Exhibit 10.8

                                                                [EXECUTION COPY]


                              NETCOM SYSTEMS, INC.
                             SHAREHOLDERS AGREEMENT

          THIS SHAREHOLDERS AGREEMENT (this "AGREEMENT") is made and entered
into as of August 29, 1997, by and among Netcom Systems, Inc., a California
corporation (the "COMPANY"), each of the Persons listed on the SCHEDULE OF
INVESTORS attached hereto (each, an "INVESTOR" and collectively, the
"INVESTORS") and each of the Persons listed on the SCHEDULE OF EXISTING
SHAREHOLDERS attached hereto (each, an "EXISTING SHAREHOLDER" and collectively,
the "EXISTING SHAREHOLDERS"). The Investors and the Existing Shareholders are
collectively referred to herein as the "SHAREHOLDERS" and individually as a
"SHAREHOLDER."  Except as otherwise provided herein, capitalized terms used
herein are defined in paragraph 9 hereof.

          The Investors shall purchase shares of the Company's Class A
Redeemable Preferred Stock and Class B Convertible Preferred Stock pursuant to a
Recapitalization Agreement, dated as of August 29, 1997, by and among the
Investors, the Existing Shareholders and the Company (as the same may be amended
from time to time in accordance with its terms, the "RECAPITALIZATION
AGREEMENT").  The Existing Shareholders are holders on the date hereof of shares
of the Company's Common Stock and/or options to purchase shares of the Company's
Common Stock.

          The Company and the Shareholders desire to enter into this Agreement
for the purposes, among others, of (i) establishing the composition of the
Company's board of directors (the "BOARD"), (ii) assuring continuity in the
management and ownership of the Company and (iii) limiting the manner and terms
by which Shares may be transferred.  The execution and delivery of this
Agreement is a condition to the Closing under the Recapitalization Agreement.

          NOW, THEREFORE, in consideration of the mutual covenants contained
herein and other good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, the parties to this Agreement hereby agree as
follows:

          1.   BOARD OF DIRECTORS.

          (a)  From and after the Closing (as defined in the Recapitalization
Agreement) and until the provisions of this paragraph 1 cease to be effective,
each holder of Shares shall vote all of his, her or its Shares which are voting
shares and any other voting securities of the Company over which such holder has
voting control and shall take all other necessary or desirable actions within
his, her or its control (whether in his, her or its capacity as a shareholder,
director, member of a board committee or officer of the Company or otherwise,
and including attendance at meetings in person or by proxy for purposes of
obtaining a quorum and execution of written consents in lieu of meetings), and
the Company shall take all necessary or desirable actions within its control
(including calling special board and shareholder meetings), so that:

               (i)    the authorized number of directors on the Board shall be
     established at five (5) directors;



               (ii)   the following representatives shall be elected to the
     Board:

                      (A)   one representative designated by the Existing
          Shareholders (the "EXISTING SHAREHOLDER DIRECTOR"), which
          representative shall be designated pursuant to the first sentence of
          paragraph 1A of Section 1 of Subdivision D of Article V of the
          Articles of Incorporation so long as any Convertible Preferred Stock
          remains outstanding or pursuant to the second sentence of paragraph 1A
          of Subdivision D of Article V of the Articles of Incorporation at such
          time as there is no Convertible Preferred Stock outstanding (in either
          case, determined by a vote of the Existing Shareholders owning a
          majority of the Shares held by all of the Existing Shareholders), with
          Marc Hamon serving as the Existing Shareholder Director as of the date
          hereof;

                      (B)   three representatives designated by the Investors
          (the "INVESTOR DIRECTORS"), which representatives shall be designated
          pursuant to paragraph 5A of Section 5 of Subdivision C of Article V of
          the Articles of Incorporation so long as any Convertible Preferred
          Stock remains outstanding or pursuant to the second sentence of
          paragraph 1A of Subdivision D of Article V of the Articles of
          Incorporation at such time as there is no Convertible Preferred Stock
          outstanding (in either case, determined by a vote of the Investors
          owning at least 66 2/3% of the Shares held by all of the Investors),
          one of which (who shall initially be Walter G. Kortschak) to be
          selected by Summit, one of which (who shall initially be Robert H.
          Sheridan III) to be selected by NCC and one of which (who shall
          initially be William B. Bunting) to be selected by Northstar so long
          as such representative is reasonably acceptable to Summit; and

                      (C)   one representative (the "OTHER DIRECTOR") mutually
          designated by the Investors (determined by a vote of the Investors
          owning at least 66 2/3% of the Shares held by all of the Investors)
          and the Existing Shareholders (determined by a vote of the Existing
          Shareholders owning a majority of the Shares held by all of the
          Existing Shareholders), which representative shall be designated
          pursuant to paragraph 5A of Section 5 of Subdivision C of Article V of
          the Articles of Incorporation so long as any Convertible Preferred
          Stock remains outstanding or pursuant to the second sentence of
          paragraph 1A of Subdivision D of Article V of the Articles of
          Incorporation at such time as there is no Convertible Preferred Stock
          outstanding;

               (iii)  for so long as any Investor shall hold any Shares, one of
     the Investor Directors shall serve as Chairman of the Board having the
     powers and duties of such office as set forth in the Company's bylaws, with
     Walter G. Kortschak serving as Chairman of the Board as of the date hereof;

                (iv)  the composition of the board of directors of each of the
     Company's Subsidiaries (a "SUB BOARD") shall be the same as that of the
     Board (subject to the


                                       -2-


     requirements of any jurisdiction that the Sub Board include only residents
     of such jurisdiction or that the Sub Board also include one or more
     residents of such jurisdiction);

                 (v)  (A) a three member Compensation Committee of the Board
     shall be established and shall include the three Investor Directors and (B)
     any other committees established by the Board or a Sub Board shall (to the
     extent possible) be proportionately equivalent to that of the Board;

                (vi)  (A) the removal from the Board or a Sub Board (with or
     without cause) of the Existing Shareholder Director shall be at the written
     request of the Existing Shareholders (determined by a vote of the Existing
     Shareholders owning a majority of the Shares held by all of the Existing
     Shareholders), but only upon such written request and under no other
     circumstances, (B) the removal from the Board or a Sub Board (with or
     without cause) of any Investor Director shall be at the written request of
     the Investor who is entitled to select such Investor Director pursuant to
     subparagraph (ii)(B) above, but only upon such written request and under no
     other circumstances and (C) the removal from the Board or a Sub Board (with
     or without cause) of the Other Director shall be at the mutual written
     request of the Investors (determined by a vote of the Investors owning at
     least 66 2/3% of the Shares held by all of the Investors) and the Existing
     Shareholders (determined by a vote of the Existing Shareholders owning a
     majority of the Shares held by all of the Existing Shareholders), but only
     upon such mutual written request and under no other circumstances; and

               (vii)  (A) in the event that the Existing Shareholder Director
     ceases to serve as a member of the Board or a Sub Board during his or her
     term of office, the resulting vacancy on the Board or a Sub Board shall be
     filled by a representative designated as provided in subparagraph (ii)(A)
     above, (B) in the event that any Investor Director ceases to serve as a
     member of the Board or a Sub Board during his or her term of office, the
     resulting vacancy on the Board or a Sub Board shall be filled by the
     Investor who is entitled to select such Investor Director as provided in
     subparagraph (ii)(B) above, and (C) in the event that the Other Director
     ceases to serve as a member of the Board or a Sub Board during his or her
     term of office, the resulting vacancy on the Board or a Sub Board shall be
     filled by a representative designated as provided in subparagraph (ii)(C)
     above.

          (b)  The Company shall pay the reasonable out-of-pocket expenses
incurred by each director in connection with attending the meetings of the Board
or a Sub Board and any committees thereof.  So long as any Investor Director,
Other Director or Existing Shareholder Director serves on the Board or a Sub
Board, the Company's Articles of Incorporation and bylaws shall provide for
indemnification and exculpation of directors to the fullest extent permitted
under applicable law.

          (c)  If any party fails to designate a representative to fill a
directorship pursuant to the terms of this paragraph 1, the individual
previously holding such directorship shall be elected to such position, or if
such individual fails or declines to serve, the election of an individual to
such directorship shall be accomplished in accordance with the Company's
Articles of Incorporation and


                                       -3-


bylaws and applicable law; PROVIDED THAT the Shareholders shall vote to remove
such individual if the party or parties which failed to designate such
directorship so direct.

          (d)  The right of each of Summit, NCC and Northstar to select one of
the Investor Directors under this paragraph 1 shall terminate at such time as
such Person (together with its Affiliates) shall hold less than 25% of the
Shares held by such Person immediately following the Closing, and at such time
the remaining Investor or Investors holding more than 25% of the Shares held by
such Persons immediately following the Closing shall have the right to designate
a representative(s) to fill the vacant Investor Director or Investor Directors'
positions (determined by a vote of such remaining Investors owning at least
66 2/3% of the Shares held by all such remaining Investors).

          (e)  The provisions of this paragraph 1 shall survive the Company's
initial Public Offering (unless terminated in connection therewith by a vote of
the Investors owning at least 66 2/3% of the Shares held by all of the
Investors) and shall remain in full force and effect thereafter until terminated
by a vote of the Investors owning at least 66 2/3% of the Shares held by all of
the Investors.

          2.   REPRESENTATIONS AND WARRANTIES.  Each Shareholder represents and
warrants that (i) this Agreement has been duly authorized, executed and
delivered by such Shareholder and constitutes the valid and binding obligation
of such Shareholder, enforceable in accordance with its terms, and (ii) such
Shareholder has not granted and is not a party to any proxy, voting trust or
other agreement which is inconsistent with, conflicts with or violates any
provision of this Agreement.  No holder of Shares shall grant any proxy or
become party to any voting trust or other agreement which is inconsistent with,
conflicts with or violates any provision of this Agreement.

          3.   RESTRICTIONS ON TRANSFER OF SHARES.

          (a)  GENERAL.  No holder of Shares shall sell, transfer, assign,
pledge or otherwise dispose of (whether with or without consideration and
whether voluntarily or involuntarily or by operation of law) any interest in any
Shares (a "TRANSFER"), except pursuant to a Public Sale or an Approved Sale (an
"EXEMPT TRANSFER") or the provisions of this paragraph 3.  Prior to making any
Transfer other than an Exempt Transfer, each Existing Shareholder transferring
any Shares (a "TRANSFERRING SHAREHOLDER") shall deliver a written notice (a
"SALE NOTICE") to the Company and the Shareholders other than the Transferring
Shareholder (the "OTHER SHAREHOLDERS") in order to allow the Company and the
Investors to exercise the rights granted pursuant to paragraphs 3(b) and 3(c)
below and the Existing Shareholders to exercise the rights granted pursuant to
paragraph 3(c) below.  Prior to making any transfer other than an Exempt
Transfer, each Investor transferring any shares of Common Stock (a "TRANSFERRING
SHAREHOLDER") shall deliver a written notice (a "SALE NOTICE") to the Other
Shareholders in order to allow the Other Shareholders to exercise the rights
granted pursuant to paragraph 3(c) below.  The Sale Notice shall disclose in
reasonable detail the identity of the prospective transferee(s), the number of
Shares to be transferred and the terms and conditions of the proposed Transfer.
In no event shall any Transfer of Shares pursuant to this paragraph 3 be made by
any Existing Shareholder for any consideration other than cash payable upon
consummation of such Transfer or in installments over time.  No Shareholder
shall consummate any Transfer until


                                       -4-


30 days after the Sale Notice has been given to the Company and the Other
Shareholders (the "ELECTION PERIOD"), unless the parties to the Transfer have
been finally determined pursuant to this paragraph 3 prior to the expiration of
such 30-day period.  The date of the first to occur of such events is referred
to herein as the "AUTHORIZATION DATE."

          (b)  FIRST REFUSAL RIGHTS APPLICABLE TO EXISTING SHAREHOLDERS.  The
Company may elect to purchase all or any portion of an Existing Shareholder's
Shares to be transferred upon the same terms and conditions as those set forth
in the Sale Notice by delivering a written notice of such election to such
Existing Shareholder and the Investors within 20 days after the Sale Notice has
been delivered to the Company.  If the Company has not elected to purchase all
of such Existing Shareholder's Shares to be transferred, the Investors may elect
to purchase the remaining Shares to be transferred upon the same terms and
conditions as those set forth in the Sale Notice by delivering written notice of
such election to such Existing Shareholder within 25 days after the Sale Notice
has been given to the Investors.  If more than one of the Investors elects to
purchase such Shares, the Shares to be sold shall be allocated among the
Investors pro rata according to the number of Shares owned by each such
Investor.  If the Company and/or the Investors have not elected to purchase all
of such Existing Shareholder's Shares specified in the Sale Notice, such
Existing Shareholder may Transfer the Shares specified in the Sale Notice,
subject to the provisions of paragraph 3(c) below, at a price and on terms no
more favorable to the transferee(s) thereof than specified in the Sale Notice
during the 30-day period immediately following the Authorization Date.  Any such
Existing Shareholder's Shares not transferred within such 30-day period shall be
subject to the provisions of this paragraph 3 upon subsequent Transfer.  If the
Company or any of the Investors have elected to purchase any Shares hereunder,
the Transfer of such shares shall be consummated as soon as practical after the
delivery of the election notice(s) to the Transferring Shareholder, but in any
event within 15 days after the expiration of the Election Period.  The Company
and/or the Investors may assign their rights under this paragraph 3(b) to one or
more designees.

          (c)  PARTICIPATION RIGHTS.  If the Company and/or the Investors have
not elected to purchase all of the Shares to be transferred by an Existing
Shareholder pursuant to paragraph 3(b) above, or in the event of a Transfer of
shares of Common Stock by an Investor, each Other Shareholder may elect to
participate in the contemplated Transfer by delivering written notice to the
Transferring Shareholder and the Company within 30 days after receipt by such
Other Shareholder of the Sale Notice.  If any Other Shareholder has elected to
participate in such Transfer, the Transferring Shareholder and the electing
Other Shareholder(s) shall be entitled to sell in the contemplated Transfer, at
the same price and on the same terms, a number of shares of Common Stock equal
to the product of (i) the quotient determined by dividing the percentage of
Shares owned by such Person by the aggregate percentage of Shares owned by the
Transferring Shareholder and all electing Other Shareholder(s) and (ii) the
number of shares of Common Stock to be sold in the contemplated sale.

     FOR EXAMPLE, if the Sale Notice contemplated a sale of 100 shares of Common
     Stock, and if the Transferring Shareholder was at such time the owner of
     30% of all Shares and if one Other Shareholder elected to participate and
     such Other Shareholder owned 20% of all Shares, the Transferring
     Shareholder would be entitled to sell 60 shares of Common Stock
     (30% DIVIDED BY 50% x 100 shares of Common Stock) and the


                                       -5-


     electing Other Shareholder would be entitled to sell 40 shares of Common
     Stock (20% DIVIDED BY 50% x 100 shares of Common Stock).

The Transferring Shareholder shall use his, her or its best efforts to obtain
the agreement of the prospective transferee(s) to the participation of the Other
Shareholders in the contemplated Transfer and shall not Transfer any shares of
Common Stock to the prospective transferee(s) if such transferee(s) refuses to
allow the participation of the Other Shareholders.  Each Shareholder
transferring shares of Common Stock pursuant to this paragraph 3(c) shall pay
its pro rata share (based on the number of shares of Common Stock to be sold) of
the expenses incurred by the Shareholders in connection with such Transfer and
shall be obligated to join on a pro rata basis (based on the number of shares of
Common Stock to be sold) in any indemnification or other obligations that the
Transferring Shareholder agrees to provide in connection with such Transfer
(other than any such obligations that relate specifically to a particular
Shareholder such as indemnification with respect to representations and
warranties given by a Shareholder regarding such Shareholder's title to and
ownership of shares of Common Stock).

          (d)  CERTAIN PERMITTED TRANSFERS.  The restrictions contained in this
paragraph 3 shall not apply with respect to any Transfer of Shares by any
Shareholder (i) in the case of any Shareholder which is an individual, pursuant
to applicable laws of descent and distribution or among such Shareholder's
Family Group or (ii) in the case of an Investor, among its Affiliates or among
any of the other Investors or their Affiliates (collectively referred to herein
as "PERMITTED TRANSFEREES"); PROVIDED THAT such restrictions shall continue to
be applicable to the Shares after any such Transfer and the transferees of such
Shares shall agree in writing to be bound by the provisions of this Agreement as
a condition precedent to any such Transfer.  An individual Shareholder's "FAMILY
GROUP" means such Shareholder's spouse and descendants (whether natural or
adopted) or any trust, family partnership or other entity established solely for
the benefit of such Shareholder and/or such Shareholder's spouse and/or
descendants.  An Investor's "AFFILIATE" means any other Person directly or
indirectly controlling, controlled by or under common control with such Investor
and any partner or member of an Investor which is a partnership or limited
liability company.  Notwithstanding the foregoing, no party hereto shall avoid
the provisions of this Agreement by making one or more transfers to one or more
Permitted Transferees and then disposing of all or any portion of such party's
interest in any such Permitted Transferee.

          (e)  TERMINATION OF RESTRICTIONS.  The restrictions set forth in this
paragraph 3 shall continue with respect to each Share following any Transfer
thereof (other than an Exempt Transfer or a Transfer to the Company or an
Investor or its designee pursuant to paragraph 3(b) above or a Transfer pursuant
to paragraph 3(c) above); PROVIDED THAT all such restrictions shall terminate
upon the consummation of a Public Offering.

          4.   HOLDBACK AGREEMENT.  No Shareholder shall effect any public sale
or distribution (including sales pursuant to Rule 144 or any similar provision
then in force) under the Securities Act of any Shares or of any other capital
stock or equity securities of the Company, or any securities convertible into or
exchangeable or exercisable for such stock or securities, during the seven days
prior to, and the 180-day period beginning on, the effective date of the
Company's initial public offering of its Common Stock under the Securities Act
or during the seven days prior to, and


                                       -6-


the 90-day period beginning on the effective date of the next registered public
offering of the Company's Common Stock (except as part of such underwritten
registration), unless the underwriters managing the registration otherwise
agree.  The restrictions on transfer set forth in this paragraph 4 shall
continue with respect to each Share until the date on which such Share has been
transferred in a Public Sale.

          5.   SALE OF THE COMPANY.

          (a)  If the Board and the holders of at least 66 2/3% of the Shares
held by the Investors approve a sale of all or substantially all of the
Company's assets determined on a consolidated basis or a sale or exchange of all
or substantially all of the Company's outstanding capital stock (whether by
merger, sale, recapitalization, consolidation, reorganization, combination or
otherwise) to any Person or Persons (an "APPROVED SALE"), each holder of Shares
shall vote for, consent to and raise no objections against such Approved Sale
and shall waive any dissenters' rights, appraisal rights or similar rights in
connection therewith.  If the Approved Sale is structured as a sale of stock,
each holder of Shares shall agree to sell all of his, her or its Shares and
rights to acquire Shares on the terms and conditions approved by the Board and
the holders of at least 66 2/3% of the Shares held by the Investors.  Each
holder of Shares shall take all necessary and desirable actions in his, her or
its capacity as a shareholder in connection with the consummation of the
Approved Sale as requested by the Company (including attendance at meetings in
person or by proxy for purposes of obtaining a quorum and execution of written
consents in lieu of meetings).

          (b)  The obligations of the holders of Shares with respect to an
Approved Sale are subject to the satisfaction of the following conditions:
(i) upon the consummation of the Approved Sale, all of the holders of Common
Stock shall receive the same form and amount of consideration per share of
Common Stock, or if any holders of Common Stock are given an option as to the
form and amount of consideration to be received, all holders shall be given the
same option; and (ii) in connection with the Approved Sale all holders of Shares
representing then currently exercisable rights to acquire shares of Common Stock
(including all holders of Convertible Preferred Stock) shall only be permitted
to either (A) exercise such rights (including conversion rights in the case of
the holders of Convertible Preferred Stock) prior to the consummation of the
Approved Sale and participate in such sale as holders of Common Stock or
(B) upon the consummation of the Approved Sale, receive in exchange for such
rights consideration equal to the amount determined by multiplying (1) the same
amount of consideration per share of Common Stock received by the holders of
Common Stock in connection with the Approved Sale less the exercise price (if
any) per share of Common Stock of such rights to acquire Common Stock by (2) the
number of shares of Common Stock represented by such then currently exercisable
rights and shall not be entitled to exercise their rights under paragraph 4A of
Subdivision C of Article V of the Company's Articles of Incorporation in
connection with any such Approved Sale and receive the aggregate consideration
provided for thereunder in preference to the holders of Common Stock.

          (c)  Each holder of Shares shall bear his, her or its pro rata share
(based upon the number of Shares held by such holder) of the costs of any
Approved Sale to the extent such costs are incurred for the benefit of all
holders of Shares and are not otherwise paid by the Company or the acquiring
party and shall be obligated to join on a pro rata basis (based on the number of
Shares


                                       -7-


held by such holder) in any indemnification or other obligations that the
Investors holding at least [66 2/3%] of the Shares held by all of the Investors
agree to provide in connection with such Approved Sale (other than any such
obligations that relate specifically to a holder of Shares such as
indemnification with respect to representations and warranties given by a holder
regarding such holder's title to and ownership of Shares).

          (d)  In order to secure each Existing Shareholder's obligation to vote
his, her or its Shares and other voting securities of the Company in accordance
with the provisions of this paragraph 5, each Existing Shareholder hereby
appoints the Investor Representative as his, her or its true and lawful proxy
and attorney-in-fact, with full power of substitution, to vote all of his, her
or its Shares and other voting securities of the Company for the approval and
consummation of an Approved Sale and all such other matters as expressly
provided for in this paragraph 5.  The Investor Representative may exercise the
irrevocable proxy granted to it hereunder at any time any Existing Stockholder
fails to comply with the provisions of this paragraph 5.  The proxies and powers
granted by each Existing Shareholder pursuant to this paragraph 5(d) are coupled
with an interest and are given to secure the performance of each Existing
Shareholder's obligations and duties under this paragraph 5.  Such proxies and
powers shall be irrevocable for so long as such Existing Shareholder holds any
Shares and shall survive the death, incompetency, disability, bankruptcy or
dissolution of such Existing Shareholder and the subsequent holders of his, her
or its Shares.

          (e)  The provisions of this paragraph 5 shall terminate upon the
consummation of a Public Offering.

          6.   FIRST REFUSAL RIGHTS APPLICABLE TO ISSUANCES OF COMMON STOCK.

          (a)  Except for issuances of Common Stock (a) to the Company's and any
of its Subsidiaries' employees, consultants, lenders or lessors as approved by
the Board or the Compensation Committee (including pursuant to options or other
rights to acquire Common Stock approved by the Board or the Compensation
Committee), (b) in connection with the acquisition of another company or
business or (c) pursuant to a Public Offering, if the Company authorizes the
issuance or sale of any shares of Common Stock or any securities (including debt
securities) containing options or rights to acquire any shares of Common Stock
(other than as a dividend on the outstanding shares of Common Stock) or any
securities exchangeable for or convertible into Common Stock or such securities
exchangeable for or convertible into Common Stock, the Company shall first offer
to sell to each Investor holding any Shares and to each of the Existing
Shareholders holding any Shares, a portion of such shares or securities equal to
the quotient determined by dividing (1) the number of shares of Common Stock
held by such Person (including the number of shares of Common Stock issuable
upon conversion of the Convertible Preferred Stock) by (2) the total number of
shares of Common Stock then outstanding (including the number of shares of
Common Stock issuable upon conversion of the Convertible Preferred Stock).  Each
Investor and each of the Existing Shareholders shall be entitled to purchase
such shares or securities at the most favorable price and on the most favorable
terms as such shares or securities are to be offered or sold to any other
Persons; PROVIDED THAT if all Persons entitled to purchase or receive such stock
or securities are required to also purchase other securities of the Company,
each Investor and each of the Existing Shareholders exercising their rights
pursuant to this paragraph shall also be required to


                                       -8-


purchase the same strip of securities (on the same terms and conditions) that
such other Persons are required to purchase.  The purchase price for all shares
and securities offered to the Investors and the Existing Shareholders shall be
payable in cash or, to the extent otherwise consistent with the terms offered to
any other Persons, installments over time.

          (b)  In order to exercise its purchase rights hereunder, an Investor
or an Existing Shareholder must within 20 days after receipt of written notice
from the Company describing in reasonable detail the shares or securities being
offered, the purchase price therefor, the payment terms and such Investor's or
such Existing Shareholder's percentage allotment, deliver a written notice to
the Company describing its election hereunder.  If all of the shares and
securities offered to the Investors and the Existing Shareholders are not fully
subscribed by the Investors and the Existing Shareholders, the remaining stock
and securities shall be reoffered by the Company to any of the Investors or the
Existing Shareholders purchasing such Person's full allotment upon the terms set
forth in this paragraph, except that such holders must exercise their purchase
rights within five days after receipt of such reoffer.

          (c)  Upon the expiration of the offering periods described above, the
Company shall be entitled to sell such shares or securities which the Investors
and the Existing Shareholders have not elected to purchase during the 60 days
following such expiration on terms and conditions no more favorable to the
purchasers thereof than those offered to the Investors and the Existing
Shareholders.  Any shares or securities offered or sold by the Company after
such 60-day period must be reoffered to the Investors and the Existing
Shareholders pursuant to the terms of this paragraph 6.

          (d)  The rights of the Investors and the Existing Shareholders under
this paragraph 6 shall terminate upon the consummation of a Public Offering.

          7.   LEGEND.  Each certificate evidencing Shares and each certificate
issued in exchange for or upon the Transfer of any Shares (if such shares remain
Shares after such Transfer) shall be stamped or otherwise imprinted with a
legend in substantially the following form:

     "The securities represented by this certificate are subject to a
     Shareholders Agreement dated as of August 29, 1997, among the issuer of
     such securities (the "COMPANY") and certain of the Company's shareholders,
     as amended and modified from time to time.  A copy of such Shareholders
     Agreement shall be furnished without charge by the Company to the holder
     hereof upon written request."

The Company shall imprint such legend on certificates evidencing Shares
outstanding as of the date hereof.  The legend set forth above shall be removed
from the certificates evidencing any shares which cease to be Shares in
accordance with paragraph 9 hereof.

          8.   TRANSFERS; FUTURE SALES.  Prior to any holder of Shares
Transferring any Shares (other than pursuant to an Exempt Transfer) to any
Person, such holder shall cause the prospective transferee to be bound by this
Agreement and to execute and deliver to the Company and the other Shareholders a
counterpart of this Agreement.  Transferees of Shares held by Investors shall be


                                       -9-


deemed to be Investors hereunder.  Transferees of Shares held by Existing
Shareholders (other than the Investors or their designees, who shall be deemed
to be Investors hereunder) shall be deemed to be Existing Shareholders hereunder
(except that no such transferees from the Existing Shareholders shall have the
right to participate in any sale of shares of Common Stock by the Investors
pursuant to paragraph 3(c) above).  The provisions of this paragraph 8 shall
terminate upon the consummation of a Public Offering.

          9.   DEFINITIONS.

          "ARTICLES OF INCORPORATION" means the Company's articles of
incorporation as in effect from time to time.

          "CLOSING" has the meaning given to such term in the Recapitalization
Agreement.

          "COMMON STOCK" means the Company's common stock, no par value per
share.

          "CONVERTIBLE PREFERRED STOCK" means the Company's Class B Convertible
Preferred Stock, no par value per share.

          "EVENT OF NONCOMPLIANCE" has the meaning given to such term in the
Articles of Incorporation.

          "FINANCING" has the meaning given to such term in the Recapitalization
Agreement.

          "INVESTOR REPRESENTATIVE" means Summit.

          "NCC" means NationsBanc Capital Corp., a Texas corporation.

          "NORTHSTAR" means Northstar Investors, LLC, a Delaware limited
liability company.

          "PERSON" means an individual, a partnership, a corporation, a limited
liability company, an association, a joint stock company, a trust, a joint
venture, an unincorporated organization and a governmental entity or any
department, agency or political subdivision thereof.

          "PUBLIC OFFERING" means any offering by the Company of its Common
Stock to the public pursuant to an effective registration statement under the
Securities Act or any comparable statement under any similar federal statute
then in force.

          "PUBLIC SALE" means any sale of Shares to the public pursuant to an
offering registered under the Securities Act or to the public through a broker,
dealer or market maker pursuant to the provisions of Rule 144 adopted under the
Securities Act (or any similar provision then in force).

          "SBA" has the meaning given to such term in the Recapitalization
Agreement.


                                      -10-


          "SBIC PURCHASER" has the meaning given to such term in the
Recapitalization Agreement.

          "SBIC REGULATIONS" has the meaning given to such term in the
Recapitalization Agreement.

          "SECURITIES ACT" means the Securities Act of 1933, as amended from
time to time.

          "SHARES" means (i) any Common Stock purchased or otherwise acquired or
held by any Shareholder, (ii) any Common Stock issued or issuable directly or
indirectly upon the conversion, exercise or exchange of any securities purchased
or otherwise acquired by any Shareholder which are convertible into or
exercisable or exchangeable for Common Stock (including the Convertible
Preferred Stock and any stock options granted by the Company) and (iii) any
capital stock or other equity securities issued or issuable directly or
indirectly with respect to the securities referred to in clauses (i) or (ii)
above by way of a stock dividend or stock split or in connection with a
combination of shares, recapitalization, merger, consolidation or other
reorganization.  As to any particular securities constituting Shares hereunder,
such securities shall cease to be Shares when they have been (x) effectively
registered under the Securities Act and disposed of in accordance with the
registration statement covering them or (y) sold to the public through a broker,
dealer or market maker pursuant to Rule 144 (or any similar provision then in
force) under the Securities Act.

          "SUBSIDIARY" means, with respect to any Person, any corporation,
limited liability company, partnership, association or other business entity of
which (i) if a corporation, a majority of the total voting power of shares of
stock entitled (without regard to the occurrence of any contingency) to vote in
the election of directors, managers or trustees thereof is at the time owned or
controlled, directly or indirectly, by that Person or one or more Subsidiaries
of that Person or a combination thereof, or (ii) if a limited liability company,
partnership, association or other business entity, a majority of the limited
liability company, partnership or other similar ownership interest thereof is at
the time owned or controlled, directly or indirectly, by that Person or one or
more Subsidiaries of that Person or a combination thereof.  For purposes hereof,
a Person or Persons shall be deemed to have a majority ownership interest in a
limited liability company, partnership, association or other business entity if
such Person or Persons shall be allocated a majority of the limited liability
company, partnership, association or other business entity gains or losses or
shall be or control the managing director, managing member or general partner of
such limited liability company, partnership, association or other business
entity.

          "SUMMIT" means Summit Ventures IV, L.P., a Delaware limited
partnership.

          10.  FINANCIAL STATEMENTS AND OTHER INFORMATION.  So long as any
Investor or Existing Shareholder holds any Shares, the Company shall deliver to
such Investor or Existing Shareholder, as the case may be:

          (a)  Not later than 30 days prior to the last day of each fiscal year,
capital and operating expense budgets, projections of sources and applications
of funds and profit and loss projections (prepared in accordance with generally
accepted accounting principles, consistently


                                      -11-


applied) for the Company (and each of the Subsidiaries with which it prepares
consolidated financial statements) on a consolidated basis for each month of the
next succeeding fiscal year, all itemized in reasonable detail and prepared by
Company.  Any material revisions made in such budgets or projections shall be
furnished promptly to each Investor and Existing Shareholder;

          (b)  As soon as available and in any event within 90 days after the
end of each fiscal year, audited financial statements of the Company (and the
Subsidiaries with which it prepares consolidated financial statements) on a
consolidated and consolidating basis, including a balance sheet as at the end of
such fiscal year, statements of income and retained earnings and a related
statement of cash flows for such fiscal year and the figures for the preceding
year, together with all notes thereto, prepared in reasonable detail and in
accordance with generally accepted accounting principles consistently applied
and accompanied by the report thereof of an independent accounting firm of
recognized national standing as may be selected by the Company, (i) stating,
among other things, that in the course of their audit, nothing has come to their
attention suggesting that a condition or event has occurred that constitutes an
Event of Noncompliance or a default or event of default under the Senior Loan
Documents (as such term is defined in the Recapitalization Agreement) and (ii)
containing no exceptions or qualifications (except for qualifications regarding
specific contingent liabilities) (or if there was such a condition or event,
specifying the same);

          (c)  As soon as available and in any event within 45 days after the
end of each fiscal quarter, unaudited financial statements of the Company (and
the Subsidiaries with which it prepares consolidated financial statements) on a
consolidated and consolidating basis, including a balance sheet as at the end of
the preceding fiscal quarter, statements of income and retained earnings and a
related statement of cash flows for such quarter (prepared in accordance with
generally accepted accounting principles, consistently applied), such figures
for the corresponding fiscal quarter of the preceding fiscal year and
comparisons to the budget for such fiscal quarter. Such financial statements
shall be certified by the chief financial officer of the Company to be (to his
knowledge) complete and accurate, to fairly present the financial condition of
the Company and its Subsidiaries and to be prepared in accordance with generally
accepted accounting principles, consistently applied;

          (d)  As soon as available in any event within 30 days after the end of
each month, monthly financial reports of the Company (and the Subsidiaries with
which it prepares consolidated financial statements) on a consolidated basis,
including a balance sheet as at the end of the preceding calendar month and
statements of income and retained earnings and a related statement of cash flows
for such month (prepared in accordance with generally accepted accounting
principles, consistently applied), such figures for the corresponding month of
the preceding fiscal year and comparisons to the budget for such month.  Such
financial statements shall be certified by the chief financial officer of the
Company to be (to his knowledge) complete and accurate, to fairly present the
financial condition of the Company and its Subsidiaries and to be prepared in
accordance with generally accepted accounting principles, consistently applied;

          (e)  As soon as reasonably possible and in any event within 30 days
after the end of each month, a statement signed by the chief financial officer
of the Company, setting forth in


                                      -12-


reasonable detail a consolidated report setting forth operational data
reasonably requested by each Investor;

          (f)  Promptly, and in no event more than ten days after receipt
thereof, copies of all audit reports, so-called "management letters" and other
communications and reports submitted to the Company or any of its Subsidiaries
by independent certified public accountants in connection with each interim or
special audit of the Company or any of its Subsidiaries made by such
accountants; and

          (g)  Promptly, but in any event within ten days after the Company has
knowledge thereof, (i) written notice of any actual or anticipated material
adverse change in the operations or financial condition of the Company or any of
its Subsidiaries, and (ii) copies of any report of any Person with respect to
the condition of the Company or any Subsidiary citing any material adverse
condition at the Company or such Subsidiary.

          11.  SBIC REGULATORY PROVISIONS.

          (a)  NUMBER OF STOCKHOLDERS.  As long as the SBIC Purchaser holds any
Class A Redeemable Preferred Stock of the Company or any Shares, the Company
shall notify the SBIC Purchaser (i) at least 15 days prior to taking any action
after which the number of record holders of the Company's voting stock would be
increased from fewer than 50 to 50 or more, and (ii) of any other action or
occurrence after which the number of record holders of the Company's voting
stock was increased (or would increase) from fewer than 50 to 50 or more, as
soon as practicable after the Company becomes aware that such other action or
occurrence has occurred or is proposed to occur.

          (b)  USE OF PROCEEDS.  At the same time the Company delivers its
annual audited financials hereunder and at such other times as the SBIC
Purchaser reasonable requests, the Company shall deliver to the SBIC Purchaser a
written statement certified by the Company's president or chief financial
officer describing in reasonable detail the use of the proceeds of the Financing
by the Company and its Subsidiaries.  In addition to any other rights granted
hereunder, the Company shall grant the SBIC Purchaser and the SBA access to the
Company's books and records for the purpose of verifying the use of such
proceeds and verifying the certifications made by the Company in SBA Forms 480
and 652 delivered pursuant to the Recapitalization Agreement and for the purpose
of determining whether the principal business activity of the Company and its
Subsidiaries continues to constitute an eligible business activity (within the
meaning of the SBIC Regulations).

          (c)  ECONOMIC IMPACT INFORMATION.  Promptly after the end of each
fiscal year, the Company shall deliver to the SBIC Purchaser a written
assessment of the economic impact of the SBIC Purchaser's investment in the
Company, specifying the full-time equivalent jobs created or retained in
connection with the investment, the impact of such SBIC Purchaser's Financing on
the revenues and profits of the Company and its Subsidiaries and on taxes paid
by the Company and its employees.


                                      -13-


          (d)  PROHIBITED ACTIVITIES.  Neither the Company nor any of its
Subsidiaries shall engage in any activities for which an SBIC is prohibited from
providing funds by the SBIC Regulations (including 13 CFR Section 107.720).

          12.  INSPECTION RIGHTS.  The Company shall permit any representatives
designated by any Investor and any Existing Shareholder (so long as such
Investor or Existing Shareholder holds any Shares), upon reasonable notice and
during normal business hours and at such other times as any such holder may
reasonably request (and, in the Company's discretion, subject to the execution
of a satisfactory confidentiality agreement), to visit and inspect any of the
properties of the Company and its Subsidiaries and examine the corporate and
financial records of the Company and its Subsidiaries.

          13.  TRANSFERS IN VIOLATION OF AGREEMENT.  Any Transfer or attempted
Transfer of any Shares in violation of any provision of this Agreement shall be
void, and the Company shall not record such Transfer on its books or treat any
purported transferee of such Shares as the owner of such Shares for any purpose.

          14.  AMENDMENT AND WAIVER.  Except as otherwise provided herein, no
modification, amendment or waiver of any provision of this Agreement shall be
effective against the Company or the Shareholders unless such modification,
amendment or waiver is approved in writing by the Company, the Investors holding
at least 66 2/3% of the Shares then held by the Investors and the Existing
Shareholders holding a majority of the Shares then held by the Existing
Shareholders.  The failure of any party to enforce any of the provisions of this
Agreement shall in no way be construed as a waiver of such provisions and shall
not affect the right of such party thereafter to enforce each and every
provision of this Agreement in accordance with its terms.

          15.  SEVERABILITY.  Whenever possible, each provision of this
Agreement shall be interpreted in such manner as to be effective and valid under
applicable law, but if any provision of this Agreement is held to be invalid,
illegal or unenforceable in any respect under any applicable law or rule in any
jurisdiction, such invalidity, illegality or unenforceability shall not affect
the validity, legality or enforceability of any other provision of this
Agreement in such jurisdiction or affect the validity, legality or
enforceability of any provision in any other jurisdiction, but this Agreement
shall be reformed, construed and enforced in such jurisdiction as if such
invalid, illegal or unenforceable provision had never been contained herein.

          16.  ENTIRE AGREEMENT.  Except as otherwise expressly set forth
herein, this Agreement embodies the complete agreement and understanding among
the parties hereto with respect to the subject matter hereof and supersedes and
preempts any prior understandings, agreements or representations by or among the
parties, written or oral, which may have related to the subject matter hereof in
any way.

          17.  SUCCESSORS AND ASSIGNS.  Except as otherwise expressly provided
herein, this Agreement shall bind and inure to the benefit of and be enforceable
by the Company and its successors and assigns and the Shareholders and any
subsequent holders of Shares and the respective successors and assigns of each
of them, so long as they hold Shares; PROVIDED THAT the rights of the


                                      -14-


Existing Shareholders under paragraphs 1, 3(c), 6 and 12 above may not be
assigned without the prior written approval of the holders of at least 66 2/3%
of the Shares held by the Investors.

          18.  COUNTERPARTS.  This Agreement may be executed in multiple
counterparts (including by means of telecopied signature pages), each of which
shall be an original and all of which taken together shall constitute one and
the same agreement.

          19.  REMEDIES.  The parties hereto shall be entitled to enforce their
rights under this Agreement specifically, to recover damages by reason of any
breach of any provision of this Agreement and to exercise all other rights
existing in their favor.  The parties hereto agree and acknowledge that money
damages would not be an adequate remedy for any breach of the provisions of this
Agreement and that the Company and any Shareholder may in its sole discretion
apply to any court of law or equity of competent jurisdiction for specific
performance and/or injunctive relief (without posting a bond or other security)
in order to enforce or prevent any violation of the provisions of this
Agreement.

          20.  NOTICES.  Any notice provided for in this Agreement shall be in
writing and shall be either personally delivered, or mailed first class mail
(postage prepaid) or sent by reputable overnight courier service (charges
prepaid) to the Company at the address set forth below and to any other
recipient at the address indicated on the schedules hereto and to any subsequent
holder of Shares subject to this Agreement at such address as indicated by the
Company's records, or at such address or to the attention of such other Person
as the recipient party has specified by prior written notice to the sending
party.  Notices shall be deemed to have been given hereunder when delivered
personally, five days after deposit in the U.S. mail and one day after deposit
with a reputable overnight courier service (charges prepaid).  The Company's
address is:

                    Netcom Systems, Inc.
                    20550 Nordhoff Street
                    Chatsworth, California 91311
                    Attention: Chief Executive Officer

                    WITH A COPY TO:
                    (which shall not constitute notice to the Company)
                    Wilson, Sonsini, Goodrich & Rosati
                    650 Page Mill Road
                    Palo Alto, California 94304-1050
                    Attn:  Steven E. Bochner, Esq.

          21.  GOVERNING LAW.  All issues and questions concerning the
construction, validity, interpretation and enforcement of this Agreement and the
exhibits and schedules hereto shall be governed by, and construed in accordance
with, the laws of the State of California without giving effect to any choice of
law or conflict of law rules or provisions (whether of the State of California
or any other jurisdiction) that would cause the application of the laws of any
jurisdiction other than the State of California.


                                      -15-


          22.  BUSINESS DAYS.  If any time period for giving notice or taking
action hereunder expires on a day which is a Saturday, Sunday or legal holiday
in the state in which the Company's chief executive office is then located, the
time period shall automatically be extended to the business day immediately
following such Saturday, Sunday or legal holiday.

          23.  DESCRIPTIVE HEADINGS, ETC.  The descriptive headings of this
Agreement are inserted for convenience only and do not constitute a part of this
Agreement.  The use of the term "including" herein shall mean "including without
limitation."

          24.  NO STRICT CONSTRUCTION.  The parties hereto have participated
jointly in the negotiation and drafting of this Agreement.  In the event an
ambiguity or question or intent or interpretation arises, this Agreement shall
be construed as it was drafted jointly by the parties hereto, and no presumption
or burden of proof shall arise favoring or disfavoring any party hereto by
virtue of the authorship of any of the provisions of this Agreement.

                          *      *      *      *     *


                                      -16-


          IN WITNESS WHEREOF, the parties hereto have executed this Agreement on
the day and year first above written.

                         NETCOM SYSTEMS, INC.


                         By:
                            ---------------------------------------------------
                         Its:
                            ---------------------------------------------------


                         SUMMIT VENTURES IV, L.P.

                         By:  Summit Partners IV, L.P.,
                              its General Partner

                         By:  Stamps, Woodsum& Co. IV,
                              its General Partner

                         By:
                            ---------------------------------------------------
                               General Partner


                         SUMMIT INVESTORS III, L.P.


                         By:
                            ---------------------------------------------------
                               Authorized Signatory


                         NATIONSBANC CAPITAL CORP.


                         By:
                            ---------------------------------------------------
                              Todd A. Binkowski, its Authorized Signatory


                         NORTHSTAR INVESTORS, LLC


                         By:
                            ---------------------------------------------------

                         Its:
                            ---------------------------------------------------


                   [Signature Page to Shareholders Agreement]



                         SPITFIRE CAPITAL PARTNERS, L.P.
                         By:  MS Spitfire LLC, its General Partner

                         By:
                            ---------------------------------------------------
                               William B. Bunting, its Authorized Signatory


                         PETER MOONEY, AS NOMINEE FOR THE BROADVIEW PARTNERS
                         GROUP

                         By:
                            ---------------------------------------------------
                         Its:
                             --------------------------------------------------


                         BAIN SECURITIES, INC.

                         By:
                            ---------------------------------------------------
                                Leonard C. Banos, its Vice President


                         WS INVESTMENT COMPANY 97B


                         By:
                            ---------------------------------------------------
                         Its:

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



                         WSGR PROFIT SHARING TRUST FBO
                         STEVEN E. BOCHNER

                         By:
                            ---------------------------------------------------

                         Its:
                             --------------------------------------------------

                         ------------------------------------------------------
                         Steven E. Bochner

                         ------------------------------------------------------
                         Nevan C. Elam

                         ------------------------------------------------------
                         Todd Cleary

                   [Signature Page to Shareholders Agreement]



                         ------------------------------------------------------
                         Marc Hamon


                         ------------------------------------------------------
                         Henri Hamon


                         ------------------------------------------------------
                         James Jordan


                         ------------------------------------------------------
                         Warren B. Phelps III


                         ------------------------------------------------------
                         Jing Zhang


                         ------------------------------------------------------
                         Stephane Johnson


                         ------------------------------------------------------
                         Richard Bass









                   [Signature Page to Shareholders Agreement]




                      Consent and Community Property Waiver


          The undersigned hereby acknowledges that the undersigned has read this
Agreement and understands its contents.  The undersigned is aware that this
Agreement provides for the purchase of shares of Common Stock from the
undersigned's spouse.  The undersigned hereby acknowledges and agrees that the
interest of the undersigned's spouse in such Common Stock is subject to this
Agreement and any interest the undersigned may have in such Common Stock shall
be irrevocably bound by this Agreement and further that the undersigned's
community property interest, if any, shall be similarly bound by this Agreement.
The undersigned has sought legal advice with respect to such waiver and has
determined after carefully reviewing this Agreement that the undersigned will
waive such community property right.




                                   --------------------------------------------
                                   By:  [Spouse's Name]

- ------------------------------
Witness



                              SCHEDULE OF INVESTORS

Name and Address
- ----------------

Summit Ventures IV, L.P.                   WS Investment Company 97B
499 Hamilton Avenue                        c/o Wilson Sonsini Goodrich & Rosati
Palo Alto, California  94301               650 Page Mill Road
Attn:  Mr. Walter G. Kortschak             Palo Alto, California 94304
                                           Attn:  Steven E Bochner, Esq.
Summit Investors III, L.P.
499 Hamilton Avenue                        WSGR Profit Sharing Trust FBO
Palo Alto, California  94301               Steven E. Bochner
Attn:  Mr. Walter G. Kortschak             c/o Wilson Sonsini Goodrich & Rosati
                                           650 Page Mill Road
NationsBanc Capital Corp.                  Palo Alto, California 94304
NationsBank Corporate Center               Attn:  Steven E Bochner, Esq.
10th Floor
100 North Tryon                            Steven E. Bochner
Charlotte, North Carolina  28255           c/o Wilson Sonsini Goodrich & Rosati
Attn:  Mr. Robert H. Sheridan III          650 Page Mill Road
                                           Palo Alto, California 94304
Northstar Investors, LLC
c/o Montgomery Securities                  Nevan C. Elam
600 Montgomery Street                      c/o Wilson Sonsini Goodrich & Rosati
San Francisco, California  94111           650 Page Mill Road
Attn:  Mr. Derek Lemke                     Palo Alto, California 94304

Spitfire Capital Partners, L.P.            Todd Cleary
c/o Montgomery Securities                  c/o Wilson Sonsini Goodrich & Rosati
600 Montgomery Street                      650 Page Mill Road
San Francisco, California  94111           Palo Alto, California 94304
Attn:  Mr. William B. Bunting

Peter Mooney as nominee for
the Broadview Partners Group
c/o Broadview Associates
950 Tower Lane
18th Floor
Foster City, California  94404
Attn:  Mr. Stephen S. Smith

Bain Securities, Inc.
c/o Bain & Company, Inc.
Two Copley Place
Boston, Massachusetts  02116
Attn:  Mr. Leonard C. Banos



With a Copy to:
- --------------
(which shall not constitute notice to the Investors)

Kirkland & Ellis
200 East Randolph Drive
Chicago, Illinois  60601
Attn:  Ted H. Zook, Esq.

Fennebresque, Clark, Swindell & Hay
100 North Tryon Street, Suite 2900
Charlotte, North Carolina  28202-4011
Attn:  John S. Chinuntdet, Esq.



                        SCHEDULE OF EXISTING SHAREHOLDERS

Name And Address
- ----------------

Marc  Hamon
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Henri Hamon
Netcom Systems Europe
4, rue de Galilee
Immeuble Le Bellevue
ZAC du Moulin a vent 78280
Guyancourt, France

James Jordan
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Warren B. Phelps III
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Jing Zhang
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Stephane Johnson
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Richard Bass
Point of View, Inc.
410 Boylston Street
5th Floor
Boston, Massachusetts  02116

With a Copy to:
- --------------
(which shall not constitute notice to the Existing Shareholders)

Wilson Sonsini Goodrich & Rosati
650 Page Mill Road
Palo Alto, California  94304
Attn:  Steven E. Bochner, Esq.



                              NETCOM SYSTEMS, INC.
                    AMENDMENT NO. 1 TO SHAREHOLDERS AGREEMENT

          THIS AMENDMENT NO. 1 TO SHAREHOLDERS AGREEMENT (this "AMENDMENT") is
made and entered into as of September 25, 1997, by and among Netcom Systems,
Inc., a California corporation (the "COMPANY"), each of the Persons listed on
the SCHEDULE OF INVESTORS attached hereto (each, an "INVESTOR" and collectively,
the "INVESTORS"), each of the Persons listed on the SCHEDULE OF EXISTING
SHAREHOLDERS attached hereto (each, an "EXISTING SHAREHOLDER" and collectively,
the "EXISTING SHAREHOLDERS") and Richard Moley ("MOLEY").

          WHEREAS, the Company, the Investors and the Existing Shareholders are
parties to that certain Shareholders Agreement dated as of August 29, 1997 (the
"AGREEMENT").

          WHEREAS, Moley is purchasing shares of the Company's Class A
Redeemable Preferred Stock and Class B Convertible Preferred Stock pursuant to a
Preferred Stock Purchase Agreement, dated as of the date hereof, by and between
the Company and Moley.

          WHEREAS, the Company, the Existing Shareholders and the Investors
desire to enter into this Amendment for the purposes of making Moley a party to
the Agreement.

          NOW, THEREFORE, in consideration of the mutual covenants contained
herein and other good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, the parties to this Amendment hereby agree as
follows:

          1.   INVESTOR.  For all purposes of the Agreement (as amended by this
Amendment), the term "INVESTOR" shall include Moley.

          2.   NOTICES.  All notices and other communications to Moley provided
for or permitted under the Agreement (as amended by this Amendment) shall be
made at the address of Moley set forth in the Company's books and records.

          3.   GOVERNING LAW.  All issues and questions concerning the
construction, validity, interpretation and enforcement of this Agreement and the
exhibits and schedules hereto shall be governed by, and construed in accordance
with, the laws of the State of California without giving effect to any choice of
law or conflict of law rules or provisions (whether of the State of California
or any other jurisdiction) that would cause the application of the laws of any
jurisdiction other than the State of California.

          4.   DESCRIPTIVE HEADINGS, ETC.  The descriptive headings of this
Agreement are inserted for convenience only and do not constitute a part of this
Agreement.  The use of the term "including" herein shall mean "including without
limitation."

          5.   FULL FORCE AND EFFECT.  Except as amended hereby, the Agreement
shall remain in full force and effect.

                          *      *      *      *     *


                                       -1-


          IN WITNESS WHEREOF, the parties hereto have executed this Amendment
No. 1 to Shareholders Agreement on the day and year first above written.

                         NETCOM SYSTEMS, INC.


                         By:
                            ---------------------------------------------------

                         Its:
                             --------------------------------------------------


                         SUMMIT VENTURES IV, L.P.

                         By:  Summit Partners IV, L.P.,
                              its General Partner

                         By:  Stamps, Woodsum& Co. IV,
                              its General Partner


                         By:
                            ---------------------------------------------------
                               General Partner


                         SUMMIT INVESTORS III, L.P.


                         By:
                            ---------------------------------------------------
                               Authorized Signatory


                         NATIONSBANC CAPITAL CORP.


                         By:
                            ---------------------------------------------------
                              Todd A. Binkowski, its Authorized Signatory


                         NORTHSTAR INVESTORS, LLC


                         By:
                            ---------------------------------------------------

                         Its:
                             --------------------------------------------------


                   [Amendment No. 1 to Shareholders Agreement]



                         SPITFIRE CAPITAL PARTNERS, L.P.
                         By:  MS Spitfire LLC, its General Partner

                         By:
                            ---------------------------------------------------
                               William B. Bunting, its Authorized Signatory


                         PETER MOONEY, AS NOMINEE FOR THE BROADVIEW PARTNERS
                         GROUP

                         By:
                            ---------------------------------------------------
                         Its:
                             --------------------------------------------------


                         BAIN SECURITIES, INC.

                         By:
                            ---------------------------------------------------
                                Leonard C. Banos, its Vice President


                         WS INVESTMENT COMPANY 97B

                         By:
                            ---------------------------------------------------
                         Its:
                             --------------------------------------------------


                         WSGR PROFIT SHARING TRUST FBO
                         STEVEN E. BOCHNER

                         By:
                            ---------------------------------------------------

                         Its:
                             --------------------------------------------------


                         ------------------------------------------------------
                         Steven E. Bochner

                         ------------------------------------------------------
                         Nevan C. Elam

                         ------------------------------------------------------
                         Todd Cleary

                   [Amendment No. 1 to Shareholders Agreement]




                         ------------------------------------------------------
                         Marc Hamon


                         ------------------------------------------------------
                         Henri Hamon


                         ------------------------------------------------------
                         James Jordan


                         ------------------------------------------------------
                         Warren B. Phelps III


                         ------------------------------------------------------
                         Jing Zhang


                         ------------------------------------------------------
                         Stephane Johnson


                         ------------------------------------------------------
                         Richard Bass


                         ------------------------------------------------------
                         Richard Moley





                   [Amendment No. 1 to Shareholders Agreement



                              SCHEDULE OF INVESTORS

Name and Address
- ----------------

Summit Ventures IV, L.P.                   WS Investment Company 97B
499 Hamilton Avenue                        c/o Wilson Sonsini Goodrich & Rosati
Palo Alto, California  94301               650 Page Mill Road
Attn:  Mr. Walter G. Kortschak             Palo Alto, California 94304
                                           Attn:  Steven E Bochner, Esq.
Summit Investors III, L.P.
499 Hamilton Avenue                        WSGR Profit Sharing Trust FBO
Palo Alto, California  94301               Steven E. Bochner
Attn:  Mr. Walter G. Kortschak             c/o Wilson Sonsini Goodrich & Rosati
                                           650 Page Mill Road
NationsBanc Capital Corp.                  Palo Alto, California 94304
NationsBank Corporate Center               Attn:  Steven E Bochner, Esq.
10th Floor
100 North Tryon                            Steven E. Bochner
Charlotte, North Carolina  28255           c/o Wilson Sonsini Goodrich & Rosati
Attn:  Mr. Robert H. Sheridan III          650 Page Mill Road
                                           Palo Alto, California 94304
Northstar Investors, LLC
c/o Montgomery Securities                  Nevan C. Elam
600 Montgomery Street                      c/o Wilson Sonsini Goodrich & Rosati
San Francisco, California  94111           650 Page Mill Road
Attn:  Mr. Derek Lemke                     Palo Alto, California 94304

Spitfire Capital Partners, L.P.            Todd Cleary
c/o Montgomery Securities                  c/o Wilson Sonsini Goodrich & Rosati
600 Montgomery Street                      650 Page Mill Road
San Francisco, California  94111           Palo Alto, California 94304
Attn:  Mr. William B. Bunting

Peter Mooney as nominee for
the Broadview Partners Group
c/o Broadview Associates
950 Tower Lane
18th Floor
Foster City, California  94404
Attn:  Mr. Stephen S. Smith

Bain Securities, Inc.
c/o Bain & Company, Inc.
Two Copley Place
Boston, Massachusetts  02116
Attn:  Mr. Leonard C. Banos



                        SCHEDULE OF EXISTING SHAREHOLDERS

Name and Address
- ----------------

Marc  Hamon
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Henri Hamon
Netcom Systems Europe
4, rue de Galilee
Immeuble Le Bellevue
ZAC du Moulin a vent 78280
Guyancourt, France

James Jordan
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Warren B. Phelps III
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Jing Zhang
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Stephane Johnson
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Richard Bass
Point of View, Inc.
410 Boylston Street
5th Floor
Boston, Massachusetts  02116



                              NETCOM SYSTEMS, INC.
                    AMENDMENT NO. 2 TO SHAREHOLDERS AGREEMENT

          THIS AMENDMENT NO. 2 TO SHAREHOLDERS AGREEMENT (this "AMENDMENT") is
made and entered into as of January 8, 1998, by and among Netcom Systems, Inc.,
a California corporation (the "COMPANY"), each of the Persons listed on the
SCHEDULE OF INVESTORS attached hereto (each, an "INVESTOR" and collectively, the
"INVESTORS"), each of the Persons listed on the SCHEDULE OF EXISTING
SHAREHOLDERS attached hereto (each, an "EXISTING SHAREHOLDER" and collectively,
the "EXISTING SHAREHOLDERS").

          WHEREAS, the Company, the Investors and the Existing Shareholders are
parties to that certain Shareholders Agreement dated as of August 29, 1997, as
amended (the "AGREEMENT").

          WHEREAS, The parties hereto wish to amend certain provisions of the
Agreement relating to the voting of shares of capital stock of the Company as
set forth herein.

          NOW, THEREFORE, in consideration of the mutual covenants contained
herein and other good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, the parties to this Amendment hereby agree as
follows:


          1.   RESTATEMENT.  Section 1 of the Agreement is amended and restated
in its entirety to read as follows:

"         1.   BOARD OF DIRECTORS.

          (a)  From and after the Closing (as defined in the Recapitalization
Agreement) and until the provisions of this paragraph 1 cease to be effective,
each holder of Shares shall vote all of his, her or its Shares which are voting
shares and any other voting securities of the Company over which such holder has
voting control and shall take all other necessary or desirable actions within
his, her or its control (whether in his, her or its capacity as a shareholder,
director, member of a board committee or officer of the Company or otherwise,
and including attendance at meetings in person or by proxy for purposes of
obtaining a quorum and execution of written consents in lieu of meetings), and
the Company shall take all necessary or desirable actions within its control
(including calling special board and shareholder meetings), so that:

               (i)    the authorized number of directors on the Board shall be
     established at six (6) directors;

               (ii)   the following representatives shall be elected to the
     Board:


                                       -1-


                      (A)     one representative designated by the Existing
          Shareholders (the "EXISTING SHAREHOLDER DIRECTOR"), which
          representative shall be designated pursuant to the first sentence of
          paragraph 1A of Section 1 of Subdivision D of Article V of the
          Articles of Incorporation so long as any Convertible Preferred Stock
          remains outstanding or pursuant to the second sentence of paragraph 1A
          of Subdivision D of Article V of the Articles of Incorporation at such
          time as there is no Convertible Preferred Stock outstanding (in either
          case, determined by a vote of the Existing Shareholders owning a
          majority of the Shares held by all of the Existing Shareholders), with
          Marc Hamon serving as the Existing Shareholder Director as of the date
          hereof;

                      (B)     three representatives designated by the Investors
          (the "INVESTOR DIRECTORS"), which representatives shall be designated
          pursuant to paragraph 5A of Section 5 of Subdivision C of Article V of
          the Articles of Incorporation so long as any Convertible Preferred
          Stock remains outstanding or pursuant to the second sentence of
          paragraph 1A of Subdivision D of Article V of the Articles of
          Incorporation at such time as there is no Convertible Preferred Stock
          outstanding (in either case, determined by a vote of the Investors
          owning at least 66 2/3% of the Shares held by all of the Investors),
          one of which (who shall initially be Walter G. Kortschak) to be
          selected by Summit, one of which (who shall initially be Robert H.
          Sheridan III) to be selected by NCC and one of which (who shall
          initially be William B. Bunting) to be selected by Northstar so long
          as such representative is reasonably acceptable to Summit; and

                      (C)     two representatives (the "OTHER DIRECTORS")
          mutually designated by the Investors (determined by a vote of the
          Investors owning at least 66 2/3% of the Shares held by all of the
          Investors) and the Existing Shareholders (determined by a vote of the
          Existing Shareholders owning a majority of the Shares held by all of
          the Existing Shareholders), which representatives shall be designated
          pursuant to paragraph 5A of Section 5 of Subdivision C of Article V of
          the Articles of Incorporation so long as any Convertible Preferred
          Stock remains outstanding or pursuant to the second sentence of
          paragraph 1A of Subdivision D of Article V of the Articles of
          Incorporation at such time as there is no Convertible Preferred Stock
          outstanding;

               (iii)  for so long as any Investor shall hold any Shares, one of
     the Investor Directors shall serve as Chairman of the Board having the
     powers and duties of such office as set forth in the Company's bylaws, with
     Walter G. Kortschak serving as Chairman of the Board as of the date hereof;

               (iv)   the composition of the board of directors of each of the
     Company's Subsidiaries (a "SUB BOARD") shall be the same as that of the
     Board (subject to the requirements of any jurisdiction that the Sub Board
     include only


                                       -2-


     residents of such jurisdiction or that the Sub Board also include one or
     more residents of such jurisdiction);

               (v)    (A) a three member Compensation Committee of the Board
     shall be established and shall include the three Investor Directors and (B)
     any other committees established by the Board or a Sub Board shall (to the
     extent possible) be proportionately equivalent to that of the Board;

               (vi)   (A) the removal from the Board or a Sub Board (with or
     without cause) of the Existing Shareholder Director shall be at the written
     request of the Existing Shareholders (determined by a vote of the Existing
     Shareholders owning a majority of the Shares held by all of the Existing
     Shareholders), but only upon such written request and under no other
     circumstances, (B) the removal from the Board or a Sub Board (with or
     without cause) of any Investor Director shall be at the written request of
     the Investor who is entitled to select such Investor Director pursuant to
     subparagraph (ii)(B) above, but only upon such written request and under no
     other circumstances and (C) the removal from the Board or a Sub Board (with
     or without cause) of any Other Director shall be at the mutual written
     request of the Investors (determined by a vote of the Investors owning at
     least 66 2/3% of the Shares held by all of the Investors) and the Existing
     Shareholders (determined by a vote of the Existing Shareholders owning a
     majority of the Shares held by all of the Existing Shareholders), but only
     upon such mutual written request and under no other circumstances; and

               (vii)  (A) in the event that the Existing Shareholder Director
     ceases to serve as a member of the Board or a Sub Board during his or her
     term of office, the resulting vacancy on the Board or a Sub Board shall be
     filled by a representative designated as provided in subparagraph (ii)(A)
     above, (B) in the event that any Investor Director ceases to serve as a
     member of the Board or a Sub Board during his or her term of office, the
     resulting vacancy on the Board or a Sub Board shall be filled by the
     Investor who is entitled to select such Investor Director as provided in
     subparagraph (ii)(B) above, and (C) in the event that any Other Director
     ceases to serve as a member of the Board or a Sub Board during his or her
     term of office, the resulting vacancy on the Board or a Sub Board shall be
     filled by a representative designated as provided in subparagraph (ii)(C)
     above.

          (b)  The Company shall pay the reasonable out-of-pocket expenses
incurred by each director in connection with attending the meetings of the Board
or a Sub Board and any committees thereof.  So long as any Investor Director,
Other Director or Existing Shareholder Director serves on the Board or a Sub
Board, the Company's Articles of Incorporation and bylaws shall provide for
indemnification and exculpation of directors to the fullest extent permitted
under applicable law.

          (c)  If any party fails to designate a representative to fill a
directorship pursuant to the terms of this paragraph 1, the individual
previously holding such directorship shall be elected to such position, or if
such individual fails or declines to serve, the election


                                       -3-


of an individual to such directorship shall be accomplished in accordance with
the Company's Articles of Incorporation and bylaws and applicable law; PROVIDED
THAT the Shareholders shall vote to remove such individual if the party or
parties which failed to designate such directorship so direct.

          (d)  The right of each of Summit, NCC and Northstar to select one of
the Investor Directors under this paragraph 1 shall terminate at such time as
such Person (together with its Affiliates) shall hold less than 25% of the
Shares held by such Person immediately following the Closing, and at such time
the remaining Investor or Investors holding more than 25% of the Shares held by
such Persons immediately following the Closing shall have the right to designate
a representative(s) to fill the vacant Investor Director or Investor Directors'
positions (determined by a vote of such remaining Investors owning at least 66
2/3% of the Shares held by all such remaining Investors).

          (e)  The provisions of this paragraph 1 shall survive the Company's
initial Public Offering (unless terminated in connection therewith by a vote of
the Investors owning at least 66 2/3% of the Shares held by all of the
Investors) and shall remain in full force and effect thereafter until terminated
by a vote of the Investors owning at least 66 2/3% of the Shares held by all of
the Investors."

          2.   GOVERNING LAW.  All issues and questions concerning the
construction, validity, interpretation and enforcement of this Agreement and the
exhibits and schedules hereto shall be governed by, and construed in accordance
with, the laws of the State of California without giving effect to any choice of
law or conflict of law rules or provisions (whether of the State of California
or any other jurisdiction) that would cause the application of the laws of any
jurisdiction other than the State of California.

          3.   DESCRIPTIVE HEADINGS, ETC.  The descriptive headings of this
Agreement are inserted for convenience only and do not constitute a part of this
Agreement.  The use of the term "including" herein shall mean "including without
limitation."

          4.   FULL FORCE AND EFFECT.  Except as amended hereby, the Agreement
shall remain in full force and effect.

                          *      *      *      *     *


                                       -4-


          IN WITNESS WHEREOF, the parties hereto have executed this Amendment
No. 1 to Shareholders Agreement on the day and year first above written.

                         NETCOM SYSTEMS, INC.


                         By:
                            ---------------------------------------------------
                         Its:
                             --------------------------------------------------


                         SUMMIT VENTURES IV, L.P.

                         By:  Summit Partners IV, L.P.,
                              its General Partner

                         By:  Stamps, Woodsum& Co. IV,
                              its General Partner


                         By:
                            ---------------------------------------------------
                               General Partner


                         SUMMIT INVESTORS III, L.P.


                         By:
                            ---------------------------------------------------
                               Authorized Signatory


                         NATIONSBANC CAPITAL CORP.


                         By:
                            ---------------------------------------------------
                              Todd A. Binkowski, its Authorized Signatory


                         SPITFIRE CAPITAL PARTNERS, L.P.
                         By:  MS Spitfire LLC, its General Partner

                         By:
                            ---------------------------------------------------
                            William B. Bunting, its Authorized Signatory

                   [Amendment No. 2 to Shareholders Agreement]


                                       -5-


                         PETER MOONEY, AS NOMINEE FOR THE BROADVIEW PARTNERS
                         GROUP

                              By:
                                 -----------------------------------------------

                              Its:
                                  ----------------------------------------------


                              BAIN SECURITIES, INC.

                              By:
                                 -----------------------------------------------
                                     Leonard C. Banos, its Vice President


                              WS INVESTMENT COMPANY 97B


                              By:
                                 -----------------------------------------------

                              Its:
                                  ----------------------------------------------


                              WSGR PROFIT SHARING TRUST FBO
                              STEVEN E. BOCHNER

                              By:
                                 -----------------------------------------------

                              Its:
                                  ----------------------------------------------


                              ADVENT ATLANTIC AND PACIFIC III


                              By:
                                 -----------------------------------------------

                              Its:
                                  ----------------------------------------------


                              CHASE VENTURE CAPITAL ASSOC., L.P.


                              By:
                                 -----------------------------------------------

                              Its:
                                  ----------------------------------------------



                   [Amendment No. 2 to Shareholders Agreement]


                                       -6-


                              TA ADVENT VIII


                              By:
                                 ----------------------------------------------

                              Its:
                                  ----------------------------------------------


                              TA VENTURE INVESTORS


                              By:
                                 ----------------------------------------------

                              Its:
                                  ----------------------------------------------


                              -------------------------------------------------
                              Steven E. Bochner


                              -------------------------------------------------
                              Nevan C. Elam


                              -------------------------------------------------
                              Todd Cleary

                              -------------------------------------------------
                              Marc Hamon


                              -------------------------------------------------
                              Henri Hamon


                              -------------------------------------------------
                              James Jordan


                              -------------------------------------------------
                              Warren B. Phelps III



                   [Amendment No. 2 to Shareholders Agreement]


                                       -7-


                              -------------------------------------------------
                              Jing Zhang


                              -------------------------------------------------
                              Stephane Johnson


                              -------------------------------------------------
                              Richard Bass


                              -------------------------------------------------
                              Richard Moley


                              -------------------------------------------------
                              David A. Baylor


                              -------------------------------------------------
                              Richard J. Cadenasso


                              -------------------------------------------------
                              Allen Chozen


                              -------------------------------------------------
                              Lewis W. Coleman


                              -------------------------------------------------
                              David V. Crowder


                              -------------------------------------------------
                              Frank M. Dunlevy


                              -------------------------------------------------
                              Clark L. Gerhardt, Jr.

                   [Amendment No. 2 to Shareholders Agreement]


                                       -8-


                              -------------------------------------------------
                              Seth J. Gersch


                              -------------------------------------------------
                              Ansel M. Hall


                              -------------------------------------------------
                              John D. Hershey


                              -------------------------------------------------
                              Wilson T. Hileman, Jr.


                              -------------------------------------------------
                              Brett A. Hodess


                              -------------------------------------------------
                              Benjamin Howe


                              -------------------------------------------------
                              Murray C. Huneke


                              -------------------------------------------------
                              David M. Jacquin


                              -------------------------------------------------
                              Craig R. Johnson


                              -------------------------------------------------
                              Scott C. Kovalik


                              -------------------------------------------------
                              David S. Lehmann



                   [Amendment No. 2 to Shareholders Agreement]


                                       -9-


                              -------------------------------------------------
                              Mark L. Lehmann


                              -------------------------------------------------
                              Derek Lemke-von Ammon


                              -------------------------------------------------
                              Jack G. Levin


                              -------------------------------------------------
                              Robert D. Long


                              -------------------------------------------------
                              Karl L. Matthies


                              -------------------------------------------------
                              J. Sanford Miller


                              -------------------------------------------------
                              Bernard M. Notas


                              -------------------------------------------------
                              Harry K. Plant


                              -------------------------------------------------
                              Bruce G. Potter


                              -------------------------------------------------
                              David B. Readerman


                              -------------------------------------------------
                              Rand L. Rosenberg



                   [Amendment No. 2 to Shareholders Agreement]


                                      -10-


                              -------------------------------------------------
                              Joseph M. Schell


                              -------------------------------------------------
                              Rex Sherry


                              -------------------------------------------------
                              Peter B. Stoneberg


                              -------------------------------------------------
                              Thomas A. Thornhill, III


                              -------------------------------------------------
                              John P. Tinker


                              -------------------------------------------------
                              Otto V. Tschudi


                              -------------------------------------------------
                              Thomas W. Weisel


                              -------------------------------------------------
                              Michael L. Yagemann



                   [Amendment No. 2 to Shareholders Agreement]


                                      -11-


                              SCHEDULE OF INVESTORS

Name and Address
- ----------------

Summit Ventures IV, L.P.                   Summit Investors III, L.P.
499 Hamilton Avenue                        499 Hamilton Avenue
Palo Alto, California  94301               Palo Alto, California  94301
Attn:  Mr. Walter G. Kortschak             Attn:  Mr. Walter G. Kortschak

NationsBanc Capital Corp.                  TA Venture Investors
NationsBank Corporate Center               c/o TA Associates, Inc.
10th Floor                                 High Street Tower, Suite 2500
100 North Tryon                            125 High Street
Charlotte, North Carolina  28255           Boston, MA 02110
Attn:  Mr. Robert H. Sheridan III          Attn:  Mr. Thomas Alber

Spitfire Capital Partners, L.P.            Peter Mooney as nominee for
c/o Montgomery Securities                  the Broadview Partners Group
600 Montgomery Street                      c/o Broadview Associates
San Francisco, California  94111           950 Tower Lane
Attn:  Mr. William B. Bunting              18th Floor
                                           Foster City, California  94404
                                           Attn:  Mr. Stephen S. Smith

Bain Securities, Inc.                      WS Investment Company 97B
c/o Bain & Company, Inc.                   c/o Wilson Sonsini Goodrich & Rosati
Two Copley Place                           650 Page Mill Road
Boston, Massachusetts  02116               Palo Alto, California 94304
Attn:  Mr. Leonard C. Banos                Attn:  Steven E Bochner, Esq.

WSGR Profit Sharing Trust FBO              Steven E. Bochner
Steven E. Bochner                          c/o Wilson Sonsini Goodrich & Rosati
c/o Wilson Sonsini Goodrich & Rosati       650 Page Mill Road
650 Page Mill Road                         Palo Alto, California 94304
Palo Alto, California 94304
Attn:  Steven E Bochner, Esq.

Nevan C. Elam                              Todd Cleary
c/o Wilson Sonsini Goodrich & Rosati       c/o Wilson Sonsini Goodrich & Rosati
650 Page Mill Road                         650 Page Mill Road
Palo Alto, California 94304                Palo Alto, California 94304

Richard Moley                              Chase Venture Capital Assoc., L.P.
19910 Robin Way                            380 Madison Avenue
Saratoga, CA 95070                         New York, NY 10017
                                           Attn:  Jeff Walker


                                      -12-


TA Advent VIII                             Advent Atlantic and Pacific III
c/o TA Associates, Inc.                    c/o TA Associates, Inc.
High Street Tower, Suite 2500              High Street Tower, Suite 2500
125 High Street                            125 High Street
Boston, MA 02110                           Boston, MA 02110
Attn:  Mr. Thomas Alber                    Attn:  Mr. Thomas Alber

David A. Baylor                            Richard J. Cadenasso
c/o Montgomery Securities                  c/o Montgomery Securities
600 Montgomery Street                      600 Montgomery Street
San Francisco, California  94111           San Francisco, California  94111

Allen Chozen                               Lewis W. Coleman
c/o Montgomery Securities                  c/o Montgomery Securities
600 Montgomery Street                      600 Montgomery Street
San Francisco, California  94111           San Francisco, California  94111

TA Advent VIII                             Advent Atlantic and Pacific III 
c/o TA Associates, Inc.                    c/o TA Associates, Inc.         
High Street Tower, Suite 2500              High Street Tower, Suite 2500   
125 High Street                            125 High Street                 
Boston, MA 02110                           Boston, MA 02110                
Attn:  Mr. Thomas Alber                    Attn:  Mr. Thomas Alber         

David A. Baylor                            Richard J. Cadenasso             
c/o Montgomery Securities                  c/o Montgomery Securities        
600 Montgomery Street                      600 Montgomery Street            
San Francisco, California  94111           San Francisco, California  94111 

Allen Chozen                               Lewis W. Coleman                 
c/o Montgomery Securities                  c/o Montgomery Securities        
600 Montgomery Street                      600 Montgomery Street            
San Francisco, California  94111           San Francisco, California  94111 

David V. Crowder                           Frank M. Dunlevy                 
c/o Montgomery Securities                  c/o Montgomery Securities        
600 Montgomery Street                      600 Montgomery Street            
San Francisco, California  94111           San Francisco, California  94111 

Clark L. Gerhardt, Jr.                     Seth J. Gersch                   
c/o Montgomery Securities                  c/o Montgomery Securities        
600 Montgomery Street                      600 Montgomery Street            
San Francisco, California  94111           San Francisco, California  94111 

Ansel M. Hall                              John D. Hershey                  
c/o Montgomery Securities                  c/o Montgomery Securities        
600 Montgomery Street                      600 Montgomery Street            
San Francisco, California  94111           San Francisco, California  94111 

Wilson T. Hileman, Jr.                     Brett A. Hodess                 
c/o Montgomery Securities                  c/o Montgomery Securities       
600 Montgomery Street                      600 Montgomery Street           
San Francisco, California  94111           San Francisco, California  94111

Benjamin Howe                              Murray C. Huneke                
c/o Montgomery Securities                  c/o Montgomery Securities       
600 Montgomery Street                      600 Montgomery Street           
San Francisco, California  94111           San Francisco, California  94111

David M. Jacquin                           Craig R. Johnson                
c/o Montgomery Securities                  c/o Montgomery Securities       
600 Montgomery Street                      600 Montgomery Street           
San Francisco, California  94111           San Francisco, California  94111


                                       -13-


Scott C. Kovalik                           David S. Lehmann                
c/o Montgomery Securities                  c/o Montgomery Securities       
600 Montgomery Street                      600 Montgomery Street           
San Francisco, California  94111           San Francisco, California  94111

Mark L. Lehmann                            Derek Lemke-von Ammon           
c/o Montgomery Securities                  c/o Montgomery Securities       
600 Montgomery Street                      600 Montgomery Street           
San Francisco, California  94111           San Francisco, California  94111

Jack G. Levin                              Robert D. Long                  
c/o Montgomery Securities                  c/o Montgomery Securities       
600 Montgomery Street                      600 Montgomery Street           
San Francisco, California  94111           San Francisco, California  94111

Karl L. Matthies                           J. Sanford Miller                
c/o Montgomery Securities                  c/o Montgomery Securities        
600 Montgomery Street                      600 Montgomery Street            
San Francisco, California  94111           San Francisco, California  94111 

Bernard M. Notas                           Harry K. Plant                   
c/o Montgomery Securities                  c/o Montgomery Securities        
600 Montgomery Street                      600 Montgomery Street            
San Francisco, California  94111           San Francisco, California  94111 

Bruce G. Potter                            David B. Readerman              
c/o Montgomery Securities                  c/o Montgomery Securities       
600 Montgomery Street                      600 Montgomery Street           
San Francisco, California  94111           San Francisco, California  94111

Rand L. Rosenberg                          Joseph M. Schell                
c/o Montgomery Securities                  c/o Montgomery Securities       
600 Montgomery Street                      600 Montgomery Street           
San Francisco, California  94111           San Francisco, California  94111

Rex Sherry                                 Peter B. Stoneberg              
c/o Montgomery Securities                  c/o Montgomery Securities       
600 Montgomery Street                      600 Montgomery Street           
San Francisco, California  94111           San Francisco, California  94111

Thomas A. Thornhill, III                   John P. Tinker                  
c/o Montgomery Securities                  c/o Montgomery Securities       
600 Montgomery Street                      600 Montgomery Street           
San Francisco, California  94111           San Francisco, California  94111


                                       -14-


Otto V. Tschudi                            Thomas W. Weisel                
c/o Montgomery Securities                  c/o Montgomery Securities       
600 Montgomery Street                      600 Montgomery Street           
San Francisco, California  94111           San Francisco, California  94111

Michael L. Yagemann
c/o Montgomery Securities 
600 Montgomery Street
San Francisco, California  94111


                                       -15-


                          SCHEDULE OF EXISTING SHAREHOLDERS

Name and Address
- ----------------

Marc  Hamon
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Henri Hamon
Netcom Systems Europe
4, rue de Galilee
Immeuble Le Bellevue
ZAC du Moulin a vent 78280
Guyancourt, France

James Jordan
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Warren B. Phelps III
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Jing Zhang
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Stephane Johnson
Netcom Systems, Inc.
20550 Nordhoff Street
Chatsworth, California  91311

Richard Bass
Point of View, Inc.
410 Boylston Street
5th Floor
Boston, Massachusetts  02116


                                       -16-