ADDENDUM        FOR        ASYNCHRONOUS TRANSFER MODE (ATM) SERVICE

This Addendum for Asynchronous Transfer Mode (ATM) Service (the "Addendum") is made as of the 8th day of May,
2000, to that certain Digital Services Agreement made by and between WorldCom Network Services, Inc. ("MCI WorldCom") and Ciera Network Systems, Inc.
("Customer"), dated as of May 8th, 2000 (the "DSA"), more specifically described as DSA # CNS - 000508.
The DSA and this Addendum shall collectively be referred to as the "Agreement". All of the terms and conditions contained in the DSA (including without
limitation, payment of charges, suspension of service, force majeure, service warranty, limitation of liability and indemnity) will apply to ATM Service (as defined herein) to be provided by MCI
WorldCom to Customer and where applicable, references to Service in the DSA will be deemed to include ATM Service. In the event of any conflict between the terms of the DSA and the terms of this
Addendum, the terms of this Addendum shall control. As of the first date written above, (i) all existing agreements for ATM Service between Customer (including Customer's parent company, Company's
subsidiaries and other entities under common control with Customer) and MCI WorldCom (including MCI WorldCom's parent company, MCI WorldCom's subsidiaries and other entities under common control with
MCI WorldCom) will be terminated and of no further force or effect except for charges or credits due for ATM Services provided prior to such date, and (ii) all ATM Service being provided to the
Customer Group by member(s) of the MCI WorldCom Group will be provisioned and maintained under the terms of this Addendum.

1.Service To Be Provided.



Port Speed

Maximum PVC BandwidthDS-1

1.536 MbpsDS-3

25.6 MbpsOC-3

25.6 Mbps


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Port Speed

PVC SpeedsDS-1 Level

16 Kbps, 32Kbps, 48Kbps, 64Kbps
plus all 64Kbps increments up to 1.536MbpsDS-3 Level

16 Kbps, 32Kbps, 48Kbps, 64Kbps
plus all 64Kbps increments up to 25.6MbpsOC-3 Level

Determined on an individual case basis




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2.Term.This Addendum shall be effective between the parties as of the date first written above and shall
continue month-to-month (the"ATM Term").

3.Commitment.Commencing                        and
continuing through the end of the ATM Term (the "ATM Commitment Period"), Customer agrees to obtain, on a take-or-pay basis, ATM Monthly Port Charges (as described in Subsection 4(i) below) PLUS ATM
Monthly PVC Charges (as described in Subsection 4(ii) below) PLUS Customer's Monthly Port Charges and Customer's Monthly CIR Charges, if any, from MCI WorldCom pursuant to an Addendum for Frame Relay
Service PLUS Customer's Integrated Internet Access Monthly Recurring Charges, if any, from MCI WorldCom pursuant to an Addendum for Integrated Internet Access Service (collectively, "Customer's Applicable ATM
Charges") of at least * ("Customer's ATM Commitment"). In the event Customer
does not maintain Customer's ATM Commitment in any month during the ATM Commitment Period, then for such month(s) Customer will pay MCI WorldCom the difference between Customer's ATM Commitment and
Customer's Applicable ATM Charges (the"ATM Deficiency Charge"). The ATM Deficiency Charge, if applicable, will be due at the same time payment is due
for Service provided to Customer or immediately upon expiration of the ATM Term. MCI WorldCom agrees to include Customer's ATM Monthly Port Charges and Customer's ATM Monthly PVC Charges in
determining if Customer has met any private line take-or-pay commitment(s) Customer has with MCI WorldCom.

4.MCI WorldCom's Charges for ATM Service.In addition to the cost of any IXC Connecting Legs as described in
Subsection 1(B) above, Customer agrees to pay the following charges for ATM Services provided by MCI WorldCom hereunder. All payments shall be made in US Dollars.



Port Speed

Monthly Port ChargesDS-1 Level

*DS-3 Level

*OC-3 Level

*




Total CIR

VBR*

ABR*

CBR16Kbps

*

*

*32Kbps

*

*

*48Kbps

*

*

*64Kbps

*

*

*


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Port

Installation ChargeDS-1 Level

*DS-3 Level

*OC-3 Level

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|Description                                                 |  | Charge
|----------------------------------------------------------- |  | ------
|Expedite Charge (per Port)                                  |  | *     
|Cancellation Charge-Pre-Engineering (per Port)              |  | *     
|Cancellation Charge-Post-Engineering (per Port)             |  | *     
|Date Change (per Port)                                      |  | *     
|Administrative Order Change (per port)                      |  | *     
|Non-Administrative Order Change-Pre-Engineering (per Port)  |  | *     
|Non-Administrative Order Change-Post-Engineering (per Port) |  | *     



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5.Other Terms and Conditions.Except to the extent specifically modified by this Addendum, all terms and
conditions contained in the DSA and any other Addenda applicable thereto shall remain in full force and effect and shall not be altered, modified, amended or changed.

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IN WITNESS WHEREOFthe parties have executed this Addendum for ATM Service as of the date first written above.

|CIERA NETWORK SYSTEMS, INC.    |  | MCI WORLDCOM NETWORK SERVICES, INC.
|------------------------------ |  | -----------------------------------
|By:                            |  | /s/ R.W. Livingston(Signature)     
|R.W. Livingston(Print Name)    |  | James J. Foran(Print Name)         
|CEO            5/8/2000(Title) |  | Regional Sales Director(Title)     

Schedules:

Schedule 1
Tier A and Tier C Cities

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MCI WORLDCOM NETWORK SERVICES, INC.TELECOMMUNICATIONS SERVICES AGREEMENT(Switched Services)

ThisTelecommunications Services Agreement(the "TSA") is entered
into as of the 8th day of May, 2000, by and betweenMCI WORLDCOM Network Services, Inc.(successor in interest to WorldCom Network Services, Inc.), a
Delaware corporation, with its principal office at 6929 North Lakewood Avenue, Tulsa, Oklahoma 74117 ("MCI WorldCom") and Ciera Network Systems, Inc., a
Texas corporation, with its principal office at 2630 Fountainview, Houston Texas 77057 ("Customer").

In
consideration of good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties agree as follows:

1.Switched Services; Other Documents; Start of Service.

(A)ServicesMCI WorldCom agrees to provide and Customer agrees to accept and pay for switched
telecommunications services and other associated services (collectively the "Switched Services") as further described in the
"Attachments" attached hereto and incorporated herein by reference, which describe the particular services, rates, specific terms and other information
necessary or appropriate for MCI WorldCom to provide the Switched Services to Customer. The Switched Services provided by MCI WorldCom are subject to (i) the terms and conditions contained in
this TSA and the Program Enrollment Terms (the "PET") which is attached hereto and incorporated herein by reference, (ii) the rates and discounts
and other applicable terms set forth in Attachment(s) attached hereto from time to time and incorporated herein by reference, and (iii) each Service Request (described below) which is accepted
hereunder. The PET, as subscribed to by the parties, shall set forth the Effective Date, the Service Term, Customer's minimum monthly commitment, if any, and other information necessary to provide the
Switched Services under this TSA. In the event of a conflict between the terms of this TSA, the PET, the Attachments and the Service Request(s), the following order of precedence will prevail:
(1) the PET, (2) the Attachments, (3) this TSA, and (4) Service Request(s). This TSA, the PET, and the applicable Attachments are sometimes collectively referred to as the
"Agreement".

(B)Service RequestsCustomer's requests to initiate or cancel Switched Services shall be described in an
appropriate MCI WorldCom Service Request ("Service Request"). A Service Request may consist of machine readable tapes, facsimiles or other means
approved by MCI WorldCom. Further, Service Requests shall specify all reasonable information, as determined by MCI WorldCom, necessary or appropriate for MCI WorldCom to provide the Switched
Service(s) in question, which shall include without limitation, the type, quantity and end point(s) (when necessary) of circuits comprising a Service Interconnection as described in the applicable
Service Schedules, or automatic number identification ("ANI") information relevant to the Switched Service(s), the "Requested Service Date", and
charges, if any, relevant to the Switched Services described in the Service Request.

(C)Start of ServiceMCI WorldCom's obligation to provide and Customer's obligation to accept and pay for
non-usage sensitive charges for Switched Services shall be binding to the extent provided for in this Agreement upon the submission of an acceptable Service Request to MCI WorldCom by Customer.
Customer's obligation to pay for usage sensitive charges for Switched Services shall commence with respect to any Switched Service as of the date the Switched Service in question is made available to
and used by Customer ("Start of Service"), but in no event later than the "Requested Service Date" if
such Switched Service is available for Customer's use as of such Requested Service Date. Start of Service for particular Services shall be further described in the Attachment(s) relevant to the
Switched Services in question.

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2.Cancellation.

(A)Cancellation ChargeAt any time after the Effective Date, Customer may cancel this Agreement if Customer
provides written notification thereof to MCI WorldCom not less than thirty (30) days prior to the effective date of cancellation. In such case (or in the event MCI WorldCom terminates this Agreement
as provided in Section 7), Customer shall pay to MCI WorldCom all charges for Services provided through the effective date of such cancellation plus a cancellation charge (the
"Cancellation Charge") equal to * of Customer's commitment(s), if any, (as described in the PET) that would have become due for the unexpired portion of
the Service Term.

(B)Liquidated DamagesIt is agreed that MCI WorldCom's damages in the event Customer cancels this Agreement
shall be difficult or impossible to ascertain. The provision for a Cancellation Charge in Subsection 2(A) above is intended, therefore, to establish liquidated damages in the event of a cancellation
and is not intended as a penalty.

(C)Cancellation Without ChargeNotwithstanding anything to the contrary contained in Subsection 2(A) above,
Customer may cancel this Agreement, as provided below, without incurring any cancellation charge (other than payment for Services provided by MCI WorldCom up through the effective date of
cancellation) if (i) MCI WorldCom fails to provide a network as warranted in Section 8 below; (ii) MCI WorldCom fails to deliver call detail records promptly based on the frequency
selected by Customer (i.e., monthly, weekly or daily); or (iii) MCI WorldCom fails to submit ANI(s) relevant to Customer's Service Requests to the applicable local exchange companies
("LECs") within the time period described in applicable Attachment(s). Provided, however, Customer must give MCI WorldCom written notice of any such
default and an opportunity to cure such default within five (5) days of the notice. In the event MCI WorldCom fails to cure any such default within the five-day period on more than three (3) occasions
within any six (6) month period, Customer may cancel this Agreement without incurring any cancellation charge.

3.Customer's End Users.

(A)End UsersCustomer will obtain, and upon MCI WorldCom's request provide MCI WorldCom (within two (2)
business days of the date of the request), a written Letter of Agency ("LOA") acceptable to MCI WorldCom (or with any other means if approved by the
Federal Communications Commission ("FCC"), the applicable public utility commission ("PUC") and the
applicable LEC), for each ANI indicating the consent of such end user of Customer ("End User") to be served by Customer and transferred (by way of
change of such End User's designated presubscribed interexchange carrier (PIC)) to the MCI WorldCom network prior to submitting a Service Request to MCI WorldCom. Each LOA will provide, among other
things, that the End User has consented to the transfer being performed by Customer or Customer's designee. When applicable, Customer will be responsible for notifying its End Users, in writing (or by
any other means if approved by the FCC, the applicable PUC and the applicable LEC) that (i) a transfer charge will be reflected on their LEC bill for effecting a change in their PIC,
(ii) the entity name under which their interstate, intrastate, local and/or operator services will be billed (if different from Customer), and (iii) the "primary" telephone number(s) to
be used for maintenance and questions concerning their telecommunications services and/or billing. Customer agrees to send MCI WorldCom a copy of the documentation Customer uses to satisfy the above
requirements promptly upon request of MCI WorldCom. MCI WorldCom may change the foregoing requirements for Customer's confirming orders and/or notifying End Users regarding the transfer charge at any
time in order to conform with applicable FCC and state regulations. Provided, however, Customer will be solely responsible for ensuring that the transfer of End Users to the MCI WorldCom network
conforms with applicable FCC and state regulations, including without limitation, the regulations established by the FCC with respect to verification of orders for long distance service generated by
telemarketing as promulgated in 47 C.F.R., Part 64, Subpart K, §64.1100 or any successor regulation(s).

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(B)Transfer Charges/Disputed TransfersCustomer agrees that it is responsible for (i) all charges
incurred by MCI WorldCom to change the PIC of End Users to the MCI WorldCom network, (ii) all charges incurred by MCI WorldCom to change End Users back to their previous PIC arising from
disputed transfers to the MCI WorldCom network plus, at MCI WorldCom's option, an administrative charge equal to twenty percent (20%) of such charges, and (iii) any other damages or costs
suffered by or awards against MCI WorldCom resulting from disputed transfers.

(C)Excluded ANIsCustomer agrees to provide all ANIs to be carried on the MCI WorldCom network prior to the
provisioning of such ANIs with the LECs. MCI WorldCom has the right to reject any ANI supplied by Customer for any of the following reasons: (i) MCI WorldCom is not authorized to provide or
does not provide long distance services in the particular jurisdiction in which the ANI is located, (ii) a particular ANI submitted by Customer is not in proper form, (iii) Customer is
not certified to provide long distance services in the jurisdiction in which the ANI is located, (iv) Customer is in material default of this Agreement, (v) Customer fails to cooperate
with MCI WorldCom in implementing reasonable verification processes determined by MCI WorldCom to be necessary or appropriate in the conduct of business, (vi) such ANI is rejected by a LEC
(e.g., "PIC freezes"), or (vii) any other circumstance reasonably determined by MCI WorldCom which could adversely affect MCI WorldCom's performance under this Agreement or MCI WorldCom's
general ability to transfer its other customers or other end users to the MCI WorldCom network, including without limitation, MCI WorldCom's ability to electronically effect PIC changes with the LECs.
In the event MCI WorldCom rejects an ANI, MCI WorldCom will notify Customer of its decision specifically describing the rejected ANI and the reason(s) for rejecting that ANI, and will not incur any
further liability under this Agreement with regard to that ANI. Further, any ANI previously requested by Customer for Switched Services may be deactivated by MCI WorldCom if no Switched Services
billings relevant thereto are generated in any three (3) consecutive calendar month/billing periods. MCI WorldCom will be under no obligation to accept ANIs submitted by Customer within the last full
calendar month period preceding the scheduled expiration of the Service Term.

(D)RecordsCustomer will maintain documents and records
("Records") supporting Customer's re-sale of Switched Services, including, but not limited to, appropriate and valid documentation of each subscribing
End User's authorization to Customer to act as End User's PIC for a period of not less than twelve (12) months or such longer period as may be required by applicable law, rule or regulation. Customer
shall indemnify MCI WorldCom for any and all costs, charges or expenses incurred by MCI WorldCom arising from disputed PIC selections involving Switched Services to be provided to Customer.

(E)Customer ServiceCustomer will be solely responsible for billing its End Users and providing such End Users
with customer service. Customer agrees to notify MCI WorldCom as soon as reasonably possible in the event an End User notifies Customer of problems associated with the Switched Services, including
without limitation, excess noise, echo, or loss of service.

4.Customer's Responsibilities

(A)Expedite ChargesIn the event Customer requests expedited services and/or changes to Service Requests and
MCI WorldCom agrees to such request, MCI WorldCom will pass through the charges assessed by any supplying parties (e.g., local access providers) for such expedited charges and/or changes to Service
Requests involved at the same rate to Customer. MCI WorldCom may further condition its performance of such request upon Customer's payment of such additional charges to MCI WorldCom.

(B)Fraudulent CallsCustomer shall indemnify and hold MCI WorldCom harmless from any and all costs, expenses,
damages, claims or actions arising from fraudulent calls of any nature which may comprise a portion of the Switched Services to the extent that the party claiming the call(s) in question to be
fraudulent is (or had been at the time of the call) an End User of such Switched Services

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through Customer or an end user of the Switched Services through Customer's distribution channels. Customer shall not be excused from paying MCI WorldCom for Switched Services provided to Customer or
any portion thereof on the basis that fraudulent calls comprised a corresponding portion of the Switched Services. In the event MCI WorldCom discovers fraudulent calls being made (or reasonably
believes fraudulent calls are being made), nothing contained herein shall prohibit MCI WorldCom from taking immediate action (without notice to Customer) that is reasonably necessary to prevent such
fraudulent calls from taking place, including without limitation, denying Switched Services to particular ANIs or terminating Switched Services to or from specific locations. Provided, however,
nothing contained herein will impose any obligation on MCI WorldCom to take any action with respect to fraudulent calls.

5.Charges and Payment Terms.

(A)PaymentMCI WorldCom Billings for Switched Services hereunder are made on a monthly basis (or such other
basis as may be mutually agreed to by the parties) following Start of Service. Subject to Subsection 5(C) below, Switched Services shall be billed at the rates set forth in the applicable
Attachment(s). Discounts, if any, applicable to the rates for certain Services are set forth in the applicable Attachment(s). Customer will pay all undisputed charges relative to each MCI WorldCom
invoice for Switched Services within thirty (30) days of the invoice date set forth on each MCI WorldCom invoice to Customer ("Due Date"). If payment is
not received by MCI WorldCom on or before the Due Date, Customer shall also pay a late fee in the amount of the lesser of * of the unpaid balance of the charges for Switched Services rendered per
month or partial month that such payment is late, or the maximum lawful rate under applicable state law.

(B)TaxesCustomer acknowledges and understands that MCI WorldCom computes all charges herein exclusive of any
applicable federal, state or local use, excise, gross receipts, sales and privilege taxes, duties, fees or similar liabilities (other than general income or property taxes), whether charged to or
against MCI WorldCom or Customer because of the Switched Services furnished to Customer ("Additional Charges"). Customer shall pay such Additional
Charges in addition to all other charges provided for herein. Customer will not be liable for certain Additional Charges if Customer provides MCI WorldCom with an appropriate exemption certificate.

(C)Modification of ChargesMCI WorldCom reserves the right to eliminate particular Switched Services and/or
modify charges for particular Switched Services (which charge modifications shall not exceed then-current generally available MCI WorldCom charges for comparable services), upon not less than sixty
(60) days prior notice to Customer, which notice will state the effective date for the charge modification. In the event MCI WorldCom notifies Customer of the elimination of a particular Switched
Service and/or an increase in the charges, Customer may terminate this Agreement without incurring a cancellation charge (other than payment for Services provided by MCI WorldCom up through the
effective date of cancellation) only with respect to the Switched Service(s) affected by the
increase in charges. In order to cancel such Switched Service(s), Customer must notify MCI WorldCom, in writing, at least thirty (30) days prior to the effective date of the increase in charges. In
the event Customer cancels its subscription to a particular Switched Service as described in this Subsection 5(C), MCI WorldCom and Customer agree to negotiate in good faith concerning Customer's
minimum monthly commitment, if any, described in the PET.

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(D)Billing DisputesNotwithstanding the foregoing, amounts reasonably disputed by Customer (along with late
fees attributable to such amounts) shall apply but shall not be due and payable for a period of sixty (60) days following the Due Date therefor, provided Customer: (i) pays all undisputed
charges on or before the Due Date, (ii) presents a written statement and supporting documentation of any billing discrepancies to MCI WorldCom in reasonable detail on or before the Due Date of
the invoice in question, and (iii) negotiates in good faith with MCI WorldCom for the purpose of resolving such dispute within said sixty (60) day period. In the event such dispute is mutually
agreed upon and resolved in favor of MCI WorldCom, Customer agrees to pay MCI WorldCom the disputed amounts together with any applicable late fees within ten (10) days of the resolution (the
"Alternate Due Date"). In the event such dispute is mutually agreed upon and resolved in favor of Customer, Customer will receive a credit for the
disputed charges in question and the applicable late fees. In the event MCI WorldCom has responded to Customer's dispute in writing and the parties fail to mutually resolve or settle the dispute
within such sixty (60) day period (unless MCI WorldCom has agreed in writing to extend such period) all disputed amounts together with late fees shall become due and payable, and this provision shall
not be construed to prevent Customer from pursuing any available legal remedies. MCI WorldCom shall not be obligated to consider any Customer notice of billing discrepancies which are received by MCI
WorldCom more than sixty (60) days following the Due Date of the invoice in question.

6.Credit: Creditworthiness:

(A)CreditCustomer's execution of this Agreement signifies Customer's acceptance of MCI WorldCom's initial and
continuing credit approval procedures and policies. MCI WorldCom reserves the right to withhold initiation or full implementation of any or all Switched Services under this Agreement pending MCI
WorldCom's initial satisfactory credit review and approval thereof which may be conditioned upon terms specified by MCI WorldCom, including, but not limited to, security for payments due hereunder in
the form of a cash deposit or other means. MCI WorldCom reserves the right to modify its requirements, if any, with respect to any security or other assurance provided by Customer for payments due
hereunder in light of Customer's actual usage when compared to projected usage levels upon which any security or assurance requirement was based.

(B)CreditworthinessIf at any time there is a material adverse change in Customer's creditworthiness, then in
addition to any other remedies available to MCI WorldCom, MCI WorldCom may elect, in its sole discretion, to exercise one or more of the following remedies: (i) cause Start of Service for
Switched Services described in a previously executed Service Request to be withheld; (ii) cease providing Switched Services pursuant to a Suspension Notice in accordance with
Section 7(A); (iii) decline to accept a Service Request or other requests from Customer to provide Switched Services which MCI WorldCom may otherwise be obligated to accept; and/or
(iv) condition its provision of Switched Services or acceptance of a Service Request on Customer's assurance of payment which shall be a deposit or such other means to establish reasonable
assurance of payment. An adverse material change in Customer's creditworthiness shall include, but not be limited to: (i) Customer's material default of its obligations to MCI WorldCom under
this or any other agreement with MCI WorldCom; (ii) failure of Customer to make full payment of all undisputed charges due hereunder on or before the Due Date (or disputed charges on or before
the Alternate Due Date) on three (3) or more occasions during any period of twelve (12) or fewer months or Customer's failure to make such payment on or before the Due Date (or the Alternate Due Date,
if applicable) in any two (2) consecutive months; (iii) acquisition of Customer (whether in whole or by majority or controlling interest) by an entity which is insolvent, which is subject to
bankruptcy or insolvency proceedings, which owes past due amounts to MCI WorldCom or any entity affiliated with MCI WorldCom or which is a materially greater credit risk than Customer; or,
(iv) Customer's being subject to or having filed for bankruptcy or insolvency proceedings or the legal insolvency of Customer.

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7.Remedies for Breach.

(A)Suspension of ServiceIn the event all undisputed charges due pursuant to MCI WorldCom's invoice are not
paid in full by the Due Date or disputed charges owed by Customer, if any, are not paid in full by the Alternate Due Date, MCI WorldCom shall have the right, after giving Customer at least five (5)
days prior notice and opportunity to pay such charges within such 5-day period, to suspend all or any portion of the Switched Services to Customer ("Suspension
Notice") until such time (designated by MCI WorldCom in its Suspension Notice) as Customer has paid in fullallundisputed
charges then due to MCI WorldCom, including any late fees. Following such payment, MCI WorldCom shall reinstitute Switched Services to Customeronlywhen Customer provides MCI WorldCom with satisfactory assurance of Customer's ability to pay for such Switched Services (i.e., a deposit, letter of credit or other means acceptable to MCI WorldCom)
and Customer's advance payment of the cost of reinstituting such Switched Services. If Customer fails to make the required payment by the date set forth in the Suspension Notice, Customer will be
deemed to have canceled this Agreement as of the date set forth in the Suspension Notice which cancellation shall not relieve Customer for payment of the Cancellation Charge as described in
Section 2.

(B)Disconnection of ServiceIn the event Customer is in material breach of this Agreement, including without
limitation, failure to pay all undisputed charges due hereunder by the date stated in the Suspension Notice described in Subsection 7(A) above, MCI WorldCom shall have the right, after giving
Customer at least five (5) days prior written notice and opportunity to cure (which notice may be given instead of or in conjunction with the Suspension Notice described in Subsection 7(A)
above), and in addition to foreclosing any security interest MCI WorldCom may have, to (i) disconnect all or any portion the Switched Services being provided hereunder and/or terminate this
agreement; (ii) withhold billing information from Customer; and/or (iii) contact the End Users (for whom calls are originated and terminated solely over facilities comprising the MCI
WorldCom network) directly and bill such End Users directly until such time as MCI WorldCom has been paid in full for the amount owed by
Customer. If Customer fails to make payment by the date stated in the Suspension Notice and MCI WorldCom, after giving Customer five (5) days prior written notice, terminates this Agreement as
provided in this Section 7, such termination shall not relieve Customer for payment of the Cancellation Charge as described in Section 2 above.

8.Warranty.MCI WorldCom will use reasonable efforts under the
circumstances to maintain its overall network quality. The quality of Switched Services provided hereunder shall be consistent with telecommunications common carrier industry standards, government
regulations and sound business practices.MCI WORLDCOM MAKES NO OTHER WARRANTIES ABOUT THE SWITCHED SERVICES PROVIDED HEREUNDER, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
TO, ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE OR USE.

9.Liability; General Indemnity; Reimbursement.

(A)Limited LiabilityIN NO EVENT WILL EITHER PARTY HERETO BE LIABLE TO THE OTHER PARTY
FOR ANY INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL LOSSES OR DAMAGES, INCLUDING WITHOUT LIMITATION, LOSS OF REVENUE, LOSS OF CUSTOMERS OR CLIENTS, LOSS OF GOODWILL OR LOSS OR PROFITS ARISING IN
ANY MANNER FROM THIS AGREEMENT AND THE PERFORMANCE OR NONPERFORMANCE OF OBLIGATIONS HEREUNDER.

(B)General IndemnityIn the event parties other than Customer (e.g., Customer's End Users) shall have use of
the Switched Services through Customer, then Customer agrees to forever indemnify and hold MCI WorldCom, its affiliated companies and any third-party provider or operator of facilities employed in
provision of the Switched Services harmless from and against any and all claims, demands, suits, actions, losses, damages, assessments or payments which those parties may assert arising out of or

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relating to any defect in the Switched Services or MCI WorldCom's provision or nonprovision of Switched Services under this Agreement.

(C)ReimbursementCustomer agrees to reimburse MCI WorldCom for all reasonable costs and expenses incurred by
MCI WorldCom due to MCI WorldCom's direct participation (either as a party or witness) in any administrative, regulatory or criminal proceeding concerning Customer if MCI WorldCom's involvement in
said proceeding is based solely on MCI WorldCom's provision of Switched Services to Customer.

10.Force Majeure.If MCI WorldCom's performance of this
Agreement or any obligation hereunder is prevented, restricted or interfered with by causes beyond its reasonable control including, but not limited to, acts of God, fire, explosion, vandalism, cable
cut, storm or other similar occurrence, any law,
order, regulation, direction, action or request of the United States government, or state or local governments, or of any department, agency, commission, court, bureau, corporation or other
instrumentality of any one or more such governments, or of any civil or military authority, or by national emergency, insurrection, riot, war, strike, lockout or work stoppage or other labor
difficulties, or supplier failure, shortage, breach or delay, then MCI WorldCom shall be excused from such performance on a day-to-day basis to the extent of such restriction or interference. MCI
WorldCom shall use reasonable efforts under the circumstances to avoid or remove such causes of nonperformance and shall proceed to perform with reasonable dispatch whenever such causes are removed or
cease.

11.State Certification.Customer warrants that in all
jurisdictions in which it provides long distance services that require certification, it has obtained the necessary certification from the appropriate governmental authority and, if requested by MCI
WorldCom, agrees to provide proof of such certification acceptable to MCI WorldCom. In the event Customer is prohibited, either on a temporary or permanent basis, from continuing to conduct its
telecommunications operations in a given jurisdiction, Customer shall (i) immediately notify MCI WorldCom by facsimile, (ii) send written notice to MCI WorldCom within twenty-four
(24) hours of such prohibition, and (iii) take immediate steps to suspend or discontinue its use of Switched Services in such jurisdiction.

12.Interstate/Intrastate Service.Except with respect to
Switched Services specifically designated as intrastate Services or international Services, the rates provided to Customer in the applicable Attachments are applicable only to Switched Services if
such Switched Services are used for carrying interstate telecommunications (i.e., Switched Services subject to FCC jurisdiction). MCI WorldCom shall not be obligated to provide Switched Services with
end points within a single state or Switched Services which originate/terminate at points both of which are situated within a single state. In those states where MCI WorldCom is authorized to provide
intrastate service (i.e., telecommunications transmission services subject to the jurisdiction of state regulatory authorities), MCI WorldCom will, at its option, provide intrastate Switched Services
pursuant to applicable state laws, regulations and applicable tariff, if any, filed by MCI WorldCom with state regulatory authorities as required by applicable law.

13.Authorized Use of MCI WorldCom Name; Press Releases.Without
MCI WorldCom's prior written consent, Customer shall not (i) refer to itself as an authorized representative of MCI WorldCom whenever it refers to the Switched Services in promotional,
advertising or other materials, or (ii) use MCI WorldCom's logos, trade marks, service marks, or any variations thereof in any of its promotional, advertising or other materials. Additionally,
Customer shall provide to MCI WorldCom for its prior review and written approval, all promotions, advertising or other materials or activity using or displaying MCI WorldCom's name or the Services to
be provided by MCI WorldCom. In the event MCI WorldCom fails to provide its approval such promotion, advertising or other materials shall be deemed not approved. Customer agrees to change or correct,
at Customer's expense, any such material or activity which MCI WorldCom, in its sole judgment, determines to be inaccurate, misleading or otherwise objectionable for any reason. Customer is explicitly
authorized to only use the following

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statements in its sales literature or if in response to an inquiry by Customer's End User: (i) "Customer utilizes the MCI WorldCom network", (ii) "Customer utilizes MCI WorldCom's
facilities", (iii) "MCI WorldCom provides only the network facilities", and (iv) "MCI WorldCom is our network services provider". Except as specifically provided in this Section 13, the
parties further agree that any press
release, advertisement or publication generated by a party regarding this Agreement, the Services provided hereunder or in which a party desires to mention the name of the other party or the other
party's parent or affiliated company(ies), will be submitted to the non-publishing party for its written approval prior to publication.

14.Notices.Notices under this Agreement shall be in writing
and delivered to the person identified below at the offices of the parties as they appear below or as otherwise provided for by proper notice hereunder. Customer shall notify MCI WorldCom in writing
if Customer's billing address is different than the address shown below. The effective date for any notice under this Agreement shall be the date of actual receipt of such notice by the appropriate
party, notwithstanding the date of mailing or transmittal via hand delivery or facsimile.

If to MCI WorldCom:

MCI WORLDCOM Network Services, Inc.
6929 North Lakewood Avenue
Tulsa, Oklahoma 74117
Attn: Wholesale ServicesIf to Customer:

Ciera Network Systems, Inc.
2630 Fountainview
Houston, Texas 77057
Attn: Bob Livingston
Telephone No.: 713-914-3850
Fax No.: 713-914-3851


15.No-Waiver.No term or provision of this Agreement shall be
deemed waived and no breach or default shall be deemed excused unless such waiver or consent shall be in writing and signed by the party claimed to have waived or consented. A consent to waiver of or
excuse for a breach or default by either party, whether express or implied, shall not constitute a consent to, waiver of, or excuse for any different or subsequent breach or default.

16.Partial Invalidity; Government Action.

(A)Partial InvalidityIf any part of any provision of this Agreement or any other agreement, document or
writing given pursuant to or in connection with this Agreement shall be invalid or unenforceable under applicable law, rule or regulation, that part shall be ineffective to the extent of such
invalidity only, without in any way affecting the remaining parts of that provision or the remaining provisions of this Agreement. In such event, Customer and MCI WorldCom will negotiate in good faith
with respect to
any such invalid or unenforceable part to the extent necessary to render such part valid and enforceable.

(B)Government ActionUpon thirty (30) days prior notice, either party shall have the right, without liability
to the other, to cancel an affected portion of the Switched Service if any material rate or term contained in this Agreement and relevant to the affected Switched Service is substantially changed (to
the detriment of the terminating party) or found to be unlawful or the relationship between the parties hereunder is found to be unlawful by order of the highest court of competent jurisdiction to
which the matter is appealed, the FCC, or other local, state or federal government authority of competent jurisdiction. Provided, the 30-day notice required hereunder may be shortened as necessary if
such order goes into effect prior to thirty (30) days.

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17.Exclusive Remedies.Except as otherwise specifically
provided for herein, the remedies set forth in this Agreement comprise the exclusive remedies available to either party at law or in equity.

18.Use of ServiceUpon MCI WorldCom's acceptance of a Service
Request hereunder, MCI WorldCom will provide the Switched Services specified therein to Customer upon condition that such Switched Services shall not be used for any unlawful purpose. The provision of
Switched Services is not intended to and will not create a partnership or joint venture between the parties or result in a joint communications service offering to any third parties, and MCI WorldCom
and Customer agree that this Agreement, to the extent it is subject to FCC regulation, is an inter-carrier agreement which is not subject to the filing requirements of Section 211(a) of the
Communications Act of 1934 (47 U.S.C. §211(a)) as implemented in 47 C.F.R. §43.51.

19.Choice of Law; Forum.

(A)LawThis Agreement shall be construed under the laws of the State of Oklahoma without regard to choice of
law principles.

(B)ForumAny legal action or proceeding with respect to this Agreement may be brought in the Courts of the
State of Oklahoma in and for the County of Tulsa or the United States of America for the Northern District of Oklahoma. By execution of this Agreement, both Customer and MCI WorldCom hereby submit to
such jurisdiction, hereby expressly waiving whatever rights may correspond to either of them by reason of their present or future domicile. In furtherance of the foregoing, Customer and MCI WorldCom
hereby agree to service by U.S. Mail at the notice addresses referenced in Section 14. Such service shall be deemed effective upon the earlier of actual receipt or seven (7) days following the date of
posting.

20.Proprietary Information

(A)Confidential InformationThe parties understand and agree that the terms and conditions of this Agreement
(but not the existence thereof), all documents referenced herein (including invoices to Customer for Switched Services provided hereunder), communications between the parties regarding this Agreement
or the Switched Services to be provided hereunder (including price quotes to Customer for any services proposed to be provided or actually provided hereunder), as well as such information relevant to
any other agreement between the parties (collectively"Confidential Information"), are confidential as between Customer and MCI WorldCom.

(B)Limited DisclosureA party shall not disclose Confidential Information (unless subject to discovery or
disclosure pursuant to legal process), to any other party other than the directors, officers, and employees of a party or a party's agents including their respective attorneys, consultants, brokers,
lenders, insurance carriers or bona fide prospective purchasers who have specifically agreed in writing to nondisclosure of the terms and conditions hereof. Any disclosure hereof required by legal
process shall only be made after providing the non-disclosing party with notice thereof in order to permit the non-disclosing party to seek an appropriate protective order or exemption. Violation by a
party or its agents of the foregoing provisions shall entitle the non-disclosing party, at its option, to obtain injunctive relief without a showing of irreparable harm or injury and without bond.

(C)Survival of ConfidentialityThe provisions of this Section 20 will be effective as of the date of this
Agreement and remain in full force and effect for a period which will be the longer of (i) one (1) year following the date of this Agreement, or (ii) one (1) year from the termination or expiration of
all Services hereunder.

21.Successors and Assignment.This agreement shall be binding
upon and inure to the benefit of the parties hereto and their respective successors or assigns, provided, however, that Customer shall not assign or transfer its rights or obligations under this
Agreement without the prior written consent of

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MCI WorldCom, which consent shall not be unreasonably withheld or delayed, and further provided that any assignment or transfer without such consent shall be void.

22.General.

(A)Survival of TermsThe terms and provisions contained in this Agreement that by their sense and context are
intended to survive the performance thereof by the parties hereto shall so survive the completion of performance and termination of this Agreement, including, without limitation, provisions for
indemnification and the making of any and all payments due hereunder.

(B)HeadingsDescriptive headings in this Agreement are for convenience only and shall not affect the
construction of this Agreement.

(C)Industry TermsWords having well-known technical or trade meanings shall be so construed, and all listings
of items shall not be taken to be exclusive, but shall include other items, whether similar or dissimilar to those listed, as the context reasonably requires.

(D)Rule of ConstructionNo rule of construction requiring interpretation against the drafting party hereof
shall apply in the interpretation of this Agreement.

23.Entire Agreement.This Agreement consists of (i) all the terms and conditions
contained herein, and (ii) all documents incorporated herein specifically by reference. This Agreement constitutes the complete and exclusive statement of the understandings between the parties and
supersedes all prior and contemporaneous proposals and agreements (oral or written) between the parties relating to the Switched Services provided hereunder. No subsequent agreement between the
parties concerning the Switched Services (including further Attachments) shall be effective or binding unless it is made in writing and signed by Customer and MCI WorldCom.

IN WITNESS WHEREOF,the parties have executed this Telecommunications Services Agreement (Switched Services) as of the dates set forth
below which Agreement will be effective as described in the PET attached hereto.

|CIERA NETWORK SYSTEMS, INC. |  | MCI WORLDCOM NETWORK SERVICES, INC.
|--------------------------- |  | -----------------------------------
|By:                         |  | /s/R.W. LIVINGSTON(Signature)      
|R.W. Livingston(Print Name) |  | Peter M. Cassidy(Print Name)       
|CEO(Title)                  |  | VP, Wholesale Services(Title)      
|5/8/2000(Date)              |  | 5/11/00(Date)                      

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MCI WORLDCOM NETWORK SERVICES, INC.PROGRAM ENROLLMENT TERMS(Switched Services)

TheseProgram Enrollment Terms(the "PET") are made by and between
MCI WORLDCOM Network Services, Inc. (successor-in-interest to WorldCom Network Services, Inc.) ("MCI WorldCom") and Ciera Network Systems, Inc.
("Customer") and are a part of their Telecommunications Services Agreement for Switched Services. Capitalized terms not defined herein shall have the
meaning ascribed to them in the TSA, the applicable Attachment(s) or applicable tariffs referenced in such Attachment(s). Neither Customer nor MCI WorldCom shall be obligated with respect to the
Switched Services described in any Attachment, nor any other condition of such Switched Services until Customer has submitted and MCI WorldCom has accepted a Service Request with respect to the
particular Switched Service.

1.SERVICE TERM:

(A)  The
Service Term shall commence as of the Effective Date (as described below) and shall continue for a period of forty-four (44) months (the
"Service Term"). Upon expiration of the Service Term, the Switched Services in question will continue to be provided pursuant to the same terms and
conditions as are then in effect (including without limitation, the applicable rates, discounts and commitments, if any), subject to termination by either party upon thirty (30) days prior written
notice to the other party. MCI WorldCom will not be obligated to accept any Service Request under this Agreement if Customer's initial Service Request is (i) not submitted by Customer within
thirty (30) days of the Effective Date of this Agreement, and (ii) not subject to a Requested Service Date within ninety (90) days of the Effective Date.

(B)  For
purposes of this Agreement, the appropriate Effective Date as determined under this Subsection (B) will be filled in the area provided above by MCI WorldCom.
If Customer has an existing switched services agreement with MCI WorldCom or its affiliates, the "Effective Date" will be the 1st day of the month
following the later of (i) twenty-one (21) days after this Agreement has been fully executed by both parties, or (ii) Customer has received a satisfactory credit review and approval from
MCI WorldCom's Credit Department pursuant to Subsection 6(A) of the TSA, and all security documentation, if any, required by MCI WorldCom has been properly executed and delivered to MCI
WorldCom (collectively, the "Credit Review"). If Customer does not have an existing switched services agreement with MCI WorldCom or its affiliates, the
"Effective Date" will be the date this Agreement has been fully executed by both parties and the Credit Review has been completed.

2.MONTHLY REVENUE:For purposes of this Agreement, Customer's
"Monthly Revenue" will be comprised of (i) the aggregation of all of Customer's Switched Services Revenue as such term is described in each of
the applicable Attachments, PLUS (ii) Customer's Data Revenue (as defined herein) from MCI WorldCom. For purposes of this Agreement, Customer's "Data
Revenue" will be comprised of Customer's monthly recurring private line Interexchange Service charges (i.e., both Domestic and International) PLUS Customer's Monthly Port
Charges, Monthly CIR Charges and Monthly NNI Charges, if any, as are specifically described in an agreement for Frame Relay Services between MCI WorldCom and Customer. Customer's Monthly Revenue will
not include any pro rata charges, access charges, ancillary or special feature charges, such as, Authorization codes or CDR Tapes, or any other charges other than those identified by the relevant MCI
WorldCom invoice as charges specifically mentioned in this Section 2.

3.SERVICE INTERCONNECTIONS.

(A)  In
order to utilize (i) CLASSIC 2000 CARRIER TERMINATION Service, CLASSIC 2000 CARRIER ORIGINATION Service, TRANSCEND® 2000 CARRIER TERMINATION
Service, TRANSCEND® 2000 CARRIER ORIGINATION Service, ACCESS BASED BILLING CARRIER TERMINATION Service, ACCESS BASED BILLING CARRIER ORIGINATION Service, one or

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more full time dedicated connections between Customer's network and the MCI WorldCom network at one or more MCI WorldCom designated locations ("MCI WorldCom
POP") must be established ("Carrier Service Interconnection(s)"), (ii) CLASSIC 2000 END USER DEDICATED ACCESS Service (1+
or TOLL FREE), TRANSCEND® 2000 END USER DEDICATED ACCESS Service (1+ or TOLL FREE), or ACCESS BASED BILLING END USER DEDICATED ACCESS Service (1+ or TOLL FREE), one or more full time
dedicated connections between an End User's private branch exchange ("PBX") or other customer premise equipment and the MCI Worldcom network at one or
more MCI WorldCom POP(s) must be established ("Dedicated Service Interconnection(s)"), and (iii) PRISM I TERMINATION Service and ADVANCED TOLL
FREE Service, one or more full time dedicated connections between Customer's network and the MCI WorldCom network at one or more MCI WorldCom POP(s) must be established
("Carrier PLUS Service Interconnection(s)"). Each Carrier Service Interconnection, Carrier PLUS Service Interconnection and Dedicated Service
Interconnection shall be comprised of one or more dedicated access circuits, as the case may be. Carrier Service Interconnection(s), Carrier PLUS Service Interconnections and Dedicated Service
Interconnection(s) are collectively referred to as "Service Interconnections".

(B)  The
circuit(s) comprising each Service Interconnection to a MCI WorldCom POP shall be requested by Customer on the appropriate MCI WorldCom Service Request. Each Service
Request will describe (among other things) the MCI WorldCom POP to which a Service Interconnection is to be established, the Requested Service Date therefor, the type and quantity of circuits
comprising the Service
Interconnection and any charges and other information relevant thereto, such as, Customer's originating or terminating switch location, as the case may be. Such additional information may be obtained
from Customer or gathered by MCI WorldCom and recorded in Technical Information Sheets provided by MCI WorldCom.

(C)  Once
ordered, and unless otherwise provided for in this Agreement, Service Interconnection(s) or the circuits comprising each Service Interconnection may only be
canceled by Customer upon not less than thirty (30) days prior written notice to MCI WorldCom.

(D)  With
respect to a Carrier Service Interconnection or a Carrier PLUS Service Interconnection, Customer shall be solely responsible for establishing and maintaining each
Carrier Service Interconnection or Carrier PLUS Service Interconnection over facilities subject to MCI WorldCom's approval. With respect to Dedicated Service Interconnections, MCI WorldCom will
provision and maintain local access facilities between the End User location (i.e., PBX) and the MCI WorldCom POP, subject to any LEC charges plus other applicable terms and charges set forth in MCI
WorldCom's applicable tariffs (or the applicable tariffs of its affiliates), however, Customer may elect to be responsible for establishing each Dedicated Service Interconnection over facilities
subject to MCI WorldCom's approval. Service Interconnections shall be only comprised of DS-1 facilities unless otherwise provided for in the Service Request and agreed to in writing by MCI WorldCom.
If a Service Interconnection is proposed to be made via a local exchange carrier, MCI WorldCom will have the authority to direct Customer to utilize MCI WorldCom's entrance facilities or local serving
arrangement ("LSA") with the relevant local telephone operating company, and Customer will be subject to a non-discriminatory charge therefor from MCI
WorldCom. The monthly recurring charge relevant to Customer's use of LSA capacity shall be subject to upward adjustment by MCI WorldCom from time to time which adjustment, if any, shall not exceed the
rate that otherwise would be charged for the equivalent switched access capacity between the same points by the relevant local telephone operating company pursuant to its published charges for the
type of service in question.

(E)  If
other private line interexchange facilities are necessary to establish a Service Interconnection, and such facilities are requested from MCI WorldCom, such facilities
will be provided on an individual case basis.

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(F)  Commencing
with the second full calendar month following Start of Service for each circuit comprising a Service Interconnection (i.e., Carrier Service Interconnections,
Dedicated Service Interconnections and Carrier PLUS Interconnections) and thereafter, Customer will maintain Switched Services measured usage charges per DS-1 (or DS-1 equivalent circuit) of not less
than an average of * per calendar month/billing period ("Minimum Monthly Usage"). In the event Customer fails to obtain the required Minimum Monthly
Usage for the circuits comprising each Service Interconnection, MCI WorldCom will charge and Customer will pay the difference between the total combined number of DS-1s times the Minimum Monthly Usage
* and Customer's total combined Switched Services measured usage charges for the circuit(s) comprising the Service Interconnection in questions ("Minimum Usage
Charge"). MCI WorldCom CLASSIC 2000 CARRIER TERMINATION Service,
CLASSIC 2000 CARRIER ORIGINATION Service and CLASSIC 2000 END USER DEDICATED Service (1+ and TOLL FREE) minutes carried over the same Service Interconnection, TRANSCEND® 2000 TERMINATION
Service, TRANSCEND® 2000 CARRIER ORIGINATION Service and TRANSCEND® 2000 END USER DEDICATED ACCESS Service (1+ and TOLL FREE) minutes carried over the same Service
Interconnection, ACCESS BASED BILLING 2000 CARRIER TERMINATION Service, ACCESS BASED CARRIER ORIGINATION Service and ACCESS BASED BILLING END USER DEDICATED Service (1+ and TOLL FREE) carried over the
same Service Interconnection, or PRISM I TERMINATION Service and ADVANCED TOLL FREE Service minutes carried over the same Service Interconnection, shall be included in determining if Customer has met
the Minimum Monthly Usage requirement described herein.



(G)  DS-1
circuits comprising all Service Interconnections will be subject to a nonrecurring * per DS-1 switch port installation charge (provided the maximum charge hereunder
will be * for up to 28 DS-1s ordered at the same time), and DS-3 circuits comprising all Service Interconnections will be subject to a nonrecurring per DS-3 switch port installation charge as
determined on an individual case basis.

4.APPLICATION OF DISCOUNTS:

(A)  With
respect to Classic 2000, and ACCESS BASED BILLING products and services, after determining Customer's applicable Discount under the appropriate Attachment(s), the
applicable Discount will only be applied to Customer's Interstate Switched Services Revenue (including Alaska, Hawaii, the United States Virgin Islands, Puerto Rico, Guam and the Northern Marianas
Islandsunlessotherwise noted in an Attachment and including 1+ and Toll Free usageunlessotherwise
noted in an Attachment). With respect to TRANSCEND® 2000 products and services, after determining Customer's applicable Discount under the appropriate Attachment(s), the applicable
Discount will only be applied to Customer's Domestic Transport Charges and Customer's Extended Transport Charges to/from Extended Locations unless otherwise noted in an Attachment. With respect to
PRISM I TERMINATION Service and ADVANCED TOLL FREE Service, after determining Customer's applicable Discount under the appropriate Attachment, the applicable Discount will only be applied to
Customer's Interstate Switched Services Revenue unless otherwise noted in the applicable Attachment.

(B)  During
the Service Term, with respect to Classic 2000, TRANSCEND® 2000 and ACCESS BASED BILLING products and services, accumulated credits derived from the
applicable Discounts will be applied in arrears commencing with the first day of the month following the Effective Date, that is, the Discount will be applied to Customer's measured usage charges for
the preceding month (the"Discount Period"). The initial Discount Period shall include any partial calendar month following Start of Service, or such
other time basis as may be mutually determined by the parties. With respect to Classic 2000, TRANSCEND® 2000 and ACCESS BASED BILLING products and services each Discount will result in the
application of a credit obtained during the Discount Period to the MCI WorldCom invoice to Customer relevant to the billed measured Switched Service for the calendar month next following the
completion of each Discount Period, provided Customer has paid undisputed

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charges (including any late fees, if applicable) for that month and has not otherwise been subject to a Suspension Notice in accordance with the Agreement. Failure of Customer to comply with the
foregoing provision shall entitle MCI WorldCom to withhold any credit due Customer for the Discount Period in question until such charges (including late fees) have been paid in full.

(C)  With
respect to all other products and services (not covered by Subsection (B) above), each Discount, if applicable, will result in the application of a credit obtained
during the Discount Period to the MCI WorldCom invoice to Customer relevant to the billed measured Switched Service for the calendar month immediately following the completion of each Discount Period,
provided Customer has paid undisputed charges (including any late fees, if applicable) for that month and has not otherwise been subject to a Suspension Notice in accordance with the Agreement.
Failure of Customer to comply with the foregoing provision shall entitle MCI WorldCom to withhold any credit due Customer for the Discount Period in question until such charges (including late fees)
have been paid in full.

5.CUSTOMER'S MINIMUM REVENUE COMMITMENT:Commencing with the
first day of the ninth (9th) billing period following the Effective Date (as determined under Section 1 above) and continuing through the end of the Service Term (including any
extensions thereto) (the"Commitment Period"), Customer agrees to maintain, on a take-or-pay basis, Monthly Revenue (as defined in Section 2 above) of
at least * ("Customer's Minimum Revenue Commitment").

6.DEFICIENCY CHARGE:If the event Customer does not maintain
Customer's Minimum Revenue Commitment in any month during the Commitment Period (regardless of whether Customer has commenced using any or all of the Switched Services described herein), then for
those month(s) only, Customer will pay MCI WorldCom, in addition to charges due for Switched Services provided to Customer, the difference between Customer's Minimum Revenue Commitment and Customer's
actual Monthly Revenue (as described in Section 2 above) (the"Deficiency Charge"). The Deficiency Charge will be due at the same time payment is due
for Switched Services provided to Customer for the billing period in which the Deficiency Charge arises, or immediately in an amount equal to Customer's Minimum Revenue Commitment for the unexpired
portion of the Service Term, if MCI WorldCom terminates this Agreement based on Customer's default or if Customer terminates this Agreement pursuant to Section 2(A) of the TSA. It is agreed that MCI
WorldCom's damages in the event Customer fails to maintain Customer's Minimum Revenue Commitment shall be difficult or impossible to ascertain. The provision for a Deficiency Charge in this Section 6
is intended, therefore, to establish liquidated damages in the event Customer fails to maintain Customer's Minimum Revenue Commitment and is not intended as a penalty.

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7.SUSPENSION OF SERVICE.The parties agree to substitute the
first sentence of Subsection 7(A) of the TSA to read in its entirety as follows:

(A)Suspension of ServiceIn the event all undisputed charges due pursuant to MCI WorldCom's invoice are not
paid in full by the Due Date or disputed charges owed by Customer, if any, are not paid in full by the Alternate Due Date, MCI WorldCom shall have the right, after giving Customer at least five (5)
days prior written notice and opportunity to pay such charges within such 5-day period, to suspend all or any portion of the Switched Services to Customer ("Suspension
Notice") until such time (designated by MCI WorldCom in its Suspension Notice) as Customer has paid in fullallundisputed
charges then due to MCI WorldCom, including any late fees.

8.CDR MEDIA.The parties agree to substitute the first sentence
of Section IV of the Attachment for CLASSIC 2000 CARRIER ORIGINATION Service, the Attachment for CLASSIC 2000 SWITCHLESS/END USER DEDICATED Services, and the Attachment for CLASSIC 2000 CARRIER
TERMINATION Service, respectively, to read in their entirety as follows:



9.SPECIAL RATES:

(A)  Notwithstanding
anything to the contrary contained in the applicable Attachment(s) attached hereto, commencing as of the Effective Date (described in Section 1 above)
and continuing through the end of the Service Term, with respect to CLASSIC 2000 SWITCHLESS 1+ Service, CLASSIC 2000 SWITCHLESS TOLL FREE Service, CLASSIC 2000 END USER DEDICATED 1+ Service, CLASSIC
2000 END USER DEDICATED TOLL FREE Service, CLASSIC 2000 CARRIER ORIGINATION Service, and CLASSIC 2000 CARRIER TERMINATION Service, Customer will receive the special rates (the "Special Rates") shown in
Subparts (i) through (xix) below. The Special Rates contained in Subparts ii, iii, iv, v, ix, x, xi, and xii will be subject
to the applicable discount
percentage set forth in the applicable Attachment(s). The Special Rates contained in Subparts i, vi, vii, viii, xiii, xiv, xv,xvi, xvii, xviii, and xix will not be subject to the applicable discount
percentage set forth in the applicable Attachment(s). All other rates will be as set forth in the applicable Attachment(s).



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*



*



*

(B)  Notwithstanding
anything to the contrary contained in the TSA, MCI WorldCom reserves the right to modify the Special Rates described in Subsection (A) above (which
charge modifications shall not exceed then-current generally available MCI WorldCom charges for comparable services), upon not less than thirty (30) calendar days' prior notice to Customer (facsimile
being acceptable), which notice will state the effective date for the charge modification.

10.    RBOC ORIGINATION / TERMINATION.The parties agree to substitute the per minute surcharge contained in
Subsection I(E) of the Attachment for CLASSIC 2000 CARRIER ORIGINATION Service, Subsection I(E) of the Attachment for CLASSIC 2000 CARRIER TERMINATION Service, Subsection I(F) of the Attachment for
CLASSIC 2000 SWITCHLESS/END USER DEDICATED Services, respectively, will be *

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11.    ATTACHMENTS:This Agreement consists of the TSA, the PET and the following Attachment(s) [check
all that apply] and will include any additional Attachments agreed to by the parties after the Effective Date of this
Agreement:

|o |  | CLASSIC 2000 CARRIER TERMINATION Service (Schedules CL-A (2000), CL-B(2000), CL-C(2000))                                                    |  | o |  | CLASSIC 2000 CARRIER ORIGINATION Service (Schedules CL-A (2000), CL-B (2000))
|- |  | ------------------------------------------------------------------------------------------------------------------------------------------- |  | - |  | -----------------------------------------------------------------------------
|ý |  | CLASSIC 2000 SWITCHLESS/END USER DEDICATED Service (Schedule CL-A (2000), CL-B (2000), CL-C (2000), CL-D (2000))                           
|o |  | TRANSCEND® 2000 Services (Schedules TR-A(2000)                                                                                             
|o |  | TRANSCEND® UNIVERSAL INTERNATIONAL FREEPHONE NUMBER Service (UFIN)                                                                         
|o |  | TRANSCEND® INTERNATIONAL TOLL FREE SERVICES (ITFS)                                                                                         
|o |  | PRISM 1® CARRIER TERMINATION Service (Schedules PR-A, PR-B, PR-C and PR-D)                                                                  |  | o |  | ADVANCED TOLL FREE Service (Schedules PR-A, PR-B, PR-C and PR-D)             
|o |  | ACCESS BASED BILLING CARRIER TERMINATION Service (Schedules ABB-A, ABB-B, ABB-C)                                                           
|o |  | ACCESS BASED BILLING CARRIER ORIGINATION Service (Schedules ABB-D, ABB-E)                                                                  
|o |  | ACCESS BASED BILLING SWITCHLESS/END USER DEDICATED Service (Schedules ABB-A, ABB-B, ABB-C, ABB-D, ABB-E, ABB-F, ABB-G, ABB-H, ABB-I, ABB-J)
|o |  | OPERATOR SERVICES                                                                                                                           |  | o |  | DEBIT CARD Service                                                           
|o |  | CALLING CARD® Service                                                                                                                       |  | o |  | NETWORK CONFERENCING Service                                                 
|o |  | UNIVERSAL INTERNATIONAL FREE PHONE NUMBER Service (UIFN)                                                                                    |  | ý |  | INTERNATIONAL TOLL FREE SERVICES (ITFS)                                      
|o |  | LOCAL SERVICE                                                                                                                               |  | o |  | CIC TRANSLATION Service                                                      

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

8

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IN
WITNESS WHEREOF, the parties have executed these Switched Services Program Enrollment Terms.

|MCI WORLDCOM NETWORK SERVICES, INC. |                     | CIERA NETWORK SYSTEMS, INC.
|----------------------------------- | ------------------- | ---------------------------
|By:                                 | /s/PETER M. CASSIDY |                            
|(Signature)                         |                     | (Signature)                
|Peter M. Cassidy                    |                     | R. W. Livingston           
|(Print Name)                        |                     | (Print Name)               
|VP, Wholesale Services              |                     | CEO                        
|(Title)                             |                     | (Title)                    
|5/11/00                             |                     | 5/8/2000                   
|(Date)                              |                     | (Date)                     

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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WORLDCOM NETWORK SERVICES, INC.

ATTACHMENT FOR CLASSIC 2000 SWITCHLESS/END USER DEDICATED SERVICES

ThisAttachment for CLASSIC 2000 SWITCHLESS/END USER DEDICATED Servicesis made by and between Ciera Network
Systems, Inc. ("Customer") and MCI WorldCom Network Services, Inc. ("MCI WorldCom") and is a part of
their Telecommunications Services Agreement for Switched Services. Capitalized terms not defined herein shall have the meaning ascribed to them in the TSA, the PET or the applicable Attachment(s). NOTE: ANY MODIFICATIONS,
ADDITIONS OR DELETIONS FROM THIS ATTACHMENT WILL NOT BE EFFECTIVE UNLESS SPECIFICALLY SET FORTH IN THE PET.

During
the Service Term of the Agreement, MCI WorldCom will provide "CLASSIC 2000 SWITCHLESS/END USER DEDICATED Services" which include
the following services:

(a)  CLASSIC
2000 SWITCHLESS 1+ Service which is the origination (via individual telephone lines) and termination of calls solely over facilities comprising the MCI WorldCom
network, (i) to and from the locations below, and (ii) for the charges and applicable discounts set forth herein.

(b)  CLASSIC
2000 SWITCHLESS TOLL FREE Service which is the origination (via individual telephone lines) and termination of calls solely over facilities comprising the MCI
WorldCom network, (i) to and from the locations below, and (ii) for the charges and applicable discounts set forth herein.

(c)  CLASSIC
2000 END USER DEDICATED 1+ Service which is the termination of calls solely over facilities comprising the MCI WorldCom network which origination is via
dedicated access lines, (i) to and from the locations below, and (ii) for the charges and applicable discounts set forth herein.

(d)  CLASSIC
2000 END USER DEDICATED TOLL FREE Service which is the origination of Toll Free calls by MCI WorldCom solely over facilities comprising the MCI WorldCom network
which termination is via dedicated access lines, (i) to and from the locations below, and (ii) for the charges and applicable discounts set forth herein.

I.    TERMS AND CONDITIONS.

(A)Forecasts:Before Customer's initial order for CLASSIC 2000
SWITCHLESS/END USER DEDICATED Services, Customer shall provide MCI WorldCom with a forecast regarding the number of minutes expected to be terminated or originated in various LATAs and/or Tandems, so
as to enable MCI WorldCom, to configure optimum network arrangements.In the event Customer's traffic volumes result in a lower than industry standard completion rate or
otherwise adversely affect the MCI WorIdCom Network, MCI WorldCom reserves the right to block the source of such adverse traffic at any time.Customer will provide MCI WorldCom
with additional forecasts from time to time upon MCI WorldCom's request which shall not be more frequent than once every three (3) months.

(B)Start of Service:Start of Service for (i) CLASSIC 2000
SWITCHLESS 1+ Service will be on an ANI by ANI basis concurrently with the activation of each ANI to be served, (ii) CLASSIC 2000 SWITCHLESS TOLL FREE Service will be on a Toll Free Number by Toll
Free Number basis concurrently with the activation of each Toll Free Number to be served, and (iii) CLASSIC 2000 END USER DEDICATED 1+ Service and CLASSIC 2000 END USER DEDICATED TOLL FREE Service
will be concurrently with the activation of each circuit comprising a Dedicated Service Interconnection (as defined in the PET) relevant to such Service.

(C)Submission of ANIs:After MCI WorldCom's receipt and
verification of a valid Service Request for CLASSIC 2000 SWITCHLESS 1+ Service or CLASSIC 2000 END USER DEDICATED 1+ Service requiring a change in the primary interexchange carrier
("PIC"), MCI WorldCom agrees to (i) submit the ANI(s) relevant to such Service Requests to the following local exchange carriers

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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("LECs") (with which MCI WorldCom currently has electronic interface capabilities) within ten (10) days: Ameritech, Bell Atlantic, BellSouth, Nynex,
Pacific Bell, Southwestern Bell, US West, GTE and United, and (ii) submit the ANI(s) relevant to such Service Requests to those LECs with which MCI WorldCom does not have electronic interface
capabilities within a reasonable time.

(D)Limitation of Origination and Termination Locations:



(E)Billing Increments:All calls (excluding California,
Intra.LATA and California intrastate calls and calls to/from International Locations, Canada and Mexico) will be billed in * increments . and subject to * minimum charge. California IntraLATA and
California intrastate calls will be billed in * increments and subject to an * charge. Calls to/from International Locations, Canada and Mexico will be billed in * and subject to a * minimum charge.
All calls will be billed utilizing Hardware Answer Supervision where available commencing with Customer's switch wink or answer back. If Customer is found to be non-compliant in passing back
appropriate answer supervision, i.e., answer back, MCI WorldCom reserves the right to suspend CLASSIC 2000 SWITCHLESS TOLL FREE Service and/or CLASSIC 2000 END USER DEDICATED TOLL FREE Service or deny
requests by Customer for additional Service until appropriate compliance is established.

(F)RBOC TERMINATION/Origination:Following Start of Service for
CLASSIC 2000 END USER DEDICATED 1 + and TOLL FREE Service, Customer will maintain at least * of the minutes of traffic (during any calendar month or pro rata portion thereof) for termination or
origination in a Tandem owned and operated by a Regional Bell Operating Company ("RBOC Terminations/Originations") and subject to such RBOC's tariffed
access charges. MCI WorldCom shall have the right to apply a * per minute surcharge to the number of minutes by which Non-RBOC Terminations/Originations exceed * of total monthly minutes for each of
the following Services: CLASSIC 2000 END USER DEDICATED 1+ and TOLL FREE Service.

(G)Presubscribed Interexchange Carrier Charge (PICC):MCI
WorldCom will charge Customer for any LEC-assessed presubscribed interexchange carrier charge ("PICC Charge") which PICC Charge will be reasonably
determined by MCI WorldCom as of a date certain each month (the "PICC Charge Determination Date"). Customer's PICC Charge will be determined as of the
PICC Charge Determination Date and will be based on the same criteria for which MCI WorldCom is assessed such charge by the LEC (e.g., number and type of Customer's End Users (i.e., residential or
business) as well as the type of line associated with each such End User (i.e., single line, secondary line or multi-line). This Subparagraph (G) will be deemed to include any other similar additional
charges assessed by a LEC during the Service Term of this Agreement (i.e., charges for which MCI WorldCom is not currently being assessed).

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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(H)Toll Free Numbers:



(I)Enhanced Toll Free Services and Routing Options:The
following Toll Free identification services and routing options (collectively, "Enhanced Toll Free Services") are available from MCI WorldCom:



*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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(J)RespOrg Services:Responsible Organization Services
(relevant to TOLL FREE Numbers) if provided by MCI WorldCom will be provided by MCI WorldCom pursuant to MCI WorldCom's applicable tariffs (or the applicable tariffs of its affiliates).

(K)Payphone Surcharge:In the event MCI WorldCom is required to
compensate payphone service providers (PSPs) for toll-free or access code calls which originate from payphones (including without limitation, any Order adopted by the FCC)
("Payphone Surcharge"), MCI WorldCom will charge and Customer agrees to pay MCI WorldCom the amount of the Payphone Surcharge which is required to be
paid by MCI WorldCom.

II.    CLASSIC 2000 SWITCHLESS/END USER DEDICATED SERVICE CHARGES.



*



*

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

4

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*



*



*



*



*



*



*



*



*

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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(iii)    INTRASTATE (NOT SUBJECT TO DISCOUNT).

*

(iv)    CANADA
(NOT SUBJECT TO DISCOUNT).

*



(v)    MEXICO
(NOT SUBJECT TO DISCOUNT).

*

(vi)    INTERNATIONAL
(NOT SUBJECT TO DISCOUNT).

*

(E)CLASSIC 2000 END USER DEDICATED TOLL FREE Service

(i)    INTERSTATE

*

(ii)    INTERSTATEExtended

*

(iii)    INTRASTATE
(NOT SUBJECT TO DISCOUNT).

*

(iv)    CANADA
(NOT SUBJECT TO DISCOUNT).

*

(F)CLASSIC 2000 DIRECTORY ASSISTANCE (NOT SUBJECT TO DISCOUNT).

*

III.  DISCOUNTS.

Commencing with the Effective Date and continuing through the end of the Service Term (includingany applicable
extensions thereto), Customer's discount percentage for CLASSIC 2000 SWITCHLESS/END USER DEDICATED Services (the "Discount") will be determined under
the Discount Schedule shown below based *

*

*


IV.  CDR MEDIA.

MCI WorldCom will provide Call Detail Records (CDRs) for MCI WorldCom's Switched Services in machine readable form in one of several magnetic tape formats
(selected by Customer on Customer's Service Request) ("CDR Media"). CDR Media provided hereunder (i) monthly is provided at no charge, (ii) weekly is
subject to a recurring monthly charge of *, and (iii) daily is subject to the applicable non-recurring Installation Charge as described below (plus all leased-line and equipment costs necessary to
implement Daily CDR Media which will be determined on an individual case basis depending on Customer's specific configuration).

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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*

*

IN
WITNESS WHEREOF, authorized parties on behalf of their respective entities have initialed this Attachment for CLASSIC 2000 SWITCHLESS/END USER DEDICATED Services as of the date shown
below.

|CIERA NETWORK SYSTEMS, INC. |  | MCI WORLDCOM NETWORK
SERVICES, INC.
|--------------------------- |  | -----------------------------------
|Customer's Initials         |  | [illegible]                        

|Date: |  | 5/8/2000 |  | Date: |  | 5/11/00
|----- |  | -------- |  | ----- |  | -------

ATTACHMENTS:



*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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WORLDCOM NETWORK SERVICES, INC.

ATTACHMENT FOR CLASSIC 2000 CARRIER TERMINATION SERVICE

ThisAttachment for CLASSIC 2000 CARRIER TERMINATION Serviceis made by and between Ciera Network Systems, Inc.
("Customer") and WorldCom Network Services, Inc. ("MCI WorldCom") and is a part of their
Telecommunications Services Agreement for Switched Services. Capitalized terms not defined herein shall have the meaning ascribed to them in the TSA, the PET or the applicable Attachment(s). NOTE: ANY MODIFICATIONS, ADDITIONS
OR DELETIONS FROM THIS ATTACHMENT WILL NOT BE EFFECTIVE UNLESS SPECIFICALLY SET FORTH IN THE PET.

During
the Service Term of the Agreement, MCI WorldCom will provide "CLASSIC 2000 CARRIER TERMINATION Service" which is MCI WorldCom's
termination of calls received from Customer's Service Interconnection(s) (as defined in the PET), (i) to and from the locations below, and (ii) for the charges and applicable discounts set forth
herein.

I.    TERMS AND CONDITIONS.

(A)Forecasts:Before Customer's initial order for CLASSIC 2000
CARRIER TERMINATION Services, Customer shall provide MCI WorldCom with a forecast regarding the number of minutes expected to be terminated in various LATAs and/or Tandems, so as to enable MCI
WorldCom to configure optimum network arrangements.In the event Customer's traffic volumes result in a lower than industry standard completion rate or otherwise adversely
affect the MCI WorldCom Network, MCI WorldCom reserves the right to block the source of such adverse traffic at any time.Customer will
provide MCI WorldCom with additional forecasts from time to time upon MCI WorldCom's request which shall not be more frequent than once every three (3) months.

(B)Start of Service:Start of Service for CLASSIC 2000 CARRIER
TERMINATION Service will be concurrent with the activation of each circuit comprising a Carrier Service Interconnection (as defined in the PET) relevant to CLASSIC 2000 CARRIER TERMINATION Service.

(C)Limitation of Origination and Termination Locations:CLASSIC
2000 CARRIER TERMINATION Service may be originated from any MCI WorldCom POP and terminated to any direct dialable location worldwide.

(D)Billing Increments:All calls (excluding California
IntraLATA and California intrastate calls and calls to International Locations, Canada and Mexico) will be billed in six (6) second increments and subject to a * minimum charge. California IntraLATA
and California intrastate calls will be billed in * increments and subject to an * minimum charge. Calls to International Locations, Canada and Mexico will be billed in * increments and subject to a *
minimum charge. All calls will be billed utilizing Hardware Answer Supervision where available.

(E)RBOC Termination:Following Start of Service for CLASSIC
2000 CARRIER TERMINATION Service, Customer will maintain at least * of the minutes of CLASSIC 2000 CARRIER TERMINATION Service traffic (during any calendar month or pro rata portion thereof) for
termination in a Tandem owned and operated by a Regional Bell Operating Company ("RBOC Terminations") and subject to such RBOC's tariffed access
charges. MCI WorldCom shall have the right to apply a * per minute surcharge to the number of minutes by which Non-RBOC Terminations exceed * of total monthly minutes for Customer's CLASSIC 2000
CARRIER TERMINATION Service.

(F)PIU CERTIFICATION:With respect to a Carrier Service
Interconnection as defined in the PET, absent the automatic number identification ("ANI") of the calling party, Customer shall provide MCI WorldCom with
a written certification (the "Certification") of the percentage of interstate (including international) and interstate minutes of use relevant to the
minutes of traffic to be terminated in the same state in which the MCI WorldCom POP is located to which the Carrier Service

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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Interconnection is made. This Certification shall be provided by Customer prior to Start of Service for any Carrier Service Interconnection and may be modified from time to time by Customer and
subject to recertification upon the request of MCI WorldCom which requests shall not be made unilaterally by MCI WorldCom more than once each calendar quarter. Any such modification(s) or
Certification(s) shall be effective as of the first day of any calendar month and following at least forty-five (45) days notice from Customer. In the event Customer fails to make such Certification,
the relevant minutes of use will be deemed to be subject to the Intrastate Rates described herein. In the event MCI WorldCom or any other third party requires an audit of MCI WorldCom's
interstate/intrastate minutes of traffic, Customer agrees to cooperate in such audit at its expense and make its call detail records, billing systems and other necessary information reasonably
available to MCI WorldCom or any third party
solely for the purpose of verifying Customer's interstate/intrastate minutes of traffic. Customer agrees to indemnify MCI WorldCom for any liability MCI WorldCom incurs in the event Customer's
Certification is different than that determined by the audit.

II.    CLASSIC 2000 CARRIER TERMINATION SERVICE CHARGES.

(A)For purposes of this Attachment, Customer's "Switched Services Revenue"
will be comprised of Customer's gross (i.e., prior to the application of discounts) measured and per call Switched Service charges described below (i.e., both domestic and international).

(B)Rates Per Minute.



III.  DISCOUNTS.



*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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IV.  CDR MEDIA.



*

IN
WITNESS WHEREOF, authorized parties on behalf of their respective entities have initialed this Attachment for CLASSIC 2000 CARRIER TERMINATION Service as of the date shown below.

|Ciera Network Systems, Inc. |  | WORLD NETWORK SERVICES, INC.
|--------------------------- |  | ----------------------------
|Customer's Initials         |  | [ILLEGIBLE]                 
|Date:                       |  | 5/8/2000                    

ATTACHMENTS:



*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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Schedule CL-A  Classic Millennium SuperSaver LATA's

*

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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Schedule CL-B  Classic Millenium Premium LATA's

*

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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Schedule CL-C  Classic Millennium International Rates

* 6 pages

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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MCI WORLDCOM NETWORK SERVICES, INC.
CLASSIC o SWITCHED SERVICESATTACHMENT FOR INTERNATIONAL TOLL FREE SERVICES ("ITFS")

ThisAttachment for International Toll Free Services(the"ITFS
Attachment") is made by and between MCI WorldCom Network Services, Inc. ("MCI WorldCom") and Ciera Network Systems, Inc.
("Customer") and is a part of their Telecommunications Services Agreement for Switched Services. Capitalized terms not defined herein shall have the
meaning ascribed to them in the TSA, the Service Schedule or the applicable Rate and Discount Schedule.



*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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IN WITNESS WHEREOF,the parties have executed these Classic/TRANSCEND® Switched Services Attachment for International Toll
Free Service.

|CIERA NETWORK SYSTEMS, INC.                 |  | MCI WORLDCOM NETWORK SERVICES, INC.             
|------------------------------------------- |  | ------------------------------------------------
|By:                                         |  | /s/R.W. LIVINGSTON(Signature)                   
|R.W. Livingston(Print Name)                 |  | Peter M. Cassidy(Print Name)                    
|CEO   
                     5/8/2000(Title) |  | VP, Wholesale
Services            5/11/00(Title)

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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Schedule 1ITFS (Classic)

Schedule 1  Classic Millennium ITFS Rates

*

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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Schedule 1ITFS (Classic)

Schedule 1  Classic Millennium ITFS Rates

*

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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WORLDCOM NETWORK SERVICES, INC.    ATTACHMENT FOR CLASSIC 2000 CARRIER ORIGINATION SERVICE

ThisAttachment for CLASSIC 2000 CARRIER ORIGINATION Serviceis made by and between Ciera Network Systems, Inc.
("Customer") and WorldCom Network Services, Inc. ("MCI WorldCom") and is a part of their
Telecommunications Services Agreement for Switched Services. Capitalized terms not defined herein shall have the meaning ascribed to them in the TSA, the PET or the applicable Attachment(s). NOTE: ANY MODIFICATIONS, ADDITIONS
OR DELETIONS FROM THIS ATTACHMENT WILL NOT BE EFFECTIVE UNLESS SPECIFICALLY SET FORTH IN THE PET.

During
the Service Term of the Agreement, MCI WorldCom will provide "CLASSIC 2000 CARRIER ORIGINATION Service" which is MCI WorldCom's
origination of Toll Free calls by MCI WorldCom and the termination of such calls to Customer's Service Interconnection(s), (i) to and from the locations below, and (ii) for the charges and applicable
discounts set forth herein.

I.    TERMS AND CONDITIONS.

(A)Forecasts:Before Customer's initial order for CLASSIC 2000
CARRIER ORIGINATION Services, Customer shall provide MCI WorldCom with a forecast regarding the number of minutes expected to be originated in various LATAs and/or Tandems, so as to enable MCI
WorldCom to configure optimum network arrangements.In the event Customer's traffic volumes result in a lower than industry standard completion rate or otherwise adversely
affect the MCI WorldCom Network, MCI WorldCom
reserves the right to block the source of such adverse traffic at any time.Customer will provide MCI WorldCom with additional forecasts from time to time upon MCI WorldCom's
request which shall not be more frequent than once every three (3) months.

(B)Start of Service:Start of Service for CLASSIC 2000 CARRIER
ORIGINATION Service will be concurrent with the activation of each circuit comprising a Carrier Service Interconnection (as defined in the PET) relevant to CLASSIC 2000 CARRIER ORIGINATION Service.

(C)Limitation of Origination and Termination Locations:CLASSIC
2000 CARRIER ORIGINATION Service may be originated from locations in the 48 contiguous United States, Hawaii, Alaska, the US Virgin Islands, Puerto Rico, Guam, the Northern Marianas Islands and Canada
and terminated to any Customer-designated Carrier Service Interconnection in the 48 contiguous United States.

(D)Billing Increments:All Calls (excluding California
intraLATA and California intrastate calls and calls to/from Canada) will be billed in * increments and subject to a * minimum charge. California IntraLATA and California intrastate calls will be
billed in * increments and subject to an * minimum charge. California intraLATA and California intrastate calls will be billed in * increments and subject to an * minimum charge, and (ii) calls
to/from Canada will be billed in * increments and subject to a * minimum charge. All calls will be billed utilizing Hardware Answer Supervision where available commencing with Customer's switch wink
or answer back. If Customer is found to be non-compliant in passing back appropriate answer supervision, i.e., answer back, MCI WorldCom reserves the right to suspend CLASSIC 2000 CARRIER ORIGINATION
Service or deny requests by Customer for additional Service until appropriate compliance is established.

(E)RBOC Origination:Following Start of Service for CLASSIC
2000 CARRIER ORIGINATION Service, Customer will maintain at least * of the minutes of CLASSIC 2000 CARRIER ORIGINATION Service traffic (during any calendar month or pro rata portion thereof) for
origination in a Tandem owned and operated by a Regional Bell Operating Company ("RBOC Originations") and subject to such RBOC's tariffed access
charges. MCI WorldCom shall have the

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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right to apply a * per minute surcharge to the number of minutes by which Non-RBOC Originations exceed * of total monthly minutes for Customer's CLASSIC 2000 CARRIER ORIGINATION Service.

(F)PIU CERTIFICATION:With respect to a Carrier Service
Interconnection as defined in the PET, absent the automatic number identification ("ANI") of the calling party, Customer shall provide MCI WorldCom with
a written certification (the "Certification") of the percentage of interstate (including international) and intrastate minutes of use relevant to the
minutes of traffic to be terminated in the same state in which the MCI WorldCom POP is located to which the Carrier Service Interconnection is made. This Certification shall be provided by Customer
prior to Start of Service for any Carrier Service Interconnection and may be modified from time to time by Customer and subject to recertification upon the request of MCI WorldCom which requests shall
not be made unilaterally by MCI WorldCom more than once each calendar quarter. Any such modification(s) or Certification(s) shall be effective as
of the first day of any calendar month and following at least forty-five (45) days notice from Customer. In the event Customer fails to make such Certification, the relevant minutes of use will be
deemed to be subject to the Intrastate Rates described herein. In the event MCI WorldCom or any other third party requires an audit of MCI WorldCom's interstate/intrastate minutes of traffic, Customer
agrees to cooperate in such audit at its expense and make its call detail records, billing systems and other necessary information reasonably available to MCI WorldCom or any third party solely for
the purpose of verifying Customer's interstate/intrastate minutes of traffic. Customer agrees to indemnify MCI WorldCom for any liability MCI WorldCom incurs in the event Customer's Certification is
different than that determined by the audit.

(G)Payphone Surcharge:In the event MCI WorldCom is required to
compensate payphone service providers (PSPs) for toll-free or access code calls which originate from payphones (including without limitation, any Order adopted by the FCC)
("Payphone Surcharge"), MCI WorldCom will charge and Customer agrees to pay MCI WorldCom the amount of the Payphone Surcharge which is required to be
paid by MCI WorldCom.

(H)Toll Free Numbers:



*
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(I)Enhanced Toll Free Services and Routing Options:The
following Toll Free identification services and routing options (collectively, "Enhanced Toll Free Services") are available from MCI WorldCom:



*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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II.    CLASSIC 2000 CARRIER ORIGINATION SERVICE CHARGES.



*



*



*



*

III.  DISCOUNTS.

Commencing with the Effective Date and continuing through the end of the Service Term (includingany applicable
extensions thereto), Customer's discount percentage for CLASSIC 2000 ORIGINATION Service (the "Discount") will be determined under the Discount Schedule
shown below based on Customer's actual Monthly Revenue for such month. Throughout the Service Term, Customer will automatically receive the next higher (or lower) Discount when Customer's eligible
Monthly Revenue (as defined in the PET) reaches the next level (or falls below a level).

|* |  | *
|- |  | -

IV.  CDR MEDIA.

MCI WorldCom will provide Call Detail Records (CDRs) for MCI WorldCom's Switched Services in machine readable form in one of several magnetic tape or optical
media formats (selected by Customer on Customer's Service Request) ("CDR Media"). CDR Media provided hereunder (i) monthly is provided at no charge,
(ii) weekly is subject to a recurring monthly charge of *, and (iii) daily is subject to the applicable non-recurring Installation Charge as described below (plus all leased-line and equipment costs
necessary to implement Daily CDR Media which will be determined on an individual case basis depending on Customer's specific configuration).

*

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

4

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IN
WITNESS WHEREOF, authorized parties on behalf of their respective entities have initialed this Attachment for CLASSIC 2000 CARRIER ORIGINATION Service as of the date shown below.

|Ciera Network Systems, Inc.     |          | WORLDCOM NETWORK SERVICES, INC.
|------------------------------- | -------- | -------------------------------
|                                |          |                                
|Customer's Initials [Illegible] |          | MCI WorldCom's Initials P.M.C. 
|Date:                           | 5/8/2000 |                                
|                                |          |                                

ATTACHMENTS



*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

5

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MCI WORLDCOM NETWORK SERVICES, INC.

AMENDMENT NO. 1

This Amendment No. 1 is made this 26 day of September, 2000, by and between Ciera Network Systems, Inc.
("Customer") and MCI WORLDCOM Network Services, Inc. (successor in interest to WorldCom Network Services, Inc.) ("MCI
WorldCom"), to those certain Program Enrollment Terms (the "PET") and the applicable Attachment(s) (the
"Attachment(s)to that certain Telecommunications Services Agreement, more particularly described as TSA # CNS-000524 made by and between Customer and
MCI WorldCom and dated May 8, 2000 (the "TSA"). In the event of any conflict between the terms of the TSA, the Attachment(s), or the PET and the
terms of this Amendment No. 1, the terms of this Amendment No. 1 shall control. The TSA, the PET, the Attachment(s), and this Amendment No. 1 are collectively referred to as the
"Agreement".

Customer
and MCI WorldCom agree for good and valuable consideration, intending legally to be bound, as follows:

A.SPECIAL RATES:Commencing, and effective, on a date to be chosen by MCI WorldCom in its sole discretion, but
within ten (10) business days after execution of this Amendment No. 1 by MCI WorldCom, and continuing through the end of the Service Term (including any extensions thereto), Subpart (xvii) of
Subsection 9(A) of the PET will be replaced in its entirety with the following:



*

B.SPECIAL RATES:Commencing, and effective, on a date to be chosen by MCI WorldCom in its sole discretion, but
within ten (10) business days after execution of this Amendment No. 1 by MCI WorldCom, and continuing through the end of the Service Term (including any extensions thereto), the following Subpart (xx)
will be added to Subsection 9(A) of the PET:



C.OTHER TERMS AND CONDITIONS:Except as specifically amended or modified herein, the terms and conditions of
the Agreement will remain in full force and effect throughout the Service Term and any extensions thereto.

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

1

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IN WITNESS WHEREOF, Customer and MCI WorldCom have entered into this Amendment No. 1 on the date first written above.

|MCI WORLDCOM NETWORK SERVICES, INC. |             | CIERA NETWORK SYSTEMS, INC.
|----------------------------------- | ----------- | ---------------------------
|By:                                 |             |                            
|                                    | (Signature) |                            
|                                    |             |                            
|(Print Name)                        |             | (Print Name)               
|                                    |             |                            
|(Title)                             |             | (Title)                    
|                                    |             |                            
|(Date)                              |             | (Date)                     

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

2

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MCI WORLDCOM NETWORK SERVICES, INC.

AMENDMENT NO. 2

This Amendment No. 2 ("Amendment No. 2") is made this 14th day of March, 2001, by and between Ciera
Network Systems, Inc. ("Customer") and MCI WORLDCOM Network Services, Inc. (successor-in-interest to WorldCom Network Services, Inc.)
("MCI WorldCom"), to those certain Program Enrollment Terms (the "PET"), to that certain
Telecommunications Services Agreement more particularly described as TSA# CNS-000525 (the "TSA"), made by and between Customer and MCI WorldCom dated
May 8, 2000, including that certain Amendment No. 1 dated September 26, 2000. In the event of any conflict between the terms of the TSA, the PET, Amendment No. 1 or any
applicable Attachment and the terms of this Amendment No. 2, the terms of this Amendment No. 2 shall control. The TSA along with the PET, Amendment No. 1, all applicable
Attachment(s), and this Amendment No. 2 shall collectively be referred to as the "Agreement". Capitalized terms not defined herein shall have the
meaning ascribed to them in other documents referenced herein.

In
consideration of good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties agree as follows:

1.SERVICE TERM.As of March 1, 2001, the parties agree to substitute Section 1 of the PETto read in its entirety as
follows:



2.CUSTOMER'S MINIMUM REVENUE COMMITMENT.As of March 1, 2001, the parties agree to substitute Section 5
of the PET to read in its entirety as follows:



3.OTHER TERMS AND CONDITIONS.Except as specifically amended or modified herein, the terms and conditions of
the Agreement will remain in full force and effect throughout the Service Term and any extensions thereof.

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

1

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IN WITNESS WHEREOF, the parties have entered into this Amendment No. 2 on the date first written above.

|CIERA NETWORK SYSTEMS, INC. |                       | MCI WORLDCOM NETWORK SERVICES, INC.
|--------------------------- | --------------------- | -----------------------------------
|By:                         | /s/ Robert Livingston |                                    
|                            | (Signature)           |                                    
|Robert W. Livingston        |                       | Peter M. Cassidy                   
|(Print Name)                |                       | (Print Name)                       
|CEO                         |                       | VP, Wholesale Services             
|(Title)                     |                       | (Title)                            
|3-14-2001                   |                       | 3/23/01                            
|(Date)                      |                       | (Date)                             

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

2

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MCI WORLDCOM NETWORK SERVICES, INC.

ATTACHMENT FOR CALLING CARD SERVICE

ThisAttachment for CALLING CARD Serviceis made by and between Ciera Network Systems, Inc.
("Customer") and MCI WORLDCOM Network Services, Inc. ("MCI WorldCom") and is a part of their
Telecommunications Services Agreement for Switched Services. Capitalized terms not defined herein shall have the meaning ascribed to them in the TSA, the PET, the applicable Attachment(s) or the
Tariff (as defined below), whichever is applicable.NOTE: ANY MODIFICATIONS, ADDITIONS OR DELETIONS FROM THIS ATTACHMENT WILL NOT BE EFFECTIVE UNLESS SPECIFICALLY SET FORTH IN
THE PET.

During
the Service Term of the Agreement, MCI WorldCom will provide "CALLING CARD Service" which is accessed only by dialing the unique
toll free access number * assigned by MCI WorldCom to Customer. With respect to International Origination CALLING CARD Service and applicable Star (*) Features, this Attachment incorporates by
reference the terms of MCI Tariff FCC No. 1 (the "Tariff"), which may be modified from time to time by MCI WorldCom in accordance with law and thereby
affect the Services furnished Customer hereunder, except that the terms and conditions contained in the TSA, the PET or this Attachment shall supplement or, to the extent inconsistent, supersede the
Tariff terms and conditions. For purposes of this Attachment, references to "MCI FEATURE CARD Service (Option T)" or "Connections Card Service" will be deemed to refer to "CALLING CARD Service". *
ACCESS NUMBER MAY BE provided by Customer.

I.    CALLING CARD SERVICE CHARGES.



*



*



*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

1

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II.    CREDITS/DISCOUNTS.



*



III.  CALLING CARD SERVICE SURCHARGES.



*

IV.  FULFILLMENT.

If Customer elects to use MCI WorldCom for fulfillment, Customer shall pay MCI WorldCom the fulfillment charges associated with Customer's usage of CALLING CARD
Service, as determined by MCI WorldCom.

V.    SET UP CHARGES.

Customer agrees to pay * for every instance of special branding (i.e., greeting and/or closing) requested by Customer in connection with CALLING CARD Service.

VI.  FRAUD DETECTION PROCEDURES.

Customer shall be responsible for any and all fraud associated with its usage of CALLING CARD Service, except as set forth below:



*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

2

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(4)  In
the event MCI WorldCom is unable to contact Customer of suspected abuse of the CALLING CARD Service, in order to minimize potential abuse, MCI WorldCom may deactivate
any calling card which has exceeded established fraud detection parameters or which MCI WorldCom has reason to believe is or may be used fraudulently. In such event MCI WorldCom will have no liability
to Customer or any End User in connection with such deactivation or failure to deactivate such calling card.

VII. FEATURE SERVICES.

(A)Customer agrees to pay the charges set forth below with respect to the features shown ("Feature
Services"):



*



*



*

*



*



*



*

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

3

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*

(B)The feature charges described in Subsection VII.(A) above will be subject to the following discounts *.

*

(C)*

IN
WITNESS WHEREOF, authorized parties on behalf of their respective entities have initialed this Attachment for CALLING CARD Service as of the date shown below.

|CIERA NETWORK SYSTEMS, INC.         |           | MCI WORLDCOM NETWORK SERVICES, INC.
|----------------------------------- | --------- | -----------------------------------
|Customer's Initials /s/ [ILLEGIBLE] |           | MCI WorldCom's
Initials:           
|Date:                               | 9-26-2000 |                                    
|                                    |           |                                    

ATTACHMENTS:



*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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Schedule CC-A

|Calling Card International Termination Rates
|--------------------------------------------
|
|* 5 pages                                   

MCI
WorldComPROPRIETARY
Not for use or disclosure outside MCI WorldCom
except under written agreement

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

5

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Schedule CC-B

|Calling Card International Origination Rate
|-------------------------------------------
|
|* 3 pages                                  

MCI
WorldComPROPRIETARY
Not for use or disclosure outside MCI WorldCom
except under written agreement

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

6

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MCI WORLDCOM NETWORK SERVICES, INC.ATTACHMENT FOR UNIVERSAL INTERNATIONAL FREEPHONE NUMBER ("UIFN") SERVICE

ThisAttachment for Universal International Freephone Number (UIFN) Service(the "UIFN
Attachment") is made this 26 day of September, 2000, by and between MCI WORLDCOM Network Services, Inc. ("MCI WorldCom")
and Ciera Network Systems, Inc. ("Customer") and is a part of their Telecommunications Services Agreement for Switched Services. Capitalized terms not
defined herein shall have the meaning ascribed to them in the TSA or the PET, as applicable.NOTE: ANY MODIFICATIONS, ADDITIONS OR DELETIONS FROM THIS ATTACHMENT WILL NOT BE
EFFECTIVE UNLESS SPECIFICALLY SET FORTH IN THE PET.

1.UIFN SERVICES:



2.UIFN TERM:The "UIFN
Term" will commence as of 9-26-2000 (the "Effective Date") and will be coterminous with the Service Term
described in the PET. At the end of the UIFN Term, the terms and conditions contained in this UIFN Attachment will remain in full force and effect until the earlier of (i) cancellation by either party
upon at least thirty (30) days' prior written notice to the other party, or (ii) the cancellation or scheduled termination of the TSA.

3.UIFN RATES:Commencing with the Effective Date and continuing
through the end of the UIFN Term, Customer's UIFN rates for DEDICATED UIFN and SWITCHED UIFN will be the * level of applicable charges shown on Schedule UIFN-A attached hereto and incorporated herein
by reference. [Note: If left blank, Customer's UIFN rates will be deemed to be the "Base UIFN Rates" shown on Schedule UIFN-A.]

4.ACCESSIBILITY/AVAILABILITY:MCI WorldCom will provide UIFN
Service subject to availability as determined solely by MCI WorldCom. Upon MCI WorldCom's receipt of a Service Order from Customer, MCI WorldCom will reserve and obtain for Customer a universal
international freephone number (the "UIFN Number") from the International Telecommunications Union (ITU). Customer agrees to pay MCI WorldCom a
nonrecurring fee of * per UIFN Number. MCI WorldCom will accept specific number requests, if available. The UIFN Number will be translated to a MCI

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

1

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WorldCom designated 800 billing identification number. Customer acknowledges that each UIFN Number obtained for Customer must be activated within ninety (90) days from the date the UIFN Number is
reserved with the UIFN Registrar. In the event a UIFN Number is not activated within such 90-day period, Customer acknowledges such UIFN Number may be canceled. MCI WorldCom reserves the right upon
not less than ten (10) days' prior notice to terminate UIFN Service relative to any UIFN Number which does not generate at least sixty (60) minutes of traffic during any consecutive six (6) months.

5.START OF SERVICE:Start of Service for (i) DEDICATED UIFN
will occur concurrently with the activation of each circuit comprising Service Interconnections relevant to DEDICATED UIFN, and (ii) SWITCHED UIFN will occur on an UIFN Number by UIFN Number basis
concurrently with the activation of each UIFN Number.

6.LIMITATION OF ORIGINATION OR TERMINATION LOCATIONS:



7.CDR MEDIA.MCI WorldCom will provide Call Detail Records
(CDRs) for MCI WorldCom's Switched Services in machine readable form in one of several magnetic tape formats (selected by Customer on Customer's Service Request) ("CDR
Media"). CDR Media provided hereunder (i) monthly is provided at no charge, (ii) weekly is subject to a recurring monthly charge of *, and (iii) daily is subject to the
applicable non-recurring Installation Charge as described below (plus all leased-line and equipment costs necessary to implement Daily CDR Media which will be determined on an individual case basis
depending on Customer's specific configuration).

*

IN WITNESS WHEREOF, authorized parties on behalf of their respective entities have initialed this Attachment for UNIVERSAL INTERNATIONAL
FREEPHONE NUMBER Service as of the date shown below.

|MCI WORLDCOM NETWORK SERVICES, INC. |  | CIERA NETWORK SYSTEMS, INC.
|----------------------------------- |  | ---------------------------
|MCI WorldCom's Initials             |  |                            
|Date:                               |  |                            

ATTACHMENTS:

Schedule
UIFN-A = Universal International Freephone Number Service Rates

Schedule
UIFN-B = UIFN Countries

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

2

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Classic Millennium UIFN Rates  (UIFN rates are not discountable)

*

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

3

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Schedule B-UIFN Country Availability

|UIFN COUNTRY     |  | INT'L Access Code
|---------------- |  | -----------------
|Australia        |  | 0011             
|Belgium*         |  | 00               
|Denmark          |  | 00               
|France           |  | 00               
|Germany          |  | 00               
|Hong Kong        |  | 001              
|Ireland*         |  | 00               
|Israel*          |  | 00               
|Japan            |  | 0061, 001 or 0041
|Korea (South)    |  | 001, 002         
|Malaysia*        |  | 00               
|Netherlands**    |  | 00               
|New Zealand      |  | 00               
|Norway           |  | 00               
|The Philippines* |  | 00               
|Singapore*       |  | 001              
|Spain*           |  | 00               
|Sweden*          |  | 009              
|Switzerland      |  | 00               
|Taiwan**         |  | 002              
|Thailand*        |  | 001              
|United Kingdom   |  | 00               

---

*
These countries are ONLY available on Advanced Toll Free Service UIFN.
** These countries are ONLY available on Classic, Access Based Billing and Transcend UIFN.

All
other countries are available on all products.

*
 CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

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