Document:

FORM OF EXCHANGE CAPITAL SECURITY

                  FORM OF SERIES B CAPITAL SECURITY CERTIFICATE

         IF THE  SERIES  B  CAPITAL  SECURITIES  CERTIFICATE  IS TO BE A  GLOBAL
SECURITIES  CERTIFICATE,  INSERT--  [THIS SERIES B CAPITAL  SECURITY IS A GLOBAL
CAPITAL  SECURITY WITHIN THE MEANING OF THE AMENDED AND RESTATED  DECLARATION OF
TRUST (THE "DECLARATION")  HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME
OF THE  DEPOSITORY  TRUST  COMPANY (THE  "CLEARING  AGENCY") OR A NOMINEE OF THE
CLEARING  AGENCY.  THIS SERIES B CAPITAL  SECURITY IS EXCHANGEABLE  FOR SERIES B
CAPITAL  SECURITIES  REGISTERED  IN THE NAME OF A PERSON OTHER THAN THE CLEARING
AGENCY  OR ITS  NOMINEE  ONLY  IN THE  LIMITED  CIRCUMSTANCES  DESCRIBED  IN THE
DECLARATION  AND NO  TRANSFER OF THIS  SERIES B CAPITAL  SECURITY  (OTHER THAN A
TRANSFER OF THIS SERIES B CAPITAL  SECURITY AS A WHOLE BY THE CLEARING AGENCY TO
A NOMINEE OF THE CLEARING  AGENCY OR BY A NOMINEE OF THE CLEARING  AGENCY TO THE
CLEARING  AGENCY OR ANOTHER  NOMINEE OF THE CLEARING  AGENCY) MAY BE  REGISTERED
EXCEPT IN LIMITED CIRCUMSTANCES.

         UNLESS THIS SERIES B CAPITAL  SECURITY IS  PRESENTED  BY AN  AUTHORIZED
REPRESENTATIVE  OF THE CLEARING  AGENCY TO CASCADE CAPITAL TRUST I (THE "TRUST")
OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY SERIES B
CAPITAL  SECURITY  ISSUED IS  REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER
NAME AS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF THE CLEARING AGENCY AND ANY
PAYMENT  HEREON IS MADE TO CEDE & CO., ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF
FOR VALUE OR  OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  SINCE THE  REGISTERED
OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.]

         THE SERIES B CAPITAL  SECURITIES  WILL BE ISSUED AND MAY BE TRANSFERRED
ONLY IN BLOCKS HAVING A LIQUIDATION AMOUNT OF NOT LESS THAN $100,000 (100 SERIES
B CAPITAL  SECURITIES) AND MULTIPLES OF $1,000 IN EXCESS THEREOF.  ANY ATTEMPTED
TRANSFER OF SERIES B CAPITAL  SECURITIES IN A BLOCK HAVING A LIQUIDATION  AMOUNT
OF LESS THAN  $100,000 (100 SERIES B CAPITAL  SECURITIES)  SHALL BE DEEMED TO BE
VOID AND OF NO LEGAL EFFECT WHATSOEVER.  ANY SUCH PURPORTED  TRANSFEREE SHALL BE
DEEMED NOT TO BE THE HOLDER OF SUCH SERIES B CAPITAL SECURITIES FOR ANY PURPOSE,
INCLUDING,  BUT NOT LIMITED TO, THE  RECEIPT OF  DISTRIBUTIONS  ON SUCH SERIES B
CAPITAL  SECURITIES,  AND SUCH PURPORTED  TRANSFEREE  SHALL BE DEEMED TO HAVE NO
INTEREST WHATSOEVER IN SUCH SERIES B CAPITAL SECURITIES.

<PAGE>

Certificate Number:  _______________              Aggregate Liquidation Amount:
CUSIP Number:        _______________              $_______________

               Certificate Evidencing Exchange Capital Securities

                                       of

                             Cascade Capital Trust I

                       11.0% Capital Securities, Series B
                (liquidation amount $1,000 per Capital Security)

                  Cascade  Capital Trust I, a statutory  business  trust created
under the laws of the State of Delaware (the  "Trust"),  hereby  certifies  that
_____________  is the  registered  owner of $_________ in aggregate  liquidation
amount of  Capital  Securities  of the Trust  representing  undivided  preferred
beneficial  interests in the assets of the Trust  designated  the 11.0%  Capital
Securities,  Series B  (liquidation  amount  $1,000 per Capital  Security)  (the
"Exchange Capital Securities"). The Exchange Capital Securities are transferable
on the books  and  records  of the  Trust,  in  person  or by a duly  authorized
attorney,  upon surrender of this  certificate  duly endorsed and in proper form
for transfer. The designation, rights, privileges, restrictions, preferences and
other terms and provisions of the Exchange Capital Securities represented hereby
are issued and shall in all respects be subject to the provisions of the Amended
and Restated Declaration of Trust, dated as of March 1, 2000, as the same may be
amended from time to time (the "Declaration"),  including the designation of the
terms  of the  Exchange  Capital  Securities  as set  forth  in  Annex  I to the
Declaration.  Capitalized  terms  used but not  defined  herein  shall  have the
meaning  given them in the  Declaration.  The Sponsor will provide a copy of the
Declaration,  the Capital Securities  Guarantee and the Indenture (including any
supplemental  indenture) to a Holder without charge upon written  request to the
Trust at its principal place of business.

                  Upon receipt of this  Certificate,  the Holder is bound by the
Declaration  and is entitled to the benefits  thereunder  and to the benefits of
the Capital Securities Guarantee to the extent provided therein.

                  By acceptance  hereof,  the Holder  agrees,  for United States
federal  income tax purposes,  to treat the Debentures as  indebtedness  and the
Exchange Capital Securities as evidence of indirect beneficial  ownership in the
Debentures.

<PAGE>

                  IN WITNESS  WHEREOF,  the Trust has executed this  certificate
this _____ day of ______________ , 2000.

                             CASCADE CAPITAL TRUST I

                                            By: ____________________________
                                                     Frank M. McCord
                                                     Administrative Trustee

<PAGE>

                PROPERTY TRUSTEE'S CERTIFICATE OF AUTHENTICATION

         This  is one of the  11.0%  Capital  Securities,  Series  B of  Cascade
Capital Trust I referred to in the within-mentioned Declaration.

                                    WILMINGTON TRUST COMPANY,
                                     not in its individual capacity but solely
                                     as Property Trustee

Dated: __________,2000              By: ______________________________________
                                        Authorized Signatory

<PAGE>

                  Distributions  on  each  Exchange  Capital  Security  will  be
payable  at a  fixed  rate  per  annum  of  11.0%  (the  "Coupon  Rate")  of the
liquidation  amount of $1000 per Exchange Capital Security,  such rate being the
rate of interest  payable on the Debentures to be held by the Property  Trustee.
Distributions in arrears for more than one semi-annual period will bear interest
thereon compounded  semi-annually at the Coupon Rate (to the extent permitted by
applicable law). The term  "Distributions,"  as used herein,  includes such cash
distributions  and any and all such interest,  if any,  payable unless otherwise
stated.  A Distribution  is payable only to the extent that payments are made in
respect of the  Debentures  held by the  Property  Trustee and to the extent the
Property Trustee has funds legally available therefor.

                  Distributions  on the  Exchange  Capital  Securities  will  be
cumulative,  will  accumulate  from the most recent date to which  Distributions
have been paid or, if no  Distributions  have been paid,  from March 1, 2000 and
will be payable  semi-annually in arrears, on March 1/st/ and September 1/st/ of
each year,  commencing  September 1, 2000, except as otherwise  described below.
Distributions  will be computed on the basis of a 360-day year of twelve  30-day
months.  As long as no Event of Default has occurred and is continuing under the
Indenture,  the  Debenture  Issuer has the right  under the  Indenture  to defer
payments of interest by extending  the interest  payment  period at any time and
from time to time on the  Debentures  for a period not exceeding 10  consecutive
semi-annual calendar periods, including the first such semi-annual period during
such  extension  period (each an  "Extension  Period"),  during which  Extension
Period no interest shall be due and payable on the Debentures,  provided that no
Extension Period shall end on a date other than an Interest Payment Date for the
Debentures  or  extend  beyond  the  Maturity  Date  of  the  Debentures.  As  a
consequence of such deferral,  Distributions (other than Liquidiated Damages, if
any)  will  also  be  deferred.   Notwithstanding  such  deferral,   semi-annual
Distributions  will continue to accumulate with interest  thereon (to the extent
permitted by  applicable  law, but not at a rate  exceeding the rate of interest
then accruing on the  Debentures)  at the Coupon Rate  compounded  semi-annually
during any such  Extension  Period.  Prior to the  termination  of any Extension
Period,  the Debenture  Issuer may further defer payments of interest by further
extending such Extension  Period;  provided that such Extension  Period does not
cause  such  Extension  Period,  together  with all such  previous  and  further
extensions within such Extension  Period,  to exceed 10 consecutive  semi-annual
periods,  including the first  semi-annual  period during such Extension Period,
end on a date other than an Interest  Payment Date for the  Debentures or extend
beyond  the  Maturity  Date  of the  Debentures.  Upon  the  termination  of any
Extension  Period and the payment of all amounts then due, the Debenture  Issuer
may commence a new Extension Period, subject to the above requirements.

                  Subject  to receipt  by the  Sponsor  of any and all  required
regulatory   approvals  and  to  certain  other  conditions  set  forth  in  the
Declaration and the Indenture, the Property Trustee may, at the direction of the
Sponsor, at any time dissolve the Trust and after satisfaction of liabilities to
creditors of the Trust as provided by applicable law, cause the Debentures to be
distributed  to the Holders of the  Securities in  liquidation  of the Trust or,
simultaneously with any redemption of the Debentures, cause a Like Amount of the
Securities to be redeemed by the Trust.

         The Exchange Capital  Securities shall be redeemable as provided in the
Declaration.

                -------------------------------------------------

<PAGE>

                                   ASSIGNMENT

                -------------------------------------------------

FOR VALUE RECEIVED,  the undersigned  hereby assigns and transfers this Exchange
Capital Security Certificate to:

--------------------------------------------------------------------------------
            (Assignee's social security or tax identification number)

--------------------------------------------------------------------------------
                       (Address and zip code of assignee)

and irrevocably appoints

--------------------------------------------------------------------------------
agent to transfer this Exchange Capital Security Certificate on the books of the
Trust. The agent may substitute another to act for him or her.

Date: __________________

Signature:_________________________________________
(Sign  exactly as your name appears on the other side of this  Exchange  Capital
Security Certificate)

Signature Guarantee: ______________________________

                          ---------------------------

         Signature  must be  guaranteed by an "eligible  guarantor  institution"
that is a bank,  stockbroker,  savings  and loan  association  or  credit  union
meeting the requirements of the Registrar, which requirements include membership
or participation in the Securities  Transfer Agents Medallion  Program ("STAMP")
or  such  other  "signature  guarantee  program"  as  may be  determined  by the
Registrar in addition to, or in substitution  for, STAMP, all in accordance with
the Securities Exchange Act of 1934, as amended.<PAGE>

                                                                EXHIBIT 10.7

                             PROCUREMENT AGREEMENT

                                    BETWEEN

                    BROADWING COMMUNICATIONS SERVICES  INC.

                                      AND

                              CORVIS CORPORATION

                             DATED March 17, 2000
<PAGE>

                              TABLE OF  CONTENTS

<TABLE>
<CAPTION>
                                                                     Page
                                                                     ----
<S>                                                                  <C>
              Recital                                                   1
Article 1     Laboratory System                                         1
Article 2     Transport Field Trial                                     2
Article 3     Reserved                                                  4
Article 4     Volume Deployment; Quantities and Delivery Schedules      5
Article 5     Commercial Testing; Product Discontinuation               7
Article 6     Pricing, Invoicing, Payment and Other Financial Terms     8
Article 7     Term                                                      9
Article 8     Documentation and Reports                                 9
Article 9     Delivery and Installation                                 9
Article 10    Force Majeure                                            10
Article 11    Training                                                 10
Article 12    Software License                                         11
Article 13    Software Changes                                         13
Article 14    Product Changes                                          13
Article 15    Proprietary Information                                  15
Article 16    Warranties, and Warranty Exclusions and Limitations      16
Article 17    Representations and Other Warranties                     18
Article 18    Remedies and Limitations                                 18
Article 19    Support and Other Services                               20
Article 20    Insurance                                                20
Article 21    Indemnification                                          21
Article 22    Patents, Copyright and Trade Secrets                     21
Article 23    Termination                                              22
Article 24    Dispute Resolution                                       23
Article 25    Notice and Representatives of the Parties                24
Article 26    General                                                  25
Article 27    Incorporation of Documents                               26
Article 28    Definitions                                              26
Article 29    Entire Agreement                                         29
</TABLE>

<PAGE>

                             PROCUREMENT AGREEMENT
                BETWEEN BROADWING COMMUNICATIONS SERVICES INC.
                            AND CORVIS CORPORATION

     THIS PROCUREMENT AGREEMENT ("Agreement"), made effective as of this 17th
day of March, 2000 ("Effective Date"), by and between Broadwing Communications
Services Inc., a Delaware  corporation, having its principal place of business
at 1122 Capital of Texas Highway South, Austin, Texas 78746-6426  (hereinafter
referred to as "Customer"), and Corvis Corporation, a Delaware corporation,
having its principal place of business at 7015 Albert Einstein Drive, Columbia,
MD 21046-9400 (hereinafter referred to as "Corvis").

     A.   Customer is a leading telecommunications service provider offering a
          broad range of telecommunications services requiring ever-increasing
          bandwidth.

     B.   Corvis is a manufacturer of next-generation optical network equipment
          whose ultra-long transmission capacity and high channel count products
          coupled with its optical router create substantially greater capacity
          while simultaneously reducing the overall cost-per-bit to the lowest
          levels in the industry.

     C.   Customer desires to deploy commercially, and Corvis desires to supply,
          Corvis equipment and software in Customer's network contingent upon
          such equipment and software performing in accordance with the
          Transport Field Trial Test Criteria, as defined below.

     NOW, THEREFORE, in consideration of the foregoing premises and the
representations, warranties, covenants and agreements herein contained, the
parties agree as follows:

DEFINITIONS: Defined terms and definitions are set forth in Article 28 of this
Agreement.

ARTICLE 1.  LABORATORY SYSTEM.

     1.1  Equipment and Software. Corvis will sell to Customer, and Customer
     will purchase, the Equipment and Software identified in Attachment 1 (the
     "Laboratory System") for the prices set forth in such attachment.

     1.2  Payment. Customer will pay Corvis an amount equal to the total cost of
     the Laboratory System as specified in Attachment 1. Payment will be due
     within thirty (30) days after the receipt of invoice. Corvis will invoice
     Customer for the Laboratory System upon shipment to Customer.

     1.3  Shipment of Laboratory System. Corvis will ship to Customer the
     Laboratory System by the date for such delivery set forth in Attachment
     1.3.

     1.4  Payment for lab system will be returned (in the form of product
     credits) once Customer has paid $50MM in Corvis invoices

                                       1
<PAGE>

ARTICLE 2.  TRANSPORT FIELD TRIAL.

     2.1  Scope. Customer will conduct a field trial of the Corvis transport
     equipment and software by deploying Corvis Equipment and Software in the
     configuration set out in Attachment 2 ("Transport Field Trial") to
     determine whether such Equipment and Software (the "Transport Field Trial
     Equipment and Software") fulfill the test criteria set forth in Attachment
     2 ("Transport Field Trial Test Criteria").

     2.2  Equipment and Software

          (a)  Corvis will sell to Customer, and Customer will purchase, the
          Transport Field Trial Equipment and Software identified in Attachment
          2 for the prices set forth in such attachment.

          (b)  In connection with the Transport Field Trial, Corvis will provide
          Customer required installation services, maintenance, training, and
          technical support for no charge.

     2.3  Payment

          (a)  Due to the high up front cost associated with the components
          included in the Transport Field Trial Equipment , Customer will pay
          Corvis, within thirty days after the Effective Date, an amount equal
          to one half of the total cost of the Equipment and license fees for
          Transport Field Trial Software to be paid by Customer to Corvis for
          the Transport Field Trial Equipment and Software as specified in
          Attachment 2.

          (b)  Customer will pay the remainder of the purchase price for the
          Transport Field Trial Equipment and license fees for Transport Field
          Trial Software within five days after successful completion of the
          Transport Field Trial, which will be deemed to occur on the date the
          Transport Field Trial Equipment and Software meet the Transport Field
          Trial Test Criteria.

          (c)  Should the Transport Field Trial not be successfully completed
          (as described above) within 75 days after system turn-up, either party
          may elect to terminate the Transport Field Trial upon written notice
          to the other party. In the event of such termination, Customer will
          promptly return the Transport Field Trial Equipment and Software to
          Corvis at Customer's expense. Upon such return, Corvis will repay the
          payments made by Customer pursuant to Section 2.3(a) within 30 days
          after such termination of the Transport Field Trial.

     2.4  Shipment of Transport Field Trial Equipment and Software. Corvis will
     ship to Customer the Transport Field Trial Equipment and Software by the
     date for such shipment set forth in Attachment 1.3.

                                       2
<PAGE>

     2.5  Duration of Transport Field Trial. Customer will complete the
     Transport Field Trial as soon as practicable, but in any event not later
     than 60 days after delivery, installation and turn-up of the Transport
     Field Trial Equipment and Software. If the Transport Field Trial Equipment
     and Software fulfill the Transport Field Trial Test Criteria, Customer
     will, within 30 days thereafter, commence deployment of Corvis Transport
     Equipment and Software in its network pursuant to Article 4. Customer will
     acknowledge in writing the successful completion of the Transport Field
     Trial within three days after such completion.

ARTICLE 3.  RESERVED.

ARTICLE 4.  VOLUME DEPLOYMENT; QUANTITIES AND DELIVERY SCHEDULES.

     4.1  Initial Deployment. Upon successful completion of the Transport Field
     Trial, Customer will purchase from Corvis and deploy the Corvis Transport
     Equipment and Software in quantities and in configurations priced at
     U.S.$200,000,000.00 (the "Minimum Deployment Commitment"), U.S.
     $100,000,000.00 of which (the "First Year Deployment Commitment") must be
     ordered within 12 months after the successful completion of the Field Trial
     with delivery no later than 60 days after such 12 month period, in each
     case based on the prices and license fees set forth in Attachment 6.
     Customer will be offered most favored customer pricing in accordance with
     the terms and conditions of Attachment 6.

     4.2  (a)  Quantity Forecast. By the fifth business day of each month (the
               month hereafter being "M"), Customer will provide to Corvis a
               non-binding ten-month rolling forecast (the "Rolling Forecast")
               of deliveries for the ten-month period commencing at the
               beginning of the third-month after the month in which the
               forecast is made the Rolling Forecast (M+3 through M+12) will
               show the quantity of each Product by product code which Customer
               anticipates it will need to be delivered during the specified
               month.

          (b)  Initial Rolling Forecast; Capacity. Notwithstanding anything to
               the contrary contained herein, the parties shall discuss the
               initial Rolling Forecast issued under this Agreement to better
               anticipate Product requirements and availability.

     4.3  During the Term of this Agreement, Customer will issue Purchase Orders
     specifying the Products ordered, the quantities necessary, the delivery
     site or sites (hereinafter the "Specified Site[s]") for the Products and
     its proposed delivery schedule.

     4.4  All deliveries of Products will be made F.O.B. destination. Customer
     agrees to pay freight and insurance charges. The preceding provisions of
     this clause are valid for deliveries in the United States, its possessions
     and territories only. All deliveries outside the aforementioned areas will
     be mutually agreed upon on a case by case basis.

                                       3
<PAGE>

     4.5  Customer will have the right to alter the destination site at least
     ten (10) days prior to Corvis' scheduled shipment date for Products,
     without cost or expense to Customer, by timely transmitting Notice to
     Corvis of the new Specified Site(s).

     4.6  Corvis will execute and deliver to Customer an order acknowledgment
     within seven days after Corvis' receipt of each Purchase Order or, if
     Corvis cannot meet the proposed delivery times, the parties shall mutually
     agree to appropriate delivery times. If Corvis and Customer cannot agree
     upon delivery times, Corvis shall have the right to reject a Purchase
     Order. Product order lead times shall be 12 weeks unless otherwise
     specified by Corvis.

     4.7  Customer will purchase on-site installation spares parts and
     components of the Equipment ("Spares Kits" or "Kits") reasonably designated
     by Corvis and agreed upon by Corvis and Customer from time to time as the
     quantity necessary to enable Corvis to provide the warranty and support
     services required by this Agreement. The quantity and locations of the Kits
     may change with installation requirements and changes in the topology of
     Customer's network.

     4.8  [*]

     4.9  [*]

ARTICLE 5.  CUSTOMER TESTING; PRODUCT DISCONTINUATION.

     5.1  Customer will have 30 days after receipt of Product at its location to
     perform any acceptance testing that Customer wishes to perform to confirm
     that the Product complies with its applicable Technical Requirements.
     Unless Customer notifies Corvis within that 30 day period of any defects in
     such Product, Customer will be deemed to have accepted the Product.
     Customer's inspection or failure to inspect and/or its acceptance of any
     Product will not relieve Corvis of its warranty obligations in respect of
     such Product.

     5.2  Corvis will notify Customer promptly upon learning of any material
     defects in any of the Products.

     5.3  (a)  Corvis will support all Licensed Software and Equipment for its
          expected useful life, as set forth in Attachment 5.3 ("Product Life"),
          subject to the support limitations for Licensed Software contained in
          Attachment 19.

          (b)  If Corvis discontinues manufacture and/or support of the
          Equipment, Corvis will at Customer's request, to the extent of Corvis'
          legal rights to do so, without obligation or charge to Customer
          deliver to Customer all of the technical information owned and
          possessed by Corvis relating to the manufacture and/or support of the
          Equipment, in the form being used in Corvis' factories in its day-to-
          day operations of manufacture, or arrange for the replacement and
          repair spare parts for the Equipment to Customer's reasonable
          satisfaction. Customer may use such

                                       4
<PAGE>

          technical information only to manufacture, have manufactured, obtain
          such spare parts from other sources in connection with the Equipment
          and System Software obtained from Corvis and owned and operated or
          licensed by Customer. Title to Corvis' technical information and
          intellectual property rights will remain with Corvis.

ARTICLE 6.  PRICING, INVOICING, PAYMENT AND OTHER FINANCIAL TERMS.

     6.1  Prices for Products are set forth in Attachment 6. In addition,
     Customer will pay the right to use fee (the "Right to Use Fee") for the
     Equipment and/or Software and intellectual property associated with Corvis
     Equipment as specified in Attachment 6.

     6.2  The prices in this Agreement do not include any federal, state or
     local sales, use, excise or similar taxes, however designated, which may be
     levied or assessed on the Products or Services provided hereunder, and any
     personal property taxes levied or assessed on Products which has been
     delivered but as to which title has not passed to Customer. With respect to
     such taxes, Customer will either furnish Corvis with an appropriate
     exemption certificate applicable thereto, or pay to Corvis, such amounts as
     Corvis may by law be required to collect or pay.

     6.3  Payment terms are set forth as follows:

          (a)  Customer will remit payment to Corvis for invoiced amounts within
          thirty (30) days after the receipt of the invoice, which will be
          issued upon shipment of the Product or completion of Services, as
          applicable. Charges for Services and Equipment will be invoiced and
          paid separately by Customer.

          (b)  Customer will not be required to pay for Products or Services
          which are rightfully rejected.

     6.4  In the event Corvis fails to receive payment from Customer as required
     herein, Customer will have fifteen (15) calendar days to cure such non-
     payment after its notice of non-payment from Corvis. Payments provided for
     in this Agreement, when overdue, will bear interest at a rate per month
     equal to 1.5 % for the time period from and including the due date until
     payment is received by Corvis.

     6.5  Invoicing instructions will be as follows:

     Original Invoice Sent To:

     Broadwing Communication Services
     Attn: Accounts Payable
     1122 Capital of Texas Highway South
     Austin, Texas 78746

                                       5
<PAGE>

ARTICLE 7.  TERM.

     Subject to the terms and conditions of this Agreement, the initial term of
     this Agreement will be two (2) years from the successful completion of the
     Transport Field Trial ("Initial Term"). This Agreement will be
     automatically renewed for successive one-year terms (without any Minimum
     Deployment Commitment pursuant to Section 4.1 unless otherwise agreed by
     the parties) unless either party gives notice of non-renewal at least 90
     days before the expiration of the Initial Term or any renewal term. The
     Initial Term in combination with any extensions is also referred to in this
     Agreement as the "Term".

ARTICLE 8.  DOCUMENTATION AND REPORTS.

     Corvis will provide to Customer, one electronic copy of the Documentation
     necessary to operate and maintain the Products provided hereunder for each
     Specified Site at which such Product is installed. Corvis will provide
     Customer with (a) updates to the Documentation, as such updates are made
     generally available, and (b) new and/or revised data incorporating any
     changes to the Products which affect form, fit, or function, in each case
     at no additional charge to Customer. Such Documentation may be reproduced
     by Customer for its internal use, provided that any copyright notice of
     such Documentation is copied as well. Soft copies of such Documentation
     will be available upon Customer's request. Such Documentation will be used
     solely for Customer's internal use only on a need-to-know and need-to-use
     basis.

ARTICLE 9.  DELIVERY AND  INSTALLATION.

     9.1  Corvis will mark each shipment to Customer with Corvis name, the
     Purchase Order number, and the identity and quantity of Product. Final
     destination, interim staging area or any special shipping instructions and
     any applicable charge will be specified on each Purchase Order.

     9.2  Corvis will perform installation services for the Products at Corvis'
     then standard rates for such services and on terms and conditions agreed by
     the parties.

ARTICLE 10. FORCE MAJEURE

     10.1 Except as otherwise provided herein, neither Corvis nor Customer will
     be liable to the other for any delay in performing in accordance with this
     Agreement if such delay arises out of an Act of God including fire, flood,
     earthquake, explosion, casualty, or accident, or out of war, riot, civil
     commotion, labor dispute, the requirement of any governmental

                                       6
<PAGE>

     agency or instrumentality, industry-wide shortages of raw materials or
     transportation facilities, or any other cause beyond the control of the
     party claiming force majeure.

     10.2 The party asserting that an event of force majeure has occurred will
     send the other party prompt notice thereof setting forth a description of
     the event of force majeure, an estimate of its effect upon the party's
     ability to perform its obligations under this Agreement and the duration or
     expected duration thereof.

     10.3  The party asserting that an event of force majeure has occurred will
     be excused, on a day-to-day basis, from the performance of its obligations
     under this Agreement to the extent prevented or delayed by such event (and
     the other party likewise will be excused, on a day-to-day basis, from the
     performance of its obligations under this Agreement to the extent such
     party's obligations related to the obligations are so prevented or
     delayed); provided, however, that the party asserting the occurrence of a
     force majeure event will use diligent efforts to avoid or remove such force
     majeure event.

ARTICLE 11.  TRAINING.

     11.1 Corvis will provide, upon Customer's request and at the time or times
     required by Customer during the Term of this Agreement, training classes
     and training materials for Customer personnel. Training will take place at
     the Corvis facilities in Columbia, MD. The training programs necessary for
     full installation, operation and maintenance of the Corvis Products are
     summarized in Attachment 11.1, which shall be subject to change by Corvis
     from time to time to reflect updates to the training methodology and
     courses. Such training will be kept current to encompass the latest
     Licensed Software and Equipment, or any other Software revision level
     and/or Equipment revision level directed by Customer. Subject to the
     foregoing, course content and material will be designed and agreed to by
     mutual consent. Customer will have the right to copy Corvis' training
     materials for its internal use provided that any copyright notice included
     in such material is copied as well. Courses will be limited to a maximum of
     ten (10) attendees in each course session. Corvis will provide at no
     additional charge a total of 30 seats in the aggregate to Corvis training
     programs that will train attendees in the installation, testing or
     operation of Corvis Equipment. Such training programs will be offered
     commencing upon the initial commercial deployment by Customer of the Corvis
     equipment. Corvis will implement commencing in Q1 2001 training and
     certification programs and will certify that participants in such training
     courses received information sufficient for installation, testing or
     operation of Corvis Equipment and Corvis will provide that the 30
     individuals utilizing the 30 seats provided by Corvis as set out above are
     provided training sufficient to certify them. Such certification shall not
     make Corvis liable for any negligence of or damage caused by such certified
     individuals. Subsequent training programs will be charged at a rate of
     U.S.$350 per person-day of training. In all cases, Customer is obligated to
     pay for all travel and lodging of Customer personnel. All training will be
     conducted at Corvis' Maryland location, or such other locations as may be
     mutually agreed upon by the parties.

                                       7
<PAGE>

     11.2  Corvis will certify attendees upon successful completion of the
     course. Such course content and materials may be tailored or customized by
     Customer for its internal use only.

ARTICLE 12.  SOFTWARE LICENSE.

     12.1  Subject to payment of any and all applicable license fees set out in
     Attachment 6, Corvis grants to Customer a perpetual (subject to termination
     pursuant to the terms of this Agreement), personal, nontransferable (except
     as provided in this Agreement), and nonexclusive license (or, with respect
     to the Third Party Software, a sublicense) to use the Software and its
     related Documentation provided pursuant to the terms of this Agreement. Use
     of the Software is restricted to the specified number of Network Elements
     or the designated equipment, as applicable ("Designated Equipment") set
     forth on Customer's Purchase Order(s). If a Designated Equipment becomes
     inoperative, Customer will have the right to use the Software on comparable
     backup equipment until such Designated Equipment is restored to operable
     status. No Software license fee shall be payable to Corvis with respect to
     spares. The license grants Customer no right to and Customer will not
     sublicense such Software, or modify, decompile, or disassemble Software
     furnished as object code to generate corresponding Source Code. Customer
     and its customers will be entitled to modify only the user-controlled
     features of the Software as provided for in the related Documentation. With
     respect to any Third Party Software, in addition to the terms and
     conditions herein, Customer will abide by the applicable terms and
     conditions for such Third Party Software. Attachment 12.1 lists the Third
     Party Software licenses that are applicable as of the date of this
     Agreement.

     12.2 The CEM Software provided for use on Sun Workstations may only be used
     on such workstation if such Software is the only software running on such
     workstation and access to such workstation is password protected.

     12.3 All Software (whether or not part of firmware) and its related
     documentation furnished by Corvis, and all copies thereof made by Customer,
     including translations, compilations, and partial copies, are and will
     remain the exclusive property of Corvis and its licensors. Customer will
     hold such Software and related documentation in strict confidence, and will
     not, without Corvis' prior written consent, disclose, provide, provide
     access to, or otherwise make available, in whole or in part, any Software
     or related documentation including any description of the Corvis Management
     Information Base (MIB) sections of the Software to anyone, except to its
     employees, and those agents and subcontractors that are not competitors of
     Corvis having a need-to-know for purposes of operating or maintaining the
     related Product, and except to its customers to the extent necessary to
     permit them to utilize customer-controlled features in accordance with the
     applicable Documentation. Such availability shall be limited to only those
     portions of the Software and its related documentation for which there is a
     need-to-know for purposes of operating or maintaining the related Product.
     All persons to whom the Software and relative documentation is made
     available shall have agreed in writing to obligations of confidentiality at
     least as protective as those set forth herein. Customer shall maintain an
     accurate and complete list of all persons having access to the Software and
     its related documentation and shall maintain a log of persons accessing the
     Software and its related

                                       8
<PAGE>

     documentation and the nature of the access, e.g., edit, view, copy, etc.
     Customer shall provide Corvis with prompt written notice of any
     unauthorized use of the Software and its related documentation and fully
     cooperate with Corvis in enforcing Corvis' proprietary rights in the
     Software and its related documentation.

     Customer shall not, and shall not permit any other person to copy,
     duplicate, modify, alter, enhance, revise, summarize, or prepare derivative
     works from any portion of the MIB sections of the Software. Customer will
     not copy Software embodied in firmware. Customer will not make any copies
     of any other Software or related documentation except as necessary for
     maintaining archival copies in accordance with Customer's customary
     practices. Such archival copies shall be stored in a locked and secured
     container. Customer will reproduce and include any Corvis copyright and
     proprietary notice on all such necessary copies of the Software and its
     related documentation. Customer will take appropriate action, by
     instruction, agreement, or otherwise, with the persons permitted access to
     the Software and related documentation to enable Customer to satisfy its
     obligations under this Agreement. When the Software and related
     documentation are no longer needed by Customer, or if Customer's license is
     canceled or terminated, Customer will return all copies of such Software
     and related documentation to Corvis or follow written disposition
     instructions provided by Corvis.

     12.4  Subject to Corvis' approval which will not be unreasonably withheld,
     Customer may transfer its right-to-use Software furnished under this
     Agreement without the payment of an additional right-to-use fee by third
     party transferee, except for additional fees which would have been
     applicable to Customer with respect to usage sensitive factors (e.g.,
     feature pricing based on activation level). Such transfer can be made to
     another end user for their own internal use, but not to any competitor of
     Corvis and only under the following conditions:

           (a)  Such Software will be used only within the United States and
           such other countries for which such Software may be licensed from
           time to time under the terms of this Agreement.

           (b)  The right to use such Software may be transferred only together
           with the Designated Equipment with which Customer has a right to use
           such Software, as long as such transfer of the Designated Equipment
           is permitted pursuant to Section 15.3, and such right to use the
           Software will continue to be limited to use with such Designated
           Equipment;

           (c)  Before any such Software will be transferred, Customer will
           notify Corvis in writing of such intended transfer and the transferee
           will have agreed in writing (a copy of which will be provided to
           Corvis before such transfer) to the terms of this Agreement and any
           amendments thereto.

     12.5  Subject to Section 12.2, upon advance written notice to Corvis,
     Customer may physically transfer Software or optional feature packages, for
     which Customer has the right to use, from one Customer-owned workstation
     computer and relocate them to another Customer-owned workstation computer,
     provided that (a) the Product from which the

                                       9
<PAGE>

     Software has been transferred will cease to be Designated Equipment for
     such transferred Software and the workstation to which the Software has
     been transferred will thereafter be deemed to be the Designated Equipment,
     and (b) the Software delivered by Corvis pursuant to a Purchase Order will
     not be resident at any time on more than the total number of items of
     Designated Equipment for such Software set forth on the applicable Purchase
     Order. Customer will not be required to pay additional right-to-use fees as
     a result of such relocation, except for additional fees which would have
     been applicable to Customer with respect to usage sensitive factors.

     12.6  Provided that Customer has proceeded with volume deployment pursuant
     to Section 4, Corvis and Customer will enter into an escrow agreement, in
     the form set forth in Attachment 12.6 and acceptable to both parties
     ("Escrow Agreement"). The escrow agent for the Escrow Agreement will be
     Fort Knox Escrow Services, Inc. or another escrow agent acceptable to both
     parties. Corvis will bear the cost of providing Corvis' Source Code to the
     Escrow Agent. Customer will pay the Escrow Agent's charges, including any
     costs associated with testing the Source Code in Escrow or with release of
     such Source Code. Upon execution of the Escrow Agreement by both parties,
     Corvis will place in escrow the source code version of the Software
     (excluding Third Party Software). Thereafter, Corvis will supplement the
     materials in escrow to include upgrades and new releases of the Software
     (excluding Third Party Software) then in use by Customer. The Escrow
     Agreement will provide for the availability of the materials in escrow,
     subject to the terms and conditions of the Escrow Agreement.

ARTICLE 13.  SOFTWARE CHANGES.

     13.1  Corvis will furnish to Customer preliminary planning information and
     documentation for new releases of the Software. Such information will be
     provided at no charge to Customer. New generally available releases of the
     Software may be licensed by Customer at Corvis' then-current standard
     license fees, except to the extent such releases are included in the
     Maintenance and Support Services then in effect pursuant to the terms of
     this Agreement.

     13.2  Software licensed to Customer under this Agreement may contain
     supplemental optional features or enhancements that are separately priced.
     Customer agrees not to activate such optional feature or enhancements
     without written authorization from Corvis and Customer's payment of the
     appropriate license fees. If, in spite of Customer's best efforts to comply
     with this restriction, such features are activated, Customer agrees to so
     notify Corvis promptly and to pay Corvis the license fees for the activated
     features as well as the reasonable cost of money not exceeding the prime
     rate of interest for the period in which such features were activated.
     Corvis will have the right to audit Customer's usage of Corvis Equipment
     and Software to assure compliance with the terms of this Agreement.

                                      10
<PAGE>

ARTICLE 14.  PRODUCT CHANGES.

     14.1  Prior to shipment, Corvis may at any time make changes in Products or
     modify the drawings and specifications relating thereto or substitute
     Products of later design, provided the changes, modifications or
     substitutions under normal and proper use do not impact upon form, fit or
     function of the ordered Equipment or materially adversely affect the use,
     function, or performance of the ordered Software, as provided in the
     Technical Requirements. Unless otherwise agreed, such Software substitution
     will not result in any additional charges to Customer with respect to
     licenses for which Corvis has quoted fees to Customer. With respect to
     changes, modifications, and substitutions which affect the form, fit,
     function, use or performance of an ordered Product, Corvis will notify
     Customer in writing 90 days prior to their effective dates. In the event
     any such change is not desired by Customer, Customer will notify Corvis
     within 30 days from the date of notice and Corvis will not furnish any such
     changed Products to Customer on any orders in process at the time Corvis is
     so notified. In no event will Corvis change the form, fit, function, use or
     performance of any Product if such change causes the Product not to conform
     to the Technical Requirements, except to the extent such change conforms to
     changes in network telecommunications standards generally accepted in the
     industry.

           Corvis may discontinue any Product or Software version if Corvis
     gives Customer at least one year's notice thereof. In such event, Corvis
     will provide Customer with a suggested product replacement at the same time
     for the remainder of the term of this Agreement. Customer will have the
     right to substitute the replacement product for the Product under this
     Agreement, at a price to be negotiated by the parties. If Customer elects
     not to use the suggested replacement product, Corvis will offer Customer a
     one-year period beginning the day of the notice of discontinuance within
     which Customer can place orders for the discontinued Product. Customer may
     give a last order ("One Time Buy Order") immediately prior to the end of
     the six-month period. The One Time Buy Order is non-cancelable, non-
     reschedulable and non-returnable; except as otherwise provided in this
     Agreement. Products ordered with the One Time Buy Order will be delivered
     to Customer as requested by Customer but no later than one year after the
     notice of discontinuance.

     14.2  Class Changes.

           (a)  After Corvis Equipment has been shipped to Customer, if Corvis
           issues a Class A Change or Class B Change, or where modification to
           correct an error in Documentation is to be introduced, Corvis will
           promptly notify Customer of such change through Corvis' designated
           notification procedure ("Change Notification"). Corvis will promptly
           provide, or cause the respective manufacturer to provide, to Customer
           any changes comparable to Class A and Class B Changes to the extent
           they are made available by manufacturers with respect to Vendor Items
           sold to Customer by Corvis; it being understood that the respective
           manufacturers of the Vendor Items may not provide such changes for
           the same period of time for which Corvis is obligated to provide
           Class A and Class B changes.

           (b)  Corvis will, at its expense, furnish the parts and documentation
           necessary for

                                      11
<PAGE>

           Customer to implement such Class A Change if it is issued within the
           Product Life for the applicable Product.

           (c)  In any of the instances above, if Corvis determines that the
           Equipment or part thereof subject to such change is readily
           returnable (e.g. plug-in items), Customer, at its expense, will
           remove and will return such Equipment or part to Corvis' facility and
           Corvis, at its expense, will implement such change at its facility
           and return such changed Equipment or part to Customer's designated
           location. Reinstallation will be performed by Customer at its
           expense.

           (d)  Corvis' undertaking under this Section 14 with respect to Vendor
           Items is limited to the extent changes comparable to Class A Changes
           are provided by the respective manufacturers of Vendor Items.

           (e)  If Customer does not make or permit Corvis to make a Class A
           Change Notification within one (1) year after the date of the related
           Change Notification, or a Class B Change within two (2) years after
           the date of the related Change Notification, subsequent changes,
           repairs, or replacements affected by the failure to make such change
           may, at Corvis' option, be billed to Customer whether or not such
           subsequent change, repair, or replacement is covered under warranty.

           (f)  If Corvis or any applicable manufacturer of a Vendor Item issues
           a Class B Change (or comparable change in the case of such
           manufacturer) after Equipment has been shipped to Customer, Corvis
           will promptly notify Customer of such change if it is being generally
           offered to Corvis' customers. When a Class B Change is requested by
           Customer, billing will be at Corvis' applicable prices or the
           respective manufacturer's then current prices to Corvis, as the case
           may be. Notwithstanding the above, there will be no charge for any
           Class B Change (or, in the case of a Vendor Item, a comparable
           change) if such change is included in the Maintenance or Support
           Services then in effect pursuant to the terms of this Agreement.

     14.3  Corvis reserves the right to discontinue any product that is a
           Product under this Agreement if Customer has not ordered any of that
           Product for two consecutive years. Corvis will provide a minimum of
           90 days' prior notice for Products being discontinued.

     14.4  Corvis reserves the right to develop, manufacture and market Products
           incorporating new features, functionality, or performance
           characteristics identified as a result of its relationship with
           Customer. Customer acknowledges that such Products will be the sole
           and exclusive property of Corvis.

ARTICLE 15.  PROPRIETARY INFORMATION.

                                      12
<PAGE>

     15.1  Each party acknowledges the other party's ownership of trade secrets,
     proprietary or confidential information, including but not limited to
     products, planned products, services or planned services, the identity of
     or information concerning customers or prospective customers, data,
     financial information, computer software, processes, methods, knowledge,
     inventions, ideas, marketing promotions, discoveries, current or planned
     activities, research development or other information relating to the other
     party's business activities or operations and those of its customers or
     subcontractors, as well as the pricing and other terms and conditions of
     this Agreement (collectively referred to hereinafter as the "Proprietary
     Information").

     15.2  (a)  This Agreement creates a confidential relationship between
           Customer and the Corvis and, in the course of, negotiating or
           performing this Agreement, including providing Products pursuant to
           this Agreement, the disclosing party may disclose Proprietary
           Information to the receiving party. The receiving party will keep
           Proprietary Information confidential and, except as directed or
           authorized in writing, will use Proprietary Information only to
           provide the Products and services pursuant to this Agreement and will
           not disclose to any person or entity, directly or indirectly, in
           whole or in part, any Proprietary Information, information prepared
           from Proprietary Information, or information that comes into
           possession by reason of services hereunder. Dissemination of
           Proprietary Information will be limited to the personnel within the
           receiving party's organization with a need to know and solely for the
           purpose of the performance of duties hereunder. Upon cessation of
           work hereunder, the receiving party will return or destroy and
           certify to the disclosing party such destruction of all documents,
           papers and other materials in its control that contain or relate to
           Proprietary Information. To the extent practicable all proprietary
           information disclosed to the receiving party will be promptly
           identified as such by the disclosing party in writing.

           (b)  The receiving party will protect the Proprietary Information
           from unauthorized use or disclosure by exercising the same degree of
           care that it uses with respect to information of its own of a similar
           nature, but in no event less than reasonable care.

     15.3  Customer acknowledges and agrees that the Products constitute and
     embody the valuable trade secrets and intellectual property of Corvis
     developed at great expense to Corvis. Customer may not sell, assign or
     otherwise transfer any of the Products to a third party other than a
     telecommunications carrier for its own internal use in providing
     telecommunication services, without the prior written consent of Corvis,
     which consent will not be unreasonably withheld. Customer agrees that it
     would be reasonable for Corvis to withhold its consent to any such sale,
     assignment or transfer of any Product to a company involved in the
     development, marketing, distribution or sale of any products that are
     competitive with the Products.

     15.4  Notwithstanding anything to the contrary contained herein, no
     information will be deemed Proprietary Information if the party receiving
     such information hereunder or any of its Affiliates ("Receiving Party") can
     demonstrate that such information: (a) is generally

                                      13
<PAGE>

     known to the public on the date of disclosure of same or becomes generally
     known to the public after such date through no breach of this Agreement or
     any other obligation of confidentiality; (b) was known by the Receiving
     Party without any obligation to hold it in confidence at the time of
     disclosure; (c) is received by the Receiving Party after the date of
     disclosure by the other party or any of its affiliates ("Disclosing Party")
     from a third party without breach of any obligation of confidentiality and
     without any obligation of confidentiality binding upon the Receiving Party;
     (d) is independently developed by the Receiving Party after the date of
     disclosure by employees without access to Proprietary Information of the
     Disclosing Party; (e) is approved for release by written authorization of
     the Disclosing Party, but only to the extent of and subject to such
     conditions as may be imposed in such written authorization; (f) is required
     by law, rule or regulation, including requirements of the applicable
     securities exchanges, to be disclosed, but only to the extent and for the
     purposes of such required disclosure and subject to Section 15.5; or (g) is
     disclosed in response to a valid order of a court or other governmental
     body, but only to the extent of and for the purposes of such order and
     subject to Section 15.5.

     15.5   If a Receiving Party is or may be required by law or court order to
     disclose any Proprietary Information of a Disclosing Party, such Receiving
     Party: (a) will provide to such Disclosing Party immediate notice of such
     possible disclosure; and (b) will permit such Disclosing Party, at its
     expense, to take all reasonable actions to eliminate such requirement of
     such disclosure, to limit the scope of same and to obtain protective orders
     to protect the confidentiality of such Proprietary Information, including,
     without limitation, filing motions and otherwise making appearances before
     the court.

     15.6   The provisions of this Article 15 will survive any termination or
     expiration of this Agreement.

ARTICLE 16.  WARRANTIES, AND WARRANTY EXCLUSIONS AND LIMITATIONS.

     16.1   Corvis warrants, to Customer only, that (i) for the applicable
     warranty period set forth in Attachment 16.1 ("Warranty Period") and
     subject to the support limitations set forth in Attachment 19, the Corvis
     Equipment and Software (as applicable) will be free from defects in
     material and workmanship, will conform in all material respects to its
     Technical Requirements, (ii) upon delivery, the Equipment will be free from
     all liens and encumbrances, and (iii) Corvis' Services will be performed in
     a workmanlike manner and in accordance with good usage and accepted
     practices in the community in which services are provided. With respect to
     any Third Party Software or any Equipment furnished by Corvis but neither
     manufactured by Corvis nor purchased by Corvis pursuant to its procurement
     specifications (e.g., items such as personal computers and products offered
     as accessories to the Corvis Products) ("Vendor Items"), Corvis does hereby
     assign to Customer the warranties given to Corvis by its vendor(s) of such
     Vendor Items to the fullest extent permitted by such warranties.

                                      14
<PAGE>

     16.2   With respect to Products repaired or replaced during the applicable
     Warranty Period, Corvis warrants, for a period equal to the greater of (i)
     the remaining unexpired portion of such Warranty Period, or (ii) 30 days
     from the date the repair is effected, in the case of Products repaired at
     the installation site, and from the date a replacement is shipped to
     Customer, in the case of defective Products that are replaced, that such
     Products will satisfy and perform in accordance with the warranty set forth
     in clause (i) in Section 16.1, throughout such time period.

     16.3   Corvis will continue to make available for purchase by Customer
     repair parts for Corvis' Products furnished pursuant to this Agreement so
     long as Corvis is manufacturing or stocking such equipment or repair parts,
     but in no event less than the Product Life for the Product.

     16.4   Corvis may use either new or remanufactured, reconditioned or
     refurbished Equipment or parts if in like-new condition, or functionally
     equivalent Equipment or parts (at equivalent or comparable prices) in the
     furnishing of repairs or replacements under this Agreement. Corvis will
     have appropriate safeguards and systems in place to assure that parts
     previously determined to be defective are not reused unless they have been
     proven to be in compliance with applicable specifications.

     16.5   Corvis warrants that it has good marketable title to the Equipment,
     that it has the full power and authority to grant the license granted
     Customer under this Agreement with respect to the Licensed Software, and to
     Corvis' knowledge, neither the license to nor use by Customer of the
     Licensed Software or Equipment, as permitted under this Agreement, will
     constitute an infringement or other violation of any copyright, patent,
     trade secret, trademark, non-disclosure, or any other intellectual property
     right of any third party.

     16.6   THE FOREGOING WARRANTIES IN THIS ARTICLE 16 ARE THE EXCLUSIVE
     WARRANTIES WITH RESPECT TO ANY OF THE PRODUCTS OR SERVICES PROVIDED
     HEREUNDER, AND ARE IN LIEU OF ALL OTHER EXPRESS AND IMPLIED WARRANTIES,
     INCLUDING BUT NOT LIMITED TO WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     A PARTICULAR PURPOSE. CUSTOMER'S SOLE AND EXCLUSIVE REMEDY WILL BE CORVIS'
     OBLIGATION TO REPAIR OR REPLACE OR, SUBJECT TO THE CONDITIONS STATED IN
     THIS ARTICLE 16 AND IN ARTICLE 18, TO CREDIT OR REFUND AS SET FORTH SECTION
     18.1.

     16.7   In the event that Customer (i) makes any unauthorized modifications
     to the Equipment or Software, or (ii) uses the Equipment or Software in the
     core optical network in connection with any other equipment or software not
     approved by Corvis, the Equipment and Software warranty will be voided with
     respect to the Equipment or Software modified or used with unapproved
     equipment or software. Corvis and Customer agree to cooperate to plan the
     configuration of Customer's network to optimize its efficiency.

     16.8   Corvis makes no warranty with respect to defective conditions or
     non-conformities resulting from the following: Customer (including third
     parties contracted by Customer) modifications, misuse, neglect, accident or
     abuse; improper wiring, repairing, splicing,

                                      15
<PAGE>

     alteration, installation, storage or maintenance by Customer (or third
     parties contracted by Customer); use in a manner not in accordance with the
     applicable specifications, or operating instructions or failure of Customer
     to apply previously applicable Corvis' modifications or corrections. In
     addition, Corvis makes no warranty with respect to Products which have had
     their serial numbers or month and year of manufacture removed, altered and
     with respect to expendable items. Corvis makes no warranty with respect to
     defects related to Customer's database errors. Moreover, no warranty is
     made that Software will run uninterrupted or error free.

     16.9   Customer agrees not to use any third party equipment or software in
     connection with the Corvis Equipment and Software other than to the [*]
     interfaces of the Corvis [*] and [*] modules, the [*] and order wire
     interfaces, or to the network management interfaces provided on the Corvis
     Equipment and Software. Customer shall pay Corvis a right to use annual
     license fee equal to 25% of the current price of the Corvis products
     equivalent to any third party equipment or software used in connection with
     Corvis Equipment and Software other than in a manner set forth above.
     Customer represents and warrants that the Products are being acquired
     hereunder for Customer's internal use and not for resale to any third
     party.

ARTICLE 17.  REPRESENTATIONS AND OTHER WARRANTIES.

     17.1   Each party represents and warrants that it is duly organized,
     existing and in good standing under the laws of its State of organization,
     and is duly qualified as a foreign corporation and in good standing in all
     jurisdictions in which the failure to so qualify would have a materially
     adverse impact upon its business and assets.

     17.2   Each party represents and warrants that it has the corporate power
     and requisite authority to execute, deliver and perform this Agreement, any
     Escrow Agreement entered into pursuant to this Agreement, and all Purchase
     Orders to be executed pursuant to or in connection with this Agreement, and
     that it is duly authorized to, and has taken all corporate action necessary
     to authorize, the execution, delivery and performance of this Agreement and
     such other agreements and documents.

     17.3   Each party represents and warrants that neither the execution and
     delivery of this Agreement and the agreements or documents stated in
     Section 17.2 above executed by it pursuant to or in connection with this
     Agreement, nor the consummation of any of the transactions herein or
     therein contemplated, nor compliance by it with the terms and provisions
     hereof or with the terms and provisions thereof will (i) contravene or
     materially conflict with any provision of applicable law to which it is
     subject or any judgment, license, order or permit applicable to it, or any
     indenture, mortgage, deed of trust, or other agreement or instrument to
     which it is a party or by which it or its property may be bound, or to
     which it or its property may be subject, (ii) violate any provision of its
     articles of incorporation or bylaws or partnership agreement, if any or
     (iii) require the consent or approval of, the giving of notice to, or the
     registration, recording or filing of any document

                                      16
<PAGE>

     with, or the taking of any other action in respect of, any person, entity
     or governmental agency.

     17.4   Each party represents and warrants that this Agreement and the
     agreements or documents stated in Section 17.2 above executed by it
     pursuant to or in connection with this Agreement will constitute when
     executed in full the legal, valid and binding obligations of said party,
     enforceable in accordance with their respective terms, subject to
     applicable bankruptcy, insolvency, reorganization, fraudulent transfer,
     moratorium or similar laws affecting the enforcement of creditors rights
     generally and to general principles of equity.

ARTICLE 18.  REMEDIES AND LIMITATIONS.

     18.1   If, under normal and proper use (i.e., as approved by Corvis or as
     provided in the applicable Technical Requirements) any Product fails to
     conform to the warranty specified in Article 16 during the applicable
     Warranty Period, Corvis will promptly repair or replace, at its option and
     expense, all such defective or nonconforming Product so as to cause it to
     satisfy, and perform in accordance with, its applicable Technical
     Requirements. If Corvis cannot repair or replace such Product, it will
     provide a refund or credit for the original purchase price or license fee
     paid by Customer for such Product. If Corvis' installation services prove
     not to be performed as warranted, within a six (6) month period commencing
     on the date of Acceptance of the Services, Corvis, at its option, either
     will correct the defect or non-conforming Services or render a full or pro-
     rated refund or credit based on the original charges for the Services. No
     Product will be accepted for repair or replacement without the written
     authorization of and in accordance with reasonable instructions of Corvis.
     Removal and reinstallation expenses as well as transportation expenses
     associated with returning such Product to Corvis for readily returnable
     Products (e.g., plug-in items) will be borne by Corvis only if Corvis
     performed improper installation services necessitating such removal and
     reinstallation. Corvis will pay the costs of transportation of the repaired
     or replaced Product to the destination designated by Customer. In repairing
     or replacing any Equipment or Software medium under this warranty, Corvis
     may use either new Products or parts or remanufactured, reconditioned or
     refurbished Products or parts if in like-new condition or functionally
     equivalent Products or parts. Replaced Products or parts will be retained
     by Corvis and become Corvis' property. Replacement Products or parts become
     the property of Customer.

     18.2   In the event Customer returns Products for repair that are not
     defective, Corvis may require that Customer pay with respect to any
     subsequently returned Products which prove not to be defective a fee which
     reflects Corvis' cost of handling, inspecting and testing and, if
     applicable, travel and related expenses by Corvis' employees.

     18.3   The parties acknowledge that disclosure of any Proprietary
     Information other than as allowed by Articles 12 or 15 may give rise to
     irreparable injury and may be inadequately compensable in monetary damages
     and therefore the non-disclosing party will be entitled to seek and to
     obtain injunctive or other equitable relief against the breach or
     threatened

                                      17
<PAGE>

     breach of the obligations of said Articles 12 or 15, in addition to any
     other remedies which may be available.

     18.4   The remedies available to either party under this Agreement are
     cumulative. The exercise of any one remedy will not be deemed an election
     of such remedy to the exclusion of other remedies; and the rights and
     remedies of the parties as set forth in this Agreement are not exclusive
     and are in addition to any other rights and remedies available to it at law
     or in equity.

     18.5   EXCEPT FOR CORVIS' INDEMNITY OBLIGATIONS SET FORTH IN ARTICLES 21
     AND 22, ANYTHING IN THIS AGREEMENT TO THE CONTRARY NOTWITHSTANDING, (I) THE
     MAXIMUM AGGREGATE AMOUNT THAT CUSTOMER WILL BE PERMITTED TO RECOVER BECAUSE
     OF A DEFECTIVE PRODUCT OR DEFICIENT SERVICE WILL NOT EXCEED THE NET PRICE
     OF SUCH PRODUCT OR SERVICE INVOICED TO CUSTOMER, AND (II) CORVIS' LIABILITY
     TO CUSTOMER UNDER THIS AGREEMENT OR IN CONNECTION WITH ANY OTHER MATTERS
     WILL NOT EXCEED IN THE AGGREGATE NET PRICE PAID TO CORVIS UNDER THIS
     AGREEMENT DURING THE TWELVE-MONTH PERIOD PRECEDING THE EVENT GIVING RISE TO
     SUCH LIABILITY.

     18.6   NOTWITHSTANDING ANY OTHER PROVISION OF THIS AGREEMENT, CORVIS AND
     ITS AFFILIATES, AND THEIR DIRECTORS, EMPLOYEES AND AGENTS WILL NOT BE
     LIABLE FOR ANY INCIDENTAL, INDIRECT, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     DAMAGES OR LOST PROFITS, REVENUES OR SAVINGS ARISING OUT OF THIS AGREEMENT,
     OR THE USE OR PERFORMANCE OF ANY PRODUCT OR SERVICES, WHETHER IN AN ACTION
     FOR OR ARISING OUT OF BREACH OF CONTRACT, TORT, INCLUDING NEGLIGENCE,
     INDEMNITY OR STRICT LIABILITY. THIS PARAGRAPH WILL SURVIVE FAILURE OF AN
     EXCLUSIVE OR LIMITED REMEDY. THE FOREGOING WILL NOT BE DEEMED TO LIMIT
     CORVIS' INDEMNITY OBLIGATIONS UNDER SECTION 22.

     18.7   ANY ACTION OR PROCEEDING BY EITHER PARTY UNDER THIS AGREEMENT MUST
     BE BROUGHT WITHIN FORTY-EIGHT (48) MONTHS AFTER THE DATE SUCH PARTY KNOWS
     OR SHOULD HAVE KNOWN THAT SUCH CAUSE OF ACTION HAS ACCRUED.

ARTICLE 19.  SUPPORT AND OTHER SERVICES.

     19.1   Customer will purchase the maintenance and support services
     ("Maintenance and Support Services") identified in Attachment 19 for the
     Products. Customer may purchase additional maintenance and support services
     at Corvis prevailing time and materials rates, upon mutually agreeable
     terms.

ARTICLE 20.  INSURANCE.

                                      18
<PAGE>

     20.1   Corvis will procure and maintain, during the Term of this Agreement
     insurance in not less than the following amounts:

            (a)  Worker's Compensation insurance in accordance with the
            provisions of the applicable Workers' Compensation or similar law of
            the state with jurisdiction applicable to Corvis' personnel.

            (b)  Commercial General Liability, including Contractual Liability
            insurance with a coverage limit of not less than five million
            dollars ($5,000,000) combined single limit per occurrence for bodily
            injury or property damage liability

            (c)  If the use of any automobile is required by the Corvis or any
            third party acting on behalf of Corvis in the performance of this
            Agreement, Corvis will also obtain and maintain business auto
            liability insurance for the operation of all owned, non-owned and
            hired automobiles with a coverage limit of not less than one million
            dollars ($1,000,000) combined single limit per accident for bodily
            injury or property damage liability.

     20.2   Corvis will deliver to Customer certificates of insurance
     satisfactory in form and content to Customer evidencing that all of the
     insurance required by this Agreement is in force, and that no policy may be
     canceled or materially altered without first giving Customer at least
     thirty (30) days prior written notice.

ARTICLE 21.  INDEMNIFICATION.

     21.1   Corvis will be responsible for and agree to indemnify and hold
     harmless Customer from and against all losses, liabilities, demands,
     claims, actions, proceedings, suits and damages (including reasonable legal
     fees) for injury to persons or damage to tangible property to the extent it
     results directly from the intentional or negligent acts or omissions, or
     strict liability, of Corvis, its officers, agents, employees, or
     contractors.

     21.2   Customer will be responsible for and agrees to indemnify and hold
     harmless Corvis from and against all losses, liabilities, demands, claims,
     actions, proceedings, suits and damages (including reasonable legal fees)
     for injury, including death, to persons or damage to tangible property to
     the extent it results directly from the intentional or negligent acts or
     omissions, or strict liability, of Customer, its officers, agents,
     employees or contractors.

     21.3   With respect to each of Sections 21.1 and 21.2 above, the
     indemnified party will give the indemnifying party prompt written notice of
     all such claims, actions, proceedings or suits and the indemnifying party
     will have the sole defense thereof, including appeals, and the sole right
     to settle the same; provided, however, that the indemnifying party will not
     agree to any settlement which imposes liability or obligation on the
     indemnified for which the indemnified party is not fully indemnified
     without first obtaining the indemnified party's

                                      19
<PAGE>

     consent. The indemnified party will, upon the indemnifying party's request
     and at the indemnifying party's expense, furnish all relevant information
     available to the indemnifying party and cooperate and assist the
     indemnifying party in every reasonable way to facilitate the defense and/or
     settlement of any such claim, action, proceeding or suit.

ARTICLE 22.  PATENT, COPYRIGHT AND TRADE SECRET.

     22.1.  In the event of any claim, action, proceeding or suit by a third
     party against Customer alleging an infringement of any patent, copyright,
     or trademark, or a violation or misappropriation of any trade secret or
     other proprietary rights by reason of the purchase, license or use, in
     accordance with Corvis' specifications, of any Product (other than Third
     Party Software) furnished by Corvis to Customer under this Agreement,
     Corvis, at its expense, will defend Customer, subject to the conditions and
     exceptions stated below. Corvis will reimburse Customer for any reasonable
     cost, expense or attorneys' fees, which Customer is required to incur
     cooperating with Corvis at Corvis' request in the defense or settlement of
     such action. Corvis will indemnify Customer against any liability assessed
     against Customer by final judgment on account of such action, proceeding or
     suit. The foregoing indemnity with respect to patent, trademark and
     copyright infringement arising from Products sold or licensed for use in
     the United States or another designated country is limited to the patents,
     trademarks, and copyrights enforced under the laws of the United States or
     such other designated country, as applicable.

     22.2.  Corvis' obligation to indemnify Customer pursuant to this Article 22
     is contingent upon (i) Customer giving Corvis prompt written notice of all
     such claims, actions, proceedings or suits alleging infringement or
     violation, (ii) Customer tendering to Corvis full and complete authority to
     assume the sole defense thereof, including appeals, and the sole right to
     settle same, and (iii) Customer furnishing to Corvis all relevant
     information available to Customer and cooperating with and assisting Corvis
     in every reasonable way to facilitate the defense and/or settlement of any
     such claim, action, proceeding or suit.

     22.3.  If Customer's use is enjoined or in Corvis' opinion is likely to be
     enjoined, Corvis will, at its expense and at its option, either (1) replace
     the enjoined Product furnished pursuant to this Agreement with a suitable
     substitute free of any infringement, provided such substitute has
     comparable functionality and performance characteristics; (2) modify it so
     that it will be free of the infringement, provided such modification does
     not result in a material degradation in performance or functionality; or
     (3) procure for Customer a license or other right to use it. If none of the
     foregoing options are available to Corvis on a commercially reasonable
     basis, Corvis will remove the enjoined Product, and refund to Customer any
     amounts paid to Corvis therefor less the amortized value of the Product(s)
     based on the applicable Product Life.

     22.4.  No undertaking of Corvis under this Article will extend to any such
     alleged infringement or violation to the extent that it: (1) arises from
     adherence to design modifications, specifications, drawings, or written
     instructions which Corvis is directed by Customer to follow; or (2) arises
     from adherence to instructions to apply Customer's

                                      20
<PAGE>

     trademark, trade name or other company identification; or (3) arises from a
     third party products, including any Third Party Software, furnished by
     Customer to Corvis for use under this Agreement; or (4) relates to uses of
     a Product provided by Corvis in combinations with other products furnished
     either by Corvis or Customer. In the foregoing cases numbered (1) through
     (4), Customer will defend and save Corvis harmless, subject to the same
     terms and conditions and exceptions stated above, with respect to the
     Corvis' rights and obligations under this Article. Corvis hereby assigns to
     Customer any rights which Corvis may have to indemnity from the original
     manufacturer with respect to any Vendor Item provided under this Agreement.

     22.5.  The liability of Corvis with respect to any and all claims, actions,
     proceedings or suits by third parties alleging infringement of patents,
     trademarks or copyrights or violation of trade secrets or other proprietary
     rights because of, or in connection with, any Products furnished pursuant
     to this Agreement will be limited to the specific undertakings contained in
     this Article.

ARTICLE 23.  TERMINATION.

     23.1   Either party may terminate this Agreement and any outstanding
     Purchase Order, in whole or in part, in the event of a default by the
     other, provided that the non-defaulting party so advises the defaulting
     party in writing of the event of alleged default and affords the defaulting
     party thirty (30) days within which to cure the default. Default is defined
     to include:

            (a)  Either party becomes insolvent, makes a general assignment for
            the benefit of creditors, files a voluntary petition in bankruptcy
            or an involuntary petition in bankruptcy is filed against such party
            which is not dismissed within sixty (60) days after the date such
            petition is filed, or suffers or permits the appointment of a
            receiver for its business, or its assets become subject to any
            proceeding under a bankruptcy or insolvency law, domestic or
            foreign, or has liquidated its business;

            (b)  Either party's material breach of any of the terms or
            conditions hereof;

            (c)  The execution by either party of an Assignment for the benefit
             of creditors or any other transfer or assignment of similar nature;
             or

            (d)  Termination by either party of the Transport Field Trial
            pursuant to Section 2.1(c).

     23.2   Neither the expiration of this Agreement according to its terms nor
     its termination under the provisions of Section 23.1 will prejudice any
     claim for any outstanding amount owed Corvis and Customer to each other,
     damages or any other rights or remedies that any party may have under this
     Agreement or at law or in equity or relieve any party from the duty to hold
     in confidence proprietary information and otherwise comply with, and
     exercise

                                      21
<PAGE>

     the rights set forth in, Articles or Sections 5.3, 6.1 (Right to Use Fee),
     14.1, 15, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26, and 28 hereof, each of
     which will survive such termination.

ARTICLE 24.  DISPUTE RESOLUTION.

     24.1   The parties will attempt in good faith to resolve promptly any
     controversy or claim arising out of or relating to this Agreement or any
     subsequent performance by the parties before resorting to other remedies
     available to them. Any such dispute will be referred to appropriate
     executives of each party who will have the authority to resolve the matter.
     If the executives are unable to resolve the dispute, the parties may by
     agreement refer the matter to an appropriate form of alternative dispute
     resolution such as mediation. If the parties cannot resolve the matter or
     if they cannot agree upon an alternative form of dispute resolution, then
     either party may pursue resolution of the matter through arbitration in
     accordance with the rules of the American Arbitration Association (the
     "AAA") applying the substantive law of the State of Delaware without regard
     to any conflict of laws provisions. The arbitration will be conducted by a
     panel of three (3) arbitrators selected in accordance with the rules of the
     AAA. Each arbitrator will be an attorney familiar with telecommunications
     technology and the telecommunications industry. The arbitration will be
     governed by the United States Arbitration Act, 9, U.S.C. Section 1, et.
     seq. and judgment upon the award rendered by the arbitrators may be entered
     by any court with jurisdiction. The arbitrators are not empowered to award
     damages in excess of compensatory damages, and each party waives any
     damages in excess of compensatory damages.

     24.2   Notwithstanding the foregoing, either party may bring a claim for
     injunctive relief as provided in Section 18.3 in any court of competent
     jurisdiction without first submitting the claim to arbitration.

ARTICLE 25.  NOTICE AND REPRESENTATIVES OF THE PARTIES.

     Any notice ("Notice") required or permitted under this Agreement must be
     given in writing to the address or facsimile number provided for a party
     below (or such other address or number as any party may provide to the
     other in writing in the manner contemplated hereby) and will be deemed
     effective as follows:

            (a)  if delivered in person or by courier, on the date it is
            delivered;

            (b)  if sent by facsimile transmission, on the date that the
            transmission is received by the recipient party in legible form;

            (c)  if sent by certified or registered mail or the equivalent
            (return receipt requested), on the date that mail is delivered or
            its delivery is attempted but acceptance is refused; unless the date
            and time of any delivery or receipt, as applicable, is not during
            normal working hours on a local business day, in which case Notice
            will be deemed given and effective on the first following day that
            is a

                                      22
<PAGE>

            local business day. For purposes hereof, a "local business day" is a
            business day in the city specified in the address for notice
            provided by the recipient.

     The Notices provided for by this Article 25 will be given to the following:

            If to Customer:

            Broadwing Communications Services Inc.
            ATTN: Mike Guess, Vice President of Engineering
            1835-B Kramer Lane
            Austin, Texas 78758

            If to Customer:

            Broadwing Communications Services Inc.
            Attn: Contract Administration
            Rm 102-260
            201 E. Fourth Street
            Cincinnati, OH 45202

            With a copy to:

            Broadwing Communications Services, Inc.
            Office of General Counsel
            1122 Capital of Texas Highway South
            Austin, Texas 78746

            If to Corvis:

            Corvis Corporation
            ATTN: General Counsel
            7015 Albert Einstein Drive
            PO Box 9400
            Columbia, Maryland 21046-9400
            Telephone: 443.259.4110

ARTICLE 26.  GENERAL

     26.1   Assignment. Neither party to this Agreement may assign, transfer,
     pledge, encumber or hypothecate its interest in this Agreement or any of
     its rights hereunder or delegate its obligations hereunder without the
     prior written consent of the other party to this Agreement, which consent
     will not be unreasonably withheld, and any attempted assignment which does
     not comply fully with this Article 26.1 will be null and void.
     Notwithstanding the foregoing, (i) Customer may assign or sublicense its
     rights and obligations under Article 12 as provided in Section 12.1; and
     (ii) either Customer or Corvis may, upon prompt written notice, assign
     their respective rights and obligations

                                      23
<PAGE>

     pursuant to this Agreement to any Affiliate, as appropriate, or to their
     respective successors by consolidation or merger, or the transferee of
     substantially all of the assets of either, so long as Customer or Corvis,
     as appropriate, remains liable under this Agreement and in such event this
     Agreement will be binding upon and inure to the benefit of each such
     successor or transferee.

     26.2   Governing Law. This Agreement will be construed in accordance with
     and governed by the law of the State of Delaware without regard to the
     conflict of law provisions of such state or any other jurisdiction.

     26.3   Laws and Regulations. The parties hereby agree to comply with all
     local, municipal, state, federal, foreign, governmental and regulatory
     laws, orders, codes, rules and regulations that are applicable to their
     respective performance of this Agreement.

     26.4   Amendment. Any provision of this Agreement, or any schedule, exhibit
     or rider hereto, may be amended only if such amendment is in writing and
     signed by all the parties hereto. Additions to the Corvis Products in
     Attachment 6 may be made by each party signing an additional Attachment 6
     page containing the following information: Corvis Product, Equipment
     Description, and Price.

     26.5   Waiver. Any waiver or delay in the exercise by either party of any
     of its rights under this Agreement will not be deemed to prejudice such
     party's right of termination or enforcement for any further, continuing or
     other breach by the other party.

     26.6   Successors and Assigns. The provisions of this Agreement will be
     binding upon and inure to the benefit of the parties hereto and their
     respective permitted successors and permitted assigns.

     26.7   Public Disclosures. Neither party will issue or release for
     publication any materials relating to the existence of this Agreement, the
     Products or any services to be performed pursuant to this Agreement without
     the prior written consent of the other party, which consent will not be
     unreasonably withheld.

     26.8   Severability. Whenever possible, each provision of this Agreement,
     as well as any schedule, exhibit or rider attached hereto, will be
     interpreted in such manner as to be effective and valid under applicable
     law, order, code, rule or regulation, but if any provision of this
     Agreement, as well as any schedule, exhibit or rider hereto, is held to be
     invalid, illegal or unenforceable in any respect under any applicable law,
     order, code, rule or regulation, such invalidity, illegality or
     unenforceability will not affect any other provision, schedule, exhibit or
     rider of this Agreement, but this Agreement, schedule, exhibit or rider
     will be reformed, construed and enforced in such jurisdiction as if such
     invalid, illegal or unenforceable provision, schedule, exhibit or rider had
     never been contained herein or attached hereto.

     26.9   Descriptive Headings. The descriptive headings of this Agreement are
     inserted for convenience only and do not constitute a part of this
     Agreement.

                                      24
<PAGE>

     26.10   Counterparts. This Agreement may be executed in separate
     counterparts each of which will be an original and all of which taken
     together will constitute one and the same Agreement.

     26.11   Relationship of Parties. Neither Corvis, its subcontractors,
     employees or agents will be deemed to be employees or agents of Customer,
     it being understood that Corvis, its subcontractors, employees or agents
     are independent contractors with respect to Customer for all purposes and
     at all times. This Agreement will not be construed as establishing a
     partnership or joint venture between Customer and Corvis.

     26.12   Supersession of PO. The terms and conditions of this Agreement
     supersede any pre-printed terms and conditions on any Purchase Order, both
     front and back, unless otherwise agreed by the parties in writing. Any pre-
     printed terms or conditions on any Purchase Order, other than the ordering
     information required by this Agreement, will be of no force or effect
     whatsoever.

     26.13  Customer will comply with the export control laws and regulations of
     the United States with respect to the Products purchased under this
     Agreement

ARTICLE 27.  INCORPORATION OF DOCUMENTS.

             This Agreement hereby incorporates by reference the Attachments
     referred to herein. In the event of an inconsistency or conflict between or
     among the provisions of this Agreement, the inconsistency will be resolved
     by giving precedence in the following order:

             (1)  Agreement
             (2)  Attachments
             (3)  Purchase Orders (excluding any preprinted terms and
                  conditions)

ARTICLE 28.  DEFINITIONS.

     "Affiliate" means, with respect to any entity, any other entity which
     controls, is controlled by, or under common control with, such entity; and
     "control" means ownership of a majority of the voting equity or similar
     rights of an entity.

     "Catastrophic Failure" means any event where/when a large amount of
     Customer equipment fails at a site or multiple sites thus rendering Corvis'
     Equipment to be inoperable due to Acts of God or acts not within Customer's
     control, and such repair of Equipment is beyond the normal repair and
     return or sparing capabilities established for routine maintenance. Such
     events will include but not be limited to floods, fires, malicious acts,
     vandalism and sabotage.

                                      25
<PAGE>

     "Change Notification" is defined in Section 14.2

     "Class A Change" means a modification of existing Corvis manufactured
     Equipment to remedy a non-conformance to Technical Requirements required to
     correct design defects of a type that results in electrical or mechanical
     inoperative conditions or unsatisfactory operating conditions, or which is
     recommended to enhance safety. Corvis will use standards consistent with
     its practices for all its customers in determining which modifications
     constitute Class A changes.

     "Class B Change" means an optional change, available to Customer at an
     additional cost, that provides Equipment enhancements resulting in new
     features or improved service capabilities to Corvis Equipment.

     "Committed Amounts" is defined in Section  4.3.

     "Designated Equipment" is defined in Article 12.

     "Documentation" with respect to any Product means Corvis' technical
     documentation and operating manuals for such Product.

     "Effective Date" is defined in the Preamble.

     "Equipment" or "Corvis Equipment" means the equipment that may be purchased
     from Corvis pursuant to this Agreement.

     "Final Deployment Date" is defined in Section 4.1.

     "Initial Deployment Shortfall" is defined in Section 4.2.

     "Initial Term" is defined in Section 7.

     "Licensed Software" means the Corvis software and third party software,
     each of which in machine-readable form, and subsequent Software upgrades,
     necessary to install, operate, and maintain the Products purchased or
     licensed by Customer pursuant to this Agreement.

     "Maintenance and Support Services" is defined in Section 19.

     "Net Price" means the final price paid by any Customer after all sales
     discounts, price reductions, sales rebates, volume discounts or similar
     adjustments of any kind are applied, whether under the original contract of
     purchase or any supplemental, separate, or complimentary transaction.

     "Network Element" means a material component of Corvis' fiber optic
     transmission system, including, but not limited to, optical amplifiers,
     optical routers, optical add-drop multiplexers or end nodes at given sites
     or nodes in the network.

     "Product Life" for each Product is as set out in Attachment 5.3.

                                      26
<PAGE>

     "Products" means Equipment and Software.

     "Proprietary Information" is defined in Section 15.1.

     "Purchase Order" means the document issued by Customer which identifies the
     Products and specifies the scope of work, quantities and dates for
     delivery, billing instructions, and any other necessary information.

     "Rolling Forecast" is defined in Section 4.3.

     "Services" means the services provided by Corvis to Customer as specified
     in a Purchase Order to the extent such Services are not included in the
     supply of other Products.

     "Software" refers to all the programs, computer languages, and operations
     used to make Equipment perform a useful function or used to enable human
     access to the Equipment for the purposes of installing, operating, or
     maintaining such Equipment

     "SONET" means a Synchronous Optical Network which adheres to the interface
     standard of the same name created by the Exchange Carriers Standards
     Association for the American National Standards Institute ("ANSI"), and
     promulgated by Bellcore on behalf of the Regional Bell Operating Companies.

     "Source Code" means all intellectual information including but not limited
     to Documentation, Software in human-readable form, flow charts, schematics
     and annotations which comprise the pre-coding detailed design
     specifications for Licensed Software (excluding Third Party Software).

     "Specified Site" is defined in Section 4.4.

     "System" means a configuration of Equipment with two (2) end terminals, any
     intermediate line amplifiers connected by fiber to the end terminals, all
     associated Software, which has the ability to communicate to an element
     management system such that traffic can be transmitted from end terminal to
     end terminal and operation can be monitored by the element management
     system.

     "Technical Requirements" means (i) the specifications set forth in
     appropriate industry standard telecommunications technical requirements
     where applicable or as such specifications may be most currently modified
     or amended pursuant to mutual agreement of the parties.

     "Third Party Software" means Software which is independently developed by a
     third party, sub-licensed to Customer under this Agreement or otherwise
     provided with the Products hereunder.

     "Transport Field Trial" is defined is Section 2.1.

                                      27
<PAGE>

     "Transport Field Trial Test Criteria" is defined in Section 2.1

     "Vendor Items" is defined in Section 16.1.

     "Warranty Period" is defined in Section 16.1.

ARTICLE 29.  ENTIRE AGREEMENT.

     This Agreement together with all Exhibits and Attachments constitutes the
     entire Agreement between Customer and Corvis with respect to the subject
     matter hereof and supersedes all prior agreements and understandings, both
     written and oral, between the parties with respect to such subject matter,
     and is not intended to confer upon any person other than the parties hereto
     any rights or remedies hereunder.

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed by their duly authorized representatives as of the day and year below
written.

CORVIS CORPORATION                 BROADWING COMMUNICATIONS SERVICES INC.

/s/ David R. Huber

BY: David R. Huber                 BY: /s/ Richard G. Ellenberger

TITLE: President and CEO           TITLE: President, COO

DATE: March 20, 2000               DATE: March 17, 2000

                                   /s/ Michael R. Jones
                                   Michael R. Jones
                                   Sr. Vice President
                                   Engineering

                                      28
<PAGE>

  Confidential materials omitted and filed separately with the Securities and
               Exchange Commission.  Asterisks denote omissions.

                              LIST OF ATTACHMENTS
                              -------------------

Attachment 1.1    -   Laboratory System

Attachment 1.3    -   Estimated Project Schedule

Attachment 2      -   Transport Field Trial Equipment, Software, and Services
                       Pricing

Attachment 2.1    -   Transport Field Trial Configuration and Test Criteria

Attachment 5.3    -   Product Life

Attachment 6      -   Prices for Products and Services

Attachment 11.1   -   Corvis Training

Attachment 12.1   -   Third Party Software Licenses

Attachment 12.7   -   Escrow Agreement

Attachment 16.1   -   Warranty Period

Attachment 19     -   Maintenance and Support Services and Other Services

Attachment 28     -   Product Specifications
<PAGE>

                                 ATTACHMENT 1

                               LABORATORY SYSTEM
                               -----------------

<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------------------------------------
Corvis Products & Services                                 Net             Units            Extended                   Field
                                                          Price                               Price                 Trial Price
------------------------------------------------------------------------------------------------------------------------------
<S>                                                      <C>               <C>              <C>                     <C>
Network Elements
   ONG-160 [*]                                            $[*]               [*]              $[*]                        $[*]
   OADM-160 [*]                                           $[*]               [*]              $[*]                        $[*]
   OA3200                                                 $[*]               [*]              $[*]                        $[*]
   OC [*] Tx/Rx Interfaces                                $[*]               [*]              $[*]                        $[*]
   ONG-160 [*] RTUs                                       $[*]               [*]              $[*]                         [*]
   OADM [*] RTUs                                          $[*]               [*]              $[*]                         [*]
   OA3200  RTUs                                           $[*]               [*]              $[*]                         [*]

NOC
   CorManager NOC Equipment SUN 450                       $[*]               [*]              $[*]                        $[*]
   CorManager Applications Software                       $[*]               [*]              $[*]                         [*]
   CorManager Annual Maintenance                          $[*]               [*]              $[*]                         [*]
   CorManager Installation                                $[*]               [*]              $[*]                         [*]

Corvis CorManager Services
   Engineering, Installation, System Turn-Up and Test     $[*]               [*]              $[*]                         [*]
   Training (per 3 Day Course)                            $[*]               [*]              $[*]                         [*]
   Remote TAC (per Hour)                                  $[*]               [*]              $[*]                         [*]
   On-Site Technical Support (per Day)                    $[*]               [*]              $[*]                         [*]
   Documentation                                          $[*]               [*]              $[*]                         [*]

------------------------------------------------------------------------------------------------------------------------------
Total Extended Price                                                                          $[*]
------------------------------------------------------------------------------------------------------------------------------
Total                                                                                                                     $[*]
------------------------------------------------------------------------------------------------------------------------------
</TABLE>
<PAGE>

                                ATTACHMENT 1.3

                          ESTIMATED PROJECT SCHEDULE
                          ---------------------------

<TABLE>
<CAPTION>
----------------------------------------------------------------------------------------------------------
          Event                     Date            Location                 Objective
----------------------------------------------------------------------------------------------------------
<S>                        <C>                      <C>         <C>
CUSTOMER                   Installation complete:   CUSTOMER    Install, test and turn-up trial system.
Laboratory System          March 7, 2000
Installed, Tested And      Test and Turn-up:
Turned-Up                  March 14, 2000
----------------------------------------------------------------------------------------------------------
CUSTOMER Field Trial       Commence shipment:       CUSTOMER    Install field trial system.  Delivery
System Installation        April 3, 2000                        of equipment for field trial installation.
                           Test and Turn-up
                           Complete: June 2, 2000
----------------------------------------------------------------------------------------------------------
Formal CUSTOMER            Commencing June 5,       CUSTOMER    Evaluate the Corvis system.
Field Trial Evaluation     2000
----------------------------------------------------------------------------------------------------------
</TABLE>
<PAGE>

                                 ATTACHMENT 2

        TRANSPORT FIELD TRIAL EQUIPMENT, SOFTWARE, AND SERVICES PRICING
        ---------------------------------------------------------------
<PAGE>

Fort Worth to Phoenix Transport Field Trial Pricing

The Corvis CorWave(TM) Transport Field Trial system configuration is activated
with [*] circuits. All required Network Elements, NOC network management,
engineering & installation, and documentation prices and configurations for the
Transport Field Trial system is outlined in the following table.

<TABLE>
<CAPTION>
---------------------------------------------------------------------------------------------------------------------------
Corvis Products & Services                                Net         Units               Extended           Field
                                                         Price                             Price          Trial Price
---------------------------------------------------------------------------------------------------------------------------
<S>                                                      <C>          <C>                 <C>             <C>
Network Elements
   ONG-160 [*]                                            $[*]         [*]                    $[*]              $[*]
   OADM-160 [*] (previously [*])                          $[*]         [*]                    $[*]              $[*]
   OA3200                                                 $[*]         [*]                    $[*]              $[*]
   OC [*] Tx/Rx Interfaces                                $[*]         [*]                    $[*]              $[*]
   ONG-160 [*] RTUs                                       $[*]         [*]                    $[*]               [*](A)
   OADM [*] RTUs                                          $[*]         [*]                    $[*]               [*](A)
   OA3200 RTUs                                            $[*]         [*]                    $[*]               [*](A)

NOC
   CorManager NOC Equipment SUN 450                       $[*]         [*]                    $[*]              $[*]
   CorManager Applications Software                       $[*]         [*]                    $[*]               [*](A)
   CorManager Annual Maintenance                          $[*]         [*]                    $[*]               [*](A)
   CorManager Installation                                $[*]         [*]                    $[*]               [*]

Corvis CorManager Services
   Engineering, Installation, System Turn-Up and Test     $[*]         [*]                    $[*]               [*]
   Training (per 3 Day Course)                            $[*]         [*]                    $[*]               [*]
   Remote TAC (per Hour)                                  $[*]         [*]                    $[*]               [*]
   On-Site Technical Support (per Day)                    $[*]         [*]                    $[*]               [*]
   Documentation                                          $[*]         [*]                    $[*]               [*]

---------------------------------------------------------------------------------------------------------------------------
Total Extended Price                                                                          $[*]
---------------------------------------------------------------------------------------------------------------------------
Total                                                                                                           $[*]
---------------------------------------------------------------------------------------------------------------------------
</TABLE>

(A) [*]
<PAGE>

                                 ATTACHMENT 2

             TRANSPORT FIELD TRIAL CONFIGURATION AND TEST CRITERIA
             -----------------------------------------------------

Fort Worth to Phoenix Field Trial Summary

The Corvis CorWave(TM) product is used to establish a Field Trial system that
spans from Fort Worth to Phoenix. The Field Trial system is configured in a [*]
configuration, shown in the following figure. Optical Network Gateways (ONGs)
are located in Fort Worth and Phoenix. These ONGs are connected through [*]
Optical Line Amplifiers (OLAs) and an Optical Add/Drop Multiplexer (OADM),
located in [*]. The initial configuration supports [*].

[Diagram of Fort Worth to Phoenix field trial system overlayed on a map of the
United States]
<PAGE>

Transport Field Trial Responsibilities

Corvis will conduct site surveys, fiber plant qualification, equipment
installation, equipment testing and turn-up, fiber splicing within the Broadwing
equipment rooms and limited on-site training at no charge.  Corvis is planning
to provide the appropriate number of installation and testing teams to support
the system. Corvis will deliver, install, test and turn-up the system as
outlined in the Master Project Schedule.

Broadwing agrees to a joint press release announcing the strategic partnership
with Corvis starting with the Corvis CorWave(TM) Field Trial.

Transport Field Trial Test Criteria

   Network Operations

 .  Gain Flatness/Gain Profile
   Demonstrates the spectral profile at points throughout the system. Signal
   amplitudes remain level after passing through many amplifiers for normal
   operating mode.

 .  End-to-End Jitter Test
   Demonstrates system meets Telcordia Jitter specs. (Transfer, Tolerance and
   Generation) at [*] reach interfaces.

 .  Eye Mask Test
   Verify Eye mask at Corvis Rx module (customer [*] Tributary  Side).

 .  Adjacent Channel Crosstalk ([*])
   [*] Monitor BER [*]. Drop and restore traffic [*] and verify no change in BER
   [*].

 .  FEC Error Correction Verification Test
   Demonstrates FEC circuitry functionality at the System level.

 .  Wavelength Accuracy & Control of Tx Channels
   Verifies the wavelength control of the laser diodes in the Tx module.
   Verifies the control loop [*] that maintains wavelength accuracy.

   Dynamic Performance

 .  [*] OSNR
   Demonstrates minimum system OSNR where system can maintain [*]. Also
   demonstrates system margin by measuring difference between nominal OSNR and
   minimum OSNR [*].

 .  [*] Gain Flattening
   [*] Input power is adjusted (increased or decreased) for a particular span on
   the network with the [*] or through other internal means. The [*] operator
   monitors the [*] and [*] data throughout the span to view increases and
   decreases in parameter values.

 .  [*]([*] Interface) Sensitivity Test
   Demonstrates the rapid response and settling time of the system as [*] data
   channels are [*] at the [*]. [*] Also measure BER during test to verify that
   no bit errors occur [*].

 .  [*] Dynamic Range Characterization
<PAGE>

   Typically, channel assignments are performed using the Corvis Wave Planner
   (CWP) and the Corvis Provisioning tool (CPT). The CEI application also
   provides technicians with the ability to [*]. This test verifies the CEI
   application and the CPT application can be used to [*]. The test sequence
   will include first [*] at the receiver ONG and then [*] at the transmitter
   ONG to avoid unnecessary [*] alarms generated by the receiver. The test will
   also verify that CEI and CPT users with the appropriate privileges may [*].

   Network Provisioning

 .  ONG Channel [*]
   This test verifies the CEI application and the CPT application can be used to
   [*].

   Fault Management

 .  Fiber Cut/Eye Safety Test
   Fiber cuts may occur between Line Amplifiers and a GNE (Gateway Node Element)
   or between Line Amplifiers. This test verifies that when a fiber cut occurs,
   different alarms are generated by different NEs. All affected network
   elements generate the appropriate alarms and go into eye safety shutdown
   mode.

 .  Failed Data Communication Network
   The CEM monitors the status of the DCN. If a failure is detected, then an
   alarm is generated by the CEM. This test verifies that an alarm is generated
   when a DCN failure occurs

 .  Failed CPM
   Each rack contains a [*] CPM [*]. When the [*] CPM fails,[*] and [*] has the
   Ethernet connection to be able to take over that communication. Therefore,
   the CEM [*]. If a [*] fails, the CEM detects the failure alarm, but the NE is
   still able to communicate with the CEM. Based on the type of failure, either
   a technician replaces it with a new CPM card or a new software module is
   downloaded.

   Under both conditions the other modules in the shelf should continue to work
   properly.

 .  Pump Failure
   Demonstrates the system's ability to [*] for various Amplifier pump failures
   in a span. Also demonstrates the capability of the firmware/software to
   report the appropriate alarms to the CEM operator in the event of a
   catastrophic pump module failure.

 .  Tx Failure

   Failure of a Transmitter (Tx) Module causes the next [*] down the span [*] to
   generate a loss of input alarm. The CEM receives the alarm and notifies the
   operator. The CEM will also receive the alarm from the module's [*]
   indicating that the module has failed. This test verifies that the
   appropriate alarms are generated when a Transmitter Module fails.

   Operations
   ----------

 .  Environmental Control Unit
<PAGE>

   This test case verifies the functionality of the Environmental Control Unit
   (ECU), which includes fan control, electrical power and breaker monitoring,
   and the output relays. The test will also demonstrate the Corvis Rack can
   operate with [*] disabled for at least [*] at normal operating temps.

   .  [*]
   Demonstrate functional orderwire and [*] link of the [*].

   .  Module Hot Swap Tests
   Demonstrates the systems ability to hot swap various modules [*] without
   interrupting service or system performance.
<PAGE>

                                ATTACHMENT 5.3

                                 PRODUCT LIFE
                                 ------------

                The Product Life for each Product is [*] years.
<PAGE>

                                  ATTACHMENT 6

                        PRICES FOR PRODUCTS AND SERVICES
                        --------------------------------

<TABLE>
<CAPTION>
      CORVIS Product                                        Equipment Description                                  Unit Price
-----------------------------------------------------------------------------------------------------------------------------
<S>                          <C>                                                                                   <C>
ONG160/[*]                   Optical Network Gateway with support for up to [*] Gbps of capacity (any                    $[*]
                             combination of OC-48/192) Channels. Includes:  ONG, Racks, Tx/Rx Shelves, NE
                             Firmware, Power Supplies
-----------------------------------------------------------------------------------------------------------------------------
ONG160/[*]                   Optical Network Gateway with support for up to [*] Gbps of capacity (any                    $[*]
                             combination of OC-48/192).  Includes:  ONG, Racks, Tx/Rx Shelves, NE Firmware,
                             Power Supplies
-----------------------------------------------------------------------------------------------------------------------------
ONG160/[*]                   Optical Network Gateway with support for up to [*] Gbps of capacity (any                    $[*]
                             combination of OC-48/192).  Includes:  ONG, Racks, Tx/Rx Shelves, NE Firmware,
                             Power Supplies
-----------------------------------------------------------------------------------------------------------------------------
ONG160/[*]                   Optical Network Gateway with support for up to [*] Gbps of capacity (any                    $[*]
                             combination of OC-48/192). Includes:  ONG, Racks, Tx/Rx Shelves, NE Firmware,
                             Power Supplies
-----------------------------------------------------------------------------------------------------------------------------
ONG160/[*]                   Optical Network Gateway with support for up to [*] Gbps of capacity (any                    $[*]
                             combination of OC-48/192). Includes:  ONG, Racks, Tx/Rx Shelves, NE Firmware,
                             Power Supplies
-----------------------------------------------------------------------------------------------------------------------------
ONG160/[*]                   Optical Network Gateway with support for up to [*] Gbps of capacity (any                    $[*]
                             combination of OC-48/192). Includes:  ONG, Racks, Tx/Rx Shelves, NE Firmware,
                             Power Supplies
-----------------------------------------------------------------------------------------------------------------------------
ONG RTUs                     Optical Network Gateway Right to Use:  Corvis CorManager ONG-160 Node                       $[*]
                             Software
-----------------------------------------------------------------------------------------------------------------------------
OADM-[*]                     Optical Add/Drop Mux with [*] capacity support for OC48.  Includes:  Optical                $[*]
                             Amplifier, OADM, Racks, NE Firmware, Power Supplies
-----------------------------------------------------------------------------------------------------------------------------
OADM-[*]                     Optical Add/Drop Mux with [*] capacity support up to [*] Gbps of capacity (any              $[*]
                             combination of OC-48/192). Includes:  Optical Amplifier, OADM, Racks, Tx/Rx
                             Shelves, NE Firmware, Power Supplies
-----------------------------------------------------------------------------------------------------------------------------
OADM-[*]                     Optical Add/Drop Mux with [*] capacity support up to [*] Gbps of capacity (any              $[*]
                             combination of OC-48/192). Includes:  Optical Amplifier, OADM, Racks, Tx/Rx
                             Shelves, NE Firmware, Power Supplies
-----------------------------------------------------------------------------------------------------------------------------
OADM-[*]                     Optical Add/Drop Mux with [*] capacity support up to [*] Gbps of capacity (any              $[*]
                             combination of OC-48/192). Includes:  Optical Amplifier, OADM, Racks, Tx/Rx
                             Shelves, NE Firmware, Power Supplies
-----------------------------------------------------------------------------------------------------------------------------
OADM-[*]                     Optical Add/Drop Mux with [*] capacity support up to [*] Gbps of capacity (any              $[*]
                             combination of OC-48/192). Includes:  Optical Amplifier, OADM, Racks, Tx/Rx
                             Shelves, NE Firmware, Power Supplies
-----------------------------------------------------------------------------------------------------------------------------
OADM-[*]                     Optical Add/Drop Mux with [*] capacity support up to [*] Gbps of capacity (any              $[*]
                             combination of OC-48/192). Includes:  Optical Amplifier, OADM, Racks, Tx/Rx
                             Shelves, NE Firmware, Power Supplies
-----------------------------------------------------------------------------------------------------------------------------
OADM-[*] RTUs                Optical Add/Drop Mux Right to Use:  Corvis CorManager OADM-[*] Node Software                $[*]
-----------------------------------------------------------------------------------------------------------------------------
OA3200                       Optical Line Amplifier. Equipment Includes:  Optical Amplifier, NE Firmware, Power          $[*]
                             Supplies
-----------------------------------------------------------------------------------------------------------------------------
OA3200 RTUs                  Optical Line Amplifier Right to Use:  Corvis CorManager OA3200 Node Software                $[*]
-----------------------------------------------------------------------------------------------------------------------------
OC-192                       OC-192 Interface                                                                            $[*]
-----------------------------------------------------------------------------------------------------------------------------
OC-48                        OC-48 Interface                                                                             $[*]
-----------------------------------------------------------------------------------------------------------------------------
CORWave NOC 3rd Party        CorWave TM NOC Equipment (NMS 3rd party Hardware & software).
 H/W + S/W
-----------------------------------------------------------------------------------------------------------------------------
     SUN Server E450                                                                                                     $[*]
     Class
-----------------------------------------------------------------------------------------------------------------------------
     SUN Server E3500                                                                                                    $[*]
     Class
-----------------------------------------------------------------------------------------------------------------------------
     SUN Server E3500                                                                                                    $[*]
     High Availability
     Class
-----------------------------------------------------------------------------------------------------------------------------
CorWave TM NOC               CorWave TM NOC Application Software (required for each NOC work station)                    $[*]
 Application Software
-----------------------------------------------------------------------------------------------------------------------------
     License Fee             Required for each seat after the first seat per licensed copy of the NOC                    $[*]
-----------------------------------------------------------------------------------------------------------------------------
</TABLE>
<PAGE>

<TABLE>
--------------------------------------------------------------------------------------------------------------------------
                              Application Software
--------------------------------------------------------------------------------------------------------------------------
<S>                           <C>                                                                                     <C>
Annual Software               Annual Maintenance Fee for Corvis CorWave software.                    $[*]
Maintenance Fee for
CorWave NOC
--------------------------------------------------------------------------------------------------------------------------
Engineering, Installation,    Engineering, Installation, System Turn-Up and Test for Network Management (per          $[*]
System Turn-Up and Test       NOC install).
--------------------------------------------------------------------------------------------------------------------------
Engineering, Installation,    Engineering, Installation, System Turn-Up and Test for Network Elements (percentage     $[*]
System Turn-Up and Test       of all NE costs).
--------------------------------------------------------------------------------------------------------------------------
Remote TAS Non-Emergency      Remote TAS Non-Emergency Assistance @ $100/hour.                                        $[*]
Assistance
--------------------------------------------------------------------------------------------------------------------------
On site Technical Support     On site Technical Support @ $1500/day.                                                  $[*]
--------------------------------------------------------------------------------------------------------------------------
Training                      Training: $1000 per seat (a seat is a 3 day course).                                    $[*]
--------------------------------------------------------------------------------------------------------------------------
Documentation                 Per additional copy beyond what Corvis is obligated to provide pursuant to Section      $[*]
                              8.1 and per hard copy supplied
--------------------------------------------------------------------------------------------------------------------------
</TABLE>

/(A)/ [*]

Preferred Customer Pricing

In consideration of Customer's commitment to purchase from Corvis and deploy
during the Term a total dollar value of Products equal to the Minimum Deployment
Commitment and Customer's agreement to make a jointly approved press
announcement of this Agreement, Corvis agrees as follows:

(a)  If Corvis sells and ships to any Third-party Corvis Customer Qualifying
     Products upon the same terms and conditions and at pricing lower than the
     Extended Pricing and such Third-party Corvis Customer has committed to
     purchase from Corvis a total dollar value of Products less than or equal to
     the Minimum Deployment Commitment, then Corvis will adjust the Extended
     Pricing for such Qualifying Products to match the pricing offered to such
     Third-party Corvis Customer.  The parties shall agree upon a method for
     determining whether pricing extended to Third-party Corvis Customers is
     lower than that extended to Customer by developing two reference
     configurations models (one based upon a fully-loaded point-to-point
     configuration and the other based upon a fully-loaded optical network
     configuration utilizing one or more optical routers).  The foregoing method
     shall provide that the adjusted Extended Pricing shall be the pricing that
     assures that for a deployment of Products comprising the applicable
     reference configuration model, the aggregate pricing of such Products to
     Customer and the Third-party Corvis Customer would be the same.  Such
     adjusted Extended Pricing will be applied to (i) Qualifying Products
     shipped to Customer within 30 days prior to the date on which Corvis first
     shipped to such Third-party Corvis Customer such Qualifying Products at
     pricing lower than the Extended Pricing (the "Shipping Date"), or (ii)
                                                   -------------
     Qualifying Products ordered by Customer after the Shipping Date for so long
     as Corvis continues to offer such lower pricing to such Third-party Corvis
     Customer.

(b)  If, during Calendar Year 2000, Corvis sells and ships to any Third-party
     Corvis Customer Qualifying Products upon the same terms and conditions and
     at pricing lower than the Extended Pricing (as determined using the method
     agreed to pursuant to Section (a) above)
<PAGE>

     and such Third-party Corvis Customer has committed to purchase from Corvis
     a total dollar value of Products greater than the Minimum Deployment
     Commitment, then, for so long as Corvis continues to offer such lower
     pricing to such Third-party Corvis Customer, Corvis will establish a pool
     of credits ("Product Credits") based upon (A) the difference between the
                  ---------------
     Extended Pricing for such Qualifying Products and the pricing offered to
     such Third-party Corvis Customer, and (B) the quantities of such Qualifying
     Products purchased by Customer after the date on which Corvis first shipped
     to such Third-party Corvis Customer such Qualifying Products at pricing
     lower than the Extended Pricing. Product Credits will not accrue on
     Products ordered by Customer after December 31, 2000 and may be applied
     only toward the purchase of Products, subject to the terms and conditions
     in subsection (c) below. Products Credits will not be counted toward
        --------------
     meeting the Minimum Deployment Commitment.

(c)  If, during Calendar Year 2000, Customer purchases from Corvis a total
     dollar value of Products equal to or greater U.S.$75,000,000.00, then
     Customer may apply the Product Credits against orders placed on and after
     January 1, 2001 up to twenty percent (20%) of the purchase price of
     Products ordered by Customer prior to the Credit Expiration Date.

(d)  Definitions.
---  -----------

          (i)    "Calendar Year 2000" means the period commencing on and
                  ------------------
                 including January 1, 2000 and ending on and including December
                 31, 2000.

          (ii)   "Calendar Year 2001" means the period commencing on and
                  ------------------
                 including January 1, 2001 and ending on and including December
                 31, 2001.

          (iii)  "Credit Expiration Date" means either:
                  ----------------------

                  i.   December 31, 2001; or

                  ii.  if the total aggregate dollar value of Products purchased
                       by Customer from Corvis during Calendar Year 2000 and
                       Calendar Year 2001 exceeds the Minimum Revenue
                       Commitment, June 1, 2002.

          (iv)    "Extended Pricing" means the prices and license fees for the
                   ----------------
                  Products set forth in this Attachment 6, as such prices and
                  license fees may, from time to time, be adjusted in accordance
                  with subsection (a) above.

          (v)     "Qualifying Products" means Products purchased from Corvis
                   -------------------
                  for commercial deployment in North America, but not for
                  laboratory testing, field trials or other similar purposes.

          (vi)    "Third-party Corvis Customer" means any third party customer
                   ---------------------------
                  of Corvis (other than any wholly or partially owned subsidiary
                  or affiliate of Corvis) that is in direct competition with
                  Customer and has a network deployment similar to Customer's
                  network deployment in terms of scope and geographic coverage.
<PAGE>

                                ATTACHMENT 11.1

                       CORVIS EQUIPMENT TRAINING CLASSES
                       ---------------------------------

<TABLE>
<CAPTION>
----------------------------------------------------------------------------------------------------------------
Code    Class                                      Target Audience           Duration     Pre-requisites
----------------------------------------------------------------------------------------------------------------
<S>     <C>                                        <C>                       <C>          <C>
         Corvis Transport Introduction and Basic
         ---------------------------------------
T-1      Operation (HW and SW):
         ----------------------
<S>     <C>                                        <C>                       <C>          <C>
          .  Overview                              All operations personnel  5 days
          .  Operation
          .  Safety
          .  Turn-up, Provisioning and
             Maintenance
          .  Interpretation of alarm conditions

----------------------------------------------------------------------------------------------------------------
         Corvis Switching Introduction and Basic
         ---------------------------------------
T-2      Operation (HW and SW):
         ----------------------
             Overview                              All operations personnel  5 days       Course T-1
             Operation
             Safety
             Turn-up, Provisioning and
             Maintenance
             Interpretation of alarm conditions
----------------------------------------------------------------------------------------------------------------
         Transport Installation, Turn-up and Test:
         -----------------------------------------
T-3          Safety                                Installation personnel    5 days       Course T-1
             Installation, turn-up and test of
             Corvis transport Network
             Elements (ONG, OA, OADM)
----------------------------------------------------------------------------------------------------------------
        Switching Installation, Turn-up and Test:
T-4     -----------------------------------------
             Safety                                Installation personnel    3 days       Courses T-1, T-2,
             Installation, turn-up and test of                                            T-3
             Corvis switching Network
             Elements (OR)
----------------------------------------------------------------------------------------------------------------
        Network Operations:
        -------------------
T-5          Network Management System             Network Management        5 days       Courses T-1 and
             overview                              Center personnel                       T-2
             Installation
             Configuration
             Performance monitoring
             Surveillance
             Fault management
----------------------------------------------------------------------------------------------------------------
        Network Planning and Equipment
        ------------------------------
T-6     Engineering:
        ------------
             HW and SW configurations and          Network Planning and      5 days       Courses T-1, T-2
             deployment                            Engineering personnel                  and T-5
             Route and capacity planning
             Protection schemes
             Wavelength planning
             Capacity Upgrade strategies
----------------------------------------------------------------------------------------------------------------
</TABLE>
<PAGE>

<TABLE>
<CAPTION>
----------------------------------------------------------------------------------------------------------------
        Field Operations:
        -----------------
<S>     <C>                                        <C>                       <C>          <C>
T-7          Safety                                Field Technical           3 days       Courses T-1, T-2
             Fault interpretation and              personnel                              and T-5
             troubleshooting
             Capacity upgrade implementation
----------------------------------------------------------------------------------------------------------------
</TABLE>
<PAGE>

                                ATTACHMENT 12.1

                         THIRD PARTY SOFTWARE LICENSES
                         -----------------------------

<TABLE>
<CAPTION>
---------------------------------------------------------------
               Item                             Version
---------------------------------------------------------------
<S>                                          <C>
SNMP (v1) (AdventNet)                        2.0
---------------------------------------------------------------
Solstice Enterprise Manager                  3.0
---------------------------------------------------------------
Solstice OSI 8.1.1 Comm. Platform            8.1.1
---------------------------------------------------------------
JRE/JVM                                      1.1.7b and 1.1.8
---------------------------------------------------------------
</TABLE>
<PAGE>

                                ATTACHMENT 12.6

                               ESCROW AGREEMENT
                               ----------------

                     Account Number ______________________

This Agreement is effective _________________, ______ ("Effective Date") among
_____________________________________ ("Escrow Agent"), Corvis Corporation
("Depositor") and Broadwing Communications Services, Inc. ("Preferred
Beneficiary"), who collectively may be referred to in this Agreement as "the
parties."

A.   Depositor and Preferred Beneficiary have entered into a Procurement
Agreement dated ________________, ______ regarding certain proprietary
technology of Depositor (referred to in this Agreement as the "Procurement
Agreement").

B.   Depositor desires to avoid disclosure of its proprietary technology except
under certain limited circumstances.

C.   The availability of the proprietary technology of Depositor is critical to
Preferred Beneficiary in the conduct of its business and, therefore, Preferred
Beneficiary needs access to the proprietary technology under certain limited
circumstances.

D.   Depositor and Preferred Beneficiary desire to establish an escrow with
Escrow Agent to provide for the retention, administration and controlled access
of the proprietary technology materials of Depositor.

E.   The parties desire this Agreement to be supplementary to the Procurement
Agreement pursuant to 11 United States Bankruptcy Code, Section 365(n).

ARTICLE 1  --  DEPOSITS

1.1  Obligation to Make Deposit.  Within thirty (30) days following successful
     --------------------------
completion of the Transport Field Trial (as defined in the Procurement
Agreement), Depositor will deliver to Escrow Agent the proprietary technology
and other materials ("Deposit Materials") identified on Exhibit A attached
hereto. Exhibit A will be prepared and signed by Depositor and Preferred
Beneficiary.  Escrow Agent will have no obligation with respect to the
preparation, signing or delivery of Exhibit A.  (Exhibit A will be defined after
the Field Trial.)

1.2  Identification of Tangible Media.  Prior to the delivery of the Deposit
     --------------------------------
Materials to Escrow Agent, Depositor will conspicuously label for identification
each document, magnetic tape, disk, or other tangible media upon which the
Deposit Materials are written or stored. Additionally, Depositor will complete
Exhibit B to this Agreement by listing each such tangible media by the item
label description, the type of media and the quantity.  The Exhibit B (to be
defined after the Field Trial) must be signed by Depositor and delivered to
Escrow Agent with the Deposit Materials.  Unless and until Depositor makes the
initial deposit with Escrow Agent, Escrow Agent will have no obligation with
respect to this Agreement, except the obligation to notify the parties regarding
the status of the deposit account as required in Section 2.2 below.
<PAGE>

1.3  Deposit Inspection.  When Escrow Agent receives the Deposit Materials and
     ------------------
the Exhibit B, Escrow Agent will conduct a deposit inspection by visually
matching the labeling of the tangible media containing the Deposit Materials to
the item descriptions and quantity listed on the Exhibit B.  In addition to the
deposit inspection, Preferred Beneficiary may elect to cause a verification of
the Deposit Materials in accordance with Section 1.6 below.

1.4  Acceptance of Deposit.  At completion of the deposit inspection, if Escrow
     ---------------------
Agent determines that the labeling of the tangible media matches the item
descriptions and quantity on Exhibit B, Escrow Agent will date and sign the
Exhibit B and mail a copy thereof to Depositor and Preferred Beneficiary.  If
Escrow Agent determines that the labeling does not match the item descriptions
or quantity on the Exhibit B, Escrow Agent will (a) note the discrepancies in
writing on the Exhibit B; (b) date and sign the Exhibit B with the exceptions
noted; and (c) mail a copy of the Exhibit B to Depositor and Preferred
Beneficiary.  Escrow Agent's acceptance of the deposit occurs upon the signing
of the Exhibit B by Escrow Agent.  Delivery of the signed Exhibit B to Preferred
Beneficiary is Preferred Beneficiary's  notice that the Deposit Materials have
been received and accepted by Escrow Agent.

1.5  Depositor's Representations.  Depositor represents as follows:
     ---------------------------

     a.   Depositor lawfully possesses all of the Deposit Materials deposited
          with Escrow Agent;

     b.   With respect to all of the Deposit Materials, Depositor has the right
          and authority to grant to Escrow Agent and Preferred Beneficiary the
          rights as provided in this Agreement;

     c.   The Deposit Materials are not subject to any lien or other
          encumbrance;

     d.   The Deposit Materials consist of the proprietary technology and other
          materials identified in Exhibit A; and

     e.   The Deposit Materials are readable and useable in their current form
          or, if the Deposit Materials are encrypted, the decryption tools and
          decryption keys have also been deposited.

1.6  Verification.  Preferred Beneficiary will have the right, at Preferred
     ------------
Beneficiary's expense, to cause a verification of any Deposit Materials.  A
verification determines, in different levels of detail, the accuracy,
completeness, sufficiency and quality of the Deposit Materials.  If a
verification is elected after the Deposit Materials have been delivered to
Escrow Agent, then only Escrow Agent, or at Escrow Agent's  election an
independent person or company selected and supervised by Escrow Agent , may
perform the verification.

1.7  Deposit Updates.  Unless otherwise provided by the Procurement Agreement,
     ---------------
Depositor will update the Deposit Materials within 60 days after each release of
a new version of the product that is subject to the Procurement Agreement.  Such
updates will be added to the existing deposit.  All deposit updates will be
listed on a new Exhibit B and the new Exhibit B will be signed by Depositor.
Each Exhibit B will be held and maintained separately within the escrow account.
An independent record will be created which will document the activity for each
Exhibit B.  The processing of all deposit updates will be in accordance with
Sections 1.2 through 1.6 above.  All references in this Agreement to the Deposit
Materials will include the initial Deposit Materials and any updates.

1.8  Removal of Deposit Materials.  The Deposit Materials may be removed and/or
     ----------------------------
exchanged only on written instructions signed by Depositor and Preferred
Beneficiary, or as otherwise provided in this Agreement.
<PAGE>

ARTICLE 2  --  CONFIDENTIALITY AND RECORD KEEPING

2.1  Confidentiality.  Escrow Agent will maintain the Deposit Materials in a
     ---------------
secure, environmentally safe, locked facility which is accessible only to
authorized representatives of Escrow Agent . Escrow Agent  will have the
obligation to reasonably protect the confidentiality of the Deposit Materials.
Except as provided in this Agreement, Escrow Agent  will not disclose, transfer,
make available, or use the Deposit Materials. Escrow Agent  will not disclose
the content of this Agreement to any third party.  If Escrow Agent  receives a
subpoena or other order of a court or other judicial tribunal pertaining to the
disclosure or release of the Deposit Materials, Escrow Agent  will immediately
notify the parties to this Agreement.  It will be the responsibility of
Depositor and/or Preferred Beneficiary to challenge any such order; provided,
however, that Escrow Agent  does not waive its rights to present its position
with respect to any such order. Escrow Agent will not be required to disobey any
court or other judicial tribunal order.  (See Section 7.5 below for notices of
requested orders.)  Notwithstanding the foregoing, in the event that Escrow
Agent  receives any subpoena or order that is not issued pursuant to the
procedure detailed in Section 7.3, Escrow Agent  will not comply with such order
without first notifying the parties and permitting the Depositor the opportunity
to challenge such order or to seek to have such order narrowed in a manner
acceptable to the Depositor, as owner of the proprietary information embodied on
the Deposit Materials.

2.2  Status Reports.  Escrow Agent  will issue to Depositor and Preferred
     --------------
Beneficiary a report profiling the account history at least semi-annually.
Escrow Agent  may provide copies of the account history pertaining to this
Agreement upon the request of any party to this Agreement.

2.3  Audit Rights.  During the term of this Agreement, Depositor and Preferred
     ------------
Beneficiary will each have the right to inspect the written records of Escrow
Agent  pertaining to this Agreement.  Any inspection will be held during normal
business hours and following reasonable prior notice.

ARTICLE 3  --  GRANT OF RIGHTS TO ESCROW AGENT

3.1  Title to Media.  Depositor hereby transfers to Escrow Agent  the title to
     --------------
the media upon which the proprietary technology and materials are written or
stored.  However, this transfer does not include the ownership of the
proprietary technology and materials contained on the media including any
copyright, trade secret, patent or other intellectual property rights.  Title to
all such intellectual property will at all times remain vested in Depositor.

3.2  Right to Make Copies.  Escrow Agent  will have the right to make copies of
     --------------------
the Deposit Materials as reasonably necessary to perform its obligations under
this Agreement.  Escrow Agent  will copy all copyright, nondisclosure, and other
proprietary notices and titles contained on the Deposit Materials onto any
copies made by Escrow Agent .  With all Deposit Materials submitted to Escrow
Agent , Depositor will provide any and all instructions as may be necessary to
duplicate the Deposit Materials including but not limited to the hardware and/or
software needed.

3.3  Right to Transfer Upon Release. Depositor hereby grants to Escrow Agent  a
     ------------------------------
non-exclusive, non-transferable, perpetual and royalty-free license to
sublicense the Deposit Materials to Preferred Beneficiary upon any release of
the Deposit Materials for use by Preferred Beneficiary in accordance with
Section 4.5. Except upon such a release or as otherwise provided in this
Agreement, Escrow Agent  will not sublicense or otherwise transfer the Deposit
Materials or permit Preferred Beneficiary to make use of the Deposit Materials.
It is expressly understood and agreed that Escrow Agent  is not authorized to
enter into any sublicense or similar agreement with Preferred Beneficiary that
alters the terms of this Section 3.3.  In case of any conflict between the
provisions of this Section 3.3 (or Section 4.5) and the provisions of the
<PAGE>

Procurement Agreement relating to the scope of the Preferred Beneficiary's
license upon release from escrow, the provisions of the Procurement Agreement
will control.

ARTICLE 4  --  RELEASE OF DEPOSIT

4.1  Release Conditions.  As used in this Agreement, "Release Condition" will
     ------------------
mean the following:

     a.   Depositor is in material breach of its support obligations, as
          described in the Maintenance and Support Services and Other Services
          pursuant to Article 19 of the Procurement Agreement, that is not cured
          within a reasonable period of time and that has a material adverse
          impact on Preferred Beneficiary's ability to conduct its business with
          the Depositor's Products; or

     b.   Depositor is the subject of a voluntary or involuntary bankruptcy or
          dissolution proceedings (that are not discharged within 60 days after
          they are filed, in the case of involuntary proceedings).

4.2  Request for Release.   If Preferred Beneficiary believes in good faith that
     -------------------
a release condition has occurred, Preferred Beneficiary may provide Escrow Agent
written notice that a Release Condition and a request for release of the Deposit
Materials.  The request will include instructions to Escrow Agent for
accomplishing the release, and a description in full detail of the release
condition that Preferred Beneficiary believes occurred.  Escrow Agent will
immediately send the notice to Depositor by overnight carrier.

4.3  Release by Escrow Agent.  Escrow Agent  will 10 days after Depositor's
     -----------------------
receipt of the notice of request for release, release the Deposit Materials to
Preferred Beneficiary pursuant to the instructions included in the request for
release, unless Depositor disputes that a release condition has occurred.
Subject to section 5.2, Escrow Agent  will continue to store the Deposit
Materials without release pending (a) joint instructions from Depositor and
Preferred Beneficiary, (b) resolution pursuant to the Dispute Resolution
provisions or (c) order of a court.

4.4  Release of Deposit. If Escrow Agent does not receive notice that Depositor
     ------------------
disputes the condition of release and demand for submission to arbitration then
Escrow Agent  is authorized to release the Deposit materials to the Preferred
Beneficiary or if more than one beneficiary is registered to the deposit, to
release a copy of the Deposit Materials to the Preferred Beneficiary.  However,
Escrow Agent  is entitled to receive any fees due Escrow Agent before making the
release.  Any copying expense in excess of $300 will be chargeable to the
Preferred Beneficiary.  This Agreement will terminate upon the release of the
Deposit Materials held by Escrow Agent.  In the event that Escrow Agent does
receive notice that Depositor disputes the release condition and demands
arbitration and subsequently receives (a) joint instructions from Depositor and
Preferred Beneficiary; (b) resolution pursuant to the Dispute Resolution
provisions; or (c) order of a court, Escrow Agent will release a copy of the
Deposit Materials to the Preferred Beneficiary in accordance with such joint
instructions from Depositor and Preferred Beneficiary; resolution pursuant to
the Dispute Resolution provisions; or court order.  The provisions of the
second, third and fourth sentences of this Section 4.4 will apply to any such
release.

4.5  Right to Use Following Release.  Unless otherwise provided in the
     ------------------------------
Procurement Agreement, upon release of the Deposit Materials in accordance with
this Article 4, Preferred Beneficiary will have the non-exclusive, non-
transferable, right to use the Deposit Materials for the sole purpose of
continuing the benefits afforded to Preferred Beneficiary by the Procurement
Agreement.  Preferred Beneficiary will be obligated to maintain the strict
confidentiality of the released Deposit Materials, including maintaining such
Deposit
<PAGE>

Materials in a single, access restricted, and locked location. Preferred
Beneficiary will provide access to the released Deposit Materials to only those
of its personnel who require such access for supporting Customer's use of the
Products sold or licensed to Customer under the Procurement Agreement and
Customer will maintain a written list of such personnel. Without limiting the
foregoing, the Deposit Materials will also be protected as Corvis' Proprietary
Materials under Article 15 of the Procurement Agreement. Receipt by Preferred
Beneficiary of the Deposit Materials pursuant to this Article 4 does not in any
way convey title or ownership of the Depositor products or the intellectual
property rights embodied in the products. Preferred Beneficiary may subcontract
to third parties maintenance and support work permitted under this Section 4.5;
provided all such third parties enter into a written agreement containing terms
equivalent to those contained in the Procurement Agreement regarding Depositor's
confidential information and preservation of Depositor's proprietary rights.
Preferred Beneficiary will provide signed copies of all such agreements to
Depositor before providing any such party with access to the Deposit Materials.

4.6  Preferred Beneficiary will place all Deposit Materials (including all
copies and extracts thereof) in another escrow under terms similar to this
Agreement if and when Depositor is able to demonstrate to Preferred
Beneficiary's reasonable satisfaction that Depositor is able and willing to
resume performance of its support obligations, as described in the Maintenance
and Support Services pursuant to Article 19 of the Procurement Agreement.

ARTICLE 5  --  TERM AND TERMINATION

5.1  Term of Agreement.  The initial term of this Agreement is for a period of
     -----------------
one year.  Thereafter, this Agreement will automatically renew from year-to-year
unless  (a) Depositor  and Preferred Beneficiary jointly instruct Escrow Agent
in writing that the Agreement is terminated; or (b) the Agreement is terminated
by Escrow Agent  for nonpayment in accordance with Section 5.2.  If the Deposit
Materials are subject to another escrow agreement with Escrow Agent, Escrow
Agent  reserves the right, after the initial one year term, to adjust the
anniversary date of this Agreement to match the then prevailing anniversary date
of such other escrow arrangements.

5.2  Termination for Nonpayment.  In the event of the nonpayment of fees owed to
     --------------------------
Escrow Agent , Escrow Agent  will provide written notice of delinquency to all
parties to this Agreement.  Any party to this Agreement will have the right to
make the payment to Escrow Agent  to cure the default.  If the past due payment
is not received in full by Escrow Agent  within one month of the date of such
notice, then Escrow Agent  will have the right to terminate this Agreement at
any time thereafter by sending written notice of termination to all parties.
Escrow Agent  will have no obligation to take any action under this Agreement so
long as any payment due to Escrow Agent  remains unpaid.

5.3  Disposition of Deposit Materials Upon Termination. Upon termination of this
     -------------------------------------------------
Agreement, Escrow Agent  will destroy, return, or otherwise deliver the Deposit
Materials in accordance with Depositor's instructions.  If there are no
instructions, Escrow Agent  may, at its sole discretion, destroy the Deposit
Materials or return them to Depositor.  Escrow Agent  will have no obligation to
return or destroy the Deposit Materials if the Deposit Materials are subject to
another escrow agreement with Escrow Agent.

5.4  Survival of Terms Following Termination.  Upon termination of this
     ---------------------------------------
Agreement, the following provisions of this Agreement will survive:

     a.   Depositor's Representations (Section 1.5);
<PAGE>

     b.   The obligations of Escrow Agent and Preferred Beneficiary to maintain
          confidentiality with respect to the Deposit Materials;

     c.   The rights granted in the sections entitled Right to Transfer Upon
          Release (Section 3.3) and Right to Use Following Release (Section
          4.5), if a release of the Deposit Materials has been made using the
          procedure described in Article 4 prior to termination;

     d.   The obligation to pay Escrow Agent  any fees and expenses due; and

     e.   The provisions of Sections 7.1 and 7.2.

ARTICLE 6  --  ESCROW'S FEES

6.1  Fee Schedule.  Escrow Agent  is entitled to be paid its standard fees and
     ------------
expenses applicable to the services provided.  Escrow Agent  will notify the
party responsible for payment of Escrow Agent's fees at least 90 days prior to
any increase in fees.  For any service not listed on Escrow Agent 's standard
fee schedule, Escrow Agent will provide a quote prior to rendering the service,
if requested.

6.2  Payment Terms. Escrow Agent will not be required to perform any service
     -------------
unless  the payment for such service and any outstanding balances owed to Escrow
Agent are paid in full.  Fees are due upon receipt of a signed contract or
receipt of the Deposit Materials whichever is earliest.  If invoiced fees are
not paid, Escrow Agent may terminate this Agreement in accordance with Section
5.2.  Late fees on past due amounts will accrue interest at the rate of one and
one-half percent per month (18% per annum) from the date of the invoice.

ARTICLE 7  --  LIABILITY AND DISPUTES

7.1  Right to Rely on Instructions. Escrow Agent may act in reliance upon any
     -----------------------------
instruction, instrument, or signature reasonably believed by Escrow Agent to be
genuine.  Escrow Agent may assume that any employee of a party to this Agreement
who gives any written notice, request, or instruction has the authority to do
so. Escrow Agent will not be responsible for failure to act as a result of
causes beyond the reasonable control of Escrow Agent.

7.2  Indemnification. Escrow Agent will be responsible to perform its
     ---------------
obligations under this Agreement and to act in a reasonable and prudent manner
with regard to this escrow arrangement.  Provided Escrow Agent has acted in the
manner stated in the preceding sentence, Depositor and Preferred Beneficiary
each agree to indemnify, defend and hold harmless Escrow Agent from any and all
claims, actions, damages, arbitration fees and expenses, costs, attorney's fees
and other liabilities incurred by Escrow Agent relating in any way to this
escrow arrangement.

7.3  Dispute Resolution.  (a) Any dispute relating to or arising from this
     ------------------
Agreement will be resolved by arbitration under the Commercial Arbitration Rules
of the American Arbitration Association.  Unless otherwise agreed by Depositor
and Preferred Beneficiary, arbitration will take place in Boston, Massachusetts,
U.S.A.  Service of a petition to confirm the arbitration award may be made by
First Class mail or by commercial express mail, to the attorney for the party
or, if unrepresented, to the party at the last known business address.
Depositor and Preferred Beneficiary will submit any dispute relating to the
release of Deposit Materials to the jurisdiction of a board of arbitrators (the
"Board") sitting in Boston, Massachusetts for resolution and will so notify
Escrow Agent.  The Board will be selected within thirty
<PAGE>

(30) days from the date of the filing of the notice of a dispute by Escrow Agent
under Section 4.3 (or other location or time mutually agreeable to Depositor and
Preferred Beneficiary). The Board will comprise three (3) members, one selected
by Depositor, one selected by Preferred Beneficiary and the third chosen by the
two members so selected, or if they cannot agree, by the American Arbitration
Association. The sole question before the Board will be whether or not Depositor
or Preferred Beneficiary is entitled to have the Deposit Materials released from
escrow. The Board will have no authority to order a modification or amendment of
this Agreement or the Procurement Agreement. The decision of the Board will be
forthwith delivered to Escrow Agent, Depositor and Preferred Beneficiary, will
be final and binding on Depositor and Preferred Beneficiary, and judgment
thereon may be entered in any court of competent jurisdiction. Service of a
petition to confirm the arbitration award may be made by First Class mail or by
commercial express mail, to the attorney for the party or, if unrepresented, to
the party at the last known business address. The dispute resolution procedures
outlined above may be followed for any other dispute arising out of this
Agreement, but the timetables established above will be adjusted by agreement of
the effected parties to account for the event that triggers the desire of any
party to seek arbitration. The limitations on the authority of the Board
enumerated above will apply to any arbitration pursued under this Agreement.

     (b)  All fees charged by the Board will be paid by the nonprevailing party
to the arbitration.  Each of Depositor and Preferred Beneficiary, however, will
be responsible for payment of all fees and expenses connected with the
presentation of its respective case, except that the Board may award such
reasonable fees and expenses of presentation, including counsel fees, to the
prevailing party in the event that the Board determines that the contentions of
the nonprevailing party were made in bad faith or without reasonable
justification.

7.4  Controlling Law.  This Agreement is to be governed and construed in
     ---------------
accordance with the laws of the State of New York, without regard to its
conflict of law provisions.

7.5  Notice of Requested Order.  If any party intends to obtain an order from
     -------------------------
the arbitrator or any court of competent jurisdiction that may direct Escrow
Agent  to take, or refrain from taking any action, that party will:

     a.   Give Escrow Agent at least two business days' prior notice of the
          hearing;

     b.   Include in any such order that, as a precondition to Escrow Agent's
          obligation, Escrow Agent be paid in full for any past due fees and be
          paid for the reasonable value of the services to be rendered pursuant
          to such order; and

     c.   Ensure that Escrow Agent not be required to deliver the original (as
          opposed to a copy) of the Deposit Materials if Escrow Agent may need
          to retain the original in its possession to fulfill any of its other
          duties.

ARTICLE 8  --  GENERAL PROVISIONS

8.1  Entire Agreement.  This Agreement, which includes the Exhibits described
     ----------------
herein, embodies the entire understanding among the parties with respect to its
subject matter and supersedes all previous communications, representations or
understandings, either oral or written. Escrow Agent is not a party to the
Procurement Agreement between Depositor and Preferred Beneficiary and has no
knowledge of any of the terms or provisions of any such Procurement Agreement.
Escrow Agent's only obligations to Depositor or Preferred Beneficiary are as set
forth in this Agreement. No amendment or modification of this Agreement will be
valid or binding unless signed by all the parties hereto, except that Exhibit A
need not be signed by Escrow Agent, Exhibit B need not be signed by Preferred
Beneficiary and Exhibit C need not be signed.
<PAGE>

8.2  Notices.  All notices, invoices, payments, deposits and other documents and
     -------
communications will be given to the parties at the addresses specified in the
attached Exhibit C.  It will be the responsibility of the parties to notify each
other as provided in this Section in the event of a change of address. The
parties will have the right to rely on the last known address of the other
parties.  Unless otherwise provided in this Agreement, all documents and
communications may be delivered by First Class mail.

8.3  Severability.  In the event any provision of this Agreement is found to be
     ------------
invalid, voidable or unenforceable, the parties agree that unless it materially
affects the entire intent and purpose of this Agreement, such invalidity,
voidability or unenforceability will affect neither the validity of this
Agreement nor the remaining provisions herein, and the provision in question
will be deemed to be replaced with a valid and enforceable provision most
closely reflecting the intent and purpose of the original provision.

8.4  Successors.  This Agreement will be binding upon and will inure to the
     ----------
benefit of the successors and assigns of the parties.  However, Escrow Agent
will have no obligation in performing this Agreement to recognize any successor
or assign of Depositor or Preferred Beneficiary unless Escrow Agent receives
clear, authoritative and conclusive written evidence of the change of parties.

8.5  Regulations. Depositor and Preferred Beneficiary are responsible for and
     -----------
warrant compliance with all applicable laws, rules and regulations, including
but not limited to customs laws, import, export, and re-export laws and
government regulations of any country from or to which the Deposit Materials may
be delivered in accordance with the provisions of this Agreement.

8.6  Conflict of Interest.  Escrow Agent will not pay any commissions, fees or
     --------------------
rebates of significant value to any employees of Depositor or Preferred
Beneficiary, nor favor any employee of Depositor or Preferred Beneficiary with
gifts or entertainment of significant value.  If Depositor or Preferred
Beneficiary has reasonable cause to believe that this provision has been
violated, Escrow Agent agrees to cooperate with Depositor or Preferred
Beneficiary in its investigation.
<PAGE>

Corvis Corporation                       Broadwing Communications Services, Inc.
Depositor                                Preferred Beneficiary
By: _________________________________    By: _________________________________

Name:________________________________    Name:________________________________

Title:_______________________________    Title:_______________________________

Date:________________________________     Date:_______________________________

Fort Knox Escrow Services, Inc.
Escrow Agent

By:

Name:

Title:

Date:
<PAGE>

ATTACHMENT 16.1

                                WARRANTY PERIOD
                                ---------------

     The Warranty Period shall be [*] years.
<PAGE>

                                 ATTACHMENT 19

              MAINTENANCE AND SUPPORT SERVICES AND OTHER SERVICES
              ---------------------------------------------------

The Corvis Support Program includes the following maintenance services:

 .24 X 7 Corvis Networks Technical Assistance Center (TAC)

 .Emergency priority access to TAC

 .Non-emergency Technical Assistance Center (TAC)

 .Basic software maintenance (patches and maintenance releases)

 .Repair and Return - Basic

 .Repair and Return - Advanced Replacement

     The price for the Corvis Support Program is as follows:

<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------------
                                                Standard Services              Optional
           Maintenance Services                 Annual Fee as a %             Fee as of %
                                            of Network Element Price   of Network Element Price
------------------------------------------------------------------------------------------------------
<S>                                         <C>                        <C>
 Repair and Return - Basic                            [*]%
 Emergency TAC Telephone Support                      [*]%
 Basic software maintenance support                   [*]%                   $[*] per hour
 Non-emergency TAC Telephone Support                  [*]%                       [*]%
 Repair and Return - Advanced Replacement               -
------------------------------------------------------------------------------------------------------
</TABLE>

Customer must include all Corvis Products under the Standard Corvis Support
Program in order to be eligible for maintenance of any Products or the Repair
and Return - Advanced Replacement program. The Annual Fees for the Corvis
Support Program and the Repair and Return - Advanced Replacement Program are due
upon shipment of the associated Network Element (pro rated for the portion of
the calendar year remaining).  The term of the Corvis Support Program for
individual shipments made during a calendar year shall end on December 31 of
each applicable year, and shall be renewed for the ensuing 12-month period
effective January 1 of each year.  Corvis shall invoice Customer for the Corvis
Support Program at the commencement of each calendar year for such calendar
year.

Maintenance Services descriptions are provided below:

1.0  Corvis Emergency Technical Assistance Center (TAC)

     .1  Staffing and Availability The Corvis Support Program provides priority
         Customer telephonic access to the Corvis Technical Assistance Center
         (TAC) 7 days per week and 24 hours per day. Corvis will provide
         Customer with the proper telephone number and procedures for contacting
         the TAC. TAC personnel provide problem status information to Customer
         for serious problems and are the interface to Corvis Management and
         Development Engineering.

     .2  Scope of Activities In addition to support on problem determination and
         resolution, the following information and services are available
         through the TAC: technical tips, hardware information,
<PAGE>

         software release notes, information on pending software updates,
         problem status report updates, and documentation updates.

     .3  Problem Handling Procedures All problems reported to the TAC will be
         assigned a Severity Classification. The Severity Level will be agreed
         upon between Corvis and Customer according to the table below.

<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------------------------------------------
Severity                        Description                                       Escalation Procedure/Response Time
<S>       <C>                                                      <C>
 1        Critical - Customer is experiencing a network outage     Corvis VP's of Engineering and Customer Service will be
          that prevents its customers from accessing service       immediately notified.  Corvis personnel will update Customer at
          and for which there is no workaround or recovery         least hourly and will work on the problem until resolution.
          action possible.
------------------------------------------------------------------------------------------------------------------------------------
 2        Major - Customer is experiencing a problem that          Corvis Level 3 personnel will resolve the problem within four
          affects service but for which there is a work-around     hours or escalate to Development Engineering.  Corvis personnel
          or recovery action.  Business can continue although      will update Customer at least every two hours.
          performance may be degraded.
------------------------------------------------------------------------------------------------------------------------------------
 3        Minor - Customer is experiencing problems and            Severity 3 problems will be resolved by Corvis in a reasonable
          requires technical advice or a recommendation for        period of time or will be escalated to Development Engineering.
          the best solution.  Severity 3 problems have a
          reliable workaround and have, at most, a slight
          impact on the operational environment.
------------------------------------------------------------------------------------------------------------------------------------
 4        Questions (Non Emergency)                                Questions received by the TAC will be logged and answered in a
                                                                   timely manner.
------------------------------------------------------------------------------------------------------------------------------------
</TABLE>

    Corvis will meet its priority response goal as provided herein at a ninety
(90%) percent effectiveness level for any calendar month. Should Corvis fail to
meet its response goal at least seventy (90%) percent in any calendar month,
Customer maintenance Service credits of 1/12 of the Standard Maintenance Fee
will be credited back and may be applied towards renewals/future service
contracts.

    The effectiveness level shall be calculated for any given month in
accordance with the following formula with Total Missed Calls being the number
of Severity 1 and Severity 2 Support calls for which priority support was not
delivered within ten (10) minutes (Missed Calls) of the initial call.

    Effectiveness Calculation equals: Total Calls per Month - Total Missed Calls
                                      ------------------------------------------
                                              Total Calls per Month

2.0  Software Maintenance Support.   Software Maintenance Support is also
provided through the TAC.  Software Maintenance includes patch releases of
software to correct reported problems, maintenance releases, upgrades to system
base software in new releases and other software updates that are made generally
available at no additional charge from time to time.  Software maintenance
releases will be made available via magnetic media or remote download, as
appropriate.  Major releases are anticipated to be made by Corvis once per year.
New software features and functionality offered in major new releases, if priced
separately, are not included in Software Maintenance Support. Additionally, any
incremental hardware required to support additional software is priced
separately.

    In addition to software patches and maintenance releases, Corvis will
provide Customer with revision releases, including installation, verification,
and uninstall procedures, and other documentation, pertaining to problem status,
code corrections, work-around procedures and known limitations of Corvis
products.
<PAGE>

     In addition to the individual software releases referred to above, Corvis
will from time to time make available to Customer, subject to the applicable
license fees, "Baseline Package Releases" consisting of groups of Corvis'
software Products. Notwithstanding anything to the contrary in the Agreement,
Corvis will only be obligated to provide support for the current and two (2)
immediately preceding Baseline Package Releases made available by Corvis.
Corvis' obligation to support any version of Third Party Software will be
subject to the continuing availability of support from the third party vendor
for such version. Corvis will not be obligated to provide services to correct
any error or defect in any Corvis Product that can be corrected by Customer's
installation of a more recent software release available from Corvis.

3.0  Repair and Return.  Basic

     Corvis will supply replacement components for Products that have failed.
The customer is responsible for first calling Corvis Customer Repair and getting
a Return Material Authorization number. The customer is responsible for sending
the faulty component to the Corvis designated location along with the assigned
RMA# for that module/component. Customer is responsible for packing material,
shipping enclosure and all necessary documentation to facilitate the return of
the defective component to Corvis. Requests for Basic Repair and Return on
replacement module/components received by Corvis by 3:00 p.m. Eastern Time will
generally be processed and sent back to customer within 5 days of receiving the
faulty module/component. Requests made after 3:00 p.m. Eastern Time or on
weekends or Corvis holidays will be processed the next business day.

4.0  Repair and Return.  Advanced Replacement

     Corvis will supply replacement components for products that have failed. As
a prerequisite to advance replacement service, Customer must establish a sparing
depot. Depot inventory must be maintained at the Corvis recommended minimum
sparing levels.

     Should Corvis determine that the failure is due to faulty hardware, Corvis
will send replacement component(s) to the designated depot location. Included
with such component(s) will be packing material, a prepaid shipping enclosure
and all necessary documentation to facilitate the return of the defective
component to Corvis by Customer or Customer personnel. Corvis will assume all
costs associated with the shipment of the replacement component(s) and the
return of the failed component(s). Customer shall return the malfunctioning
hardware product to Corvis within 10 days of the receipt of the replacement
product.

     Should Corvis determine that the cards are fully functional and are "no
fault found" in accordance with Corvis fault diagnostic and testing procedures,
Corvis will invoice customer for the replacement component, associated testing
and all shipping and shipping related costs.

     Advance replacement requests received at the Corvis TAC by 3:00 p.m.
Eastern Time will be processed on the same business day. Corvis will make all
reasonable commercial efforts to effect delivery of the replacement hardware
component into the designated sparing depot(s) by the next business day for
those locations where international customs need not be cleared. Requests made
after
<PAGE>

3:00 p.m. Eastern Time or on weekends or Corvis holidays will be processed on
the next business day for delivery on the following business day.

     It is Corvis' intention to use Customer's preferred carrier for shipments
to Customer contingent upon availability, quality, pricing, and terms and
conditions of service that such carrier makes available to Corvis. In all cases,
Corvis will use an internationally recognized carrier. Should Corvis elect not
to use Customer's preferred carrier, Corvis will notify Customer and will, at
Customer's option, assume responsibility for package tracking.
<PAGE>

                                 ATTACHMENT 28

                            PRODUCT SPECIFICATIONS
                            ----------------------

     Corvis System Specifications

The Corvis system comprises a number of network elements, which can be
configured to form point to point and mesh network connections. The maximum span
distance that any of the [*] channels can traverse before electronic
regeneration depends on the individual fiber types and span losses between
optical amplifier sites. The Corvis Wave Planner automatically determines
appropriate locations for each of the network elements and regeneration sites
based on the actual span losses and fiber types in the system.

Tables 2 and 3 specify the system performance under the following assumptions:
     1.   all span losses in the system are identical;
     2.   absolute value of fiber dispersion is greater than [*] for all
          channels;
     3.   all spans consist of Corning-LS or Lucent TrueWave-Classic, Plus, or
          RS fiber and have an average [*];
     4.   the maximum transmission distance is 3200 km; and,
     5.   the system is operated using the parameters listed in Table 1.

                          Table 1: System Parameters
-------------------------------------------------------------------------------
                   Parameter                          Value      Units
-------------------------------------------------------------------------------
Amplifier Input Connector Loss                       0.2           dB
-------------------------------------------------------------------------------
Amplifier Output Connector Loss                      0.2           dB
-------------------------------------------------------------------------------
Operating Range                                   1530-1564        nm
-------------------------------------------------------------------------------
Maximum System Gain Flatness Variation               [*]           dB
-------------------------------------------------------------------------------
Maximum Amplifier Gain [*]                           [*]           dB
-------------------------------------------------------------------------------
[*] (See note 1)                                     [*]           dB
-------------------------------------------------------------------------------
Nominal Fiber Launch Power / Channel                 [*]           dBm
-------------------------------------------------------------------------------
Equivalent OSNR at Fiber Launch                      [*]           dB.nm
-------------------------------------------------------------------------------
Maximum accumulated dispersion (See note 2)          [*]           ps/nm
-------------------------------------------------------------------------------
Receiver Sensitivity [*]                             [*]           dB.nm
-------------------------------------------------------------------------------
Minimum EOL System Margin (See Note 3)               [*]           dB
-------------------------------------------------------------------------------
Additional EOL System Margin Connector Penalty       [*]           dB
-------------------------------------------------------------------------------

Note 1:   Total loss = span loss + amplifier module loss.
Note 2:   [*]
Note 3:   The Minimum EOL margin includes the following:
          [*]dB [*]
          [*]dB [*] variation across all [*] Channels
          [*]dB Unallocated margin
<PAGE>

                  Table 2: System Performance using [*]/4-6/
          ---------------------------------------------------------
                                [*]              [*]        [*]
                   [*]       Number of       Number of
               EOL Span      Spans           Spans
               Loss (dB)       w/[*]           w/[*]
          ---------------------------------------------------------
                 [*]             [*]              [*]        [*]
          ---------------------------------------------------------
                 [*]             [*]              [*]        [*]
          ---------------------------------------------------------
                 [*]             [*]              [*]        [*]
          ---------------------------------------------------------

                   Table 3: System Performance using [*]/4-6/
          ---------------------------------------------------------
                                [*]              [*]        [*]
                   [*]       Number of       Number of
               EOL Span      Spans           Spans
               Loss (dB)       w/[*]           w/[*]
          ---------------------------------------------------------
                 [*]             [*]              [*]        [*]
          ---------------------------------------------------------
                 [*]             [*]              [*]        [*]
          ---------------------------------------------------------
                 [*]             [*]              [*]        [*]
          ---------------------------------------------------------
                 [*]             [*]              [*]        [*]
          ---------------------------------------------------------
                 [*]             [*]              [*]        [*]
          ---------------------------------------------------------
                 [*]             [*]              [*]        [*]
          ---------------------------------------------------------
                 [*]             [*]              [*]        [*]
          ---------------------------------------------------------
                 [*]             [*]              [*]        [*]
          ---------------------------------------------------------
                 [*]             [*]              [*]        [*]
          ---------------------------------------------------------
                 [*]             [*]              [*]        [*]
          ---------------------------------------------------------

Note 4:   [*]

Note 5:   [*]

Note 6:   Based on an Amplifier Module Loss for [*] of [*] dB and a [*] dB
          respectively.

The transmission distance can be calculated based on the average loss per km
(dB/km) for a span using the equation:

[*] transmission distance (km) = Minimum (3200,([*]EOL Span)x(#of
spans)/(Average Loss/km).

A sample calculation is shown below for a system with an average loss per km of
0.245 dB/km and a 17 dB EOL span loss using [*].

<TABLE>
<CAPTION>
----------------------------------------------------------------------------------------------------------------------------
Amp       System w/[*]                                                System w/[*]
----------------------------------------------------------------------------------------------------------------------------
<S>       <C>                                                         <C>
[*]       Max Distance = (17 dB/span)*([*] spans)/(0.0245 dB/km)      Max Distance = (17 dB/span)*([*] spans)/(0.0245 dB/km)
                       = Min(3200, [*] km) = 3200 km                  = Min(3200, [*] km) = 3200 km
----------------------------------------------------------------------------------------------------------------------------
[*]       Max Distance = (17 dB/span)*([*] spans)/(0.0245 dB/km)     Max Distance = (17 dB/span)*([*] spans)/(0.0245 dB/km)
                       = Min(3200, [*] km) = 3200 km                  = Min(3200, [*] km) = [*] km
----------------------------------------------------------------------------------------------------------------------------
</TABLE>
<PAGE>

     Corvis Optical Amplifier

The Corvis Optical Amplifier provides optical amplification of up to 160 OC [*]
optical signal channels that allows for transmission distances up to 3,200 km
without electrical regeneration using Corvis transmitters and receivers. Two
Corvis Optical Amplifiers are provided on a single [*] amplifier shelf for use
in two fiber systems. A single rack can house up to [*] amplifier shelves. The
Corvis Optical Amplifier can be provided in [*] to amplify spans with losses up
to [*]. A [*] can be added to either [*] as required to [*] for [*] and the [*]
loss is added to the span loss. The Corvis Optical Amplifier is equipped to
transmit and receive [*] carrying [*] channels, Corvis system supervisory
information, and [*] order wires. A Craft Interface and Environmental Control
Unit (ECU) are provided for local control of the amplifier.

                                 [*] Amplifier
--------------------------------------------------------------------------------
Parameter             Nominal Value  Units                Notes
--------------------------------------------------------------------------------
Max. Amplifier Gain         [*]       dB      Based on LS, TW-C, TW-P and TW-RS
                                              fiber spans having an average [*]
--------------------------------------------------------------------------------
Operating Range          1530-1564    nm
--------------------------------------------------------------------------------
Gain Flatness over
Operating Range             [*]       dB

--------------------------------------------------------------------------------

                                 [*] Amplifier
--------------------------------------------------------------------------------
Parameter             Nominal Value  Units                Notes
--------------------------------------------------------------------------------
Max. Amplifier Gain         [*]       dB      Based on LS, TW-C, TW-P and TW-
     [*]                    [*]       dB      RS fiber spans having an average
                                                                   [*]
--------------------------------------------------------------------------------
Operating Range          1530-1564    nm
--------------------------------------------------------------------------------
Gain Flatness over
Operating Range             [*]       dB
--------------------------------------------------------------------------------

                 ---------------------------------------------------
                    Size and Weight          Specification
                 ---------------------------------------------------
                    Power                    -48 volts @ [*] Amps
                 ---------------------------------------------------
                    Heat Dissipation         [*] Watts /Shelf
                 ---------------------------------------------------
                    Size                     84"x24"x24"
                 ---------------------------------------------------
                    Weight (OA3200L[*])      [*]
                 ---------------------------------------------------
<PAGE>

     Corvis Optical Network Gateway

The Corvis Optical Network Gateway (ONG) can be configured to transmit and
receive up to 160 OC [*] optical signal channels for up to 3,200 km without
electrical regeneration when used with Corvis Optical Amplifiers. [*] racks are
required to house equipment for 160 transmit channels and 160 receive channels
according to the channel plan provided below. [*] ONG rack includes [*] transmit
channels and [*] receive channels along with multiplexing, demultiplexing, and
monitoring equipment. In addition, [*] rack is equipped to transmit and receive
[*] and provides a Craft Interface for local access to the ONG.

     ---------------------------------------------------------------------------
           Parameter                    Min        Typ   Max   Units  Comments
     ---------------------------------------------------------------------------
      Number of channels                                 160
     ---------------------------------------------------------------------------
      [*]                               [*]        [*]   [*]
     ---------------------------------------------------------------------------
      Data Rate per channel                        [*]           Gb/s     [*]
     ---------------------------------------------------------------------------
     ---------------------------------------------------------------------------
      Tx Output Power per channel                  [*]           dBm
     ---------------------------------------------------------------------------
      Fiber Launch power per channel               [*]           dBm
     ---------------------------------------------------------------------------
     ---------------------------------------------------------------------------
      Rx Input Power per channel                   [*]           dBm
     ---------------------------------------------------------------------------
      Receiver Sensitivity at [*]       [*]        [*]           dB.nm
     ---------------------------------------------------------------------------

     ---------------------------------------------------------------------------
                 Parameter                            Value    Units   Comments
     ---------------------------------------------------------------------------
      Number of Racks - up to [*] Tx/Rx Channels       [*]
     ---------------------------------------------------------------------------
      Number of Racks - up to [*] Tx/Rx Channels       [*]
     ---------------------------------------------------------------------------
      Number of Racks - up to [*] Tx/Rx Channels       [*]
     ---------------------------------------------------------------------------
      Number of Racks - up to [*] Tx/Rx Channels       [*]
     ---------------------------------------------------------------------------
      Number of Racks - up to [*] Tx/Rx Channels       [*]
     ---------------------------------------------------------------------------
      Number of Racks - up to [*] Tx/Rx Channels       [*]
     ---------------------------------------------------------------------------
      Voltage requirements                             -48       V  Standard
                                                                    Voltage
     ---------------------------------------------------------------------------
      Power requirements/Rack                          [*]       W
     ---------------------------------------------------------------------------
      Dimensions per Rack (WxDxH)                   19x24x84   Inches
     ---------------------------------------------------------------------------
<PAGE>

     CORVIS Optical Add/Drop Multiplexer [*] (OADM [*])

The OADM [*] allows up to 160 channels of Add Drop access, [*], and [*] of
channels. The OADM [*] is partitioned into [*] section that provides for [*] the
add/drop function and [*], which can be upgraded to provide add/drop
functionality by addition of ONGs. The rack configuration and space requirements
depend on the number of channels accessed in each direction.

     ---------------------------------------------------------------------------
              Parameter                      Min   Typ   Max   Units  Comments
     ---------------------------------------------------------------------------
      Number of channels                     [*]         160
     ---------------------------------------------------------------------------
      Wavelength range                       1530        1564   nm
     ---------------------------------------------------------------------------
      [*]                                    [*]         [*]
     ---------------------------------------------------------------------------
      [*]                                    [*]         [*]
     ---------------------------------------------------------------------------
      Output optical power per channel       [*]   [*]   [*]    dBm
     ---------------------------------------------------------------------------
      Output optical power (160 channels)    [*]   [*]   [*]    dBm
     ---------------------------------------------------------------------------
      [*]                                    [*]         [*]    [*]
     ---------------------------------------------------------------------------
      [*]                                    [*]                [*]
     ---------------------------------------------------------------------------

     ---------------------------------------------------------------------------
          Parameter                   Value    Units              Comments
     ---------------------------------------------------------------------------
      Number of Racks: [*]             [*]                          [*]
     ---------------------------------------------------------------------------
      Number of Racks: OADM [*]        [*]              Up to [*] channels Add/
                                                         Drop in each direction
     ---------------------------------------------------------------------------
      Number of Racks: OADM [*]        [*]              Up to [*] channels Add/
                                                         Drop in each direction
     ---------------------------------------------------------------------------

      Number of Racks: OADM [*]        [*]              Up to [*] channels Add/
                                                         Drop in each direction
     ---------------------------------------------------------------------------
       Voltage requirements            -48       V      Standard Voltage
     ---------------------------------------------------------------------------
      Power requirements/Rack          [*]       W
     ---------------------------------------------------------------------------
      Dimensions per Rack (WxDxH)    19x24x84  Inches
     ---------------------------------------------------------------------------
<PAGE>

Channel Plan:

The Corvis system transmits and receives 160 channels [*] as shown in the table
below.  [*] resulting in total system capacity of 400 Gb/s.  [*] are allocated
in the channel plan [*].

-----------------------------------------
 Wavelength    Frequency      Wavelength
 Number           (THz)          (nm)
-----------------------------------------
    [*]              [*]            [*]

<PAGE>

                            [BROADWING LETTERHEAD]

                                                                   April 7, 2000

Kim Larsen
General Counsel
Corvis Corporation
7015 Albert Einstein Drive
PO Box 9400
Columbia, Maryland 21046-9400

Dear Kim,

     As we discussed, please note the following items which should revised in
the Procurement Agreement between Broadwing Communications Services Inc. and
Corvis Corporation, dated March 17, 2000.

     Article 4 "Volume Deployment; Quantities and Delivery Schedules" shall be
amended to read as follows:

     4.1  Initial Deployment. Upon successful completion of the Transport Field
     Trial, Customer will purchase from Corvis and deploy the Corvis Transport
     Equipment and Software in quantities and in configurations priced at U.S.
     $200,000,000.00 (the "Minimum Deployment Commitment"), U.S. $100,000,000.00
     of which (the "First Year Deployment Commitment") must be ordered within 12
     months after the successful completion of the Field Trial with delivery no
     later than 60 days after such 12 month period, in each case based on the
     prices and license fees set forth in Attachment 6. The Minimum Deployment
     Commitment and the First Year Deployment Commitment shall be adjusted for
     late delivery by Corvis as provided in Section 4.2. Customer will be
     offered most favored customer pricing in accordance with the terms and
     conditions of Attachment 6.

     4.2  Initial Deployment Schedule; Late Deliveries. Within 30 days after
     successful completion of the Transport Field Trial, Customer and Corvis
     shall agree upon a non-binding estimated deployment schedule (the
     "Estimated Deployment Schedule") for the Minimum Deployment Commitment. If
     Customer submits Purchase Orders for Corvis
<PAGE>

     Transport Equipment and Software in accordance with applicable lead times
     and the amount ordered and previously shipped does not exceed the Estimated
     Deployment Schedule, the Minimum Deployment Commitment and the First Year
     Deployment Commitment shall each be reduced by the aggregate purchase price
     of the Corvis Transport Equipment and Software Corvis fails to deliver
     within 60 days after the agreed delivery date.

     4.3  Non-binding Forecasts. Quantity Forecast. By the fifth business day of
     each month (the Month hereafter being "M"), Customer will provide to Corvis
     a non-binding ten-month rolling forecast (the "Rolling Forecast") of
     deliveries for the ten-month period commencing at the beginning of the
     third month after the month in which the forecast is made. The Rolling
     Forecast (M+3 through M+12) will show the quantity of each Product by
     product code which Customer anticipates it will need to be delivered during
     the specified month.

     4.4  During the Term of this Agreement, Customer will issue Purchase Orders
     specifying the Products ordered, the quantities necessary, the delivery
     site or sites (hereinafter the "Specified Site[s]") for the Products and
     its proposed delivery schedule.

     4.5  All deliveries of Products will be made F.O.B. destination. Customer
     agrees to pay freight and insurance charges. The preceding provisions of
     this clause are valid for deliveries in the United States, its possessions
     and territories only. All deliveries outside the aforementioned areas will
     be mutually agreed upon on a case by case basis.

     4.6  Customer will have the right to alter the destination site at least
     ten (10) days prior to Corvis' scheduled shipment date for Products,
     without cost or expense to Customer, by timely transmitting Notice to
     Corvis of the new Specified Site(s).

     4.7  Corvis will execute and deliver to Custumer an order acknowledgment
     within seven days after Corvis' receipt of each Purchase Order or, if
     Corvis cannot meet the proposed delivery times, the parties shall mutually
     agree to appropriate delivery times. If Corvis and Customer cannot agree
     upon delivery times, Corvis shall have the right to reject a Purchase
     Order. Product order lead times shall be 12 weeks unless otherwise
     specified by Corvis.

     4.8  Customer will purchase on-site installation spares, parts and
     components of the Equipment ("Spares Kits" or "Kits") reasonably designated
     by Corvis and agreed upon by Corvis and Customer from time to time as the
     quantity necessary to enable Corvis to provide the warranty and support
     services required by this Agreement. The quantity and
<PAGE>

     locations of the Kits may change with installation requirements and changes
     in the topology of Customer's network.

      4.9  [*]

     4.10  [*]

             Article 28 "Definitions" shall be amended as follows:

     "Committed Amounts" shall be deleted.
     "Final Deployment Date" shall be deleted.
     "Initial Deployment Shortfall" shall be deleted.
     "Specified Site" shall reference the definition contained in Section 4.4.

     All other definitions shall remain in full force and effect.

     Please execute your concurrence by counter-execution below and return at
your earliest convenience.

                                    Sincerely,

                                    /s/ Angela L. Jones
                                    Angela L. Jones

_________________________

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