AMENDED 2000 STOCK OPTION AND INCENTIVE PLAN AS AMENDED



 EXHIBIT 4.3 
  
 AVICI SYSTEMS INC. 
  
 AMENDED 2000 STOCK OPTION AND INCENTIVE
PLAN 
  

	1.	Purpose and Eligibility 

  
 The purpose of this 2000 Stock Option and Incentive Plan (the “Plan”) of Avici Systems Inc. (the “Company”) is to
provide stock options and other equity interests in the Company (each an “Award”) to employees, officers, directors, consultants and advisors of the Company and its Subsidiaries, all of whom are eligible to receive Awards under the
Plan. Any person to whom an Award has been granted under the Plan is called a “Participant”. Additional definitions are contained in Section 8. 
  


	2.	Administration 

  
 a. Administration by Board of Directors. The Plan will be administered by the Board of Directors of the Company (the “Board”). The
Board, in its sole discretion, shall have the authority to grant and amend Awards, to adopt, amend and repeal rules relating to the Plan and to interpret and correct the provisions of the Plan and any Award. All decisions by the Board shall be final
and binding on all interested persons. Neither the Company nor any member of the Board shall be liable for any action or determination relating to the Plan. 
  
 b. Appointment of Committees. To the extent permitted by applicable law, the Board may delegate any or all of its powers under the Plan to one or
more committees or subcommittees of the Board (a “Committee”). All references in the Plan to the “Board” shall mean such Committee or the Board. 
  
 c. Delegation to Executive Officers. To the extent permitted by applicable law, the Board may delegate to one or more
executive officers of the Company the power to grant Awards and exercise such other powers under the Plan as the Board may determine, provided that the Board shall fix the maximum number of Awards to be granted and the maximum number of
shares issuable to any one Participant pursuant to Awards granted by such executive officers. 
  

	3.	Stock Available for Awards 

  
 a. Number of Shares. Subject to adjustment under Section 3(c), the aggregate number of shares of Common Stock of the Company (the “Common
Stock”) that may be issued pursuant to the Plan is equal to the number of shares of Common Stock authorized but not issued under the 1997 Stock Incentive Plan of the Company, as amended, on or before the date of the initial public offering of
the Company’s Common Stock plus (i) the 1,250,000 additional shares authorized for issuance under the Plan pursuant to the amendment of the Plan in 2001 and (ii) the 1,250,000 additional shares authorized for issuance under the Plan pursuant to
the amendment of the Plan in 2004 (collectively the “Available Shares”). If any Award expires, or is terminated, surrendered or forfeited, in whole or in part, the unissued Common Stock covered by such Award shall again be available
for the grant of Awards under the Plan. If shares of Common Stock issued pursuant to the Plan are repurchased by, or are surrendered or forfeited to, the Company at 

  









 
no more than cost, such shares of Common Stock shall again be available for the grant of Awards under the Plan; provided, however, that the cumulative number
of such shares that may be so reissued under the Plan will not exceed the Available Shares. Shares issued under the Plan may consist in whole or in part of authorized but unissued shares or treasury shares. 
  
 b. Per-Participant Limit. Subject to adjustment under Section 3(c), no
Participant may be granted Awards during any one fiscal year to purchase more than 500,000 shares of Common Stock. 
  
 c. Adjustment to Common Stock. In the event of any stock split, stock dividend, extraordinary cash dividend, recapitalization, reorganization,
merger, consolidation, combination, exchange of shares, liquidation, spin-off, split-up, or other similar change in capitalization or event, (i) the number and class of securities available for Awards under the Plan and the per-Participant share
limit, (ii) the number and class of securities, vesting schedule and exercise price per share subject to each outstanding Option, (iii) the repurchase price per security subject to repurchase, and (iv) the terms of each other outstanding stock-based
Award shall be adjusted by the Company (or substituted Awards may be made) to the extent the Board shall determine, in good faith, that such an adjustment (or substitution) is appropriate. If Section 7(e)(i) applies for any event, this Section 3(c)
shall not be applicable. 
  

	4.	Stock Options 

  
 a. General. The Board may grant options to purchase Common Stock (each, an “Option”) and determine the number of shares of Common
Stock to be covered by each Option, the exercise price of each Option and the conditions and limitations applicable to the exercise of each Option and the Common Stock issued upon the exercise of each Option, including vesting provisions, repurchase
provisions and restrictions relating to applicable federal or state securities laws, as it considers advisable. 
  
 b. Incentive Stock Options. An Option that the Board intends to be an “incentive stock option“ as defined in Section 422 of the Code (an
“Incentive Stock Option”) shall be granted only to employees of the Company and shall be subject to and shall be construed consistently with the requirements of Section 422 of the Code. The Board and the Company shall have no
liability if an Option or any part thereof that is intended to be an Incentive Stock Option does not qualify as such. An Option or any part thereof that does not qualify as an Incentive Stock Option is referred to herein as a “Nonstatutory
Stock Option.” 
  
 c. Exercise Price. The Board
shall establish the exercise price (or determine the method by which the exercise price shall be determined) at the time each Option is granted and specify it in the applicable option agreement. 
  
 d. Duration of Options. Each Option shall be exercisable at such times
and subject to such terms and conditions as the Board may specify in the applicable option agreement. 
  

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 e. Exercise of Option. Options may be exercised only by delivery to the Company of a written
notice of exercise signed by the proper person together with payment in full as specified in Section 4(f) for the number of shares for which the Option is exercised. 
  
 f. Payment Upon Exercise. Common Stock purchased upon the exercise of an Option shall be paid for by one or any
combination of the following forms of payment: 
  
 (i) by check payable to the order of the Company; 
  
 (ii) except as otherwise explicitly provided in the applicable option agreement, and only if the Common Stock is then publicly traded, delivery of an irrevocable and unconditional undertaking by a creditworthy broker
to deliver promptly to the Company sufficient funds to pay the exercise price, or delivery by the Participant to the Company of a copy of irrevocable and unconditional instructions to a creditworthy broker to deliver promptly to the Company cash or
a check sufficient to pay the exercise price; or 
  
 (iii) to the extent explicitly provided in the applicable option agreement, by (x) delivery of shares of Common Stock owned by the Participant valued at fair market value (as determined by the Board or as determined pursuant to the
applicable option agreement), (y) delivery of a promissory note of the Participant to the Company (and delivery to the Company by the Participant of a check in an amount equal to the par value of the shares purchased), or (z) payment of such other
lawful consideration as the Board may determine. 
  

	5.	Restricted Stock 

  
 a. Grants. The Board may grant Awards entitling recipients to acquire shares of Common Stock, subject to (i) delivery to the Company by the
Participant of a check or payment of such other lawful consideration as the Board may determine in an amount at least equal to the par value of the shares purchased, and (ii) the right of the Company to repurchase all or part of such shares at their
issue price or other stated or formula price from the Participant in the event that conditions specified by the Board in the applicable Award are not satisfied prior to the end of the applicable restriction period or periods established by the Board
for such Award (each, a “Restricted Stock Award”). 
  
 b. Terms and Conditions. The Board shall determine the terms and conditions of any such Restricted Stock Award. Any stock certificates issued in respect of a Restricted Stock Award shall be registered in the name of the Participant
and, unless otherwise determined by the Board, deposited by the Participant, together with a stock power endorsed in blank, with the Company (or its designee). After the expiration of the applicable restriction periods, the Company (or such
designee) shall deliver the certificates no longer subject to such restrictions to the Participant or, if the Participant has died, to the beneficiary designated by a Participant, in a manner determined by the Board, to receive amounts due or
exercise rights of the Participant in the event of the Participant’s death (the “Designated Beneficiary”). In the absence of an effective designation by a Participant, Designated Beneficiary shall mean the Participant’s
estate. Each Restricted Stock Award granted pursuant to the Plan shall be subject to forfeiture if, in the discretion of the Board, the recipient of such award has not, within a reasonable period of time 

  

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following the grant of such award, executed any instrument required by the Board to be executed in connection with such award. 
  

	6.	Other Stock-Based Awards 

  
 The Board shall have the right to grant other Awards based upon the Common Stock having such terms and conditions as the Board may determine, including,
without limitation, the grant of shares based upon certain conditions, the grant of securities convertible into Common Stock and the grant of stock appreciation rights, phantom stock awards or stock units. 
  

	7.	General Provisions Applicable to Awards 

  
 a. Transferability of Awards. Except as the Board may otherwise determine or provide in an Award, Awards shall not be sold, assigned, transferred,
pledged or otherwise encumbered by the person to whom they are granted, either voluntarily or by operation of law, except by will or the laws of descent and distribution, and, during the life of the Participant, shall be exercisable only by the
Participant. References to a Participant, to the extent relevant in the context, shall include references to authorized transferees. 
  
 b. Documentation. Each Award under the Plan shall be evidenced by a written instrument in such form as the Board shall determine or as executed by
an officer of the Company pursuant to authority delegated by the Board. Each Award may contain terms and conditions in addition to those set forth in the Plan provided that such terms and conditions do not contravene the provisions of the
Plan. 
  
 c. Board Discretion. The terms of each type of
Award need not be identical, and the Board need not treat Participants uniformly. 
  
 d. Termination of Status. The Board shall determine the effect on an Award of the disability, death, retirement, authorized leave of absence or other change in the employment or other status of a Participant
and the extent to which, and the period during which, the Participant, or the Participant’s legal representative, conservator, guardian or Designated Beneficiary, may exercise rights under the Award. 
  
 e. Acquisition of the Company 
  
 (i) Consequences of an Acquisition. 
  
 (A) Upon the consummation of an Acquisition, the Board shall
take any one or more of the following actions with respect to then outstanding Awards: (a) provide that outstanding Options shall be assumed, or equivalent Options shall be substituted, by the acquiring or succeeding corporation (or an affiliate
thereof), provided that any such Options substituted for Incentive Stock Options shall satisfy, in the determination of the Board, the requirements of Section 424(a) of the Code; (b) upon written notice to the Participants, provide that all or a
portion of then unexercised Options will become exercisable in full or in part as of a specified time (the “Acceleration Time”) prior to the Acquisition and will terminate immediately 

  

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prior to the consummation of such Acquisition, except to the extent exercised by the Participants between the Acceleration Time and the consummation of such
Acquisition; (c) in the event of an Acquisition under the terms of which holders of Common Stock will receive upon consummation thereof a cash payment for each share of Common Stock surrendered pursuant to such Acquisition (the “Acquisition
Price”), provide that all outstanding Options shall terminate upon consummation of such Acquisition and each Participant shall receive, in exchange therefor, a cash payment equal to the amount (if any) by which (x) the Acquisition Price
multiplied by the number of shares of Common Stock subject to such outstanding Options (whether or not then exercisable), exceeds (y) the aggregate exercise price of such Options; (d) provide that all or any portion of the Restricted Stock Awards
then outstanding shall become free of all or certain restrictions prior to the consummation of the Acquisition; and (e) provide that any other stock-based Awards outstanding (x) shall become exercisable, realizable or vested in full or in part, or
shall be free of all or certain conditions or restrictions, as applicable to each such Award, prior to the consummation of the Acquisition, or (y), if applicable, shall be assumed, or equivalent Awards shall be substituted, by the acquiring or
succeeding corporation (or an affiliate thereof); provided that in no event shall the Board accelerate the vesting of any Option, Restricted Stock Award or other Award by a period of more than one year. 
  
 (B) Acquisition Defined. An
“Acquisition” shall mean: (x) the sale of the Company by merger in which the shareholders of the Company in their capacity as such no longer own a majority of the outstanding equity securities of the Company (or its successor); or
(y) any sale of all or substantially all of the assets or capital stock of the Company (other than in a spin-off or similar transaction) or (z) any other acquisition of the business of the Company, as determined by the Board. 
  
 (ii) Assumption of Options Upon Certain Events. In
connection with a merger or consolidation of an entity with the Company or the acquisition by the Company of property or stock of an entity, the Board may grant Awards under the Plan in substitution for stock and stock-based awards issued by such
entity or an affiliate thereof. The substitute Awards shall be granted on such terms and conditions as the Board considers appropriate in the circumstances. 
  
 (iii) Pooling-of Interests-Accounting. If the Company proposes to engage in an Acquisition intended to be accounted for as a
pooling-of-interests, and in the event that the provisions of this Plan or of any Award hereunder, or any actions of the Board taken in connection with such Acquisition, are determined by the Company’s or the acquiring company’s
independent public accountants to cause such Acquisition to fail to be accounted for as a pooling-of-interests, then such provisions or actions shall be amended or rescinded by the Board, without the consent of any Participant, to be consistent with
pooling-of-interests accounting treatment for such Acquisition. 
  
 (iv) Parachute Awards. Notwithstanding the provisions of Section 7(e)(i)(A), if, in connection with an Acquisition described therein, a tax under Section 4999 of the Code would be imposed on the Participant
(after taking into account the exceptions set forth in Sections 280G(b)(4) and 280G(b)(5) of the Code), then the number of Awards which shall become exercisable, realizable or vested as provided in such section shall be reduced (or delayed), to the
minimum extent necessary, so that no such tax would be imposed on the 

  

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Participant (the Awards not becoming so accelerated, realizable or vested, the “Parachute Awards”); provided, however, that if the
“aggregate present value” of the Parachute Awards would exceed the tax that, but for this sentence, would be imposed on the Participant under Section 4999 of the Code in connection with the Acquisition, then the Awards shall become
immediately exercisable, realizable and vested without regard to the provisions of this sentence. For purposes of the preceding sentence, the “aggregate present value” of an Award shall be calculated on an after-tax basis (other than taxes
imposed by Section 4999 of the Code) and shall be based on economic principles rather than the principles set forth under Section 280G of the Code and the regulations promulgated thereunder. All determinations required to be made under this Section
7(e)(iv) shall be made by the Company. 
  
 f. Withholding.
Each Participant shall pay to the Company, or make provisions satisfactory to the Company for payment of, any taxes required by law to be withheld in connection with Awards to such Participant no later than the date of the event creating the tax
liability. The Board may allow Participants to satisfy such tax obligations in whole or in part by transferring shares of Common Stock, including shares retained from the Award creating the tax obligation, valued at their fair market value (as
determined by the Board or as determined pursuant to the applicable option agreement). The Company may, to the extent permitted by law, deduct any such tax obligations from any payment of any kind otherwise due to a Participant. 
  
 g. Amendment of Awards. The Board may amend, modify or terminate any
outstanding Award including, but not limited to, substituting therefor another Award of the same or a different type, changing the date of exercise or realization, and converting an Incentive Stock Option to a Nonstatutory Stock Option, provided
that, except as otherwise provided in Section 7(e)(iii), the Participant’s consent to such action shall be required unless the Board determines that the action, taking into account any related action, would not materially and adversely
affect the Participant. 
  
 h. Conditions on Delivery of
Stock. The Company will not be obligated to deliver any shares of Common Stock pursuant to the Plan or to remove restrictions from shares previously delivered under the Plan until (i) all conditions of the Award have been met or removed to the
satisfaction of the Company, (ii) in the opinion of the Company’s counsel, all other legal matters in connection with the issuance and delivery of such shares have been satisfied, including any applicable securities laws and any applicable
stock exchange or stock market rules and regulations, and (iii) the Participant has executed and delivered to the Company such representations or agreements as the Company may consider appropriate to satisfy the requirements of any applicable laws,
rules or regulations. 
  
 i. Acceleration. The Board may at
any time provide that any Options shall become immediately exercisable in full or in part, that any Restricted Stock Awards shall be free of some or all restrictions, or that any other stock-based Awards may become exercisable in full or in part or
free of some or all restrictions or conditions, or otherwise realizable in full or in part, as the case may be, despite the fact that the foregoing actions may (i) cause the application of Sections 280G and 4999 of the Code if a change in control of
the Company occurs, or (ii) disqualify all or part of the Option as an Incentive Stock Option. 
  

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	8.	Miscellaneous 

  
 a. Definitions. 
  
 (i) “Company,” for purposes of eligibility under the Plan, shall include any present or future subsidiary corporations of
Avici Systems Inc., as defined in Section 424(f) of the Code (a “Subsidiary”), and any present or future parent corporation of Avici Systems Inc., as defined in Section 424(e) of the Code. For purposes of Awards other than Incentive
Stock Options, the term “Company” shall include any other business venture in which the Company has a direct or indirect significant interest, as determined by the Board in its sole discretion. 
  
 (ii) “Code” means the Internal Revenue Code
of 1986, as amended, and any regulations promulgated thereunder. 
  
 (iii) “employee” for purposes of eligibility under the Plan (but not for purposes of Section 4(b)) shall include a person to whom an offer of employment has been extended by the Company. 

 
 b. No Right To Employment or Other Status. No person shall have any
claim or right to be granted an Award, and the grant of an Award shall not be construed as giving a Participant the right to continued employment or any other relationship with the Company. The Company expressly reserves the right at any time to
dismiss or otherwise terminate its relationship with a Participant free from any liability or claim under the Plan. 
  
 c. No Rights As Stockholder. Subject to the provisions of the applicable Award, no Participant or Designated Beneficiary shall have any rights as a
stockholder with respect to any shares of Common Stock to be distributed with respect to an Award until becoming the record holder thereof. 
  
 d. Effective Date and Term of Plan. The Plan shall become effective on the date on which it is adopted by the Board. No Awards shall be granted
under the Plan after the completion of ten years from the date on which the Plan was adopted by the Board, but Awards previously granted may extend beyond that date. 
  
 e. Amendment of Plan. The Board may amend, suspend or terminate the Plan or any portion thereof at any time.

  
 f. Governing Law. The provisions of the Plan and all
Awards made hereunder shall be governed by and interpreted in accordance with the laws of Delaware, without regard to any applicable conflicts of law. 
  

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