Exhibit 10.10

                             CHANGE IN CONTROL AGREEMENT                


     This Change in Control Agreement (the "Agreement") is made and entered 
into effective as of May 6, 1998, by and between Netcom Systems, Inc.,  a 
California corporation (the "Company") and the employee of the Company whose 
name appears on the last page hereof (the "Employee").

                                   R E C I T A L S

     A.   The Employee is and has been employed by the Company.

     B.   The Company and the Employee desire to enter into this Agreement to 
provide additional financial security and benefits to the Employee and to 
encourage the Employee to continue his employment with the Company.

     C.   Certain capitalized terms used in the Agreement are  defined in 
Section 3 below.

                                  A G R E E M E N T

     In consideration of the mutual covenants herein contained, and in 
consideration of the continuing employment of the Employee by the Company, 
the parties agree as follows:

     1.   EMPLOYMENT RELATIONSHIP.  The Company and the Employee acknowledge 
that the Employee's employment is and shall continue to be at-will, as 
defined under applicable law.  If the Employee's employment terminates for 
any reason, the Employee shall not be entitled to any payments, benefits, 
damages, awards or compensation other than as provided by this Agreement, or 
as may otherwise be available in accordance with the Company's established 
employee plans and policies at the time of termination.  

     2.   SEVERANCE BENEFITS.

          (a)  TERMINATION AS PART OF OR FOLLOWING A CHANGE OF CONTROL.  
Subject to Sections 4 and 5 below, if the Employee's employment with the 
Company terminates at any time within twenty-four months after a Change of 
Control, then the Employee shall be entitled to receive severance benefits as 
follows:

               (i) INVOLUNTARY TERMINATION.  If the Employee's employment 
terminates as a result of Involuntary Termination other than for Cause, the 
Employee shall be entitled to receive a severance payment equal to one year 
of  the Employee's base compensation for the Company's fiscal year then in 
effect plus Employee's bonus calculated at one hundred percent of target for 
the Company's fiscal year then in effect.  Any severance payments to which 
the Employee is entitled pursuant to this Section 2(a)(i) shall be paid to 
the Employee (or to the Employee's estate or beneficiary in the event of the 
Employee's death) in a lump sum on or prior to the Employee's Termination 
Date.  In addition, if the 



Employee's employment terminates as a result of Involuntary Termination other 
than for Cause, then for the one year period commencing on the Employee's 
Termination Date, Employee shall continue to participate in the Company's 
health and dental insurance benefit plans in accordance with the rules 
established for individual participation in such plans, as such rules may be 
amended from time to time.

               (ii)  VOLUNTARY RESIGNATION; TERMINATION FOR CAUSE.  If the 
Employee voluntarily resigns from the Company (other than as an Involuntary 
Termination), or if the Company terminates the Employee's employment for 
Cause, then the Employee shall not be entitled to receive severance or other 
benefits except for those (if any) as may then be established under the 
Company's then existing severance and benefits plans and policies at the time 
of such resignation or termination.

               (iii)   DISABILITY; DEATH.  If the Company terminates the 
Employee's employment as a result of the Employee's Disability, or if the 
Employee's employment terminates due to the death of the Employee, then the 
Employee shall not be entitled to receive severance or other benefits except 
for those (if any) as may then be established under the Company's then 
existing severance and benefits plans and policies at the time of such 
Disability or death.

          (b)  OPTIONS.  Subject to Sections 4 and 5 below, in the event 
Employee becomes entitled to severance benefits pursuant to Section 2(a)(i) 
above, then the unvested portion of any stock option(s) held by the Employee 
granted by the Company (or any successor in interest thereto to the extent 
that such options were granted in exchange for options granted by the 
Company), shall, as of Employee's Termination Date, immediately vest and 
become exercisable in full, and the Employee shall have the right to exercise 
such additional vested portion of such stock option(s) at such time. 

     3.   DEFINITION OF TERMS.  The following terms referred to in this 
Agreement shall have the following meanings:

          (a)  CAUSE.  "Cause" shall mean (i) any act of personal dishonesty 
taken by the Employee in connection with his responsibilities as an employee 
and intended to result in substantial personal enrichment of the Employee, 
(ii) conviction of a felony that is demonstrably injurious to the Company, 
(iii) a willful act by the Employee which constitutes gross misconduct and 
which is demonstrably injurious to the Company, and (iv) continued violations 
by the Employee of the Employee's obligations as an employee of the Company 
that are demonstrably willful and deliberate on the Employee's part after 
there has been delivered to the Employee a written demand for performance 
from the Company which describes the basis for the Company's belief that the 
Employee has not substantially performed his duties, and Employee has been 
given fourteen (14) days to perform after receipt of such written demand.

          (b)  CHANGE OF CONTROL.  "Change of Control" shall mean the 
occurrence of any of the following events:

               (i)  The acquisition by any "person" (as such term is used in 
Sections 13(d) and 14(d) of the Exchange Act) (other than the Company or a 
person that directly or indirectly controls, 

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is controlled by, or is under common control with, the Company) of the 
"beneficial ownership" (as defined in Rule 13d-3 under said Act), directly or 
indirectly, of securities of the Company representing fifty percent (50%) or 
more of the total voting power represented by the Company's then outstanding 
voting securities; or

               (ii) A change in the composition of the Board of Directors of 
the Company (the "Board") as a result of which fewer than a majority of the 
directors are Incumbent Directors.  "Incumbent Directors" shall mean 
directors who either (A) are directors of the Company as of the date hereof, 
or (B) are elected, or nominated for election, to the Board with the 
affirmative votes of at least a majority of the Incumbent Directors at the 
time of such election or nomination; or

               (iii)   A merger or consolidation of the Company with any 
other corporation, other than a merger or consolidation which would result in 
the voting securities of the Company outstanding immediately prior thereto 
continuing to represent (either by remaining outstanding or by being 
converted into voting securities of the surviving entity) at least fifty 
percent (50%) of the total voting power represented by the voting securities 
of the Company or such surviving entity outstanding immediately after such 
merger or consolidation, or the approval by the stockholders of the Company 
of a plan of complete liquidation of the Company or of an agreement for the 
sale or disposition by the Company of all or substantially all the Company's 
assets.

     (c)  DISABILITY.  "Disability" shall mean that the Employee has been 
unable to substantially perform his duties under this Agreement as the result 
of his incapacity due to physical or mental illness for at least 26 weeks, 
and such incapacity is determined to be total and permanent by a physician 
selected by the Company or its insurers and acceptable to the Employee or the 
Employee's legal representative (such Agreement as to acceptability not to be 
unreasonably withheld).

     (d)  EXCHANGE ACT.  "Exchange Act" shall mean the Securities Exchange 
Act of 1934, as amended.

     (e)  INVOLUNTARY TERMINATION.  "Involuntary Termination" shall mean (i) 
without the Employee's express written consent, the significant reduction of 
the Employee's duties, authority or responsibilities relative to the 
Employee's duties, authority and responsibilities as in effect immediately 
prior to such reduction or the assignment to the Employee of such reduced 
duties, authority or responsibilities; (ii) without the Employee's express 
written consent, a substantial reduction, without good business reasons, of 
the facilities and perquisites (including office space and location) 
available to the Employee immediately prior to such reduction; (iii) without 
the Employee's express written consent, a reduction by the Company in the 
base compensation of the Employee as in effect immediately prior to such 
reduction; (iv) a material reduction by the Company in the kind or level of 
employee benefits to which the Employee is entitled immediately prior to such 
reduction with the result that the Employee's overall benefits package is 
significantly reduced; (v) the relocation of the Employee to a facility or a 
location more than 30 miles from the Employee's then present location, 
without the Employee's express written consent; (vi) any purported 
termination of the Employee by the Company which is not effected for 
Disability or for Cause, or any purported termination for which the grounds 

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relied upon are not valid; or (vii) the failure of the Company to obtain the 
assumption of this agreement by any successors contemplated in Section 6 
below.

          (f)  TERMINATION DATE.  "Termination Date" shall mean (i) if the 
Employee's employment is terminated by the Company for Disability, thirty 
(30) days after notice of termination is given to the Employee (provided that 
the Employee shall not have returned to the performance of the Employee's 
duties on a full-time basis during such thirty (30)-day period), (ii) if the 
Employee's employment is terminated by the Company for any other reason, the 
date on which the Company delivers notice of termination to the Company or 
such later date, not to exceed ninety (90) days, specified in the notice of 
termination, or (iii) if the Agreement is terminated by the Employee, the 
date on which the Employee delivers notice of termination to the Company.

     4.   LIMITATION ON PAYMENTS. 

          (a)  In the event that the severance and other benefits provided 
for in this Agreement or otherwise payable to the Employee (i) constitute 
"parachute payments" within the meaning of Section 280G of the Internal 
Revenue Code of 1986, as amended (the "Code") and (ii) but for this Section 4 
would be subject to the excise tax imposed by Section 4999 of the Code, then 
the Employee's severance benefits under Section 2 shall be payable either (i) 
in full, or (ii) as to such lesser amount which would result in no portion of 
such severance benefits being subject to excise tax under Section 4999 of the 
Code, whichever of the foregoing amounts, taking into account the applicable 
federal, state and local income taxes and the excise tax imposed by Section 
4999, results in the receipt by the Employee on an after-tax basis, of the 
greatest amount of severance benefits under this Agreement, notwithstanding 
that all or some portion of such severance benefits may be taxable under 
Section 4999 of the Code. 

          (b)  If a reduction in the payments and benefits that would 
otherwise be paid or provided to the Employee under the terms of this 
Agreement is necessary to comply with the provisions of Section 4(a), the 
Employee shall be entitled to select which payments or benefits will be 
reduced and the manner and method of any such reduction of such payments or 
benefits (including but not limited to the number of options that would vest 
under Section 2(b)) subject to reasonable limitations (including, for 
example, express provisions under the Company's benefit plans) (so long as 
the requirements of Section 4(a) are met).  Within fifteen (15) days after 
the amount of any required reduction in payments and benefits is finally 
determined in accordance with the provisions of Section 4(c), the Employee 
shall notify the Company in writing regarding which payments or benefits are 
to be reduced.  If no notification is given by the Employee, the Company will 
determine which amounts to reduce.  If, as a result of any reduction required 
by Section 4(a), amounts previously paid to the Employee exceed the amount to 
which the Employee is entitled, the Employee will promptly return the excess 
amount to the Company. 

          (c)   Unless the Company and the Employee otherwise agree in 
writing, any determination required under this Section 4 shall be made in 
writing by the Company's independent public accountants (the "Accountants"), 
whose determination shall be conclusive and binding upon the Employee and the 
Company for all purposes.  For purposes of making the calculations required 
by this Section 4, the Accountants may make reasonable assumptions and 
approximations concerning applicable taxes and 

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may rely on reasonable, good faith interpretations concerning the application 
of Sections 280G and 4999 of the Code. The Company and the Employee shall 
furnish to the Accountants such information and documents as the Accountants 
may reasonably request in order to make a determination under this Section.  
The Company shall bear all costs the Accountants may reasonably incur in 
connection with any calculations contemplated by this Section 4.

     5.   CERTAIN BUSINESS COMBINATIONS.  In the event it is determined by 
the Board, upon receipt of a written opinion of the Company's independent 
public accountants, that the enforcement of any Section or subsection of this 
Agreement, including, but not limited to, Section 2(b) hereof, which allows 
for the acceleration of vesting of options to purchase shares of the 
Company's common stock upon a termination in connection with a Change of 
Control, would preclude accounting for any proposed business combination of 
the Company involving a Change of Control as a pooling of interests, and the 
Board otherwise desires to approve such a proposed business transaction which 
requires as a condition to the closing of such transaction that it be 
accounted for as a pooling of interests, then any such Section of this 
Agreement shall be null and void, but only if the absence of enforcement of 
such Section would preserve the pooling treatment.  For purposes of this 
Section 5, the Board's determination shall require the unanimous approval of 
the disinterested Board members.

     6.   SUCCESSORS.

          (a)  COMPANY'S SUCCESSORS.  Any successor to the Company (whether 
direct or indirect and whether by purchase, lease, merger, consolidation, 
liquidation or otherwise) to all or substantially all of the Company's 
business and assets shall assume the obligations under this Agreement and 
agree expressly to perform the obligations under this Agreement in the same 
manner and to the same extent as the Company would be required to perform 
such obligations in the absence of a succession.  For all purposes under this 
Agreement, the term "Company" shall include any successor to the Company's 
business and assets which executes and delivers the assumption agreement 
described in this Section 6(a) or which becomes bound by the terms of this 
Agreement by operation of law.

          (b)  EMPLOYEE'S SUCCESSORS.  The terms of this Agreement and all 
rights of the Employee hereunder shall inure to the benefit of, and be 
enforceable by, the Employee's personal or legal representatives, executors, 
administrators, successors, heirs, devisees and legatees.

     7.   NOTICE.

          (a)  GENERAL.  Notices and all other communications contemplated by 
this Agreement shall be in writing and shall be deemed to have been duly 
given when personally delivered or when mailed by U.S. registered or 
certified mail, return receipt requested and postage prepaid.  In the case of 
the Employee, mailed notices shall be addressed to him at the home address 
which he most recently communicated to the Company in writing.  In the case 
of the Company, mailed notices shall be addressed to its corporate 
headquarters, and all notices shall be directed to the attention of its Chief 
Financial Officer.

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          (b)  NOTICE OF TERMINATION.  Any termination by the Company for 
Cause or by the Employee as a result of an Involuntary Termination shall be 
communicated by a notice of termination to the other party hereto given in 
accordance with Section 7(a) of this Agreement.  Such notice shall indicate 
the specific termination provision in this Agreement relied upon, shall set 
forth in reasonable detail the facts and circumstances claimed to provide a 
basis for termination under the provision so indicated, and shall specify the 
Termination Date (which shall be not more than ninety (90) days after the 
giving of such notice).  The failure by the Employee to include in the notice 
any fact or circumstance which contributes to a showing of Involuntary 
Termination shall not waive any right of the Employee hereunder or preclude 
the Employee from asserting such fact or circumstance in enforcing his rights 
hereunder.

     8.   MISCELLANEOUS PROVISIONS.

          (a)  NO DUTY TO MITIGATE.  The Employee shall not be required to 
mitigate the amount of any payment contemplated by this Agreement (whether by 
seeking new employment or in any other manner), nor shall any such payment be 
reduced by any earnings that the Employee may receive from any other source.

          (b)  WAIVER.  No provision of this Agreement shall be modified, 
waived or discharged unless the modification, waiver or discharge is agreed 
to in writing and signed by the party hereto whose interests are adversely 
affected thereby (provided that Employee may not sign on behalf of the 
Company for such purpose). No waiver by either party of any breach of, or of 
compliance with, any condition or provision of this Agreement by the other 
party shall be considered a waiver of any other condition or provision or of 
the same condition or provision at another time.

          (c)  WHOLE AGREEMENT.  No agreements, representations or 
understandings (whether oral or written and whether express or implied) which 
are not expressly set forth in this Agreement have been made or entered into 
by either party with respect to the subject matter hereof.  This Agreement 
shall replace and supersede any prior agreement between the parties hereto 
relating to the accrual of any benefits to the Employee in connection with a 
change in control or organic change to the Company (other than stock option 
agreements, if any) and all such agreements shall henceforth be void and of 
no further force and effect.

          (d)  CHOICE OF LAW.  The validity, interpretation, construction and 
performance of this Agreement shall be governed by the laws of the State of 
California.

          (e)  SEVERABILITY.  The invalidity or unenforceability of any 
provision or provisions of this Agreement shall not affect the validity or 
enforceability of any other provision hereof, which shall remain in full 
force and effect.

          (f)  ARBITRATION.  Any dispute or controversy arising out of, 
relating to or in connection with this Agreement shall be settled exclusively 
by binding arbitration in San Jose, California, in accordance with the 
California Code of Civil Procedure section 1280 et seq., as amended, 
including, but not limited to, sections 1283, 1283.05 and 1283.1, such that 
the full degree of discovery permitted under the 

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aforementioned statutes will be allowed in any dispute hereunder.  Judgment 
may be entered on the arbitrator's award in any court having jurisdiction.  
The prevailing party shall be awarded its counsel fees and expenses, 
including costs of arbitration.  Punitive damages shall not be awarded.

          (g)  NO ASSIGNMENT OF BENEFITS.  The rights of any person to 
payments or benefits under this Agreement shall not be made subject to option 
or assignment, either by voluntary or involuntary assignment or by operation 
of law, including (without limitation) bankruptcy, garnishment, attachment or 
other creditor's process, and any action in violation of this Section 8(g) 
shall be void.

          (h)  EMPLOYMENT TAXES.  All payments made pursuant to this 
Agreement will be subject to withholding of applicable income and employment 
taxes.

          (i)  ASSIGNMENT BY COMPANY.  The Company may assign its rights 
under this Agreement to an affiliate, and an affiliate may assign its rights 
under this Agreement to another affiliate of the Company or to the Company; 
provided, however, that no assignment shall be made if the net worth of the 
assignee is less than the net worth of the Company at the time of assignment. 
In the case of any such assignment, the term "Company" when used in a 
section of this Agreement shall mean the corporation that actually employs 
the Employee.

          (j)  COUNTERPARTS.  This Agreement may be executed in counterparts, 
each of which shall be deemed an original, but all of which together will 
constitute one and the same instrument.

                                   * * * *



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     IN WITNESS WHEREOF, each of the parties has executed this Agreement, in 
the case of the Company by its duly authorized officer, as of the day and 
year first above written.

COMPANY:                              NETCOM SYSTEMS, INC.



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

                                      Title:
                                           -------------------------------



EMPLOYEE:                                  -------------------------------

                                       Name:
                                           -------------------------------


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