Document:

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                                                                   Exhibit 10.27

                              CLARENT CORPORATION

              EXECUTIVE CHANGE IN CONTROL SEVERANCE BENEFIT PLAN

Section 1.  Introduction.

     This Clarent Corporation Executive Change in Control Severance Benefit Plan
(the "Plan") was established effective April 12, 2001.  The purpose of the Plan
is to provide for the payment of severance benefits to certain eligible
employees of Clarent Corporation (the "Company") whose employment with the
Company is terminated following a Change in Control.  This Plan shall supersede
any severance benefit plan (other than the Senior Executive Change in Control
Severance Benefit Plan or the Employee Change in Control Severance Benefit
Plan), policy or practice previously maintained by the Company.  This Plan
document also is the Summary Plan Description for the Plan.

Section 2.  Definitions.

     For purposes of the Plan, the following terms are defined as follows:

          (a)  "Base Salary" means the Eligible Employee's annual base salary as
in effect during the last regularly scheduled payroll period immediately
preceding the Change in Control or as increased thereafter.

          (b)  "Board" means the Board of Directors of the Company.

          (c)  "Change in Control" means:

               (i)   the sale of all or substantially all of the Company's
assets to a single purchaser or a group of related purchasers;

               (ii)  the sale, exchange or other disposition, in a single
transaction, of more than fifty percent (50%) of the Company's outstanding
capital stock; or

               (iii) a merger or consolidation of the Company in a transaction
following which the Company's stockholders receive less than fifty percent (50%)
of the outstanding voting shares of the surviving entity.

          (d)  "Company" means Clarent Corporation or, following a Change in
Control, the surviving entity resulting from such transaction.

          (e)  "Continuation Period" means the period for which an Eligible
Employee is entitled to receive the benefits described in Section 4. The
Continuation Period is six (6) months.

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          (f)  "Covered Termination" means an Involuntary Termination Without
Cause which occurs within thirteen (13) months following the effective date of a
Change in Control.

          (g)  "Involuntary Termination Without Cause" means the Eligible
Employee's dismissal or discharge for reasons other than Cause. For this
purpose, "Cause" means that, in the reasonable determination of the Company, the
Eligible Employee has

               (i)   been convicted of or pleaded guilty or nolo contendere to a
felony or any crime involving moral turpitude or dishonesty;

               (ii)  participated in a fraud or act of dishonesty against the
Company;

               (iii) willfully and materially breached a Company policy;

               (iv)  intentionally damaged the Company's property;

               (v)   willfully and materially breached the Eligible Employee's
Proprietary Information and Inventions Agreement with the Company; or

               (vi)  engaged in conduct that, in the reasonable determination of
the Company, demonstrates gross unfitness to serve.

     Notwithstanding the foregoing, Cause shall not exist based on conduct
described in clause (iii) or (vi) unless the conduct described in such clause
has not been cured within thirty (30) days following the Eligible Employee's
receipt of written notice from the Company specifying the particulars of the
conduct constituting Cause.

Section 3. Eligibility For Benefits.

           (a) General Rules. Subject to the requirements set forth in this
Section, the Company will provide the severance benefits described in Section 4
of the Plan to Eligible Employees. For purposes of this Plan, "Eligible
Employees" are all full-time and part-time regular hire employees of the Company
who hold a position of Vice President or Director and whose employment with the
Company terminates due to an Involuntary Termination Without Cause, within
thirteen (13) months following the effective date of a Change in Control.

               (i)   In order to be eligible to receive benefits under the Plan,
an Eligible Employee must remain on the job until his or her date of
termination, as scheduled by the Company.

               (ii)  In order to be eligible to receive benefits under the Plan,
an Eligible Employee also must execute a general waiver and release in
substantially the form attached hereto as Exhibit A, Exhibit B or Exhibit C, as
appropriate, and such release must become effective in accordance with its
terms.

                                       2.
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          (b)  Exceptions to Benefit Entitlement. An employee who otherwise is
an Eligible Employee will not receive benefits under the Plan in any of the
following circumstances, as determined by the Company in its sole discretion:

               (i)   The employee has executed an individually negotiated
employment contract or agreement with the Company relating to severance benefits
that is in effect on his or her termination date which provides severance
benefits greater than the benefits otherwise payable under this Plan.

               (ii)  The employee is terminated for Cause, as defined in Section
2(h).

               (iii) The employee voluntarily terminates employment with the
Company. Voluntary terminations include, but are not limited to, resignation,
retirement or failure to return from a leave of absence on the scheduled date.

               (iv)  The employee voluntarily terminates employment with the
Company in order to accept employment with another entity that is wholly or
partly owned (directly or indirectly) by the Company or an affiliate of the
Company.

               (v)   The employee continues employment, with the same title and
reporting responsibilities and no diminution in duties and responsibilities,
with a successor corporation following a Change in Control.

Section 4.  Amount Of Benefit.

            (a)  Salary Continuation. Each Eligible Employee shall continue to
receive Base Salary for the Continuation Period. Such amount shall be paid in
regular installments on the normal payroll dates of the Company and shall be
subject to all required tax withholding.

            (b)  Continued Insurance Benefits. Provided that the Eligible
Employee elects continued coverage under the Consolidated Omnibus Budget
Reconciliation Act of 1985 ("COBRA"), the Company shall pay the portion of
premiums of each Eligible Employee's group medical, dental and vision coverage,
including coverage for the Eligible Employee's eligible dependents, that the
Company paid prior to the Covered Termination or, if shorter, for the duration
of the COBRA continuation period. Such premium payments shall continue for the
duration of the Continuation Period; provided, however, that no such premium
payments shall be made following the effective date of the Eligible Employee's
coverage by a medical, dental or vision insurance plan of a subsequent employer.
Each Eligible Employee shall be required to notify the Company immediately if
the Eligible Employee becomes covered by a medical, dental or vision insurance
plan of a subsequent employer.

     No provision of this Plan will affect the continuation coverage rules under
COBRA, except that the Company's payment of any applicable insurance premiums
during the Continuation Period will be credited as payment by the Eligible
Employee for purposes of the Eligible Employee's payment required under COBRA.
Therefore, the period during which an Eligible Employee must elect to continue
the Company's group medical coverage at his or her own expense under COBRA, the
length of time during which COBRA coverage will be made available to the
Eligible Employee, and all other rights and obligations of the Eligible Employee

                                       3.
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under COBRA (except the obligation to pay insurance premiums that the Company
pays during the Continuation Period) will be applied in the same manner that
such rules would apply in the absence of this Plan.  At the conclusion of the
Continuation Period, the Eligible Employee will be responsible for the entire
payment of premiums required under COBRA for the duration of the COBRA
continuation period.  For purposes of this Section 4(b), applicable premiums
that will be paid by the Company during the Continuation Period shall not
include any amounts payable by the Eligible Employee under a Section 125 health
care reimbursement plan, which amounts, if any, are the sole responsibility of
the Eligible Employee.

            (c)  Acceleration of Vesting. Effective as of the date of the
Covered Termination, each Eligible Employee shall be credited with twenty-four
(24) months of additional vesting under all options to purchase the Company's
Common Stock that the Eligible Employee holds on such date. Notwithstanding the
foregoing, no Eligible Employee shall be entitled to receive such additional
vesting credit if the transaction constituting the Change in Control that
triggers the Eligible Employee's entitlement to benefits under the Plan (i)
occurs within six (6) months following the effective date of the Plan and (ii)
is to be accounted for as a "pooling of interests" for financial accounting
purposes.

Section 5.  Limitations on Benefits.

            (a)  Release.  To receive benefits under this Plan, an Eligible
Employee must execute a release of claims in favor of the Company, in the form
attached to this Plan as Exhibit A, Exhibit B or Exhibit C, as appropriate, and
such release must become effective in accordance with its terms.

            (b)  Certain Reductions and Offsets. Notwithstanding any other
provision of the Plan to the contrary, any benefits payable to an Eligible
Employee under this Plan shall be reduced by any severance benefits payable by
the Company to such individual under any other policy, plan, program or
arrangement, including, without limitation, a contract between the Eligible
Employee and any entity, covering such individual. Furthermore, to the extent
that any federal, state or local laws, including, without limitation, so-called
"plant closing" laws, require the Company to give advance notice or make a
payment of any kind to an Eligible Employee because of that Eligible Employee's
involuntary termination due to a layoff, reduction in force, plant or facility
closing, sale of business, change of control, or any other similar event or
reason, the benefits payable under this Plan shall either be reduced or
eliminated. The benefits provided under this Plan are intended to satisfy any
and all statutory obligations that may arise out of an Eligible Employee's
involuntary termination of employment for the foregoing reasons, and the Plan
Administrator shall so construe and implement the terms of the Plan.

            (c)  Mitigation. Except as otherwise specifically provided herein,
Eligible Employees shall not be required to mitigate damages or the amount of
any payment provided under this Plan by seeking other employment or otherwise,
nor shall the amount of any payment provided for under this Plan be reduced by
any compensation earned by any Eligible Employee as a result of employment by
another employer or any retirement benefits received by such Eligible Employee
after the date of the Covered Termination.

                                       4.
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          (d)  Termination of Benefits. Benefits under this Plan shall terminate
immediately if the Eligible Employee, at any time, violates any proprietary
information or confidentiality obligation to the Company.

          (e)  Non-Duplication of Benefits. No Eligible Employee is eligible to
receive benefits under this Plan more than one time.

          (f)  Indebtedness of Eligible Employees. If a terminating employee is
indebted to the Company or an affiliate of the Company at his or her termination
date, the Company reserves the right to offset any severance payments under the
Plan by the amount of such indebtedness.

          (g)  Parachute Payments. If any payment or benefit the Eligible
Employee would receive in connection with a Change in Control from the Company
or otherwise ("Payment") would (i) constitute a "parachute payment" within the
meaning of Section 280G of the Internal Revenue Code of 1986, as amended (the
"Code"), and (ii) but for this sentence, be subject to the excise tax imposed by
Section 4999 of the Code (the "Excise Tax"), then such Payment shall be reduced
to the Reduced Amount. The "Reduced Amount" shall be either (x) the largest
portion of the Payment that would result in no portion of the Payment being
subject to the Excise Tax or (y) the largest portion, up to and including the
total, of the Payment, whichever amount, after taking into account all
applicable federal, state and local employment taxes, income taxes, and the
Excise Tax (all computed at the highest applicable marginal rate), results in
the Eligible Employee's receipt, on an after-tax basis, of the greater amount of
the Payment notwithstanding that all or some portion of the Payment may be
subject to the Excise Tax. If a reduction in payments or benefits constituting
"parachute payments" is necessary so that the Payment equals the Reduced Amount,
reduction shall occur in the following order unless the Eligible Employee elects
in writing a different order (provided, however, that such election shall be
subject to Company approval if made on or after the date on which the event that
triggers the Payment occurs): reduction of cash payments; cancellation of
accelerated vesting of stock awards; reduction of employee benefits. In the
event that acceleration of vesting of stock award compensation is to be reduced,
such acceleration of vesting shall be cancelled in the reverse order of the date
of grant of the Eligible Employee's stock awards unless the Eligible Employee
elects in writing a different order for cancellation.

     The accounting firm engaged by the Company for general audit purposes as of
the day prior to the effective date of the Change in Control shall perform the
foregoing calculations.  If the accounting firm so engaged by the Company is
serving as accountant or auditor for the individual, entity or group effecting
the Change in Control, the Company shall appoint a nationally recognized
accounting firm to make the determinations required hereunder.  The Company
shall bear all expenses with respect to the determinations by such accounting
firm required to be made hereunder.

     The accounting firm engaged to make the determinations hereunder shall
provide its calculations, together with detailed supporting documentation, to
the Company and the Eligible Employee within fifteen (15) calendar days after
the date on which the Eligible Employee's right to a Payment is triggered (if
requested at that time by the Company or the Eligible Employee) or such other
time as requested by the Company or the Eligible Employee. If the accounting
firm

                                       5.
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determines that no Excise Tax is payable with respect to a Payment, either
before or after the application of the Reduced Amount, it shall furnish the
Company and the Eligible Employee with an opinion reasonably acceptable to
Executive that no Excise Tax will be imposed with respect to such Payment. Any
good faith determinations of the accounting firm made hereunder shall be final,
binding and conclusive upon the Company and the Eligible Employee.

Section 6.  Right To Interpret Plan; Amendment and Termination.

            (a)  Exclusive Discretion. The Plan Administrator shall have the
exclusive discretion and authority to establish rules, forms, and procedures for
the administration of the Plan and to construe and interpret the Plan and to
decide any and all questions of fact, interpretation, definition, computation or
administration arising in connection with the operation of the Plan, including,
but not limited to, the eligibility to participate in the Plan and amount of
benefits paid under the Plan. The rules, interpretations, computations and other
actions of the Plan Administrator shall be binding and conclusive on all
persons.

            (b)  Amendment or Termination. The Company reserves the right to
amend or terminate this Plan or the benefits provided hereunder at any time;
provided, however, that no such amendment or termination shall occur following a
Change in Control if such amendment or termination would affect the rights of
any persons who were employed by the Company prior to the Change in Control. Any
action amending or terminating the Plan shall be in writing and executed by the
chairman of the Compensation Committee of the Board of Directors of the Company.

Section 7.  Termination of Certain Employee Benefits.

     All non-health benefits (such as life insurance, disability and 401(k) plan
coverage) terminate as of the employee's termination date (except to the extent
that a conversion privilege may be available thereunder).

Section 8.  No Implied Employment Contract.

     The Plan shall not be deemed (i) to give any employee or other person any
right to be retained in the employ of the Company or (ii) to interfere with the
right of the Company to discharge any employee or other person at any time and
for any reason, which right is hereby reserved.

Section 9.  Legal Construction.

     This Plan is intended to be governed by and shall be construed in
accordance with the Employee Retirement Income Security Act of 1974 ("ERISA")
and, to the extent not preempted by ERISA, the laws of the State of California.

Section 10. Claims, Inquiries And Appeals.

            (a)  Applications for Benefits and Inquiries. Any application for
benefits, inquiries about the Plan or inquiries about present or future rights
under the Plan must be submitted to the Plan Administrator in writing. The Plan
Administrator is:

                                       6.
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                              Clarent Corporation
                             700 Chesapeake Drive
                            Redwood City, DA 94063

          (b)  Denial of Claims. In the event that any application for benefits
is denied in whole or in part, the Plan Administrator must notify the applicant,
in writing, of the denial of the application, and of the applicant's right to
review the denial. The written notice of denial will be set forth in a manner
designed to be understood by the employee and will include specific reasons for
the denial, specific references to the Plan provision upon which the denial is
based, a description of any information or material that the Plan Administrator
needs to complete the review and an explanation of the Plan's review procedure.

     This written notice will be given to the employee within ninety (90) days
after the Plan Administrator receives the application, unless special
circumstances require an extension of time, in which case, the Plan
Administrator has up to an additional ninety (90) days for processing the
application.  If an extension of time for processing is required, written notice
of the extension will be furnished to the applicant before the end of the
initial ninety (90) day period.

     This notice of extension will describe the special circumstances
necessitating the additional time and the date by which the Plan Administrator
is to render its decision on the application. If written notice of denial of the
application for benefits is not furnished within the specified time, the
application shall be deemed to be denied. The applicant will then be permitted
to appeal the denial in accordance with the Review Procedure described below.

          (c)  Request for a Review. Any person (or that person's authorized
representative) for whom an application for benefits is denied (or deemed
denied), in whole or in part, may appeal the denial by submitting a request for
a review to the Plan Administrator within sixty (60) days after the application
is denied (or deemed denied). The Plan Administrator will give the applicant (or
his or her representative) an opportunity to review pertinent documents in
preparing a request for a review. A request for a review shall be in writing and
shall be addressed to:

                              Clarent Corporation
                             700 Chesapeake Drive
                            Redwood City, DA 94063

A request for review must set forth all of the grounds on which it is based, all
facts in support of the request and any other matters that the applicant feels
are pertinent.  The Plan Administrator may require the applicant to submit
additional facts, documents or other material as it may find necessary or
appropriate in making its review.

          (d)  Decision on Review. The Plan Administrator will act on each
request for review within sixty (60) days after receipt of the request, unless
special circumstances require an extension of time (not to exceed an additional
sixty (60) days), for processing the request for a review. If an extension for
review is required, written notice of the extension will be furnished to the
applicant within the initial sixty (60) day period. The Plan Administrator will
give prompt, written notice of its decision to the applicant. In the event that
the Plan Administrator confirms the denial of the application for benefits in
whole or in part, the notice will outline, in a manner

                                       7.
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calculated to be understood by the applicant, the specific Plan provisions upon
which the decision is based. If written notice of the Plan Administrator's
decision is not given to the applicant within the time prescribed in this
Subsection (d), the application will be deemed denied on review.

            (e)  Rules and Procedures. The Plan Administrator will establish
rules and procedures, consistent with the Plan and with ERISA, as necessary and
appropriate in carrying out its responsibilities in reviewing benefit claims.
The Plan Administrator may require an applicant who wishes to submit additional
information in connection with an appeal from the denial (or deemed denial) of
benefits to do so at the applicant's own expense.

            (f)  Exhaustion of Remedies. No legal action for benefits under the
Plan may be brought until the claimant (i) has submitted a written application
for benefits in accordance with the procedures described by Section 10(a) above,
(ii) has been notified by the Plan Administrator that the application is denied
(or the application is deemed denied due to the Plan Administrator's failure to
act on it within the established time period), (iii) has filed a written request
for a review of the application in accordance with the appeal procedure
described in Section 10(c) above and (iv) has been notified in writing that the
Plan Administrator has denied the appeal (or the appeal is deemed to be denied
due to the Plan Administrator's failure to take any action on the claim within
the time prescribed by Section 10(d) above).

Section 11. Basis Of Payments To And From Plan.

     All benefits under the Plan shall be paid by the Company. The Plan shall be
unfunded, and benefits hereunder shall be paid only from the general assets of
the Company.

Section 12. Other Plan Information.

            (a)  Employer and Plan Identification Numbers. The Employer
Identification Number assigned to the Company (which is the "Plan Sponsor" as
that term is used in ERISA) by the Internal Revenue Service is 77-0433687. The
Plan Number assigned to the Plan by the Plan Sponsor pursuant to the
instructions of the Internal Revenue Service is 504.

            (b)  Ending Date for Plan's Fiscal Year. The date of the end of the
fiscal year for the purpose of maintaining the Plan's records is December 31.

            (c)  Agent for the Service of Legal Process. The agent for the
service of legal process with respect to the Plan is Clarent Corporation, 700
Chesapeake Drive, Redwood City, CA 94063.

            (d)  Plan Sponsor and Administrator. The "Plan Sponsor" and the
"Plan Administrator" of the Plan is Clarent Corporation, 700 Chesapeake Drive,
Redwood City, CA 94063. The Plan Sponsor's and Plan Administrator's telephone
number is (650) 306-7511. The Plan Administrator is the named fiduciary charged
with the responsibility for administering the Plan.

                                       8.
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Section 13.  Statement Of ERISA Rights.

     Participants in this Plan (which is a welfare benefit plan sponsored by
Clarent Corporation) are entitled to certain rights and protections under ERISA.
If you are an Eligible Employee, you are considered a participant in the Plan
and, under ERISA, you are entitled to:

          (a)  Examine, without charge, at the Plan Administrator's office and
at other specified locations, such as work sites, all Plan documents and copies
of all documents filed by the Plan with the U.S. Department of Labor, such as
detailed annual reports;

          (b)  Obtain copies of all Plan documents and Plan information upon
written request to the Plan Administrator. The Administrator may make a
reasonable charge for the copies; and

          (c)  Receive a summary of the Plan's annual financial report, in the
case of a plan that is required to file an annual financial report with the
Department of Labor. (Generally, all pension plans and welfare plans with one
hundred (100) or more participants must file these annual reports.)

     In addition to creating rights for Plan participants, ERISA imposes duties
upon the people responsible for the operation of the employee benefit plan.  The
people who operate the Plan, called "fiduciaries" of the Plan, have a duty to do
so prudently and in the interest of you and other Plan participants and
beneficiaries.

     No one, including your employer or any other person, may fire you or
otherwise discriminate against you in any way to prevent you from obtaining a
Plan benefit or exercising your rights under ERISA.  If your claim for a Plan
benefit is denied in whole or in part, you must receive a written explanation of
the reason for the denial.  You have the right to have the Plan review and
reconsider your claim.

     Under ERISA, there are steps you can take to enforce the above rights.  For
instance, if you request materials from the Plan and do not receive them within
thirty (30) days, you may file suit in a federal court.  In such a case, the
court may require the Plan Administrator to provide the materials and pay you up
to $110 a day until you receive the materials, unless the materials were not
sent because of reasons beyond the control of the Plan Administrator.  If you
have a claim for benefits that is denied or ignored, in whole or in part, you
may file suit in a state or federal court.  If it should happen that the Plan
fiduciaries misuse the Plan's money, or if you are discriminated against for
asserting your rights, you may seek assistance from the U.S. Department of
Labor, or you may file suit in a federal court.  The court will decide who
should pay court costs and legal fees.  If you are successful, the court may
order the person you have sued to pay these costs and fees.  If you lose, the
court may order you to pay these costs and fees, for example, if it finds your
claim is frivolous.

     If you have any questions about the Plan, you should contact the Plan
Administrator.  If you have any questions about this statement or about your
rights under ERISA, you should contact the nearest office of the Pension and
Welfare Benefits Administration, U.S. Department

                                      9.
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of Labor, listed in your telephone directory or the Division of Technical
Assistance and Inquiries, Pension and Welfare Benefits Administration, U.S.
Department of Labor, 200 Constitution Avenue N.W., Washington, D.C. 20210.

                                      10.
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                                   Exhibit A

                                    RELEASE
                       (Individual Termination over 40)

     Certain capitalized terms used in this Release are defined in the Change in
Control Severance Benefit Plan (the "Plan") which I have executed and of which
this Release is a part.

     I hereby confirm my obligations under the Company's proprietary information
and inventions agreement.

     I acknowledge that I have read and understand Section 1542 of the
California Civil Code which reads as follows: "A general release does not extend
to claims which the creditor does not know or suspect to exist in his favor at
the time of executing the release, which if known by him must have materially
affected his settlement with the debtor." I hereby expressly waive and
relinquish all rights and benefits under that section and any law of any
jurisdiction of similar effect with respect to my release of any claims I may
have against the Company.

     Except as otherwise set forth in this Release, I hereby release, acquit and
forever discharge the Company, its parents and subsidiaries, and their officers,
directors, agents, servants, employees, shareholders, successors, assigns and
affiliates, of and from any and all claims, liabilities, demands, causes of
action, costs, expenses, attorneys fees, damages, indemnities and obligations of
every kind and nature, in law, equity, or otherwise, known and unknown,
suspected and unsuspected, disclosed and undisclosed (other than any claim for
indemnification I may have as a result of any third party action against me
based on my employment with the Company), arising out of or in any way related
to agreements, events, acts or conduct at any time prior to the date I execute
this Release, including, but not limited to:  all such claims and demands
directly or indirectly arising out of or in any way connected with my employment
with the Company or the termination of that employment, including but not
limited to, claims of intentional and negligent infliction of emotional
distress, any and all tort claims for personal injury, claims or demands related
to salary, bonuses, commissions, stock, stock options, or any other ownership
interests in the Company, vacation pay, fringe benefits, expense reimbursements,
severance pay, or any other form of compensation; claims pursuant to any
federal, state or local law or cause of action including, but not limited to,
the federal Civil Rights Act of 1964, as amended; the federal Age Discrimination
in Employment Act of 1967, as amended ("ADEA"); the federal Employee Retirement
Income Security Act of 1974, as amended; the federal Americans with Disabilities
Act of 1990; the California Fair Employment and Housing Act, as amended; tort
law; contract law; wrongful discharge; discrimination; fraud; defamation;
emotional distress; and breach of the implied covenant of good faith and fair
dealing; provided, however, that nothing in this paragraph shall be construed in
any way to release the Company from its obligation to indemnify me pursuant to
the Company's indemnification obligation pursuant to agreement or applicable
law.

     I acknowledge that I am knowingly and voluntarily waiving and releasing any
rights I may have under ADEA.  I also acknowledge that the consideration given
under the Plan for the waiver and release in the preceding paragraph hereof is
in addition to anything of value to which I was already entitled.  I further
acknowledge that I have been advised by this writing, as

                                      1.
<PAGE>

required by the ADEA, that: (A) my waiver and release do not apply to any rights
or claims that may arise on or after the date I execute this Release; (B) I have
the right to consult with an attorney prior to executing this Release; (C) I
have twenty-one (21) days to consider this Release (although I may choose to
voluntarily execute this Release earlier); (D) I have seven (7) days following
my execution of this Release to revoke the Release; and (E) this Release shall
not be effective until the date upon which the revocation period has expired,
which shall be the eighth (8th) day after I execute this Release.

                                    Employee

                                    Name: _______________________________

                                    Date: _______________________________

                                      2.
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                                   Exhibit B

                                    RELEASE
                       (Individual Termination under 40)

     Certain capitalized terms used in this Release are defined in the Change in
Control Severance Benefit Plan (the "Plan") which I have executed and of which
this Release is a part.

     I hereby confirm my obligations under the Company's proprietary information
and inventions agreement.

     I acknowledge that I have read and understand Section 1542 of the
California Civil Code which reads as follows: "A general release does not extend
to claims which the creditor does not know or suspect to exist in his favor at
the time of executing the release, which if known by him must have materially
affected his settlement with the debtor." I hereby expressly waive and
relinquish all rights and benefits under that section and any law of any
jurisdiction of similar effect with respect to my release of any claims I may
have against the Company.

     Except as otherwise set forth in this Release, I hereby release, acquit and
forever discharge the Company, its parents and subsidiaries, and their officers,
directors, agents, servants, employees, shareholders, successors, assigns and
affiliates, of and from any and all claims, liabilities, demands, causes of
action, costs, expenses, attorneys fees, damages, indemnities and obligations of
every kind and nature, in law, equity, or otherwise, known and unknown,
suspected and unsuspected, disclosed and undisclosed (other than any claim for
indemnification I may have as a result of any third party action against me
based on my employment with the Company), arising out of or in any way related
to agreements, events, acts or conduct at any time prior to the date I execute
this Release, including, but not limited to:  all such claims and demands
directly or indirectly arising out of or in any way connected with my employment
with the Company or the termination of that employment, including but not
limited to, claims of intentional and negligent infliction of emotional
distress, any and all tort claims for personal injury, claims or demands related
to salary, bonuses, commissions, stock, stock options, or any other ownership
interests in the Company, vacation pay, fringe benefits, expense reimbursements,
severance pay, or any other form of compensation; claims pursuant to any
federal, state or local law or cause of action including, but not limited to,
the federal Civil Rights Act of 1964, as amended; the federal Age Discrimination
in Employment Act of 1967, as amended ("ADEA"); the federal Employee Retirement
Income Security Act of 1974, as amended; the federal Americans with Disabilities
Act of 1990; the California Fair Employment and Housing Act, as amended; tort
law; contract law; wrongful discharge; discrimination; fraud; defamation;
emotional distress; and breach of the implied covenant of good faith and fair
dealing; provided, however, that nothing in this paragraph shall be construed in
any way to release the Company from its obligation to indemnify me pursuant to
the Company's indemnification obligation pursuant to agreement or applicable
law.

                                    Employee

                                    Name: _______________________________

                                    Date: _______________________________

                                    1.
<PAGE>

                                   Exhibit C

                                    RELEASE
                              (Group Termination)

     Certain capitalized terms used in this Release are defined in the Change in
Control Severance Benefit Plan (the "Plan") which I have executed and of which
this Release is a part.

     I hereby confirm my obligations under the Company's proprietary information
and inventions agreement.

     I acknowledge that I have read and understand Section 1542 of the
California Civil Code which reads as follows: "A general release does not extend
to claims which the creditor does not know or suspect to exist in his favor at
the time of executing the release, which if known by him must have materially
affected his settlement with the debtor." I hereby expressly waive and
relinquish all rights and benefits under that section and any law of any
jurisdiction of similar effect with respect to my release of any claims I may
have against the Company.

     Except as otherwise set forth in this Release, I hereby release, acquit and
forever discharge the Company, its parents and subsidiaries, and their officers,
directors, agents, servants, employees, shareholders, successors, assigns and
affiliates, of and from any and all claims, liabilities, demands, causes of
action, costs, expenses, attorneys fees, damages, indemnities and obligations of
every kind and nature, in law, equity, or otherwise, known and unknown,
suspected and unsuspected, disclosed and undisclosed (other than any claim for
indemnification I may have as a result of any third party action against me
based on my employment with the Company), arising out of or in any way related
to agreements, events, acts or conduct at any time prior to the date I execute
this Release, including, but not limited to:  all such claims and demands
directly or indirectly arising out of or in any way connected with my employment
with the Company or the termination of that employment, including but not
limited to, claims of intentional and negligent infliction of emotional
distress, any and all tort claims for personal injury, claims or demands related
to salary, bonuses, commissions, stock, stock options, or any other ownership
interests in the Company, vacation pay, fringe benefits, expense reimbursements,
severance pay, or any other form of compensation; claims pursuant to any
federal, state or local law or cause of action including, but not limited to,
the federal Civil Rights Act of 1964, as amended; the federal Age Discrimination
in Employment Act of 1967, as amended ("ADEA"); the federal Employee Retirement
Income Security Act of 1974, as amended; the federal Americans with Disabilities
Act of 1990; the California Fair Employment and Housing Act, as amended; tort
law; contract law; wrongful discharge; discrimination; fraud; defamation;
emotional distress; and breach of the implied covenant of good faith and fair
dealing; provided, however, that nothing in this paragraph shall be construed in
any way to release the Company from its obligation to indemnify me pursuant to
the Company's indemnification obligation pursuant to agreement or applicable
law.

     I acknowledge that I am knowingly and voluntarily waiving and releasing any
rights I may have under ADEA.  I also acknowledge that the consideration given
under the Plan for the waiver and release in the preceding paragraph hereof is
in addition to anything of value to which I was already entitled.  I further
acknowledge that I have been advised by this writing, as

                                      1.
<PAGE>

required by the ADEA, that: (A) my waiver and release do not apply to any rights
or claims that may arise on or after the date I execute this Release; (B) I have
the right to consult with an attorney prior to executing this Release; (C) I
have forty-five (45) days to consider this Release (although I may choose to
voluntarily execute this Release earlier); (D) I have seven (7) days following
my execution of this Release to revoke the Release; (E) this Release shall not
be effective until the date upon which the revocation period has expired, which
shall be the eighth day (8th) after I execute this Release; and (F) I have
received with this Release a detailed list of the job titles and ages of all
employees who were terminated in this group termination and the ages of all
employees of the Company in the same job classification or organizational unit
who were not terminated.

                                    Employee

                                    Name:  ____________________________

                                    Date:  ____________________________

                                      2.<PAGE>

                                                                   Exhibit 10.28

                              CLARENT CORPORATION
                           STOCK OPTION GRANT NOTICE
       (Outside of the 1999 Amended and Restated Equity Incentive Plan)

Clarent Corporation (the "Company") hereby grants to Optionee a nonstatutory
stock option to purchase the number of shares of the Company's common stock (the
"Shares") set forth below. This option is not intended to qualify as an
"incentive stock option" within the meaning of Section 422 of the Internal
Revenue Code of 1986, as amended (the "Code"). This option is not subject to,
and is granted outside of the Company's 1999 Amended and Restated Equity
Incentive Plan. This option is granted as an inducement essential to the
Optionee's entering into an employment agreement with the Company. This option
is subject to all of the terms and conditions as set forth herein and in
Attachments I and II, which are incorporated herein in their entirety.

Optionee:                     Barry Forman
Date of Grant:                March 2, 2001
Shares Subject to Option:     600,000
Exercise Price Per Share:     $9.125
Expiration Date:              March 2, 2011

--------------------------------------------------------------------------------
                               Vesting Schedule
                               ----------------

25% of the shares subject to this option shall vest and become exercisable on
March 2, 2002. 1/48/th/ of the shares shall vest and become exercisable monthly
thereafter.
--------------------------------------------------------------------------------

Payment: Payment of the option exercise price may be made in cash, check or any
other method provided in the Stock Option Agreement.

Additional Terms/Acknowledgements: The undersigned Optionee acknowledges receipt
of, and understands and agrees to, this Grant Notice and the Stock Option
Agreement. Optionee further acknowledges that as of the Date of Grant, this
Grant Notice and the Stock Option Agreement set forth the entire understanding
between Optionee and the Company regarding the acquisition of Shares pursuant to
the option and supersedes all prior oral and written agreements on that subject
with the exception of the following agreements only:

Other Agreements:        Employment Agreement between Optionee and the Company
                         dated March 5, 2001.

CLARENT CORPORATION                          OPTIONEE

By: /s/ Jerry Chang                          /s/ Barry Forman
    ---------------                          ----------------
      Signature                              Barry Forman

Title: Chief Executive Officer
       -----------------------

Date:________________________________

                                       1.
<PAGE>

Attachment I:   Stock Option Agreement
Attachment II:  Notice of Exercise

                              CLARENT CORPORATION
                            STOCK OPTION AGREEMENT

     Pursuant to the Grant Notice and this Stock Option Agreement, Clarent
Corporation (the "Company") has granted you an option to purchase the number of
shares of the Company's common stock ("Shares") indicated in the Grant Notice at
the exercise price indicated in the Grant Notice.

     This option is granted in connection with, and as inducement essential to,
your entering an employment agreement with the Company, and as a compensatory
benefit plan in connection with your employment.

     The details of this option are as follows:

     1.   Vesting. This option will vest as provided in the Grant Notice,
subject to certain acceleration, continuation or termination of vesting more
specifically provided for in that certain Employment Agreement, dated March 5,
2001, by and between you and the Company (the "Employment Agreement").

     2.   Method of Payment. Payment of the exercise price by cash or check is
due in full upon exercise of all or any part of this option, provided that you
may elect, to the extent permitted by applicable law and the Grant Notice, to
make payment of the exercise price under the following alternatives, (i)
provided that at the time of exercise the Company's stock is publicly traded and
quoted regularly in the Wall Street Journal: payment by delivery of already-
owned Shares, held for the period required to avoid a charge to the Company's
reported earnings, and owned free and clear of any liens, claims, encumbrances
or security interests, which Shares shall be valued at their fair market value
on the date of exercise, or (ii) payment pursuant to a program developed under
Regulation T as promulgated by the Federal Reserve Board which, prior to the
issuance of Shares, results in either the receipt of cash (or check) by the
Company or the receipt of irrevocable instructions to pay the aggregate exercise
price to the Company from the sales proceeds.

     3.   Whole Shares. This option may be exercised only for whole Shares.

     4.   Term. The term of this option commences on the Date of Grant and
expires upon the earliest of:

          (a)  the tenth (10th) anniversary of the Date of Grant;

          (b)  eighteen (18) months after your death, if you die while an
employee, director or consultant of the Company or if you die within three (3)
months after termination of your continuous service;

                                       2.
<PAGE>

          (c)  twelve (12) months after the termination of your continuous
service due to your permanent and total disability (within the meaning of
Section 22(e)(3) of the Internal Revenue Code of 1986, as amended); or

          (d)  three (3) months after the termination of your continuous service
for any reason other th an death or disability.

     5.   Exercise.

          (a)  You may exercise the vested portion of this option during its
term by delivering a notice of exercise (in a form designated by the Company)
together with the exercise price to the Secretary of the Company, or to such
other person as the Company may designate, during regular business hours,
together with such additional documents as the Company may then require.

          (b)  By exercising this option you agree that:

               (i)   As a condition to any exercise of this option, the Company
may require you to enter into an arrangement providing for the payment by you to
the Company of any tax withholding obligation of the Company arising by reason
of (1) the exercise of this option; (2) the lapse of any substantial risk of
forfeiture to which the Shares are subject at the time of exercise; or (3) the
disposition of Shares acquired upon such exercise.

               (ii)  Regardless of whether the offer and sale of Shares subject
to this option have been registered under the Securities Act of 1933, as amended
(the "1933 Act") or have been registered or qualified under the securities laws
of any state, the Company may impose restrictions upon the sale, pledge or other
transfer of such Shares (including the placement of appropriate legends on stock
certificates) if in the judgment of the Company and its counsel such
restrictions are necessary or desirable in order to achieve compliance with the
provisions of the 1933 Act, the securities laws of any state or any other law.

     6.   Transferability. This option is not transferable, except by will or by
the laws of descent and distribution, and is exercisable during your lifetime
only by you.

     7.   Capitalization Adjustments. If any change is made in the Shares
subject to this option without the receipt of consideration by the Company
(through merger, consolidation, reorganization, recapitalization,
reincorporation, stock dividend, dividend in property other than cash, stock
split, liquidating dividend, combination of shares, exchange of shares, change
in corporate structure or other transaction not involving the receipt of
consideration by the Company), the option will be appropriately adjusted in the
class(es) and number of shares and price per share of stock subject to such
option. Such adjustments shall be made by the Board of Directors of the Company,
determination of which shall be final, binding and conclusive. (The conversion
of any convertible securities of the Company shall not be treated as a
transaction "without receipt of consideration" by the Company.)

     8.   Change of Control.

                                       3.
<PAGE>

     (a)  Dissolution or Liquidation. In the event of a dissolution or
liquidation of the Company, this option shall be terminated if not exercised
prior to such event.

     (b)  Asset Sale, Merger, Consolidation or Reverse Merger. In the event of
(1) a sale of all or substantially all of the assets of the Company, (2) a
merger or consolidation in which the Company is not the surviving corporation or
(3) a reverse merger in which the Company is the surviving corporation but the
shares of Common Stock outstanding immediately preceding the merger are
converted by virtue of the merger into other property, whether in the form of
securities, cash or otherwise, then any surviving corporation or acquiring
corporation shall assume or continue this option or shall substitute a similar
option. In the event any surviving corporation or acquiring corporation refuses
to assume or continue this option or to substitute a similar option for this
option, then if your continuous service as an employee, consultant or director
has not terminated, the vesting of this option (and, if applicable, the time
during which this option may be exercised) shall be accelerated in full prior to
such event, and this option shall terminate if not exercised at or prior to such
event. In addition, the vesting of this option (and, if applicable, the time
during which this option may be exercised) may be subject to acceleration
pursuant to the terms of your Employment Agreement.

     (c)  Securities Acquisition. In the event of an acquisition by any person,
entity or group within the meaning of Section 13(d) or 14(d) of the Exchange Act
of 1934, as amended (the "Exchange Act"), or any comparable successor provisions
(excluding any employee benefit plan, or related trust, sponsored or maintained
by the Company or an affiliate) of the beneficial ownership (within the meaning
of Rule 13d-3 promulgated under the Exchange Act, or comparable successor rule)
of securities of the Company representing at least fifty percent (50%) of the
combined voting power entitled to vote in the election of directors, then if
your continuous service as an employee, consultant or director has not
terminated, the vesting of this option (and, if applicable, the time during
which this option may be exercised) shall be accelerated in full.

     9.   Purchase for Investment; Rights of Holder on Subsequent Registration.
Unless the Shares to be issued upon exercise of your option have been
effectively registered under the 1933 Act, the Company shall be under no
obligation to issue any Shares covered by this option, whether such exercise is
in whole or in part, unless you give a written representation and undertaking to
the Company which is satisfactory in form and scope to counsel for the Company
and upon which, in the opinion of such counsel, the Company may reasonably rely,
that you are acquiring the Shares issued to you pursuant to such exercise of the
option for your own account as an investment and not with a view to, or for sale
in connection with, the distribution of any such Shares, and that you will make
no transfer of the same except in compliance with any rules and regulations in
force at the time of such transfer under the 1933 Act, or any other applicable
law, and that if Shares are issued without such registration a legend to this
effect may be endorsed on the securities so issued. In the event that the
Company shall, nevertheless, deem it necessary or desirable to register under
the 1933 Act or other applicable statutes any Shares with respect to which this
option shall have been exercised, or to qualify any such Shares for exemption
from the 1933 Act or other applicable statutes, then the Company shall take such
action at its own expense and may require from you such information in writing
for use in any registration statement, prospectus, preliminary prospectus or
offering circular as is reasonably necessary for such purpose and may require
reasonable indemnity to the Company and its officers and

                                       4.
<PAGE>

directors from you against all losses, claims, damages and liabilities arising
from such use of the information so furnished and caused by any untrue statement
of any material fact required to be stated therein or necessary to make the
statement therein not misleading in light of the circumstances under which they
were made.

     10.  Option Not an Employment Contract. This option is not an employment
contract, and nothing in this option including without limitation the reference
to your Employment Agreement shall be deemed to create in any way whatsoever any
obligation on your part to continue in the employ of the Company, or of the
Company to continue your employment with the Company. The Company may terminate
your employment at any time, for any reason or no reason, with or without cause.

     11.  Notices. Any notices provided for in this option shall be given in
writing and shall be deemed effectively given upon receipt or, in the case of
notices delivered by the Company to you, (i) five (5) days after deposit in the
United States mail, postage prepaid, addressed to you at the last address you
provided to the Company or (ii) immediately upon confirmation of successful
transmission via facsimile or electronic mail.

     12.  Choice of Law. This option shall be governed by, and construed in
accordance with the laws of the State of California, as such laws are applied to
contracts entered into and performed in such State.

     13.  Governing Authority. This option is subject to all interpretations,
amendments, rules and regulations which may from time to time be promulgated and
adopted by the Company. This authority shall be exercised by the Board, or by a
committee of one or more members of the Board in the event that the Board
delegates its authority to a committee. The Board, in the exercise of this
authority, may correct any defect, omission or inconsistency in this option in a
manner and to the extent the Board shall deem necessary or desirable to make
this option fully effective. References to the Board also include any committee
appointed by the Board to administer and interpret this option. Any
interpretations, amendments, rules and regulations promulgated by the Board
shall be final and binding upon the Company and its successors in interest as
well as you and your heirs, assigns, and other successors in interest.

Dated the 2/nd/ day of March, 2001.

Very truly yours,

Clarent Corporation

By: /s/ Jerry Chang
    ---------------
        Duly authorized on behalf
        of the Board of Directors

                                       5.
<PAGE>

                              NOTICE OF EXERCISE

Clarent Corporation
700 Chesapeake Drive
Redwood City, CA 94063                        Date of Exercise: ________________

Ladies and Gentlemen:

     This constitutes notice under my nonstatutory stock option that I elect to
purchase the number of shares for the price set forth below.

     Stock option dated:                          March 2, 2001
                                                  -------------

     Number of shares as
     to which option is
     exercised:                                   _____________

     Certificate to be
     issued in name of:                           _____________

     Total exercise price:                        $____________

     Cash payment (or check) delivered herewith:  $____________

     Value of ______ shares of
     Clarent Corporation
     common stock delivered herewith/1/:          $____________

     By this exercise, I agree to provide such additional documents as you may
reasonably require. I understand that my right to receive the shares otherwise
issuable to me upon the exercise of the option is contingent upon my
satisfaction of these requirements.

     I hereby make the following statements with respect to the shares of common
stock (the "Shares"), which are being acquired by me for my own account upon
this exercise of the option as set forth above:

____________
/1/  Shares must meet the public trading requirements set forth in the option.
Shares must be valued in accordance with the terms of the option being
exercised, must have been owned for the minimum period required in the option,
and must be owned free and clear of any liens, claims, encumbrances or security
interests. Certificates must be endorsed or accompanied by an executed
assignment separate from certificate.

                                      1.
<PAGE>

     I acknowledge and agree that as a condition to this exercise of the option,
the Company may require me to enter an arrangement providing for the payment by
me to the Company of any tax withholding obligation of the Company arising by
reason of (1) the exercise of the option; (2) the lapse of any substantial risk
of forfeiture to which the Shares are subject at the time of exercise; or (3)
the disposition of Shares acquired upon such exercise.

     I further acknowledge and agree that regardless of whether the offer and
sale of Shares subject to the option have been registered under the Securities
Act of 1933, as amended (the "1933 Act") or have been registered or qualified
under the securities laws of any state, the Company may impose restrictions upon
the sale, pledge or other transfer of the Shares (including the placement of
appropriate legends on stock certificates) if in the judgment of the Company and
its counsel such restrictions are necessary or desirable in order to achieve
compliance with the provisions of the 1933 Act, the securities laws of any state
or any other law.

                                             Very truly yours,

                                             ___________________________________

                                      2.

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