<PAGE>

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


                                                                   Exhibit 10.13
                                                                   -------------


                   Fiber Optic Network Leased Fiber Agreement
                                 Product Order

This Product Order ("Product Order") together with the General Terms and
Conditions constitute the Fiber Optic Private Network Agreement ("Agreement")
which is effective as of October 8, 1999 by and between Metromedia Fiber Network
Services, Inc. ("MFN"), One North Lexington Ave., Fourth Floor, White Plains,
New York 10601, and StorageNetworks, Inc. ("Carrier"), 100 Fifth Avenue,
Waltham, Massachusetts 02451.  Definitions of terms used in this Agreement
appear in this Product Order and in the General Terms and Conditions.

Carrier hereby orders and MFN hereby agrees to provide Leased Fiber as follows:

     1.   Lease Term: 240 Months

     2.   Number of Leased Fibers: To Be Determined in each Supplement

     3.   Number of Leased Fiber Miles: An aggregate of [**] to be leased
          pursuant to supplements ("Supplements" and each a "Supplement") to
          this Product Order to be executed between the parties. The form of
          Supplement is attached hereto as Annex I. In no event shall MFN add to
          any Supplement any materially terms or conditions different from or in
          addition to the terms and conditions of this Agreement without the
          prior consent of Carrier.

     4.   Carrier locations ("Location(s)"): To be specified in Supplements to
          this Product Order.

     5.   Specifications pertinent to the Leased Fiber: To be provided as an
          Exhibit to the Supplement. Minimum Specifications of the Leased Fiber
          are set forth in Annex II hereto.

     6.   Installation Charge and Monthly Lease Payments:

          6.1  One Time Installation Charge: If any, to be specified in each
               Supplement. Any lateral connections from the MFN Network to such
               Locations are not included in the Monthly Lease Payment. Such
               lateral connections may be built by MFN at Carrier's request and
               at Carrier's cost, to be negotiated in good faith by the parties
               and included in any Supplement. The One Time Installation Charge
               for a Location shall in no event exceed MFN's actual cost plus
               [**] plus Applicable Taxes, whether such cost is incurred before
               or after the date of the applicable Supplement.


          6.2  Monthly Lease Payments: [**]per Leased Fiber Mile, subject to
               tolling and discounting as hereinafter provided.

          Applicable Taxes (as defined in the Agreement) on any Installation
          Charge incurred pursuant to a Supplement and all Lease Payments are to
          be paid by Carrier as and when due. In no event shall Applicable Taxes
          include any franchise or other right of way fees or similar charges or
          impositions assessed upon MFN. Carrier shall have the right to protest
          any new or additional taxes imposed on the Leased Fiber during the
          Lease Term.

     7.   Estimated Installation Completion Dates: To be specified in
          Supplements

     8.   Early Termination Charge:
<PAGE>

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



     In the event of termination of this Agreement or any Supplement to this
     Product Order pursuant to Section 11.2 of the General Terms and Conditions
     of this Agreement, Carrier will pay to MFN an Early Termination Charge
     (plus Applicable Taxes) for the affected Leased Fiber determined as
     follows:

     Termination during the first year of the Lease Term - [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     first year, plus [**]of all unpaid Leased Fiber Monthly Lease Payments for
     the affected Leased Fiber for the second year, plus [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     third year, plus [**]of all unpaid Leased Fiber Monthly Lease Payments for
     the affected Leased Fiber for the fourth year, plus [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     fifth year, plus [**] of all unpaid Leased Fiber Monthly Lease Payments for
     the affected Leased Fiber for the sixth through twentieth years.

     Termination during the second year of the Lease Term - [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     second year, plus [**] of all unpaid Leased Fiber Monthly Lease Payments
     for the affected Leased Fiber for the third year, plus [**]of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     fourth year, plus [**] of all unpaid Leased Fiber Monthly Lease Payments
     for the affected Leased Fiber for the fifth year, plus [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     sixth through twentieth years.

     Termination during the third year of the Lease Term- [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     third year, plus [**] of all unpaid Leased Fiber Monthly Lease Payments for
     the affected Leased Fiber for the fourth year, plus [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     fifth year, plus [**] of all unpaid Leased Fiber Monthly Lease Payments for
     the affected Leased Fiber for the sixth through twentieth years.

     Termination during the fourth year of the Lease Term- [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     fourth year, plus [**] of all unpaid Leased Fiber Monthly Lease Payments
     for the affected Leased Fiber for the fifth year, plus [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     sixth through twentieth years.

     Termination during the fifth year of the Lease Term- [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     fifth year, plus [**] of all unpaid Leased Fiber Monthly Lease Payments for
     the affected Leased Fiber for the sixth through twentieth years.

     Termination during the sixth through twentieth year of the Lease Term -
     [**] of all unpaid Leased Fiber Monthly Lease Payments for the affected
     Leased Fiber for the balance of the Lease Term.

     In the event that this Agreement is terminated pursuant to Section 11.2 of
     the General Terms and Conditions, and if Carrier has not yet leased [**]
     fiber miles from MFN hereunder as of the date of any termination, then such
     termination shall be calculated as if Carrier has leased [**] fiber miles
     at the per fiber mile per month price set forth in Section 9.1(b) of this
     Product Order.

9.   Fiber, Locations and Requirements
<PAGE>

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


9.1  Carrier acknowledges and agrees that within [**] of the effective date of
     this Agreement, Carrier will lease from MFN pursuant to Supplements for a
     term of two hundred forty (240) months Leased Fiber subject to the terms
     and conditions of this Agreement totaling at least [**] fiber miles in at
     least [**] metropolitan areas where MFN has or reasonably expects to have
     within such [**] period an installed fiber optic network.

     (a)  For the purposes of this Agreement, fiber miles will be calculated by
          multiplying the physical mileage of Carrier's Leased Fiber route(s) by
          the quantity of Leased Fiber along the same route(s).

     (b)  The monthly lease payment for the initial [**] Leased Fiber fiber
          miles that MFN leases to Carrier within [**] of the effective date of
          this Agreement shall be [**] per fiber mile per month for the duration
          of the Lease Term.

     (c)  Carrier further acknowledges and agrees that it shall be liable to MFN
          for any difference that may exist between the monthly lease payment
          for [**]fiber miles and Carrier's actual total Leased Fiber miles
          pursuant to Supplements [**] after the effective date of this
          Agreement (the "Contract Balance") for the period beginning at the end
          of such [**] until such time as Carrier has leased [**] fiber miles
          pursuant to Supplements. If such difference exists, MFN will provide
          Carrier written notice of the deficiency [**] after the effective date
          of this Agreement and Carrier will then have thirty (30) days to order
          additional fiber subject to the terms and conditions of this Agreement
          necessary to achieve Supplements for [**] Leased Fiber fiber miles. If
          after [**] from the effective date of this Agreement Carrier still has
          not leased from MFN Leased Fiber totaling [**] fiber miles pursuant to
          Supplements, MFN will invoice and Carrier will pay a monthly lease
          payment each month equal to the Contract Balance (as the Contract
          Balance may be reduced in accordance with the this paragraph)
          multiplied by [**] per fiber mile per month commencing at the
          beginning of the [**] after the effective date of this Agreement until
          such time as Carrier has leased an aggregate of [**] fiber miles
          pursuant to Supplements. Any such amount will be subject to an early
          termination charge as set forth in Section 8. As and when Carrier has
          leased Leased Fiber miles pursuant to Supplements, the Contract
          Balance shall be reduced by the amount of the fiber miles subject to
          such Supplements. Notwithstanding anything to the contrary contained
          in this provision, Carrier will have no liability under this provision
          in the event that any failure of Carrier to lease [**] fiber miles is
          due to MFN's inability to deliver fiber in accordance with any
          Supplements, including, without limitation, any failure of MFN to
          timely deliver Leased Fiber, any failure of any Leased Fiber to meet
          the Specifications, MFN's failure to build to announced build plans,
          any breach of MFN of the representations contained in Section 9.3,
          and/or any other failure or inability of MFN to timely deliver Leased
          Fiber in accordance with the terms of the Agreement.

     (d)  In no event shall Carrier be obligated to lease Leased Fiber from MFN
          in excess of [**] fiber miles.

9.2  Carrier will, from time to time, request fiber pursuant to the terms and
     provisions hereof, by providing MFN with one or more written notices. Each
     such notice shall indicate the number of fibers, the MFN metropolitan
     market and Carrier's proposed Locations. Within thirty (30) days after
     receipt of such notice, MFN will respond to Carrier with a Supplement
     confirming the availability, the monthly lease payment for the Leased Fiber
     subject to the Supplement, the one time installation charge, if any,
<PAGE>

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



     and the estimated installation completion date for the requested fiber.
     Carrier may request fiber in any metropolitan area that MFN has or
     reasonably expects to have within [**] of the effective date of this
     Agreement an installed fiber optic network. If Carrier accepts such
     Supplement, Carrier will execute and return to MFN each such Supplement
     within ten (10) days of receipt thereof.

     For any Supplement executed by the parties within [**] of the date hereof,
     MFN shall discount the [**] lease payments for Leased Fiber pursuant to
     such Supplements by[**].

9.3  Attached hereto as Annex III is a map of every metropolitan area in which
     MFN currently has an existing fiber optic network. Attached hereto as Annex
     IV is a complete listing of every additional metropolitan area in which MFN
     will have a fiber optic network during the [**] period following the
     effective date of this Agreement. For [**] after the effective date of this
     Agreement, MFN commits to provide to Carrier upon an executed Supplement up
     to [**] fiber strands along any MFN network ring identified in Annex III
     and, after the date MFN has identified such network to be available, Annex
     IV. Subject to fiber availability, MFN will use commercially reasonable
     efforts to honor Carrier's requests for fiber in excess of [**] strands
     along such network rings. In no event shall MFN be required to lease to
     Carrier more than [**] fiber strands in any single MFN network ring.

9.4  If, within [**] of the effective date of this Agreement, Carrier has leased
     at least [**] fiber miles pursuant to the terms and conditions of this
     Agreement and provided Carrier is not in any material breach of this
     Agreement and, this Agreement is in full force and effect, the price for
     each additional fiber mile that MFN leases to Carrier on MFN Networks
     pursuant to Supplements entered into during the [**] period following the
     effective date of this Agreement shall be the lower of the prices set forth
     below or the then current MFN market rate for such additional leased fiber:



          Incremental
Fiber    $/Fiber Mile/
 Mile       Month
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
<PAGE>

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




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

-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------
[**]         [**]
-----------------------


9.5    Provided Carrier is not in any material breach of this Agreement and this
Agreement is in full force and effect, Carrier may request additional Locations
be added to any then existing Supplement by providing MFN one or more written
requests.  Such orders shall indicate the number of fibers, requested term, and
any relevant information necessary to identify the requested Locations
including, but not limited to, the address, floor, suite, and room number of the
requested Location.  The minimum allowable term shall be one (1) year and the
maximum allowable term shall be coterminous with the Agreement.  Within thirty
(30) days after receipt of such orders, MFN will respond to Carrier with a
revised Supplement confirming the availability, the monthly lease payment, the
one time installation charge, if any, and the estimated installation completion
date for the requested additional Locations.  If Carrier accepts such
Supplement, Carrier will execute and return to MFN each such Supplement within
ten (10) days of receipt thereof.

9.6 If, within [**] months of the effective date of this Agreement, Carrier has
leased at least [**] fiber miles pursuant to the terms and conditions of this
Agreement and provided Carrier is not in any material breach of this Agreement
and, this Agreement is in full force and effect, then MFN will extend the
pricing set forth in Section 9.4 above for additional fiber leased by Carrier
pursuant to Supplements entered into during the period ending [**] months after
the effective date of this Agreement.

9.7  The Lease Term for all of the Supplements to this Product Order shall be
coterminous with the Lease Term for the Supplement with the earliest Service
Date.

10.  MFN address (and contact person) is as follows:

     Metromedia Fiber Network Services, Inc.
     One North Lexington Ave., Fourth Floor
     White Plains, NY  10601
     Attn.:  Vice President - Marketing

     For purposes of declaring a default or termination, a copy of the notice
     must be sent to:

     Vice President - Legal Affairs
     Metromedia Fiber Network Services, Inc.
     One North Lexington Ave., Fourth Floor
     White Plains, NY  10601

     Carrier address (and contact person) is as follows:

     StorageNetworks, Inc.
     100 Fifth Avenue
     Waltham, Massachusetts 02451
     Attn:  Chief Financial Officer
<PAGE>

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



     For purposes of declaring a default or termination, a copy of the notice
     must be sent to:

     General Counsel
     StorageNetworks, Inc.
     100 Fifth Avenue
     Waltham, Massachusetts 02451



11.1 At any time after the fifth anniversary of the Service Date for a Leased
     Fiber, Carrier shall have the right to exchange Leased Fiber for alternate
     fiber in another MFN Network. If Carrier desires to make such an exchange,
     Carrier shall give MFN a written request setting forth the number of
     strands of Leased Fiber, the Route and the Locations which Carrier desires
     to exchange, as well as the proposed number of alternate Leased Fibers, the
     MFN metropolitan market in which Carrier desires the alternate Leased Fiber
     and the proposed Locations. Within thirty (30) days after receipt of such
     notice, MFN will respond to Carrier with a Supplement confirming the
     availability of the fiber, the monthly lease payment for the Leased Fiber,
     the one time installation charge, if any (which charge shall include,
     without limitation, MFN's cost to take the old Leased Fiber out of service
     plus [**], and the estimated installation completion date for the requested
     fiber. The Lease Term for such new Leased Fiber shall equal the balance of
     the Lease Term for the Leased Fiber that was exchanged therefor. If Carrier
     accepts the Supplement, Carrier will execute and return to MFN each such
     Supplement.

11.2 Notwithstanding anything in Section 11.1 above to the contrary, (i) in no
     event shall Carrier have the right to effect an exchange pursuant to
     Section 11.1 above that would result in the maximum number of fiber strands
     in any single MFN Network ring to exceed the limitations set forth in
     Section 9.3 above, (ii) Carrier shall incur no Early Termination Charges in
     connection with such exchange effected pursuant to Section 11.1 above,
     (iii) in any calendar year during the Lease Term of the Agreement, Carrier
     shall not be permitted to request more than twelve (12) such exchanges of
     Leased Fiber (pro rated for partial calendar years), nor may the quantity
     of Leased Fiber fiber miles exchanged pursuant to such exchanges effected
     pursuant to Section 11.1 above exceed more than [**] of the total Leased
     Fiber Miles for which the Service Date has commenced (the "In-Service
     Leased Fiber") during any calendar year (pro rated for partial calendar
     years); and (iv) during the Lease Term of the Agreement, no more than [**]
     of the In-Service Leased Fiber may be exchanged nor may Carrier request
     more than sixty (60) such exchanges pursuant to Section 11.1 above.



Metromedia Fiber Network Services, Inc.  StorageNetworks, Inc.


By: ____________________              By: _______________________
     Nicholas M. Tanzi                 Name:_____________________
     Senior Vice President               Title:__________________
<PAGE>

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



                     Fiber Optic Private Network Agreement
                     -------------------------------------

                          General Terms and Conditions


1.   TERM AND LEASE
     --------------

1.1  MFN hereby leases to Carrier, pursuant to Supplements to be executed by the
     parties, optical fiber ("Leased Fiber") on MFN's fiber optic cable network
     ("Network") and/or constructed and installed specifically for Carrier and
     the equipment and interfaces described in the Supplements to the Product
     Order ("Equipment"), as provided in the Product Order and the Supplements
     thereto. The Leased Fiber and Equipment leased by Carrier will be referred
     to as the "Product". The lease term ("Lease Term") and other specific terms
     pertaining to the Product are set forth in the Supplements. The term
     "Party" will refer, individually, to either MFN or Carrier and the term
     "Parties" will refer to both of them. The term "Agreement" will mean and
     include the Product Order, all Supplements and all Exhibits thereto and
     these General Terms and Conditions.

1.2  MFN will use commercially reasonable efforts to complete installation of
     and provide Carrier with access to the Product by the Estimated
     Installation Completion Date specified in the Supplements at the Locations
     specified in the Supplement ("Turnover Date") and to conduct the testing
     (and provide such test results) detailed in Annex II to the Product Order.
     Carrier will be provided at least ten (10) days prior written notice of the
     tests described in Annexx II to the Product Order and will be permitted to
     observe, or have its designee observe, such tests. For a period of time not
     to exceed ten (10) business days after the Turnover Date (the "Acceptance
     Test Period"), Carrier will conduct such testing as it reasonably deems
     necessary to ensure that the Product conforms in all material respects to
     the material technical specifications set forth in the applicable Exhibit A
     to the Supplement ("Specifications"). Carrier will use commercially
     reasonable efforts to complete such acceptance testing and notify MFN in
     writing within five (5) business days after the Turnover Date, but in any
     event within the Acceptance Test Period, of acceptance or of any
     "Deficiencies" (as defined herein) in such Product. Deficiencies exist if
     the Product does not conform in all material respects to the relevant
     Specifications. Upon receipt of such notification from Carrier, MFN will
     promptly undertake correction of such Deficiencies and restore access to
     and use of such Product to Carrier. The "Service Date," whereupon the Lease
     Term commences for such Product, will be the earlier of (i) the date
     Carrier accepts such Product following completion of testing and acceptance
     of such Product by Carrier, (ii) expiration of the AcceptanceTest Period
     or, (iii) if Carrier has identified Deficiencies, then the first date upon
     which such Product conforms in all material respects with the relevant
     Specifications.

1.3  Carrier will obtain all necessary approvals for access into the Location
     buildings and for the use of any required building riser conduit or other
     required building facilities at all Locations to the extent that MFN has
     not actually obtained such approvals previously. Unless otherwise provided
     for in the Product Order, if there is no existing and available riser
     conduit or other required facilities within such buildings then Carrier
     shall arrange to have such riser constructed at its own cost or (ii) have
     MFN perform all construction and installation of such riser conduit at
     Carrier's expense, which shall be MFN's cost to contract and install such
     riser conduit plus [**] plus Applicable Taxes. To the extent that Carrier
     is required to obtain all necessary approvals as described above and such
     approvals are not obtained within ninety (90) days of the effective date of
     the applicable Supplement, either party may terminate the affected
     Location, or if such termination renders the applicable Product unusable,
     the affected Supplment. In any and all such events, Carrier shall reimburse
     MFN for all of its reasonable costs and expenses incurred through the date
     of termination in connection with such terminated Location or Supplement to
     the extent such costs and expenses were included with the Installation
     Charge for such Supplement. If
<PAGE>

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



     during the Lease Term MFN permits other customers of MFN to use the
     building riser conduit for which Carrier has paid the construction cost
     therefor, then MFN will rebate a portion of such construction costs as
     follows: If one such additional customer, MFN will rebate to Carrier
     [**]percent of such construction costs; if two such additional customers,
     MFN will rebate to Carrier an aggregate of [**] percent of such
     construction costs; and if three or more such additional customers, MFN
     will rebate to Carrier an aggregate of [**] percent. MFN shall notify
     Carrier within ten (10) days of any other customer's use of such riser or
     conduit. In no event shall any such additional customers disturb or
     interfere with Carrier's use of the Product.

1.4  Upon the expiration of the Lease Term, or any earlier termination of this
     Agreement or a Supplement, Carrier will promptly remove from any property
     owned, leased or licensed by MFN all Carrier property, equipment and other
     materials used in connection with the applicable Product within forty five
     (45) days from such expiration or termination. Carrier will complete such
     removal in a manner that does not interfere with or damage the Product or
     the Network. If Carrier fails to remove its property within such period,
     such property will be deemed abandoned, and MFN will make such disposition
     of the property as it deems necessary or advisable at Carrier's sole,
     reasonable expense.


2. TERMS OF PAYMENT
   ----------------

2.1  Unless otherwise provided for in the Product Order, Carrier agrees to pay
     the One Time Installation Charge, if any, as provided in each Supplement,
     upon the execution of the Supplement . Carrier will pay to MFN all
     applicable sales or other taxes other than taxes on or measured by MFN's
     income or capital, ("Applicable Taxes"), unless Carrier is eligible for an
     exemption and Carrier provides to MFN an exemption certificate or other
     documentation. Commencing on the Service Date for each Supplement and
     continuing each month thereafter for the duration of the Lease Term,
     Carrier will pay the Monthly Lease Payment for such Supplement plus
     Applicable Taxes in advance for each month. If the Service Date commences
     after the first day of any month or terminates before the last day of a
     month, then the payment for such partial month will be pro rated based on
     the number of days of the Lease Term during that month to the number of
     days in that month. Carrier will include such pro rata payment for the
     initial partial month in the first monthly payment at the commencement of
     the Lease Term for such Supplement.

2.2  If Carrier fails to pay any sum when due pursuant to this Agreement, then,
     in addition to such sum, Carrier will pay interest on such unpaid sum at
     the lower of the highest legal rate of interest permitted in the State of
     New York or one and one-half percent (1.5%) per month.

3. MAINTENANCE, RESTORATION AND REPAIR OF THE NETWORK AND PRODUCT MONITORING
   -------------------------------------------------------------------------

3.1  MFN will provide remote monitoring of the Network and the Product to the
     extent that the Product is incorporated into the Network. MFN will use
     commercially reasonable efforts to maintain the Product in accordance with
     the Specifications (subject to reasonable wear and tear) and the Network in
     good operating condition at all times during the Lease Term. The foregoing
     maintenance will be at no additional charge to Carrier, except as set forth
     in Section 3.4 hereof.

3.2  An "Outage" will mean the complete interruption of communications, or the
     material degradation of performance below the Specifications, on one or
     more of Carrier's Leased Fibers. If an Outage or any other material
     degradation of service on any Leased Fibers occurs Carrier will immediately
     notify MFN by telephone at (888) 636-2778 or through such other
     notification procedure as Parties may establish. Provided that MFN
     personnel or
<PAGE>

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




     contractors have access to affected Carrier facilities immediately upon
     notification, MFN will respond and commence work within two (2) hours after
     the time of notification by Carrier and restore effective use of the
     Product as expeditiously as practicable, but in no event more than four (4)
     hours after receipt by MFN of Carrier's notification, subject to "Force
     Majeure" as provided in Section 11 hereof.

3.3  Except for any Outage caused by or resulting from (i) Force Majeure as set
     forth in Section 11 hereof; (ii) the act or omission of Carrier, its
     employees, agents or contractors; (iii) any of Carrier's equipment or
     facilities used in connection with the Product; or (iv) planned Outages by
     reason of Services which have been scheduled and approved in advance by
     Carrier ("Excepted Outages") in the event of an Outage, Carrier will
     receive from MFN a credit ("Outage Credit") calculated at [**]of the Leased
     Fiber Monthly Lease Payment for the affected Leased Fiber strands for each
     [**] of Outage, up to a maximum of the Leased Fiber Monthly Lease Payment
     for the affected Leased Fiber for [**]. Except in the case of a termination
     as provided in this Section 3, the Outage Credit will be applied against
     future payments which may become due and payable by Carrier to MFN. The
     Outage Credit will be determined by multiplying the number of affected
     fibers by the total route length of the ring such fibers are on, times the
     Monthly Lease Payment for such affected fibers, times [**], times the
     number of [**] Outage periods, up to the maximum set forth above. The
     Outage Credit will be in the form of a cash payment to Carrier by MFN if
     this Agreement is terminated with respect to the affected fiber by either
     Party as provided in Section 3.4 hereof. Outage Credits will not be
     credited or payable for any period of time during which MFN personnel or
     contractors are denied access to Carrier Locations or other facilities to
     remedy an Outage.

3.4  If an Outage occurs and continues for a period longer than [**] for any
     reason other than "Force Majeure" as defined in this Agreement, then at any
     time thereafter, unless and until such Outage is corrected, Carrier can
     terminate the Supplement with respect to the Product subject to the Outage
     by written notice of such termination delivered to MFN. If there are
     Outages that occur for a cumulative period of longer than 360 hours in any
     36 month period for any reason other than "Force Majeure", then for a
     thirty (30) day period thereafter, Carrier may terminate the Supplement
     with respect to the Product subject to such Outages by written notice of
     such termination to MFN. If so terminated, Carrier will have no further
     obligations with respect to such Supplement, including, without limitation,
     any obligation to make any early termination payment with respect to such
     Supplement. Notwithstanding the foregoing, if such Outage occurs and
     continues by reason of a breach by a Carrier of its obligations under this
     Agreement, Carrier will not have any right to terminate this Agreement. The
     Outage Credit and right to terminate will be the sole and exclusive remedy
     of Carrier and liability of MFN for any Outage regardless of the cause of
     such Outage.

3.5  If all or part of the Product requires restoration, replacement or repair
     by reason by any breach of this Agreement by Carrier, its employees,
     agents, or contractors or any of Carrier's equipment or facilities used in
     connection with the Product , such repair, replacement and/or restoration
     will be made by MFN, at Carrier's sole expense, in accordance with MFN's
     then current time and materials rates plus Applicable Taxes. In addition,
     Carrier will not receive any Outage Credit by reason of the foregoing.

3.6  MFN may assign or subcontract to any third party any or all of its
     performance obligations (including, without limitation, maintenance) under
     this Agreement and Product Order at any time, without the consent of
     Carrier, provided that MFN will remain obligated for such performance in
     accordance with the terms of this Agreement.

3.7  MFN will have the right to inspect Carrier's use of the Product at any time
     and from time to time during normal business hours upon at least
     `twenty-four (24) hours" prior notice by MFN.
<PAGE>

4. USE AND OWNERSHIP OF THE PRODUCT
   --------------------------------

4.1  Carrier will not, by itself or through any agent or contractor, make any
     repair to or replacement of the Product or the Network or any other
     equipment or facilities provided by MFN in connection with the Product or
     otherwise. Carrier will not install any equipment to be used with the
     Product or use the Product in any manner which damages or adversely
     interferes with the Product or the Network.

4.2  Carrier will use the Product in full compliance with all applicable
     federal, state and local laws, rules and regulations and all applicable
     franchises, rights of way, leases, licenses, contracts and other
     obligations to third parties (of which it has actual knowledge) with
     respect to the Network or Product. Carrier will obtain and maintain in
     effect during the Lease term all rights, leases, licenses, permits and
     governmental or non-governmental approvals necessary for use of the Product
     by Carrier and its customers.

4.3  Carrier acknowledges and agrees that the Product is provided for use (1)
     exclusively by Carrier and/or affiliated or permitted successor entities
     which control or are controlled by or commonly controlled with Carrier
     ("Affiliates") (2) customers of Carrier and (3) in either case only in the
     ordinary course of business of Carrier. For purposes of this Agreement, the
     ordinary course of Carrier's business shall not include the sale, leasing
     or granting of any rights of use in "dark fiber", as such term is commonly
     understood in the telecommunications industry. Carrier will not without
     MFN's prior written consent, which consent may be withheld at MFN's sole
     discretion, (a) permit or provide access to or use of the Product, in whole
     or part, to any third party (other than a customer of Carrier in the
     ordinary course of business of Carrier), pursuant to (by way of example and
     not in limitation) sublease, license, sublicense or resale, or any other
     right to use, or (b) share or otherwise utilize in conjunction with a third
     party (including without limitation in any joint venture or as part of any
     outsourcing activity) any of the Product. Any breach of this Section 4.3
     will be deemed to be a material breach of this Agreement and in the event
     of such material breach MFN will have the right to immediately terminate
     this Agreement, any applicable Product Orders and Carrier's access to the
     Network, in addition to any and all rights and remedies.

4.4  MFN retains all right, title and interest in and to the Product and the
     Network to the points within the locations specified in the Product Order
     at which MFN's facilities end and Carrier's facilities begin, subject only
     to the grant of access and use provided to Carrier pursuant to this
     Agreement.

4.5  Subject to Section 1.3 hereof, MFN reserves the right to utilize unused
     external building access and space within the building conduit(s)
     constructed by MFN and occupied by the Product at the Locations and
     otherwise, provided that such use does not interfere with or hinder
     Carrier's use of its Product as permitted hereunder.

4.6  MFN shall keep the Product and the Network free from any liens, rights or
     claims of any third party that may materially and adversely affect the
     right of Carrier to use the Product hereunder; provided, however, that MFN
     may pledge the Network so long as MFN uses commercially reasonable efforts
     to obtain a non- disturbance agreement in favor of Carrier.

4.7  MFN and Carrier shall promptly notify each other of any matters pertaining
     to, or the occurrence (or impending occurrence) of, any event of which it
     is aware that could give rise to any damage or impending damage to the
     Product or the Network.

4.8  MFN and Carrier agree to cooperate with each other in complying with any
     requirements applicable to their respective rights and obligations
     hereunder by any Governmental Authority.
<PAGE>

5. AUTHORIZATIONS; RELOCATION; CONDEMNATION
   ----------------------------------------

5.1  "Authorization(s)" will mean all material and applicable governmental or
     non-governmental licenses, easements, rights of way, conduit, pole
     attachment and any other facilities or property rights, licenses,
     contracts, franchises, approvals, permits, orders, consents, and all other
     rights required for MFN to operate and maintain the Network or provide the
     Product to Carrier pursuant to this Agreement.

5.2  MFN will have or obtain by the Service Date, all Authorizations and will
     use commercially reasonable efforts to maintain or renew all such
     Authorizations through the Lease Term and replace such Authorizations with
     reasonably suitable replacement Authorizations if any expire or are
     terminated or discontinued during the Lease Term. If any Authorizations are
     modified, terminated or discontinued and not replaced, and the loss of such
     Authorizations threatens to cause or does cause material financial harm to
     MFN, or prevents or materially interferes with MFN's control, possession
     and/or use of the Network or ability to lease the Product or materially and
     adversely affects the use by Carrier of the Product, then MFN will, at
     Carrier's option, either (i) provide at no cost to Carrier, replacement
     Product or fiber optic capacity on portions of MFN's then existing Network
     (and/or other MFN Networks, including networks belonging to or controlled
     by MFN Affiliates) or on networks of third parties, or (ii) terminate this
     Agreement with respect to the affected Product. The foregoing will be MFN's
     sole and exclusive liability and Carrier's sole and exclusive remedy with
     respect to the foregoing.

5.3  If MFN receives notice of any request, intent or plan by any governmental
     or non-governmental third party, to relocate any material part of the
     Product or any material segment of MFN's Network used in the provision of
     the Product, MFN will promptly notify Carrier of such request, intent, or
     plan. If MFN is required by any such third party to relocate any segment of
     MFN's network used in providing the Product, MFN will give Carrier at least
     one hundred eighty (180) days (or such lesser period of notice that MFN may
     have received) prior written notice of any such relocation ("Relocation
     Notice"). Together with the Relocation Notice, MFN will provide an estimate
     of the cost of such relocation. MFN will relocate the Leased Fibers, and,
     to the extent MFN is not reimbursed for the cost of such relocation by a
     third party, governmental entity or otherwise, Carrier will pay its pro
     rata share of the costs associated with the relocation of the Product based
     upon Carrier's fiber count in such relocated fiber; except, however, that
     Carrier shall have no such payment obligation to the extent that such
     relocation is the direct result of any negligent or willful act or omission
     of MFN. MFN will use its commercially reasonable efforts to secure an
     agreement for reimbursement from any third party, governmental entity or
     otherwise, requiring any relocation of the Network and the Product.

5.4  If any portion of the Network or the Product and/or the Authorizations in
     or upon which the Product has been installed, become the subject of a
     condemnation proceeding which is not dismissed within one hundred eighty
     (180) days after the date of filing of such proceeding and which could
     reasonably be expected to result in a taking by any governmental agency or
     other party having the power of eminent domain for public purpose or use,
     both Parties will be entitled, to the extent permitted under applicable
     law, to participate in any condemnation proceedings for compensation by
     either joint or separate awards for the economic value of their respective
     interests in the Leased Fibers that are subject to such condemnation
     proceeding.
<PAGE>

6. WARRANTIES
   ----------

6.1  MFN warrants to Carrier that upon the applicable Service Dates the Product
     will operate in accordance with the Specifications related thereto.

       EXCEPT AS OTHERWISE EXPRESSLY PROVIDED IN THIS AGREEMENT, MFN DISCLAIMS
       ALL WARRANTIES WHETHER EXPRESS OR IMPLIED INCLUDING ANY AND ALL
       WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE WITH
       RESPECT TO THE (i) NETWORK OR PRODUCT, (ii) THE LEASE GRANTED PURSUANT
       HERETO, (iii) MAINTENANCE SERVICES (iv) CONSTRUCTION AND INSTALLATION
       SERVICES, IF ANY, AND (v) ANY OTHER SERVICE(S) (HEREINAFTER (iii) THROUGH
       (v) WILL COLLECTIVELY BE REFERRED TO AS "SERVICES") PROVIDED BY OR ON
       BEHALF OF MFN HEREUNDER.

7. LIABILITY/INDEMNIFICATION
   -------------------------

7.1  Except for the gross negligence or willful misconduct of a Party hereto and
     except where a specific remedy is provided in this Agreement, the liability
     of each Party to the other Party for damages will be limited to the total
     Installation Charges, if any, the Monthly Lease Payments paid or payable by
     Carrier for the Lease Term during which the damages were incurred. In no
     event will either Party be liable to the other Party for any incidental,
     indirect, special, consequential, exemplary, or punitive damages arising
     out of or relating to this Agreement, the lease granted hereunder, the
     Network, Product or Services provided hereunder, including damages based on
     loss of revenues, profits or lost business opportunities, regardless of
     whether the respective Party had been advised of or could have foreseen the
     possibility of such damages.

7.2  MFN agrees to indemnify, defend and hold Carrier, its officers, directors,
     employees, agents and contractors harmless from and against all loss,
     damage, liability, cost and expense (including reasonable attorney's fees
     and expenses) by reason of any claims or actions by third parties for (i)
     bodily injury, including death and, (ii) damage, loss or destruction of any
     real or tangible personal property (including without limitation the
     Network and Product) which third party claims arise out of or relate to (a)
     any Product or Services provided by or on behalf of MFN hereunder, (b)
     MFN's performance of or failure to perform any term, condition or
     obligation under this Agreement, or (c) any act or omission of MFN's
     directors, agents, employees, contractors, representatives or invitees.
     Carrier agrees to indemnify, defend and hold MFN, its officers, directors,
     employees, agents and contractors harmless from and against all loss,
     damage, liability, cost and expense (including reasonable attorney's fees
     and expenses) by reason of any claims or actions by third parties for (i)
     bodily injury, including death and (ii) damage, loss or destruction of any
     real or tangible personal property (including, without limitation, the
     Network and Product) which third party claims arise out of or relate to (a)
     Carrier's performance of or failure to perform any term, condition or
     obligation under this Agreement, or (b) any act or omission of Carrier's
     directors, agents, employees, contractors, representatives or invitees; or
     (c) Carrier's or its customer's use of the Product and conduct of their
     respective businesses including without limitation the content of any
     video, voice or data carried by Carrier or its customers on the Product or
     Network.

7.3  Except as otherwise set forth in this Agreement, nothing contained herein
     will operate as a limitation on the right of either Party to bring an
     action for damages against any third party based on any act or omission of
     such third party as such act or omission may affect the construction,
     operation, or use of the Product. Each Party agrees to execute such
     documents and provide such commercially reasonable assistance, at the
     claiming Party's
<PAGE>

     sole expense, as may be reasonably necessary to enable the claiming Party
     to pursue any such action against such third party.

8. CONFIDENTIALITY
   ---------------

8.1  The Parties acknowledge and agree that this Agreement and the information
     each Party has provided or will provide in connection with this Agreement
     or that the other Party learns or obtains from a source other than public
     domain or from a source (including a Party) not in violation of any
     obligation of confidentiality, are and will be confidential and proprietary
     to the Party providing such information (the "Providing Party"). The Party
     in receipt of or learning or obtaining the confidential information (the
     "Receiving Party") agrees not to distribute, use or disclose to any third
     party or use (except for the purposes of this Agreement) the confidential
     information of the Providing Party.

8.2  Except as may be required by applicable legal requirements in the course of
     defending or prosecuting a legal, insurance or other claim or as required
     by applicable law, rule or regulation, Receiving Party will restrict
     dissemination of confidential information to only those persons who must
     have access to such confidential information in order to perform their
     respective rights or obligations hereunder. The Receiving Party will
     promptly notify the Disclosing Party of any such required disclosure to
     enable the Disclosing Party to seek protective relief therefrom and shall
     cooperate as the Disclosing Party may request in connection therewith.

8.3  Carrier may disclose the identity of MFN as a supplier of Carrier, and MFN
     may disclose the identity of Carrier as customer of MFN, each with the
     prior written consent from the other; which consent will not be
     unreasonably withheld or delayed; provided, that no such disclosure shall
     imply any endorsement of the disclosed Party or contain any misleading
     reference to the nature of the relationship between the Parties.

8.4  Each Party acknowledges and agrees that the information of the Disclosing
     Party described in this Section 8 constitutes valuable property of the
     Disclosing Party and that Disclosing Party will suffer irreparable injury
     not compensable by money damages for which the Disclosing Party will not
     have an adequate remedy at law in the event of a breach by the Receiving
     Party of the provisions of this Section 8 and therefore the Disclosing
     Party shall be entitled to injunctive relief to prevent or curtail any such
     breach, threatened or actual. The foregoing shall be without prejudice to
     or limitation on any other rights a Party may have under this Agreement, at
     law or in equity.

9. NOTICES
   -------

Unless otherwise provided herein, all notices and communications concerning this
Agreement will be in writing and sent to the address (and contact person)
specified in the Product Order, or at such other address as may be designated in
writing by a Party. Unless otherwise provided herein, notices will be sent by
certified US Postal Service, return receipt requested, or by commercial
overnight delivery service, or by facsimile, and will be deemed delivered, if
sent by US Postal Service, five (5) days after deposit, if sent by facsimile,
upon verification or receipt or, if sent by commercial overnight delivery
service, one (1) business day after deposit therewith.

10.  RENEWAL TERM
     ------------

Provided that Carrier is not in breach of any of its material obligations under
this Agreement and subject to the conditions of this Agreement, Carrier may
renew the term of this Agreement for the Product for one (1) additional renewal
term upon the terms and conditions of this Agreement, except for the length of
such renewal term and the Installation and Lease Fee payments, which the Parties
will negotiate in good faith following Carrier's written request for renewal
delivered to
<PAGE>

MFN no earlier than one year before the scheduled expiration date of the initial
term and no later that ninety (90) days before such expiration date.

11.  TERMINATION/FORCE MAJEURE
     -------------------------

11.1 If any of the following events of default occur, the non-breaching Party
     will have the right to terminate this Agreement or, if applicable, the
     affected Supplement, by written notice following the expiration of any
     periods of time included in the following, such termination to be effective
     on the date set forth in the written notice of termination:

     11.1 (a) If Carrier terminates any Supplement at any time before the
          expiration of the Lease Term (whether before or after the Turnover
          Date) or fails to make any payment hereunder within thirty (30) days
          or receipt of written notice of late payment from MFN, MFN will have
          the right to terminate such Supplement and/or deny access by Carrier
          to the affected Product immediately without further notice to Carrier.

     11.1 (b) If a Party breaches any material term or condition of this
          Agreement (including specifically, and without limitation, any failure
          by MFN to deliver Product that meets the Specifications) and such
          breach remains uncured thirty (30) days after delivery to the
          breaching Party of written notice of such breach, unless the breach is
          of a nature or involves circumstances requiring more than thirty (30)
          days to cure, the time period may be extended for such time as will be
          reasonably required, provided the defaulting party proceeds diligently
          to cure the breach.

     11.1 (c) A Party applies for or consents to the appointment of a receiver,
          trustee or similar officer for it or any substantial part of its
          property or assets, or any such appointment is made without such
          application or consent by such Party and remains undischarged for a
          period of sixty (60) days; or

     11.1 (d) A Party consents to, or fails to contest, the institution of a
          petition or other application of any involuntary bankruptcy,
          insolvency or reorganization proceeding and any such proceeding as
          instituted against such Party remains undischarged for a period of
          sixty (60) days.

11.2 In the event of termination of a Supplement by MFN pursuant to Section 11.1
     hereof or by Carrier after execution of the Supplement and before the end
     of the Lease Term (other than by Carrier for cause as provided in this
     Section 11), MFN will be entitled to receive, and Carrier will immediately
     pay, the early termination charge ("Early Termination Charge") set forth in
     the Product Order and such liquidated damages shall be Carrier's sole
     liability, and MFN's sole remedy, hereunder.

11.3 If any Authorization is modified, terminated or discontinued and not
     replaced as provided in Section 5.2 of these General Terms and Conditions,
     and MFN has not notified Carrier in writing within thirty (30) days after
     the occurrence of such modification, termination or discontinuance that MFN
     will provide replacement Product or capacity as provided in Section 5.2,
     then and thereafter Carrier has the right, exercisable in its sole
     discretion, to terminate the applicable Supplement with respect to the
     affected Product upon thirty (30) days prior written notice (or such other
     notice as is practicable under the circumstances) without liability
     whatsoever by Carrier to MFN or any party claiming by, through or under
     MFN.

11.4 Neither Party will be in breach of this Agreement resulting from delay or
     prevention of performance of such Party which is caused by any act
     attributable to an occurrence or an event of "Force Majeure" as defined
     herein. Neither party will, however, be relieved of liability for failure
     of performance due to a claimed Force Majeure hereunder if such failure is
     due to causes arising out of its own negligence or to removable or remedial
     causes that it
<PAGE>

     fails to remove or remedy using commercially reasonable efforts and within
     a reasonable period of time. In an event of Force Majeure occurs and is
     continuing for a period in excess of thirty (30) days and results in
     Carrier's inability to utilize any Product, either party will have the
     right to terminate the Supplement relating to the affected Product and
     neither party shall have any liability to the other with respect to such
     affected Product or such termination.

11.5 The term "Force Majeure" will mean any cause beyond the control of Carrier
     (or MFN, as applicable) which, by the exercise of due foresight, Carrier
     (or MFN) could not reasonably have been expected to avoid, and which by the
     exercise of reasonable diligence, Carrier (or MFN) will be unable to
     overcome, including but not limited to action by governmental authority
     including without limitation moratorium on any activities related to the
     Agreement, third party labor dispute, flood, earthquake, fire, lightning,
     epidemic war, riot, civil disturbance, sabotage and the like. The party
     affected by an event of Force Majeure (the "Affected Party") will notify
     the other party (the "Other Party") promptly of any occurrence or condition
     which, in the Affected Party's reasonable opinion, warrants an extension of
     time. Such notice will specify in detail the anticipated length of delay,
     the cause of the delay and a timetable by which any remedial measures will
     be implemented.

12.  ASSIGNMENT; SUCCESSION
     ----------------------

12.1 Carrier may assign this Agreement to any of its Affiliates or to any
     successor by merger, consolidation, purchase or acquisition of all or
     substantially all of the assets or capital stock of Carrier. Upon any
     permitted assignment (or delegation) hereunder, Carrier will remain jointly
     and severally responsible for the performance under this Agreement, unless
     released in writing by MFN. Any permitted assignee will expressly assume
     all liabilities hereunder prior to the effectiveness of such assignment.
     Any attempted assignment or delegation without such consent will be null
     and void and may be deemed by MFN, in its sole discretion, to constitute a
     material breach of this Agreement.

12.2 The Agreement and Product Order will be binding upon and inure to the
     benefit of the Parties hereto and their respective successors and permitted
     assigns.

13.  GOVERNING LAW
     -------------

13.1 THIS AGREEMENT WILL BE INTERPRETED AND CONSTRUED IN ACCORDANCE WITH THE
     INTERNAL LAWS OF THE STATE 0F NEW YORK WITHOUT GIVING EFFECT TO ITS
     PRINCIPLES OF CONFLICTS OF LAWS.

14.  SURVIVAL
     --------

The Parties' respective representation, warranties, and covenants, together with
obligations of indemnification, confidentiality and limitations on liability
will survive the expiration, termination or rescission of this Agreement and
continue in full force and effect in accordance with their respective terms.

15.  ENTIRE AGREEMENT
     ----------------

This Agreement, Product Order, Supplements, and all addenda attached hereto
constitute the entire agreement between the parties hereto with respect to the
subject matter hereof and supersede any and all prior negotiations,
understandings, and agreement with respect hereto, whether oral or written,
except for any existing non-disclosure agreements between the parties, which
shall remain in full force and effect in accordance with its or their terms.
<PAGE>

16.  REMEDIES CUMULATIVE
     -------------------

Except as otherwise expressly provided, the rights and remedies set forth in
this Agreement will be in addition to, and cumulative of, all other rights and
remedies at law or in equity.

17.  REPRESENTATIONS, WARRANTIES AND COVENANTS
     -----------------------------------------

Each Party represents, warrants and covenants to the other that (a) it is a
corporation duly organized, validly existing and in good standing under the laws
of the state of its organization, (b) it has all requisite power and authority
to enter into and perform its obligations under this Agreement and Product Order
and (c) this Agreement, when executed, will become the legal, valid and binding
obligation of such Party.

18.  MISCELLANEOUS
     -------------

18.1 The covenants, undertakings, and agreements set forth in this Agreement
     will be solely for the benefit of and will be enforceable only by the
     Parties hereto or their respective successors or permitted assigns.

18.2 The headings of the Sections in this Agreement are strictly for convenience
     and will not in any way be construed as amplifying or limiting any of the
     terms, provisions or conditions thereof.

18.3 In the event any term of this Agreement will be held valid, illegal or
     unenforceable, in whole or in part, neither the validity of the remaining
     part of such term nor the validity of the remaining terms of this Agreement
     will be in any way affected thereby.

18.4 This Agreement may be amended only by a written instrument executed by the
     Parties.

18.5 No failure to exercise and no delay in exercising, on the part of either
     Party hereunder, any right, power or privilege hereunder will operate as a
     waiver hereof, except as expressly provided herein.

18.6 This Agreement may be executed in multiple counterparts, each of which will
     constitute one and the same instrument.



Metromedia Fiber Network Services, Inc.    StorageNetworks, Inc.



By:  ___________________________            _______________________________
          Nicholas M. Tanzi                       Name:
          Senior Vice President                   Title:
<PAGE>

                     Fiber Optic Private Network Agreement

                                    Exhibit A

                           Leased Fiber Specifications
                           ---------------------------

MFN will perform fiber testing as described below on each Leased Fiber and will
provide the documentation (hard copy and/or diskette) of results to the Carrier
at the Turnover Date.  Each "span" will be defined in documentation included in
the Carrier's Turnover Date package.  Acceptance of a span by Carrier will be an
acknowledgement by the Carrier that all Leased Fiber complies with all
performance criteria contained herein.

1)   Power testing: This end-to-end loss measurement will be conducted for each
     Leased Fiber in the span and from both directions using an
     industry-accepted laser source and power meter. The bi-directional average
     will be used to determine the end-to-end loss of the span at each
     appropriate wavelength. This test will be conducted at both 1310 nm and
     1550 nm for Standard Single Mode Fiber; Dispersion Shifted Fiber (True
     WaveTM, LEAFTM, etc.) will be tested at 1550 nm only. In the event that a
     span consists of both Standard Single Mode and Dispersion Shifted fiber
     types, only 1550 nm testing will be conducted. This power testing will
     ensure fiber continuity and the absence of crossed fibers in the span.
     Power testing will only be conducted where the Leased Fiber is terminated
     by MFN in fiber distribution panels at both ends of the span.

2)   OTDR testing: All traces will be provided in hard copy and diskette form
     using GR 196 format. This testing will be conducted at both 1310 nm and
     1550 nm wavelengths when the Leased Fiber consists of Standard Single Mode
     Fiber, but will be done at 1550 nm only if the Leased Fiber consists of
     either Dispersion Shifted Fiber (True-WaveTM, LEAFTM, etc.) or a
     combination of Single Mode and Dispersion Shifted fiber types.

     OTDR testing will be conducted on a bi-directional basis for each Leased
     Fiber in each span at the appropriate wavelengths for the Leased Fiber
     described above. However, if due to length or attenuation reasons that the
     Leased Fiber span exceeds the dynamic range of an OTDR, a portion or all of
     the span may be tested on a unidirectional basis only. Alternatively, the
     Leased Fiber span may be divided into shorter testing spans, to the extent
     reasonably possible, in order to obtain bi-directional analysis. Also, in
     instances where a Carrier intends to accept Leased Fiber that is not
     terminated at one end by MFN in a fiber distribution panel (such as in a
     manhole or handhole) only unidirectional testing will be performed.

     The Turnover documentation package delivered at the Turnover Date will
     contain the actual traces that detail the testing parameters (including
     pulse width, averaging and range). The average bi-directional splice loss
     for all splices within each span will be of 0.15 dB or less while each
     connector pair (such as at a FDP) will have an average bi-directional
     connector loss for all splices within each span of 0.5 dB or less for all
     connectors within each span. (Note that the front and end connector of the
     span can only be measured uni- directionally and will also have a loss
     equal to or less than 0.5 dB). In the event that OTDR acceptance testing
     must be done on a unidirectional basis (for reasons described above), an
     average per span splice loss will be 0.30 dB.

     All traces will be provided in hard copy and/or diskette form using GR 196
     format. If the average bi-directional splice loss of each span exceeds 0.15
     dB (or 0.30 dB uni-directionally), MFN will provide upon the Carrier's
     request documentation of at a least three attempts to reduce this value to
     below 0.15 dB (0.30 dB uni-directionally). The only exception to this
<PAGE>

     will be in the instance of a splice between two different fiber types
     (Standard Single-mode to Dispersion Shifted, Depressed-Clad to Matched
     Clad, fibers with different mode-field diameters).

Carrier should also note that the loss and/or reflectance of the front-end
connector (as measured using a launch cord) is only an indicator of a problem
such as a defective port, bulkhead, or the like.  Since a different patch cord
will be used by  Carrier (that connects to their equipment, for example) to mate
to this connector, a different loss and/or reflectance may occur.
<PAGE>


                                     Annex I

                                   Supplement

Reference is made to the Fiber Optic Private Network Agreement dated October 8,
1999 ("Agreement") by and between Metromedia Fiber Network Services, Inc.
("MFN"), One North Lexington Ave., Fourth Floor, White Plains, New York 10601,
and StorageNetworks, Inc. ("Carrier"), 100 Fifth Avenue, Waltham, Massachusetts
02451, to which this Supplement effective __________ shall be attached and is
hereby made a part thereof.  The Agreement is hereby supplemented as follows:

Carrier hereby orders and MFN hereby agrees to provide Leased Fiber as follows:

     1.   Lease Term: Coterminous with the Lease Term for the Supplement with
          the earliest Service Date.

     2.   Number of Leased Fibers:

     3.   Number of Leased Fiber Miles:

     4.   Carrier locations ("Location(s)"):

     5.   Specifications pertinent to the Leased Fiber: Exhibit to the
          Supplement.

     6.   Installation Charge and Monthly Lease Payments:

          6.1  One Time Installation Charge:

          6.2  Monthly Lease Payments:

          Applicable Taxes (as defined in the Agreement) on any Installation
          Charge incurred pursuant to this Supplement and all Lease Payments are
          to be paid by Carrier as and when due. In no event shall Applicable
          Taxes include any franchise or other right of way fees or similar
          charges or impositions assessed upon MFN. Carrier shall have the right
          to protest any new or additional taxes imposed on the Leased Fiber
          during the Lease Term.

     7.   Estimated Installation Completion Dates:

     8.   Early Termination Charge:

          In the event of termination of this Supplement pursuant to Section
          11.2 of the General Terms and Conditions of this Agreement, Carrier
          will pay to MFN an Early Termination Charge (plus Applicable Taxes)
          for the affected Leased Fiber determined as follows:
<PAGE>

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


     Termination during the first year of the Lease Term - [**]of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     first year, plus [**]of all unpaid Leased Fiber Monthly Lease Payments for
     the affected Leased Fiber for the second year, plus [**]of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     third year, plus[**]of all unpaid Leased Fiber Monthly Lease Payments for
     the affected Leased Fiber for the fourth year, plus [**]of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     fifth year, plus [**]of all unpaid Leased Fiber Monthly Lease Payments for
     the affected Leased Fiber for the sixth through twentieth years.

     Termination during the second year of the Lease Term - [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     second year, plus [**]of all unpaid Leased Fiber Monthly Lease Payments for
     the affected Leased Fiber for the third year, plus [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     fourth year, plus [**]of all unpaid Leased Fiber Monthly Lease Payments for
     the affected Leased Fiber for the fifth year, plus [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     sixth through twentieth years.

     Termination during the third year of the Lease Term- [**]of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     third year, plus [**] of all unpaid Leased Fiber Monthly Lease Payments for
     the affected Leased Fiber for the fourth year, plus [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     fifth year, plus [**]of all unpaid Leased Fiber Monthly Lease Payments for
     the affected Leased Fiber for the sixth through twentieth years.

     Termination during the fourth year of the Lease Term-[**]of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     fourth year, plus [**] of all unpaid Leased Fiber Monthly Lease Payments
     for the affected Leased Fiber for the fifth year, plus [**] of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     sixth through twentieth years.

     Termination during the fifth year of the Lease Term- [**]of all unpaid
     Leased Fiber Monthly Lease Payments for the affected Leased Fiber for the
     fifth year, plus [**] of all unpaid Leased Fiber Monthly Lease Payments for
     the affected Leased Fiber for the sixth through twentieth years.

     Termination during the sixth through twentieth year of the Lease Term -
     [**] of all unpaid Leased Fiber Monthly Lease Payments for the affected
     Leased Fiber for the balance of the Lease Term.

9.   Fiber, Locations and Requirements

10.  MFN address (and contact person) is as follows:

     Metromedia Fiber Network Services, Inc.
     One North Lexington Ave., Fourth Floor
     White Plains, NY  10601
<PAGE>

     Attn.:  Vice President - Marketing

     For purposes of declaring a default or termination, a copy of the notice
     must be sent to:

     Vice President - Legal Affairs
     Metromedia Fiber Network Services, Inc.
     One North Lexington Ave., Fourth Floor
     White Plains, NY  10601
<PAGE>

     Carrier address (and contact person) is as follows:

     StorageNetworks, Inc.
     100 Fifth Avenue
     Waltham, Massachusetts 02451
     Attn:  Chief Financial Officer

     For purposes of declaring a default or termination, a copy of the notice
     must be sent to:

     General Counsel
     StorageNetworks, Inc.
     100 Fifth Avenue
     Waltham, Massachusetts 02451


Metromedia Fiber Network Services, Inc.     StorageNetworks, Inc.


By:  /s/Nicholas M. Tanzi                   By:
    ---------------------------               -------------------------
     Nicholas M. Tanzi                      Name:
     Senior Vice President                  Title: