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                                                                   Exhibit 10.10


                                 AMENDMENT NO. 6

THIS AMENDMENT NO. 6 ("Amendment") is made and entered into effective this 25th
day of September, 2001, by and between WILLIAMS COMMUNICATIONS, LLC ("Customer")
and CORVIS CORPORATION ("Corvis").

WHEREAS, Customer and Corvis are parties to that certain Procurement Agreement
dated April 6, 2000, which has been subsequently amended from time to time (the
"Agreement"); and

WHEREAS, Customer and Corvis desire to further amend the Agreement; and

NOW, THEREFORE in consideration of the foregoing premises and mutual promises
and covenants of the parties hereto, the receipt and sufficiency of which is
hereby acknowledged, Customer and Corvis agree to amend the Agreement as
follows:

1.   The following language shall be added to the end of Attachment 3.2
(Revised), provided for by Amendment No. 4, dated April 23, 2001, to the
Procurement Agreement:

          In connection solely with the Corvis Products to be sold to Customer
     from time to time under the Agreement, which are also financed by Corvis or
     with respect to which Corvis had provided deferred payment terms to
     Customer (the "Financed Products"), and in consideration for the extension
     of payment terms and other valuable consideration, Corvis reserves, and
     Customer hereby grants to Corvis, a purchase money security interest in any
     Financed Products sold to Customer by Corvis under or pursuant to this
     Agreement until any and all payments, charges and other amounts due or to
     become due to Corvis solely for the purchase of such Financed Products,
     including without limitation taxes, and shipping and installation charges
     for the Financed Products, are paid in full.

          Corvis shall have the right and is hereby authorized, at any time and
     without notice to Customer, to file in any state or local jurisdiction, and
     Customer hereby agrees to execute upon request from Corvis, such financing
     statements (e.g., UCC-1 financing statements) or other writings as Corvis
     reasonably from time to time deems necessary to perfect and continue the
     perfection of the purchase money security interest granted hereunder.
     Notwithstanding the foregoing, Customer hereby appoints Corvis as its
     attorney-in-fact for the sole purpose of the above said filing and, to the
     extent necessary, to execute any such financing statements and such other
     writings prepared by Corvis or its designee solely for purposes of
     perfecting or maintaining the perfection of Corvis' purchase money security
     interest granted hereunder. Customer also agrees that this Amendment, or a
     carbon, xerographic or other copy hereof may be filed by Corvis in any
     state or local jurisdiction as a financing statement (or as other evidence
     of Corvis' purchase money security interest). Customer shall not sell or
     lease the Financed Products or allow any liens or encumbrances to attach to
     the

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     Financed Products without written permission of Corvis prior to payment in
     full for the Financed Products.

          In addition to any other remedy available to Corvis as provided
     herein, by common law or by statute, Corvis may, if applicable, exercise
     its rights pursuant to UCC 2-702 or such other applicable provision as may
     exist from state to state.

2.   Except as specifically amended herein, all other provisions of the
Agreement shall remain unchanged and in full force and effect.

IN WITNESS WHEREOF, the parties have executed this Amendment as of the day and
year last set forth below.


WILLIAMS COMMUNICATIONS, LLC                  CORVIS CORPORATION


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         (TITLE)                                  (TITLE)

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         (DATE)                                   (DATE)