Document:

<PAGE>   1

                                   EXHIBIT 4.4

                      FOURTH AMENDMENT TO BROOKTROUT, INC.
                      1992 STOCK INCENTIVE PLAN, AS AMENDED

     This Fourth Amendment (the "Fourth Amendment") to the Brooktrout, Inc. (the
"Company") 1992 Stock Incentive Plan, dated August 17, 1992, as amended to date
(the "Incentive Plan"), was adopted by the Board of Directors (the "Board") of
the Company on March 7, 2000.

WHEREAS, the Board approved and adopted, subject to stockholder approval, the
amendment to increase by eight hundred thousand (800,000) the maximum number of
shares of common stock, $.01 par value per share (the "Stock"), reserved and
available for issuance under the Incentive Plan, from three million four hundred
and seventy-five thousand (3,475,000) to four million two hundred and
seventy-five thousand (4,275,000); and

WHEREAS, on May 11, 2000, the stockholders of the Company approved the amendment
at the annual meeting of stockholders;

NOW, THEREFORE, the Incentive Plan is hereby amended in the following manner:
The first sentence of Section 3 clause (a) is amended to increase the maximum
number of shares of Stock reserved and available for issuance under the
Incentive Plan from three million four hundred and seventy-five thousand
(3,475,000) to four million two hundred and seventy-five thousand (4,275,000).

                                       8<PAGE>   1

                                   EXHIBIT 4.7

                      SECOND AMENDMENT TO BROOKTROUT, INC.
                  AMENDED AND RESTATED 1992 STOCK PURCHASE PLAN

     This Second Amendment (the "Second Amendment") to the Brooktrout, Inc. (the
"Company") Amended and Restated 1992 Stock Purchase Plan, dated August 17, 1992
(the "Purchase Plan"), was adopted by the Board of Directors (the "Board") of
the Company on March 7, 2000.

WHEREAS, the Board approved and adopted, subject to stockholder approval, the
amendment to increase by seventy-five thousand (75,000) the maximum number of
shares of common stock, $.01 par value per share (the "Stock"), reserved and
available for issuance under the Purchase Plan, from two hundred and twelve
thousand five hundred (212,500) to two hundred and eighty-seven thousand five
hundred (287,500); and

WHEREAS, on May 11, 2000, the stockholders of the Company approved the amendment
at the annual meeting of stockholders;

NOW, THEREFORE, the Purchase Plan is hereby amended in the following manner: The
second sentence of the first paragraph is amended to increase the number of
shares of Stock reserved and available for purchase under the Purchase Plan from
two hundred and twelve thousand five hundred (212,500) to two hundred and
eighty-seven thousand five hundred (287,500).

                                       9<PAGE>   1
                                                                    EXHIBIT 10.1

                SIXTH AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

         AGREEMENT, made as of the 16th day of June, 2000, by and among Sitara
Networks, Inc., a Delaware corporation (the "Company"), Malik Z. Khan (the
"Founder"), Manickam Sridhar, Sylvain Louchez (collectively, the "Employee
Stockholders") and the persons or entities named as Investors on the signature
page(s) hereto (each, an "Investor").

         WHEREAS, the Company (formerly known as K2 Net, Inc.), the Founder, the
Employee Stockholders and certain of the Investors are parties to a Fifth
Amended and Restated Stockholders Agreement dated as of January 14, 2000 (the
"Existing Stockholders Agreement");

         WHEREAS, the Founder and his Permitted Transferees (as hereafter
defined) are holders of an aggregate 4,500,000 shares of common stock, $0.00001
par value, of the Company (the "Common Stock");

         WHEREAS, certain of the Investors acquired an aggregate of 6,470,589
shares of Series A Convertible Preferred Stock, $0.00001 par value, of the
Company (the "Series A Preferred Stock") from the Company pursuant to the terms
of a Series A Convertible Preferred Stock Purchase Agreement dated December 11,
1996 between the Company and the Investors (the "Purchase Agreement");

         WHEREAS, certain Investors acquired an aggregate of 5,000,000 shares of
Series B Convertible Preferred Stock, $0.00001 par value, of the Company (the
"Series B Preferred Stock") from the Company pursuant to the terms of a Series B
Convertible Preferred Stock Purchase Agreement dated September 9, 1997 between
the Company and certain Investors (the "Series B Purchase Agreement");

         WHEREAS, certain Investors acquired an aggregate of 1,312,336 shares of
Series C Convertible Preferred Stock, $0.00001 par value, of the Company (the
"Series C Preferred Stock") from the Company pursuant to the terms of a Series C
Convertible Preferred Stock Purchase Agreement dated May 18, 1998 between the
Company and certain Investors (the "Series C Purchase Agreement")

         WHEREAS, Intel Corporation acquired an aggregate of 787,402 shares of
Series D Convertible Preferred Stock, $0.00001 par value, of the Company (the
"Series D Preferred Stock") from the Company pursuant to the terms of a Series D
Convertible Preferred Stock Purchase Agreement dated December 17, 1998 between
the Company and Intel Corporation (the "Series D Purchase Agreement");

         WHEREAS, certain Investors acquired an aggregate of 5,722,903 shares of
Series E Convertible Preferred Stock, $0.00001 par value, of the Company (the
"Series E Preferred Stock") from the Company pursuant to the terms of a Series E
Convertible Preferred Stock Purchase Agreement dated July 9, 1999 between the
Company and certain Investors (the "Series E Purchase Agreement");

<PAGE>   2

         WHEREAS, certain Investors acquired an aggregate of 1,110,000 shares of
Series F Convertible Preferred Stock, $0.00001 par value, of the Company (the
"Series F Preferred Stock") from the Company pursuant to the terms of a Series F
Convertible Preferred Stock Purchase Agreement dated January 14, 2000 between
the Company and certain Investors (the "Series F Purchase Agreement");

         WHEREAS, certain Investors acquired an aggregate of up to 4,650,000
shares of Series G Convertible Preferred Stock, $0.00001 par value, of the
Company (the "Series G Preferred Stock") from the Company pursuant to the terms
of a Series G Convertible Preferred Stock Purchase Agreement dated as of the
date hereof between the Company and certain Investors (the "Series G Purchase
Agreement")

         WHEREAS, the parties to the Existing Stockholders Agreement who hold a
sufficient number of Shares (as hereinafter defined) to amend the Existing
Stockholders Agreement in accordance with the provisions of Section 14 thereof
and the Investors who are parties to the Series G Purchase Agreement desire to
amend and restate in its entirety the Existing Stockholders Agreement; and

         WHEREAS, it is a condition to the obligations of the Investors under
the Series G Purchase Agreement that this Agreement be executed by the parties
hereto, and the parties are willing to execute this Agreement and to be bound by
the provisions hereof;

         NOW, THEREFORE, in consideration of the foregoing, the agreements set
forth below, and the parties' desire to provide for continuity of ownership of
the Company to further the interests of the Company and its present and future
stockholders, the parties hereby agree with each other to amend and restate the
Existing Stockholders Agreement in its entirety as follows:

         1. Certain Defined Terms. As used in this Agreement, the following
terms shall have the following respective meanings:

                  (a) "Qualified Public Offering" shall mean and include the
         closing of a firmly underwritten public offering pursuant to an
         effective registration statement under the Securities Act of 1933, as
         amended, covering the offer and sale of Common Stock for the account of
         the Company from which the aggregate net proceeds to the Company are at
         least $15,000,000 and the price per share of such Common Stock is not
         less than $9.77 (such amount to be equitably adjusted whenever there is
         a stock split, combination, stock dividend, reclassification or similar
         event affecting the Common Stock).

                  (b) "Preferred Stock" shall mean the Series A Preferred Stock,
         the Series B Preferred Stock, the Series C Preferred Stock, the Series
         D Preferred Stock, the Series E Preferred Stock, the Series F Preferred
         Stock and the Series G Preferred Stock.

                  (c) "Shares" shall mean and include all shares of Stock now
         owned or hereafter acquired by a Stockholder or an Investor.

                  (d) "Stock" shall mean and include all shares of Common Stock,
         and all other securities of the Company which may be issued in exchange
         for or in respect of shares of

                                      -2-
<PAGE>   3

         Common Stock (whether by way of stock split, stock dividend,
         combination, reclassification, reorganization, or any other means).
         Stock owned by an Investor shall also mean and include all of the Stock
         which an Investor has the right to acquire from the Company upon the
         conversion, exercise or exchange of any Preferred Stock, warrants or
         other securities of the Company then owned by such Investor.

                  (e) "Stockholder" shall mean the Founder, the Employee
         Stockholders and each additional person or entity, other than an
         Investor or any transferee of an Investor, who or which shall acquire
         Stock from the Company and shall execute an Instrument of Adherence in
         the form of Exhibit A hereto pursuant to the provisions of Section 2
         hereof.

                  (f) "Unvested Shares" shall mean the shares of Common Stock
         now or hereafter owned by the Founder and which are subject to
         repurchase on certain events as set forth in Section 7 hereof.

                  (g) "Vested Shares" shall mean the shares of Common Stock now
         or hereafter owned by the Founder which are not, or no longer subject
         to, repurchase in accordance with the provisions of Section 7 hereof.

         2. Additional Stockholders. The Company agrees that it will not, so
long as this Agreement is in effect, issue any shares of Common Stock to any
person, firm or entity, other than shares of Common Stock issued to any Investor
or any transferee of an Investor, upon conversion of any Preferred Stock, unless
such person or entity executes an Instrument of Adherence in the form of Exhibit
A hereto, and upon execution thereof, such person or entity shall be deemed to
be a Stockholder hereunder for all purposes and all shares of Common Stock held
by such Stockholder shall be subject to all the provisions of this Stockholders
Agreement; provided, however, that this Section 2 shall not apply to Common
Stock issued to an employee where the aggregate number of shares owned by such
employee is less than one half of one percent (.50%) of the total outstanding
capital of the Company.

         3. Prohibited Transfers. No Stockholder shall sell, assign, transfer,
pledge, hypothecate, mortgage, encumber or dispose of all or any of his Shares
except to the Company or as expressly provided in this Agreement, and in no
event, without limitation, may the Founder sell, assign, transfer, pledge,
hypothecate, mortgage, encumber or dispose of any of his Unvested Shares.
Notwithstanding the foregoing, any Stockholder may transfer all or any of his
Shares, other than any Unvested Shares (i) by way of gift to any member of his
family (i.e., spouse, sibling, spouse's sibling, child (natural or adopted),
stepchild, grandchild, uncle, aunt, niece, nephew, parent, grandparent or any
other lineal ancestor or descendant) or to any trust, partnership or limited
liability company for the benefit of, or the ownership interests of which are
wholly owned by, any such family member or such Stockholder (each, a "Permitted
Transferee"), provided that any such Permitted Transferee shall execute an
Instrument of Adherence, as a condition to such transfer, to be bound by all of
the provisions of this Agreement to the same extent as if such Permitted
Transferee were the Stockholder, (ii) by will or the laws of descent and
distribution to or for the benefit of a Permitted Transferee or (iii) to a
Permitted Transferee of a Stockholder, in any of which event each such Permitted
Transferee shall be bound by all of the provisions of this Agreement to the same
extent as if such Permitted

                                      -3-
<PAGE>   4
 Transferee were the Stockholder, and in each case each such Permitted
Transferee shall execute an Instrument of Adherence in the form of Exhibit A
hereto, as a condition to transfer of such Stock to such Permitted Transferee.

         4. Right of First Refusal on Dispositions.

                  (a) If at any time any Stockholder desires to sell for cash
         and/or promissory notes all or any part of his, her or its Shares
         (other than any Unvested Shares) pursuant to a bona fide written offer
         from a third party (the "Proposed Transferee"), such Stockholder (the
         "Selling Stockholder") shall submit a written offer (the "Offer") to
         sell such Shares (the "Offered Shares") to the Company and the
         Investors and the Founder on terms and conditions, including price, not
         less favorable than those on which the Selling Stockholder proposes to
         sell such Offered Shares to the Proposed Transferee. The Offer shall
         disclose the identity of the Proposed Transferee, the Offered Shares
         proposed to be sold, the total number of Shares owned by the Selling
         Stockholder, the terms and conditions, including price, of the proposed
         sale, and any other material facts relating to the proposed sale and
         shall include a copy of the Offer to purchase from the Proposed
         Transferee. The Offer shall further state that the Company and the
         Investors and the Founder may acquire, in accordance with the
         provisions of this Agreement, any or all of the Offered Shares for the
         price and upon the other terms and conditions, including deferred
         payment (if applicable), set forth therein (and the Offer shall specify
         that, if the Company does not communicate in writing its election to
         purchase any or all of the Offered Shares, within twenty (20) days of
         the date the Offer was delivered to the Company, the Investors and the
         Founder shall thereafter have the right to purchase some or all of the
         remaining Offered Shares).

                  (b) If the Company does not elect to purchase all or part of
         the Offered Shares, then each other party having a right of purchase
         herewith and who desires to purchase any or all of the Offered Shares
         not purchased by the Company shall communicate in writing its election
         to purchase to the Selling Stockholder on the terms and conditions set
         forth in the Offer (with a copy to the Company and each Investor and
         the Founder), which communication shall be delivered in person or
         mailed to the Selling Stockholder at the address set forth in
         accordance with Section 4 below within thirty (30) days of the date the
         Offer was delivered to the Company, the Investors and the Founder. Such
         communications, when taken in conjunction with the Offer, shall be
         deemed to constitute valid, legally binding and enforceable
         agreement(s) for the sale and purchase of such Offered Shares.

                  (c) If the Selling Stockholder receives any communications
         pursuant to Section 4(a) or Section 4(b), the Selling Stockholder shall
         sell the Offered Shares to each party from whom he has received notice
         as follows:

                           (i) If a communication has been received from the
                  Company, the Selling Stockholder shall sell to the Company
                  such amount of the Offered Shares as are set forth in such
                  communication; and

                                      -4-
<PAGE>   5

                           (ii) If a communication has been received from one or
                  more of the Investors and the Founder, the Selling Stockholder
                  shall next sell to such of the Investors and the Founder from
                  whom communication has been received (the "Participating
                  Holders") on a pro rata basis, (provided that each
                  Participating Holder shall have a right of oversubscription
                  such that if any Participating Holder fails to accept the
                  Offer as to all or a portion of its pro rata share, the other
                  Participating Holders shall have the right to purchase up to
                  the balance of the Offered Shares not so purchased on a pro
                  rata basis, or the Participating Holders may elect to purchase
                  the Offered Shares in such other proportions as they may
                  determine) such amount of the Offered Shares as were not sold
                  to the Company and as are set forth in such notices or other
                  instructions from the Participating Holders.

                  (d) The sale of the Offered Shares shall occur forty-five (45)
         days following the date on which the Offer was delivered to the
         Company, the Investors and the Founder or, if the Company shall not be
         open for business on such date, on the next succeeding business day.
         All sales of the Offered Shares shall occur contemporaneously. Such
         sales shall be effected by the Selling Stockholder's delivery to the
         Company, and/or the Participating Holders as applicable, of
         certificates evidencing the Offered Shares to be purchased by them,
         duly endorsed for transfer, against payment to the Selling Stockholder
         of the purchase prices therefor by the Company or the Participating
         Holders as applicable.

                  (e) If the Company and the Stockholders do not elect to
         purchase all of the Offered Shares, the remaining Offered Shares may be
         sold by the Selling Stockholder at any time within ninety (90) days
         after the date the Offer was accepted, rejected or lapsed pursuant to
         Section 4(b) above, subject to the provisions of Section 5. Any such
         sale shall be to the Proposed Transferee and at not less than the price
         and upon other terms and conditions, if any, not more favorable to the
         Proposed Transferee than those specified in the Offer. Any Offered
         Shares not sold within such ninety (90) day period shall continue to be
         subject to the requirements of a prior offer pursuant to this Section
         4.

                  (f) The rights of first refusal provided in this Section 4
         shall not apply with respect to sales, transfers or exchanges of Shares
         to the Company or in conjunction with the sale of the Company to an
         unaffiliated third party whether by merger, consolidation or sale of
         stock in a transaction in which the Investors' Shares are also sold or
         transferred or eligible to be sold or transferred (herein, a "Sale of
         the Company").

                  (g) For purposes of determining a party's pro rata share under
         this Agreement, all calculations shall be made based on the number of
         Shares then held by all Stockholders and Investors, as applicable, and
         calculated (i) on the basis that all shares of Preferred Stock then
         held by any party were converted on the date of any notice into the
         largest whole number of shares of Common Stock into which such shares
         of Preferred Stock were then convertible, and (ii) treating all Shares
         subject to vesting, options and warrants held by any party as
         outstanding and held by such parties on the date of any notice.

                                      -5-
<PAGE>   6

                  (h) If a Stockholder is subject to a transfer of his, her or
         its Shares by any bankruptcy or insolvency law or proceeding, any
         divorce proceeding or otherwise by operation of law (other than by
         death), or if any transfer of Shares is made or attempted contrary to
         the provisions of this Agreement, the Company, the Investors and the
         Founder (unless he or any of his Permitted Transferees is the
         Stockholder) will have the right to purchase any or all of such Shares
         from the Stockholder, his, her or its legal representative or his, her
         or its transferees at any time before or after the transfer, at the
         price, if any, paid for or proposed to be paid for such Shares or for
         Fair Market Value as determined under Section 4(i), whichever is less,
         on the same terms, conditions, order of purchase and procedures set
         forth in Sections (b), (c) and (d) hereof.

                  (i) "Fair Market Value" shall mean (i) the fair market value
         of the assets of the Company and its subsidiaries on a consolidated and
         combined basis. including cash, property, intellectual property, and
         goodwill, determined on a going concern basis as of the date of the
         Communication (as defined below), plus the aggregate exercise prices of
         all options, warrants and other convertible securities, minus the sum
         of (x) all liabilities of the Company reflected on the Company's most
         recent monthly financial statements, plus (y) without duplication, the
         liquidation value of any outstanding Preferred Stock, including accrued
         but unpaid dividends thereon at the time of the Notice: divided by (ii)
         the aggregate number of shares of Common Stock then outstanding plus
         the aggregate number of shares of Common Stock issuable upon exercise
         of all options, warrants and other convertible securities (other than
         the Preferred Stock).

                  If the Selling Stockholder and the purchasing party cannot
         agree upon the Fair Market Value within twenty (20) days of delivery of
         the communication specified in this Section 4 (the "Communication"),
         the Selling Stockholder and the purchasing party may refer the matter
         to appraisal in accordance with the following:

                           (i) The parties shall endeavor in good faith to
                  agree, within ten (10) days of the last day of the twenty (20)
                  day period, upon a sole appraiser to conduct the appraisal.
                  Such appraiser shall conduct an appraisal of the Fair Market
                  Value of the Common Stock within thirty (30) days of his/her
                  selection, which appraisal shall be binding on the parties.

                           (ii) If the parties cannot agree upon a sole
                  appraiser within ten (10) days of the last day of the twenty
                  (20) day period referred to above, the Selling Stockholder,
                  and the purchasing parties, acting as a group, will select an
                  appraiser and the two appraisers will select a third
                  appraiser. The three appraisers shall be known as the
                  "Appraisal Panel". If either the Selling Stockholder and the
                  purchasing party fail to elect an appraiser within the
                  aforementioned ten (10) day period, the appraiser selected by
                  the other party shall perform the appraisal within thirty (30)
                  days and said appraisal shall be binding upon all of the
                  parties.

                           (iii) Each appraiser will be qualified by education,
                  experience or training to render a decision in the matters
                  submitted.

                                      -6-
<PAGE>   7

                           (iv) If an Appraisal Panel is selected, within thirty
                  (30) days of the selection of the third appraiser, each of the
                  Selling Stockholder's appraiser and the purchasing party's
                  appraiser shall have conducted such investigation as they deem
                  necessary regarding the valuation of the Company, and will
                  submit the Fair Market Value which it believes is accurate
                  (the "Submitted Valuation"), to the third appraiser.

                           (v) Within sixty (60) days after the third appraiser
                  has received the Submitted Valuations (or immediately if the
                  Submitted Valuations are within 10% of the Submitted Valuation
                  which is greater), such appraiser will render a decision
                  determining the Fair Market Value, as follows: if the
                  Submitted Valuations are within ten percent (10%) of the
                  Submitted Valuation which is the greater of the two, then the
                  Fair Market Value shall be the average of the Submitted
                  Valuations. If the Submitted Valuations diverge by more than
                  ten percent (10%) of the Submitted Valuation which is the
                  greater of the two, then the third appraiser shall determine
                  the Fair Market Value by selecting one of the Submitted
                  Valuations. The appraiser's decision shall be binding on the
                  parties.

                           All such valuations shall be determined in accordance
                  with generally accepted accounting principles and any dispute
                  as to the meaning of the phrase "generally accepted accounting
                  principles" or its application in any circumstances or to any
                  state of facts shall be referred to and conclusively
                  determined by the Company's auditors. The Company shall pay
                  for any appraisal conducted hereunder.

         5.       Right of Participation in Sales By the Stockholders.

                  (a) If at any time a Stockholder desires to sell all or any
         part of the Shares owned by him, her or it to any person or entity,
         (the "Proposed Transferee"), any Investor or the Founder shall have the
         right to sell to the Proposed Transferee, as a condition to such sale
         by such Stockholder (the "Selling Stockholder"), at the same price per
         share and on the same terms and conditions as the sale by the Selling
         Stockholder, the number of Shares to be acquired by the Proposed
         Transferee, times a fraction, the numerator of which is the number of
         shares of Common Stock into which such Investor's Preferred Stock is
         convertible (or, in the case of the Founder, the number of shares of
         Common Stock held by him at the time), and the denominator of which is
         the number of shares of Common Stock (assuming the conversion of all
         Preferred Stock into Common Stock) held by the Selling Stockholder and
         such of the Founder and the Investors as elect to participate in the
         sale to the Proposed Transferee.

                  (b) If an Investor or the Founder wishes to so participate in
         any sale under this Section 5, it shall notify the Selling Stockholder
         and the Company in writing of such intention as soon as practicable
         after receipt of the Offer made pursuant to Section 4, and in any event
         within fifteen (15) days after the date the Offer is given to the
         Company. Such notification shall be delivered to the Selling
         Stockholder in accordance with and at the address set forth in Section
         13 below.

                                      -7-
<PAGE>   8

                  (c) Subject to the right of first refusal in Section 4, the
         Selling Stockholder and, if any of them so elect, such Investors and
         the Founder, shall sell to the Proposed Transferee all, or at the
         option of the Proposed Transferee, any part, of the Shares proposed to
         be sold by them at not more than the price and upon other terms and
         conditions, if any, not more favorable to the Proposed Transferee than
         those in the Offer provided by the Selling Stockholder under Section 4
         above; provided, however, that any purchase of less than all of such
         Shares by the Proposed Transferee shall be made from the Selling
         Stockholder and the Investors and Founder pro rata based upon the
         relative number of Shares that the Selling Stockholder and the
         Investors and Founder are otherwise entitled to sell pursuant to
         Section 5(a).

                  (d) The Investors' and Founder's right to participate in sales
         pursuant to this Section 5 shall not apply with respect to sales,
         transfers or exchanges of Shares to the Company or in conjunction with
         a Sale of the Company.

         6.       Further Limitations Provisions Relating to Transfers by a
Stockholder.

                  (a) In addition to the other restrictions provided in this
         Agreement, the Founder agrees that the number of Shares which he or any
         of his Permitted Transferees (pursuant to Section 3 hereof) may
         transfer pursuant to Sections 4 and 5 shall not, for a period of five
         (5) years from December 11, 1996, exceed in the aggregate ten percent
         (10%) of the Shares he owns on the date hereof (subject to equitable
         adjustment for any stock split, stock dividend, combination of shares
         or the like and based upon Common Stock, or Common Stock equivalent)
         unless a greater number of shares is consented to by the Board of
         Directors of the Company; provided, however, that this limitation shall
         not apply to any sale, transfer or exchange of Shares to the Company or
         in conjunction with a Sale of the Company.

                  (b) Each Stockholder agrees that at the request of the
         Company, if required by the managing underwriter in conjunction with an
         initial public offering of securities of the Company, such Stockholder
         will agree not to offer to sell or to sell any equity securities of the
         Company owned by such Stockholder for a period of at least one hundred
         eighty (180) days after the closing of any such initial public
         offering, and for a period of at least ninety (90) days after the
         closing of any subsequent underwritten public offerings.

                  (c) Any Shares sold by a Selling Stockholder to a Proposed
         Transferee or a Purchaser pursuant to Sections 4 and 5 hereof shall no
         longer be subject to the restrictions imposed by Sections 3, 4 and 5 of
         this Agreement and any Shares sold by Investors pursuant to Section 5
         shall no longer be entitled to the benefits conferred by this
         Agreement; however, the Company shall require, as a condition to
         transfer of any such Shares, that the Proposed Transferee or Purchaser
         agree to be bound by the provisions of Sections 11 and 14 hereof.

         7.       Option to Repurchase Certain Shares of the Founder Upon
Termination of Employment.

                                      -8-
<PAGE>   9

                  (a) If the Founder shall cease to be retained as an executive
         officer of the Company as a result of his death, his disability or
         termination for "Cause" (as such term is defined in Section 7(h)), the
         Company may within seventy-five (75) days from the date upon which the
         Founder shall so cease to be employed (the "Termination Date"),
         exercise its option under this Section 7 to purchase from the Founder
         all or part of his Unvested Shares, as of the Termination Date. as
         provided in Section 7(b) hereof.

                  (b) The Shares subject to purchase under this Section 7, i.e.,
         Unvested Shares, shall initially be 2,250,000 shares of Common Stock
         (such number of Shares being subject to equitable adjustment for any
         stock split, stock dividend, combination of shares or the like and
         based upon Common Stock or Common Stock equivalents after December 11,
         1996), such Shares shall be released from the right of purchase set
         forth herein and thereupon become Vested Shares, in increments as
         follows: (i) on December 11, 1997 25% of such Unvested Shares, and (ii)
         quarterly thereafter an additional 6.25% of such Unvested Shares. In
         addition, in the event of a Change of Control Transaction (as defined
         in Section 7(i)), any then remaining Unvested Shares shall become
         Vested Shares ratably at the end of each quarter over the first year
         following the closing of such Transaction or over the original vesting
         schedule, if faster. Furthermore, if the Company reduces the Founder's
         compensation in a discriminatory fashion from other executives of the
         Company and he terminates his employment as a result, the Unvested
         Shares shall, upon such termination, cease to be subject to repurchase
         by the Company and shall become Vested Shares.

                  (c) Pursuant to the Existing Stockholders Agreement, the
         Founder delivered to and deposited with Posternak, Blankstein & Lund,
         L.L.P., as escrow agent (the "Escrow Agent"), pursuant to the Escrow
         Instructions attached hereto as Exhibit B ("Escrow Instructions"), the
         stock certificate(s) evidencing all of the Founder's Unvested Shares,
         together with undated assignments therefor duly endorsed for transfer
         in blank; and such Escrow Instructions shall remain in effect, except
         that hereafter all references therein to the Existing Stockholders
         Agreement shall mean and refer to this Agreement.

                  (d) The purchase price of any Unvested Shares for which the
         Company exercises its option under this Section 7 (the "Option Price")
         shall be $.001 per Share (such price being subject to equitable
         adjustment for any stock split, stock dividend, combination of shares
         or the like affecting the Common Stock after December 11, 1996).

                  (e) All Shares owned by the Founder which are not originally
         Unvested Shares or which are released from the right of purchase
         pursuant to Section 7(b) hereof are Vested Shares.

                  (f) If the Company desires to exercise its option to purchase,
         it shall do so by communicating in writing its election to purchase to
         the Founder, which communication shall state the basis for the
         Company's right to purchase the Unvested Shares, the number of Unvested
         Shares the Company is electing to purchase and the aggregate Option
         Price and shall be delivered in person or mailed to the Founder at his
         address set forth in accordance with Section 14 below within the
         seventy-five (75) day period provided for in

                                      -9-
<PAGE>   10

         Section 7(a). A copy of such notice accompanied by a request to release
         such Shares from escrow shall be sent to the Escrow Agent. The sale of
         the Shares to be sold to the Company pursuant to this Section 7 shall
         be made at the principal executive office of the Company on the 15th
         day following the date of the Company's written election to purchase
         (or if such 15th day is not a business day, then on the next succeeding
         business day). Such sale shall be effected by release from escrow and
         delivery to the Company of (i) a certificate or certificates evidencing
         the Shares to be purchased by it, and (ii) stock assignments therefor
         endorsed by the Founder for transfer to the Company, against payment by
         the Company to the Founder of the aggregate Option Price for such
         Shares to be purchased by the Company.

                  (g) Any Vested Shares held in escrow shall be released to the
         Founder upon written request by the Founder in compliance with the
         provisions of the Escrow Instructions.

                  (h) For purposes of this Agreement, the term "Cause" shall
         mean that any one or more of the following events has occurred: (i) the
         Founder's engaging in willful or intentional misconduct, or gross
         negligence by the Founder, which has caused demonstrable and serious
         injury to the Company, financial or otherwise, or to the Company's
         reputation; (ii) conviction of a felony, as evidenced by a judgment,
         order, or decree of a court of competent jurisdiction which shall
         adversely affect the Founder's ability to perform the material duties
         of his employment or the Company's reputation; (iii) insubordination or
         willful and continued failure by the Founder to comply with the
         material directions of the Board of Directors or the continued willful
         neglect or refusal by the Founder to perform the Founder's duties or
         responsibilities as an executive officer (unless such duties or
         responsibilities are significantly and adversely changed without the
         Founder's consent), after written notice that such actions are
         occurring has been furnished by the Company to the Founder and the
         Founder has been afforded a reasonable opportunity of at least
         forty-five (45) days to cure same; (iv) documented failure to meet
         performance expectations; or (v) continued and untreated alcohol and
         drug abuse, after written notice and a reasonable opportunity to cure,
         which materially adversely affects the Founder's performance of the
         duties of his employment. For purposes hereof, a "documented failure to
         meet performance expectations" shall mean the failure of the Founder to
         meet reasonable performance expectations established by the Company's
         Board of Directors, continuing over a period of at least ninety (90)
         days (or such longer period, specified by the Board of Directors or any
         designees thereof) and after at least two meetings of the Board of
         Directors or any designees thereof.

                  (i) In the event of a sale, merger, consolidation or other
         transaction (a "Change of Control Transaction") involving the Company
         (i) as a result of which more than fifty (50%) percent of the capital
         stock of the Company (or its successor) outstanding immediately after
         the effective date of such Change of Control Transaction is owned of
         record or beneficially by persons other than the holders of such
         Capital Stock immediately prior to such Change of Control Transaction,
         and (ii) following which the Founder is not offered continued
         employment with, or retained by the Company or its successor in a
         position with similar responsibilities and compensation to the
         Founder's

                                      -10-
<PAGE>   11

         position and compensation with the Company immediately prior to the
         Change of Control Transaction at a location within thirty-five (35)
         miles of the Founder's principal residence in the Greater Boston Area
         prior to the Change of Control Transaction, all remaining Unvested
         Shares shall cease to be subject to repurchase by the Company pursuant
         to Section 7(a) hereof, shall be released from escrow to the Founder
         and shall be Vested Shares effective as of the consummation of the
         Change of Control Transaction.

                  (j) For the period in effect on the date hereof and ending on
         December 11, 2000, or, if earlier, the effective date of the Founder's
         termination of employment with the Company, the Company will, provided
         the Founder is insurable at normal rates, obtain and thereafter
         maintain in full force and effect term life insurance in the amount of
         Two (2) Million Dollars on the life of the Founder, payable to a
         beneficiary designated by the Founder.

         8. Failure to Deliver Shares. If any Stockholder becomes obligated to
sell any Shares to the Company, any Investor and/or the Founder under this
Agreement and fails to deliver such Shares in accordance with the terms of this
Agreement, the Company, such Investor and/or the Founder, as the case may be,
may, at his, her or its option, in addition to all other remedies it may have,
deposit the purchase price for such Shares with a commercial bank approved by
the Board of Directors, as escrow transfer agent (the "Escrow Transfer Agent"),
and thereupon the Company shall cancel on its books the certificate or
certificates representing such Shares and shall issue, in lieu thereof and in
the name of such purchasing Investor, Founder or the Company, as the case may
be, a new certificate or certificates representing such Shares, and thereupon
all of such Stockholder's rights in and to such Shares shall terminate.
Thereafter, upon delivery to the Company by such Stockholder of the certificate
or certificates evidencing such Shares (duly endorsed for transfer, with
signature guaranteed, and free and clear of any liens or encumbrances), the
Company shall instruct the Escrow Transfer Agent to deliver the purchase price
to such Stockholder (any interest earned from the date of deposit of such funds
with the Escrow Transfer Agent to the date of delivery of such stock
certificates and payment of the purchase price to such Stockholders, shall
accrue to such Stockholder).

         9. Specific Enforcement. Each Stockholder expressly agrees that the
Founder, the Investors and the Company will be irreparably damaged if this
Agreement is not specifically enforced. Upon a breach or threatened breach of
the terms, covenants or conditions of this Agreement by a Stockholder, the
Company and the other interested parties shall, in addition to all other
remedies, each be entitled to a temporary or permanent injunction, without
showing any actual damage, and a decree for specific performance, in accordance
with the provisions hereof.

         10. Legend. Each certificate evidencing any of the Shares shall bear a
legend substantially as follows:

                  "The shares represented by this certificate are subject to
                  restrictions on transfer and may not be sold, exchanged,
                  transferred, pledged, hypothecated or otherwise disposed of,
                  whether voluntarily or by operation of law, except in
                  accordance with and subject to all the terms and conditions of
                  a certain Sixth Amended and Restated

                                      -11-
<PAGE>   12

                  Stockholders Agreement dated as of ___________, 2000, as
                  amended or amended and restated from time to time, a copy of
                  which the Company will furnish to the holder of this
                  certificate upon request and without charge."

         11.      Board of Directors.

                  (a) For so long as this Agreement remains in effect, each
         Stockholder and each Investor will vote any and all shares of the
         Company's Common Stock and Preferred Stock held by him, her or it from
         time to time, and will use his, her or its best efforts to cause the
         several members of the Company's Board of Directors (the "Board of
         Directors") to vote, so as to elect members of the Board of Directors,
         to maintain the membership of the Board of Directors, and to cause the
         Company to act or abstain from acting, in accordance with all of the
         provisions of this Agreement.

                  (b) The Board of Directors will be composed of not more than
         seven (7) members, as follows:

                           (i) Four (4) members representing the holders of the
                  Preferred Stock, one (1) of whom will be designated by Charles
                  River Partnership VII, L.P. (so long as it holds any Preferred
                  Stock) and who initially will be Michael Zak, one (1) of whom
                  will be designated by OneLiberty Fund III, L.P. (so long as it
                  holds any Preferred Stock) and who initially will be Edwin
                  Kania, one (1) of whom will be designated by New Enterprise
                  Associates VII, Limited Partnership (so long as it holds any
                  Preferred Stock) and who initially will be Arthur Marks and
                  one (1) of whom will be designated by FW Ventures IV L.P. (so
                  long as it or its affiliates hold any Preferred Stock) and who
                  initially will be David Brown.

                           (ii) One (1) member who will be selected by the
                  holders of a majority of the Common Stock (excluding for
                  purposes of this subsection (ii) the Preferred Stock and any
                  Common Stock issued upon conversion of the Preferred Stock);

                           (iii) One (1) member will be nominated by the Chief
                  Executive Officer of the Company, and approved by the
                  Directors representing the holders of a majority of the
                  Preferred Stock, which approval shall not be unreasonably
                  withheld; provided, however, that at the election of the
                  Directors representing the holders of the Preferred Stock,
                  such member will be a person unaffiliated with the Company or
                  any of its Stockholders, with relevant business experience;
                  and

                           (iv) One (1) member, who will be the Chief Executive
                  Officer of the Company and who is presently Malik Z. Khan.

                  (c) Directors will be entitled to reimbursement by the Company
         for reasonable out-of-pocket expenses incurred in connection with the
         performance of their duties as Directors, provided, however, that no
         directors' fee will be paid to any Director.

                                      -12-
<PAGE>   13

                  (d) The Board of Directors shall appoint and keep in effect
         (x) a Compensation Committee comprising the Chief Executive Officer of
         the Company and those directors designated in accordance with the
         provisions of Section 11(b)(i) and (y) an Audit Committee comprising at
         least the two (2) of the directors designated in accordance with the
         provisions of Section 11(b)(i) hereof.

                  (e) Notwithstanding anything to the contrary set forth in this
         Section 11, in the event the Company shall fail to redeem any shares of
         Preferred Stock, as and when provided in the Restated Certificate of
         Incorporation of the Company, thereafter, until such shares are
         redeemed, the holders of the Preferred Stock may designate a majority
         of the directors of the Company and the remaining directors will be (i)
         the Chief Executive Officer of the Company and (ii) two disinterested
         directors designated in accordance with Section 11(b)(iii).

                  (f) If any director shall fail or cease to serve for any
         reason, then the vacancy created by such director shall be filled only
         in accordance with Section 11(b) hereof.

         12. Pre-emptive Rights. The Company shall, prior to any issuance by the
Company of any of its securities (other than debt securities with no equity
feature and shares issued pursuant to the Series G Purchase Agreement of even
date hereof), offer to each holder of Preferred Stock and to the Founder (so
long as he owns any Shares) by written notice the right, for a period of fifteen
(15) days, to purchase its or his pro-rata share (determined on a fully diluted
and as converted basis, based on the number of shares of Stock into which the
shares of Preferred Stock held by any holder could be converted on the date of
such notices, and assuming the conversion of all Preferred Stock into Common
Stock and the exercise of all options and warrants as of the date of any such
notice) of such securities proposed to be issued (the "Offered Securities") for
cash at an amount equal to the price or other consideration for which such
Offered Securities are to be issued; provided, however, that the pre-emptive
rights pursuant to this Section 12 shall not apply to securities issued, (A)
upon conversion of any of the Preferred Stock into Common Stock, (B) as a stock
dividend or upon any subdivision of shares of Common Stock, provided that the
securities issued pursuant to such stock dividend or subdivision are limited to
additional shares of Common Stock, (C) in connection with any merger or
consolidation of the Company with another corporation or other entity or as
consideration for the acquisition (whether by the Company or any of its
subsidiaries of the stock or assets of any other entity), (D) pursuant to a
Qualified Public Offering, (E) pursuant to the issuance of shares of Common
Stock or the exercise of options, warrants or similar securities to purchase
Common Stock, presently outstanding or hereafter issued or granted pursuant to
the Company's 1996 Incentive Stock Plan, as amended from time to time or
pursuant to any similar plan approved by the Board of Directors for the purpose
of using equity securities to provide incentives to persons or entities whom the
Board of Directors determines can help the Corporation achieve its objective,
not to exceed in the aggregate 7,200,000 shares and the issuance of, or grant of
options or warrants to purchase up to 300,000 shares of Common Stock pursuant to
routine equipment financing transactions (each as appropriately adjusted to
reflect stock splits, stock dividends, combinations of shares and the like with
respect to the Common Stock), in each case, plus such additional number of
shares as may from time to time be approved by the holders of at least sixty
(60%) percent of the Preferred Stock voting or acting as

                                      -13-
<PAGE>   14

a single class, and (F) upon the exercise of any right which was not itself in
violation of the terms of this Section 12. Unless the Board of Directors of the
Company shall determine otherwise, the maximum number of shares under the
Company's 1996 Incentive Stock Option Plan excluded from the pre-emptive rights
pursuant to the preceding sentence of this Section 12 shall be automatically
increased on January 1, 2001 and on the first calendar day of each year
thereafter by a number equal to the lesser of (i) 3,000,000 shares of Common
Stock (as appropriately adjusted to reflect stock splits, stock dividends,
combinations of shares and the like with respect to the Common Stock) and (ii)
the number of shares of Common Stock equal to five percent (5%) of the issued
and outstanding shares of Common Stock of the Company (calculated on a
fully-diluted (including all shares issuable under the Corporation's 1996
Incentive Stock Plan) and as-converted basis); provided, that the maximum number
of shares of Common Stock under the Corporation's 1996 Incentive Stock Plan
excluded from adjustments pursuant to the preceding sentence of this Section 12
shall not exceed a number of shares of Common Stock equal to twenty-five percent
(25%) of the issued and outstanding shares of Common Stock (calculated on a
fully-diluted (including all shares issuable under the Corporation's 1996
Incentive Stock Plan) and as-converted basis). The Company's written notice to
the Investors and the Founder shall describe the securities proposed to be
issued by the Company and specify the number, price and payment terms. The
Founder and each Investor may accept the Company's offer as to the full number
of securities offered to it or any lesser number, by written notice thereof
given by it to the Company prior to the expiration of the aforesaid fifteen (15)
day period, in which event the Company shall promptly sell and such holder shall
buy, upon the terms specified, the number of securities agreed to be purchased
by such Purchaser. The Company shall be free at such time prior to ninety (90)
days after the date of its notice of offer to the Investors and the Founder, to
offer and sell, to any third party or parties such Offered Securities as are not
purchased by the Investors and the Founder, at a price and on payment and terms
no less favorable to the Company than those specified in such notice of offer to
such holders. However, if such sale or sales are not consummated within such
ninety (90) day period, the Company shall not sell such Offered Securities as
shall have not been purchased within such period without again complying with
this Section 12. The right to purchase granted pursuant to this Section 12 shall
expire immediately prior to the first sale of Common Stock pursuant to a
Qualified Public Offering. The provisions of this Section 12 may be waived (but
only as to the Investors and the Founder as a group), amended, modified or
terminated by written consents of the Investors and/or the Founder, who in the
aggregate hold at least sixty (60%) percent (determined on a fully diluted
as-converted basis, based on the number of shares of Stock into which the shares
of Preferred Stock held by such holders would then be converted on the date of
such consents) of the Shares owned by all such stockholders (including in the
case of the Founder, his Permitted Transferees), provided, however that any such
amendment, modification or termination which treats any of the Investors or the
Founder in a discriminatory fashion shall require the written consent of such
Investor or Founder.

         13. Notices. Any notice required or permitted to be given hereunder
shall be in writing and shall be deemed to be properly given when sent by
registered or certified mail, return receipt requested, by Federal Express, DHL,
or other guaranteed overnight delivery service or by facsimile transmission,
addressed as follows:

             If to the Company:                        Sitara Networks, Inc.

                                      -14-
<PAGE>   15

<TABLE>
<S>                                                    <C>
                                                       60 Hickory Drive
                                                       Waltham, MA  02154
                                                       Attention:  President
                                                       Telecopier:  (781) 890-8042

             With a copy to:                           McDermott, Will & Emery
                                                       28 State Street
                                                       Boston, MA  02109
                                                       Attention:  Arthur I. Anderson, P.C.
                                                       Telecopier:  (617) 535-3800

             If to the Founder:                        Malik Z. Khan
                                                       240 Western Avenue
                                                       Sherborn, MA  01770
                                                       Telecopier:

             If to any Investor:                       To the address of such Investor set forth on the
                                                       applicable signature page hereto
</TABLE>

and if to any other Holder at such Holder's address for notice as set forth in
the register maintained by the Company, or, as to any of the foregoing, to such
other address as any such party may give the others notice of pursuant to this
section, provided that a change of address shall only be effective upon receipt.

         All notices, requests, consents and other communications hereunder
shall be deemed to have been received (i) if by hand, at the time of the
delivery thereof to the receiving party at the address of such party set forth
above or as so designated, (ii) if made by telecopy or facsimile transmission,
at the time that receipt thereof has been acknowledged by electronic
confirmation or otherwise, (iii) if sent by overnight courier, on the day such
notice is delivered by the courier service, or (iv) if sent by registered or
certified mail, on the fifth (5th) business day following the day such mailing
is made.

         14. Waiver and Amendment. The provisions of the Agreement may not
waived, amended, modified or terminated except (i) with the written consent of
the holders of at least sixty (60%) percent of the outstanding Preferred Stock,
and (ii) if such waiver, amendment, modification or termination affects the
Founder's rights under this Agreement, other than a waiver, modification,
amendment or termination of Section 12, in accordance with the terms thereof,
with the written consent of the Founder as well. This Agreement shall terminate
(a) immediately prior to the consummation of a Qualified Public Offering or (b)
on the tenth anniversary of the date of this Agreement, whichever first occurs.
Notwithstanding any such termination, Section 6(b) hereof shall remain in full
force and effect until and unless such provision is specifically terminated in
accordance with the provisions of this Section 14.

                                      -15-
<PAGE>   16

         15. Entire Agreement and Amendments. This Agreement constitutes the
entire agreement of the parties with respect to the subject matter hereof. To
the extent any term or other provision of any other agreement or instrument by
which any party hereto is bound conflicts with this Agreement, this Agreement
shall have precedence over such conflicting term or provision.

         16. Governing Law; Successors and Assigns. This Agreement shall be
governed by the laws of the Commonwealth of Massachusetts (without regard to
choice of law provisions) and shall be binding upon and shall inure to the
benefit of the heirs, personal representatives, executors, administrators,
successors and permitted assigns of the parties hereto. If an Investor sells or
transfers some or all of such Investor's Stock, then any transferee of such
Investor will be entitled to all rights under this Agreement to which such
transferring Investor would been entitled if such Investor had not transferred
such Stock, except where the rights such a transferee are limited or otherwise
restricted as set forth in this Agreement.

         17. Waivers. No waiver of any breach or default hereunder shall be
considered valid unless in writing, and no such waiver shall be deemed a waiver
of any subsequent breach or default of the same or similar nature.

         18. Severability. If any provision of this Agreement shall be held to
be illegal, invalid or unenforceable, such illegality, invalidity or
unenforceability shall attach only to such provision and shall not in any manner
affect or render illegal, invalid or unenforceable any other provision of this
Agreement, and this Agreement shall be carried out as if any such illegal,
invalid or unenforceable provision were not contained herein.

         19. Captions. Captions are for convenience only and are not deemed to
be part of this Agreement.

         20. Continuation of Employment. Nothing in this Agreement shall create
an obligation on the Company or the Stockholders to continue any Stockholder's
employment with the Company.

         21. Counterparts. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

              [THE REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK]

                                      -16-
<PAGE>   17
         IN WITNESS WHEREOF, this Agreement has been executed as of the date and
year first above written.

ATTEST:                                   COMPANY:

                                          SITARA NETWORKS, INC.

 /s/ Arthur Anderson                      By:  /s/ Malik Z. Khan
 -------------------                           -----------------
   Secretary                                       Malik Z. Khan, President
                                                   60 Hickory Drive
                                                   Waltham, MA 02154

                                          FOUNDER:

                                          /s/ Malik Z. Khan
                                          -----------------
                                          Malik Z. Khan
                                          240 Western Avenue
                                          Sherborn, MA 01770

                                          INVESTORS:

                                          ONELIBERTY FUND III, L.P.

                                          By: One Liberty Partners III, L.P.,
                                          its general partner

                                          By:  /s/ Edwin M. Kania, Jr.
                                               -----------------------
                                               Edwin M. Kania, Jr.
                                               One Liberty Square
                                               Boston, MA 02109
<PAGE>   18
                                          FW VENTURES IV L.P.

                                          By:  /s/ David Brown
                                               ---------------
                                          Name:   David Brown
                                          Title:
                                          201 Main Street, Suite 3100
                                          Fort Worth, TX 76102

                                          ESSEX PRIVATE PLACEMENT FUND III-A,
                                          LIMITED PARTNERSHIP.

                                          By:  Essex Investment Management
                                          Company, LLC, its general partner

                                          By:  /s/ Susan P. Stickells
                                               ----------------------
                                          Name:    Susan P. Stickells
                                          Title: Principal
                                          125 High Street, 29th Floor
                                          Boston, MA 02110

                                          ESSEX PRIVATE PLACEMENT FUND III-B,
                                          LIMITED PARTNERSHIP.

                                          By:  Essex Investment Management
                                          Company, LLC, its general partner

                                          By:  /s/ Susan P. Stickells
                                               ----------------------
                                          Name:    Susan P. Stickells
                                          Title: Principal
                                          125 High Street, 29th Floor
                                          Boston, MA 02110

<PAGE>   19
                                          ESSEX HIGH TECHNOLOGY FUND L.P.

                                          By:  Essex Investment Management
                                          Company, LLC, its general partner

                                          By:  /s/ Susan P. Stickells
                                               ----------------------
                                          Name:    Susan P. Stickells
                                          Title: Principal
                                          125 High Street, 29th Floor
                                          Boston, MA 02110

                                          TWP SITARA INVESTORS

                                          By:  /s/ David A. Baylor
                                               -------------------
                                          Name:    David A. Baylor
                                          Title:  Managing Partner

                                          TAILWIND CAPITAL PARTNERS 2000, L.P.

                                          By:  Thomas Weisel Capital Partners
                                          LLC, General Partner

                                          By:  /s/ David Baylor
                                               ----------------
                                          Name:    David Baylor
                                          Title:  General Counsel

                                          /s/ Barry Davis
                                          ---------------
                                              Barry Davis

                                          NEW ENTERPRISE ASSOCIATES VII, LP

                                          By:  /s/ Arthur J. Marks
                                               -------------------
                                          Name:    Arthur J. Marks
<PAGE>   20
                                          NEA PRESIDENTS' FUND, L.P.

                                          By:  /s/ Arthur J. Marks
                                               -------------------
                                          Name:    Arthur J. Marks

                                          PRISM VENTURE PARTNERS I, L.P.

                                          By:  Prism Investment Partners,
                                          L.L.C., its general partner

                                          By:  /s/ Robert Fleming
                                               ------------------
                                          Name:    Robert Fleming
                                          100 Lowder Brook Drive
                                          Suite 2500
                                          Westwood, MA 02090

                                          MFS SERIES TRUST I on behalf of
                                          MFS New Discovery Fund ("NDF")
                                          ($4,841,584.65; 743,715 shares)
                                          Nominee: Clump & Co.
                                          Nominee ID: 04-3208074
                                          Tax ID: 04-3339400

                                          By:  /s/ Ellen Moynihan
                                               ------------------
                                          Name:    Ellen Moynihan
                                          Title: Assistant Treasurer

                                          MFS/SUN LIFE SERIES TRUST on behalf
                                          of MFS New Discovery Series ("NWD")
                                         ($482,391; 74,100 shares)
                                          Nominee: Inletbluff & Co.
                                          Nominee ID: 04-3409455
                                          Tax ID: 04-3417488

                                          By:  /s/ Ellen Moynihan
                                               ------------------
                                          Name:    Ellen Moynihan
                                          Title: Assistant Treasurer
<PAGE>   21
                                          MFS VARIABLE INSURANCE TRUST on behalf
                                          of MFS New Discovery Series ("VND")
                                          ($276,024; 42,400 shares)
                                          Nominee: Newwind & Co.
                                          Nominee ID: 04-3409369
                                          Tax ID: 04-3417481

                                          By:  /s/ Ellen Moynihan
                                               ------------------
                                          Name:    Ellen Moynihan
                                          Title: Assistant Treasurer

                                          MFS SERIES TRUST I on behalf of
                                          MFS Technology Fund ("SCT")
                                          ($400,000.44; 61,444 shares)
                                          Nominee: Distinguish & Co.
                                          Nominee ID: 04-3208197
                                          Tax ID: 04-3339406

                                          By:  /s/ Ellen Moynihan
                                               ------------------
                                          Name:    Ellen Moynihan
                                          Title: Assistant Treasurer

     A copy of the Declaration of Trust of each of the above (each, the "Trust")
is on file with the Secretary of State of The Commonwealth of Massachusetts. You
acknowledge that the obligations of or arising out of this instrument are not
binding upon any of the Trust's trustees, officers, employees, agents or
shareholders individually, but are binding solely upon the assets and property
of the Trust in accordance with its proportionate interest hereunder. If this
instrument is executed by the Trust on behalf of one or more series of the
Trust, you further acknowledge that the assets and liabilities of each series of
the Trust are separate and distinct and that the obligations of or arising out
of this instrument are binding solely upon the assets or property of the series
on whose behalf the Trust has executed this instrument. If the Trust has
executed this instrument on behalf of more than one series of the Trust, you
also agree that the obligations of each series hereunder shall be several and
not joint, in accordance with its proportionate interest hereunder, and you
agree not to proceed against any series for the obligations of another series.

                                          VAN WAGONER CAPITAL MANAGEMENT

                                          By:  /s/ Audrey Lam
                                               --------------
                                          Name:    Audrey Lam
                                          Title:  Managing Director
                                          345 California Street, Suite 2450
                                          San Francisco, CA 94104

                                          BT INVESTMENT PARTNERS, INC.

                                          By:  /s/ Kristine Cicardo
                                               --------------------
                                          Name:    Kristine Cicardo
                                          Title:  Director
<PAGE>   22
                                          CHARLES RIVER PARTNERSHIP VII, L.P.

                                          By:  /s/ Michael Zak
                                               ---------------
                                          Name:    Michael Zak
                                          Title: General Partner
                                          1000 Winter Street, Suite 3300
                                          Waltham, MA 02154

                                          SIEMENS SERVICES, INC.

                                          By:  /s/ Michael Rowan
                                               -----------------
                                          Name:    Michael Rowan
                                          Title: Vice President
                                          Chase Manhattan Center, Suite 1402
                                          1201 Market Street
                                          Wilmington, DE 19801

                                          SIEMENS SERVICES, INC.

                                          By:  /s/ Christine Krzyzarnski
                                               -------------------------
                                          Name:    Christine Krzyzarnski
                                          Title: Vice President
                                          Chase Manhattan Center, Suite 1402
                                          1201 Market Street
                                          Wilmington, DE  19801

                                          /s/ Dipak Rastogi
                                          -----------------
                                              Dipak Rastogi

                                          /s/ Audrey M. Rastogi
                                          ---------------------
                                              Audrey M. Rastogi

                                          /s/ John Halligan
                                          -----------------
                                              John Halligan

                                          /s/ Andy Fox
                                          ------------
                                              Andy Fox
<PAGE>   23
                                          /s/ Michael Bassinger
                                          ---------------------
                                              Michael Bassinger

                                          /s/ Rhys Williams
                                          -----------------
                                              Rhys Williams
                                              General Partner, SIVO G.P.

                                          /s/ Manny Fernandez
                                          -------------------
                                              Manny Fernandez

                                          SI VENTURE FUND II, L.P.

                                          By:  /s/ Manny Fernandez
                                               -------------------
                                          Name:    Manny Fernandez
                                          Title:  Managing Director

                                          ANGLO AMERICAN SECURITY FUND, L.P.

                                          By:  /s/ John S. Grace
                                               -----------------
                                          Name:    John S. Grace
                                          Title:  General Partner

                                          CABIN INTERIORS, LP
                                          By:  Cabin Interiors, Inc., its
                                          general partner

                                          By:  /s/ John S. Grace
                                               -----------------
                                          Name:    John S. Grace
                                          Title:  President

                                          DIVERSIFIED LONG TERM GROWTH FUND,
                                          L.P.
                                          By:  Associated Asset Management, Inc.
                                          its general partner

                                          By:  /s/ John S. Grace
                                               -----------------
                                          Name:    John S. Grace
                                          Title:  Co-Chairman
<PAGE>   24
                                          DRAKE ASSOCIATES, L.P.
                                          By:  Associated Asset Management, Inc.
                                          its general partner

                                          By:  /s/ John S. Grace
                                               -----------------
                                          Name:    John S. Grace
                                          Title:  Co-Chairman

                                          STERLING GRACE CAPITAL MANAGEMENT, LP.
                                          By:  Sterling Grace Corporation, its
                                          general partner

                                          By:  /s/ John S. Grace
                                               -----------------
                                          Name:    John S. Grace
                                          Title:  President

                                          GRACE-ARTEL INVESTORS, INC.

                                          By:  /s/  Oliver R. Grace
                                               --------------------
                                          Name:     Oliver R. Grace
                                          Title:   Chairman

                                          THE SOG FUND LP.
                                          By:  The Special Opportunities Group,
                                          LLC its managing general partner

                                          By:  /s/ Christopher G. Miller
                                               --------------------------
                                          Name:    Christopher G. Miller
                                          Title:  Chief Executive Officer

                                          THE SOG FUND II LP
                                          By:  The Special Opportunities Group,
                                          LLC its managing general partner

                                          By:  /s/ Christopher G. Miller
                                               --------------------------
                                          Name:    Christopher G. Miller
                                          Title:  Chief Executive Officer
<PAGE>   25
                                    EXHIBIT A

                            INSTRUMENTS OF ADHERENCE
                                 ("Stockholder")

         The undersigned, a holder of shares of Common Stock, $0.00001 par
value, of Sitara Networks, Inc., a Delaware corporation (the "Company"), hereby
joins in and agrees to be bound by all the terms and provisions of that Certain
Sixth Amended and Restated Stockholders Agreement dated as of
_______________________, shall for all purposes be deemed to be a Stockholder
thereunder, subject to all of the obligations of a Stockholder set forth
therein, and hereby agrees that all shares of Common Stock now or hereafter held
by the undersigned shall be subject to the restrictions on transfer, rights of
purchase and co-sale and other provisions of said Agreement.

         EXECUTED on this ___________ day of ________________ , ___________.

                                                  ______________________________
<PAGE>   26
                               AMENDMENT NO. 1 TO

                              SITARA NETWORKS, INC.
                      SERIES G CONVERTIBLE PREFERRED STOCK
                               PURCHASE AGREEMENT,

                           SIXTH AMENDED AND RESTATED
                             STOCKHOLDERS AGREEMENT

                                       AND

                           SIXTH AMENDED AND RESTATED
                          REGISTRATION RIGHTS AGREEMENT

                              SEPTEMBER ____, 2000

         WHEREAS, the undersigned, being (i) Sitara Networks, Inc., a Delaware
corporation (the "Company"), (ii) the holders (the "Required Holders") of at
least sixty (60%) percent of the issued and outstanding shares of Series A
Convertible Preferred Stock, $0.00001 par value per share, (the "Series A
Stock"), Series B Convertible Preferred Stock, $0.00001 par value per share (the
"Series B Stock"), Series C Convertible Preferred Stock, $0.00001 par value per
share (the "Series C Stock"), Series D Convertible Preferred Stock, $0.00001 par
value (the "Series D Stock"), Series E Convertible Preferred Stock, $0.00001 par
value per share (the "Series E Stock"), Series F Convertible Preferred Stock,
$0.00001 par value per share (the "Series F Stock"), and Series G Convertible
Preferred Stock, $0.00001 (the "Series G Stock" and together with the Series A
Stock, the Series B Stock, the Series C Stock, the Series D Stock, the Series E
Stock, and the Series F Stock the "Preferred Stock") of the Company, calculated
as a single class (treating all Preferred Stock for all purposes herein as if
converted to Common Stock, par value $.00001 per share ), and (iii) Malik Z.
Khan, in his capacity as the founder of the Company (the "Founder"), desire to
amend (1) that certain Series G Convertible Preferred Stock Purchase Agreement,
dated as of June 16, 2000, by and among the Company and the other parties
thereto (the "Series G Purchase Agreement"), (2) that certain Sixth Amended and
Restated Stockholders Agreement, dated as of June 16, 2000, by and among the
Company and the other parties thereto (the "Stockholders Agreement") and (3)
that certain Sixth Amended and Restated Registration Rights Agreement, dated as
of June 16, 2000 by and among the Company and the other parties thereto (the
"Registration Rights Agreement");

         WHEREAS, Section 6.02 of the Series G Purchase Agreement permits
amendments to such agreement upon the written consent of the Company and the
Required Holders;

         WHEREAS, Section 14 of the Stockholders Agreement permits amendments to
such agreement upon the written consent of the Company, the Required Holders and
the Founder; and

         WHEREAS, Section 13 of the Registration Rights Agreement permits
amendments to such agreement upon the written consent of the Company, the
Required Holders and the Founder;
<PAGE>   27
         NOW, THEREFORE, in consideration of the mutual covenants set forth
herein, the parties hereto agree as follows:

         A.       That, the Series G Purchase Agreement be amended to the extent
set forth below:

                  1. The second sentence of Section 2.03(b) of the Agreement is
         hereby amended and restated in its entirety to read as follows:

                  "Such purchase and sale shall take place at a closing or
                  series of closings (the "Subsequent Closings" and together
                  with the Initial Closing, the "Closing") to be held at the
                  office of Counsel to the Company, 28 State Street, Boston,
                  Massachusetts 02109, at any time or from time to time, through
                  and including October 15, 2000, as may be mutually agreed upon
                  by the Company and such Purchasers."

                  2. The Company is hereby empowered to amend and restate
         Exhibit 2.01A of the Series G Purchase Agreement to reflect any
         additional sales of Series G Stock in any Subsequent Closings.

         B.       That the Stockholders Agreement be amended (i) to the extent
necessary to add any persons who purchase any shares of Series G Stock at any
Subsequent Closing to the Stockholders Agreement as "Investors" thereunder and
(ii) to the extent set forth below:

                  1. The number of shares current issuable under the Company's
         Stock Incentive Program that are excluded from the pre-emptive rights
         set forth in Section 12 of the Stockholders Agreement shall be
         increased by replacing the number "7,200,000" in clause (E) of the
         first sentence of Section 12 of the Stockholders Agreement with the
         number "9,200,000".

         C.       That the Registration Rights Agreement be amended to the
extent necessary to add any persons who purchase any shares of Series G Stock at
any Subsequent Closing to the Registration Rights Agreement as "Investors"
thereunder and to accordingly amend and restate Schedule RRA-1 of the
Registration Rights Agreement.

                            [SIGNATURE PAGES FOLLOW]

                                       2
<PAGE>   28
         IN WITNESS WHEREOF, the undersigned have executed this Amendment No. 1
to the Sitara Networks, Inc. Series G Convertible Preferred Stock Purchase
Agreement, the Sixth Amended and Restated Stockholders Agreement and the Sixth
Amended and Restated Registration Rights Agreement as of the date first written
above.

                                          COMPANY:

                                          SITARA NETWORKS, INC.

                                          By:    /s/ Malik Khan
                                                 -----------------------------
                                          Name:  Malik Khan
                                          Title: President

                                          FOUNDER:

                                          /s/ Malik Khan
                                          Malik Z. Khan

                                          PREFERRED STOCKHOLDERS:

                                          CHARLES RIVER PARTNERSHIP VII, L.P.

                                          By:    /s/ Michael Zak
                                                 -----------------------------
                                                 Michael Zak, General Partner

                                          ONE LIBERTY FUND III, L.P.

                                          By:  OneLiberty Partners III, L.P.,
                                               its general partner

                                          By:    /s/ Edwin M. Kania, Jr.
                                                 -----------------------------
                                          Name:  Edwin M. Kania, Jr.
                                          Title:
<PAGE>   29
                                          NEW ENTERPRISE ASSOCIATES VII, LP

                                          By:    /s/ Arthur Marks
                                                 -----------------------------
                                          Name:  Arthur Marks
                                          Title: General Partner

                                          NEA PRESIDENTS' FUND, L.P.

                                          By:    /s/ Arthur Marks
                                                 -----------------------------
                                          Name:  Arthur Marks
                                          Title: General Partner

                                          FW VENTURES IV, L.P.

                                                 By:    /s/ David G. Brown
                                                        ------------------------
                                                 Name:  David G. Brown
                                                 Title: Vice President

                                          PRISM VENTURE PARTNERS I, L.P.

                                          By:    Prism Investment Partners,
                                                 L.P., its general partner

                                                 By:   Prism Venture Partners,
                                                       L.L.C., its general
                                                       partner

                                                 By:   /s/ Robert Fleming
                                                       -------------------------
                                                       Managing Director

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00018-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00018-of-00352.parquet"}], [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00018-of-00352.parquet"}]]