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                                                                   EXHIBIT 10.28


                  ENGINEERING SERVICES AGREEMENT NO. 20-03-003


THIS AGREEMENT made as of the 2nd day of October, 2000 by and between Unisphere
Networks Inc., a corporation incorporated under the laws of Delaware, with its
principal office located at One Executive Drive, Chelmsford, MA 08124
(hereinafter called "USI") and Siemens Information and Communication Networks,
Inc., a corporation incorporated under the laws of Delaware, with its principal
office located at 900 Broken Sound Parkway, Boca Raton, Florida, United States
of America 33487 (hereinafter called "Siemens"). Collectively, the
aforementioned participants to this Agreement shall be called the "Parties", or
singularly, as the "Party".

WHEREAS, USI desires to enter into a time and material contract for engineering
services (hereinafter called "Services"); and

WHEREAS, Siemens desires to provide such Services on a time and material basis;

NOW THEREFORE, in consideration of the mutual promises contained herein and
other valuable consideration, the receipt and adequacy of which is hereby
acknowledged, the Parties agree as follows:

ARTICLE 1 - PROJECTS

1.1      This Agreement covers the prices for time and material development
         Services anticipated for two (2) projects:

1.1.1    "LOCAL NUMBER PORTABILITY" (LNP), a software feature enhancement; and

1.1.2    "DIGITAL TONE MODULE VERSION 1 (DTM1)", an application module for the
         USI SMX-2100 product, comprised of hardware and embedded software
         supporting Channel Associated Signaling and echo cancellation.

1.2      Siemens shall follow the development procedures as directed by USI.
         Such procedures shall be provided to Siemens prior to the acceptance
         and commencement of any project hereunder. When no procedures exist,
         Siemens personnel will use Siemens procedures where appropriate or will
         use sound engineering judgement to identify an appropriate course of
         action.

1.3      Siemens furnished personnel for performance of Services shall be
         subject to Siemens' direction and control.

1.4      Siemens will provide, at no additional cost to USI, appropriate office
         and lab facilities at Siemens' facilities to house and support Siemens'
         personnel performing the Services.

1.5      USI shall provide all necessary hardware and software development
         tools, documentation, training, SMX-2100 switches, personal computers,
         test equipment, and emulation equipment.

         USI shall provide timely technical support to Siemens personnel for the
         projects. Any materials and/or equipment furnished by USI shall be
         deemed bailed to Siemens, and title thereto shall at all times remain
         in USI.



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1.6      This technical support shall include training, dependent hardware and
         software designs, periodic design reviews, software configuration
         management, and maintenance for USI development tools and processes.
         All support, tools, equipment or information delivered by USI is
         provided "AS IS", with no warranty whatsoever.

1.7      Upon the earlier of USI's request or completion of the projects under
         this Agreement, Siemens will return all USI supplied capital equipment,
         documentation, software, etc, to USI at USI's expense.

1.8      The delivery schedule for the LNP project will be determined through
         ongoing discussions between the responsible engineering managers.
         Regardless of content, Siemens' commitment for engineering services
         will not extend beyond April 30, 2000.

1.9      The delivery schedule for the DTM1 project will be determined through
         ongoing discussions between the responsible engineering managers.
         Regardless of content, Siemens' commitment for engineering services
         will not extend beyond July 31, 2000. The electronic mail message
         entitled "DTM1 Schedules and Deliverables", dated March 29, 2000, sent
         by Brad Bridges (responsible engineering manager at Siemens) to Steve
         Converse (responsible engineering manager at USI) documents the most
         recent content and delivery schedule agreement. The final content of
         the DTM1 project will be determined between the parties prior to July
         31, 2000.

1.10     Siemens may agree to provide technical support for the products
         delivered under this Agreement under terms and conditions to be
         mutually agreed and set forth in a separate agreement to be executed
         between the parties.

1.11     Delivery of software under the projects shall include both source and
         object code, and shall include the final version and all intermediate
         versions along with all data, codes or other information generated by
         Siemens under this Agreement or necessary for use by USI to exercise
         its rights hereunder, including without limitation all routines and
         subroutines, program materials, flowcharts, notes, outlines, formulae,
         processes, algorithms and ideas.


ARTICLE 2 - TIME AND MATERIAL PRICES

2.1      During the term of this Agreement, Siemens will provide USI Services at
         a rate of $77.95 per Staff-hour, which shall be fixed for the term of
         this Agreement. "Staff-hour" shall mean an hour of engineering labor.

2.2      At no time shall Siemens charge uncompensated overtime to USI.

2.3      Siemens will provide a monthly Staff-hour ramp to USI, which shall be
         utilized as an estimate for the current month. Siemens will keep
         written records and make reports about work performed, as may be
         reasonably requested by USI. Upon termination or expiration of this
         Agreement, Siemens will deliver to USI, at its request, all such
         records. Thereafter Siemens will make no further use or utilization of
         any such material without the prior written consent of USI, except as
         required by law or generally accepted accounting and record principles.

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2.4      During the term of this Agreement Siemens staff years to be billed
         shall not exceed eighteen (18). The number of staff years anticipated
         to complete the projects has been estimated by Siemens, and has been
         the basic consideration under which this Agreement has been entered
         into by the parties. The electronic mail messages entitled "DTM1
         Estimates", dated "June 28, 1999" sent from Brad Bridges (Siemens) to
         Mike Regan (USI), and "RE: DTM1 Support/Needs", dated "June 29, 1999"
         from Mike Regan (USI) to Brad Bridges (Siemens) document the basic
         considerations for the DTM1 project. The basic considerations for the
         LNP project have been determined through verbal discussions between
         Siemens and USI engineering management. Any additional staff year
         requirements must have prior approval of USI. Siemens shall have no
         obligation to provide Services in excess of 18 staff years. Should
         Siemens agree to provide Services over the 18 staff years, such
         Services shall be provided only on a time and material basis. Siemens
         also shall have no obligation to provide a minimum of 18 staff years of
         service. The final delivery content and schedule for the projects will
         determine the actual staff year effort expended.

         Siemens enters into this Agreement as, and shall continue to be, an
         independent contractor. Under no circumstances shall Siemens look to
         USI as Contractor's employer, nor as a partner, agent, or principal.
         Siemens shall not be entitled to any benefits accorded to USI' s
         employees including, without limitation, workers compensation,
         disability insurance, vacation or sick pay or the right to participate
         in the USI 401(k) Retirement Savings Plan or Employee Stock Purchase
         Plan. Siemens specifically waives the right to receive any such
         benefits or participate in any such plans for the term of this
         Agreement or while the parties agree that Siemens is providing services
         to USI as a contractor, even if Siemens later becomes or is designated
         an employee of USI.

2.5      The price of any materials used in the performance of or delivered
         under this Agreement shall be the cost of the materials to Siemens plus
         a fee of five percent (5%) of such material cost.


ARTICLE 3 - PAYMENT TERMS

3.1      Siemens shall invoice on a monthly basis. Such invoice will include the
         number of hours worked per individual per week and all other reasonable
         information to support the amount billed.

3.2      USI shall pay each undisputed invoice within thirty (30) days of
         receipt thereof. USI shall have seven (7) business days from date of
         receipt of invoice to dispute any charges after which time such charges
         will be understood as accepted.

3.3      Any additional charges such as travel and materials utilized by Siemens
         as a result of this Agreement shall be billed separately to USI. All
         such charges shall be approved in advance by USI and paid within thirty
         (30) days of receipt of invoice.

3.4      USI will pay for all travel and travel expenses required of Siemens
         staff during this Agreement. Travel must be approved in advance by USI.


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3.5      USI will pay for all other incidental costs incurred by Siemens staff
         which are directly related to and necessary for the completion of the
         projects. Expenses in excess of $1,000 must be approved in advance.
         Expenses are to be submitted directly to USI on a form to be mutually
         agreed.


ARTICLE 4 - INTELLECTUAL PROPERTY RIGHTS

4.1      USI shall own all intellectual property and inventions created in the
         process of performing work under this Agreement. Subject to the limited
         grant-back provisions set forth in Section 4.2 below, Siemens hereby
         irrevocably assigns to USI all right, title and interest in and to all
         ideas, inventions, discoveries, improvements and other know-how or
         rights that are discovered, developed, created or conceived by Siemens
         in performing its work under this Agreement, and all intellectual
         property rights therein, including without limitation any and all
         copyrights, patent rights or trade secrets (hereinafter collectively
         "Intellectual Property").

4.2      USI hereby grants to Siemens a fully paid-up, royalty-free,
         non-exclusive, worldwide, irrevocable license to use, make, have made
         and sell and sublicense Intellectual Property associated with LNP and
         Intellectual Property associated with the following aspects of the
         DTM1:

         (i)    the Echo Cancellation Daughtercard; and

         (ii)   all application and control software developed by Siemens
         for the DTM1 MPC8260 processor; and

         (iii)  all application and control software developed by Siemens for
         the DTM1 Digital Signal Processor(s) (Section 4.2 collectively
         hereinafter the "Grantback License").

4.3      The Grantback License is expressly subject to the following
         exclusions, conditions and limitations:

         (i) USI grants no rights to any third party software, hardware or
         technology pursuant to the Grantback License, and Siemens agrees that
         if any third party rights or licenses are required in order to enable
         Siemens to exploit the Grantback License, Siemens shall be solely
         responsible for securing such rights or licenses directly with the
         applicable third party(ies); and

         (ii) Notwithstanding anything which may be construed to the contrary in
         this Agreement, in no event shall the Grantback License confer upon
         Siemens any right, title or interest in or to the SMX-2100 hardware or
         software, the NMC-SMX (Sentry) Element Management System hardware or
         software, or any intellectual property rights therein.

4.4      Siemens agrees, at USI's expense, to assist in the preparation and
         prosecution of any patent or copyright application and to execute and
         cause its employees to execute all applications for patents and/or
         copyrights, domestic and foreign, assignment and other papers necessary
         to secure and enforce rights related to work performed under this
         Agreement. Siemens agrees to obtain or has obtained written assurances
         from its employees and


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         contract personnel of their agreement to the terms hereof. If Siemens
         delivers products or designs containing intellectual property owned by
         Siemens and not created during the performance of this Agreement,
         Siemens hereby grants USI a fully-paid, royalty-free, non-exclusive,
         worldwide, irrevocable license to use and to sublicense such
         intellectual property for use only in the LNP and DTM1 products. USI
         shall continue to retain all rights in any intellectual property it
         provided to Siemens to perform the work under this Agreement and
         Siemens does not acquire any rights in such intellectual property.


ARTICLE 5 - CONFIDENTIAL INFORMATION

5.1      Each Party shall maintain the confidentiality of the other Party's
         confidential information and shall not, without the other Party's prior
         written consent, (a) use such confidential information in any manner
         not authorized under this agreement, or (b) disclose any such
         confidential information in any form to any person, except to its
         employees whose access is necessary in connection with the performance
         of this Agreement. "Confidential Information" means any business or
         technical information of either Party, that (a) is provided to the
         other Party in connection with this Agreement, (b) concerns the Party's
         business, methods, plans, designs, procedures, systems operations, or
         technology, research, marketing, sales, customer or financial data, and
         (c) has been identified in writing as being proprietary to a Party or
         marked "proprietary" or "confidential" or, if disclosed orally, is
         confirmed subsequently in writing to be confidential or proprietary.
         Confidential Information does not include any information that is or
         becomes publicly disclosed by a Party or lawfully by a non-party to
         this Agreement or which is disclosed pursuant to legal process provided
         that prompt notice is provided to the disclosing party so as to enable
         the disclosing party to seek relief from the disclosure.

5.2      Siemens shall use USI supplied hardware, software and supporting
         documentation only for the purpose of developing the products described
         in this agreement. Unless otherwise mutually agreed as set forth in a
         written modification to this Agreement signed by both parties, USI does
         NOT grant rights for any other use.


ARTICLE 6 - WARRANTIES AND DISCLAIMER


6.1      With the exception of willful misconduct, or negligent assembly or
         design, all deliverables under this Agreement will be delivered "AS IS"
         without warranty of any kind. Siemens' sole obligation and USI's sole
         remedy in the event of breach of this warranty shall be the replacement
         or repair of defective hardware and the redesign in accordance with
         standard design procedures of the affected software. SIEMENS
         SPECIFICALLY DISCLAIMS ALL EXPRESS OR IMPLIED WARRANTIES, INCLUDING THE
         WARRANTIES OF MERCHANTABILITY, FITNESS FOR ANY PARTICULAR PURPOSE, AND
         FREEDOM FROM PATENT AND COPYRIGHT INFRINGEMENT.




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ARTICLE 7 - INDEMNIFICATION


7.1      Siemens agrees, at its expense, to defend USI in any suit, claim or
         proceeding brought against USI alleging that any equipment manufactured
         by Siemens or software or design created by Siemens and furnished
         hereunder directly infringes any U.S. Letters Patent, copyright or
         other intellectual property rights, provided Siemens is promptly
         notified, given assistance required, and permitted to direct the
         defense. Siemens agrees to pay any judgment based on infringement
         rendered in such suit by final judgment of a court of last resort, but
         Siemens shall have no liability for settlements or costs incurred
         without its consent. In addition, and by way of limitation, should the
         use of any such equipment or software by USI be enjoined, Siemens' only
         obligation is to refund to USI the price paid for the infringing item
         or design as complete damages for the loss of future use of the
         infringing item or design. The foregoing states the entire liability of
         Siemens for patent or copyright infringement or for any breach of
         warranty of noninfringement, express or implied. The foregoing
         indemnity shall not apply and USI agrees to indemnify Siemens in a
         manner fully equivalent to the foregoing in any suit, claim or
         proceeding brought against Siemens in which and to the extent the
         alleged infringement arises from equipment, software, data or design
         made to the specification or design of USI or from the modification of
         the equipment, software, data or design by anyone other than Siemens or
         the combination of any equipment or software purchased pursuant to this
         contract with products or software supplied by USI or others.

ARTICLE 8 -  LIMITATION OF LIABILITY

 8.1     Each party's entire liability arising out of or in connection with this
         Agreement, regardless of the form of action, whether based on contract
         or tort, including negligence, including, without limitation the
         furnishing, the failure to furnish or the quality of any Service, shall
         in no event exceed the amount paid by USI under this Agreement. The
         foregoing limitation of liability shall not apply to loss, damages or
         liabilities arising out of Sections 5 or 7.1 above.

8.2      IN NO EVENT WILL EITHER PARTY BE LIABLE FOR DAMAGES HEREUNDER IN
         RESPECT OF SPECIAL, INCIDENTAL, INDIRECT, OR CONSEQUENTIAL LOSS, (EVEN
         IF IT HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH LOSS) INCLUDING, BUT
         NOT LIMITED TO, LOST BUSINESS REVENUE, LOSS OF PROFITS, LOSS OF DATA,
         FAILURE TO REALIZE EXPECTED PROFITS OR SAVINGS OR ANY CLAIM AGAINST
         CUSTOMER BY ANY OTHER PERSON.


ARTICLE 9  -  NOTICES


9.1      Any notices or demands that are required by law or under the terms of
         this Agreement shall be given or made by a Party in writing and shall
         be given by hand delivery, facsimile or similar communication, or by
         certified or registered mail, and addressed to the respective Party set
         forth below. Such notices shall be deemed to have been given in the
         case of facsimile or similar communications when delivered, and in the
         case of certified or registered mail, five (5) days after the date when
         mailed postage prepaid.


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         To USI:     Unisphere Networks, Inc
                     One Executive Drive
                     Chelmsford, MA 01824
         Attention:  Michael Regan, Vice President of Engineering

         To Siemens: Siemens Information and Communication Networks, Inc.
                     900 Broken Sound Parkway
                     Boca Raton, Florida  33487
         Attention:  Manager of Contracts

     The above addresses may be changed at any time by giving thirty (30) days
prior written notice.

ARTICLE 10  - AGREEMENT TERM

10.1     The term of this Agreement shall commence July 1, 1999 and end July 31,
         2000. Siemens and USI may, subject to Article 13.1, extend the content
         and duration of the noted projects or extend this Agreement for
         additional projects, under terms and conditions to be mutually agreed.

ARTICLE 11 - ASSIGNMENT

11.1     Neither party shall assign or otherwise transfer its rights or
         obligations under this Agreement except with prior written consent of
         the other Party, such consent not to be unreasonably withheld;
         provided, however, either Party may assign this Agreement to any
         present or future affiliate, subsidiary, parent corporation or
         successor in interest to substantially all of the business assets
         without securing the consent of the other Party and may grant to any
         such assignee the same rights and privileges granted under this
         Agreement. Any attempted assignment not assented to in the manner as
         prescribed herein shall be void.

ARTICLE 12  - CHOICE OF LAW

12.1     The laws of the Commonwealth of Massachusetts excluding its Choice of
         Law rules shall govern this Agreement.


ARTICLE 13  - ENTIRE AGREEMENT


 13.1    This Agreement constitutes the entire agreement between the Parties
         with respect to the subject matter contained herein, superseding all
         previous agreements pertaining to such subject matter, and may be
         modified only by an amendment executed in writing by both Parties.



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IN WITNESS WHEREOF, the Parties have executed this Agreement by their duly
authorized representatives as of the day first above written.




UNISPHERE NETWORKS INC.                     SIEMENS INFORMATION AND
                                            COMMUNICATION NETWORKS, INC.





By: /s/ Michael D. Regan                   By: /s/ Dieter Diehn
    -------------------------------------      -----------------------------

Michael D. Regan
Vice President Engineering




                                                         Agreement No. 20-03-003