Exhibit 1.1


                                4,000,000 SHARES

                             NETSCOUT SYSTEMS, INC.

                                  COMMON STOCK

                             UNDERWRITING AGREEMENT


                                                                        __, 1999


DEUTSCHE BANC ALEX. BROWN
BEAR, STEARNS & CO. INC.
DAIN RAUSCHER WESSELS
  As Representatives of the Several Underwriters,
    c/o Deutsche Banc Alex. Brown
         101 Federal Street, 15th Floor
         Boston, Massachusetts  02110

Dear Sirs:

         1. INTRODUCTORY. NetScout Systems, Inc., a Delaware corporation
("COMPANY"), proposes to issue and sell 4,000,000 shares of its common stock,
$.001 par value per share ("SECURITIES") (such shares of Securities being
hereinafter referred to as the "FIRM SECURITIES"). The stockholders listed in
Schedule A hereto (the "Selling Stockholders") also propose to sell to the
Underwriters, at the option of the Underwriters, an aggregate of not more than
600,000 additional outstanding shares of the Company's Securities, as set forth
below (such 600,000 additional shares being hereinafter referred to as the
"OPTIONAL SECURITIES"). The Firm Securities and the Optional Securities are
herein collectively called the "OFFERED SECURITIES". The Company and the Selling
Stockholders hereby agree with the several Underwriters named in Schedule B
hereto ("UNDERWRITERS") as follows:

         2. REPRESENTATIONS AND WARRANTIES OF THE COMPANY AND THE SELLING
STOCKHOLDERS. (a) The Company and Narendra Popat (the "Principal Selling
Stockholder"), jointly and severally, represent and warrant to, and agree with,
the several Underwriters that:

              (i) A registration statement (No. 333-76843) relating to the
         Offered Securities, including a form of prospectus, has been filed with
         the Securities and Exchange Commission ("COMMISSION") and either (A)
         has been declared effective under the Securities Act of 1933 ("ACT")
         and is not proposed to be amended or (B) is proposed to be amended by
         amendment or post-effective amendment. If such registration statement
         (the "INITIAL REGISTRATION STATEMENT") has been declared effective,
         either (A) an additional registration statement (the "ADDITIONAL
         REGISTRATION STATEMENT")




         relating to the Offered Securities may have been filed with the
         Commission pursuant to Rule 462(b) ("RULE 462(b)") under
         the Act and, if so filed, has become effective upon filing pursuant to
         such Rule and the Offered Securities all have been duly registered
         under the Act pursuant to the initial registration statement and, if
         applicable, the additional registration statement or (B) such an
         additional registration statement is proposed to be filed with the
         Commission pursuant to Rule 462(b) and will become effective upon
         filing pursuant to such Rule and upon such filing the Offered
         Securities will all have been duly registered under the Act pursuant to
         the initial registration statement and such additional registration
         statement. If the Company does not propose to amend the initial
         registration statement or if an additional registration statement has
         been filed and the Company does not propose to amend it, and if any
         post-effective amendment to either such registration statement has been
         filed with the Commission prior to the execution and delivery of this
         Agreement, the most recent amendment (if any) to each such registration
         statement has been declared effective by the Commission or has become
         effective upon filing pursuant to Rule 462(c) ("RULE 462(c)") under the
         Act or, in the case of the additional registration statement, Rule
         462(b). For purposes of this Agreement, "EFFECTIVE TIME" with respect
         to the initial registration statement or, if filed prior to the
         execution and delivery of this Agreement, the additional registration
         statement means (A) if the Company has advised the Representatives that
         it does not propose to amend such registration statement, the date and
         time as of which such registration statement, or the most recent
         post-effective amendment thereto (if any) filed prior to the execution
         and delivery of this Agreement, was declared effective by the
         Commission or has become effective upon filing pursuant to Rule 462(c),
         or (B) if the Company has advised the Representatives that it proposes
         to file an amendment or post-effective amendment to such registration
         statement, the date and time as of which such registration statement,
         as amended by such amendment or post-effective amendment, as the case
         may be, is declared effective by the Commission. If an additional
         registration statement has not been filed prior to the execution and
         delivery of this Agreement but the Company has advised the
         Representatives that it proposes to file one, "EFFECTIVE TIME" with
         respect to such additional registration statement means the date and
         time as of which such registration statement is filed and becomes
         effective pursuant to Rule 462(b). "EFFECTIVE DATE" with respect to the
         initial registration statement or the additional registration statement
         (if any) means the date of the Effective Time thereof. The initial
         registration statement, as amended at its Effective Time, including all
         information contained in the additional registration statement (if any)
         and deemed to be a part of the initial registration statement as of the
         Effective Time of the additional registration statement pursuant to the
         General Instructions of the Form on which it is filed and including all
         information (if any) deemed to be a part of the initial registration
         statement as of its Effective Time pursuant to Rule 430A(b) ("RULE
         430A(b)") under the Act, is hereinafter referred to as the "INITIAL
         REGISTRATION STATEMENT". The additional registration statement, as
         amended at its Effective Time, including the contents of the initial
         registration statement incorporated by reference therein and including
         all information (if any) deemed to be a part of the additional
         registration statement as of its Effective Time pursuant to Rule
         430A(b), is hereinafter referred to as the "ADDITIONAL REGISTRATION
         STATEMENT". The Initial Registration Statement and the Additional
         Registration Statement are hereinafter referred to collectively as the
         "REGISTRATION STATEMENTS" and individually as a "REGISTRATION
         STATEMENT". The form of prospectus relating to the Offered Securities,
         as first filed with the Commission pursuant to and in accordance with
         Rule 424(b) ("RULE 424(b)") under the Act or (if no such filing is
         required) as included in a Registration Statement, is hereinafter
         referred to as the "PROSPECTUS". No document has been or will be
         prepared or distributed in reliance on Rule 434 under the Act.

              (ii) If the Effective Time of the Initial Registration Statement
         is prior to the execution and delivery of this Agreement: (A) on the
         Effective Date of the Initial Registration Statement, the Initial
         Registration Statement conformed in all material respects to the
         requirements of the Act and the rules and regulations of the Commission
         ("RULES AND REGULATIONS") and did not include any


                                      -2-



         untrue statement of a material fact or omit to state any material fact
         required to be stated therein or necessary to make the statements
         therein, in light of the circumstances under which they were made, not
         misleading, (B) on the Effective Date of the Additional Registration
         Statement (if any), each Registration Statement conformed or will
         conform, in all respects to the requirements of the Act and the Rules
         and Regulations and did not include, or will not include, any untrue
         statement of a material fact and did not omit, or will not omit, to
         state any material fact required to be stated therein or necessary to
         make the statements therein, in light of the circumstances under which
         they were made, not misleading, and (C) on the date of this Agreement,
         the Initial Registration Statement and, if the Effective Time of the
         Additional Registration Statement is prior to the execution and
         delivery of this Agreement, the Additional Registration Statement each
         conforms, and at the time of filing of the Prospectus pursuant to Rule
         424(b) or (if no such filing is required) at the Effective Date of the
         Additional Registration Statement in which the Prospectus is included,
         each Registration Statement and the Prospectus will conform, in all
         material respects to the requirements of the Act and the Rules and
         Regulations, and neither of such documents includes, or will include,
         any untrue statement of a material fact or omits, or will omit, to
         state any material fact required to be stated therein or necessary to
         make the statements therein, in light of the circumstances under which
         they were made, not misleading. If the Effective Time of the Initial
         Registration Statement is subsequent to the execution and delivery of
         this Agreement: on the Effective Date of the Initial Registration
         Statement, the Initial Registration Statement and the Prospectus will
         conform in all material respects to the requirements of the Act and the
         Rules and Regulations, neither of such documents will include any
         untrue statement of a material fact or will omit to state any material
         fact required to be stated therein or necessary to make the statements
         therein not misleading, and no Additional Registration Statement has
         been or will be filed. The two preceding sentences do not apply to
         statements in or omissions from a Registration Statement or the
         Prospectus based upon written information furnished to the Company by
         any Underwriter through the Representatives specifically for use
         therein, it being understood and agreed that the only such information
         is that described as such in Section 7(c) hereof.

              (iii) The Company has been duly incorporated and is an existing
         corporation in good standing under the laws of the State of Delaware,
         with power and authority (corporate and other) to own its properties
         and conduct its business as described in the Prospectus; the merger of
         Frontier Software Development, Inc., a Massachusetts corporation, into
         the Company was duly and validly consummated; and the Company is duly
         qualified to do business as a foreign corporation in good standing in
         all other jurisdictions in which its ownership or lease of property or
         the conduct of its business requires such qualification and the failure
         to be so qualified would have a material adverse effect on the
         condition (financial or other), business, prospects, properties or
         results of operations of the Company and its subsidiaries, taken as
         whole ("MATERIAL ADVERSE EFFECT").

              (iv) Each subsidiary of the Company has been duly incorporated and
         is an existing corporation in good standing under the laws of the
         jurisdiction of its incorporation, with power and authority (corporate
         and other) to own its properties and conduct its business as described
         in the Prospectus; and each subsidiary of the Company is duly qualified
         to do business as a foreign corporation in good standing in all other
         jurisdictions in which its ownership or lease of property or the
         conduct of its business requires such qualification and the failure to
         be so qualified would have a Material Adverse Effect; all of the issued
         and outstanding capital stock of each subsidiary of the Company has
         been duly authorized and validly issued and is fully paid and
         nonassessable; and the capital stock of each subsidiary owned by the
         Company, directly or through subsidiaries, is owned free from liens,
         encumbrances and defects.

              (v) The Offered Securities and all other outstanding shares of
         capital stock of the Company have been duly authorized; all outstanding
         shares of capital stock of the Company are, and when the Offered
         Securities have been delivered and paid for in accordance with this
         Agreement on


                                      -3-



         each Closing Date (as defined below) will have been, validly issued,
         fully paid and nonassessable and will conform to the description
         thereof contained in the Prospectus; and neither the stockholders of
         the Company nor any other person has any preemptive rights with respect
         to the Offered Securities that have not been waived. The information
         set forth under the caption "Capitalization" in the Prospectus is true
         and correct. There are no outstanding options, warrants or other rights
         (that have not been waived) granted to or by the Company to purchase
         Offered Securities or other securities of the Company other than (i) as
         described in the Prospectus or (ii) options to purchase up to 175,000
         shares of Common Stock granted by the Company to employees and
         consultants in the ordinary course of business consistent with past
         practice.

              (vi) Except as disclosed in the Prospectus, there are no
         contracts, agreements or understandings between the Company and any
         person that would give rise to a valid claim against the Company or any
         Underwriter for a brokerage commission, finder's fee or other like
         payment in connection with this offering.

              (vii) Except as disclosed in the Prospectus, there are no
         contracts, agreements or understandings between the Company and any
         person granting such person the right to require the Company to file a
         registration statement under the Act with respect to any securities of
         the Company owned or to be owned by such person or to require the
         Company to include such securities in the securities registered
         pursuant to a Registration Statement or in any securities being
         registered pursuant to any other registration statement filed by the
         Company under the Act.

              (viii) The Securities have been approved for listing, subject to
         notice of issuance, on the Nasdaq Stock Market's National Market.

              (ix) No consent, approval, authorization, or order of, or filing
         with, any governmental agency or body or any court is required for the
         consummation of the transactions contemplated by this Agreement in
         connection with the issuance and sale of the Offered Securities, except
         such as have been obtained and made under the Act and such as may be
         required under state securities laws.

              (x) The execution, delivery and performance of this Agreement, and
         the consummation of the transactions herein contemplated will not
         result in a breach or violation of any of the terms and provisions of,
         or constitute a default under, (i) any statute, any rule, regulation or
         order of any governmental agency or body or any court, domestic or
         foreign, having jurisdiction over the Company or any subsidiary of the
         Company or any of their properties, (ii) any agreement or instrument to
         which the Company or any such subsidiary is a party or by which the
         Company or any such subsidiary is bound or to which any of the
         properties of the Company or any such subsidiary is subject and that is
         material to the Company and its subsidiaries, taken as a whole, or
         (iii) the charter or by-laws of the Company or any such subsidiary; and
         the Company has full power and authority to authorize, issue and sell
         the Securities to be sold by the Company as contemplated by this
         Agreement.

              (xi) This Agreement has been duly authorized, executed and
         delivered by the Company.

              (xii) Except as disclosed in the Prospectus, the Company and its
         subsidiaries have good and marketable title to all real properties and
         all other properties and assets owned by them which are material to the
         business of the Company and its subsidiaries, taken as a whole, in each
         case free from liens, encumbrances and defects that would materially
         affect the value thereof or materially interfere with the use made or
         to be made thereof by them; and except as disclosed in the Prospectus,
         the Company and its subsidiaries hold any leased real or personal
         property under valid and enforceable leases with no exceptions that
         would materially interfere with the use made or to be made thereof by
         them.


                                      -4-



              (xiii) The Company and its subsidiaries possess adequate
         certificates, authorities or permits issued by appropriate governmental
         agencies or bodies necessary to conduct the business now operated by
         them and have not received any notice of proceedings relating to the
         revocation or modification of any such certificate, authority or permit
         that, if determined adversely to the Company or any of its
         subsidiaries, would individually or in the aggregate have a Material
         Adverse Effect.

              (xiv) No labor dispute with the employees of the Company or any
         subsidiary exists or, to the knowledge of the Company, is imminent that
         might have a Material Adverse Effect.

              (xv) Except as disclosed in the Prospectus, (i) the Company and
         each of its subsidiaries have the right to use all trademarks, trade
         names, trade secrets, servicemarks, inventions, patent rights, mask
         works, copyrights, licenses, software code, audiovisual works, formats,
         algorithms and underlying data required to operate its business as
         presently being conducted and proposed to be conducted as described in
         the Prospectus, (ii) the Company and each of its subsidiaries have all
         required approvals and governmental authorizations now used in, or
         which are necessary for fulfillment of their respective obligations or
         the conduct of, their respective businesses as now conducted or
         proposed to be conducted as described in the Prospectus, except where
         the failure to have such approvals or authorizations do not have a
         Material Adverse Effect and (iii) neither the Company nor any of its
         subsidiaries is knowingly infringing any trademark, trade name rights,
         patent rights, mask works, copyrights, licenses, trade secret,
         servicemarks or other similar rights of others, and there is no claim
         being made against the Company or any of its subsidiaries regarding
         trademark, trade name, patent, mask work, copyright, license, trade
         secret or other infringement or assertion of intellectual property
         rights which could have a Material Adverse Effect. The Company has
         agreements in place with each employee, consultant or other person or
         party engaged by the Company or any subsidiary providing for the
         assignment to the Company or any of its subsidiaries, as the case may
         be, of all intellectual property and exploitation rights in the work
         performed and the protection of the trade secrets and confidential
         information of the Company, each of its subsidiaries and of third
         parties which have been developed by such person for or on behalf of
         the Company or any of its subsidiaries. The description of the
         Company's Year 2000 readiness under the caption "Management's
         Discussion and Analysis of Financial Condition and Results of
         Operations--Year 2000 Readiness Disclosure" in the Prospectus is
         accurate and complete in all material respects.

              (xvi) Except as disclosed in the Prospectus, neither the Company
         nor any of its subsidiaries is knowingly in violation of any statute,
         any rule, regulation, decision or order of any governmental agency or
         body or any court, domestic or foreign, relating to the use, disposal
         or release of hazardous or toxic substances or relating to the
         protection or restoration of the environment or human exposure to
         hazardous or toxic substances (collectively, "ENVIRONMENTAL LAWS"),
         owns or knowingly operates any real property contaminated with any
         substance that is subject to any environmental laws, is liable for any
         off-site disposal or contamination pursuant to any environmental laws,
         or is subject to any claim relating to any environmental laws, which
         violation, contamination, liability or claim would individually or in
         the aggregate have Material Adverse Effect; and the Company is not
         aware of any pending investigation which might lead to such a claim.

              (xvii) Except as disclosed in the Prospectus, there are no pending
         actions, suits or proceedings against or affecting the Company, any of
         its subsidiaries or any of their respective properties that, if
         determined adversely to the Company or any of its subsidiaries, would
         individually or in the aggregate have a Material Adverse Effect, or
         would materially and adversely affect the ability of the Company to
         perform its obligations under this Agreement, or which are otherwise
         material in the context of the sale of the Offered Securities; and,
         except as disclosed in the Prospectus, no


                                      -5-


         such actions, suits or proceedings have been threatened or, to the
         Company's knowledge, are contemplated.

              (xviii) The financial statements included in each Registration
         Statement and the Prospectus present fairly the financial position of
         the Company and its consolidated subsidiaries as of the dates shown and
         their results of operations and cash flows for the periods shown, and
         such financial statements have been prepared in conformity with the
         generally accepted accounting principles in the United States applied
         on a consistent basis; and the schedules included in each Registration
         Statement present fairly the information required to be stated therein;
         and the assumptions used in preparing the pro forma financial
         statements included in each Registration Statement and the Prospectus
         provide a reasonable basis for presenting the significant effects
         directly attributable to the transactions or events described therein,
         the related pro forma adjustments give appropriate effect to those
         assumptions, and the pro forma columns therein reflect the proper
         application of those adjustments to the corresponding historical
         financial statement amounts.

              (xix) Except as disclosed in the Prospectus, since the date of the
         latest audited financial statements included in the Prospectus there
         has been no material adverse change, nor any development or event
         involving a prospective material adverse change, in the condition
         (financial or other), business, properties or results of operations of
         the Company and its subsidiaries taken as a whole, and, except as
         disclosed in or contemplated by the Prospectus, there has been no
         dividend or distribution of any kind declared, paid or made by the
         Company on any class of its capital stock.

              (xx) The Company is not and, after giving effect to the offering
         and sale of the Offered Securities and the application of the proceeds
         thereof as described in the Prospectus, will not be an "investment
         company" as defined in the Investment Company Act of 1940.

              (xxi) The Company and each of its subsidiaries has filed all
         foreign, federal, state and local tax returns that are required to be
         filed or has requested extensions thereof (except in any case in which
         the failure so to file would not have a Material Adverse Effect) and
         the Company and each of its subsidiaries has paid all material taxes
         required to be paid by it and any other assessment, fine or penalty
         levied against it, to the extent that any of the foregoing is due and
         payable, except for any such assessment, fine or penalty that is
         currently being contested in good faith or as described in or
         contemplated by the Registration Statement or the Prospectus.

              (xxii) PricewaterhouseCoopers, LLP, who have audited the financial
         statements filed with the Commission as part of each Registration
         Statement, are independent public accountants as required by the Act
         and the Rules and Regulations. The Company maintains a system of
         internal accounting controls sufficient to provide reasonable
         assurances that (i) transactions are executed in accordance with
         management's general or specific authorization; (ii) transactions are
         recorded as necessary to permit preparation of financial statements in
         conformity with generally accepted accounting principles and to
         maintain accountability for assets; and (iii) access to assets is
         permitted only in accordance with management's general or specific
         authorization.

              (xxiii) The Company and each of its subsidiaries carry, or are
         covered by, insurance in such amounts and covering such risks as is
         adequate for the conduct of their respective businesses and the value
         of their respective properties and as is customary for companies
         engaged in similar industries.

              (xxiv) The Company and each of its subsidiaries are in compliance
         in all material respects with all presently applicable provisions of
         the Employee Retirement Income Security Act of 1974,


                                      -6-



         as amended, including the regulations thereunder ("ERISA"); no
         "reportable event" (as defined in ERISA) has occurred with respect to
         any "pension plan" (as defined in ERISA) for which the Company or any
         of its subsidiaries would have any liability; the Company and each of
         its subsidiaries have not incurred and do not expect to incur liability
         under (i) Title IV of ERISA with respect to termination of, or
         withdrawal from, any "pension plan" or (ii) Section 412 or 4971 of the
         Internal Revenue Code of 1986, as amended, including the regulations
         thereunder ("CODE"); and each "pension plan" for which the Company and
         each of its subsidiaries would have any liability that is intended to
         be qualified under Section 401(a) of the Code is so qualified in all
         material respects and nothing has occurred, whether by action or by
         failure to act, which would cause the loss of such qualification.

              (xxv) Except as set forth in each Registration Statement and the
         Prospectus, there are no agreements, claims, payments, issuances,
         arrangements or understandings, whether oral or written, for services
         in the nature of finder's, consulting or origination fees with respect
         to the sale of the Offered Securities or any other arrangements,
         agreements, understandings, payments or issuance with respect to the
         Company or any of its officers, directors, shareholders, partners,
         employees, subsidiaries or affiliates that may affect the Underwriters'
         compensation as determined by the National Association of Securities
         Dealers, Inc. (the "NASD").

              (xxvi) Except as set forth in each Registration Statement and the
         Prospectus and as is required to be disclosed in each Registration
         Statement and the Prospectus, no officer, director or shareholder of
         the Company or any "affiliate" or "associate" (as these terms are
         defined in Rule 405 under the Act) of any of the foregoing persons or
         entities has or has had, either directly or indirectly (i) an interest
         in any person or entity that (x) furnishes or sells services or
         products which are furnished or sold or that are proposed to be
         furnished or sold by the Company, or (y) purchases from or sells or
         furnishes to the Company any goods or services, or (ii) a beneficial
         interest in any contract or agreement to which the Company is a party
         or by which it may be bound or affected. Except as set forth in each
         Registration Statement and the Prospectus under the caption "Certain
         Transactions", "Management", "Description of Capital Stock" and Item
         16, Exhibits and Financial Statement Schedules and as is required to be
         disclosed in each Registration Statement and Prospectus, there are no
         existing or proposed agreements, arrangements, understandings or
         transactions, between or among the Company and any officer, director,
         principal shareholder of the Company or any partner, affiliate or
         associate of any of the foregoing persons or entities.

              (xxvii) The minute books of the Company made available to the
         Underwriters contain a complete summary of all meetings and actions of
         the directors and stockholders of the Company (including its
         predecessor Massachusetts corporation) since the time of its
         incorporation and reflect accurately and fairly in all respects all
         transactions referred to in such minutes.

         (b) Each Selling Stockholder severally and not jointly represents and
    warrants to, and agrees with, the several Underwriters that:

              (i) Such Selling Stockholder has and on each Closing Date
         hereinafter mentioned will have good, valid and unencumbered title to
         the Offered Securities to be delivered by such Selling Stockholder on
         such Closing Date and full right, power and authority to enter into
         this Agreement and to sell, assign, transfer and deliver the Offered
         Securities to be delivered by such Selling Stockholder on such Closing
         Date hereunder; and upon the delivery of and payment for the Offered
         Securities on each Closing Date hereunder the several Underwriters will
         acquire good, valid and unencumbered title to the Offered Securities to
         be delivered by such Selling Stockholder on such Closing Date.


                                      -7-



              (ii) Such Selling Stockholder has duly authorized (if applicable),
         executed and delivered, in the form heretofore furnished to the
         Representatives, an irrevocable Power of Attorney (the "Power of
         Attorney") appointing Anil K. Singhal, Narendra Popat and Charles W.
         Tillett as attorneys-in-fact (collectively, the "Attorneys" and
         individually, an "Attorney") and a Custody Agreement (the "Custody
         Agreement") with NetScout Systems, Inc., as custodian (the
         "Custodian"); each of the Power of Attorney and the Custody Agreement
         constitutes a valid and binding agreement on the part of such Selling
         Stockholder, enforceable in accordance with its terms, except as the
         enforcement thereof may be limited by applicable bankruptcy,
         insolvency, reorganization, moratorium or other similar laws relating
         to or affecting creditors' rights generally or by general equitable
         principles; and each of such Selling Stockholder's Attorneys, acting
         alone, is authorized to execute and deliver this Agreement and such
         certificates as the Representatives shall reasonably request at the
         Closing on behalf of such Selling Stockholder, to determine the
         purchase price to be paid by the several Underwriters to such Selling
         Stockholder, to authorize the delivery of the Offered Securities to be
         sold by such Selling Stockholder under this Agreement and to duly
         endorse (in blank or otherwise) the certificate or certificates
         representing such Securities or a stock power or powers with respect
         thereto, to accept payment therefor, and otherwise to act on behalf of
         such Selling Stockholder in connection with this Agreement.

              (iii) All consents, approvals, authorizations and orders required
         for the execution and delivery by such Selling Stockholder of the Power
         of Attorney and the Custody Agreement, the execution and delivery by or
         on behalf of such Selling Stockholder of this Agreement and the sale
         and delivery of the Offered Securities to be sold by such Selling
         Stockholder under this Agreement (other than, at the time of the
         execution hereof (if the Registration Statement has not yet been
         declared effective by the Commission) the issuance of the order of the
         Commission declaring the Registration Statement effective and such
         filings required under Rule 424(b) promulgated under the Securities Act
         and such consents, approvals, authorizations or orders as may be
         necessary under state or other securities or Blue Sky laws) have been
         obtained and are in full force and effect; such Selling Stockholder, if
         other than a natural person, has been duly organized and is validly
         existing in good standing under the laws of the jurisdiction of its
         organization as the type of entity that it purports to be; and such
         Selling Stockholder has full legal right, power and authority to enter
         into and perform its obligations under this Agreement and such Power of
         Attorney and Custody Agreement, and to sell, assign, transfer and
         deliver the Securities to be sold by such Selling Stockholder under
         this Agreement.

              (iv) Certificates in negotiable form for all Securities to be sold
         by such Selling Stockholder under this Agreement, together with a stock
         power or powers duly endorsed in blank by such Selling Stockholder,
         have been placed in custody with the Custodian for the purpose of
         effecting delivery hereunder.

              (v) This Agreement has been duly authorized by each Selling
         Stockholder that is not a natural person and has been duly executed and
         delivered by or on behalf of such Selling Stockholder and is a valid
         and binding agreement of such Selling Stockholder, enforceable in
         accordance with its terms, except as rights to indemnification
         hereunder may be limited by applicable law and except as the
         enforcement hereof may be limited by bankruptcy, insolvency,
         reorganization, moratorium or other similar laws relating to or
         affecting creditors' rights generally or by general equitable
         principles; and the performance of this Agreement and the consummation
         of the transactions herein contemplated will not result in a material
         breach or violation of any of the terms and provisions of or constitute
         a default under any material bond, debenture, note or other evidence of
         indebtedness, or under any material lease, contract, indenture,
         mortgage, deed of trust, loan agreement, joint venture or other
         agreement or instrument to which such Selling Stockholder is a party or
         by which such Selling Stockholder, or any Offered Securities to be sold
         by such Selling Stockholder hereunder, may be bound or, to the best of
         such Selling Stockholders'


                                      -8-



         knowledge, result in any violation of any law, order, rule, regulation,
         writ, injunction, judgment or decree of any court, government or
         governmental agency or body, domestic or foreign, having jurisdiction
         over such Selling Stockholder or over the properties of such Selling
         Stockholder, or, if such Selling Stockholder is other than a natural
         person, result in any violation of any provisions of the charter,
         bylaws or other organizational documents of such Selling Stockholder.

              (vi) Such Selling Stockholder has not taken and will not take,
         directly or indirectly, any action designed to or that might reasonably
         be expected to cause or result in stabilization or manipulation of the
         price of the Common Stock to facilitate the sale or resale of the
         Securities.

              (vii) Such Selling Stockholder has not distributed and will not
         distribute any prospectus or other offering material in connection with
         the offering and sale of the Securities.

              (viii) Such Selling Stockholder does not have, or has waived prior
         to the date hereof, any preemptive right, co-sale right or right of
         first refusal or other similar right to purchase any of the Offered
         Securities that are to be sold by the Company or any of the other
         Selling Stockholders to the Underwriters pursuant to this Agreement;
         such Selling Stockholder does not have, or has waived prior to the date
         hereof, any registration right or other similar right to participate in
         the offering made by the Prospectus, other than such rights of
         participation as have been satisfied by the participation of such
         Selling Stockholder in the transactions to which this Agreement relates
         in accordance with the terms of this Agreement; and such Selling
         Stockholder does not own any warrants, options or similar rights to
         acquire, and does not have, or has waived prior to the date hereof, any
         right or arrangement to acquire, any capital stock, rights, warrants,
         options or other securities from the Company, other than those
         described in the Registration Statement and the Prospectus or those
         issued pursuant to the Company's option plans described in the
         Prospectus.

              (ix) The information regarding such Selling Stockholder under the
         caption "Principal and Selling Stockholders" and "Certain Transactions"
         in the Registration Statement is true and correct in all material
         respects.

              (x) Except as disclosed in the Prospectus, there are no contracts,
         agreements or understandings between such Selling Stockholder and any
         person that would give rise to a valid claim against such Selling
         Stockholder or any Underwriter for a brokerage commission, finder's
         fee or other like payment in connection with this offering.

         In addition, each Selling Stockholder, other than Greylock Equity
Limited Partnership ("Greylock"), severally and not jointly, represents and
warrants to, and agrees with, the several Underwriters that, without having
undertaken to determine independently the accuracy or completeness of the
information contained in the Registration Statement, such Selling Stockholder
has reviewed the Registration Statement and Prospectus and nothing has come to
the attention of such Selling Stockholder that would lead such Selling
Stockholder to believe that either (A) on the Effective Date, the Registration
Statement contained any untrue statement of a material fact or omitted to state
any material fact required to be stated therein or necessary in order to make
the statements therein in light of the circumstances under which they were made
not misleading, or (B) on the Effective Date the Prospectus did not and, on the
Closing Date and any later date on which Optional Securities are to be purchased
will not, contain any untrue statement of a material fact or omitted or omits to
state any material fact necessary in order to make the statements therein, in
the light of the circumstances under which they were made, not misleading.

         3. PURCHASE, SALE AND DELIVERY OF OFFERED SECURITIES. On the basis of
the representations, warranties and agreements herein contained, but subject to
the terms and conditions herein set forth, the Company agrees to sell to each
Underwriter, and each Underwriter agrees, severally and not jointly, to


                                      -9-



purchase from the Company at a purchase price of $       per share, that
number of Firm Securities set forth opposite the name of such Underwriter
in Schedule B.

         Certificates in negotiable form for the Offered Securities to be sold
by the Selling Stockholders hereunder have been placed in custody, for delivery
under this Agreement, under Custody Agreements made with NetScout Systems, Inc.,
as custodian ("CUSTODIAN"). Each Selling Stockholder agrees that the shares
represented by the certificates held in custody for the Selling Stockholders
under such Custody Agreements are subject to the interests of the Underwriters
hereunder, that the arrangements made by the Selling Stockholders for such
custody are to that extent irrevocable, and that the obligations of the Selling
Stockholders hereunder shall not be terminated by operation of law, whether by
the death of any individual Selling Stockholder or the occurrence of any other
event, or in the case of a trust, by the death of any trustee or trustees or the
termination of such trust. If any individual Selling Stockholder or any such
trustee or trustees should die, or if any other such event should occur, or if
any of such trusts should terminate, before the delivery of the Offered
Securities hereunder, certificates for such Offered Securities shall be
delivered by the Custodian in accordance with the terms and conditions of this
Agreement as if such death or other event or termination had not occurred,
regardless of whether or not the Custodian shall have received notice of such
death or other event or termination.

         The Company will deliver the Firm Securities to the Representatives
for the accounts of the Underwriters, at the office of Testa, Hurwitz &
Thibeault, LLP, against payment of the purchase price in Federal (same day)
funds by official bank check or checks or wire transfer to an account at a
bank designated by the Company drawn to the order of NetScout Systems, Inc.,
at 9:30 A.M., New York time, on August   , 1999, or at such other time not
later than seven full business days thereafter as Deutsche Banc Alex. Brown
("DEUTSCHE BANC") and the Company determine, such time being herein referred
to as the "FIRST CLOSING DATE". For purposes of Rule 15c6-1 under the
Securities Exchange Act of 1934, as amended, the First Closing Date (if later
than the otherwise applicable settlement date) shall be the settlement date
for payment of funds and delivery of securities for all the Firm Securities
sold pursuant to the offering. The certificates for the Firm Securities so to
be delivered will be in definitive form, in such denominations and registered
in such names as Deutsche Banc requests and will be made available for
checking and packaging at such location as Deutsche Banc shall reasonably
request at least 24 hours prior to the First Closing Date.

         In addition, upon written notice from Deutsche Banc given to the
Company and the Selling Stockholders from time to time not more than 30 days
subsequent to the date of the Prospectus, the Underwriters may purchase all or
less than all of the Optional Securities at the purchase price per Offered
Security to be paid for the Firm Securities. The Selling Stockholders agree,
severally and not jointly, to sell to the Underwriters the respective numbers of
Optional Securities obtained by multiplying the number of Optional Securities
specified in such notice by a fraction the numerator of which is the number of
shares set forth opposite the names of such Selling Stockholders in Schedule A
hereto under the caption "Number of Optional Securities to be Sold" and the
denominator of which is the total number of Optional Securities (subject to
adjustment by Deutsche Banc to eliminate fractions). Such Optional Securities
shall be purchased from each Selling Stockholder for the account of each
Underwriter in the same proportion as the number of Firm Securities set forth
opposite such Underwriter's name bears to the total number of Firm Securities
(subject to adjustment by Deutsche Banc to eliminate fractions) and may be
purchased by the Underwriters only for the purpose of covering over-allotments
made in connection with the sale of the Firm Securities. No Optional Securities
shall be sold or delivered unless the Firm Securities previously have been, or
simultaneously are, sold and delivered. The right to purchase the Optional
Securities or any portion thereof may be exercised from time to time and to the
extent not previously exercised may be surrendered and terminated at any time
upon notice by Deutsche Banc to the Company and the Selling Stockholders.

         Each time for the delivery of and payment for the Optional Securities,
being herein referred to as an "OPTIONAL CLOSING DATE", which may be the First
Closing Date (the First Closing Date and each


                                      -10-



Optional Closing Date, if applicable, being sometimes referred to as a "CLOSING
DATE"), shall be determined by Deutsche Banc but shall be not later than five
full business days after written notice of election to purchase Optional
Securities is given. The Company and the Custodian will deliver the Optional
Securities being purchased on each Optional Closing Date to the Representatives
for the accounts of the several Underwriters, at the office of Testa, Hurwitz &
Thibeault, LLP, against payment of the purchase price therefor in Federal (same
day) funds by official bank check or checks or wire transfer to an account at a
bank designated by the Custodian drawn to the order of the Custodian, for the
account of the Selling Stockholders, in the case of the Optional Securities sold
by the Selling Stockholders. The certificates for the Optional Securities being
purchased on each Optional Closing Date will be in definitive form, in such
denominations and registered in such names as Deutsche Banc requests upon
reasonable notice prior to such Optional Closing Date and will be made available
for checking and packaging at such location as Deutsche Banc shall reasonably
request at a reasonable time in advance of such Optional Closing Date.

         4. OFFERING BY UNDERWRITERS. It is understood that the several
Underwriters propose to offer the Offered Securities for sale to the public as
set forth in the Prospectus.

         5. CERTAIN AGREEMENTS OF THE COMPANY AND THE SELLING STOCKHOLDERS. The
Company agrees and each of the Selling Stockholders (with respect to
subparagraphs (i) and (j) below) agrees with the several Underwriters that:

              (a) If the Effective Time of the Initial Registration Statement is
         prior to the execution and delivery of this Agreement, the Company will
         file the Prospectus with the Commission pursuant to and in accordance
         with subparagraph (1) (or, if applicable and if consented to by
         Deutsche Banc, subparagraph (4)) of Rule 424(b) not later than the
         earlier of (A) the second business day following the execution and
         delivery of this Agreement or (B) the fifteenth business day after the
         Effective Date of the Initial Registration Statement.

         The Company will advise Deutsche Banc promptly of any such filing
         pursuant to Rule 424(b). If the Effective Time of the Initial
         Registration Statement is prior to the execution and delivery of this
         Agreement and an additional registration statement is necessary to
         register a portion of the Offered Securities under the Act but the
         Effective Time thereof has not occurred as of such execution and
         delivery, the Company will file the additional registration statement
         or, if filed, will file a post-effective amendment thereto with the
         Commission pursuant to and in accordance with Rule 462(b) on or prior
         to 10:00 P.M., New York time, on the date of this Agreement or, if
         earlier, on or prior to the time the Prospectus is printed and
         distributed to any Underwriter, or will make such filing at such later
         date as shall have been consented to by Deutsche Banc.

              (b) The Company will advise Deutsche Banc promptly of any proposal
         to amend or supplement the initial or any additional registration
         statement as filed or the related prospectus or the Initial
         Registration Statement, the Additional Registration Statement (if any)
         or the Prospectus and will not effect such amendment or supplementation
         without Deutsche Banc's consent, which consent shall not be
         unreasonably withheld; and the Company will also advise Deutsche Banc
         promptly of the effectiveness of each Registration Statement (if its
         Effective Time is subsequent to the execution and delivery of this
         Agreement) and of any amendment or supplementation of a Registration
         Statement or the Prospectus and of the institution by the Commission of
         any stop order proceedings in respect of a Registration Statement and
         will use its best efforts to prevent the issuance of any such stop
         order and to obtain as soon as possible its lifting, if issued.

              (c) If, at any time when a prospectus relating to the Offered
         Securities is required to be delivered under the Act in connection with
         sales by any Underwriter or dealer, any event occurs as a result of
         which the Prospectus as then amended or supplemented would include an
         untrue statement of a material fact or omit to state any material fact
         necessary to make the statements


                                      -11-



         therein, in the light of the circumstances under which they were made,
         not misleading, or if it is necessary at any time to amend the
         Prospectus to comply with the Act, the Company will promptly notify
         Deutsche Banc of such event and will promptly prepare and file with the
         Commission, at its own expense, an amendment or supplement which will
         correct such statement or omission or an amendment which will effect
         such compliance. Neither Deutsche Banc's consent to, nor the
         Underwriters' delivery of, any such amendment or supplement shall
         constitute a waiver of any of the conditions set forth in Section 6.

              (d) As soon as practicable, but not later than the Availability
         Date (as defined below), the Company will make generally available to
         its securityholders an earnings statement covering a period of at least
         12 months beginning after the Effective Date of the Initial
         Registration Statement (or, if later, the Effective Date of the
         Additional Registration Statement) which will satisfy the provisions of
         Section 11(a) of the Act. For the purpose of the preceding sentence,
         "AVAILABILITY DATE" means the 45th day after the end of the fourth
         fiscal quarter following the fiscal quarter that includes such
         Effective Date, except that, if such fourth fiscal quarter is the last
         quarter of the Company's fiscal year, "AVAILABILITY DATE" means the
         90th day after the end of such fourth fiscal quarter.

              (e) The Company will furnish to the Representatives copies of each
         Registration Statement (one of which will be signed and will include
         all exhibits), each related preliminary prospectus, and, so long as a
         prospectus relating to the Offered Securities is required to be
         delivered under the Act in connection with sales by any Underwriter or
         dealer, the Prospectus and all amendments and supplements to such
         documents, in each case in such quantities as Deutsche Banc requests.
         The Prospectus shall be so furnished on or prior to 3:00 P.M., New York
         time, on the business day following the later of the execution and
         delivery of this Agreement or the Effective Time of the Initial
         Registration Statement. All other such documents shall be so furnished
         as soon as available. The Company and the Selling Stockholders will pay
         the expenses of printing and distributing to the Underwriters all such
         documents.

              (f) The Company will arrange for the qualification of the Offered
         Securities for sale under the laws of such jurisdictions as Deutsche
         Banc designates and will continue such qualifications in effect so long
         as required for the distribution; provided, however, that the Company
         shall not be obliged to file any general consent to service of process
         or to qualify as a foreign corporation or as a securities dealer in any
         jurisdiction or to subject itself to taxation in respect of doing
         business in any jurisdiction in which it is not otherwise so subject.

              (g) During the period of five years hereafter, the Company will
         furnish to the Representatives and, upon request, to each of the other
         Underwriters, as soon as practicable after the end of each fiscal year,
         a copy of its annual report to stockholders for such year; and the
         Company will furnish to the Representatives (i) as soon as available, a
         copy of each report and any definitive proxy statement of the Company
         filed with the Commission under the Securities Exchange Act of 1934 or
         mailed to stockholders, and (ii) from time to time, such other
         information concerning the Company as Deutsche Banc may reasonably
         request.

              (h) For a period of 180 days after the Effective Date, the Company
         will not offer, sell, contract to sell, grant any option to purchase,
         pledge or otherwise dispose of or transfer, directly or indirectly, or
         file with the Commission a registration statement (other than a
         Registration Statement on Form S-8) under the Act relating to, any
         additional shares of its securities or securities convertible into or
         exchangeable or exercisable for any shares of its securities, or
         publicly disclose the intention to make any such offer, sale, pledge,
         disposition or filing, without the prior written consent of Deutsche
         Banc, except for the sale by the Company of the Offered Securities to
         the Underwriters, the issuances of securities pursuant to the
         conversion of convertible


                                      -12-



         securities or the exercise of warrants or options, in each case
         outstanding on the date hereof, or grants of director, consultant and
         employee stock options or stock pursuant to the terms of a plan in
         effect on the Closing Date and described in the Prospectus, or
         issuances of securities pursuant to the exercise of such options.

              (i) The Company and each Selling Stockholder agree with the
         several Underwriters that the Company and such Selling Stockholder will
         pay all expenses incident to the performance of the obligations of the
         Company and such Selling Stockholder, as the case may be, under this
         Agreement, including, without limitation, for any filing fees and other
         expenses (including reasonable fees and disbursements of counsel) in
         connection with qualification of the Offered Securities for sale under
         the laws of such jurisdictions as Deutsche Banc designates and the
         printing of memoranda relating thereto, for the filing fee incident to,
         and the reasonable fees and disbursements of counsel to the
         Underwriters in connection with, the review by the NASD of the Offered
         Securities, for any travel expenses of the Company's officers and
         employees and any other expenses of the Company in connection with
         attending or hosting meetings with prospective purchasers of the
         Offered Securities, for any transfer taxes on the sale by the Selling
         Stockholders of the Offered Securities to the Underwriters and for
         expenses incurred in distributing preliminary prospectuses and the
         Prospectus (including any amendments and supplements thereto) to the
         Underwriters. Notwithstanding the provisions of the foregoing
         paragraph, each Selling Stockholder shall be responsible for his, her
         or its own transfer taxes.

              (j) Each Selling Stockholder agrees to deliver to Deutsche Banc,
         attention: Transactions Advisory Group on or prior to the First Closing
         Date a properly completed and executed United States Treasury
         Department Form W-9 (or other applicable form or statement specified by
         Treasury Department regulations in lieu thereof).

         6. CONDITIONS OF THE OBLIGATIONS OF THE UNDERWRITERS. The obligations
of the several Underwriters to purchase and pay for the Firm Securities on the
First Closing Date and the Optional Securities to be purchased on each Optional
Closing Date will be subject to the accuracy of the representations and
warranties on the part of the Company and the Selling Stockholders herein, to
the accuracy of the statements of Company officers made pursuant to the
provisions hereof, to the performance by the Company and the Selling
Stockholders of their obligations hereunder and to the following additional
conditions precedent:

              (a) The Representatives shall have received from
         PricewaterhouseCoopers, LLP a letter dated the date hereof and each
         Closing Date, in form and substance satisfactory to the
         Representatives, together with signed or reproduced copies of such
         letter for each of the Underwriters containing statements and
         information of the type ordinarily included in accountants' "comfort
         letters" to underwriters with respect to the financial statements and
         certain information contained in each Registration Statement and the
         Prospectus.

              In the event that the letters referred to above set forth any
         changes in capital stock, increases in short-term or long-term debt or
         decreases in net current assets, net assets, revenues, net income or
         net income per share as reflected on the most recently available
         financial statements not included in the Prospectus as compared to the
         corresponding date or period of the prior year and as compared to the
         most recent date and the most recent period of corresponding length
         included in the financial statements included in the Prospectus, it
         shall be a further condition to the obligations of the Underwriters
         that (i) such letters shall be accompanied by a written explanation of
         the Company as to the significance thereof, unless the Representatives
         deem such explanation unnecessary, and (ii) such changes, decreases or
         increases do not, in the sole judgment of the Representatives, make it
         impractical or inadvisable to proceed with the purchase and delivery of


                                      -13-



         the Offered Securities as contemplated by such Registration Statement,
         as amended as of the date hereof.

              (b) If the Effective Time of the Initial Registration Statement is
         not prior to the execution and delivery of this Agreement, such
         Effective Time shall have occurred not later than 10:00 P.M., New York
         time, on the date of this Agreement or such later date as shall have
         been consented to by Deutsche Banc. If the Effective Time of the
         Additional Registration Statement (if any) is not prior to the
         execution and delivery of this Agreement, such Effective Time shall
         have occurred not later than 10:00 P.M., New York time, on the date of
         this Agreement or, if earlier, the time the Prospectus is printed and
         distributed to any Underwriter, or shall have occurred at such later
         date as shall have been consented to by Deutsche Banc. If the Effective
         Time of the Initial Registration Statement is prior to the execution
         and delivery of this Agreement, the Prospectus shall have been filed
         with the Commission in accordance with the Rules and Regulations and
         Section 5(a) of this Agreement. Prior to such Closing Date, no stop
         order suspending the effectiveness of a Registration Statement shall
         have been issued and no proceedings for that purpose shall have been
         instituted or, to the knowledge of any Selling Stockholder, the Company
         or the Representatives, shall be contemplated by the Commission.

              (c) Subsequent to the execution and delivery of this Agreement,
         there shall not have occurred (i) any change, or any development or
         event involving a prospective change, in the condition (financial or
         other), business, properties or results of operations of the Company or
         its subsidiaries taken as one enterprise which, in the judgment of a
         majority in interest of the Underwriters including the Representatives,
         is material and adverse and makes it impractical or inadvisable to
         proceed with completion of the public offering or the sale of and
         payment for the Offered Securities; (ii) any downgrading in the rating
         of any debt securities of the Company by any "nationally recognized
         statistical rating organization" (as defined for purposes of Rule
         436(g) under the Act), or any public announcement that any such
         organization has under surveillance or review its rating of any debt
         securities of the Company (other than an announcement with positive
         implications of a possible upgrading, and no implication of a possible
         downgrading, of such rating); (iii) any suspension or limitation of
         trading in securities generally on the New York Stock Exchange or any
         setting of minimum prices for trading on such exchange, or any
         suspension of trading of any securities of the Company on any exchange
         or in the over-the-counter market; (iv) any banking moratorium declared
         by U.S. Federal or New York authorities; or (v) any outbreak or
         escalation of major hostilities in which the United States is involved,
         any declaration of war by Congress or any other substantial national or
         international calamity or emergency if, in the judgment of a majority
         in interest of the Underwriters including the Representatives, the
         effect of any such outbreak, escalation, declaration, calamity or
         emergency makes it impractical or inadvisable to proceed with
         completion of the public offering or the sale of and payment for the
         Offered Securities.

              (d) The Representatives shall have received an opinion, dated such
         Closing Date, of Testa, Hurwitz & Thibeault, LLP, counsel for the
         Company, to the effect that:

                  (i) The Company has been duly incorporated and is an existing
              corporation in good standing under the laws of the State of
              Delaware, with corporate power and authority to own its properties
              and conduct its business as described in the Prospectus; the
              merger of Frontier Software Development, Inc., a Massachusetts
              corporation, into the Company was duly and validly consummated;
              and the Company is duly qualified to do business as a foreign
              corporation in Massachusetts, Arizona, California, Colorado,
              Florida, Georgia, Illinois, Kentucky, Maryland, Michigan,
              Minnesota, New Hampshire, New Jersey, New York, North Carolina,
              Ohio, Oregon, Pennsylvania, Texas, Virginia, and Washington;


                                      -14-



                  (ii) The Offered Securities delivered on such Closing Date and
              all other outstanding shares of the Common Stock of the Company
              have been duly authorized and validly issued, are fully paid and
              nonassessable and conform in all material respects to the
              description thereof contained in the Prospectus; the Company has
              authorized and outstanding capital stock as set forth under the
              caption "Capitalization" in the Prospectus as of the date
              specified therein; the certificates for the Offered Securities,
              assuming they are in the form filed with the Commission, are in
              due and proper form; and no stockholder of the Company or any
              other person has any preemptive rights with respect to the Offered
              Securities pursuant to the Delaware General Corporation Law, the
              Company's Certificate of Incorporation, By-laws, or to such
              counsel's knowledge, any agreement with the Company that have not
              been waived;

                  (iii) Except as described in or contemplated by the
              Prospectus, to the knowledge of such counsel, there are no
              outstanding securities of the Company convertible or exchangeable
              into or evidencing the right to purchase or subscribe for any
              shares of capital stock of the Company and there are no
              outstanding or authorized options, warrants or other securities
              obligating the Company to issue any shares of its capital stock or
              any securities convertible or exchangeable into or evidencing the
              right to purchase or subscribe for any shares of such capital
              stock;

                  (iv) Except as disclosed in the Prospectus, there are no
              contracts, agreements or understandings known to such counsel
              between the Company and any person granting such person the right
              to require the Company to file a registration statement under the
              Act with respect to any securities of the Company owned or to be
              owned by such person or to require the Company to include such
              securities in the securities registered pursuant to the
              Registration Statement or in any securities being registered
              pursuant to any other registration statement filed by the Company
              under the Act which have not been waived;

                  (v) The Company is not and, after giving effect to the
              offering and sale of the Offered Securities and the application of
              the proceeds thereof as described in the Prospectus, will not be
              an "investment company" as defined in the Investment Company Act
              of 1940, as amended.

                  (vi) No consent, approval, authorization or order of, or
              filing with, any governmental agency or body or any court is
              required to be obtained or made by the Company for the
              consummation of the transactions contemplated by this Agreement or
              the Custody Agreement in connection with the issuance or sale of
              the Offered Securities, except such as have been obtained and made
              under the Act (except that such counsel need express no opinion as
              to state securities laws);

                  (vii) The execution, delivery and performance of this
              Agreement or the Custody Agreement and the consummation of the
              transactions herein or therein contemplated will not result in (a)
              a material breach or violation of any of the terms and provisions
              of, or constitute a default under, any statute, any rule,
              regulation or order of any governmental agency or body or any
              court having jurisdiction over the Company or any U.S. subsidiary
              of the Company or any of their properties (except that such
              counsel need express no opinion as to state securities laws), or
              any agreement or instrument listed in the exhibit index to the
              Registration Statement to which the Company or any such U.S.
              subsidiary is a party or by which the Company or any such U.S.
              subsidiary is bound or to which any of the properties of the
              Company or any such subsidiary is subject, or (b) a breach or
              violation of the charter or by-laws of the Company or any such
              U.S. subsidiary; and the Company has the corporate power and
              authority to authorize issue and sell the securities to be sold by
              the Company as contemplated by this Agreement;


                                      -15-



                  (viii) The Initial Registration Statement was declared
              effective under the Act as of the date and time specified in such
              opinion, the Additional Registration Statement (if any) was filed
              and became effective under the Act as of the date and time (if
              determinable) specified in such opinion, the Prospectus either was
              filed with the Commission pursuant to the subparagraph of Rule
              424(b) specified in such opinion on the date specified therein or
              was included in the Initial Registration Statement or the
              Additional Registration Statement (as the case may be), and, to
              the knowledge of such counsel after due inquiry, no stop order
              suspending the effectiveness of a Registration Statement or any
              part thereof has been issued and no proceedings for that purpose
              have been instituted or are pending or contemplated under the Act,
              and each Registration Statement and the Prospectus, and each
              amendment or supplement thereto, as of their respective effective
              or issue dates, complied as to form in all material respects with
              the requirements of the Act and the Rules and Regulations; such
              counsel has no reason to believe that any part of a Registration
              Statement or any amendment thereto, as of its effective date or as
              of such Closing Date, contained any untrue statement of a material
              fact or omitted to state any material fact required to be stated
              therein or necessary to make the statements therein not
              misleading; or that the Prospectus or any amendment or supplement
              thereto, as of its issue date or as of such Closing Date,
              contained any untrue statement of a material fact or omitted to
              state any material fact necessary in order to make the statements
              therein, in the light of the circumstances under which they were
              made, not misleading; and the descriptions in the Registration
              Statements and Prospectus of United States statutes, legal and
              governmental proceedings and contracts and other documents are
              accurate in all material respects and fairly present the
              information required to be shown; it being understood that such
              counsel need express no opinion as to the financial statements or
              schedules or other financial data contained in the Registration
              Statements or the Prospectus;

                  (ix) This Agreement has been duly authorized, executed and
              delivered by the Company;

                  (x) All of the Offered Securities have been duly authorized
              for quotation on the Nasdaq National Market, subject to official
              notice of issuance; and

                  (xi) Such counsel does not know of any legal or governmental
              proceedings or investigations pending or threatened to which the
              Company or any of its U.S. subsidiaries is a party or to which the
              property of the Company or any of its subsidiaries is subject that
              are required to be described in any Registration Statement or the
              Prospectus and are not described therein or any statutes,
              regulations, contracts or other documents that are required to be
              described in any Registration Statement or the Prospectus or to be
              filed as exhibits to any Registration Statement that are not
              described therein or filed as required.

                  With respect to subparagraph (viii) of paragraph (d) above,
              Testa, Hurwitz & Thibeault, LLP may state that their opinion and
              belief are based upon their participation in the preparation of
              the Registration Statement and Prospectus and any amendments or
              supplements thereto and review and discussion of the contents
              thereof, but are without independent check or verification.

              (e) The Representatives shall have received an opinion, dated any
         such Optional Closing Date, of Testa, Hurwitz & Thibeault, LLP, counsel
         for the Selling Stockholders who are natural persons (the "Individual
         Selling Stockholders"), to the effect that:

                  (i) Upon the Underwriters obtaining control of the Offered
              Securities to be sold by the Individual Selling Stockholders, and
              assuming that the Underwriters acquired such Offered Securities
              for value and without notice of any adverse claim to such Offered
              Securities within the meaning of Section 8-102 of the Uniform
              Commercial Code as in effect in the


                                      -16-



              Commonwealth of Massachusetts, the Underwriters will have acquired
              all rights of the Individual Selling Stockholders in such Offered
              Securities free of any adverse claim;

                  (ii) No consent, approval, authorization or order of, or
              filing with, any governmental agency or body or any court is
              required to be obtained or made by any Individual Selling
              Stockholder for the consummation of the transactions contemplated
              by the Custody Agreement or this Agreement in connection with the
              sale of the Offered Securities sold by the Individual Selling
              Stockholders, except such as have been obtained and made under the
              Act and such as may be required under state securities laws;

                  (iii) The execution, delivery and performance of the Custody
              Agreement and this Agreement and the consummation of the
              transactions therein and herein contemplated will not result in a
              breach or violation of any of the terms and provisions of, or
              constitute a default under, any statute, any rule, regulation or
              order of any governmental agency or body or any court having
              jurisdiction over any Individual Selling Stockholder or any of
              their properties;

                  (iv) The Power of Attorney and related Custody Agreement with
              respect to each Individual Selling Stockholder has been duly
              authorized, executed and delivered by such Individual Selling
              Stockholder and constitute valid and legally binding obligations
              of each such Individual Selling Stockholder enforceable in
              accordance with their terms, subject to bankruptcy, insolvency,
              fraudulent transfer, reorganization, moratorium and similar laws
              of general applicability relating to or affecting creditors'
              rights and to general equity principles; and

                  (v) This Agreement has been duly executed and delivered by
              each Individual Selling Stockholder.

              (e) The Representatives shall have received an opinion, dated any
         such Optional Closing Date, of Goodwin, Procter & Hoar, LLP, counsel
         for the TA Entities (as defined in the Prospectus) and of Hale and Dorr
         LLP, special counsel to Greylock, to the effect that:

                  (i) To such counsel's knowledge, each of the TA Entities or
              Greylock, as the case may be, had valid and unencumbered title to
              the Offered Securities delivered by such Selling Stockholder on
              such Closing Date and had full right, power and authority to sell,
              assign, transfer and deliver the Offered Securities delivered by
              such Individual Selling Stockholder on such Closing Date
              hereunder; and upon delivery to the Underwriters of a certificate
              or certificates for the Offered Securities that are being sold by
              each Selling Stockholder under this Agreement and payment for such
              Offered Securities by the Underwriters, each Underwriter will
              acquire all of the rights of such Selling Stockholder in such
              Offered Securities, and each Underwriter will also acquire each of
              the Offered Securities free of any "adverse claim" (within the
              meaning of Section 8-102 of the Uniform Commercial Code);

                  (ii) No consent, approval, authorization or order of, or
              filing with, any governmental agency or body or any court is
              required to be obtained or made by any TA Entity or Greylock, as
              the case may be, for the consummation of the transactions
              contemplated by the Custody Agreement or this Agreement in
              connection with the sale of the Offered Securities sold by the TA
              Entities or Greylock, as the case may be, except such as have been
              obtained and made under the Act and such as may be required under
              state securities laws;

                  (iii) The execution, delivery and performance of the Custody
              Agreement and this Agreement and the consummation of the
              transactions therein and herein contemplated will not result in a
              breach or violation of any of the terms and provisions of, or
              constitute a default


                                      -17-



              under, any statute, any rule, regulation or order of any
              governmental agency or body or any court having jurisdiction over
              any TA Entity or Greylock, as the case may be, or any of their
              properties or any agreement or instrument to which any TA Entity
              or Greylock, as the case may be, is a party or by which any TA
              Entity or Greylock, as the case may be, is bound or to which any
              of the properties of any TA Entity or Greylock, as the case may
              be, is subject and as set forth on EXHIBIT A attached to such
              counsel's opinion;

                  (iv) The Power of Attorney and related Custody Agreement with
              respect to each TA Entity or Greylock, as the case may be, has
              been duly authorized, executed and delivered by such Selling
              Stockholder and constitute valid and legally binding obligations
              of each such Selling Stockholder enforceable in accordance with
              their terms, subject to bankruptcy, insolvency, fraudulent
              transfer, reorganization, moratorium and similar laws of general
              applicability relating to or affecting creditors' rights and to
              general equity principles; and

                  (v) This Agreement has been duly authorized, executed and
              delivered by each such Selling Stockholder.

              (g) The Representatives shall have received from Hale and Dorr
         LLP, counsel for the Underwriters, such opinion or opinions, dated such
         Closing Date, with respect to the incorporation of the Company, the
         validity of the Offered Securities delivered on such Closing Date, the
         Registration Statements, the Prospectus and other related matters as
         the Representatives may require, and the Selling Stockholders and the
         Company shall have furnished to such counsel such documents as they
         request for the purpose of enabling them to pass upon such matters. In
         rendering such opinion, Hale and Dorr LLP may rely as to the
         incorporation of the Company upon the opinion of Testa, Hurwitz &
         Thibeault, LLP.

              (h) The Representatives shall have received a certificate, dated
         such Closing Date, of the President or any Vice President and a
         principal financial or accounting officer of the Company in which such
         officers, to the best of their knowledge after reasonable
         investigation, shall state that: the representations and warranties of
         the Company in this Agreement are true and correct; the Company has
         complied with all agreements and satisfied all conditions on its part
         to be performed or satisfied hereunder at or prior to such Closing
         Date; no stop order suspending the effectiveness of any Registration
         Statement has been issued and no proceedings for that purpose have been
         instituted or are contemplated by the Commission; the Additional
         Registration Statement (if any) satisfying the requirements of
         subparagraphs (1) and (3) of Rule 462(b) was filed pursuant to Rule
         462(b), including payment of the applicable filing fee in accordance
         with Rule 111(a) or (b) under the Act, prior to the time the Prospectus
         was printed and distributed to any Underwriter; and, subsequent to the
         date of the most recent financial statements in the Prospectus, there
         has been no material adverse change, nor any development or event
         involving a prospective material adverse change, in the condition
         (financial or other), business, properties or results of operations of
         the Company and its subsidiaries taken as a whole except as set forth
         in or contemplated by the Prospectus or as described in such
         certificate.

              (i) The Representatives shall have received a letter, dated such
         Closing Date, of PricewaterhouseCoopers, LLP which meets the
         requirements of subsection (a) of this Section, except that the
         specified date referred to in such subsection will be a date not more
         than three days prior to such Closing Date for the purposes of this
         subsection.

              (j) The Representatives shall have received from all officers and
         directors of the Company and holders of Common Stock, securities
         convertible into Common Stock and options to purchase Common Stock
         (representing an aggregate of at least 95% of the Common Stock, on an
         as-converted, fully-diluted basis) an agreement ("LOCK-UP AGREEMENT")
         dated on or before the date


                                      -18-



         of this Agreement to the effect that, for a period of 180 days after
         the Effective Date, such person will not, except as otherwise provided
         in the Lock-Up Agreement without the prior written consent of Deutsche
         Banc, offer, sell, contract to sell, grant any option to purchase,
         pledge or otherwise dispose of or transfer, directly or indirectly, any
         shares of Securities or securities convertible into or exchangeable or
         exercisable for any shares of Securities.

              If any of the conditions hereinabove provided for in this Section
         6 shall not have been fulfilled when and as required by this Agreement
         to be fulfilled, the obligations of the Underwriters hereunder may be
         terminated by the Representatives by notifying the Company of such
         termination in writing or by telegram at or prior to the First Closing
         Date and each Optional Closing Date.

The Selling Stockholders and the Company will furnish the Representatives with
such conformed copies of such opinions, certificates, letters and documents as
the Representatives reasonably request. Deutsche Banc may in its sole discretion
waive on behalf of the Underwriters compliance with any conditions to the
obligations of the Underwriters hereunder, whether in respect of an optional
Closing Date or otherwise.

         7. INDEMNIFICATION AND CONTRIBUTION. (a) Subject to Section 7(h), the
Company and the Principal Selling Stockholder, jointly and severally, will
indemnify and hold harmless each Underwriter, its partners, directors and
officers and each person, if any who controls such Underwriter within the
meaning of Section 15 of the Act, against any losses, claims, damages or
liabilities, joint or several, to which such Underwriter may become subject,
under the Act or otherwise, insofar as such losses, claims, damages or
liabilities (or actions in respect thereof) arise out of or are based upon (i)
any breach of any representation, warranty, agreement or covenant of the Company
and the Principal Selling Stockholder contained in Section 2(a), (ii) any untrue
statement or alleged untrue statement of any material fact contained in any
Registration Statement, the Prospectus, or any amendment or supplement thereto,
or any related preliminary prospectus or (iii) the omission or alleged omission
to state therein a material fact required to be stated therein or necessary to
make the statements therein in light of the circumstances under which they were
made not misleading, and will reimburse each Underwriter for any legal or other
expenses reasonably incurred by such Underwriter in connection with
investigating or defending any such loss, claim, damage, liability or action as
such expenses are incurred; provided, however, that the Company will be liable
only for the fees of one counsel for all of the Underwriters and will not be
liable in any such case to the extent that any such loss, claim, damage or
liability arises out of or is based upon an untrue statement or alleged untrue
statement in or omission or alleged omission from any of such documents in
reliance upon and in conformity with written information furnished to the
Company by any Underwriter through the Representatives specifically for use
therein, it being understood and agreed that the only such information furnished
by any Underwriter consists of the information described as such in subsection
(c) below; PROVIDED, FURTHER HOWEVER, that this indemnification provision with
respect to any Registration Statement or preliminary prospectus shall not inure
to the benefit of any Underwriter (or any person controlling such Underwriter)
from whom the person asserting any such losses, claims, damages or liabilities
purchased Offered Securities if a copy of the Prospectus (as then amended or
supplemented if the Company shall have furnished any amendments or supplements
thereto) was not sent or given by or on behalf of such Underwriter to such
person, at or prior to the written confirmation of the sale of the Offered
Securities to such person, and if the Prospectus (as so amended or supplemented)
would have cured the defect giving rise to such losses, claims, damages or
liabilities.

         (b) Each Selling Stockholder severally and not jointly will indemnify
and hold harmless each Underwriter, its partners, directors and officers and
each person who controls such Underwriter within the meaning of Section 15 of
the Act, against any losses, claims, damages or liabilities, joint or several,
to which such Underwriter may become subject, under the Act or otherwise,
insofar as such losses, claims, damages or liabilities (or actions in respect
thereof) arise out of or are based upon any breach of any representation,
warranty, agreement or covenant of such Selling Stockholder contained herein,
and will


                                      -19-



reimburse each Underwriter for any legal or other expenses reasonably incurred
by such Underwriter in connection with investigating or defending any such loss,
claim, damage, liability or action as such expenses are incurred; provided,
however, that the Selling Stockholders will be liable only for the fees of one
counsel for all of the Underwriters and will not be liable in any such case to
the extent that any such loss, claim, damage or liability arises out of or is
based upon an untrue statement or alleged untrue statement in or omission or
alleged omission from any of such documents in reliance upon and in conformity
with written information furnished to the Company by an Underwriter through the
Representatives specifically for use therein, it being understood and agreed
that the only such information furnished by any Underwriter consists of the
information described as such in subsection (c) below; PROVIDED, FURTHER
HOWEVER, that this indemnification provision with respect to any Registration
Statement or preliminary prospectus shall not inure to the benefit of any
Underwriter (or any person controlling such Underwriter) from whom the person
asserting any such losses, claims, damages or liabilities purchased Offered
Securities if a copy of the Prospectus (as then amended or supplemented if the
Company shall have furnished any amendments or supplements thereto) was not sent
or given by or on behalf of such Underwriter to such person, at or prior to the
written confirmation of the sale of the Offered Securities to such person, and
if the Prospectus (as so amended or supplemented) would have cured the defect
giving rise to such losses, claims, damages or liabilities.

         (c) Each Underwriter will severally and not jointly indemnify and hold
harmless the Company, its directors and officers and each person, if any, who
controls the Company within the meaning of Section 15 of the Act, and each
Selling Stockholder against any losses, claims, damages or liabilities to which
the Company or such Selling Stockholder may become subject, under the Act or
otherwise, insofar as such losses, claims, damages or liabilities (or actions in
respect thereof) arise out of or are based upon any untrue statement or alleged
untrue statement of any material fact contained in any Registration Statement,
the Prospectus, or any amendment or supplement thereto, or any related
preliminary prospectus, or arise out of or are based upon the omission or the
alleged omission to state therein a material fact required to be stated therein
or necessary to make the statements therein not misleading, in each case to the
extent, but only to the extent, that such untrue statement or alleged untrue
statement or omission or alleged omission was made in reliance upon and in
conformity with written information furnished to the Company by such Underwriter
through the Representatives specifically for use therein, and will reimburse any
legal or other expenses reasonably incurred by the Company and each Selling
Stockholder in connection with investigating or defending any such loss, claim,
damage, liability or action as such expenses are incurred, it being understood
and agreed that the only such information furnished by any Underwriter consists
only of the following information in the Prospectus furnished on behalf of each
Underwriter: (i) the table under the first paragraph under the caption
"Underwriting", (ii) the concession and reallowance figures appearing in the
fifth paragraph under the caption "Underwriting" and (iii) the information
contained in the sixth and thirteenth paragraphs under the caption
"Underwriting".

         (d) Promptly after receipt by an indemnified party under this Section
of notice of the commencement of any action, such indemnified party will, if a
claim in respect thereof is to be made against an indemnifying party under
subsection (a), (b) or (c) above, notify the indemnifying party of the
commencement thereof; but the omission so to notify the indemnifying party will
not relieve it from any liability which it may have to any indemnified party
otherwise than under subsection (a), (b) or (c) above (except to the extent that
such liability was directly caused by such lack of notice). In case any such
action is brought against any indemnified party and it notifies an indemnifying
party of the commencement thereof, the indemnifying party will be entitled to
participate therein and, to the extent that it may wish, jointly with any other
indemnifying party similarly notified, to assume the defense thereof, with
counsel reasonably satisfactory to such indemnified party and after notice from
the indemnifying party to such indemnified party of its election so to assume
the defense thereof, the indemnifying party will not be liable to such
indemnified party under this Section for any legal or other expenses
subsequently incurred by such indemnified party in connection with the defense
thereof other than reasonable costs of investigation; provided, however, that if
the indemnified party or parties reasonably determines that there may be a


                                      -20-



conflict between the positions of the indemnifying party or parties and the
indemnified party or parties in conducting the defense of such action or that
there may be legal defenses available to such indemnified party or parties
different from or in addition to those available to the indemnifying party or
parties, then counsel for the indemnified party or parties shall be entitled to
conduct the defense to the extent reasonably determined by such counsel to be
necessary to protect the interests of the indemnified party or parties, and the
indemnifying party or parties shall bear the legal or other expenses incurred in
connection with the conduct of such defense. No indemnifying party shall,
without the prior written consent of the indemnified party, effect any
settlement of any pending or threatened action in respect of which any
indemnified party is or could have been a party and indemnity could have been
sought hereunder by such indemnified party unless such settlement (i) includes
an unconditional release of such indemnified party from all liability on any
claims that are the subject matter of such action, and (ii) does not include a
statement as to, or an admission of, fault, culpability, or a failure to act by
or on behalf of an indemnified party. The indemnifying party or parties shall
not be responsible and shall have no liability under this Section for any
settlement effected by the indemnified party without the indemnifying parties'
consent.

         (e) If the indemnification provided for in this Section is unavailable
or insufficient to hold harmless an indemnified party under subsection (a), (b)
or (c) above, then each indemnifying party shall contribute to the amount paid
or payable by such indemnified party as a result of the losses, claims, damages
or liabilities referred to in subsection (a), (b) or (c) above (i) in such
proportion as is appropriate to reflect the relative benefits received by the
Company and the Selling Stockholders on the one hand and the Underwriters on the
other from the offering of the Securities or (ii) if the allocation provided by
clause (i) above is not permitted by applicable law, in such proportion as is
appropriate to reflect not only the relative benefits referred to in clause (i)
above but also the relative fault of the Company and the Selling Stockholders on
the one hand and the Underwriters on the other in connection with the statements
or omissions which resulted in such losses, claims, damages or liabilities as
well as any other relevant equitable considerations. The relative benefits
received by the Company and the Selling Stockholders on the one hand and the
Underwriters on the other shall be deemed to be in the same proportion as the
total net proceeds from the offering (before deducting expenses) received by
the Company and the Selling Stockholders bear to the total underwriting
discounts and commissions received by the Underwriters. The relative fault shall
be determined by reference to, among other things, whether the untrue or alleged
untrue statement of a material fact or the omission or alleged omission to state
a material fact relates to information supplied by the Company, the Selling
Stockholders or the Underwriters and the parties' relative intent, knowledge,
access to information and opportunity to correct or prevent such untrue
statement or omission. The amount paid by an indemnified party as a result of
the losses, claims, damages or liabilities referred to in the first sentence of
this subsection (e) shall be deemed to include any legal expenses of one counsel
to the Company and the Selling Stockholders as a group on the one hand and the
Underwriters as a group on the other hand, as the case may be, or other expenses
reasonably incurred by such indemnified party in connection with investigating
or defending any action or claim which is the subject of this subsection (e).
Notwithstanding the provisions of this subsection (e), no Underwriter shall be
required to contribute any amount in excess of the amount by which the total
price at which the Securities underwritten by it and distributed to the public
were offered to the public exceeds the amount of any damages which such
Underwriter has otherwise been required to pay by reason of such untrue or
alleged untrue statement or omission or alleged omission. No person guilty of
fraudulent misrepresentation (within the meaning of Section 11(f) of the Act)
shall be entitled to contribution from any person who was not guilty of such
fraudulent misrepresentation. The Underwriters' obligations in this subsection
(e) to contribute are several in proportion to their respective underwriting
obligations and not joint.

         (f) The obligations of the Company and the Selling Stockholders under
this Section shall be in addition to any liability which the Company and the
Selling Stockholders may otherwise have and shall extend, upon the same terms
and conditions, to each person, if any, who controls any Underwriter within the
meaning of the Act; and the obligations of the Underwriters under this Section
shall be in addition to any liability which the respective Underwriters may
otherwise have and shall extend, upon the same terms


                                      -21-



and conditions, to each director of the Company or the Selling Stockholders, to
each officer of the Company who has signed a Registration Statement and to each
person, if any, who controls the Company or the Selling Stockholders within the
meaning of the Act.

         (g) The liability of each Selling Stockholder (including the Principal
Selling Stockholder) for breach of any representation, warranty, agreement or
covenant of this Agreement and under the indemnification and contribution
provisions under this Section 7 shall not exceed the lesser of (i) that
percentage of the total amount of such losses, claims, damages or liabilities
indemnified against which equals the percentage obtained by dividing the total
number of shares of the Offered Securities sold by such Selling Stockholder
hereunder by the total number of shares of the Offered Securities sold
hereunder, or (ii) the net proceeds received by such Selling Stockholder from
the Underwriters in the offering. Except in the case of claims based on fraud or
seeking equitable relief, the sole and exclusive remedy for breach of any
representation, warranty, agreement or covenant of this Agreement shall be
limited to the indemnification and contribution provisions of this Section 7.
The Company and the Selling Stockholders may agree, as among themselves and
without limiting the rights of the Underwriters under this Agreement, as to the
respective amounts of liability for which they shall each be responsible.

         (h) In the event that any Underwriter is entitled to indemnification or
contribution from the Company or the Principal Selling Stockholder under Section
7(a), such Underwriter shall first obtain recovery, to the extent recoverable,
against the Company for such indemnification or contribution prior to taking any
action against the Principal Selling Stockholder under Section 7(a); PROVIDED,
that such Underwriter shall not be required to delay acting against the
Principal Selling Stockholder if such delay would materially prejudice such
Underwriter's rights under this Agreement.

         8. DEFAULT OF UNDERWRITERS. If any Underwriter or Underwriters default
in their obligations to purchase Offered Securities hereunder on either the
First or any Optional Closing Date and the aggregate number of shares of Offered
Securities that such defaulting Underwriter or Underwriters agreed but failed to
purchase does not exceed 10% of the total number of shares of Offered Securities
that the Underwriters are obligated to purchase on such Closing Date, Deutsche
Banc may make arrangements satisfactory to the Company and the Selling
Stockholders for the purchase of such Offered Securities by other persons,
including any of the Underwriters, but if no such arrangements are made by such
Closing Date, the non-defaulting Underwriters shall be obligated severally, in
proportion to their respective commitments hereunder, to purchase the Offered
Securities that such defaulting Underwriters agreed but failed to purchase on
such Closing Date. If any Underwriter or Underwriters so default and the
aggregate number of shares of Offered Securities with respect to which such
default or defaults occur exceeds 10% of the total number of shares of Offered
Securities that the Underwriters are obligated to purchase on such Closing Date
and arrangements satisfactory to Deutsche Banc, the Company and the Selling
Stockholders for the purchase of such Offered Securities by other persons are
not made within 36 hours after such default, this Agreement will terminate
without liability on the part of any non-defaulting Underwriter, the Company or
the Selling Stockholders, except as provided in Section 9 (provided that if such
default occurs with respect to Optional Securities after the First Closing Date,
this Agreement will not terminate as to the Firm Securities or any Optional
Securities purchased prior to such termination). As used in this Agreement, the
term "Underwriter" includes any person substituted for an Underwriter under this
Section. Nothing herein will relieve a defaulting Underwriter from liability for
its default.

         9. SURVIVAL OF CERTAIN REPRESENTATIONS AND OBLIGATIONS. The respective
indemnities, agreements, representations, warranties and other statements of the
Selling Stockholders, of the Company or its officers and of the several
Underwriters set forth in or made pursuant to this Agreement will remain in full
force and effect, regardless of any investigation, or statement as to the
results thereof, made by or on behalf of any Underwriter, any Selling
Stockholder, the Company or any of their respective representatives, officers or
directors or any controlling person, and will survive delivery of and payment
for the Offered Securities. If this Agreement is terminated pursuant to Section
8 or if for any reason the purchase of the Offered


                                      -22-



Securities by the Underwriters is not consummated, the Company shall remain
responsible for the expenses to be paid or reimbursed by them pursuant to
Section 5 and the respective obligations of the Company, the Selling
Stockholders, and the Underwriters pursuant to Section 7 shall remain in effect,
and if any Offered Securities have been purchased hereunder the representations
and warranties in Section 2 and all obligations under Section 5 shall also
remain in effect. If the purchase of the Offered Securities by the Underwriters
is not consummated for any reason other than solely because of the termination
of this Agreement pursuant to Section 8 or the occurrence of any event specified
in clause (iii), (iv) or (v) of Section 6(c), the Company will reimburse the
Underwriters for all out-of-pocket expenses (including fees and disbursements of
counsel) reasonably incurred by them in connection with the offering of the
Offered Securities.

         10. NOTICES. All communications hereunder will be in writing and, if
sent to the Underwriters, will be mailed, delivered or telegraphed and confirmed
to the Representatives c/o Deutsche Banc Alex. Brown, 101 Federal Street, 15th
Floor, Boston, Massachusetts, 02110, Attention: Investment Banking Department,
or, if sent to the Company, will be mailed, delivered or telegraphed and
confirmed to it at NetScout Systems, Inc., 4 Technology Park Drive, Westford, MA
01886, Attention: President, or, if sent to the Selling Stockholders or any of
them, will be mailed, delivered or telegraphed and confirmed to Anil K. Singhal,
Narendra Popat and Charles W. Tillett at c/o NetScout Systems, Inc., 4
Technology Park Drive, Westford, MA, 01886; provided, however, that any notice
to an Underwriter pursuant to Section 7 will be mailed, delivered or telegraphed
and confirmed to such Underwriter.

         11. SUCCESSORS. This Agreement will inure to the benefit of and be
binding upon the parties hereto and their respective personal representatives
and successors and the officers and directors and controlling persons referred
to in Section 7, and no other person will have any right or obligation
hereunder.

         12. REPRESENTATION. The Representatives will act for the several
Underwriters in connection with the transactions contemplated by this Agreement,
and any action under this Agreement taken by the Representatives jointly or by
Deutsche Banc will be binding upon all the Underwriters. Anil K. Singhal,
Narendra Popat and Charles W. Tillett will act for the Selling Stockholders in
connection with such transactions, and any action under or in respect of this
Agreement taken by Anil K. Singhal, Narendra Popat and Charles W. Tillett will
be binding upon all the Selling Stockholders.

         13. COUNTERPARTS. This Agreement may be executed in any number of
counterparts, each of which shall be deemed to be an original, but all such
counterparts shall together constitute one and the same Agreement.

         14. APPLICABLE LAW. This Agreement shall be governed by, and construed
in accordance with, the laws of the State of New York, without regard to
principles of conflicts of laws.

         The Company hereby submits to the non-exclusive jurisdiction of the
Federal and state courts in the Borough of Manhattan in The City of New York in
any suit or proceeding arising out of or relating to this Agreement or the
transactions contemplated hereby.


                                      -23-



         If the foregoing is in accordance with the Representatives'
understanding of our agreement, kindly sign and return to the Company one of the
counterparts hereof, whereupon it will become a binding agreement among the
Selling Stockholder[s], the Company and the several Underwriters in accordance
with its terms.


                               Very truly yours,


                                        --------------------------------------
                                        [INSERT NAMES OF SELLING STOCKHOLDERS]


                                        --------------------------------------


                                        NETSCOUT SYSTEMS, INC.

                                        By
                                           -----------------------------------
                                          [INSERT TITLE]


The foregoing Underwriting Agreement is hereby
  confirmed and accepted as of the date first above
  written.

         DEUTSCHE BANC ALEX. BROWN
         BEAR, STEARNS & CO. INC.
         DAIN RAUSCHER WESSELS

         Acting on behalf of themselves and as the
              Representatives of the several
              Underwriters.


         By  DEUTSCHE BANC ALEX. BROWN
             -------------------------


         By
             -------------------------
               [INSERT TITLE]


                                      -24-




                                   SCHEDULE A





                                                                 NUMBER OF
                                                                 OPTIONAL
                                                               SECURITIES TO
                 SELLING STOCKHOLDER                              BE SOLD
                 -------------------                           -------------

                                                            










                                                               -------------
    Total ....................................................    600,000
                                                               -------------
                                                               -------------




                                      -25-




                                   SCHEDULE B





                                                                NUMBER OF
                                                             FIRM SECURITIES
         UNDERWRITER                                         TO BE PURCHASED
         -----------                                         ---------------

                                                          

Deutsche Banc Alex. Brown ...............................
Bear, Stearns & Co. Inc. ................................
Dain Raucher Wessels ....................................








                                                             ---------------
    Total ...............................................       4,000,000
                                                             ---------------
                                                             ---------------




                                      -26-