                    Fax:  (617) 969-4395

                  with a copy to:   Riemer & Braunstein LLP
                                    Three Center Plaza
                                    Boston, Massachusetts 02108
                                    Attn: David A. Ephraim, Esquire
                                    FAX: (617) 880-3456

     11        CHOICE OF LAW, VENUE AND JURY TRIAL WAIVER

     Massachusetts law governs the Loan Documents without regard to principles
of conflicts of law. Borrower and Bank each submit to the exclusive jurisdiction
of the State and Federal courts in Massachusetts; provided, however, that if for
any reason Bank cannot avail itself of such courts in the Commonwealth of
Massachusetts, Borrower accepts jurisdiction of the courts and venue in Santa
Clara County, California. NOTWITHSTANDING THE FOREGOING, THE BANK SHALL HAVE THE
RIGHT TO BRING ANY ACTION OR PROCEEDING

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AGAINST THE BORROWER OR ITS PROPERTY IN THE COURTS OF ANY OTHER JURISDICTION
WHICH THE BANK DEEMS NECESSARY OR APPROPRIATE IN ORDER TO REALIZE ON THE
COLLATERAL OR TO OTHERWISE ENFORCE THE BANK'S RIGHTS AGAINST THE BORROWER OR ITS
PROPERTY.

BORROWER AND BANK EACH WAIVE THEIR RIGHT TO A JURY TRIAL OF ANY CLAIM OR CAUSE
OF ACTION ARISING OUT OF OR BASED UPON THIS AGREEMENT, THE LOAN DOCUMENTS OR ANY
CONTEMPLATED TRANSACTION, INCLUDING CONTRACT, TORT, BREACH OF DUTY AND ALL OTHER
CLAIMS. THIS WAIVER IS A MATERIAL INDUCEMENT FOR BOTH PARTIES TO ENTER INTO THIS
AGREEMENT. EACH PARTY HAS REVIEWED THIS WAIVER WITH ITS COUNSEL.

     12        GENERAL PROVISIONS

     12.1      SUCCESSORS AND ASSIGNS. This Agreement binds and is for the
benefit of the successors and permitted assigns of each party. Borrower may not
assign this Agreement or any rights or Obligations under it without Bank's prior
written consent which may be granted or withheld in Bank's discretion. Bank has
the right, without the consent of or notice to Borrower, to sell, transfer,
negotiate, or grant participation in all or any part of, or any interest in,
Bank's obligations, rights and benefits under this Agreement, the Loan Documents
or any related agreement.

     12.2      INDEMNIFICATION. Borrower hereby indemnifies, defends and holds
the Bank and its officers, employees and agents harmless against: (a) all
obligations, demands, claims, and liabilities asserted by any other party in
connection with the transactions contemplated by the Loan Documents; and (b) all
losses or Bank Expenses incurred, or paid by Bank from, following, or
consequential to transactions between Bank and Borrower (including reasonable
attorneys' fees and expenses), except for losses caused by Bank's gross
negligence or willful misconduct.

     12.3      RIGHT OF SET-OFF. Borrower and any guarantor hereby grant to
Bank, a lien, security interest and right of setoff as security for all
Obligations to Bank, whether now existing or hereafter arising upon and against
all deposits, credits, collateral and property, now or hereafter in the
possession, custody, safekeeping or control of Bank or any entity under the
control of the Bank or in transit to any of them. At any time after the
occurrence and during the continuance of an Event of Default, without demand or
notice, Bank may set off the same or any part thereof and apply the same to any
liability or obligation of Borrower and any guarantor even though unmatured and
regardless of the adequacy of any other collateral securing the Obligations. ANY
AND ALL RIGHTS TO REQUIRE BANK TO EXERCISE ITS RIGHTS OR REMEDIES WITH RESPECT
TO ANY OTHER COLLATERAL WHICH SECURES THE OBLIGATIONS, PRIOR TO EXERCISING ITS
RIGHT OF SETOFF WITH RESPECT TO SUCH DEPOSITS, CREDITS OR OTHER PROPERTY OF THE
BORROWER OR ANY GUARANTOR, ARE HEREBY KNOWINGLY, VOLUNTARILY AND IRREVOCABLY
WAIVED.

     12.4      TIME OF ESSENCE. Time is of the essence for the performance of
all Obligations in this Agreement.

     12.5      SEVERABILITY OF PROVISION. Each provision of this Agreement is
severable from every other provision in determining the enforceability of any
provision.

     12.6      AMENDMENTS IN WRITING; INTEGRATION. All amendments to this
Agreement must be in writing signed by both Bank and Borrower. This Agreement
and the Loan Documents represent the entire agreement about this subject matter,
and supersede prior negotiations or agreements. All prior agreements,
understandings, representations, warranties, and negotiations between the
parties about the subject matter of this Agreement and the Loan Documents merge
into this Agreement and the Loan Documents.

     12.7      COUNTERPARTS. This Agreement may be executed in any number of
counterparts and by different parties on separate counterparts, each of which,
when executed and delivered, are an original, and all taken together, constitute
one Agreement.

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<Page>

     12.8      SURVIVAL. All covenants, representations and warranties made in
this Agreement continue in full force while any Obligations remain outstanding.
The obligation of Borrower in Section 12.2 to indemnify Bank shall survive until
the statute of limitations with respect to such claim or cause of action shall
have run.

     12.9      CONFIDENTIALITY. In handling any Confidential Information, Bank
shall exercise the same degree of care that it exercises for its own proprietary
information, but disclosure of information may be made: (i) to Bank's
subsidiaries or affiliates in connection with their business with Borrower; (ii)
to prospective transferees or purchasers of any interest in the Credit
Extensions (provided, however, Bank shall use commercially reasonable efforts in
obtaining such prospective transferee's or purchaser's agreement to the terms of
this provision); (iii) as required by law, regulation, subpoena, or other order,
(iv) as required in connection with Bank's examination or audit; and (v) upon
the occurrence and continuance of an Event of Default, as Bank considers
appropriate in exercising remedies under this Agreement. The restrictions set
forth above shall not apply to information that (a) is generally known within
the industry at the time of its disclosure; (b) is lawfully received by the Bank
from a third party (unless the Bank is aware that such third party is not
permitted to make such disclosures due to a confidential relationship with the
Borrower); (c) was already in the Bank's possession at the time such information
was disclosed by the Borrower to the Bank; or (d) was independently developed by
the Bank without use of the information disclosed under this Agreement. If a
portion or aspect of the Confidential Information becomes generally known
through no action of the Bank, only that portion or aspect shall not be governed
by this Agreement and all other aspects of the Confidential Information shall
remain subject to the provisions of this Agreement.

     13        DEFINITIONS

     13.1      DEFINITIONS.

     "ACCOUNTS" are all existing and later arising accounts, contract rights,
and other obligations owed Borrower in connection with its sale or lease of
goods (including licensing software and other technology) or provision of
services, all credit insurance, guaranties, other security and all merchandise
returned or reclaimed by Borrower and Borrower's Books relating to any of the
foregoing, as such definition may be amended from time to time according to the
Code.

     "ADVANCE" or "ADVANCES" is a loan advance (or advances) under the Committed
Revolving Line, including, without limitation, the Prime Rate Loans and the
LIBOR Rate Loans described in the Interest Rate Supplement.

     "AFFILIATE" of a Person is a Person that owns or controls directly or
indirectly the Person, any Person that controls or is controlled by or is under
common control with the Person, and each of that Person's senior executive
officers, directors, partners and, for any Person that is a limited liability
company, that Person's managers and members.

     "BANK EXPENSES" are all audit fees and expenses and reasonable costs or
expenses (including reasonable attorneys' fees and expenses) for preparing,
negotiating, administering, defending and enforcing the Loan Documents
(including appeals or Insolvency Proceedings).

     "BELLSOUTH DEBT" is defined in Section 5.9.

     "BORROWER'S BOOKS" are all Borrower's books and records including ledgers,
records regarding Borrower's assets or liabilities, the Collateral, business
operations or financial condition and all computer programs or discs or any
equipment containing the information.

     "BORROWING BASE" is eighty percent (80%) of Eligible Accounts, as
determined by Bank from Borrower's most recent Borrowing Base Certificate;
provided, however, that Bank may lower the percentage of the Borrowing Base
after performing an audit of Borrower's Collateral, which reduction of the
Borrowing Base shall be effective ten (10) days after Bank provides notice to
Borrower of such change.

                                       15
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     "BUSINESS DAY" is any day that is not a Saturday, Sunday or a day on which
the Bank is closed.

     "CASH MANAGEMENT SERVICES" are defined in Section 2.1.4.

     "CLOSING DATE" is March 25, 2002.

     "CODE" is the Uniform Commercial Code as adopted in Massachusetts, as
amended and as may be amended and in effect from time to time.

     "COLLATERAL" is any and all properties, rights and assets of the Borrower
(other than Intellectual Property, except to the extent that a security interest
in Borrower's Intellectual Property is granted by Borrower to Bank hereafter)
granted by the Borrower to Bank or arising under the Code, now, or in the
future, in which the Borrower obtains an interest, or the power to transfer
rights, including, without limitation, the property described on EXHIBIT A.

     "COMMITTED EQUIPMENT LINE" is an Equipment Advance or Equipment Advances of
up to Ten Million Dollars ($10,000,000.00).

     "COMMITTED REVOLVING LINE" is an Advance or Advances of up to Twenty
Million Dollars ($20,000,000.00). Notwithstanding the foregoing, the
availability of the initial Advance under the Committed Revolving Line shall be
subject to the receipt by the Bank of satisfactory results, in the sole and
absolute discretion of the Bank, of the Initial Audit of Borrower's Accounts
pursuant to Section 6.2 hereof. If the results of the Initial Audit are not
satisfactory to the Bank for any reason, the Bank may, at its discretion, reduce
the amount of the Committed Revolving Line, or not make any Advances thereunder,
except pursuant to terms satisfactory to Bank.

     "CONFIDENTIAL INFORMATION" means all commercially valuable, propriety and
confidential information and trade secrets with respect to the Borrower's
business and products, whether of a technical, business or other nature
(including, without limitation, know-how and information relating to the
technology, customers, business plans, promotional and marketing activities,
finances and other business affairs of the Borrower), that is disclosed to the
Bank or any of its officers, employees or agents or is otherwise learned by the
Bank or any of its officers, employees or agents in the course of discussions or
business dealings with, or physical or electronic access to the premises of, the
Borrower, and that has been identified as being proprietary and/or confidential
or that by the nature of the circumstances surrounding the disclosure or receipt
ought to be treated as proprietary and confidential.

     "CONTINGENT OBLIGATION" is, for any Person, any direct or indirect
liability, contingent or not, of that Person for (i) any indebtedness, lease,
dividend, letter of credit or other obligation of another such as an obligation
directly or indirectly guaranteed, endorsed, co-made, discounted or sold with
recourse by that Person, or for which that Person is directly or indirectly
liable; (ii) any obligations for undrawn letters of credit for the account of
that Person; and (iii) all obligations from any interest rate, currency or
commodity swap agreement, interest rate cap or collar agreement, or other
agreement or arrangement designated to protect a Person against fluctuation in
interest rates, currency exchange rates or commodity prices; but "Contingent
Obligation" does not include endorsements in the ordinary course of business.
The amount of a Contingent Obligation is the stated or determined amount of the
primary obligation for which the Contingent Obligation is made or, if not
determinable, the maximum reasonably anticipated liability for it determined by
the Person in good faith; but the amount may not exceed the maximum of the
obligations under the guarantee or other support arrangement.

     "CREDIT EXTENSION" is each Advance (including Cash Management Services),
Equipment Advance, Letter of Credit, FX Forward Contract or any other extension
of credit by Bank for Borrower's benefit.

     "CURRENT LIABILITIES" are the aggregate amount of Borrower's Total
Liabilities which mature within one (1) year, PLUS, without duplication, all
obligations and liabilities of Borrower to Bank.

                                       16
<Page>

     "DEFERRED MAINTENANCE REVENUE" is all amounts received in advance of
performance under maintenance contracts and not yet recognized as revenue.

     "ELIGIBLE ACCOUNTS" are billed Accounts in the ordinary course of
Borrower's business that meet all Borrower's representations and warranties in
Section 5.2; BUT Bank may in its reasonable discretion change eligibility
standards by giving Borrower thirty (30) days prior written notice. Unless Bank
agrees otherwise in writing, Eligible Accounts shall not include:

               (a)  Accounts that the account debtor has not paid within ninety
     (90) days of invoice date;

               (b)  Accounts for an account debtor, fifty percent (50%) or more
     of whose Accounts have not been paid within ninety (90) days of invoice
     date;

               (c)  Credit balances over ninety (90) days from invoice date;

               (d)  Accounts for an account debtor, including Affiliates, whose
     total obligations to Borrower exceed twenty-five percent (25%) of all
     Accounts, for the amounts that exceed that percentage, unless Bank approves
     in writing;

               (e)  Accounts for which the account debtor does not have its
     principal place of business in the United States, except for certain
     foreign accounts receivable which may be approved by Bank in its sole
     discretion on a case-by-case basis;

               (f)  Accounts for which the account debtor is a federal, state or
     local government entity or any department, agency, or instrumentality
     thereof;

               (g)  Accounts for which Borrower owes the account debtor, but
     only up to the amount owed (sometimes called "contra" accounts, accounts
     payable, customer deposits or credit accounts);

               (h)  Accounts for demonstration or promotional equipment, or in
     which goods are consigned, sales guaranteed, sale or return, sale on
     approval, bill and hold, or other terms if account debtor's payment may be
     conditional;

               (i)  Accounts for which the account debtor is Borrower's
     Affiliate, officer, employee, or agent;

               (j)  Accounts in which the account debtor disputes liability or
     makes any claim and Bank believes there may be a basis for dispute (but
     only up to the disputed or claimed amount), or if the Account Debtor is
     subject to an Insolvency Proceeding, or becomes insolvent, or goes out of
     business;

               (k)  Accounts for which Bank reasonably determines collection to
     be doubtful.

     "ELIGIBLE EQUIPMENT" is (a) general purpose computer equipment, office
equipment, test, manufacturing and laboratory equipment, furnishings, subject to
the limitations set forth herein, and (b) Other Equipment that complies with all
of Borrower's representations and warranties to Bank and which is reasonably
acceptable to Bank in all respects.

     "EQUIPMENT" is all present and future machinery, equipment, tenant
improvements, furniture, fixtures, vehicles, tools, parts and attachments in
which Borrower has any interest.

     "EQUIPMENT ADVANCE " is defined in Section 2.1.5.
     "EQUIPMENT AVAILABILITY END DATE" is defined in Section 2.1.5.

                                       17
<Page>

     "EQUIPMENT MATURITY DATE" is, with respect to each Equipment Advance, the
thirty-sixth (36th) Payment Date following each such Equipment Advance.

     "ERISA" is the Employment Retirement Income Security Act of 1974, and its
regulations.

     "FX FORWARD CONTRACT" is defined in Section 2.1.3.

     "FX RESERVE" is defined in Section 2.1.3.

     "GAAP" is generally accepted accounting principles.

     "GUARANTOR" is any present or future guarantor of the Obligations.

     "INDEBTEDNESS" is (a) indebtedness for borrowed money or the deferred price
of property or services, such as reimbursement and other obligations for surety
bonds and letters of credit, (b) obligations evidenced by notes, bonds,
debentures or similar instruments, (c) capital lease obligations and (d)
Contingent Obligations.

     "INSOLVENCY PROCEEDING" is any proceeding by or against any Person under
the United States Bankruptcy Code, or any other bankruptcy or insolvency law,
including assignments for the benefit of creditors, compositions, extensions
generally with its creditors, or proceedings seeking reorganization,
arrangement, or other relief.

     "INTELLECTUAL PROPERTY" is any copyright rights, copyright applications,
copyright registrations and like protections in each work of authorship and
derivative work, whether published or unpublished, now owned or later acquired;
any patents, trademarks, service marks and applications therefor; any trade
secret rights, including any rights to unpatented inventions, now owned or
hereafter acquired.

     "INTEREST RATE SUPPLEMENT" is that certain Interest Rate Supplement to
Agreement attached hereto and incorporated herein by reference.

     "INVENTORY" is present and future inventory in which Borrower has any
interest, including merchandise, raw materials, parts, supplies, packing and
shipping materials, work in process and finished products intended for sale or
lease or to be furnished under a contract of service, of every kind and
description now or later owned by or in the custody or possession, actual or
constructive, of Borrower, including inventory temporarily out of its custody or
possession or in transit and including returns on any accounts or other proceeds
(including insurance proceeds) from the sale or disposition of any of the
foregoing and any documents of title.

     "INVESTMENT" is any beneficial ownership of (including stock, partnership
interests or other securities) any Person, or any loan, advance or capital
contribution to any Person.

     "LETTER OF CREDIT" means a letter of credit or similar undertaking issued
by Bank pursuant to Section 2.1.2.

     "LETTER OF CREDIT FEES" is defined in Section 2.4.

     "LETTER OF CREDIT RESERVE" has the meaning set forth in Section 2.1.2.

     "LIEN" is a mortgage, lien, deed of trust, charge, pledge, security
interest or other encumbrance.

     "LOAN DOCUMENTS" are, collectively, this Agreement, any note, or notes or
guaranties executed by Borrower, and any other present or future agreement
between Borrower and/or for the benefit of Bank in connection with this
Agreement, all as amended, extended or restated.

     "MATERIAL ADVERSE CHANGE" is: (i) A material impairment in the perfection
or priority of Bank's security interest in the Collateral or in the value of
such Collateral; or (ii) a material adverse change in the business, operations,
or condition (financial or otherwise) of the Borrower; or (iii) a material
impairment of the prospect of

                                       18
<Page>

repayment of any portion of the Obligations; or (iv) Bank determines, based upon
information available to it and in its reasonable judgment, that there is a
substantial likelihood that Borrower shall fail to comply with one or more of
the financial covenants in Section 6 during the next succeeding financial
reporting period.

     "OBLIGATIONS" are debts, principal, interest, Bank Expenses and other
amounts Borrower owes Bank now or later under or in connection with this
Agreement, including letters of credit, cash management services, and foreign
exchange contracts, if any, and including interest accruing after Insolvency
Proceedings begin and debts, liabilities, or obligations of Borrower assigned to
Bank.

     "OTHER EQUIPMENT" is leasehold improvements, intangible property such as
computer software and software licenses, equipment specifically designed or
manufactured for Borrower, other intangible property, limited use property and
other similar property and soft costs approved by the Bank, excluding sales tax,
freight and installation expenses. Unless otherwise agreed to by Bank, not more
than 25% of the proceeds of the Committed Equipment Line shall be used to
finance Other Equipment.

     "PAYMENT DATE" is the first calendar day of each month.

     "PERMITTED INDEBTEDNESS" is:

               (a)  Borrower's indebtedness to Bank under this Agreement or the
     Loan Documents;

               (b)  Indebtedness existing on the Closing Date and shown on the
     Schedule;

               (c)  Subordinated Debt;

               (d)  Indebtedness to trade creditors incurred in the ordinary
     course of business;

               (e)  Indebtedness secured by Permitted Liens; and

               (f)  Extensions, refinancings, modifications, amendments and
     restatements of any items of Permitted Indebtedness (a) through (e) above,
     provided that the principal amount thereof is not increased or the terms
     thereof are not modified to impose more burdensome terms upon Borrower or
     its Subsidiary, as the case may be.

     "PERMITTED INVESTMENTS" are:

               (a)  Investments shown on the Investments Schedule and existing
     on the Closing Date; and

               (b)  (i) marketable direct obligations issued or unconditionally
     guaranteed by  the United States or its agency (including FannieMae or
     FreddieMac) or any state maturing within 1 year from its acquisition, (ii)
     commercial paper maturing no more than 1 year after its creation and having
     the highest rating from either Standard & Poor's Corporation or Moody's
     Investors Service, Inc., (iii) certificates of deposit issued maturing no
     more than 1 year after issue, and (iv) any other investments administered
     through the Bank.

     "PERMITTED LIENS" are:

               (a)  Liens existing on the Closing Date and shown on the Schedule
     or arising under this Agreement or other Loan Documents;

               (b)  Liens for taxes, fees, assessments or other government
     charges or levies, either not delinquent or being contested in good faith
     and for which Borrower maintains adequate reserves on its Books, IF they
     have no priority over any of Bank's security interests;

                                       19
<Page>

               (c)  Purchase money Liens granted in connection with the
     financing (by loan or capital lease) of Equipment in an outstanding amount
     not greater than $10,000,000.00: (i) on Equipment acquired or held by
     Borrower incurred for financing the acquisition of the Equipment, or (ii)
     existing on Equipment when acquired, IF the Lien is confined to the
     property and improvements and the proceeds of the Equipment;

               (d)  Leases or subleases and non-exclusive licenses or
     sublicenses granted in the ordinary course of Borrower's business; and

               (e)  Liens incurred in the extension, renewal or refinancing of
     the indebtedness secured by Liens described in (a) through (d), BUT any
     extension, renewal or replacement Lien must be limited to the property
     encumbered by the existing Lien and the principal amount of the
     indebtedness may not increase.

     "PERSON" is any individual, sole proprietorship, partnership, limited
liability company, joint venture, company, trust, unincorporated organization,
association, corporation, institution, public benefit corporation, firm, joint
stock company, estate, entity or government agency.

     "PRIME RATE" is Bank's most recently announced "prime rate," even if it is
not Bank's lowest rate.

     "QUICK ASSETS" is, on any date, the Borrower's consolidated, unrestricted
cash, cash equivalents, net billed accounts receivable and investments with
maturities of fewer than 12 months determined according to GAAP.

     "RESPONSIBLE OFFICER" is each of the Chief Executive Officer, President,
Chief Financial Officer and Controller of Borrower.

     "REVOLVING MATURITY DATE" is that date which is three hundred sixty-four
(364) days following the Closing Date.

     "SCHEDULE" is any attached schedule of exceptions.

     "SUBORDINATED DEBT" is debt incurred by Borrower subordinated to Borrower's
debt to Bank (pursuant to a subordination agreement entered into between the
Bank, the Borrower and the subordinated creditor), on terms acceptable to Bank.
As of the Closing Date, the BellSouth Debt shall be deemed Subordinated Debt
hereunder.

     "SUBSIDIARY" of any Person is any corporation, partnership, limited
liability company, joint venture, or any other business entity of which more
than 50% of the voting stock or other equity interests is owned or controlled,
directly or indirectly, by the Person or one or more Affiliates of the Person.

     "TANGIBLE NET WORTH" is, on any date, the consolidated total assets of
Borrower and its Subsidiaries MINUS (i) any amounts attributable to (a)
goodwill, (b) intangible items including unamortized debt discount and expense,
patents, trade and service marks and names, copyrights and research and
development expenses except prepaid expenses, and (c) reserves not already
deducted from assets, MINUS (ii) Total Liabilities, PLUS (iii) Subordinated Debt
to the extent that such Subordinated Debt is due and payable greater than one
(1) year from the applicable testing date.

     "TOTAL LIABILITIES" is on any day, obligations that should, under GAAP, be
classified as liabilities on Borrower's consolidated balance sheet, including
all Indebtedness, and current portion of Subordinated Debt permitted by Bank to
be paid by Borrower, but excluding all other Subordinated Debt.

     "TNW THRESHOLD" is Borrower's maintaining a Tangible Net Worth, as of the
last day of the month, of not less than Seventy Million Dollars
($70,000,000.00), as determined by Bank upon its review of Borrower's Compliance
Certificate and financial statements.

                                       20
<Page>

     "UNUSED COMMITTED EQUIPMENT LINE" is the maximum principal amount of the
Committed Equipment Line less the principal amount of the Equipment Advances
made thereunder (including any Equipment Advances which have been repaid by
Borrower).

            [THE REMAINDER OF THIS PAGE IS INTENTIONALLY LEFT BLANK]

                                       21
<Page>

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed as a sealed instrument under the laws of the Commonwealth of
Massachusetts as of March 25, 2002, to be effective as of January 16, 2002.

BORROWER:

SONUS NETWORKS, INC.

By:   /s/ Peter S. Hemme
   --------------------------------------------

Name:  Peter S. Hemme
     ------------------------------------------

Title: Vice President and Controller
      -----------------------------------------

BANK:

SILICON VALLEY BANK, d/b/a
SILICON VALLEY EAST

By:   /s/ Timothy O'Loughlin
   --------------------------------------------

Name:  Timothy O'Loughlin
     ------------------------------------------

Title:  Senior Vice President
     ------------------------------------------

SILICON VALLEY BANK

By:     /s/ Maggie Garcia
   --------------------------------------------

Name:   Maggie Garcia
     ------------------------------------------

Title:  AVP
      -----------------------------------------
     (Signed in Santa Clara County, California)

                                       22
<Page>

                                    EXHIBIT A

     The Collateral consists of all right, title and interest of Borrower in and
to the following:

     All goods, equipment, inventory, contract rights or rights to payment of
money, license agreements, franchise agreements, general intangibles (including
payment intangibles), accounts (including health-care receivables), documents,
instruments (including any promissory notes), chattel paper (whether tangible or
electronic), cash, deposit accounts, fixtures, letters of credit rights (whether
or not the letter of credit is evidenced by a writing), commercial tort claims,
securities, and all other investment property supporting obligations, and
financial assets, whether now owned or hereafter acquired, wherever located; and

     All Borrower's Books relating to the foregoing and any and all claims,
rights and interests in any of the above and all substitutions for, additions,
attachments, accessories, accessions and improvements to and replacements,
products, proceeds and insurance proceeds of any or all of the foregoing.

     The Collateral does not include:

     Any copyright rights, copyright applications, copyright registrations and
     like protections in each work of authorship and derivative work, whether
     published or unpublished, now owned or later acquired; any patents,
     trademarks, service marks and applications therefor; any trade secret
     rights, including any rights to unpatented inventions, now owned or
     hereafter acquired. Notwithstanding the foregoing, the Collateral shall
     include all accounts, license and royalty fees and other revenues,
     proceeds, or income arising out of or relating to any of the foregoing
     Intellectual Property.

                                       23
<Page>

                                    EXHIBIT B

                   LOAN PAYMENT/ADVANCE TELEPHONE REQUEST FORM
              DEADLINE FOR SAME DAY PROCESSING IS 3:00 P.M., E.S.T.

TO:  CENTRAL CLIENT SERVICE DIVISION                  DATE:
                                                           --------------------

FAX#:  (617) 969-5965                                 TIME:
                                                           ---------------------

--------------------------------------------------------------------------------
FROM:  SONUS NETWORKS, INC.
      ------------------------------------------------
                                CLIENT NAME (BORROWER)
REQUESTED BY:
             ------------------------------------------------------
                            AUTHORIZED SIGNER'S NAME

AUTHORIZED SIGNATURE:
                     ----------------------------------------------

PHONE NUMBER:
             ------------------------------------------------------

FROM ACCOUNT #                     TO ACCOUNT #
              --------------------             --------------------

REQUESTED TRANSACTION TYPE                  REQUEST DOLLAR AMOUNT
--------------------------                  ---------------------

PRINCIPAL INCREASE (ADVANCE)                $
                                             ----------------
PRINCIPAL PAYMENT (ONLY)                    $
                                             ----------------
INTEREST PAYMENT (ONLY)                     $
                                             ----------------
PRINCIPAL AND INTEREST (PAYMENT)            $
                                             ----------------

OTHER INSTRUCTIONS:
                    --------------------------------------------------

All Borrower's representations and warranties in the Loan and Security Agreement
are true, correct and complete in all material respects on the date of the
telephone request for and Advance confirmed by this Borrowing Certificate; but
those representations and warranties expressly referring to another date shall
be true, correct and complete in all material respects as of that date.

--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
                                  BANK USE ONLY

TELEPHONE REQUEST:

The following person is authorized to request the loan payment transfer/loan
advance on the advance designated account and is known to me.

-------------------------------------         ----------------------------
       Authorized Requester                               Phone #
--------------------------------------------------------------------------------

                                       24
<Page>

                                    EXHIBIT C
                           BORROWING BASE CERTIFICATE

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

Borrower:   SONUS NETWORKS, INC.                   Lender:   Silicon Valley Bank

Commitment Amount:   $20,000,000.00

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

<Table>
<Caption>
ACCOUNTS RECEIVABLE
<S>      <C>                                                                    <C>
1.       Accounts Receivable Book Value as of                                   $
                                             -------------------                ------------------
2.       Additions (please explain on reverse)                                  $
                                                                                 -----------------
3.       TOTAL ACCOUNTS RECEIVABLE                                              $
                                                                                 -----------------

ACCOUNTS RECEIVABLE DEDUCTIONS (without duplication)
4.       Amounts over 90 days due                                               $
                                                                                 -----------------
5.       Balance of 50% over 90 day accounts                                    $
                                                                                 -----------------
6.       Credit balances over 90 days                                           $
                                                                                 -----------------
7.       Concentration Limits                                                   $
                                                                                 -----------------
8.       Foreign Accounts                                                       $
                                                                                 -----------------
9.       Governmental Accounts                                                  $
                                                                                 -----------------
10.      Contra Accounts                                                        $
                                                                                 -----------------
11.      Promotion or Demo Accounts                                             $
                                                                                 -----------------
12.      Intercompany/Employee Accounts                                         $
                                                                                 -----------------
13.      Other (please explain on reverse)                                      $
                                                                                 -----------------
14.      TOTAL ACCOUNTS RECEIVABLE DEDUCTIONS                                   $
                                                                                 -----------------
15.      Eligible Accounts (#3 minus #14)                                       $
                                                                                 -----------------
16.      LOAN VALUE OF ACCOUNTS(80% OF #15)                                     $
                                                                                 -----------------

BALANCES
17.      Maximum Loan Amount                                                    $
                                                                                 -----------------
18.      Total Funds Available (Lesser of #16 and #17)                          $
                                                                                 -----------------
19.      Present balance owing on Committed Revolving Line                      $
                                                                                 -----------------
20.      Outstanding under Sublimits (Letter of Credit, FX Reserve, Cash Mngt)  $
                                                                                 -----------------
21.      RESERVE POSITION (#18 minus #19 and #20)                               $
                                                                                 -----------------
</Table>

THE UNDERSIGNED REPRESENTS AND WARRANTS THAT THIS IS TRUE, COMPLETE AND CORRECT,
AND THAT THE INFORMATION IN THIS BORROWING BASE CERTIFICATE COMPLIES WITH THE
REPRESENTATIONS AND WARRANTIES IN THE LOAN AND SECURITY AGREEMENT BETWEEN THE
UNDERSIGNED AND SILICON VALLEY BANK.

                                                         BANK USE ONLY

COMMENTS:                                    Received by:
                                                         ----------------------
                                                           AUTHORIZED SIGNER
                                             Date:
                                                  ------------------------------

By:                                          Verified:
   -------------------------                          --------------------------
        Authorized Signer                                  AUTHORIZED SIGNER

                                             Date:
                                                  -----------------------------

                                             Compliance Status: Yes  No

                                       25
<Page>

                                    EXHIBIT D
                             COMPLIANCE CERTIFICATE

TO:      SILICON VALLEY BANK

FROM:    SONUS NETWORKS, INC.

     The undersigned authorized officer of SONUS NETWORKS, INC. certifies that
under the terms and conditions of the Loan and Security Agreement between
Borrower and Bank (the "Agreement"), (i) Borrower is in complete compliance for
the period ending _______________ with all required covenants except as noted
below and (ii) all representations and warranties in the Agreement are true and
correct in all material respects on this date. Attached are the required
documents supporting the certification. The Officer certifies that these are
prepared in accordance with Generally Accepted Accounting Principles (GAAP)
consistently applied from one period to the next except as explained in an
accompanying letter or footnotes. The Officer acknowledges that no borrowings
may be requested at any time or date of determination that Borrower is not in
compliance with any of the terms of the Agreement, and that compliance is
determined not just at the date this certificate is delivered.

     PLEASE INDICATE COMPLIANCE STATUS BY CIRCLING YES/NO UNDER "COMPLIES"
COLUMN.

<Table>
<Caption>
     REPORTING COVENANT                      REQUIRED                               COMPLIES
     ------------------                      --------                               --------
     <S>                                     <C>                                    <C>
     Financial statements with CC            Monthly within 25 days                 Yes  No
     BBC w/ A/R Agings                       Monthly w/in 25 days*                  Yes  No
     10-Q, 10-K and 8-K                      Within 5 days after filing with SEC    Yes  No
     Balance Sheet, Income Statement, and    FYE within 45 days                     Yes  No
</Table>

     Cash Projections (plus all revisions approved by Board)

* To be submitted by Borrower to Bank in accordance with Section 6.2 of the Loan
and Security Agreement

<Table>
<Caption>
     FINANCIAL COVENANT                      REQUIRED                            ACTUAL            COMPLIES
     ------------------                      --------                            ------            --------
     <S>                                     <C>                                <C>                <C>
     Minimum Quick Ratio (monthly)           1.5:1.0                                  :1.0         Yes   No
                                                                                ------
     Minimum Tangible Net Worth (monthly)    (i) $70,000,000 thru 3/31/02,      $                  Yes   No
                                                                                 --------
                                             $60,000,000 thru 9/30/02,          $                  Yes   No
                                                                                 --------
                                             and $50,000,000 after 9/30/02;     $                  Yes   No
                                                                                 --------
                                             PLUS (ii) 50% of new equity issued.
</Table>

COMMENTS REGARDING EXCEPTIONS:  See Attached.             BANK USE ONLY

Sincerely,                                    Received by:
                                                          ---------------------
                                                            AUTHORIZED SIGNER

-----------------------------                 Date:
SIGNATURE                                          ----------------------------

                                              Verified:
-----------------------------                          ------------------------
                                                           AUTHORIZED SIGNER
TITLE
                                              Date:
-----------------------------                      ----------------------------
DATE
                                             Compliance Status:   Yes     No

                                       26

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