EX-10.6



 Exhibit 10.6 

CASA SYSTEMS, INC. 
 2011 STOCK
INCENTIVE PLAN 
 1. Purpose 
 The
purpose of this 2011 Stock Incentive Plan (the “Plan”) of Casa Systems, Inc., a Delaware corporation (the “Company”), is to advance the interests of the Company’s stockholders by enhancing the
Company’s ability to attract, retain and motivate persons who are expected to make important contributions to the Company and by providing such persons with equity ownership opportunities and performance-based incentives that are intended to
better align the interests of such persons with those of the Company’s stockholders. Except where the context otherwise requires, the term “Company” shall include any of the Company’s present or future parent or
subsidiary corporations as defined in Sections 424(e) or (f) of the Internal Revenue Code of 1986, as amended, and any regulations thereunder (the “Code”) and any other business venture (including, without limitation,
joint venture or limited liability company) in which the Company has a controlling interest, as determined by the Board of Directors of the Company (the “Board”); provided, however, that such other business
ventures shall be limited to entities that, where required by Section 409A of the Code, are eligible issuers of service recipient stock (as defined in Treas. Reg. Section 1.409A-1(b)(5)(iii)(E), or
applicable successor regulation). 
 2. Eligibility 

All of the Company’s employees, officers and directors, as well as consultants and advisors to the Company (as such terms are defined and
interpreted for purposes of Rule 701 under the Securities Act of 1933, as amended (the “Securities Act”) (or any successor rule)) are eligible to be granted Awards under the Plan. Each person who is granted an Award
under the Plan is deemed a “Participant.” “Award” means Options (as defined in Section 5), SARs (as defined in Section 6), Restricted Stock (as defined in Section 7), Restricted Stock
Units (as defined in Section 7) and Other Stock-Based Awards (as defined in Section 8). 
 3. Administration and Delegation 

(a) Administration by Board of Directors. The Plan will be administered by the Board. The Board shall have authority to grant Awards
and to adopt, amend and repeal such administrative rules, guidelines and practices relating to the Plan as it shall deem advisable. The Board may construe and interpret the terms of the Plan and any Award agreements entered into under the Plan. The
Board may correct any defect, supply any omission or reconcile any inconsistency in the Plan or any Award in the manner and to the extent it shall deem expedient to carry the Plan into effect and it shall be the sole and final judge of such
expediency. All decisions by the Board shall be made in the Board’s sole discretion and shall be final and binding on all persons having or claiming any interest in the Plan or in any Award. 

(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 the Board or a Committee of the Board or the officers referred to in
Section 3(c) to the extent that the Board’s powers or authority under the Plan have been delegated to such Committee or officers. 

  
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 (c) Delegation to Officers. To the extent permitted by applicable law, the Board may
delegate to one or more officers of the Company the power to grant Options and other Awards that constitute rights under Delaware law (subject to any limitations under the Plan) to employees or officers of the Company and to exercise such other
powers under the Plan as the Board may determine, provided that the Board shall fix the terms of such Awards to be granted by such officers (including the exercise price of such Awards, which may include a formula by which the exercise price
will be determined) and the maximum number of shares subject to such Awards that the officers may grant; provided further, however, that no officer shall be authorized to grant such Awards to any “executive officer” of the Company
(as defined by Rule 3b-7 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”)) or to any “officer” of the Company (as defined by Rule 16a-1 under the Exchange Act). The Board may not delegate authority under this Section 3(c) to grant Restricted Stock, unless Delaware law then permits such delegation. 

4. Stock Available for Awards
 (a)
Number of Shares. Subject to adjustment under Section 9, Awards may be made under the Plan for up to a number of shares of common stock, $0.001 par value per share, of the Company (the “Common Stock”), equal to
the sum of (a) 298,371, plus (b) such additional number of shares of Common Stock as is equal to the sum of (x) the number of shares of Common Stock reserved for issuance under the Company’s 2003 Stock Incentive Plan, as amended
(the “2003 Plan”) that remain available for issuance under the 2003 Plan as of the time immediately before termination of the 2003 Plan and (y) the number of shares of Common Stock subject to awards granted under the 2003 Plan which
awards expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right (subject, however, in the case of Incentive Stock Options (as
hereinafter defined) to any limitations of the Code); provided, however, that the maximum number of shares of Common Stock available for issuance under the Plan (including any shares becoming available by reason of clause (y)) shall be 935,871.
Any or all of the Awards described in the preceding sentence may be in the form of Incentive Stock Options (as defined in Section 5(b)). If any Award expires or is terminated, surrendered or canceled without having been fully exercised, is
forfeited in whole or in part (including as the result of shares of Common Stock subject to such Award being repurchased by the Company at the original issuance price pursuant to a contractual repurchase right), or results in any Common Stock not
being issued, the unused Common Stock covered by such Award shall again be available for the grant of Awards under the Plan. Further, shares of Common Stock tendered to the Company by a Participant to exercise an Award shall be added to the number
of shares of Common Stock available for the grant of Awards under the Plan. However, in the case of Incentive Stock Options, the two immediately preceding sentences shall be subject to any limitations under the Code. Shares issued under the Plan may
consist in whole or in part of authorized but unissued shares or treasury shares. 

  
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 (b) Substitute Awards. 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 in substitution for any options or other stock or stock-based awards granted by such entity or an affiliate thereof. Substitute Awards may be
granted on such terms as the Board deems appropriate in the circumstances, notwithstanding any limitations on Awards contained in the Plan. Substitute Awards shall not count against the overall share limit set forth in Section 4(a), except as
may be required by reason of Section 422 and related provisions of the Code. 
 5. 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, including conditions relating to applicable federal or state securities laws, as
it considers necessary or 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 only be granted to employees of Casa Systems, Inc., any of Casa Systems, Inc.’s present or future parent or subsidiary
corporations as defined in Sections 424(e) or (f) of the Code, and any other entities the employees of which are eligible to receive Incentive Stock Options under the Code, and shall be subject to and shall be construed consistently with the
requirements of Section 422 of the Code. An Option that is not intended to be an Incentive Stock Option shall be designated a “Nonstatutory Stock Option.” The Company shall have no liability to a Participant, or any
other party, if an Option (or any part thereof) that is intended to be an Incentive Stock Option is not an Incentive Stock Option or if the Company converts an Incentive Stock Option to a Nonstatutory Stock Option. 

(c) Exercise Price. The Board shall establish the exercise price of each Option and specify the exercise price in the applicable Option
agreement. The exercise price shall be not less than 100% of the fair market value per share of Common Stock, as determined by (or in a manner approved by) the Board (“Fair Market Value”), on the date the Option is granted.

 (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; provided, however, that no Option will be granted with a term in excess of 10 years. 

(e) Exercise of Options. Options may be exercised by delivery to the Company of a notice of exercise in a form of notice (which may be
electronic) approved by the Company, together with payment in full (in a manner specified in Section 5(f)) of the exercise price for the number of shares for which the Option is exercised. Shares of Common Stock subject to the Option will be
delivered by the Company as soon as practicable following exercise. 
 (f) Payment Upon Exercise. Common Stock purchased upon the exercise
of an Option granted under the Plan shall be paid for as follows: 
 (1) in cash or by check, payable to the order of the Company; 

  
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 (2) when the Common Stock is registered under the Exchange Act, except as may otherwise be
provided in the applicable Option agreement or approved by the Board, in its sole discretion, by (i) delivery of an irrevocable and unconditional undertaking by a creditworthy broker to deliver promptly to the Company sufficient funds to pay
the exercise price and any required tax withholding or (ii) 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 and any required tax withholding; 
 (3) when the Common Stock is registered under the Exchange Act and
to the extent provided for in the applicable Option agreement or approved by the Board, in its sole discretion, by delivery (either by actual delivery or attestation) of shares of Common Stock owned by the Participant valued at their Fair Market
Value, provided (i) such method of payment is then permitted under applicable law, (ii) such Common Stock, if acquired directly from the Company, was owned by the Participant for such minimum period of time, if any, as may be
established by the Board in its discretion and (iii) such Common Stock is not subject to any repurchase, forfeiture, unfulfilled vesting or other similar requirements; 

(4) to the extent provided for in the applicable Option agreement or approved by the Board in its sole discretion, by delivery of a notice of
“net exercise” to the Company, as a result of which the Participant would pay the exercise price for the portion of the Option being exercised by cancelling a portion of the Option for such number of shares as is equal to the exercise
price divided by the excess of the Fair Market Value on the date of exercise over the Option exercise price per share. 
 (5) to the extent
permitted by applicable law and provided for in the applicable Option agreement or approved by the Board, in its sole discretion, by (i) delivery of a promissory note of the Participant to the Company on terms determined by the Board, or (ii
) payment of such other lawful consideration as the Board may determine; or 
 (6) by any combination of the above permitted forms
of payment. 
 6. Stock Appreciation Rights 

(a) General. The Board may grant Awards consisting of stock appreciation rights (“SARs”) entitling the holder,
upon exercise, to receive an amount of Common Stock or cash or a combination thereof (such form to be determined by the Board) determined by reference to appreciation, from and after the date of grant, in the Fair Market Value of a share of Common
Stock over the measurement price established pursuant to Section 6(b). The date as of which such appreciation is determined shall be the exercise date. 

(b) Measurement Price. The Board shall establish the measurement price of each SAR and specify it in the applicable SAR agreement. The
measurement price shall not be less than 100% of the Fair Market Value on the date the SAR is granted. 
 (c) Duration of SARs. Each
SAR shall be exercisable at such times and subject to such terms and conditions as the Board may specify in the applicable SAR agreement; provided, however, that no SAR will be granted with a term in excess of 10 years. 

  
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 (d) Exercise of SARs. SARs may be exercised by delivery to the Company of a notice of
exercise in a form (which may be electronic) approved by the Company, together with any other documents required by the Board. 
 7. Restricted Stock;
Restricted Stock Units 
 (a) General. The Board may grant Awards entitling recipients to acquire shares of Common Stock
(“Restricted Stock”), subject to the right of the Company to repurchase all or part of such shares at their issue price or other stated or formula price (or to require forfeiture of such shares if issued at no cost) from the
recipient 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. The Board may also grant Awards
entitling the recipient to receive shares of Common Stock or cash to be delivered at the time such Award vests (“Restricted Stock Units”) (Restricted Stock and Restricted Stock Units are each referred to herein as a
“Restricted Stock Award”). 
 (b) Terms and Conditions for All Restricted Stock Awards. The Board shall
determine the terms and conditions of a Restricted Stock Award, including the conditions for vesting and repurchase (or forfeiture) and the issue price, if any. 

(c) Additional Provisions Relating to Restricted Stock. 

(1) Dividends. Unless otherwise provided in the applicable Award agreement, any dividends (whether paid in cash, stock or property)
declared and paid by the Company with respect to shares of Restricted Stock (“Accrued Dividends”) shall be paid to the Participant only if and when such shares become free from the restrictions on transferability and
forfeitability that apply to such shares. Each payment of Accrued Dividends will be made no later than the end of the calendar year in which the dividends are paid to stockholders of that class of stock or, if later, the 15th day of the third
month following the lapsing of the restrictions on transferability and the forfeitability provisions applicable to the underlying shares of Restricted Stock. 

(2) Stock Certificates. The Company may require that any stock certificates issued in respect of shares of Restricted Stock, as well as
dividends or distributions paid on such Restricted Stock, shall be deposited in escrow by the Participant, together with a stock power endorsed in blank, with the Company (or its designee). At 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 his or her Designated Beneficiary. “Designated Beneficiary” means
(i) the beneficiary designated, in a manner determined by the Board, by a Participant to receive amounts due or exercise rights of the Participant in the event of the Participant’s death or (ii) in the absence of an effective
designation by a Participant, “Designated Beneficiary” the Participant’s estate. 
 (d) Additional
Provisions Relating to Restricted Stock Units. 
 (1) Settlement. Upon the vesting of and/or lapsing of any other restrictions
(i.e., settlement) with respect to each Restricted Stock Unit, the Participant shall be entitled to receive from the Company one share of Common Stock or (if so provided in the applicable 

  
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Award agreement) an amount of cash equal to the Fair Market Value of one share of Common Stock. The Board may, in its discretion, provide that settlement of Restricted Stock Units shall be
deferred, on a mandatory basis or at the election of the Participant in a manner that complies with Section 409A of the Code. 
 (2)
Voting Rights. A Participant shall have no voting rights with respect to any Restricted Stock Units. 
 (3) Dividend
Equivalents. The Award agreement for Restricted Stock Units may provide Participants with the right to receive an amount equal to any dividends or other distributions declared and paid on an equal number of outstanding shares of Common Stock
(“Dividend Equivalents”). Dividend Equivalents may be paid currently or credited to an account for the Participants, may be settled in cash and/or shares of Common Stock and may be subject to the same restrictions on transfer
and forfeitability as the Restricted Stock Units with respect to which paid, in each case to the extent provided in the applicable Award agreement. 
 8.
Other Stock-Based Awards 
 (a) General. Other Awards of shares of Common Stock, and other Awards that are valued in whole or
in part by reference to, or are otherwise based on, shares of Common Stock or other property, may be granted hereunder to Participants (“Other Stock-Based-Awards”). Such Other Stock-Based Awards shall also be available as a
form of payment in the settlement of other Awards granted under the Plan or as payment in lieu of compensation to which a Participant is otherwise entitled. Other Stock-Based Awards may be paid in shares of Common Stock or cash, as the Board shall
determine. 
 (b) Terms and Conditions. Subject to the provisions of the Plan, the Board shall determine the terms and conditions of
each Other Stock-Based Award, including any purchase price applicable thereto. 
 9. Adjustments for Changes in Common Stock and Certain Other Events

 (a) Changes in Capitalization. In the event of any stock split, reverse stock split, stock dividend, recapitalization, combination
of shares, reclassification of shares, spin-off or other similar change in capitalization or event, or any dividend or distribution to holders of Common Stock other than an ordinary cash dividend, (i) the number and class of securities
available under the Plan, (ii) the number and class of securities and exercise price per share of each outstanding Option, (iii) the share and per-share provisions and the measurement price of each outstanding SAR, (iv) the number of
shares subject to and the repurchase price per share subject to each outstanding Restricted Stock Award and (v) the share and per-share-related provisions and the purchase price, if any, of each outstanding Other Stock-Based Award, shall be
equitably adjusted by the Company (or substituted Awards may be made, if applicable) in the manner determined by the Board. Without limiting the generality of the foregoing, in the event the Company effects a split of the Common Stock by means of a
stock dividend and the exercise price of and the number of shares subject to an outstanding Option are adjusted as of the date of the distribution of the dividend (rather than as of the record date for such dividend), then an optionee who exercises
an Option between the record date and the distribution date for such 

  
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stock dividend shall be entitled to receive, on the distribution date, the stock dividend with respect to the shares of Common Stock acquired upon such Option exercise, notwithstanding the fact
that such shares were not outstanding as of the close of business on the record date for such stock dividend. 
 (b) Reorganization
Events. 
 (1) Definition. A “Reorganization Event” shall mean: (a) any merger or consolidation of
the Company with or into another entity as a result of which all of the Common Stock of the Company is converted into or exchanged for the right to receive cash, securities or other property or is cancelled, (b) any transfer or disposition of
all of the Common Stock of the Company for cash, securities or other property pursuant to a share exchange or other transaction or (c) any liquidation or dissolution of the Company. 

(2) Consequences of a Reorganization Event on Awards Other than Restricted Stock. 

(i) In connection with a Reorganization Event, the Board may take any one or more of the following actions as to all or any (or any portion
of) outstanding Awards other than Restricted Stock on such terms as the Board determines (except to the extent specifically provided otherwise in an applicable Award agreement or another agreement between the Company and the Participant):
(i) provide that such Awards shall be assumed, or substantially equivalent Awards shall be substituted, by the acquiring or succeeding corporation (or an affiliate thereof), (ii) upon written notice to a Participant, provide that all of
the Participant’s unexercised Awards will terminate immediately prior to the consummation of such Reorganization Event unless exercised by the Participant (to the extent then exercisable) within a specified period following the date of such
notice, (iii) provide that outstanding Awards shall become exercisable, realizable, or deliverable, or restrictions applicable to an Award shall lapse, in whole or in part prior to or upon such Reorganization Event, (iv) in the event of a
Reorganization Event under the terms of which holders of Common Stock will receive upon consummation thereof a cash payment for each share surrendered in the Reorganization Event (the “Acquisition Price”), make or provide for
a cash payment to Participants with respect to each Award held by a Participant equal to (A) the number of shares of Common Stock subject to the vested portion of the Award (after giving effect to any acceleration of vesting that occurs upon or
immediately prior to such Reorganization Event) multiplied by (B) the excess, if any, of (I) the Acquisition Price over (II) the exercise, measurement or purchase price of such Award and any applicable tax withholdings, in exchange
for the termination of such Award, (v) provide that, in connection with a liquidation or dissolution of the Company, Awards shall convert into the right to receive liquidation proceeds (if applicable, net of the exercise, measurement or
purchase price thereof and any applicable tax withholdings) and (vi) any combination of the foregoing. In taking any of the actions permitted under this Section 9(b)(2), the Board shall not be obligated by the Plan to treat all Awards, all
Awards held by a Participant, or all Awards of the same type, identically. 

  
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 (ii) Notwithstanding the terms of Section 9(b)(2)(A), in the case of outstanding Restricted
Stock Units that are subject to Section 409A of the Code: (i) if the applicable Restricted Stock Unit agreement provides that the Restricted Stock Units shall be settled upon a “change in control event” within the meaning of
Treasury Regulation Section 1.409A-3(i)(5)(i), and the Reorganization Event constitutes such a “change in control event”, then no assumption or substitution shall be permitted pursuant to
Section 9(b)(2)(A)(i) and the Restricted Stock Units shall instead be settled in accordance with the terms of the applicable Restricted Stock Unit agreement; and (ii) the Board may only undertake the actions set forth in
clauses (iii), (iv) or (v) of Section 9(b)(2)(A) if the Reorganization Event constitutes a “change in control event” as defined under Treasury Regulation Section 1.409A-3(i)(5)(i) and
such action is permitted or required by Section 409A of the Code; if the Reorganization Event is not a “change in control event” as so defined or such action is not permitted or required by Section 409A of the Code, and the
acquiring or succeeding corporation does not assume or substitute the Restricted Stock Units pursuant to clause (i) of Section 9(b)(2)(A), then the unvested Restricted Stock Units shall terminate immediately prior to the consummation of
the Reorganization Event without any payment in exchange therefor. 
 (iii) For purposes of Section 9(b)(2)(A)(i), an Award (other
than Restricted Stock) shall be considered assumed if, following consummation of the Reorganization Event, such Award confers the right to purchase or receive pursuant to the terms of such Award, for each share of Common Stock subject to the Award
immediately prior to the consummation of the Reorganization Event, the consideration (whether cash, securities or other property) received as a result of the Reorganization Event by holders of Common Stock for each share of Common Stock held
immediately prior to the consummation of the Reorganization Event (and if holders were offered a choice of consideration, the type of consideration chosen by the holders of a majority of the outstanding shares of Common Stock); provided,
however, that if the consideration received as a result of the Reorganization Event is not solely common stock of the acquiring or succeeding corporation (or an affiliate thereof), the Company may, with the consent of the acquiring or succeeding
corporation, provide for the consideration to be received upon the exercise or settlement of the Award to consist solely of such number of shares of common stock of the acquiring or succeeding corporation (or an affiliate thereof) that the Board
determined to be equivalent in value (as of the date of such determination or another date specified by the Board) to the per share consideration received by holders of outstanding shares of Common Stock as a result of the Reorganization Event. 

(3) Consequences of a Reorganization Event on Restricted Stock. Upon the occurrence of a Reorganization Event other than a liquidation
or dissolution of the Company, the repurchase and other rights of the Company with respect to outstanding Restricted Stock shall inure to the benefit of the Company’s successor and shall, unless the Board determines otherwise, apply to the
cash, securities or other property which the Common Stock was converted into or exchanged for pursuant to such Reorganization Event in the same manner and to the same extent as they applied to such Restricted Stock; provided, however,
that the Board may provide for termination or deemed satisfaction of such repurchase or other rights under the instrument evidencing any Restricted Stock or any other agreement between a Participant and the Company, either initially or by amendment.
Upon the occurrence of a Reorganization Event involving the liquidation or dissolution of the Company, except to the extent specifically provided to the contrary in the instrument evidencing any Restricted Stock or any other agreement between a
Participant and the Company, all restrictions and conditions on all Restricted Stock then outstanding shall automatically be deemed terminated or satisfied. 

  
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 10. General Provisions Applicable to Awards 

(a) Transferability of Awards. Awards (or any interest in an Award, including, prior to exercise, any interest in shares of Common
Stock issuable upon exercise of an Option or SAR) shall not be sold, assigned, transferred (including by establishing any short position, put equivalent position (as defined in Rule 16a-1 issued under the
Exchange Act) or call equivalent position (as defined in Rule 16a-1 issued under the Exchange Act)), pledged, hypothecated or otherwise encumbered by the person to whom they are granted, either
voluntarily or by operation of law, and, during the life of the Participant, shall be exercisable only by the Participant; except that Awards may be transferred to family members (as defined in Rule 701(c)(3) under the Securities Act) through
gifts or (other than Incentive Stock Options) domestic relations orders or to an executor or guardian upon the death or disability of the Participant. The Company shall not be required to recognize any such permitted transfer until such time as such
permitted transferee shall deliver to the Company a written instrument, as a condition to such transfer, in form and substance satisfactory to the Company confirming that such transferee shall be bound by all of the terms and conditions of the
Award. References to a Participant, to the extent relevant in the context, shall include references to authorized transferees. For the avoidance of doubt, nothing contained in this Section 10(a) shall be deemed to restrict a transfer to the
Company. 
 (b) Documentation. Each Award shall be evidenced in such form (written, electronic or otherwise) as the Board shall
determine. Each Award may contain terms and conditions in addition to those set forth in the Plan. 
 (c) Board Discretion. Except as
otherwise provided by the Plan, each Award may be made alone or in addition or in relation to any other Award. The terms of each 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, termination or other cessation of
employment, 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) Withholding. The Participant must satisfy all applicable
federal, state, and local or other income and employment tax withholding obligations before the Company will deliver stock certificates or otherwise recognize ownership of Common Stock under an Award. The Company may decide to satisfy the
withholding obligations through additional withholding on salary or wages. If the Company elects not to or cannot withhold from other compensation, the Participant must pay the Company the full amount, if any, required for withholding or have a
broker tender to the Company cash equal to the withholding obligations. Payment of withholding obligations is due before the Company will issue any shares on exercise, vesting or release from forfeiture of an Award or at the same time as payment of
the exercise or purchase price unless the Company determines otherwise. If provided for in an Award or approved by the Board in its sole discretion, a Participant may satisfy such tax obligations in whole or in part by delivery (either by actual
delivery or attestation) of shares of Common Stock, including shares retained from the Award creating the tax obligation, valued at their Fair Market Value; provided, however, except as otherwise provided by the Board, that the total tax
withholding where stock is 

  
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being used to satisfy such tax obligations cannot exceed the Company’s minimum statutory withholding obligations (based on minimum statutory withholding rates for federal and state tax
purposes, including payroll taxes, that are applicable to such supplemental taxable income). Shares used to satisfy tax withholding requirements cannot be subject to any repurchase, forfeiture, unfulfilled vesting or other similar requirements. 

(f) Amendment of Award. 

(1) 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. The Participant’s consent to such action shall be required unless (i) the Board determines
that the action, taking into account any related action, does not materially and adversely affect the Participant’s rights under the Plan or (ii) the change is permitted under Section 9. 

(2) The Board may, without stockholder approval, amend any outstanding Award granted under the Plan to provide an exercise price per share
that is lower than the then-current exercise price per share of such outstanding Award. The Board may also, without stockholder approval, cancel any outstanding award (whether or not granted under the Plan) and grant in substitution therefor new
Awards under the Plan covering the same or a different number of shares of Common Stock and having an exercise price per share lower than the then-current exercise price per share of the cancelled award. 

(g) 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 issued or 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 regulations 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. 

(h) Acceleration. The Board may at any time provide that any Award shall become immediately exercisable in whole or in part, free of
some or all restrictions or conditions, or otherwise realizable in whole or in part, as the case may be. 
 11. Miscellaneous 

(a) No Right To Employment or Other Status. No person shall have any claim or right to be granted an Award by virtue of the adoption of
the Plan, 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, except as expressly provided in the applicable Award. 

  
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 (b) 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 of such shares. 

(c) 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 expiration of 10 years from the earlier of (i) the date on which the Plan was adopted by the Board or (ii) the date the Plan was approved by the Company’s stockholders, but Awards previously
granted may extend beyond that date. 
 (d) Amendment of Plan. The Board may amend, suspend or terminate the Plan or any portion
thereof at any time; provided that if at any time the approval of the Company’s stockholders is required as to any modification or amendment under Section 422 of the Code or any successor provision with respect to Incentive Stock
Options, the Board may not effect such modification or amendment without such approval. Unless otherwise specified in the amendment, any amendment to the Plan adopted in accordance with this Section 11(d) shall apply to, and be binding on the
holders of, all Awards outstanding under the Plan at the time the amendment is adopted, provided the Board determines that such amendment, taking into account any related action, does not materially and adversely affect the rights of Participants
under the Plan. 
 (e) Authorization of Sub-Plans (including Grants to non-U.S. Employees). The Board may from time to time establish
one or more sub-plans under the Plan for purposes of satisfying applicable securities, tax or other laws of various jurisdictions. The Board shall establish such sub-plans by adopting supplements to the Plan containing (i) such limitations on
the Board’s discretion under the Plan as the Board deems necessary or desirable or (ii) such additional terms and conditions not otherwise inconsistent with the Plan as the Board shall deem necessary or desirable. All supplements adopted
by the Board shall be deemed to be part of the Plan, but each supplement shall apply only to Participants within the affected jurisdiction and the Company shall not be required to provide copies of any supplement to Participants in any jurisdiction
which is not the subject of such supplement. 
 (f) Compliance with 409A of the Code. Except as provided in individual Award
agreements initially or by amendment, if and to the extent (i) any portion of any payment, compensation or other benefit provided to a Participant pursuant to the Plan in connection with his or her employment termination constitutes
“nonqualified deferred compensation” within the meaning of Section 409A of the Code and (ii) the Participant is a specified employee as defined in Section 409A(a)(2)(B)(i) of the Code, in each case as determined by the
Company in accordance with its procedures, by which determinations the Participant (through accepting the Award) agrees that he or she is bound, such portion of the payment, compensation or other benefit shall not be paid before the day that is six
months plus one day after the date of “separation from service” (as determined under Section 409A of the Code) (the “New Payment Date”), except as Section 409A of the Code may then permit. The aggregate of
any payments that otherwise would have been paid to the Participant during the period between the date of separation from service and the New Payment Date shall be paid to the Participant in a lump sum on such New Payment Date, and any remaining
payments will be paid on their original schedule. 

  
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The Company makes no representations or warranty and shall have no liability to the Participant or any other person if any provisions of or payments, compensation or other benefits under the Plan
are determined to constitute nonqualified deferred compensation subject to Section 409A of the Code but do not to satisfy the conditions of that section. 

(g) Limitations on Liability. Notwithstanding any other provisions of the Plan, no individual acting as a director, officer, other
employee, or agent of the Company will be liable to any Participant, former Participant, spouse, beneficiary, or any other person for any claim, loss, liability, or expense incurred in connection with the Plan, nor will such individual be personally
liable with respect to the Plan because of any contract or other instrument he or she executes in his or her capacity as a director, officer, other employee, or agent of the Company. The Company will indemnify and hold harmless each director,
officer, other employee, or agent of the Company to whom any duty or power relating to the administration or interpretation of the Plan has been or will be delegated, against any cost or expense (including attorneys’ fees) or liability
(including any sum paid in settlement of a claim with the Board’s approval) arising out of any act or omission to act concerning the Plan unless arising out of such person’s own fraud or bad faith. 

(h) Governing Law. The provisions of the Plan and all Awards made hereunder shall be governed by and interpreted in accordance with the
laws of the State of Delaware, excluding choice-of-law principles of the law of such state that would require the application of the laws of a jurisdiction other than the State of Delaware. 

  
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 CASA SYSTEMS, INC.  

2011 STOCK INCENTIVE PLAN 

CALIFORNIA SUPPLEMENT 

Pursuant to Section 11(e) of the Plan, the Board has adopted this supplement for purposes of satisfying the requirements of
Section 25102(o) of the California Law: 
 Any Awards granted under the Plan to a Participant who is a resident of the State of
California on the date of grant (a “California Participant”) shall be subject to the following additional limitations, terms and conditions: 

1. Additional Limitations on Options. 

(a) Maximum Duration of Options. No Options granted to California Participants shall have a term in excess of 10 years measured from
the Option grant date. 
 (b) Minimum Exercise Period Following Termination. Unless a California Participant’s employment is
terminated for cause (as defined by applicable law, the terms of the Plan or option grant or a contract of employment), in the event of termination of employment of such Participant, such Participant shall have the right to exercise an Option, to
the extent that such Participant is entitled to exercise such Option on the date employment terminated, until the earlier of: (i) at least six months from the date of termination, if termination was caused by such Participant’s death or
disability, (ii) at least 30 days from the date of termination, if termination was caused other than by such Participant’s death or disability and (iii) the Option expiration date. 

2. Additional Limitations for Other Stock-Based Awards. The terms of all Awards granted to a California Participant under Section 8 of the Plan
shall comply, to the extent applicable, with Sections 260.140.42, 260.140.45 and 260.140.46 of the California Code of Regulations. 
 3. Additional
Limitations on Timing of Awards. No Award granted to a California Participant shall become exercisable, vested or realizable, as applicable to such Award, unless the Plan has been approved by the holders of a majority of the Company’s
outstanding voting securities by the later of (i) within 12 months before or after the date the Plan was adopted by the Board, or (ii) prior to or within 12 months of the granting of any Award to a California Participant. 

4. Additional Restriction Regarding Recapitalizations, Stock Splits, Etc. For purposes of Section 9 of the Plan, in the event of a stock split,
reverse stock split, stock dividend, recapitalization, combination, reclassification or other distribution of the Company’s securities underlying the Award without the receipt of consideration by the Company, the number of securities
purchasable, and in the case of Options, the exercise price of such Options, must be proportionately adjusted. 
 5. Additional Limitations on
Transferability of Awards. Notwithstanding the provisions of Section 10(a) of the Plan, an Award granted to a California Participant may not be transferred to an executor or guardian upon the disability of the Participant. 

  
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 CASA SYSTEMS, INC. 

Amendment No. 1 To 2011 Stock Incentive Plan 

The 2011 Stock Incentive Plan (the “Plan”) of Casa Systems, Inc. (the “Company”) is hereby amended, pursuant to
Section 11(d) of the Plan, as follows: 
  

	 	1.	Section 4(a) of the Plan be and hereby is amended by deleting the first sentence thereof and replacing it with the following: 


“Subject to adjustment under Section 9, Awards may be made under the Plan for up to a number of shares of common stock, $0.001 par
value per share, of the Company (the “Common Stock”), equal to the sum of (a) 698,371, plus (b ) such additional number of shares of Common Stock as is equal to the sum of (x) the number of shares of Common
Stock reserved for issuance under the Company’s 2003 Stock Incentive Plan, as amended (the “2003 Plan”) that remain available for issuance under the 2003 Plan as of the time immediately before termination of the 2003 Plan and
(y) the number of shares of Common Stock subject to awards granted under the 2003 Plan which awards expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by the Company at their original issuance price pursuant to a
contractual repurchase right (subject, however, in the case of Incentive Stock Options (as hereinafter defined) to any limitations of the Code); provided, however, that the maximum number of shares of Common Stock available for issuance under the
Plan (including any shares becoming available by reason of clause (y)) shall be 1,335,871.” 1 

Adopted by the Board of Directors: May 25, 2011 

Adopted by the Stockholders: May 25, 2011 

 

	1 	Subsequent to the amendment of the Plan referred to above, the Company effected a two-for-one split of the Common Stock. As a result of the split, the number of shares of Common Stock reserved for Awards under
clause (a) above has been adjusted to 1,396,742, and the maximum number of shares of Common Stock available for issuance under the Plan has been adjusted to 2,671,742. 


  
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 CASA SYSTEMS, INC. 

Amendment No. 2 To 2011 Stock Incentive Plan 

The 2011 Stock Incentive Plan (the “Plan”) of Casa Systems, Inc. (the “Company”) is hereby amended, pursuant to
Section 11(d) of the Plan, as follows: 
  

	 	2.	Section 4(a) of the Plan be and hereby is amended by deleting the first sentence thereof and replacing it with the following: 


“Subject to adjustment under Section 9, Awards may be made under the Plan for up to a number of shares of common stock, $0.001 par
value per share, of the Company (the “Common Stock”), equal to the sum of (a) 2,396,742, plus (b) such additional number of shares of Common Stock as is equal to the sum of (x) the number of shares of Common
Stock reserved for issuance under the Company’s 2003 Stock Incentive Plan, as amended (the “2003 Plan”) that remain available for issuance under the 2003 Plan as of the time immediately before termination of the 2003 Plan and
(y) the number of shares of Common Stock subject to awards granted under the 2003 Plan which awards expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by the Company at their original issuance price pursuant to a
contractual repurchase right (subject, however, in the case of Incentive Stock Options (as hereinafter defined) to any limitations of the Code); provided, however, that the maximum number of shares of Common Stock available for issuance under the
Plan (including any shares becoming available by reason of clause (y)) shall be 3,671,742.” 
 Adopted by the Board of
Directors: June 11, 2014 
 Adopted by the Stockholders: June 11, 2014 

  
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 CASA SYSTEMS, INC. 

Amendment No. 3 To 2011 Stock Incentive Plan 

The 2011 Stock Incentive Plan (the “Plan”) of Casa Systems, Inc. (the “Company”) is hereby amended, pursuant to
Section 11(d) of the Plan, as follows: 
  

	 	3.	Section 4(a) of the Plan be and hereby is amended by deleting the first sentence thereof and replacing it with the following: 


“Subject to adjustment under Section 9, Awards may be made under the Plan for up to a number of shares of common stock, $0.001 par
value per share, of the Company (the “Common Stock”), equal to the sum of (a) 3,396,742, plus (b) such additional number of shares of Common Stock as is equal to the sum of (x) the number of shares of Common
Stock reserved for issuance under the Company’s 2003 Stock Incentive Plan, as amended (the “2003 Plan”) that remain available for issuance under the 2003 Plan as of the time immediately before termination of the 2003 Plan and
(y) the number of shares of Common Stock subject to awards granted under the 2003 Plan which awards expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by the Company at their original issuance price pursuant to a
contractual repurchase right (subject, however, in the case of Incentive Stock Options (as hereinafter defined) to any limitations of the Code); provided, however, that the maximum number of shares of Common Stock available for issuance under the
Plan (including any shares becoming available by reason of clause (y)) shall be 4,671,742.” 
 Adopted by the Board of
Directors: June 29, 2015 
 Adopted by the Stockholders: June 29, 2015 

  
 3