<PAGE>   1
                                                                    EXHIBIT 10.9

                                  [PLEXUS LOGO]
                  Comprehensive Professional Services Agreement


This Agreement is hereby entered into on this 19th day of July, 2000 by and
between Sitara Networks, Inc., of 60 Hickory Drive, Waltham, MA 02451
(hereinafter "Customer") and Plexus Corp. of 55 Jewelers Park Drive, Neenah, WI
54956, (along with its wholly-owned subsidiaries Plexus Technology Group, Plexus
Electronic Assembly, and SeaMED, a Plexus Company hereafter collectively
referred to as "Plexus".)

A. PRODUCT DEVELOPMENT AND PROTOTYPE PHASE INCLUSIVE (Prototype Phase inclusive)
The terms and conditions set forth in this Section A, Product Development and
Prototype Phase, as well as the terms and conditions set forth in Section C,
Standard Terms and Conditions, shall be applicable to this portion of the
Agreement.

         1. PROGRAM
         Plexus will undertake for the Customer a Program which could also
         include a prototype program, defined in the accompanying Proposal which
         this Agreement is part of. The activity described in the accompanying
         Proposal will be referred to as the "Program". Prototype program, if
         applicable, will be defined at the time the program is defined in
         writing by the Customer.

                  a)       At the Customers request, Plexus will provide a
                           bi-monthly or as agreed upon by both parties,
                           detailed engineering report showing progress of the
                           agreed to Program and schedule.

                  b)       From time to time, Plexus and the customer may
                           redefine, revise, enlarge, amend, abandon, or
                           undertake a new phase of activity as an addition to
                           the Program. These revisions to the Program shall be
                           defined in writing and agreed upon by both parties.
                           Any additional cost associated with the revisions
                           shall be quoted by Plexus and authorized by the
                           Customer before work can proceed on them. Except for
                           appropriate changes in objectives, schedules and
                           budgets, all additional work shall be conducted under
                           the terms of this Agreement.

                  c)       Unit cost estimates provided in this Proposal or
                           during the course of the Product Development Phase
                           are not binding and are for informal use only.

                  d)       Sections B.1. and B.2.h) also apply to prototype
                           programs.

         2. DRAWINGS, RECORDS AND MODELS
         At this time, Plexus will develop all records, sketches, original
         drawings, photographs, prototypes, or finished models and the use
         thereof are the exclusive property of the Customer. Normally any such
         items, which are of continuing value to the Customer, are returned to
         the Customer. In order to avoid questions regarding value, the customer
         will issue written instructions to Plexus within sixty (60) days
         following termination or completion of the Product Development Phase
         for the disposition all such items. Plexus is authorized to determine
         the disposition of any such items, which are not covered by written
         instructions.

         At the completion of the Product Development Phase, the customer will
         receive hard copies and/or magnetic medium of the files generated as a
         result of the Product Development and Prototype Phase. These
         deliverables are described in the Proposal. Customer will be
         responsible for maintaining and archiving the deliverables in a
         suitable environment.

         3. COMMITMENT TO MANUFACTURE
         Customer understands that Plexus desires to manufacture the product at
         the end of the program. Customer understands that manufacturing of the
         product by a competitor of Plexus is undesirable to Plexus. Should
         Customer manufacture the product outside Customer's facilities,
         Customer will work with Plexus in good faith to ensure that Plexus is
         awarded the manufacture of the product, provided Plexus is cost
         competitive and capabilities analysis is proven.

Sitara Networks-Final Execution Comprehensive Professional Services Agreement
<PAGE>   2
         4. PROTOTYPE UNITS
         Engineering and Pre-production Prototypes: During the Product
         Development and Prototype Phase, Plexus may generate several versions
         of the unit to verify design concepts. The number of prototypes and/or
         pre-production units that Plexus will deliver to the Customer is
         outlined in the body of the proposal. These prototypes may or may not
         meet the requirements of the product specification. Once these units
         are built, any modifications (hardware, software, or mechanical)
         required as a result of further testing will be done by Plexus on a
         time and material basis.

         5. ON-GOING SUPPORT
         At the conclusion of the Product Development and Prototype Phase of the
         Program, Plexus and the Customer will jointly review the entire Program
         to assure compliance with the Program Specifications. When this has
         been completed, Plexus will notify the Customer in writing that this
         Phase has been completed, and the Customer will have thirty (30) days
         to respond by identifying errors or omissions they believe should be
         corrected by Plexus under this Agreement. After that period, the
         Customer requests for on-going support will be handled on a time and
         materials basis at Plexus' then current billing rates.

         6. COMPENSATION, CHARGES, AND BILLING

                  a)       Unless other specific arrangements are agreed upon,
                           Plexus will invoice the Customer each month for
                           services rendered up to the total amount specified in
                           the Proposal. Invoices are subject to terms of net
                           amount due in thirty (30) days following the date of
                           the invoice.

                  b)       Unless specifically stated to the contrary in the
                           Proposal, the following parts and/or services are not
                           included in the base Proposal and may be an
                           additional billing monthly as costs are incurred as
                           stated in Customer authorized quotation.

                                    1. Parts, PCBs and freight which may be
                                    required for project, breadboard and/or
                                    prototypes, plus actual cost plus defined
                                    mark-up.
                                    2. Tooling charges for custom components
                                    such as graphics, plastics, metal, etc. -
                                    actual cost plus defined mark-up.
                                    3. Telephone, fax, and travel expenses
                                    incurred by Plexus in pursuing the
                                    customer's objectives and directives -
                                    actual cost.
                                    4. Any travel required by Plexus in pursuing
                                    the Customer's objectives and directives
                                    will be billed at the normal hourly rate of
                                    the personnel performing the work for the
                                    Customer, with a maximum day billing of 8
                                    hours plus any expenses incurred.
                                    5. Services of consultants or other outside
                                    personnel retained by Plexus will be
                                    invoiced to the customer at a rate
                                    commensurate with Plexus' in-house rates or
                                    actual cost plus defined mark-up.
                                    6. NRE and Tooling: Markup percentage on NRE
                                    is 10%. Plexus will make reasonable efforts
                                    to minimize tooling and NRE charges
                                    including competitive quoting. Customer has
                                    the right to review NRE and tooling quotes.
                                    Customer has the right to alternatively
                                    source NRE materials if NRE pricing cannot
                                    be mutually agreed upon between the parties.

         7. PRODUCT DEVELOPMENT CANCELLATION
         During the Product Development and Prototype Phase, Customer may cancel
         this project upon providing forty-five (45) days written notice to
         Plexus. In such an event, the Customer shall be responsible for all
         expenses incurred through the effective date of cancellation,
         including, but not limited to, all labor undertaken and all materials
         purchased or ordered prior to said effective date. To help minimize the
         impact of cancellation charges, Plexus will attempt to restock
         components at the supplier, resell the components, and/or utilize the
         components on non-customer assemblies.

         8. ADVANCED PROCUREMENT OF COMPONENTS/TOOLING
         Plexus may, with customer prior approval on dollar value exceeding $500
         procure for assemblies for either Prototype or Risk Reduction any items
         that requires Customer to meet ship date requirements. Any deviation
         from the Supplied Approved Vendor List "AVL" (or franchised
         distributor) requires Customer prior approval.

Sitara Networks-Final Execution Comprehensive Professional Services Agreement

                                                                               2
<PAGE>   3
B. MANUFACTURING PHASE
The terms and conditions set forth in this Section B, Manufacturing Phase,
Section A, Product Development Phase, as well as the terms and conditions set
forth in Section C, Standard Terms and Conditions, shall be applicable to this
portion of the Agreement.

         1. DEFINITIONS
         For the purpose of this Manufacturing Phase:

         "Long Lead Time Component(s)" shall mean all of those individual parts
         and materials whose current lead times extend beyond forty (40)
         business days. The Long Lead Time Components may, from time to time, be
         reviewed by Plexus and Customer, at the request of either party due to
         possible changes in market conditions of supply and demand affecting
         the procurement by Plexus of the Components and/or Long Lead Time
         Components for the assemblies hereunder. Any changes resulting from
         such review shall be with the mutual written agreement of Plexus and
         Customer.

         "NCNR Component(s)" shall mean those parts that are not cancelable once
         placed on order with Plexus suppliers, and are not returnable once
         delivered to Plexus. The NCNR Component(s) may, from time to time, be
         reviewed by Plexus and Customer, at the request of either party due to
         possible changes in market conditions of supply and demand affecting
         the procurement by Plexus of the Components and/or NCNR Component(s)
         for the assemblies hereunder. Any changes resulting from such review
         shall be with the mutual written agreement of Plexus and Customer.

         "Special Component(s)" shall mean those parts that have special
         procurement conditions such as limited change parameters or other
         special liability conditions that are required by Plexus' suppliers.
         The Special Component(s) may, from time to time, be reviewed by Plexus
         and Customer, at the request of either party due to possible changes in
         market conditions of supply and demand affecting the procurement by
         Plexus of the Components and/or Special Component(s) for the assemblies
         hereunder. Any changes resulting from such review shall be with the
         mutual written agreement of Plexus and Customer.

         "Monthly Rolling Quantity Forecast of Delivery Requirements" shall mean
         the written documents provided to Plexus by Customer each month
         indicating the delivery requirements projected for the next twelve (12)
         months.

         "Obsolete Components" shall mean all material used in Buyer's product
         for which there is no current or future demand.

         "Inactive Components" shall be all material which is non-obsolete
         material with a balance that is greater than zero after all demand has
         been met.

         "Excess Components" shall be all material with a balance that is
         greater than zero after six (6) months that will be consumed by demand
         beyond six (6) months.

         2. AUTHORIZATION OF WORK PROCUREMENT OF MATERIALS
         The following terms will apply:

                  a)       The purpose of this section is to define the methods
                           under which Plexus will procure materials to support
                           manufacturing of product for the Customer. The intent
                           is to provide the Customer with flexibility to alter
                           and/or cancel schedules within a reasonable period of
                           time while at the same time minimizing Plexus
                           liability that is a result of those alterations and
                           cancellations. In order to offer the best possible
                           price, Plexus does not attempt to build unanticipated
                           carrying charges into its price. When changes in
                           Customer requirements occur that cause Plexus to
                           incur unanticipated expenses that are the result of
                           Customer actions, the Customer is expected to
                           reimburse Plexus for the costs incurred.

                  b)       For each assembly and/or board level to be
                           manufactured, Plexus establishes a manufacturing lead
                           time, which is the number of business days it will
                           take, an average, to receive and kit all

Sitara Networks-Final Execution Comprehensive Professional Services Agreement

                                                                               3
<PAGE>   4
                           components, assemble, test and ship the lot, unless
                           moved to Finished Goods Inventory ("FGI"). Unless
                           otherwise noted, this manufacturing lead-time is
                           twenty (20) business days. Plexus agrees to review
                           the manufacturing lead-time after three (3) months of
                           production of the product, and thereafter mutually
                           agree to any adjusted manufacturing lead-time. Plexus
                           schedules all components for a particular lot of
                           assemblies to arrive one manufacturing lead-time
                           prior to the Customer due date. Plexus then uses this
                           information, together with the Forecast and Purchase
                           Order information as defined below, to place
                           commitments to its suppliers for materials.

                  c)       At the beginning of each month, Customer will provide
                           a twelve (12) month rolling forecast of total
                           requirements listing top level assembly and/or board
                           level assembly requirements by month. This monthly
                           rolling forecast shall be used by Plexus to determine
                           the Components and/or the Long Lead Time Components,
                           NCNR Components and/or Special Components that Plexus
                           must obtain and/or procure and/or inventory, and
                           unless otherwise agreed to, Plexus will negotiate
                           pricing contracts with its suppliers based upon the
                           forecast.

                  d)       For purposes herein current month shall mean a
                           rolling four (4) week window. Changes from the
                           previous month's Purchase Orders are allowed to the
                           current Purchase Orders as follows:

                           i) Current Month:               No change allowed.
                           ii) Second Month:               Up to 50% reduction
                                                           or increase.
                           iii) Third Month:               Up to 75% reduction
                                                           or increase.
                           iv) Fourth Month (and beyond)   As required;
                                                           increase or decrease.

                           Changes in excess of these parameters may be mutually
                           agreed to by Plexus and Customer.

                           Changes to the monthly rolling Forecast may result in
                           an excess inventory position (due to component market
                           conditions), the impact for which is not considered
                           in the original cost of the assembly. In addition,
                           Plexus may have to place orders for quantities of
                           components in excess of that required to support
                           Customer requirements. This may be as a result of
                           minimum order size requirements or standard package
                           sizes from the supplier. In the event that the
                           monthly rolling Forecast does not define component
                           consumption of sufficient magnitude to eliminate the
                           excess inventory within sixty (60) business days,
                           Plexus will notify Customer of its excess inventory
                           position of Components and/or Long Lead Time
                           Components, NCNR Components and/or Special Components
                           that Plexus has procured and is inventorying and/or
                           has on order with its suppliers. Upon receipt of such
                           notification, Customer will purchase the excess
                           inventory at Plexus' actual cost plus the agreed upon
                           quoted material mark-up. Payment terms are net thirty
                           (30) days.

                  e)       At the end of each quarter, Customer will issue
                           Purchase Orders ("POs") for top level and/or board
                           level assemblies in accordance with, but not limited
                           to the monthly rolling Forecast of total
                           requirements. These POs will cover the next quarter's
                           total requirements. The pricing for that quarter's
                           POs will be reviewed for cost reductions the last
                           month of the prior quarter. There is a targeted price
                           reduction at a minimum of every other quarter. If
                           Plexus reduces cost, they keep 50/50% - if Customer
                           reduces cost it is all passed along to the Customer.

                  f)       Plexus shall procure in advance of Customer POs for
                           assemblies pursuant to the monthly rolling Forecast
                           for each top level and board level assembly, the
                           Components and/or Long Lead Time Components, NCNR
                           Components and/or Special Components, as required for
                           each top level and board level assembly. Plexus shall
                           purchase all components in accordance with Customer's
                           approved vendor list (AVL), exclusively. Any
                           deviation from the AVL must be authorized in writing
                           by Customer prior to purchase by Plexus.

                  g)       Customer may request that Plexus purchase from
                           Customer certain components that the Customer has in
                           its inventory as a result of the transfer of new
                           business to Plexus. Plexus and Customer will
                           negotiate in good faith to determine pricing and
                           title transfer of such inventory. In addition, open
                           component purchase order(s) with Customer's suppliers
                           may be transferred to Plexus upon mutual agreement.

Sitara Networks-Final Execution Comprehensive Professional Services Agreement


                                                                               4
<PAGE>   5
                  h)       Customer will communicate a monthly Production
                           Schedule to Plexus outlining the top level assembly
                           and/or board level production requirements. The
                           Production Schedule will be firmed for the current
                           month fifteen (15) business days prior to the start
                           of that month, will be within Forecasted quantities,
                           and have a six (6) month rolling horizon. Changes to
                           the Production Schedule are allowed as follows:

                           (1) Current Month:              No change Allowed.
                           (2) Second Month:               Up to 50% reduction.
                           (3) Third Month:                Up to 75% reduction.
                           (4) Fourth Month (and beyond)   As required; increase
                                                           or decrease.

                           Changes to the Production Schedule within the current
                           month may be mutually agreed to by Plexus and
                           Customer.

                           i)       At any time during the current month,
                                    Customer may exercise an increase or
                                    decrease in delivery requirements
                                    (Flexibility Quantity). This Flexibility
                                    Quantity is limited to a maximum
                                    accumulation of the Flexibility Percentage
                                    outlined in Attachment A (to be defined) for
                                    each top level and board level assembly, for
                                    the current month's production based on the
                                    average of the current sixty (60) business
                                    days of the Forecast. This Flexibility
                                    Quantity will be available within ten (10)
                                    business days of the Customer request.
                                    Additional Flexibility Quantity may be
                                    mutually agreed to between Plexus and
                                    Customer Any finished goods inventory (FGI)
                                    at the end of the current month will be
                                    netted from the Forecast in accordance with
                                    the change provisions of this Agreement.
                                    Customer understands and agrees that there
                                    may be associated costs with the efforts
                                    regarding this section and imposed by
                                    Plexus, which shall be borne by the
                                    Customer.

                           ii)      For Production Schedule decreases issued
                                    within the current month beyond the
                                    allowable Flexibility Quantity decrease, the
                                    Customer will pay full price and accept
                                    title and risk of loss for completed
                                    assemblies and any work in process materials
                                    and labor.

                                    (1)      Accept shipment of the completed
                                             assemblies within the current month
                                             as originally scheduled; or
                                    (2)      Pay full price and accept title and
                                             risk of loss for completed
                                             assemblies any work in process
                                             materials and labor.

                           iii)     For Production Schedule decreases issued
                                    outside the current month and beyond the
                                    allowable Production Schedule decrease
                                    parameters, the Customer will:

                                    (1)      Pay for and accept title and risk
                                             of Loss for the value of the
                                             components (cost plus the agreed
                                             upon quoted material markup) which
                                             Plexus is unable to return or
                                             reschedule to meet the new schedule
                                             requirements; and
                                    (2)      Pay Plexus for any additional cost
                                             from supplies resulting from the
                                             prescheduling.

                           iv)      For Production Schedule increases beyond the
                                    allowable Flexibility Quantity, Plexus will
                                    make its best effort to obtain the
                                    components necessary to meet Customer
                                    requirements. However, Plexus may be
                                    unsuccessful in obtaining all of the
                                    components required to meet the Customer's
                                    increased requirements at which Plexus will
                                    provide satisfactory evidence to Customer of
                                    such inability to meet such requirements. In
                                    that situation, Plexus reserves the right to
                                    Customer payment of the value of all
                                    inventory in house as of the delivery date
                                    that is a result of the increased
                                    requirement, which will be agreed upon by
                                    Plexus and Customer.

                  i)       Engineering Change

                           The term "Engineering Change(s)" (hereinafter called
                           "EC" or "EC's") shall mean those mechanical,
                           software, or electrical design and/or specification
                           and requirement changes which, if made to the
                           assemblies to be delivered hereunder, would affect
                           the schedule performance,

Sitara Networks-Final Execution Comprehensive Professional Services Agreement

                                                                               5
<PAGE>   6
                           reliability, availability, serviceability,
                           appearance, dimensions, tolerance, safety or purchase
                           price of such assemblies or which would require
                           additional approval test.


                               Plexus may determine that Engineering Changes
                               will affect its ability to maintain the delivery
                               schedule, due to the lead time of newly specified
                               parts and/or the impact of substantial rework or
                               modification. Under these circumstances, Plexus
                               reserves the right to define a new Production
                               Schedule for delivery and treat this as a
                               Production Schedule Change, with the Customer
                               liability as defined under Section 2 (g)
                               (ii)(iii) and (iv) above.

                               Upon receipt, Plexus shall review Customer's
                               proposed EC and Plexus shall give to Customer a
                               written evaluation of the EC, stating Plexus'
                               cost to implement the EC (including the cost to
                               modify any tooling), the excess quantity of
                               Components (including Long Lead Time Components,
                               NCNR Components and/or Special Components) Plexus
                               has inventoried and/or has on order with its
                               suppliers that are excess due to the EC, and
                               associated costs and expenses such Components
                               and/or Long Lead Time Components, NCNR Components
                               and/or Special Components that Customer shall be
                               liable for and the cost savings, if any,
                               resulting from the EC, and the expected effect on
                               the Production Schedule, availability and/or
                               purchase price of such assemblies, or which may
                               require additional approval tests by Customer.
                               Plexus will submit its written evaluation to the
                               Customer within five (5) business days after
                               receipt of the proposed EC, or in conjunction
                               with Customer's stated timeframe.

                  j)       Customer Supplied Parts
                           The Customer may provide certain components required
                           to build Customer's assemblies. The Customers
                           inability to provide parts in a timely manner may
                           effect Plexus' ability to meet its delivery schedule
                           and may cause Plexus to incur extraordinary expenses
                           to hold Plexus purchased material and/or labor in
                           process. Under these circumstances, Plexus reserves
                           the right to define a new Production Schedule for
                           delivery based upon component availability
                           information from the Customer and treat this as a
                           Production Schedule change, with the Customer
                           liability as defined under Section 2 (g) (ii)(iii)
                           and (iv) above.

                  k)       Minimum Component Purchases
                           Plexus may have to place order for quantities of
                           components in excess of that required to support
                           Customer requirements. This may be as a result of
                           minimum order size requirements or standard package
                           sizes from the supplier. The customer will agree to
                           have the cost of the excess components amortized over
                           a maximum of six (6) month's requirements, or will
                           place a purchase order separately for the excess
                           components.

                  1)       Obsolete, Inactive and Excess Inventory coverage
                           Customer and Plexus agree to review obsolete,
                           inactive and excess component(s) inventory on a
                           monthly basis, and to agree to disposition of such
                           material. Customer further agrees to issue monthly
                           Purchase Orders for actual purchase price plus margin
                           of all obsolete, inactive and excess materials(s),
                           due to changes in Customer's demand.

                  m)       Cancellation
                           Customer may cancel requirements defined in orders
                           and/or forecasts at any time before the scheduled
                           delivery date. Any assembly requirements canceled
                           within the manufacturing lead-time of the scheduled
                           delivery date will be invoiced at the full agreed to
                           price for the completed assembly.

                           For assembly requirements canceled outside the
                           manufacturing lead time of the scheduled delivery
                           date, Customer's liability to Plexus will be the
                           value of the components in Plexus' inventory
                           (including the full markup as defined in the Plexus
                           quotation), and other components for which Plexus has
                           liability but which are not in Plexus inventory, as
                           well as payment for any and all in-process
                           manufacturing costs and expenses, and reasonable
                           administrative costs and expenses. Plexus will
                           deliver an itemized list of these costs to customer.
                           Customer agrees to pay the costs identified by Plexus
                           within thirty (30) business days of notification of
                           such costs. To help

Sitara Networks-Final Execution Comprehensive Professional Services Agreement

                                                                               6
<PAGE>   7
                           minimize the impact of cancellation charges, Plexus
                           will attempt to restock components at the supplier,
                           resell the components, and/or utilize the components
                           on non-customer assemblies.

                  n)       Cost Reduction
                           Cost Reductions will be reviewed by both parties
                           quarterly. Plexus initiated cost reductions will be
                           shared 50/50 for the term of this Agreement. Customer
                           initiated reductions will be passed through at full
                           value. Actual cut-in reduction will based upon, at
                           minimum, inventory at Plexus and committed on-order
                           Product with Plexus' suppliers.

                  o)       Customer Property
                           Tooling and consigned material - Plexus has the
                           responsibility to have proper security, and material
                           storage. Customer shall be responsible for repairing,
                           upgrading, replacing and/or maintaining the materials
                           and/or equipment consigned to Plexus. However, Plexus
                           shall provide routine maintenance, of which
                           associated costs are borne by the Customer.

                  p)       Cost Increases or Changes
                           Parties will meet quarterly to discuss cost increases
                           or changes due to parts demand and availability.

         3. PACKAGING AND SHIPPING

                  a)       Product will be shipped to the customer in a manner
                           that meets industry standard packaging requirements.
                           Plexus is not liable for design related packaging
                           issues but is liable for products improperly
                           packaged. Customer is responsible for the selection
                           of the shipping company unless otherwise directed.

                  b)       Distribution Services: Plexus will provide Customer
                           with "Direct Ship" Distribution Services for the
                           specified product(s) identified in the Pricing Model
                           (Attachment D ), attached hereto and made a part
                           hereof. Prior to expanding these services for
                           additional product(s), Plexus and Customer must
                           review and mutually agree upon written changes to
                           this Agreement.

                  c)       Upon manufacturing completion of Direct Ship product,
                           Plexus will invoice Customer and identify/store
                           product as Customer's Finished Goods Inventory in an
                           approved storage location. Consequent to the invoice
                           transaction, Customer assumes complete title,
                           liability, and ownership of the Customer's Finished
                           Goods Inventory, which includes insurance coverage
                           and loss of product. Plexus assumes no liability for
                           Customer's Finished Goods Inventory on the premise or
                           in transit.

                  d)       At some point in time the Customer will provide
                           completely functional computer terminals, with
                           applicable hardware and software, dedicated printer,
                           and access to Customer's computer system.
                           Additionally, Customer will provide necessary
                           training and on-going computer support. At such time
                           immediately following the invoice transaction, Plexus
                           will "receive" Direct Ship product onto Customer's
                           computer system.

                  e)       When Plexus receives signal to direct ship product,
                           Plexus will complete appropriate actions and
                           transactions on Customer's computer system to
                           package, per specifications, and ship product. Plexus
                           to ship product 3rd party. Freight charges related to
                           this activity shall be borne by Customer. Plexus will
                           guarantee same business day shipment of product for
                           domestic locations, if signal is received prior to
                           2:00 p.m. CST. For signals received after 2:00 p.m.
                           CST, Plexus will make every effort to ship domestic
                           locations the same business day, but will guarantee
                           next business day shipment. Plexus will guarantee
                           shipment of product for all international locations
                           within two (2) business days. If any order(s) or
                           combination of orders exceed agreed upon Finished
                           Good Inventory "FGI" levels this subsection 3(e) does
                           not apply and shall not be enforced.

Sitara Networks-Final Execution Comprehensive Professional Services Agreement

                                                                               7
<PAGE>   8
                           The cost to provide these Direct Ship Distribution
                           Services will be included in the unit price of each
                           assembly shipped. Payment terms and conditions shall
                           be pursuant to this Agreement.

                  g)       Any EC's that will require re-work and/or upgrade for
                           Customer Finished Goods Inventory shall be the sole
                           liability of the Customer and follow standard
                           re-work/upgrade policies and procedures as specified
                           in this Agreement.

         4. FINISHED GOODS INVENTORY

                  a)       Finished Goods Inventory Introduction
                           The Customer has requested Plexus to begin building a
                           finished goods inventory ("FGI") of Customer's
                           product(s)hereinafter "finished assemblies or
                           product(s)") and store ("warehouse") such finished
                           assemblies on site at Plexus' facilities and/or
                           warehouse(s) after issuance of Customer's purchases
                           orders, for indefinite periods of time, until higher
                           level assembly or delivery instructions are issued by
                           the Customer.

                  b)       Payment Terms related to FGI
                           Customer further agrees to and understands that once
                           Product(s) is receipted into FGI, Plexus shall issue
                           an invoice for that Product(s) and payment terms
                           shall be as set forth in Section 5 of this Agreement.

                  c)       Cancellation of Purchase Orders related to FGI
                           The Parties agree that cancellation by the Customer
                           of any of the Purchase Orders issued to Plexus
                           relating to such finished goods inventory will create
                           material liability on behalf of the Customer, and
                           Customer agrees to abide by all the terms and
                           conditions set forth in Section C "Standard Terms and
                           Conditions" of this Agreement regarding cancellation
                           of Purchased Orders in the event of such
                           cancellation.

                  d)       Purchase Orders related to FGI
                           The finished goods inventory quantities will be
                           determined by the purchase orders issued by Customer
                           to Plexus. Plexus agrees to place this product in FGI
                           based on the same terms and conditions set forth in
                           Section C "Standard Terms and Conditions" of this
                           Agreement.

                  e)       Location of FGI
                           Plexus agrees to make available to Customer a
                           secured, segregated area at Plexus' facility for the
                           purpose of maintaining and storing Finished Goods
                           Inventory (hereinafter "FGI"). Plexus will furnish
                           sufficient heat and electricity, without charge to
                           Customer to adequately store such FGI. Plexus agrees
                           to maintain the storage area of the FGI in a clean
                           and orderly manner.

                  f)       Storage of FGI
                           Customer agrees Plexus shall be allowed, without
                           Customer's prior consent written or otherwise, to
                           make any alterations, additions, or improvements in
                           or to the storage area premises storing Customer's
                           FGI, as Plexus deems necessary for any reason. If for
                           the safety of the FGI Plexus is forced to relocate
                           Customer FGI, Customer agrees to allow Plexus access
                           to the FGI as needed and as required by Plexus.

                  g)       Stocking of FGI
                           Plexus shall stock FGI inventory in such a manner, in
                           Plexus' sole discretion, that is acceptable by the
                           Customer, and in Plexus' normal storage methods
                           relating to its engineering and manufacturing
                           services. Stocking requirements of customer may be
                           amended from time to time by mutual consent of both
                           parties and after a reasonable history of production
                           levels and/or demand is established. Shipments of FGI
                           inventory to the Customer's dock shall be handled in
                           the same manner as set forth in this Agreement. Such
                           inventory will remain the property of Plexus and
                           Plexus shall retain title and risk of loss to the FGI
                           until Customer issues a Purchase Order for such FGI
                           and Plexus invoices Customer for such FGI. Upon
                           issuance of Customer PO and invoice of FGI all title
                           and risk of loss shall be passed to the Customer.

Sitara Networks-Final Execution Comprehensive Professional Services Agreement

                                                                               8
<PAGE>   9
                  h)       Title and Risk of Loss related to FGI
                           Customer will assume all risk of loss or damage,
                           regardless of cause, to any of its property or any
                           property belonging to its employees upon transfer of
                           title and risk of loss of FGI to the Customer as
                           discussed previously. Plexus will at all times carry
                           adequate Worker's Compensation Insurance and such
                           appropriate insurance to cover its employees that are
                           mandated by federal or by state law of the state(s)
                           in which the employees perform work relating to
                           Customer's FGI. Plexus agrees to take all necessary
                           precautions to prevent injury or death to persons or
                           damage to property during the course of its
                           performance under this Agreement regarding Customer
                           FGI. However, Customer will maintain adequate risk of
                           loss, all, general liability, or other insurance, as
                           appropriate, for all FGI of which title and risk of
                           loss has been transferred to the Customer. Customer
                           shall name Plexus as additional insured, as evidenced
                           by a Certificate of Insurance, and evidencing such
                           policies, within thirty (30) days after execution of
                           this FGI Agreement and upon request by Plexus
                           thereafter.

                  i)       Quantity related to FGI
                           The FGI inventory and quantity of FGI to be
                           maintained by Plexus shall be mutually agreed upon
                           during the term of this Agreement and will be
                           specified by the purchase orders issued by the
                           customer to Plexus. Plexus may delete or discontinue
                           any type of FGI inventory from its storage area in
                           Plexus' facilities at any time, with sixty (60) days
                           prior written notice to Customer, or mutual written
                           agreement between the parties.

                  j)       Taxes related to FGI
                           Notwithstanding anything to the contrary, Customer
                           further agrees to and is responsible for the payment
                           of personal property taxes, or additional corporate
                           income taxes, if any, incurred by Plexus, on FGI
                           inventory sold to Customer resulting from the sale of
                           FGI. Customer further agrees to assist Plexus with
                           the reporting requirements of any personal property
                           or corporate income taxes upon Plexus' request, if
                           necessary.

                  k)       Plexus Personnel related to FGI
                           The storage area of Customer's FGI will be operated
                           by Plexus' personnel who will remain employees of
                           Plexus and on Plexus' payroll and will not be
                           considered employees of Customer. All of Plexus'
                           employees shall be subject to the reasonable rules
                           and regulations at any time promulgated by Plexus for
                           the safe, orderly, and efficient conduct of
                           operations of Customer's property. Customer shall
                           designate a specific managerial or person regarding
                           Customers FGI.

                  1)       UCC Filing related to FGI
                           Customer may, after prior written approval of Plexus,
                           and only after title and risk of loss has been
                           transferred to the Customer, file a Uniform
                           Commercial Code Form 1 (UCC-1), or any other UCC
                           form, as evidence of its title, or the creation of a
                           lien, of its inventoried FGI Product in Plexus'
                           facility, with any governing federal, state or city
                           agency or public records office, as necessary. Plexus
                           agrees to assist Customer, at Customer's sole
                           expense, with any necessary paperwork to secure such
                           notice of lien and/or evidence of title, as requested
                           by Customer.

         5. PRICING AND PAYMENT
         As full compensation for the assemblies provided by Plexus hereunder
         and its obligations contained herein, Customer will make payments
         subject to terms of net amount due twenty (20) days following the date
         of the invoice. Plexus and Customer will review the status of credit
         history on a regular basis, and, after sufficient credit history is
         established by the Customer, Plexus may amend payment terms at its sole
         discretion. Unless stated otherwise, prices quoted are F. 0. B. Plexus'
         manufacturing facility. Unless specifically stated otherwise, all
         quoted prices are firm for thirty (30) days from the date of quotation.
         Quotations are based on drawings, specifications, and other written
         information available to Plexus at the time of quotation. Any
         additional data supplied at the time of purchase may necessitate price
         adjustments. Any manufacturer's tax, retailer's occupation tax, use
         tax, sales tax, excise tax, or tax of any nature whatsoever imposed on
         or measured by the transaction between Plexus and Customer shall be
         paid by the Customer in addition to the prices quoted or invoiced. In
         the event Plexus is required to pay such tax, the Customer shall
         reimburse Plexus therefore, within ten (10) days of written demand by
         Plexus to the Customer for such reimbursement. If the transaction
         between

Sitara Networks-Final Execution Comprehensive Professional Services Agreement

                                                                               9
<PAGE>   10
         Plexus and the Customer is exempt from all such taxes, Customer shall
         provide Plexus with a tax exemption certification or other document
         acceptable to all taxing authorities at the time the order or contract
         is submitted.

         The parties further agree to the credit terms and conditions set forth
         in Attachment A, "Payment Terms", dated February 3, 2000, and attached
         hereto and made a part hereof. Plexus and Customer will review the
         status of credit history on a regular basis, and, after sufficient
         credit history is established by the Customer, Plexus will remove the
         credit restrictions set forth in Attachment A, "Payment Terms", and all
         business shall resume subject to the payment terms and provisions set
         forth in this Section 3 Payment, above.

         6. WARRANTY
         PLEXUS EXPRESSLY WARRANTS THE WORK AS SET FORTH HEREIN. PLEXUS MAKES NO
         OTHER WARRANTIES, EITHER EXPRESS OR IMPLIED (INCLUDING WITHOUT
         LIMITATION WARRANTIES AS TO MERCHANTABILITY OR FITNESS FOR PARTICULAR
         PURPOSES). IN ADDITION, THE FOLLOWING SHALL CONSTITUTE THE EXCLUSIVE
         REMEDIES FOR CUSTOMER FOR ANY BREACH BY PLEXUS OF ITS WARRANTIES
         HEREUNDER.

         Plexus warrants the assemblies against all defects in ) workmanship -
         where the assemblies do not conform to the agreed upon manufacturing
         specifications, for a period of fifteen (15) months from date of
         shipment, provided agreed upon testing is conducted by Plexus prior to
         shipment, except as set forth below. If the materials (components)
         furnished contains a manufacturer's warranty, Plexus hereby extends, to
         the extent possible, such Component Manufacturers' warranty to
         Customer. Plexus shall repair or replace, at Plexus' option and free of
         charge, any portion of the assemblies which is returned to Plexus'
         factory securely packaged, insured and with freight pre-paid within the
         warranty period, and which upon examination Plexus determines in its
         sole discretion to be defective in workmanship. Plexus will return the
         repaired or replaced assemblies to customer with freight pre-paid.

         Plexus is responsible for determining root cause of any defective
         assemblies, and will work with Customer and material supplier to
         develop corrective actions. Customer and Plexus will work cooperatively
         in pursuing corrective action if a third party is determined to cause
         failures. In the event Customer and Plexus are unable to reach an
         agreement for a resolution of a deficiency caused by a third party,
         then Plexus will recommend the final solution and/or corrective action
         plan to remedy any defect caused by such third party. Plexus will allow
         Customer to participate in any discussions with such third party as
         requested.

         This Warranty does not apply to:

                  a)       Design deficiencies. Plexus expressly disclaims any
                           warranty responsibility for design deficiency, and
                           for infringement for the like.

                  b)       Any modifications and/or alterations made to the
                           Assemblies, or any portion thereof, without the
                           express written authorization of Plexus obtained in
                           advance. If this is the case, all warranties made
                           herein are invalid and Customer shall have no further
                           remedies hereunder against Plexus.

                  c)       Any defect, loss or damage resulting from theft,
                           loss, fire, misuse, abuse, negligence, vandalism,
                           acts of God, accident, casualty, power failures or
                           surges, alteration, modification or failure to follow
                           installation, operation or maintenance instructions,
                           or any other cause beyond Plexus' reasonable control.

                  d)       Any defect, unless written notice of the defect is
                           given by the Customer to Plexus as soon as practical
                           after the defect first appears. The right to make a
                           claim under this warranty expires fifteen (15) months
                           from the date of shipment. Actions taken by Plexus to
                           correct any defect shall not extend beyond this
                           period.

                  e)       Components incorporated into the assemblies.

         IN NO EVENT, REGARDLESS OF CAUSE, SHALL PLEXUS BE LIABLE FOR
         INCIDENTAL, INDIRECT, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSSES OF
         ANY KIND, WHETHER IN CONTRACT OR IN TORT, ARISING FROM ITS PERFORMANCE
         UNDER THIS AGREEMENT.

Sitara Networks-Final Execution Comprehensive Professional Services Agreement

                                                                              10
<PAGE>   11
         7. TEST EQUIPMENT
         Unless otherwise noted, any test equipment quoted herein is warranted
         to be free from defects in material and workmanship for a period of one
         (1) year from the date of certification. After the warranty period the
         equipment will be repaired on a time and materials basis. Labor will be
         charged at the current billing rate. Parts will be charged at cost plus
         markup. Travel expenses will be added to any repairs including travel
         between Plexus and/or one of its affiliates. All dedicated test/burn in
         fixtures will be progress billed monthly up to 95% of the program cost.
         The remaining 5% is due upon fixture certification.

         8. DOCUMENTATION
         The Customer is responsible for supplying Plexus with complete
         documentation. This includes, at a minimum, (three) 3 complete and
         current sets of documentation including, at a minimum, all prints,
         softwares, artwork, and bill of materials with manufacturer and part
         number, and any specifications, including test specializations or
         procedure, called for on any customer prints. It is the Customer's
         responsibility to assure that Plexus receives timely notification of
         any changes to the documentation, and updated prints reflecting the
         changes.

         9. TOOLING
         All tooling produced or obtained for the assemblies delivered hereunder
         and paid for by Customer shall become and remain the property of
         Customer at the time payment in full is received for the tooling by
         Plexus. Such tooling shall be used by Plexus only for the benefit of
         Customer, and shall be delivered to Customer upon request. If Customer
         requests the return of any tooling from Plexus and Plexus determines
         the return of such tooling prevents Plexus from providing the
         assemblies to Customer, then Plexus shall inform Customer in writing,
         and Customer and Plexus shall negotiate a mutually acceptable
         resolution.

         Customer, at its sole discretion, may consign to Plexus, items,
         including, but not limited to, materials and/or equipment relating to
         the production and/or testing of the assemblies at Plexus' location.
         The material and/or equipment shall be utilized by Plexus only for the
         production and/or testing of the assemblies. Customer shall assist
         Plexus in installing the materials and/or equipment and shall provide
         training and maintenance instructions, if requested by Plexus or
         required by Customer. Customer shall be responsible for repairing,
         upgrading, replacing and/or maintaining the materials and/or equipment
         consigned to Plexus. However, Plexus shall provide routine maintenance.

         All tooling quoted herein is quoted at the cost to Plexus from its
         suppliers. A charge of 10% will be added to all tooling with a cost of
         less than $5,000, and a 5% charge added to all tooling with a cost of
         $5,000 or greater.

         10. TERMINATION AND CANCELLATION OF MANUFACTURING PHASE
         During the Manufacturing Phase, either party shall have the right to
         terminate any or all activities under this agreement for any reason and
         at any time upon ninety (90) days prior written notice to the other
         party. Plexus agrees to immediately terminate the specified activity
         pursuant to this Agreement upon termination or cancellation. If this
         entire Agreement is terminated, all existing Customer POs shall be
         deemed to have been canceled unless otherwise specified by Customer.
         Customer agrees to reimburse Plexus for unrecovered expenses. In
         addition, Customer and Plexus shall negotiate a settlement of charges,
         if any, for reasonable and allowable expense directly incurred by
         Plexus including, but not limited to, manufacturing process ramp down
         costs and packaging and transportation costs and expenses, and the
         return to Customer of any Customer owned material(s), tools, equipment
         and/or any other related items, consistent with Section B2, above.

         If this entire agreement is terminated, then Plexus shall:

                  a)       Deliver to Customer all completed assemblies which
                           conform to the applicable and then current
                           specifications and requirements; and

                  b)       Return to Customer, at Customer's expense, all
                           tooling, equipment, Components and/or Long Lead Time
                           Components, drawings, specifications, documentations
                           and supplies that are owned by Customer pursuant to
                           the Agreement; and

                  c)       Prepare and submit to Customer an itemized document
                           to include the quantity of assemblies in the
                           production process.

Sitara Networks-Final Execution Comprehensive
Professional Services Agreement                                               11
<PAGE>   12
         Upon such termination, all existing Customer POs shall be deemed to
         have been canceled unless otherwise specified by Customer and Customer,
         agrees to reimburses Plexus for unrecovered expenses, consistent with
         section B2, above.

C. STANDARD TERMS AND CONDITIONS
The terms and conditions set forth in this Section C, Standard Terms and
Conditions shall be applicable to Product Development and Prototype Phase, and
Manufacturing Phase of this Agreement.

         1. MUTUAL COOPERATION
         Plexus represents that it will pursue the Agreement to the best of its
         ability and in the best interest of the Customer, and the Customer
         represents that it will cooperate with Plexus in reaching the
         objectives of the Agreement. Plexus will appoint a project manager that
         is acceptable at al times with Customer for the duration of the
         Agreement and will require the Customer to establish one person to
         coordinate all activities through. In the event that the project
         manager is not operating in the best interest of the Customer, the
         Customer shall contact Plexus to discuss Agreement related concerns
         and/or complaints.

         2. CONFIDENTIAL INFORMATION
         Plexus and the Customer will use best efforts to prevent the disclosure
         of any confidential information, unless specifically instructed
         otherwise in writing by the disclosing party, and excepting in such
         instances where Plexus may be compelled by law to make disclosures. The
         mechanisms for controlling and processing confidential information may
         be covered under a separate Confidential Disclosure Agreement (if
         required).

         3. FORCE MAJEURE
         Plexus shall not be liable for any delay in or failure of performance
         under this agreement due to any contingency beyond Plexus' control,
         including, but not limited to, an act of God, war, insurrection, fire,
         riot, strike or labor dispute, sabotage, act of public enemy, flood,
         storm, accident, equipment failure, inability to obtain suitable or
         sufficient labor or material, laws or regulations, or any other cause
         beyond its reasonable control.

         4. INTELLECTUAL PROPERTY RIGHTS
         All patents, copyrights, trademarks, or other rights pertaining to
         inventions, developments, or improvements made in the course of the
         work, and funded by the Customer, are the property of Customer. Plexus
         will, upon written direction from Customer, execute any and all papers
         and documents prepared or submitted by Customer as may be reasonably
         required to transfer or secure to Customer full title and authority
         over such rights. Plexus will be compensated by Customer for time and
         expense as incurred in this obligation at the then current billing
         rates for those of its employees necessary for these purposes.

         Customer agrees that it shall assume all responsibility for determining
         whether the assemblies to be designed and assembled infringe an any
         patent, copyright or trademark, and Customer shall indemnify and hold
         harmless Plexus from any liability, including legal costs and expenses,
         damages and attorney fees arising from any claim demand or suit,
         including a claim by Customer, based on allegations or claims that the
         assemblies or any design, patent, copyright, or trademark sought to be
         obtained or obtained by Customer as a result of this agreement
         constitutes an infringement of any patent, trademark or copyright of
         the United States or any foreign county.

         In the event any such claim or suit is asserted or instituted against
         Plexus, Plexus shall promptly notify Customer of the assertion of any
         such allegation or claim. Customer shall thereupon assume
         responsibility for and conduct the defense of each assertion or suit at
         its expense, and reasonable information and assistance for the defense
         of same shall be provided by Plexus for which Plexus will be
         compensated for time and expenses at its then current billing rate.
         Plexus shall have the right, at its expense, to be represented in the
         defense of any such assertion or suit by counsel of its own selection.

         The prices quoted do not include, unless specifically stated otherwise,
         the cost for testing and/or submittals for assembly approvals or any
         annual file maintenance fee, such as for UL, VDE, CSA or FCC. Plexus
         will assist Customer in obtaining such approvals and charge for same
         services at Plexus' current hourly billing rate.

Sitara Networks-Final Execution Comprehensive
Professional Services Agreement                                               12
<PAGE>   13
         However, if Plexus has done the initial design for Customer, they agree
         to use design practices that conform with all standard industry agency
         requirements.

         5. LIABILITY AND INDEMNIFICATION
         Plexus will use its discretion to pursue the Agreement in the best
         interest of Customer. Plexus will be under no liability to Customer or
         otherwise for its choice of methods employed, the character or tests
         and experiments performed, the results obtained, nor for the use which
         shall thereafter be made by Customer of such results. IT IS UNDERSTOOD
         THAT OTHER THAN THE WARRANTY SET FORTH IN SECTION B4, NO OTHER
         GUARANTEES OR WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, ARE GIVEN BY
         PLEXUS, INCLUDING, BUT NOT LIMITED TO ANY WARRANTIES OF MERCHANTABILITY
         OR FITNESS FOR A PARTICULAR PURPOSE. PLEXUS SHALL NOT BE LIABLE FOR ANY
         INDIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES (INCLUDING LOST PROFITS)
         SUSTAINED OR INCURRED IN CONNECTION WITH THIS AGREEMENT.

         Customer will fully indemnify and hold harmless Plexus from any and all
         liability, claims demands, costs and expense arising out of the use,
         publication, and/or marketing of the results of Plexus' efforts, the
         functioning of the assemblies or the product(s) which they are a pan
         of, or any other matter resulting from Plexus' performance under this
         Agreement, whether such liability, claims or demands be in the nature
         of patent, trademark or copyright infringement, public or product
         liability, contract liability, or otherwise during or following the
         terms of this Agreement, and Customer shall, at its own expense, defend
         any and all such actions based thereon and shall pay all attorney's
         fees and cost and other expenses arising therefrom.

         Plexus will not be liable for errors, or expenses which may be incurred
         in its performance of this work which results from the engineering
         and/or design of the Assemblies, or from Plexus' reliance upon
         information, technological records, sketches, drawings, or prototypes
         furnished by Customer or Customer's design engineering firm. Customer
         will forthwith, during the term of this Agreement, notify Plexus of any
         and all information, technology changes, or other facts relevant to any
         aspect or phase of the Agreement.

         6. ARBITRATION
         All rights and remedies conferred by this Agreement, by any other
         instrument, or by law are cumulative and may be exercised singularly or
         concurrently. If any provision of this Agreement is held by any court
         or governmental agency to be invalid, such invalidity shall not affect
         the enforceability of any other provision(s) hereof. This Agreement and
         any Purchase Orders issued hereunder shall be governed by and
         interpreted in accordance with the laws of the Commonwealth of
         Massachusetts. Unless otherwise agreed to in writing by the parties,
         any controversy or claim arising out or relating to this Agreement, or
         the parties' decision to enter into this Agreement, or the breach
         thereof, shall be settled by arbitration through the American
         Arbitration Association and in accordance with the Commercial
         Arbitration Rules of the American Arbitration Association. The
         arbitration proceeding shall be conducted and presided over by a single
         neutral arbitrator chosen pursuant to American Arbitration Association
         procedures. Decision of the arbitrator shall be final, binding, and not
         subject to appeal or review; provided that, either party may request
         that the arbitrator review and reconsider his or her decision, in whole
         or in part. Judgment upon the award rendered by the arbitrator may be
         entered in any court having jurisdiction thereof. The arbitration shall
         be held in Boston, Massachusetts and the arbitrator shall apply the
         substantive law of Commonwealth of Massachusetts except that the
         interpretation and enforcement of this arbitration provision shall be
         governed by the federal Arbitration Act. The arbitrator shall not award
         either party punitive damages and the parties shall be deemed to have
         waived any right to such damages.

         7. CONSENT TO JURISDICTION AND APPLICABLE LAW
         The parties hereby irrevocably submit to the jurisdiction of the courts
         of the Commonwealth of Massachusetts in any action or proceeding
         arising out of or relating to this Agreement, and the parties hereby
         irrevocably agree that all claims in respect of such action or
         proceeding may be determined by such courts. The parties hereby waive,
         to the fullest extent possible, the defense of an inconvenient forum to
         the maintenance of such action or proceeding, and the parties agree
         that a final judgement in any action or proceeding shall be conclusive
         and may be enforced in other jurisdictions by suit on the judgement or
         in any other matter provided by law.

         The parties hereby agree that this Agreement shall be governed by and
         will be construed in accordance with the laws of the State of
         Wisconsin, irrespective of the conflicts of laws provisions thereof.

Sitara Networks-Final Execution Comprehensive
Professional Services Agreement                                               13
<PAGE>   14
         8. NO RECRUITING
         Plexus and the Customer agree that during the term of this program and
         for twelve (12) months thereafter, it shall not solicit or recruit
         (even though professional recruiters) the employees of the other. This
         shall not preclude an employee of either Plexus or the Customer from
         independently pursuing and securing employment opportunities with the
         other on such employee's own initiative.

         9. ENTIRE AGREEMENT
         This Agreement, along with the proposal, and Confidential Disclosure
         Agreement and/or quotation (if any) and Plexus' invoices, contains the
         entire understanding of the parties pertaining to the subject matter
         hereof, and no other agreements, oral or otherwise, shall be deemed to
         exist or to bind the parties. Notwithstanding anything to the contrary
         contained herein, the parties hereto agree that the terms and
         conditions set forth herein and in Plexus' invoices, proposal and
         Confidential Disclosure Agreement (if any), shall supersede any and all
         terms and conditions submitted by the Customer in any document,
         including but not limited to any terms and conditions contained in the
         Customer's purchase order. This agreement may not be modified or
         terminated orally, and no claimed modification, termination, or waiver
         shall be binding unless in writing and signed by both parties.

         Accepted and agreed to:

         SITARA NETWORKS, INC.                    PLEXUS CORP.

                                                  ENGINEERING AUTHORIZATION:

         By:  /s/ Michael S. Palin               By:  /s/ [Illegible]
              -------------------------------         --------------------------
         Title: Chief Financial Officer          Title: Executive Vice President
                -----------------------------           / Tech. Group
                                                        ------------------------
         Date:  7/25/00                          Date:  7/19/00
                -----------------------------           ------------------------


                                                 MANUFACTURING AUTHORIZATION

         By:  /s/ Susan E. Fennell               By:  /s/ Chuck Williams
              -------------------------------         --------------------------
         Title: Director-Material Operations    Title:  Vice President
                -----------------------------           ------------------------
         Date:  7/25/00                          Date:  7/19/00
                -----------------------------           ------------------------


Sitara Networks-Final Execution Comprehensive
Professional Services Agreement                                               14
<PAGE>   15
                              [PLEXUS LETTERHEAD]

                                  ATTACHMENT A
                                  PAYMENT TERMS

December 13, 1999

Ms.  Susan Fennell
Sitara Networks, Inc.
60 Hickory Drive
Waltham, MA 02451


Dear Susan:

I was requested to outline the information that Plexus Electronic Assembly will
require in order to finalize the credit arrangement between Sitara Networks, Inc
and Plexus Electronic Assembly Corporation. Along with the following
information, a standard credit application, including trade and bank references
will need to be completed.

         1)   Sitara Networks will provide to Plexus Electronic Assembly,
              monthly confirmation of the available cash balances under Sitara's
              control. Such confirmation shall be from the bank or investment
              firm in which the funds are held. This information should be
              forwarded to me by the 10th day following each month-end.

         2)   Sitara Networks will provide to Plexus Electronic Assembly written
              confirmation that there are no restrictions against the use of
              Sitara's existing cash balances and, that there is no outside
              control of the use of these funds. A list of individuals
              authorized to disburse these funds should be included.

         3)   Sitara will provide quarterly financial statements to Plexus
              Electronic Assembly for review. Statements will be provided within
              20 working days after the close of each quarter. All information
              will be strictly confidential and for internal use only.

         4)   Sitara will provide cash deposits to cover all exposure created by
              Plexus Electronic Assembly purchase orders for non-cancelable /
              non-returnable material.

         5)   Initially, all products produced for Sitara will be invoiced after
              completion and transfer to finished goods. These goods will become
              the property of Sitara Networks, and Sitara will take title and
              insurability at that point.

         6)   Invoice terms will be NET 30 days from invoice date, via wire
              transfer. Payment to be received by Plexus Electronic Assembly on
              the 30th day.
<PAGE>   16
December 13, 1999
Page Two


         7)   An initial credit limit of S400,000 has been established for
              accounts receivable. If in the course of business this initial
              limit is exceeded, you will be contacted and may be required to
              pay some invoices before the NET 30 day term so as to remain
              within the limit. Any increase in the limit will be based upon
              length and status of credit history.

I thank you, in advance, for your cooperation in working to establish credit
standards, and look forward to a mutually beneficial relationship between our
two companies. If you have any questions or concerns, please contact me directly
at (920) 751-3625.

Sincerely,

/s/ Marty Verstegen

Marty Verstegen,
Controller
Plexus Electronic Assembly

Cc:      Bob Kronser, Vice President, Sales and Marketing - Plexus Corp.




                                  [PLEXUS LOGO]

                         The Product Realization Company
<PAGE>   17
                                  ATTACHMENT B

                      FLEXIBILITY PERCENTAGES PER ASSEMBLY

To be determined at a later date by mutual agreement between the parties.

Customer:   /s/ MSP / 7/25/00                  Plexus:   /s/ CW / 7/19/00
            -----------------                            ----------------
            Initial/Date                                 Initial/Date
<PAGE>   18
                                  ATTACHMENT C

                             REPORTING REQUIREMENTS

To be determined at a later date by mutual agreement between the parties.

Customer:   /s/ MWP / 7/25/00                  Plexus:   /s/ CW / 7/19/00
            -----------------                            ----------------
            Initial/Date                                 Initial/Date
<PAGE>   19
                                  ATTACHMENT D

                                  PRICING MODEL

To be determined at a later date by mutual agreement between the parties.

Customer:   /s/ MWP / 7/25/00                  Plexus:   /s/ CW / 7/19/00
            -----------------                            ----------------
            Initial/Date                                 Initial/Date