<PAGE>   1
                                                                    EXHIBIT 10.4

                              EMPLOYMENT AGREEMENT


         This EMPLOYMENT AGREEMENT ("Agreement") is effective as of the 15th day
of January, 2001 by and between Unisphere Networks, Inc. (the "Company"), a
Delaware Corporation with offices at One Executive Drive, Chelmsford, MA 01824,
and Eve Aretakis, an individual residing at 6814 NW 65th Terrace, Parkland,
Florida 33067 (the "Employee").

         WHEREAS, the Company desires to enter into this Agreement to employ the
services of the Employee on the terms and conditions set forth below;

         WHEREAS, the Employee desires to be employed by the Company and is
willing to do so on the terms and conditions set forth below;

         NOW, THEREFORE, in consideration of the above recitals and of the
mutual promises and conditions in this Agreement, it is agreed as follows:

1.       TERM OF EMPLOYMENT.

         The initial term of the Employee's employment under this Agreement (the
"Initial Term") shall be deemed to have commenced on January 15, 2001 and shall
terminate on the second (2nd) anniversary thereof. The Initial Term shall be
automatically extended for additional terms of successive one (1) year periods
(the "Additional Employment Term") unless the Company or Employee gives written
notice to the other at least ninety (90) days prior to the expiration of the
then Initial Employment Term or Additional Employment Term of the termination of
Employee's employment hereunder at the end of such Employment Term. The term of
this Agreement, including the Initial Employment Term and the Additional
Employment Term, as from time to time is modified in writing by and between the
parties and in effect, is hereafter referred to as the "Employment Term" or the
"term of this Agreement" or "the term hereof." Upon termination of the term
hereof, this Agreement and all obligations of the parties hereunder shall
terminate, except as provided in Sections 5, 6, 7 and 8 hereof. If the
Employment Term ends at the option of the Company, the Employee shall be
considered to have been terminated "without cause" and shall be entitled to
those termination payments and benefits specified in Section 6(c). The Employee
and the Company have no other agreement, express or implied or written or oral,
regarding the term of their employment relationship other than the agreement set
forth in this paragraph.

2.       EMPLOYMENT AND DUTIES.

a.       During the Term, the Company shall employ the Employee on a full-time
basis as Vice President and General Manager of the Company with responsibility
for Voice Business Unit and such other duties as may be assigned to her from
time-to-time by the Company's President and subject to the supervision of the
President. The Employee agrees to use her diligent efforts in and shall devote
at least forty (40) hours per week to the performance of her duties during the
Term and to the advancement of the interests of the Company and its affiliates.


                                       1
<PAGE>   2



b.       The services of the Employee shall be performed at the Company's
offices located at One Executive Drive, Chelmsford, Massachusetts or at such
other facility designated by the Company. If the Company's offices are moved
from the above mentioned address to another location within the greater Boston,
Massachusetts metropolitan area, the Employee agrees to perform the employee's
services at such new address.

c.       Employee will sign separate agreements, policies or certifications
regarding Confidentiality/Invention and Trade Secret Agreement and, in the
future will sign separate agreements, policies or certifications including, but
not limited to, Ethical Business Practices, Conflicts of Interest and Insider
Trading, on such forms as are or may be adopted by the Company from time to time
for its executives. Any such agreements, policies or certifications shall
supplement the terms and conditions of this Agreement, including, without
limitation, the provisions of Section 5 and 7 hereof.

3.       EMPLOYEE'S OUTSIDE BUSINESS ACTIVITIES.

a.       During the Term, the Employee shall devote such time, interest and
effort as shall be necessary to satisfactorily perform and discharge all duties
and responsibilities of the Employee's position and shall not, without the prior
written consent of the Company's President, render to others services of any
kind for compensation, or engage in any other business activity that would
materially interfere with the performance of the Employee's duties under this
Agreement.

b.       During the Term, the Employee shall not take any action, without the
prior written consent of the Company's President, which consent he/she may grant
or withhold in his/her sole discretion, to establish, form or become employed
upon termination of employment with the Company by a competing business anywhere
in the United States or in any foreign country.

c.       The Employee's failure to comply with the provisions of this Section
shall give the Company the right (in addition to any other remedies and rights
the Company may have) to terminate this Agreement.

4.       COMPENSATION.

a.       BASE SALARY. The Company shall pay the Employee, in arrears (payable no
less than on a monthly basis) in equal installments at such intervals as the
Company shall generally pay its senior  executives, a base salary (the
"Base Salary") at a rate of  $270,004.80 per year.

b.       BONUS. In the event that the Company adopts and implements a bonus plan
for its executive employees, then Employee shall be eligible to participate in
that plan. The parties hereby acknowledge and agree that there is no bonus plan
currently in effect for the Company's fiscal year ending September 30, 2001 and
whether or not the Company elects to adopt a bonus plan in the future is in the
Company's sole discretion. The parties hereby acknowledge and agree that the
Employee's entitlement to any bonus in respect of the year of termination shall
be governed by the

                                       2
<PAGE>   3


terms of such bonus plan provided, however, that the parties agree that if the
Employee's employment terminates during any bonus plan year, then the Employee
shall be entitled to receive a pro-rata portion of the bonus for that plan year
through the date of termination if the bonus plan objectives are actually
achieved in that plan year and the Company pays a bonus to the plan
participants, which bonus shall be paid to the Employee at the same time as
bonuses are generally paid to the other bonus plan participants.

c.       STOCK OPTION AWARD. The Company shall submit to the Company's Board of
Directors a recommendation that the Employee be awarded 300,000 stock options
under the Company's 1999 Stock Incentive Plan (the "Stock Incentive Plan") at an
exercise price to be determined by the Board of Directors, which options shall
be either incentive stock options (ISO's) or non-qualified options, or a
combination thereof, as determined by the Board of Directors in its sole
discretion, provided, however, that the exercise price of said options shall be
set at a price no greater than the fair market value of the Company's common
stock as of the grant date of the award to the Employee. The vesting of such
options shall be as follows: one-quarter (1/4) of the total options granted
shall vest on the first anniversary of the Employee's date of hire and 6.25% of
the remaining options shall vest following completion of each quarterly
anniversary thereafter, subject to the Employee's continued employment, and the
terms and conditions of the Company's Stock Incentive Plan. The Employee shall
receive a Stock Option Agreement following the Board of Director's approval
which shall set forth the number of options (both incentive and non-qualified
options), the exercise price thereof, the four year vesting schedule and such
other terms and conditions as set forth in and governed by the Stock Incentive
Plan. If the Board of Directors fail either to award the full number of such
stock options and/or to approve the accelerated vesting provisions of Section 6
within 90 days of Employee's commencement of employment, the Employee may
immediately terminate (without prior notice) her employment for "Good Reason."

d.       OTHER BENEFITS. During the Term, the Employee shall be entitled to
participate in such employee benefit programs as may be maintained from time to
time by the Company in its sole discretion for the purpose of covering salaried
employees of the Company. This Section 4(d) shall in no way create or be deemed
to create any obligation, express or implied, on the part of the Company with
respect to the continuation of any benefit or other plan or arrangement
maintained on or prior to the date of this Agreement or the creation and
maintenance of any particular benefit or other plan or arrangement at any time
during the Term. The Company shall provide the Employee with the same or similar
medical, dental, life and disability insurance benefits, if any, provided to
other salaried employees of the Company.

e.       WITHHOLDING. All payments made to the Employee pursuant to this Section
4 shall be subject to withholding to the extent required under applicable law.

f.       BUSINESS EXPENSES. The Company will reimburse the Employee for business
expenses in accordance with Company policy.

                                       3
<PAGE>   4

5.       CONFIDENTIAL INFORMATION, TRADE SECRETS, DESIGNS.

a.       The Employee acknowledges and agrees that information concerning the
work conducted by the Company may constitute confidential information, trade
secrets or copyrightable or patentable works or expressions, including, but not
limited to, know-how, design information or concepts, advertising concepts,
matters which are subject to trademark, copyright or patent protection,
manufacturing information or concepts, marketing or sales information, price and
cost information, customer information, including points of contact at customers
and product requirements and buying habits of customers, financial information
regarding the Company, information regarding suppliers, and all personnel
information. The Employee further acknowledges that such information will be
entrusted to her by the Company and that the Employee will take all steps
necessary to protect the confidentiality of such information, including abiding
by all internal regulations, policies, procedures or safeguards to protect such
information from disclosure and to implement any necessary regulations,
procedures or safeguards to protect any such confidential information or trade
secret information from disclosure or to allow such information in any way to
lose its protection as intangible assets of the Company. The Employee agrees to
execute any documents necessary to protect the Company's rights or interests in
such inventions, patentable developments, copyrightable works, designs,
trademarks, advertising concepts or other confidential or trade secret
information.

b.       During the Term hereof and during the entire course of her employment
with the Company and for a period of five (5) years following the termination of
her employment, the Employee promises and agrees not to disclose to any other
person or entity any trade secrets or confidential information, unless
specifically authorized in writing in advance by the Company's President to do
so. If the Company's President gives the Employee written authorization to make
any such disclosure, the Employee shall do so only within the limits and to the
extent of the authorization.

c.       The Employee also agrees, during the Term of this Agreement and during
the entire course of her employment with the Company, to promptly divulge to the
Company all developments and information related to the Company's business, or
which relate to any actual or anticipated research and development of the
Company, and to assign any and all rights of any kind or character in such
patents, trademarks, copyrights, inventions and the like to the Company. The
Employee's duty to assign all such developments and information shall be
applicable to any invention or information the Employee develops which relates
at the time of conception or reduction to practice to the Company's business, or
actual or anticipated research or development, which results from any work
performed by the Employee for the Company, or any invention or information which
involves, in any way, the use of the Company's equipment, supplies, facilities,
trade secrets, or confidential information. The Employee agrees to execute all
documents necessary to the perfection and/or protection of the Company's
interest or rights in such intangible assets.

d.       The Employee also acknowledges that by virtue of her employment with
the Company, she will have access to confidential information, trade secrets,
copyrightable works or expressions, design information or concepts,
manufacturing information or concepts, patentable information or concepts,
advertising concepts, and other confidential information and trade secrets of
the Company as set forth more fully above, which are the intangible assets of
the Company. The Employee



                                       4
<PAGE>   5
agrees that her participation in the development of these intangible assets or
her knowledge of the existence of such information does not give rise to any
rights on the Employee's behalf to disclose or utilize these intangible assets
or information.

e.       The Employee acknowledges that during the course of Employee's
employment, the Employee will obtain knowledge and skills pertaining to the
Company's industry, manufacturing processes, methods of production, methods of
buying and selling which are "know-how" acquired by virtue of the Employee's
employment relationship with the Company. This "know-how" is also an intangible
asset of the Company.

f.       The Employee agrees during the entire course of her employment with the
Company to offer or otherwise make known or available to the Company and without
additional payment or other economic benefit to her, any business prospects,
contacts or other business opportunities which she may discover, find, develop
or otherwise have available to her in any field in which the Company is engaged,
and further agrees that any such business prospects, contacts or other business
opportunities shall be the property of the Company.

g.       During the entire course of her employment with the Company and for a
period of one (1) year following her termination of employment, the Employee
promises and agrees not to: (i) hire, solicit or attempt to hire, whether on
behalf of herself or any person, firm, corporation or other business
organization with which the Employee is affiliated in any capacity, any employee
of the Company or any of its affiliates, or (ii) encourage, solicit or induce
any such employee to terminate his or her relationship or employment with the
Company or any affiliate, or (iii) solicit any customer of the Company for or on
behalf of herself or any person, firm, corporation or other business
organization with which the Employee is affiliated in any capacity. For purposes
of this Agreement, the foregoing restrictions shall apply to any employee who
was employed by the Company at the time of the termination of the Employee's
employment with the Company or at any time during the 180 day period preceding
said termination of Employee's employment.

6.       TERMINATION.

         Prior to the expiration of the Employment Term as provided in Section 1
hereof, this Agreement may be terminated as follows:

a.       At any time by mutual written consent of the Employee and the Company.
Upon such termination as provided in this Section 6(a), the Employee shall be
entitled to receive any vacation pay and Base Salary pursuant to Section 4(a)
that is accrued and unpaid as of the termination date, with such amount payable
at the same intervals as Base Salary payments were made under Section 4 hereof,
subject to withholding. In addition, the Employee shall be entitled to exercise
any options which were vested on or before the termination date in accordance
with and subject to the terms of the Stock Incentive Plan, including, but not
limited, the time period for such exercise and any provisions regarding
forfeiture. Upon payment of such amount, the Company shall have no further
obligations hereunder, including, without limitation, the obligation to pay the
Employee any bonus


                                       5



<PAGE>   6


in respect of the year of termination except as provided in Section 4(b) hereof
or any subsequent year, and the provisions of Sections 5, 7 and 8 shall remain
in effect in accordance with their terms.

b.       Upon the death or following the permanent disability (as defined below)
of the Employee. For purposes of this Agreement, the Employee shall have a
"permanent disability" if an independent medical doctor (selected by the
Company's health or disability insurer) certifies that the Employee has for four
(4) months, consecutive or non-consecutive, in any twelve-month period been
physically or mentally disabled or incapacitated in a manner which seriously
interferes with her ability to perform her essential job responsibilities under
this Agreement despite reasonable accommodation. Upon termination of the
Employee's employment pursuant to this Section 6(b), (i) the Company shall pay
the Employee or her estate any vacation pay and Base Salary pursuant to Section
4(a) that is accrued and unpaid as of the termination date, and upon the making
of such payment the Company shall have no further obligations hereunder,
including, without limitation, the obligation to pay the Employee any bonus in
respect of the year of termination except as otherwise provided in Section 4(b)
hereof or any subsequent year, and (ii) the provisions of Sections 5, 7 and 8 to
the extent relevant shall remain in effect in accordance with their terms. In
addition, the Employee shall be entitled to exercise any options which were
vested on or before the termination date in accordance with and subject to the
terms of the Stock Incentive Plan, including, but not limited, the time period
for such exercise and any provisions regarding forfeiture.

c.       At any time by the Company without cause upon written notice to the
Employee. In the event of termination of the Employee's employment by the
Company pursuant to this Section 6(c), the Company shall pay to the Employee any
vacation and Base Salary pursuant to Section 4(a) that is accrued and unpaid as
of the termination day. The Company also shall pay to the Employee severance
pay, provided that the Employee executes the Company's form of Termination
Agreement releasing her claims against the Company and its affiliates,
consisting of an amount equal to the Base Salary that would have been payable
for six (6) months from the date of termination had the Employee remained an
employee of the Company hereunder until that date, with such amount payable at
the same intervals as Base Salary payments were made under Section 4 hereof,
subject to withholding. In the alternative, at the Company's option, the
Employee shall receive a lump-sum payment equal to the salary continuation
payments due under the immediately preceding sentence. Upon payment of such
amount, the Company shall have no further obligations hereunder, including,
without limitation, the obligation to pay the Employee any bonus in respect of
the year of termination except as otherwise provided in Section 4(b) hereof or
any subsequent year, and the provisions of Sections 5, 7 and 8 shall remain in
effect in accordance with their terms. In addition, the Employee shall become
immediately vested as of the termination date, for the lesser of: (i) 37,500
options of the 300,000 option under the Company's Stock Incentive Plan or (ii)
the remaining balance (as of the termination date) of the unvested options of
the 300,000 option award under the Company's Stock Incentive Plan if said amount
is less than 37,500 options. The Employee may or may not be vested in any
options as of the termination date under the vesting schedule set forth in her
Stock Option Award but to the extent that the Employee is so vested in any of
said options, the accelerated vesting described in the foregoing sentence shall
be in addition to the shares which have vested in accordance with the terms of
the Stock Option Award. The Employee


                                       6
<PAGE>   7

shall be entitled to exercise any vested options which were vested or become
vested as of the date of termination in accordance with the terms of the Stock
Incentive Plan, including, but not limited to, the time period for such exercise
and any provisions regarding forfeiture.

d.       At any time by the Employee upon sixty (60) days prior written notice
to the Company. Upon termination by the Employee as provided in this Section
6(d), the Employee shall be entitled to receive any vacation pay and Base Salary
pursuant to Section 4(a) that is accrued and unpaid as of the termination date,
with such amount payable at the same intervals as Base Salary payments were made
under Section 4 hereof, subject to withholding. Upon payment of such amount, the
Company shall have no further obligations hereunder, including, without
limitation, the obligation to pay the Employee any bonus in respect of the year
of termination except as otherwise provided in Section 4(b) hereof or any
subsequent year, and the provisions of Sections 5, 7 and 8 shall remain in
effect in accordance with their terms. In addition, the Employee shall be
entitled to exercise any options which were vested as of the termination date in
accordance with and subject to the terms of the Stock Incentive Plan, including,
but not limited, the time period for such exercise and any provisions regarding
forfeiture.

e.       At any time for cause by the Company upon written notice to the
Employee. For purposes of this Agreement, a termination shall be for cause if:

         (i) the Employee shall commit an act of fraud, embezzlement,
         misappropriation, dishonesty or breach of fiduciary duty against the
         Company or any of its affiliates; or shall be convicted in a court of
         competent jurisdiction or shall plead guilty or nolo contendere to any
         felony or any other crime involving moral turpitude; or shall fail in
         the performance of her job responsibilities to comply with or violate a
         provision of federal, state or local law or regulation applicable to
         the Company or any of its affiliates; or upon the issuance of any
         order, whether civil, criminal or administrative, barring the Employee
         from continuing to carry on any assigned duties;

         (ii) the Employee shall commit a willful or material breach of any of
         the covenants, terms or provisions of Sections 3, 5 or 7 hereof; or

         (iii) the Employee shall refuse to follow the written direction of a
         more senior officer of the Company or the Board of Directors, provided
         that the foregoing refusal shall not be "for Cause" if the Employee in
         good faith reasonably believes that such direction is illegal,
         unethical or immoral and promptly so notifies in writing the Board or
         the more senior officer (whichever is applicable), or the Employee
         shall substantially fail to perform the Employee's duties hereunder in
         a manner acceptable to the Company's President or Board of Directors,
         provided that the Company shall notify the Employee in writing of the
         basis for the termination pursuant to this Subsection (iii) and provide
         the Employee with thirty (30) days to cure the same, provided, however,
         that the Company shall not be required to provide the Employee with
         such notice and opportunity to cure (i) more than one (1) time during
         any consecutive three hundred sixty five (365) day period during the
         course of her employment and (ii) more than once with respect to any
         particular incident of an alleged failure to obey or perform.




                                       7
<PAGE>   8



Upon termination for cause as provided in Section 6(e), the Employee shall be
entitled to receive any vacation pay and Base Salary payments pursuant to
Section 4(a) that are accrued and unpaid as of the termination date (subject to
the further provisions of this Section 6). Upon payment of such amount, the
Company shall have no further obligations hereunder after the date of
termination, including, without limitation, the obligation to pay the Employee
any bonus, if any, in respect of the year of termination except as otherwise
provided under Section 4(b) hereof or any subsequent year, and the Company shall
be entitled to exercise any rights which the Company may have against the
Employee (including the rights of recovery by offset of any amounts due but not
yet paid to the Employee), and the provisions of Sections 5, 7 and 8 shall
remain in effect in accordance with their terms. In addition, the Employee may
be entitled to exercise any options which were vested as of the termination date
in accordance with and subject to the terms of the Stock Incentive Plan,
including, but not limited, the time period for such exercise and any provisions
regarding forfeiture.


f.       The Employee may terminate her employment for Good Reason (as defined
below). For purposes of this Agreement, the Employee shall have "Good Reason" to
terminate her employment with the Company in the event of: (i) any material
breach by the Company of the provisions of this Agreement; (ii) any change of
control of the Company other than an internal reorganization; (iii) any
substantial reduction in the Employee's job responsibilities without the
Employee's consent. Notwithstanding the foregoing, the Employee shall not have
Good Reason to terminate her employment unless and until she has provided the
Company with written notice of such breach or event at least seven (7) days in
advance of her intended termination date and an opportunity and period to cure
such breach or event within the fourteen (14) day period following such notice;
provided further, however, if the Company cures such breach or event, the
Employee shall not have Good Reason to terminate this Agreement. In the event of
termination of the Employee's employment by the Company pursuant to this Section
6(f), the Company shall pay to the Employee any vacation pay and Base Salary
pursuant to Section 4(a) that is accrued and unpaid as of the termination date.
The Company also shall pay to the Employee severance pay, provided that the
Employee executes the Company's form of Termination Agreement releasing her
claims against the Company and its affiliates, consisting of an amount equal to
the Base Salary that would have been payable for the six (6) month period
following the date of termination had the Employee remained an employee of the
Company hereunder until that date, with such amount payable at the same
intervals as Base Salary payments were made under Section 4 hereof, subject to
withholding. In the alternative, at the Company's option, the Employee shall be
entitled to a lump-sum payment equal to the salary continuation payments due
under the immediately preceding sentence. Upon payment of such amounts, the
Company shall have no further obligations hereunder, including, without
limitation, the obligation to pay the Employee any bonus in respect of the year
of termination except as otherwise provided in Section 4(b) hereof or any
subsequent year, and the provisions of Sections 5, 7 and 8 shall remain in
effect in accordance with their terms. In addition, the Employee shall become
immediately vested as of the termination date, for the lesser of: (i) 37,500
options of the 300,000 option award under the Company's Stock Incentive Plan or
(ii) the remaining balance (as of the termination date) of the unvested options
of the 300,000 option award under the Company's Stock Incentive Plan if said
amount is less than 37,500 options. The Employee may or may not be vested in any
options as of the termination date under the vesting schedule set forth in her
Stock



                                       8
<PAGE>   9
Option Award but to the extent that the Employee is so vested in any of said
options, the accelerated vesting described in the foregoing sentence shall be in
addition to the shares which have vested in accordance with the terms of the
Stock Option Award. The Employee shall be entitled to exercise any vested
options which were vested or become vested as of the date of termination in
accordance with the terms of the Stock Incentive Plan, including, but not
limited to, the time period for such exercise and any provisions regarding
forfeiture.

7.       NON-COMPETITION.

         As an inducement to the Company to enter into this Agreement with
Employee and to employ Employee as its Vice President and General Manager,
during the Term of this Agreement and during the six month period that the
Employee receives severance post-termination (either in the form of salary
continuation payments or in a lump-sum payment), as provided under the terms and
provisions of Sections 6(c) or 6(f), the Employee agrees that she shall not,
anywhere in any county of any state in the United States and in any and all
foreign countries, without the express written advance consent of the President
of the Company, which consent he/she may grant or withhold in his/her sole
discretion, directly or indirectly, either as an employee, employer, trustee,
consultant, agent, principal, partner, corporate officer, director, creditor,
owner or shareholder or in any other individual or representative capacity,
promote, participate, invest or engage in any activity or other business
competitive with the Company's business in the design, manufacture, development,
distribution, marketing or sales of any products or services for the following
market: the internet infrastructure for carrier networks. The sole exception to
this restriction shall be that the Employee may make passive investments in a
competitive enterprise the shares of which are publicly traded if such
investment constitutes less than one percent of the outstanding capital stock or
other interests in the equity of such enterprise. Without implied limitation,
the foregoing covenant shall include: (i) the hiring or attempting to hire any
employee of the Company or any of its affiliates, (ii) encouraging or inducing
any such employee to terminate his or her relationship or employment with the
Company or any affiliate, (iii) soliciting for or on behalf of any competitor
any customer of the Company, and (iv) diverting to any competitor any customer
of the Company. For purposes of this Agreement, the foregoing restrictions shall
apply to any employee who was employed by the Company at the time of the
termination of the Employee's employment with the Company or at any time during
the 180 day period preceding said termination of Employee's employment. As of
the date of this Agreement, the Employee is not performing any consulting or
other duties for, and is not a party to any similar agreement with, any business
or venture competing in the relevant market described hereinabove.

8.       SPECIFIC PERFORMANCE; SEVERABILITY.

a.       It is specifically understood and agreed that any breach of the
provisions of Sections 3, 5 or 7 of this Agreement by the Employee is likely to
result in irreparable injury to the Company, that the remedy at law alone will
be an inadequate remedy for such breach and that, in addition to any other
remedy it may have, the Company shall be entitled to enforce the specific
performance of this Agreement by the Employee and to seek both temporary and
permanent injunctive relief (to the extent permitted by law), without the
necessity of proving actual damages.




                                       9
<PAGE>   10



b.       In case any of the provisions contained in this Agreement shall be for
any reason be held to be invalid, illegal or unenforceable in any respect by a
court of competent jurisdiction, any such invalidity, illegality or
unenforceability shall not affect any other provision of this Agreement, but
this Agreement shall be construed as if such invalid, illegal or unenforceable
provision had been limited or modified (consistent with its general intent) to
the extent necessary to make it valid, legal and enforceable, or if it shall not
be possible to so limit or modify such invalid, illegal or unenforceable
provision or part of a provision, this Agreement shall be construed as if such
invalid, illegal or unenforceable provision or part of a provision had never
been contained in this Agreement.

9.       NOTICES.

         All notices permitted or required hereunder shall be deemed to have
been duly given if delivered personally or if sent by certified or registered
mail or overnight courier, postage prepaid, to the parties at their respective
addresses set forth below or to such other address as any party may hereafter
designate.

To the Company:                           With a copy to:
Unisphere Networks, Inc.                  Unisphere Networks, Inc.
One Executive Drive                       One Executive Drive
Chelmsford, MA 01824                      Chelmsford, MA 01824
Attention: President                      Attention: General Counsel

To the Employee:

Eve Aretakis
6814 NW 65th Terrace
Parkland, FL 33067

10.      WAIVER.

         Neither party's failure to enforce any provision or provisions of this
Agreement shall be deemed in any way to be or construed as a waiver of any such
provision or provisions, nor prevent that party thereafter from enforcing each
and every provision of this Agreement. The rights granted both parties herein
are cumulative and shall not constitute a waiver of either party's right to
assert all other legal remedies available to it under the circumstances.

11.      MISCELLANEOUS.

         This Agreement shall be governed by and construed under the laws of the
Commonwealth of Massachusetts, and shall not be modified or discharged in whole
or in part except by an agreement in writing signed by the Company and the
Employee. The parties consent to personal jurisdiction, service of process and
venue in the federal or state courts of Massachusetts with respect

                                       10
<PAGE>   11


to any and all claims or disputes between the parties arising in connection with
this Agreement. The parties hereby agree that the prevailing party to any
litigation commenced pursuant to this Agreement shall be entitled to recover its
or her reasonable attorney's fees incurred in connection with that matter. This
Agreement shall inure to the benefit of the successors and assigns of the
Company, including the successors of the Company by way of merger, consolidation
or transfer of substantially all the assets of the Company, and may not be
assigned by the Employee except as provided expressly herein in Section 6(b).

12.      ENTIRE AGREEMENT.

         This Agreement, and the agreement, policies and certifications
referenced in Section 2(c) hereof, contain the entire agreement of the parties
and supersedes and replaces any other agreements or understandings between them
with respect to the subject matter of this Agreement.

         IN WITNESS WHEREOF, the parties have duly executed this Agreement as of
the day and year first written above.


                                        UNISPHERE NETWORKS, INC.




                                        By: /s/ James A. Dolce
                                           -------------------------------------
                                           James A. Dolce
                                           Chief Executive Officer and President


                                        /s/ Eve Aretakis
                                        ----------------------------------------
                                        Eve Aretakis



                                       11