Document:

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                                                                     EXHBIT 10.9
                                                                     -----------

        CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH THE
         SECURITIES AND EXCHANGE COMMISSIONP URSUANT TO A REQUEST FOR
                            CONFIDENTIAL TREATMENT.
                      ASTERISKS(*) DENOTE SUCH OMISSIONS.

                             PROCUREMENT AGREEMENT
                             ---------------------

This Procurement Agreement ("Agreement") is made as of the 17th day of May, 2000
("Effective Date") between Avici Systems, Inc., a Delaware corporation, with its
address at 101 Billerica Avenue, N. Billerica, Massachusetts 01862-1256
("Avici") and Williams Communications, Inc., a Delaware corporation, with its
address at One Williams Center, Tulsa, Oklahoma 74172 ("Customer").

The parties agree as follows:

1.0  DEFINITIONS

1.1  "Affiliate" shall mean with respect to any entity, any other entity which
     controls, is controlled by, or is under common control with, such entity,
     and for these purposes, "control" means interest, voting or otherwise, of
     more than fifty percent (50%) in an entity.

1.2  "Delivery Point" shall have the meaning described in Section 3.3.

1.3  "Documentation" refers to manuals, handbooks, maintenance libraries and
     other publications of Avici which are normally supplied by Avici with the
     Product or Software.

1.4  "POP" shall mean a telecommunications point of presence and unless the
     context indicates otherwise, refers to a Customer-designated point of
     presence.

1.5  "Product" means a terabit switch router which may be comprised of various
     combination/configurations of the products and equipment set forth in
     Attachment A with the term Product including all such possible
     combinations/configurations.  Unless otherwise indicated, Product also
     includes all Software.

1.6  "Services" means all the services provided by Avici to Customer pursuant to
     the terms of this Agreement or a purchase order issued under this
     Agreement.

1.7  "Software" refers to software products in machine executable, object code
     form, supplied with, or embedded in, a Product.  The term Software applies
     to all parts of Software, and to new releases, updates and modifications of
     Software and of Third Party Software.

1.8  "Specifications" means the specifications contained in the relevant
     Documentation or as set forth in Attachment B.

1.9  "Third Party Software" means Software which is independently developed by a
     third party and licensed or sublicensed to Customer by Avici in connection
     with this Agreement.

                                                                    Page 1 of 37
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2.0  PURCHASE TERMS

2.1  PURCHASES.  During the term of this Agreement and subject to the terms and
     conditions of this Agreement, Avici shall sell to Customer and Customer
     shall purchase (or in the case of Software, license), from Avici, Products,
     Software and/or Services in all aggregate amount of at least [CONFIDENTIAL
     TREATMENT REQUESTED]/*/ at the prices and fees listed in Attachment
     A [CONFIDENTIAL TREATMENT REQUESTED]/*/. For purposes of clarity, to the
     extent the prices actually paid by Customer under a purchase order differs
     from those set forth in Attachment A, then the actual prices paid by
     Customer shall be utilized for the purposes of determining if Customer has
     met its purchase obligations under this Section 2.1 and Section 2.2.
     [CONFIDENTIAL TREATMENT REQUESTED]/*/. It is understood that the prices and
     fees set forth in Attachment A represent Avici's list prices and fees
     Current as of the Effective Date. If, during the term of this Agreement,
     Avici's list prices and fees change, Customer's purchases made thereafter
     shall be at the new list price or fee [CONFIDENTIAL TREATMENT
     REQUESTED]/*/.

2.2  PURCHASE TIMING.

     a) Customer shall (i) purchase (or in the case of Software, license) at
     [CONFIDENTIAL TREATMENT REQUESTED]/*/ of Product, Software and/or Services
     which shall be shipped by December 31, 2000; and (ii) between January 1,
     2001 and December 31, 2001, purchase (or in the case of Software, license)
     at least the lesser of: (x) [CONFIDENTIAL TREATMENT REQUESTED]/*/ of
     Product, Software and/or Services or (y) the difference between
     [CONFIDENTIAL TREATMENT REQUESTED]/*/ and the total amount of the Products,
     Software and/or Services which were shipped prior to December 31, 2000. For
     purposes of determining when purchases are to be credited against the
     obligations in Sections 2.1 and 2.2, the date of shipment shall be used.
     Provided that, if Products or Software are, through no fault of Customer,
     not shipped on the accepted shipment date, the accepted shipment date shall
     for the purpose of making the calculations under Section 2.1 and this
     Subsection 2.2(a), be deemed to be the shipment date.

     b)  Prior to October 27, 2000, Customer shall issue a purchase order or
     purchase orders to Avici for Products, Software and/or Services with
     requested shipment dates and in amounts sufficient to enable Avici to ship
     Products, Services and/or Software in all aggregate amount of at least
     [CONFIDENTIAL TREATMENT REQUESTED]/*/ by no later than December 31, 2000,
     provided such shipment dates will be determined in accordance with the
     provisions of Section 3.1. Customer shall issue a purchase order or
     purchase orders to Avici for Products, Software and/or Services with
     requested shipment dates and will amounts sufficient to enable Avici to
     ship Products, Services and/or Software in an aggregate amount of at least
     [CONFIDENTIAL TREATMENT REQUESTED]/*/ by no later than December 31, 2001
     provided that such shipment dates shall be determined in accordance with
     the provision of Section 3.1.

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                    Page 2 of 37
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2.3  PERFORMANCE CONTINGENCIES.

     a)  (i)  Customer's obligation to purchase (or in the case of Software,
          license) any Product, Software and/or Services under this Agreement
          shall be subject to the Product having successfully passed a test
          ("Test"), the scope of the Test being limited to demonstrating the
          Product's compliance with the Specifications in Attachment B. The
          terms of the Test shall be mutually agreed between Customer and Avici
          within [CONFIDENTIAL TREATMENT REQUESTED]/*/ from the Effective Date.
          Avici shall be responsible for preparing and submitting to Customer
          the initial, proposed version of the Test. The Test will be conducted
          [CONFIDENTIAL TREATMENT REQUESTED]/*/ utilizing a Product installed by
          Avici, [CONFIDENTIAL TREATMENT REQUESTED]/*/

          (ii) Within [CONFIDENTIAL TREATMENT REQUESTED]/*/ from agreement upon
          the Test, Avici shall provide Customer written notice indicating that
          the Test Unit is ready for testing ("Notice of Readiness to Test") and
          shall contain a proposed schedule for conducting the Test, indicating
          proposed dates and times. Within [CONFIDENTIAL TREATMENT REQUESTED]/*/
          from receipt of the Notice for Readiness to Test, Customer and Avici
          shall agree upon a schedule for conducting the Test ("Test Schedule")
          which schedule shall provide for the Test to be conducted by no later
          than [CONFIDENTIAL TREATMENT REQUESTED]/*/. Within [CONFIDENTIAL
          TREATMENT REQUESTED]/*/of completion of the initial Test, Customer
          shall advise Avici, in writing, if the Test Unit has (X) successfully
          performed or (Y) failed to successfully perform the Test.

          (iii)  Should the Test Unit fail to successfully perform the initial
          Test, then Avici shall, for a period of [CONFIDENTIAL TREATMENT
          REQUESTED]/*/ following the notice from Customer that the Test Unit
          has failed to successfully perform the Initial Test, have the right to
          carry out any repairs or modifications to the Test Unit Avici deems
          appropriate and upon notice from Avici that the Test Unit is ready for
          re-testing, reperform the Test subject to a schedule Mutually agreed
          between the parties within [CONFIDENTIAL TREATMENT REQUESTED]/*/ of
          the notice from Avici that Avici is really to reperform the Test.
          Customer shall promptly notify Avici, in writing, of the results of
          any such retesting. Avici shall have, during the [CONFIDENTIAL
          TREATMENT REQUESTED]/*/ period described in this clause (iii), the
          right to reperform the Test more than once.

          (iv) Within [CONFIDENTIAL TREATMENT REQUESTED]/*/ of successful
          completion of the Test, Customer and Avici shall jointly execute an
          acknowledgement ("Acknowledgement Certificate") that the Test Unit has
          satisfied the Test. It is understood that the issuance of an
          Acknowledgement Certificate shall not relieve or excuse Avici from the
          performance of any of its obligations, nor constitute a waiver of any
          fights or remedies Customer may have under this Agreement, including
          any warranty obligations in respect to the Product and Software.

          (v) If by the [CONFIDENTIAL TREATMENT REQUESTED]/*/ following the date
          of Customer's notice that the Test Unit has failed to successfully
          perform the initial Test, the Test Unit,

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

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          despite any modifications or repair Avici chose to make to the Test
          Unit during such period, has still not successfully performed the
          Test, then Customer shall be entitled to terminate this Agreement
          pursuant to the terms of Section 4.3

          (vi) The cost of preparation for, and the conducting of, the Test
          shall he borne by Avici.  Avici shall be responsible for any loss of,
          or damage to, the Test Unit unless the damage or loss is caused by
          Customer's representatives, employees, agents or, contractors.
          Customer shall have the right to have a representative or,
          representatives present during each performance of the Test.

          (vii) [CONFIDENTIAL TREATMENT REQUESTED]/*/

     (b) Avici shall meet the development milestones set forth in Attachment B-1
     concerning the addition of new features or capabilities to the Product.
     Upon the development of each new feature or capability, it will be made
     available by Avici for purchase by the Customer and each such new feature
     or capability shall become part of the Specifications and such amended
     Specifications shall apply to the relevant Products shipped thereafter.  No
     later than December 31, 2000, the parties will agree in writing upon
     specifications (with timelines) in addition to those contained in
     Attachment B-1, such additional specifications shall, upon agreement
     thereto by the parties, apply to all Product and/or Software scheduled to
     be shipped after December 31, 2000.  These additional specifications which
     are to be agreed by December 31, 2000, will be limited to applicable core
     router related protocols and other technologies that are, or will be,
     adopted by major standards bodies (IETF, IEEE, ITU) in the year 2001 and
     technologies that are, or will be, generally commercially available within
     the industry in 2001.  Specifications not in effect when particular
     Products and/or Software are shipped shall not be applied retroactively
     with respect to such previously shipped item.

     (c) Avici shall, with respect to each feature, capability or specification
     described in Subsection 2.3(b), promptly provide Customer with notice of
     such development thereof.

     (d) If Avici fails to meet a milestone as specified in Attachment B-1 or as
     will be specified by December 31, 2000, Customer shall remain obligated to
     purchase Products unrelated to such milestone which Customer has agreed to
     purchase Pursuant to this Agreement.

2.4  PAYMENT TERMS.

     (a) Avici will invoice Customer upon shipment of Products, and upon the
     completion of any Services. Payment terms are [CONFIDENTIAL TREATMENT
     REQUESTED]/*/, from the date Customer receives the invoice. Subject to
     Avici's credit approval and Customer's continuing good credit standing,
     Customer shall pay all invoices within [CONFIDENTIAL TREATMENT
     REQUESTED]/*/ of receipt. If Customer disputes any invoice rendered (or a
     portion thereof), Customer shall so notify Avici and

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

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     the parties will use their best efforts to resolve such dispute
     expeditiously. Provided that Customer so notifies Avici of a disputed
     invoice and there is a good-faith basis for such dispute, the time for
     paying the portion of the invoice in dispute shall be extended by a period
     of time equal to the time between Avici's receipt of such notice of dispute
     from Customer and [CONFIDENTIAL TREATMENT REQUESTED]/*/ after resolution of
     such dispute. Payment of the amount determined to be due shall be made by
     Customer with interest from the original due date at the rate of
     [CONFIDENTIAL TREATMENT REQUESTED]/*/ per annum. Customer shall pay for
     non-disputed items in accordance with the terms of this Agreement. All
     invoices will be payable by check or wire transfer, to Avici's account.

     (b) With respect to undisputed amounts Avici reserves the right to impose a
     late payment charge of [CONFIDENTIAL TREATMENT REQUESTED]/*/ per month, or
     the maximum allowed by law, whichever is less for each month that any
     payment is late, excluding the month in which the payment was due and not
     paid.

2.5  CURRENCY AND TAXES.  All payments will be made in United States dollars.
     Customer will pay all municipal, state, county or federal taxes including,
     but not limited to sales, use excise, value added or other taxes which may
     be levied upon the sale, license, transfer, ownership or installation of
     the Products (except for any taxes imposed upon the Products prior to
     shipment or taxes imposed upon the income of Avici or upon its employment
     base).

[CONFIDENTIAL TREATMENT REQUESTED]/*/

3.0  TERMS OF SUPPLY

3.1  ORDERING.  All purchases under this Agreement will be initiated by
     Customer's issuance of written purchase orders to Avici.  Such purchase
     orders shall be submitted to Avici's address set forth in Section 15.4.
     Avici will confirm receipt of Customer's orders within [CONFIDENTIAL
     TREATMENT REQUESTED]/*/ of receipt. Avici will execute and deliver to
     Customer an order acceptance within [CONFIDENTIAL TREATMENT REQUESTED]/*/
     after Avici's receipt of each purchase order. Acknowledgment of receipt and
     order acceptance shall be sent by Avici to the attention of Customer's
     employee or agent who signed the relevant purchase order. At a minimum,
     each purchase order shall specify the following items:

     a)  A complete list of the Products and Services covered by the purchase
     order, specifying the quantity, part number and description of each;

     b)  The price of each Product and Service shall be as set forth on the
     attached price list and subject to the terms of this Agreement, after any
     applicable discounts (including any discount due Customer by virtue of
     Section 2.6), and any additional charges and costs made in accordance with
     the terms of this Agreement;

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/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                    Page 5 of 37
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     c)  The billing address, the destination to which the Products will be
     delivered, and the requested shipment date; and

     d)  The signature of Customer's employee or agent who possesses the
     authority to place such an order.

     Avici shall not be obligated to accept any order in which Customer fails to
     include the items in "a" through "d", above.  However, if such order is
     accepted, such failure shall not cause Customer, not to receive the
     applicable discount for such order.  Should all of the items in "a" through
     "d" be included in the order and if the requested shipment date is (or, in
     the event of multiple shipment dates, all requested shipment dates under
     the order) at least [CONFIDENTIAL TREATMENT REQUESTED]/*/ from the date of
     such order, including the requested shipment date or dates, Avici shall
     accept such order, subject to the other terms and conditions of this
     Agreement. It is understood that Customer shall be entitled to purchase
     Product consisting of those configurations available from Avici upon the
     date such purchase order, it shall promptly advise Customer in writing to
     that effect.

3.2  NON-VARIANCE.  No purchase order, acknowledgment form, invoice or other
     ordering document or communications for either party shall vary the terms
     and conditions of this Agreement unless both parties expressly so agree in
     writing.  In the event of any conflict between the terms and conditions of
     this Agreement and those of any purchase order, acknowledgment form,
     invoice or other ordering document or communication, the terms and
     conditions of this Agreement shall prevail.

3.3  SHIPPING.  Avici shall ship the Products on the shipment date agreed to by
     Avici in its acceptance of the purchase order.  All items ordered by
     Customer under this Agreement will be suitably packed for shipment in
     Avici's standard containers, marked for shipment to the designated address
     or addresses specified by Customer in Customer's purchase older, and
     delivered to a carrier or forwarding agent chosen by Customer.  If Customer
     fails to designate a carrier, forwarding agent or type of conveyance, Avici
     will make this designation in conformance with its standard shipping
     practices. Delivery will be F.O.B Avici's facility ("Delivery Point"),
     [CONFIDENTIAL TREATMENT REQUESTED]/*/ All freight, insurance and other
     shipping expenses from Delivery Point to the destination specified by
     Customer as well as any expenses related to Customer's special packing
     requests, will be borne by Customer. [CONFIDENTIAL TREATMENT REQUESTED]/*/

3.4  DELAY AND CANCELLATION OF ORDERS.  Partial shipments shall only be made
     with Customer's previous written approval, which shall not be unreasonably
     withheld. If shipment of an order is delayed more than [CONFIDENTIAL
     TREATMENT REQUESTED]/*/ but less than [CONFIDENTIAL TREATMENT REQUESTED]/*/
     beyond the agreed shipment date, then Customer shall receive [CONFIDENTIAL
     TREATMENT REQUESTED]/*/ of the order or the delayed portion if a partial
     shipment is allowed by Customer. If shipment of an order is delayed more
     than [CONFIDENTIAL TREATMENT REQUESTED]/*/ but less than [CONFIDENTIAL
     TREATMENT REQUESTED]/*/ beyond the scheduled shipment date, then Customer
     shall receive [CONFIDENTIAL TREATMENT REQUESTED]/*/ of the order or the
     delayed portion if a partial shipment is allowed by

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/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                    Page 6 of 37
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     Customer. The amount of the purchase commitments set forth in Sections
     2.1 and 2.2 shall be [CONFIDENTIAL TREATMENT REQUESTED]/*/. If shipment is
     delayed more than [CONFIDENTIAL TREATMENT REQUESTED]/*/ from the
     mutually agreed upon shipment date due solely to causes in Avici's
     reasonable control, then Customer, at its election, may either receive a
     [CONFIDENTIAL TREATMENT REQUESTED]/*/ on the order or cancel the affected
     order upon written notice provided such cancellation notice is delivered to
     Avici prior to shipment. In the event Customer exercises its right to
     cancel a purchase order, Customer's purchase commitments under Sections 2.1
     and 2.,2 of this Agreement shall be [CONFIDENTIAL TREATMENT REQUESTED]/*/.

3.5  RECONFIGURATION, RESCHEDULING AND CANCELLATION OF ORDERS.

     a) Upon written notice to Avici provided at least [CONFIDENTIAL TREATMENT
     REQUESTED]/*/ prior to the scheduled ship date, Customer may
     reconfigure any purchase order or reschedule the delivery of any Products
     scheduled for shipment by up to [CONFIDENTIAL TREATMENT REQUESTED]/*/ at no
     Charge. Acceptance of Customer's request to reconfigure or reschedule any
     delivery with less than such [CONFIDENTIAL TREATMENT REQUESTED]/*/ prior
     written notice to Avici shall be at the sole discretion of Avici; provided
     that, Avici shall use commercially reasonable efforts to accommodate any
     request by Customer to reschedule or reconfigure upon less than such
     [CONFIDENTIAL TREATMENT REQUESTED]/*/ notice.

     b) Upon at least [CONFIDENTIAL TREATMENT REQUESTED]/*/ written notice to
     Avici prior to the originally scheduled shipment date of Products ordered
     pursuant to written, accepted purchase orders under this Agreement,
     Customer may cancel any shipment date of the Products without charge. The
     following cancellation charges shall apply to any cancellations made by
     Customer less than [CONFIDENTIAL TREATMENT REQUESTED]/*/ prior to accepted
     shipment date as liquidated damages and not as a penalty and shall
     constitute Avici's exclusive remedy for cancellation and is based on the
     number of days prior to the accepted shipment date that written notice of
     cancellation is received by Avici:

               Days Notice        Charge
               -----------        ------
                                ($ of canceled order)
               [CONFIDENTIAL TREATMENT REQUESTED]/*/

     However, the amount of any purchase order cancelled under this Section 3.5
     shall not reduce Customer's obligations in Sections 2.1 (Purchases) and 2.2
     (Purchase Timing) of this Agreement.

3.6  INSTALLATION.  If requested by Customer, Avici will install the Products
     and/or Software, or any portion requested, at Customer's facilities at
     [CONFIDENTIAL TREATMENT REQUESTED]/*/ for such

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

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<PAGE>

     services. All charges for installation shall be applied against Customer's
     procurement obligations under Sections 2.1 and 2.2 of this Agreement.

3.7  PRODUCT CHANGES.  Avici may, at any time, make changes in, or substitutions
     to, the Product, any component thereof or any Software provided the changes
     (i) are made for safety purposes or (ii) do not impact upon form, fit,
     function features, use or performance of such items in a manner which
     results in material changes to Customer's operations procedures or
     negatively impact Customer's network operations.  With respect to changes
     in, or substitutions to, the Product, components thereof or any Software
     which does impact upon the form, fit, function features, use or performance
     of such items in manner which results in material changes to Customer's
     operations procedures or negatively impact Customer's network operations,
     Avici will notify Customer in writing [CONFIDENTIAL TREATMENT
     REQUESTED]/*/prior to the effective date of such change or substitution of
     its intent to make the change or substitution. In the event any such change
     or substitution is not desired by Customer, Customer will so notify Avici
     within [CONFIDENTIAL TREATMENT REQUESTED]/*/ from the date of the notice of
     the proposed change or substitution, however, Avici will continue to make
     available to Customer for a period of [CONFIDENTIAL TREATMENT REQUESTED]/*/
     from the effective date of Avici's substitution or change and at the price
     being charged at the time of such notice, the Product, component thereof or
     Software which is subjcct to change or substitution. Provided however, if
     Avici must make changes in, or substitutions to, the Product, components
     thereof or any Software which does impact upon the form, fit, function
     features, use or performance of such items in a manner which results in
     material changes to Customer's operations procedures or negatively impact
     Customer's network operations, which changes or substitutions are unplanned
     or unanticipated by Avici ("Exceptional Changes"), Avici will notify
     Customer in writing [CONFIDENTIAL TREATMENT REQUESTED]/*/ prior to the
     effective date of such Exceptional Change. In the event any such
     Exceptional Change is not desired by Customer, Customer will so notify
     Avici within [CONFIDENTIAL TREATMENT REQUESTED]/*/ from the date of the
     notice of the proposed Exceptional Change, however, Avici will continue to
     make available to Customer for a period of [CONFIDENTIAL TREATMENT
     REQUESTED]/*/ from the effective date of Avici's Exceptional Change and at
     the price being charged at the time of notice of the Exceptional Change,
     the Product, component thereof or Software which is subject to the
     Exceptional Change.

3.8  PRODUCT SUPPORT AND UNLICENSED SPARE. For a period of [CONFIDENTIAL
     TREATMENT REQUESTED]/*/ from the date of shipment ("Supported Period"),
     Avici will continue to make available for purchase by Customer repair/spare
     parts for Avici Products and shall provide maintenance and technical
     support services at the then current price for all Products and Software
     furnished pursuant to this Agreement. Customer may purchase a single
     Product which will be shipped without a software license for the purpose of
     maintaining such Product as a spare. When Customer utilizes the spare
     Product to effect a replacement of a non-functioning Product, Customer will
     issue a purchase order to license the Software for such spare at the then
     current price.

3.9  PRODUCT DISCONTINUANCE.  (a) Subject to Avici's obligations under Section
     3.8, Avici may discontinue sale of the Product, component thereof or
     Software if Avici gives Customer at least [CONFIDENTIAL TREATMENT
     REQUESTED]/*/ notice thereof; provided, however, that Avici agrees not to

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                    Page 8 of 37
<PAGE>

     discontinue sale of any such item until the earlier of (i) the date
     Customer satisfies its purchase obligation under this Agreement, or (ii)
     the expiration of the term of this Agreement. In the event of any such
     discontinuation of the Product, component thereof or Software, Avici will
     provide Customer with a suggested replacement produced by Avici and which
     would be available for the remainder of the term of this Agreement.
     Customer will have the right to substitute the replacement item for the
     discontinued Product, component thereof or Software under this Agreement,
     at the then Current list price then being charged other customers by Avici
     [CONFIDENTIAL TREATMENT REQUESTED]/*/. If Customer elects not to use the
     suggested replacement item, Avici will offer Customer a [CONFIDENTIAL
     TREATMENT REQUESTED]/*/ period beginning the day of the notice of
     discontinuance within which Customer can place orders for the discontinued
     item. Customer may give a last order ("One Time Buy Order") immediately
     prior to the end of the [CONFIDENTIAL TREATMENT REQUESTED]/*/ period. All
     purchases made under the preceding two sentences shall be at the prices
     which Customer was paying for the discontinued item immediately prior to
     the notice of discontinuance. The One-Time Buy Order is non-cancelable,
     non-reschedulable and non-returnable. Items ordered with the One-Time Buy
     Order will be delivered to Customer as requested by Customer but no later
     than [CONFIDENTIAL TREATMENT REQUESTED]/*/ after the notice of
     discontinuance.

     [CONFIDENTIAL TREATMENT REQUESTED]/*/

3.10 FORECASTS. No later than [CONFIDENTIAL TREATMENT REQUESTED]/*/, Customer
     shall provide Avici with a forecast setting forth the Customer's estimated
     [CONFIDENTIAL TREATMENT REQUESTED]/*/ requirements for Products for the
     [CONFIDENTIAL TREATMENT REQUESTED]/*/, Customer shall provide Avici with a
     forecast setting forth the Customer's estimated [CONFIDENTIAL TREATMENT
     REQUESTED]/*/ requirements for Products for the [CONFIDENTIAL TREATMENT
     REQUESTED]/*/. After [CONFIDENTIAL TREATMENT REQUESTED]/*/, Customer shall,
     no later than [CONFIDENTIAL TREATMENT REQUESTED]/*/ prior to the beginning
     of each [CONFIDENTIAL TREATMENT REQUESTED]/*/, provide Avici with a
     [CONFIDENTIAL TREATMENT REQUESTED]/*/ rolling forecast, updated
     [CONFIDENTIAL TREATMENT REQUESTED]/*/, setting forth the Customer's
     estimated [CONFIDENTIAL TREATMENT REQUESTED]/*/ requirements for Products.
     All forecasts supplied by Customer hereunder shall be non-binding as to all
     amounts forecasted.

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                    Page 9 of 37
<PAGE>

3.11 EXPORT OF PRODUCTS.  As to all shipments with destinations outside of the
     US, Avici and Customer shall comply with all applicable export and import
     regulations and Customer shall provide such documentation and assistance
     reasonably necessary to ensure US export control compliance.  For shipment
     other than in the US, Customer will bc solely responsible for (i) obtaining
     any license that may be required to import the Products into its country
     (ii) clearing the Products thought local customers upon their arrival to
     Customer Country and (iii) paying all customs duties, taxes and other
     charges assessed on such importation's in such country.

3.12 US GOVERNMENT RESTRICTED RIGHTS.  Notice - distribution and use of
     products including computer programs and any related documentation and
     derivative works thereof, to and by the United States Government, are
     subject to the Restricted Rights provisions of FAR 52.227.19, paragraph
     (c)(2) as applicable, except for purchases by agencies of the Department of
     Defense (DOD).  If the Software is acquired under the terms of a Department
     of Defense or civilian agency contract, the Software is "commercial item"
     as that term is defined at 48 C.F. R. 2.101 (Oct. 1995), consisting of
     "commercial computer software" and "commercial computer software
     documentation" as such terms are used in 48 C.F.R 12.212 of the Federal
     Acquisition Regulations and its successors and 48 C.F.R 227.7202-1 through
     22.7202-4 (June 1995) of the DOD FAR Supplement and its successors.  All
     U.S. Government end users acquire the Software with only those rights set
     forth in this Agreement.  Manufacturer is Avici Systems, Inc., North
     Billerica, MA 01862.  Unpublished - lights reserved under the copyright
     laws of United States.

3.13 RESALE.  Products purchased under this Agreement may be resold and the
     related Software subliccnsed by Customer to its own customers when such
     Product is included as part of a sale of a package of Customer's
     proprietary products with integrated value-added services such as
     installation (provided that any such installation is performed by all
     Avici-certified technician), training, consulting, integration, management
     and maintenance.  Customer is therefore authorized to distribute and
     sublicense the Products and Software, to the extent necessary to effect the
     transactions described in this Section 3.13, provided that, any agreement
     to sublicense is consistent with the rights and obligations set forth
     herein and includes terms and conditions no less restrictive than those
     contained in this Agreement.  Customer agrees that it will not delete or
     modify any markings, notices, etc. on Products or Software licensed from
     Avici.  Customer shall notify Avici of any such sublicense.

3.14 DOCUMENTATION.  Avici will supply Customer with one (1) hard copy of the
     Documentation for each unit of Product and/or any Software ordered and one
     (1) electronic or CD-ROM copy of the Documentation.  The foregoing
     obligation shall apply to all upgrades and releases purchased or made
     available by Avici to Customer after the Effective Date.  Customer shall
     have the right to copy the Documentation in its entirety, without
     alteration (including all copyright notices), and to distribute such copies
     internally, solely for use in connection with the operation and maintenance
     of the Product.  Avici owns and retains copyright in the Documentation.

4.0  TERM AND TERMINATION

                                                                   Page 10 of 37
<PAGE>

4.1  TERM.  This Agreement will commence on the Effective Date and remain in
     effect until December 31, 2001, unless earlier terminated pursuant to
     Sections 4.2, 4.3, 4.4, 4.5 or 15.5.  This Agreement shall automatically
     renew for consecutive, one-year terms, provided that either party shall
     have the light upon sixty (60) days prior written notice to the other to
     cancel this Agreement effective at the end of the initial term or any of
     the one-year renewals.  For purposes of clarity, Customer shall have no
     obligation to make any purchase during any renewal period.

4.2  TERMINATION.  In addition to Customer's rights to terminate this Agreement
     pursuant to Sections 4.3, 4.4, 4.5 and 15.5, either party may terminate
     this Agreement in the event of a default by the other, provided that the
     non-defaulting party so advises the defaulting party in writing of the
     event of alleged default and affords the defaulting party thirty (30) days
     within which to cure the default.  Default is defined to include:

     (a) Either party becomes insolvent, makes a general assignment for the
     benefit of creditors, files a voluntary petition in bankruptcy or an
     involuntary petition in bankruptcy is filed against such party which is not
     dismissed within sixty (60) days after the date such petition is filed, or
     suffers or permits the appointment of a receiver for its business, or its
     assets become subject to any proceeding under a bankruptcy or insolvency
     law, domestic or foreign, or has liquidated its business;

     (b) Either party's material breach of any of the terms or conditions
     hereof;

     (c) The execution by either party of an assignment for the benefit of
     creditors or any other transfer or assignment of similar nature.

4.3  FAILURE TO PASS TEST.  If the Test Unit fails to successfully perform the
     Test within the time period permitted under Subsection 2.3(a), then the
     Customer shall have the right to terminate this Agreement upon thirty (30)
     days written notice to Avici, Customer's right to terminate pursuant to
     this Section 4.3 must be exercised within one-hundred eighty (180) days
     from the end of the [CONFIDENTIAL TREATMENT REQUESTED]/*/ period described
     in 2.3(a)(iii).

4.4  NETWORK FAILURE.  If at any time after meeting its purchase obligation
     under Sections 2.1 and 2.2, the Customer's network or any significant span
     within such network, fails solely due to the failure of Avici's Product or
     Software to perform in accordance with the Specifications, to function
     properly for a period of [CONFIDENTIAL TREATMENT REQUESTED]/*/ after
     Customer provides notice to Avici as per clause 4.4(a), Customer shall have
     the right to terminate this Agreement upon [CONFIDENTIAL TREATMENT
     REQUESTED]/*/ written notice to Avici, provided that Avici (or an Avici
     certified equipment technician) performed Product installation and that
     Customer:

     (a) Notifies Avici with as much information (including at a minimum
     location) about the cause of the failure as is available at the time, in
     writing, within 24 hours of determining that a failure is attributable to
     Avici's Product or Software,

     (b) Immediately and continuously provides access to Customer facilities
     where Avici Product is located, subject to Customer's policies and
     procedures regarding access to its

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 11 of 37
<PAGE>

     facilities which are aimed at protecting Customer's proprietary information
     in, and the security of, such facilities,

     (c) Makes adequately trained and informed personnel available for
     consultation and assistance to Avici engineers, and

     (d) Allows Avici to repair or replace Product(s), Software or components of
     Product(s)

     Customer will not be entitled to terminate under this Section 4.4 if the
     alleged failure is due to (i) unauthorized alteration of the Products or
     Software, (ii) mishandling, abuse to, or improper storage of the Products
     or Software, (iii) installation by other than Avici or an Avici-certified
     equipment technician (except as per Section 8.6), (iv) service or
     maintenance other than by Avici or Avici-certified equipment technician
     (except as per Section 8.6), (v) misuse, including, without limitation, any
     use of the Product beyond the environmental parameters set forth in the
     applicable Specifications, (vi) damage by fire, explosion, power failure,
     power surge or other power irregularity (beyond such parameters which are
     set forth in the applicable Specifications), or (vii) any repair or
     modifications or attempted repair or modifications of the Product made
     other than by Avici or an Avici-certified authorized equipment technician
     (except as per Section 8.6).

4.5  "CHRONIC LATE SHIPMENT".  If at any time after meeting its purchase
     obligation under Sections 2.1 and 2.2, Customer may upon [CONFIDENTIAL
     TREATMENT REQUESTED]/*/ written notice to Avici, terminate this Agreement
     and any outstanding purchase order, in whole or in part, in the event of
     "Chronic Late Shipment" by Avici that is not cured by Avici within
     [CONFIDENTIAL TREATMENT REQUESTED]/*/ after notice Of Such problem by
     Customer. "Chronic Late Shipment" is defined as Avici's late shipment
     during any consecutive [CONFIDENTIAL TREATMENT REQUESTED]/*/ period of
     [CONFIDENTIAL TREATMENT REQUESTED]/*/ or more of the Products and/or
     Software for which Customer has submitted a purchase order.

4.6  SURVIVAL OF RIGHTS.  Neither the termination or expiration of this
     Agreement shall relieve either party from any obligations to pay the other
     party any amounts accrued under this Agreement prior to such termination or
     expiration.  Expiration or termination of this Agreement shall not relieve
     either party of liability for damages or any other rights or remedies that
     either party may have under this Agreement or at law or in equity or
     relieve either party from the duty to hold in confidence proprietary
     information and otherwise comply with, and exercise the rights set forth
     in, Articles or Articles 5.0. 6.0, 7.0, 8.0, 9.0, 10.0, 11.0 13.0 and
     Sections 4.6 and 14.1 hereof, each of which will survive termination or
     expiration of this Agreement.  Customer's obligation to meet the purchase
     obligations under Sections 2.1 and 2.2 will survive the expiration of this
     Agreement or the termination of this Agreement by Avici for cause pursuant
     to Section 4.2.  Notwithstanding anything in this Agreement to the
     contrary, Customer shall in no event have any obligation to make the
     minimum purchase obligations set forth in Sections 2.1 and 2.2 or any
     portion thereof in the event of termination by Customer pursuant to either
     Sections 4.2 or 4.3. In the event of termination of this Agreement by Avici
     pursuant to Section 4.2, Avici's obligations under existing but uncompleted
     purchase orders will

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 12 of 37
<PAGE>

     immediately cease. In the event of expiration of this Agreement or in the
     event of termination of this Agreement by Customer pursuant to either
     Sections 4.2, 4.3, 4.4, 4.5, or 15.5, Customer, at its option, upon ten
     (10) days written notice to Avici, may elect to terminate its obligations
     under all or any purchase orders issucd by Customer prior to the effective
     date of such expiration of termination by Customer, but not yet fully
     performed by Avici as of the date of such expiration or termination by
     Customer; provided to the extent the Customer elects not to terminate
     Avici's obligations under such existing purchase orders, Avici's
     obligations under such purchase orders shall survive such termination or
     expiration.

5.0  TRAINING MAINTENANCE AND SUPPORT

     Avici agrees to provide Customer training, support and maintenance with
     respect to the Product and Software with the terms and conditions upon
     which such training, support and maintenance will be provided to be set
     forth in a separate "Maintenance, Support and Training Agreement" which
     shall be mutually agreed between the parties and executed within thirty
     (30) days from the Effective Date.  Although a Maintenance, Support and
     Training Agreement is to be subsequently negotiated, this Agreement and its
     continuing effectiveness is not conditional upon the execution of the
     Maintenance, Support and Training Agreement.

6.0  SOFTWARE LICENSE

6.1  GRANT OF LICENSE.  Subject to payment of the applicable license fees, if
     any, set forth in this Agreement, Avici hereby grants to Customer a
     perpetual, nontransferable (except is otherwise provided in this
     Agreement), and nonexclusive license (or, with respect to the Third Party
     Software, a sublicense) to use the Software and its related Documentation
     provided pursuant to the terms of this Agreement.  The license (or
     sublicense in the case of Third Party Software) grants Customer no right
     to, and Customer will not, further sublicense such Software (except to the
     extent otherwise provided herein), or modify, decompile, or disassemble
     Software furnished to generate corresponding source code.  Customer and its
     customers will be entitled to modify only the user-selectable features of
     the Software.  With respect to any Third Party Software, in addition to the
     terms and conditions herein, Customer will abide by the applicable terms
     and conditions for such Third Party Software.  Attachment C lists the Third
     Party Software licenses that are applicable as of the Effective Date and
     contains the terms of such Third Party Software licenses.

6.2  CONFIDENTIALITY.  All Software (whether or not part of firmware) and its
     related Documentation furnished by Avici, and all copies thereof made by
     Customer, including translations, compilations, and partial copies, are and
     will remain the exclusive property of Avici and its licensors.  Customer
     will hold such Software and related Documentation in strict confidence, and
     will not, without Avici' prior written consent, disclose, provide, provide
     access to, or otherwise make available, in whole or in part, any Software
     or related Documentation to anyone, except to Customer's employees, agents
     and subcontractors having a need-to-know for purposes of operating or
     maintaining the

                                                                   Page 13 of 37
<PAGE>

     related Product, or to its customers to the extent necessary to permit them
     to utilize user-selectable features in accordance with the applicable
     Documentation. Any disclosures made under this Section 6.2 to agents,
     subcontractors or customers of Customer shall be made Subject to
     confidentiality agreements between Customer and such subcontractors, agents
     or customers. Customer will protect the Documentation from unauthorized use
     or disclosure by exercising the same degree of care that it uses with
     respect to information of its own of a similar nature, but in no event less
     than reasonable care.

6.3  COPIES.  Customer will not make any copies of any Software or related
     Documentation except as necessary for archival purposes in accordance with
     Customer's customary practices.  In addition, Customer shall have the right
     to keep a copy of the Software on a backup system and use such copy in the
     event of an emergency situation without paying any additional license fees.
     Customer agrees not to use such copy on the backup system unless an
     emergency situation prevents the original licensed Software from being used
     by Customer.  Customer will reproduce and include any Avici copyright and
     proprietary notice on all copies of the Software and its related
     Documentation produced by Customer.  Customer will take appropriate action,
     by instruction, agreement, or, otherwise, with the persons permitted access
     to the Software and related Documentation to enable Customer to satisfy its
     obligations under this Agreement.  When the Software and related
     Documentation are no longer needed by Customer, or if Customer's license is
     canceled or terminated, Customer will return ill copies of such Software
     and related Documentation to Avici or follow written disposition
     instructions provided by Avici at that time, if any.

6.4  UPDATES.  The fees specified in this Agreement are for only the Software
     increase current as of the Effective Date.  Other Version Releases and
     Incremental Releases in may require additional fees to be paid by Customer
     and be subject to additional terms.  Releases, if any, will be issued by
     Avici in its sole discretion and designated in the following manner:
     Version Releases, by a change in the digit(s) to the left of the decimal
     point in the Product version number [(x).x.x] and, Incremental Releases, by
     a change in the tenths digit [x.(x).x].  During the term of this Agreement,
     Avici will provide to Customer any Updates that it makes generally
     commercially available at no additional charge.  For purposes of this
     Agreement, "Updates" means modifications, addition or routines intended to
     correct the practical adverse effect of a Software error.  Updates will be
     designated by a change in the digit(s) to the right of the tenths digit(s)
     [x.x.(x)].  The foregoing is based upon Avici's current nomenclature for
     identifying modifications and changes to software and should the
     nomenclature change the rights of Customer under this Section 6.4 shall be
     applied accordingly.

7.0  CONFIDENTIAL INFORMATION

7.1  CONFIDENTIAL INFORMATION.  As used herein, "Confidential Information" means
     and includes trade secrets and other proprietary or confidential
     information, including but not limited to, products, planned products,
     services or planned services, the identity of or information concerning,
     customers or prospective customers, data, financial information, computer
     software, processes, methods, knowledge, inventions, ideas, marketing
     promotions, discoveries, current or planned activities, research
     development of other

                                                                   Page 14 of 37
<PAGE>

     information relating to a party's business activities or operations or
     those of its customers or subcontractors, whether or not marked
     "confidential". The Confidential Information shall be deemed the property
     of the Disclosing Party (as defined below).

7.2  NON-DISCLOSURE.  This Agreement creates a confidential relationship between
     Customer and Avici and, in the course of negotiating or performing this
     Agreement a party may disclose ("Disclosing Party") Confidential
     Information to the other party ("Receiving Party").  The Receiving Party
     will keep Confidential Information confidential and, except as directed or
     authorized in writing, will use Confidential Information only in
     conjunction with the provision, use, maintenance or operation of the
     Products and/or Service provided under this Agreement and will not disclose
     to any person or, entity, directly or indirectly, in whole or in part, any
     Confidential Information, or information derived from Confidential
     Information.  Notwithstanding the foregoing, the Confidential Information
     may be disclosed to the officers, directors, employees and affiliates of
     the Receiving Party who have a legitimate need to know and solely for the
     purpose of the performance of duties hereunder.  Upon termination of this
     Agreement, the Receiving Party will, at the Disclosing Party's option,
     return to the Disclosing Party, or destroy and certify to the Disclosing
     Party such destruction, all documents, papers and other materials in its
     control that contain or relate to Confidential Information.  To the extent
     practicable all Confidential Information disclosed to the Receiving Party
     will be promptly identified as such by the Disclosing Party in writing.
     The Receiving Party will protect the Confidential Information from
     unauthorized use or disclosure by exercising the same degree of care that
     it uses with respect to information of its own of a similar nature, but in
     no event less than reasonable care.

7.3  EXCEPTIONS TO RESTRICTIONS.  Notwithstanding anything to the contrary
     contained herein, "Confidential Information" will not include any
     information Receiving Party can demonstrate:  (a) is generally known to the
     public on the date of disclosure of same outcomes generally known to the
     public after such date through no breach of this Agreement or any other
     obligation of confidentiality; (b) was known by the Receiving Party at the
     time of disclosure without any obligation to hold it in confidence; (c) is
     received by the Receiving Party after the date of disclosure from a third
     party without breach of any obligation of confidentiality and without any
     obligation of confidentiality binding upon the Receiving Party; (d) is
     independently developed by the Receiving Party after the date of disclosure
     without use of, or reference to, the Confidential Information of the
     disclosing Party; (e) is approved for release by written authorization of
     the Disclosing Party, but only to the extent of, and subject to, such
     conditions as may be imposed in such written authorization; (f) is required
     by law, rule or regulation, including requirements of the applicable
     securities exchanges, to be disclosed, but only to the extent and for the
     purposes of such required disclosure and subject to Section 7.4, or (g) is
     disclosed in response to a valid order of a court or other governmental
     body, but only to the extent of and for the purposes of such order and
     subject to Section 7.4.

7.4.  NOTICE OF REQUIRED DISCLOSURE.  If a Receiving Party is or may be required
     under 7.3(f) or (g) to disclose any Confidential Information of a
     Disclosing Party, the Receiving Party:  (a) will provide to the Disclosing
     Party immediate notice of the possible

                                                                   Page 15 of 37
<PAGE>

     disclosure, and (b) will permit the Disclosing Party, at Disclosing Party's
     expense, to take all reasonable actions to eliminate the requirement of
     such disclosure, to limit the scope of same and to obtain protective orders
     to protect the confidentiality of such Confidential Information, including,
     without limitation, filing motions and otherwise making appearances before
     a court.

7.5  SURVIVAL OF PROVISIONS.  The provisions of this Article 7 will survive any
     termination or expiration of this Agreement indefinitely with regard to
     information which constitutes a trade secret of the Disclosing Party and
     for a period of [CONFIDENTIAL TREATMENT REQUESTED]/*/ with regard to all
     other Confidential Information.

8.0  PRODUCT AND SOFTWARE WARRANTIES.

8.1  PRODUCT WARRANTY.  Avici hereby warrants that all Product hardware,
     Software and documentation media provided under this Agreement shall
     conform to the functionality described in the Specifications and the
     Documentation in effect as of the date of shipment and shall be free from
     defects in material and workmanship for a period of [CONFIDENTIAL TREATMENT
     REQUESTED]/*/ following delivery (the "Warranty Period"). Provided,
     however, that Software is not warranted to be error free.

8.2.  WARRANTY CLAIMS.  Customer must notify Avici's Technical Assistance
     Center, ("`TAC") of a suspected defect in the Product or Software.  After
     receiving such notice, TAC will notify Customer of its designation of one
     of the two problem resolution methods set out below in 8.2.1 or 8.2.2.
     Avici shall incur no liability under this warranty if Customer fails to
     provide Avici with notice of the alleged defect during the applicable
     Warranty Period.

     8.2.1  RETURN TO FACTORY:  If TAC selects the "Return to Factory" problem
          resolution method, then the allegedly defective hardware, must be
          returned to Avici in accordance with Avici's Return to Factory repair
          procedures, as follows:

          (a) During the Warranty Period.  Avici shall, at its cost, ship
          repaired items or replacements for defective hardware covered under
          warranty within [CONFIDENTIAL TREATMENT REQUESTED]/*/ of receipt
          of the hardware.

          (b) Return Material Authorization ("RMA") numbers are issued to
          utilize returns and ensure proper treatment of the equipment in
          shipping, diagnosis, repair and/or replacement.  An RMA number may be
          obtained by calling the Avici Technical Assistance Center (TAC) at
          (978) 964-2000 during normal business hours, or via email to
          support@avici.com. All returns should be shipped

          to:

          RMA Depot,
          Avici Systeins Inc,,
          101 Billerica Avenue,
          North Billerica, MA 01862

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 16 of 37
<PAGE>

          The following information should accompany the return equipment:

          Detailed information about the defect.
          Model and Serial Numbers.
          Hosting TSR Bay Model and Serial Number, where applicable.  Ship to
          address for return repaired/replaced equipment.
          Contact name, phone, mobile and fax number and email address.

          When the RMA is issued, the TAC representative will provide a
          preferred carrier account number and priority shipping instructions.

          (c) Hardware which is defective upon arrival at Customer's specified
          destination address shall be referred to as a "DOA Part".  Within
          [CONFIDENTIAL TREATMENT REQUESTED]/*/ of notification by Customer that
          it has received a DOA Part, Avici shall ship a replacement to
          Customer. Customer, in such event, must return the DOA Part to the
          freight carrier for shipment to Avici within [CONFIDENTIAL TREATMENT
          REQUESTED]/*/ of receipt of the replacement hardware. If the DOA Part
          is not returned within this time period, Avici will bill the Customer
          for the replacement hardware at list price, [CONFIDENTIAL TREATMENT
          REQUESTED]/*/.

     8.2.2  OTHER: TAC will return Software to functionality in conformance with
            the relevant Specifications and Documentation per the table in
            8.3.1. Such efforts shall include analysis, repair, correction or
            workaround of the problem by means of telephone support, or, if
            appropriate, onsite support, including patches, corrective software
            releases or other means reasonably determined by Avici. Software
            maintenance releases will be available under this warranty. Software
            images and Management Information Bases ("MIB's") will be
            downloadable from the Avici web site, or upon request by Customer,
            physical media will bc shipped with relevant images, MIBS, release
            notes and full user documentation. Such upgrades shall be governed
            by the same license terms pursuant to which the original version of
            the Software was licensed.

       8.3  THE AVICI TAC PROCESS. In addition to the obligations under 8.1 and
            8.2, Avici shall make available telephone and email warranty
            services support engineers for [CONFIDENTIAL TREATMENT REQUESTED]/*/
            calls during normal business hours (8 am to 5 pm Eastern Time).
            Support includes answering questions, trouble shooting and
            identifying problems, and developing solutions and workarounds.

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 17 of 37
<PAGE>

     8.3.1  Responses to Customer calls will be based on problem severity.  The
     following service levels apply according to the severity classification:

<TABLE>
<CAPTION>
Severity                   Description                     Escalation Procedure/Response Time
-------------------------------------------------------------------------------------------------
<C>          <S>                                       <C>
          1  Critical - Customer is experiencing a     Avici's VP's of Engineering and Customer
             network outage that prevents their        Service will be [CONFIDENTIAL TREATMENT
             customers from accessing service and      REQUESTED]/*/ notified. Avici's personnel
             for which there is no workaround or       will update Customer at least [CONFIDENTIAL
             recovery action possible.                 TREATMENT REQUESTED]/*/ and will work on the
                                                       problem until completion.
-------------------------------------------------------------------------------------------------
          2  Major - Customer is experiencing a        Avici's Level 3 personnel will resolve
             problem that affects service but for      the problem within [CONFIDENTIAL TREATMENT
             which there is a work-around or           REQUESTED]/*/ or escalate to Development
             recovery action.  Business can continue   Engineering.  Avici's personnel will update
             although performance may be degraded.     Customer at least every [CONFIDENTIAL TREATMENT
                                                       REQUESTED]/*/.
-------------------------------------------------------------------------------------------------
          3  Minor - Customer is experiencing          Severity 3 problems will be resolved by
             problems and requires technical advice    Avici within [CONFIDENTIAL TREATMENT
             or recommendation for the best            REQUESTED]/*/or escalate to Development
             solution.  Severity 3 problems have a     Engineering.  Avici will work during normal
             reliable workaround and have, at most,    business hours to resolve these Severity 3
             a slight impact on the operational        problems and will contact Customer after
             environment.                              [CONFIDENTIAL TREATMENT REQUESTED]/*/ to report
                                                       on progress.
-------------------------------------------------------------------------------------------------
          4  Questions                                 Questions received by the TAC will be
                                                       logged and answered within [CONFIDENTIAL
                                                       TREATMENT REQUESTED]/*/.
-------------------------------------------------------------------------------------------------
</TABLE>

     8.3.2  At Avici's sole discretion, a technical expert may be dispatched to
            the affected site to better understand and resolve the problem.  For
            Critical Problems dispatch will be within [CONFIDENTIAL TREATMENT
            REQUESTED]/*/ of the call, Major Problems within the [CONFIDENTIAL
            TREATMENT REQUESTED]/*/.

     8.3.3  At Avici's sole discretion, it may escalate the problem for
            resolution through Support, Engineering and Sales Management, in
            accordance with the following matrix:

                                ESCALATION TREE

<TABLE>
<CAPTION>
AVICI STAFF/ORGANIZATION                          CRITICAL          MAJOR             MINOR
---------------------------------------------------------------------------------------------------
<S>                                           <C>
CSE Engineer                                    [CONFIDENTIAL TREATMENT REQUESTED]/*/
---------------------------------------------------------------------------------------------------
CSE Consulting Engineer                         [CONFIDENTIAL TREATMENT REQUESTED]/*/
---------------------------------------------------------------------------------------------------

Dir. Cust Svc & Dir Continuing Eng.             [CONFIDENTIAL TREATMENT REQUESTED]/*/
VP Sales & VP Eng                               [CONFIDENTIAL TREATMENT REQUESTED]/*/
===================================================================================================
</TABLE>

8.4  WARRANTY OF REPAIR OR REPLACEMENT PARTS. Avici warrants that repair or
     replacement hardware, and any Software upgrades, provided pursuant to this
     Agreement, under normal use and service, will be free from defective
     material and faulty workmanship and will perform in accordance with the
     functionality described in the Specifications and the Documentation for a
     period of [CONFIDENTIAL TREATMENT REQUESTED]/*/ from date of delivery, or
     the remainder of the Original Warranty Period, whichever is greater.

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 18 of 37
<PAGE>

8.5  WARRANTY OF SERVICES. Avici warrants that all Services performed under this
     Agreement shall be performed in a workmanlike manner in accordance with the
     standards of the industry. If any Services fail to meet the standard in the
     foregoing sentence and Customer notifies Avici of such failure within a
     reasonable time of discovery of such failure, but in no event later than
     [CONFIDENTIAL TREATMENT REQUESTED]/*/ from the completion of such Services,
     Avici shall, at its cost reperform the Services. Any Services which are
     reperformed, pursuant to this Section 8.5, shall be warranted for a period
     of [CONFIDENTIAL TREATMENT REQUESTED]/*/ from the date of the re-
     performance, or the remainder of the original warranty term, whichever is
     greater.

8.6  Avici shall incur no liability under this warranty if the alleged defect
     arises from (i) mishandling, abuse, improper storage (ii) installation,
     service or maintenance other than by Avici or an Avici-certified Customer
     service provided; (iii) misuse, including, without limitation, any use of
     the Product beyond the environmental parameters set forth in the applicable
     Specifications; (iv) damage by fire, explosion, power failure, power surge
     or other power irregularity (beyond such parameters which are set forth in
     the applicable Specifications), or (v) if any repair or modifications or
     attempted repair or modifications of the Product is made other than by
     Avici or all Avici-certified Customer service provider. Under the Return to
     Factory alternative, if a Product is determined to have a defect due to any
     of the causes set out above, Avici's then current repair price as listed in
     the price list will apply. Routine insertion or removal of hardware may be
     performed by non-Avici certified individuals provided that Such Insertion
     or removal is otherwise subject to the terms of this Section 8.6.

8.7  Avici warrants, except as stated in Avici's Documentation or
     Specifications, or as otherwise agreed, that no Software provided to
     Customer by Avici, shall, as of the date of shipment, (a) contain no hidden
     files; (b) not replicate, transmit, or activate itself without control of a
     person operating computing equipment on which it resides; (c) not alter,
     damage, or erase any data or computer programs without control of a person
     operating the computing equipment on which it resides; and (d) contain no
     encrypted embedded key unknown to Customer, node lock, timeout or other
     function, whether implemented by electronic, mechanical or other means,
     which restricts or may restrict use of access to any programs or data
     developed under this Agreement, based on residency on a specific hardware
     configuration, frequency of duration of use, or other limiting criteria.

8.8  Avici warrants that the Products and Software delivered to Customer are new
     (except for repaired or replacement hardware) and are free and clear of all
     liens and encumbrances.

8.9  EXCLUSIVE REMEDY.  Customer's sole and exclusive remedy for breach of the
     foregoing warranties, shall be limited to the express remedies set forth in
     this Article 8.

8.10 DISCLAIMER OF WARRANTIES.  AVICI MAKES NO OTHER WARRANTIES, EXPRESS,
     IMPLIED OR STATUTORY, OTHER THAN AS SET OUT IN THIS AGREEMENT.  ALL OTHER
     WARRANTIES AS TO THE QUALITY, CONDITION, MERCHANTABILITY, FITNESS FOR A
     PARTICULAR PURPOSE, OR NONINFRINGEMENT ARE EXPRESSLY DISCLAIMED.

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 19 of 37
<PAGE>

9.0  INTELLECTUAL PROPERTY CLAIMS

9.1  INDEMNIFICATION.  In the event of any claim, action, proceeding or suit by
     a third party against Customer alleging an infringement of any patent,
     copyright or trademark, or a violation or misappropriation of any trade
     secret by reason of the purchase, license or use of any Product or Software
     provided by Avici to Customer under this Agreement (other than Third Party
     Software unless the claim is based upon Customer's unauthorized use of the
     Third Party Software due to Avici not having the authority to Sublicense to
     Customer), Avici, at its expense, will defend, indemnify and hold harmless
     Customer, subject to the conditions and exceptions stated below from such
     claims, actions. proceedings or suits.  Avici will reimburse Customer for
     any reasonable cost, expense or attorneys' fees, which Customer is required
     to incur in cooperating with Avici, at Avici's request, in the defense or
     settlement of such action.  Avici will indemnify Customer against any
     liability assessed against Customer, including, among others, any final
     judgment on account of such action, proceeding or suit.

9.2  CUSTOMER ASSISTANCE.  Avici's obligation to indemnify Customer pursuant to
     this Article 9 is contingent upon (i) Customer giving Avici prompt written
     notice of all such claims, actions, proceedings or suits alleging
     infringement or violation, (ii) Customer tendering to Avici full and
     complete authority to assume the sole defense thereof, including appeals
     provided that Customer shall have the right to have counsel, at Customer's
     own expense, participate in such defense or appeal, and the sole right to
     settle same, provided that Customer has provided its prior written consent
     to such settlement, which consent shall not be unreasonably withheld, and
     (iii) Customer furnishing to Avici all relevant information available to
     Customer and cooperating with and assisting Avici in every reasonable way
     to facilitate the defense and/or settlement of any such claim, action,
     proceeding or suit.

9.3  NONINFRINGING USE.  If Customer's use of the Product or Software is
     enjoined or in Avici's opinion is likely to be enjoined, Avici will, at its
     expense and at its option, either (1) replace the enjoined Product or
     Software furnished pursuant to this Agreement with it suitable substitute
     free of any infringement, provided such substitute has comparible
     functionality and performance characteristics to the infringing items; (2)
     modify it so that it will be free of the infringement, provided such
     modification does not result in a material degradation in performance or
     functionality; or (3) procure for Customer a license or other right to use
     the infringing item.  If none of the foregoing options are available to
     Avici on a commercially reasonable basis, Avici will remove, or accept the
     return of, the enjoined Product or Software, and refund to Customer any
     amounts paid to Avici therefore.

9.4  AVICI RIGHT IN PROPERTY.  Except as expressly set forth in this Agreement,
     Avici grants no rights, title or interest in its intellectual property in
     the Products, Software or Documentation to Customer.

10.0 LIMITATION OF LIABILITY

                                                                   Page 20 of 37
<PAGE>

     Except for Avici's obligations under Articles 9.0 and 11.0, and to the
     extent not prohibited by applicable law:

     A.   Avici's liability to Customer under this Agreement will not exceed in
          the aggregate the total of all amounts paid to Avici by Customer under
          this Agreement provided that the foregoing limit shall be in addition
          to any amounts paid or expended by Avici in satisfying its obligations
          under Article 8.

     B.   Neither party shall be liable to the other for any indirect, punitive,
          special, incidental or consequential damage in connection with, or
          arising out of, this Agreement (including loss of business, revenue,
          profits, use, data or other economic advantage) however it arises,
          whether based on breach of contract or tort even if that party his
          been advised of the possibility of such damage.

11.0  INDEMNIFICATION

11.1  AVICI INDEMNIFICATION.  Avici will be responsible for and agrees to
     indemnify and hold harmless Customer from and against all losses,
     liabilities, demands, claims, actions, proceedings, suits and damages
     (including reasonable legal fees) for bodily injury, including death, to
     persons or damage to tangible property to the extent it results directly
     from tile willful misconduct or negligent acts of omissions, or strict
     liability, of Avici, its officers, agents, employees, or contractors.

11.2  CUSTOMER INDEMNIFICATION.  Customer will be responsible for and agrees to
     indemnify and hold harmless Avici from and against all losses, liabilities,
     demands, claims, actions, proceedings, suits and damages (including
     reasonable legal fees) for bodily injury, including death, to persons or
     damage to tangible property to the extent it results directly from the
     willful misconduct or negligent acts or omissions, or strict liability, of
     Customer, its officers, agents, employees or contractors.

11.3  OBLIGATIONS OF INDEMNIFIED PARTY.  With respect to each of Sections 11.1
     and 11.2 above, the indemnified party will give the indemnifying party
     prompt written notice of all such claims, actions, proceedings or suits.
     The indemnified party will, upon the indemnifying party's request and at
     the indemnifying party's expense, furnish all relevant information
     available to the indemnifying party and cooperate and assist the
     indemnifying party in every reasonable way to facilitate the defense and/or
     settlement of any such claim, action, proceeding or suit.

12.0  INSURANCE

12.1  COVERAGE.  Avici will carry or cause to be carried and maintained in force
     throughout the entire term of this contract insurance coverage's as
     described in paragraphs (A) through (D) below with insurance companies
     acceptable to Customer.  Avici will also require all subcontractors to
     maintain in force at all times during any subcontractor's performance of
     the Work the insurance coverage's set forth below.  The limits set forth
     below are minimum limits and will not be construed to limit Avici's
     liability.  All costs and deductible amounts will be for the sole account
     of Avici.

                                                                   Page 21 of 37
<PAGE>

     (a) Worker's Compensation insurance complying with the laws of the State or
     States having jurisdiction over each employee, whether or not Avici is
     required by such laws to maintain such insurance, and Employer's Liability
     with limits of [CONFIDENTIAL TREATMENT REQUESTED]/*/. If work is to be
     performed in Nevada, North Dakota, Ohio, Washington, Wyoming or West
     Virginia, Avici will participate in the appropriate state fund(s) to cover
     all eligible employees and provide a stop gap endorsement.

     (b) Commercial or Comprehensive General Liability insurance on an
     occurrence form with a combined single limit of [CONFIDENTIAL TREATMENT
     REQUESTED]/*/.

     (c) Automobile Liability insurance with a combined single limit of
     [CONFIDENTIAL TREATMENT REQUESTED]/*/.

     (d) Excess or Umbrella Liability insurance with a combined single limit of
     [CONFIDENTIAL TREATMENT REQUESTED]/*/.

12.2  WAIVERS.  In each of the above described policies, Avici agrees to waive
     and will require its insurers to waive any right of subrogation or recovery
     they may have against Customer, its parent, subsidiary, or affiliated
     companies.

12.3  ADDITIONAL INSUREDS.  Under the policies described in (B), (C) and (D)
     above, Customer, its parent, subsidiary and affiliated companies will be
     named as additional insureds as respects Avici's operations and as respects
     any work performed under this contract.  Any costs associated with naming
     these additional insureds is included in the contract cost.

12.4  OTHER INSURANCE.  The policies described in (B), (C) and (D) above will
     include the following "other insurance" amendment, "This insurance is
     primary insurance with respect to Customer, its parent, Subsidiary and
     affiliated companies, and any other insurance maintained by Customer, its
     parent, subsidiary or affiliated companies is excess and not contributory
     with this insurance."

12.5  NOTICE OF CANCELLATION.  Non-renewal or cancellation of policies described
     above will be effective only after written notices received by Customer
     from the insurance company [CONFIDENTIAL TREATMENT REQUESTED]/*/ in advance
     of any such non-renewal or cancellation. Prior to commencing the work
     hereunder, Contractor will deliver to Customer certificates of insurance on
     an Accord 25 or 25S form evidencing the existence of the insurance coverage
     required above.

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 22 of 37
<PAGE>

12.6  POLICY COPY.  In the event of a loss of claim arising out of or in
     connection with this contract, Contractor agrees, upon request of Customer,
     to submit the original or a certified copy of its insurance policies for
     inspection by Customer.

12.7  LIMITATIONS.  Customer will not insure nor be responsible for any loss or
     damage, regardless of cause, to property of any kind, including loss of use
     thereof, owned, leased or borrowed by Avici, or their employees, servants
     or agents.

13.0  REPRESENTATIONS AND WARRANTIES

13.1  MARKETABLE TITLE.  Avici warrants that it has good marketable title to the
     Products and that it has the full power and authority to grant the license
     (or sublicense, as applicable) granted Customer under or in connection with
     this Agreement with respect to the Software and that the license to, and
     use by, Customer of the Products and Software, as permitted under this
     Agreement, will not (or in the case of Third Party Software, to Avici's
     knowledge, will not) constitute art infringement or other violation of any
     copyright, patent, trade secret, trademark, non-disclosure, or any other
     intellectual property right of any third party.

13.2  GOOD STANDING.  Each party represents and warrants that it is duly
     organized, existing, and in good standing under the laws of its State of
     organization, and is duly qualified as a foreign corporation and in good
     standing in all jurisdictions in which the failure to so qualify would have
     a materially adverse impact upon its business and assets.

13.3  AUTHORITY.  Each party represents and warrants that it has the corporate
     power and requisite authority to execute, deliver and perform this
     Agreement, any Escrow Agreement, any Maintenance, Support and Training
     Agreement entered into pursuant to this Agreement, and all purchase orders
     to be executed pursuant to or in connection with this Agreement, and that
     it is duly authorized to, and has taken all corporate action necessary to
     authorize, the execution, delivery and performance of this Agreement and
     such other agreements and documents.

13.4  NON-CONFLICT.  Upon the Effective Date, each party represents and warrants
     that neither execution and delivery of this Agreement and the agreements or
     documents stated in Section 13.3 above executed by it pursuant to or in
     connection with this Agreement, nor the consummation of any of the
     transactions herein or therein contemplated, nor compliance by it with the
     terms and provisions hereof or with the terms and provisions thereof will
     (i) contravene or materially conflict with any provision of applicable law
     to which it is subject or any judgment, license, order or permit applicable
     to it, or any indenture mortgage, deed of trust, or other agreement or
     instrument to which it is a party or by which it or its property may be
     bound, or to which it or its property may be subject, (ii) violate any
     provision of its articles of incorporation or bylaws or (iii) require the
     consent or approval of, the giving of notice to, or the registration,
     recording or filing of any document with, or the taking of any other action
     in respect of, any person, entity or governmental agency.

                                                                   Page 23 of 37
<PAGE>

13.5  BINDING OBLIGATIONS.  Upon the Effective Date, each party represents and
     warrants that this Agreement and the agreements or documents stated in
     Section 13.3 above executed by it pursuant to or in connection with this
     Agreement will constitute when executed in full, the legal, valid and
     binding obligations of said party, enforceable in accordance with their
     respective terms, subject to applicable bankruptcy, insolvency,
     reorganization, fraudulent transfer, moratorium or similar laws affecting
     the enforcement of creditors rights generally and to general principles of
     equity.

14.0  ADDITIONAL TERMS

14.1  PUBLICITY.  Neither party shall publish or use any advertising, sales
     promotions, or other publicity materials that use the other party's logo,
     trademarks, or service marks without the prior written approval of the
     other party.  Each party shall have the right to review and approve any
     publicity material, press releases, or other public statements by the other
     that refer to such party or that describe any aspect of this Agreement.  In
     addition to their obligations under Article 7 of this Agreement, without
     the prior written approval of the other party, each party agrees not to
     issue any such publicity materials, press releases, public statements which
     contain information not previously publicly disclosed by mutual agreement
     of the parties, except as is required to comply with federal or state laws.
     Nothing in this Agreement establishes a lease, license or right for either
     party to use any of the other party's brands, marks, or logos without prior
     written approval of the other party.  Subject to the terms of Article 7,
     Customer and Avici agree to appropriate disclosure of their relationship in
     Avici's S-1 registration.

14.2 JOINT MARKETING.  Avici and Customer will each contribute an amount not to
     exceed [CONFIDENTIAL TREATMENT REQUESTED]/*/ of the total net price of
     Customer's purchases of Products under this Agreement for joint marketing
     activities. All such joint marketing activities will be subject to mutual
     agreement in writing, and each party will present the other with proposals
     for such joint marketing activities (including cost estimates) prior to
     making any commitments to third parties. Upon approval by a party of the
     other's joint marketing proposal, the originating party shall invoice the
     other party for its share of the expenses of such proposal [CONFIDENTIAL
     TREATMENT REQUESTED]/*/. Notwithstanding the foregoing, neither party will
     make a public announcement or issue joint marketing material; or press
     release concerning such matter without having made available to the other
     party for review and comment the proposed text of such announcement, press
     release or material, with approval not to be unreasonably withheld or
     delayed. Any proposed announcement shall be subject to the terms of Section
     14.1.

14.3  INITIAL PRESS ANNOUNCEMENT.  Subject to the terms of Section 14.1,
     Customer and Avici agree to make a public announcement of their
     relationship no later than May 26, 2000, The language of such announcement
     shall be mutually agreed upon by the parties.  It is the intention of both
     parties to announce only the relevant elements of this Agreement and to
     focus on the unique capabilities of Avici's Terabit Switch Router in
     support of Customer's network.

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 24 of 37
<PAGE>

14.4  FIELD TEST.  In lieu of carrying out the activities described in the
     provision titled "Supercomm 2000 Announcement" of that certain "Procurement
     Agreement Term Sheet" signed between the parties and dated April 10, 2000
     ("Procurement Agreement Term Sheet"), the parties shall, by no later than
     July 31, 2000, mutually agree upon a field trial test plan ("Field Trial
     Test Plan") with the Field Trial Test Plan to be carried out by no later
     than November 30, 2000.

15.0  GENERAL TERMS

15.1  RELATIONSHIP OF THE PARTIES.  This Agreement is not intended to establish
     a partnership, franchise, joint venture or agency relationship between the
     parties.  Neither party may act in a manner that expresses or implies a
     relationship other than that of independent contractor or binds the other
     party.

15.2  WAIVER OR DELAY.  Neither a party's express waiver nor its failure to
     promptly exercise any right under this Agreement will create a continuing
     waiver or expectation of non-enforcement of any tight under this Agreement.

15.3  GOVERNING LAW.  This Agreement will be construed in accordance with and
     governed by the law of the State of New York without regard to the conflict
     of law provisions of such state or any other jurisdiction.

15.4  NOTICES.  All written notices required by this Agreement must be delivered
     in person or by means evidenced by certified mail or express delivery to
     the addresses identified below for each party and will be effective upon
     receipt:

               Customer:  Williams Communications, Inc.
                         Attn: Contract Administration
                         One Williams Center,
                         Tulsa, Oklahoma 74172

               with a copy to: Williams Communications, Inc.
                         Attn: General Counsel
                         One Williams Center, Suite 4100
                         Tulsa, Oklahoma, 74172

               with a copy to: Williams Communications, Inc
                         ATTN: Vice President of Network Planning
                         One Williams Center
                         Tulsa, Oklahoma 74172

               Avici:  Avici Systems, Inc.
                         101 Billerica Avenue
                         N. Billerica, Massachusetts 01862-1256

15.5  FORCE MAJEURE.  Neither Avici nor Customer will be liable to the other for
     any delay in performing in accordance with this Agreement, other than the
     payment of amounts due

                                                                   Page 25 of 37
<PAGE>

     hereunder, if such delay arises out of an Act of God including fire, flood,
     earthquake, explosion, casualty, or accident, or out of war, riot civil
     commotion, or the requirement of any governmental agency or
     instrumentality. The party asserting that an event of force majeure has
     occurred will send the other party prompt notice thereof setting forth a
     description of the event of force majeure, an estimate of its effect upon
     the party's ability to perform its obligations under this Agreement and the
     duration or expected duration thereof. In addition, if, at any time after
     Customer has satisfied its purchasing obligation under Sections 2.1 and
     2.2, an event of force majeure endures for a period of ninety (90) days
     where Avici is the party whose performance is prevented or delayed by an
     event of force majeure, Customer shall have the right to terminate this
     Agreement upon thirty days' written notice to Avici. Avici shall have no
     right to terminate this Agreement in the event either its or Customer's
     performance hereunder is delayed or prevented by an event of force majeure
     regardless of how long the event of force majeure exists,

15.6  ASSIGNMENT.  This Agreement may not be assigned by either party, by
     operation of law or otherwise, without the express prior written consent of
     the other party (which consent will not be unreasonably withheld), except
     that no such consent will be required in connection with (a) any merger,
     consolidation, or the transfer of all or substantially all of such party's
     assets or (b) an assignment by a party to any of its Affiliates.  This
     Agreement will be binding upon, and inure to the benefit of, the permitted
     successors and assigns of each party.  Any purported assignment in
     violation of this Section 15.6 will be null and void.  Notwithstanding
     anything in this Agreement to the contrary, Customer may assign some or all
     of its rights and obligations hereunder to State Street Bank and Trust
     Company of Connecticut, National Association, in connection with a
     financing by Customer of construction of its fiber optic network; in
     addition, Street Bank and Trust Company of Connecticut, National
     Association, may further assign this Agreement as collateral for such
     financing; provided that if Customer makes an assignment to State Street
     Bank and Trust Company of Connecticut, National Association, pursuant to
     this paragraph, Customer (or its assignee pursuant to an assignment made
     under the other provisions of this Agreement) shall guarantee performance
     of the assignee's obligations.

15.7  LEGAL EXPENSES.  The prevailing party in any legal action arising out of
     this Agreement will be entitled to recover court costs and reasonable
     attorneys' fees.

15.8  SEVERABILITY.  If any provision of this Agreement is held invalid by any
     law or regulation of any government or by any court or arbitrator, that
     invalidity will not affect the enforceability of any other provision.

15.9  ENTIRE AGREEMENT.  This Agreement, together with the Attachments,
     constitutes the parties' entire agreement relating to its subject matter.
     This Agreement supercedes all prior or contemporaneous oral or written
     Communications, proposals, conditions, representations and warranties,
     including, among others, the "Procurement Agreement Term Sheet", and shall
     prevail over any conflicting or additional terms of any quote, order,
     acknowledgement, or other communication between the parties relating to its
     subject matter during the term of this Agreement.  No modification to this
     Agreement will be binding, unless in writing and signed by an authorized
     representative of each party

                                                                   Page 26 of 37
<PAGE>

15.10  CONFLICT OF INTEREST.  Avici will not use any funds received under this
     Agreement for illegal or "improper" purposes related to the Agreement.
     Avici will not pay any commissions, fees or rebates to any employee of
     Customer, nor favor any employee of Customer with gifts of entertainment of
     significant cost or value.  If Customer has reasonable cause to believe
     that one of these provisions has been violated, Customer or its
     representative may audit the records of Avici for the purpose of
     establishing compliance with such provisions.  For purposes of this
     Section, Customer shall include all affiliated companies of Customer.

15.11  ESCROW AGREEMENT. The parties shall within [CONFIDENTIAL TREATMENT
     REQUESTED]/*/from the Effective Date, mutually agree to the terms of an
     escrow agreement which shall provide for the deposit, by no later than
     December 31, 2000, of the source code (and other relevant materials) with
     respect to the Product and Software with an independent, recognized escrow
     agent. Such escrow agreement shall provide Customer the right to obtain and
     use such source code and other materials deposited under certain
     conditions. As long as this Agreement has not terminated or expired,
     [CONFIDENTIAL TREATMENT REQUESTED]/*/. Avici agrees to provide regular
     reports to Customer regarding Avici's efforts to prepare a final written
     version of the source code suitable for deposit.

15.12  COUNTERPARTS; FACSIMILE COPY.  This Agreement may be executed in separate
     counterparts, each of which so executed and delivered shall constitute an
     original, but all such counterparts shall together constitute one and the
     same instrument.  The parties stipulate that facsimile copies of the signed
     Agreement will be admissible in evidence for all purposes in any proceeding
     as between the parties.

15.13  REMEDIES.  Subject to the provisions regarding exclusive remedy in
     Sections 3.4, 3.5 and 8.9 the remedies available to either party under this
     Agreement are cumulative.  The exercise of any one remedy will not be
     deemed an election of such remedy to the exclusion of other remedies; and
     the rights and remedies of the parties as set forth in this Agreement are
     not exclusive and are in addition to any other rights and remedies
     available to it at law or in equity.

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 27 of 37
<PAGE>

     In witness whereof, the parties have caused this Agreement to be executed
by their respective authorized representatives as of the Effective Date,

AVICI SYSTEMS, INC.                 WILLIAMS COMMUNICATIONS, INC.

By: /s/ Brian McCormack             By: /s/ Howard Janzen
   ----------------------------        ----------------------------

Name: Brian McCormack               Name: Howard Janzen
     --------------------------          --------------------------

Title: Vice President, Sales        Title: President & CEO
      -------------------------           -------------------------

Date: May 17, 2000                  Date: May 17, 2000
     --------------------------          --------------------------

                                                                   Page 28 of 37
<PAGE>

                                  ATTACHMENT A

                              AVICI SYSTEMS, INC.

                                   PRICE LIST

<TABLE>
<CAPTION>
PRODUCT PART NO.                            DESCRIPTION                              LIST PRICE
--------------------------------------------------------------------------------------------------
<S>                                     <C>
[CONFIDENTIAL TREATMENT REQUESTED]/*/

</TABLE>

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 29 of 37
<PAGE>

[CONFIDENTIAL TREATMENT REQUESTED]/*/

All Prices FOB North Billerica MA 01862

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 30 of 37
<PAGE>

                                  ATTACHMENT B

TSR Product Specifications

[CONFIDENTIAL TREATMENT REQUESTED]/*/

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 31 of 37
<PAGE>

[CONFIDENTIAL TREATMENT REQUESTED]/*/

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 32 of 37
<PAGE>

[CONFIDENTIAL TREATMENT REQUESTED]/*/

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 33 of 37
<PAGE>

[CONFIDENTIAL TREATMENT REQUESTED]/*/

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 34 of 37
<PAGE>

[CONFIDENTIAL TREATMENT REQUESTED]/*/

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 35 of 37

<PAGE>
                                 ATTACHMENT B1

Market Leadership -- Additional Features and Capabilities

Avici acknowledges Customer's desire to have market-leading technology.  In
connection therewith, Avici agrees to meet the performance specifications
described below by the milestone dates indicated.

[CONFIDENTIAL TREATMENT REQUESTED]/*/

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 36 of 37
<PAGE>
                                  ATTACHMENT C
                              Third Party Software

[CONFIDENTIAL TREATMENT REQUESTED]/*/

---------------------
/*/ [CONFIDENTIAL TREATMENT REQUESTED] INDICATES MATERIAL THAT HAS BEEN
OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH
OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1933,
AS AMENDED.

                                                                   Page 37 of 37<PAGE>
                                                                   EXHIBIT 10.10
                                                                   -------------
December 1, 1998

Mr. Brian McCormack
2600 Cole Avenue, Apt. 108
Dallas, TX  75204

Dear Brian:

It is distinct pleasure to offer you the position of Vice President of Sales
with Avici Systems, Inc.  In this capacity you will report to me.  Your starting
bi-weekly base salary will be 5,388.00 which annualized is $140,088.  In
addition to your base salary, you will be entitled to a non-recoverable draw-
salary supplement of $10,000 per year for the first year of your employment
payable in bi-weekly installments of $384.62.

You will also be eligible for a sales incentive of $150,000 at target payable in
quarterly installments based on revenue.  there will be no cap in the sales
incentive plan.  Fifty percent (50%) of the first year's target of $75,000 of
the $150,000 is guaranteed in the first year.  For the quarter ending March 31,
1999, MBO's will be established in lieu of a sales incentive target.

Therefore, your total targeted compensation will be $300,000 during your first
year of employment comprised of $140,088 in base salary, $10,000 in the
draw/salary supplement, and $150,000 in the targeted sales incentive.  Avici
Systems, Inc. will guarantee $225,000 of that amount during the first year
provided you remain in our employ for the year.

In addition, subject to approval of the Board of Directors, you will be granted
options in the amount of 100,000 shares of Avici Common Stock with terms and
conditions as per the Corporation's stock incentive plan.  The stock will vest
over four years at 25% per year.  After your first anniversary, the remaining
shares vest on a per month basis of 2.0833%.  In the event of a Change of
Control of Avici, your stock options will become fully vested.  The exercise
price of your options will be $1.00 per share, provided you accept this offer
before December 7 and start with Avici no later than January 13, 1999.

Avici will also offer a conditional severance of $200,000 in the event you are
involuntarily terminated from the company of any reason other than gross
misconduct and you did not receive a severance package from your current
employer.

Avici Systems, Inc. also agrees to pay actual and reasonable living expenses for
you during the initial period of your employment, for up to three months.  The
arrangement will cover temporary living during the workweek, actual and
reasonable out-of-pocket meal expenses, and coach airline travel to and from
your home on the weekends.  Avici will reimburse you for your relocation to the
Massachusetts area for up to $50,000 of actual and reasonable expenses and tax
liabilities.
<PAGE>

Mr. Brian McCormack
December 1, 1998
Page 2

The Company has a competitive employee benefit program.  You will be covered by
this plan based on the standard eligibility requirements for all Avici
employees.  Avici's benefits are described in a document called "Avici's 1999
Benefits Summary for the Full-Time Employees."  Avici's current program includes
vacation (accrued 10 days) and holidays (10 days).  Effective January 1999,
Avici will offer three medical insurance plans to choose from, Fallon HMO,
Harvard Pilgrim HMO and Harvard Pilgrim PPO.  Avici also offers Fallon or Delta
Dental plans, a Merrill Lynch 401(k) program, life insurance, supplemental life
insurance, short and long-term disability benefits.  Please note that Avici
reserves the right to change or discontinue any of its current benefits plans,
providers and policies in the future.

In accordance with federal law, you will be asked to provide documentation
proving your eligibility to work in the United States.  Please bring proper
documentation on your first day of work.  This can be a U.S. Passport or a
driver's license and birth certificate/social security card.

Please confirm your acceptance of this employment offer by signing one copy of
this letter which will indicate your acceptance of our offer as well as your
anticipated start date and return it to me.

This letter does not constitute a guarantee of employment or a contract, and
your employment with Avici Systems, Inc. may be terminated by you or the Company
at any time for any reason.

Employment with Avici is subject to your signing the Avici Incentive Stock
Options Agreement and the Invention and Non-Disclosure Agreement.  Note that
these Agreements are available for your review prior to accepting this offer.

This offer expires as of the close of business on Monday, December 7, 1998.
This offer supercedes any prior offers, both verbal and written.

Brian, we are very pleased by the prospect of your addition to the Avici team
and we are sure that you will play an important role in the future success of
the Company.

Sincerely,

/s/ Surya Panditi
Surya Panditi
President and CEO
Avici Systems, Inc.

Accepted by: /s/ Brian McCormack   Date: 12/3/98
            ---------------------       ----------
             Brian McCormack

Start Date: 1/13/99
           ----------

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