Sonus Networks, Inc.
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                                          250 Apollo Drive, Chelmsford, MA 01824

August 9, 2005

Mr. Paul McDermott
18 Nipmuck Drive
Westborough, MA 01581

Dear Paul:

I am  pleased  to  provide  you with the  terms and  conditions  of our offer of
employment to you by Sonus Networks, Inc. (the "Company").

1.   Position.    Your initial position will be VP, Corporate Controller and VP,
Finance,  reporting to Ellen Richstone,  Chief Financial Officer. In addition to
performing  duties and  responsibilities  associated  with the  position  of VP,
Controller  from  time to time the  Company  may  assign  you other  duties  and
responsibilities.

As a full-time employee of the Company, you will be expected to devote your full
business time and energies to the business and affairs of the Company.

2.   Starting  Date/Nature of Relationship.  It is expected that your employment
will start on or within 1 week from August 29, 2005. No provision of this letter
shall be  construed  to create an express or implied  employment  contract for a
specific period of time.  Employment at Sonus  Networks,  Inc. is considered "at
will" and either you or the Company may terminate the employment relationship at
any time and for any reason.

3.   Compensation.

     (a)  Your  initial  salary  will be  annualized  at  $190,000.  You will be
          eligible to participate in the Bonus Program for 2005 (pro-rated) with
          a target of 20% of annual base salary.  Objectives will be agreed upon
          within the first ninety days of your employment.

     (b)  You will be granted  an option to  purchase  150,000  shares of common
          stock under the Company's  Incentive Stock Plan,  subject to the terms
          of the Plan and approval of the Stock Option Committee. Should the
          Company implement a change of control provision for corporate
          officers, this position will be included.

4.   Employment  Eligibility.  In  compliance  with the  Immigration  Reform and
Control Act of 1986,  you are required to establish your identity and employment
eligibility.  Therefore, on your first day of employment you will be required to
fill out an  Employment  Verification  Form and present  documents in accordance
with this form.

5.   Benefits.  You will be  entitled  as an  employee of the Company to receive
such benefits as are generally provided its employees in accordance with Company
policy as in effect from time to time.  Company  benefits  include group health,
life and dental insurance, and liberal holidays, vacation and 401K programs. All
employees  begin  accruing  three (3) weeks of vacation  upon date of hire.  The
Company is committed to providing a healthy work environment for every employee.
Therefore,  we provide a smoke free  environment  and require all  employees  to
comply.

The Company retains the right to change, add or cease any particular benefit.

6.   Confidentiality.  The Company  considers the protection of its confidential
information and  proprietary  materials to be very  important.  Therefore,  as a
condition  of your  employment,  you and the Company  will  become  parties to a
Noncompetition and Confidentiality  Agreement.  Two copies of this agreement are
sent with this offer  letter.  Both  copies  must be signed and  returned to the
Company prior to the first day of employment.

7.   General.

     (a)  This letter will constitute our entire agreement as to your employment
          by  the   Company  and  will   supercede   any  prior   agreements  or
          understandings, whether in writing or oral.

     (b)  This  letter  shall  be  governed  by the law of the  Commonwealth  of
          Massachusetts.

     (c)  Sonus Networks is an equal opportunity employer.

You may accept this offer of employment and the terms and conditions  thereof by
confirming your acceptance by August 17, 2005. Please send your signed letter to
the Company, or via e-mail to Nancy Forte at nforte@sonusnet.com which execution
will evidence your  agreement with the terms and conditions set forth herein and
therein.  You may retain the enclosed copy of this letter for your  records.  We
are  enthusiastic  about you  joining  us, and believe  that our  technical  and
business  goals will provide every  opportunity  for you to achieve you personal
and professional objectives.

Very truly yours,

/s/Colleen Humphrey
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Colleen Humphrey
Director, Human Resources