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                                                                    Exhibit 10.3

                             TAX SHARING AGREEMENT

          Tax Sharing Agreement, dated as of _______ ___ 2000 (the "Effective
Date"), by and between Frontier Corporation, a New York corporation ("Parent")
and GlobalCenter Inc., a [Delaware] corporation ("Sub").

                                  WITNESSETH:
                                  ----------

          WHEREAS, Sub and each of its subsidiaries that are includible
corporations within the meaning of section 1504 of the Internal Revenue Code of
1986, as amended (the "Code"), (collectively, the "Sub Group") are members of
the affiliated group of corporations of which Parent is the common parent (the
"Parent Group"), which files a Consolidated Tax Return (as defined below);

          WHEREAS, Parent and Sub desire to agree upon an equitable method for
determining the financial consequences to them of the Sub Group continuing to be
included in the filing of the Consolidated Tax Return, and comparable state,
local, and foreign income or franchise tax returns, of the Parent Group for the
current and each subsequent taxable year, the responsibility for Contests (as
defined below), and certain other matters;

          NOW THEREFORE, in consideration of the mutual covenants contained
herein, Parent and Sub hereby agree as follows:
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1.    Consolidated Tax Returns
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1.1      Filing by Parent
         ----------------

          As long as Sub and any member of the Sub Group is a member of the
Parent Group, Sub agrees that it will, and will cause each member of the Sub
Group to, consent to and join in the filing by Parent of the consolidated
Federal income tax returns ("Consolidated Tax Returns") for the Parent Group as
Parent may elect to file and will execute such documents and take such action as
Parent may reasonably request in connection therewith. For each taxable year for
which Parent determines to file a Consolidated Tax Return, Parent shall file
such Consolidated Tax Return on a timely basis, taking into account any
extensions granted by the Internal Revenue Service (the "Service") of the due
date of such filing. Nothing in this Agreement, however, shall be construed to
require Parent to file a Consolidated Tax Return for any taxable year.

1.2      Payment by Parent of Parent Group Tax Liability
         -----------------------------------------------

          For each taxable year for which Parent files a Consolidated Tax
Return, Parent shall timely pay or discharge, or cause to be timely paid or
discharged, the consolidated Federal income tax liability (the "Tax") of the
Parent Group, if any, for such taxable year.

1.3      Tax Sharing Payment
         -------------------
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(a)       Federal Income Taxes. With respect to any Taxes, no later than five
          --------------------
days prior to the due date (including extensions) of any Consolidated Tax Return
of the Parent Group if such Tax return is for a taxable period, or portion
thereof, beginning on or after the Effective Date (with the first such period
beginning on the Effective Date) and ending thereafter but no later than the
date upon which no member of Sub Group is included in the Parent Group
Consolidated Tax Return (a "Determination Year"):

          (i)     Sub shall pay to Parent (with interest at the Applicable
     Federal Rate as defined in section 1274(d) of the Code computed from such
     due date (without extensions)) the sum of (I) the aggregate amount of any
     Tax that would not have been incurred by the Parent Group but for the
     inclusion of any legal entity that is a member of the Sub Group during any
     Determination Year in the Parent Group and (II) the aggregate amount of any
     Tax refund, credit, or other Tax benefit that would have been realized or
     received with respect to such Consolidated Tax Return (or any other Tax
     return that has been or could have been filed) by the Parent Group but for
     the inclusion of any legal entity that is a member of the Sub Group during
     any Determination Year in the Parent Group; and

          (ii)    Parent shall pay Sub (with interest at the Applicable Federal
     Rate as defined in section 1274(d) of the Code computed from such due date

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     (without extensions)) the sum of (I) the aggregate amount of any Tax that
     would have been incurred by the Parent Group but for the inclusion of any
     legal entity that is a member of the Sub Group during any Determination
     Year in the Parent Group and (II) the aggregate amount of any Tax refund,
     credit, or other Tax benefit realized or received with respect to such Tax
     return that would not have been realized or received by the Parent Group
     but for the inclusion of any legal entity that is a member of the Sub Group
     during any Determination Year in the Parent Group;

(b)       The consolidated return regulations (the "Consolidated Return
Regulations") and the Consolidated Tax Returns filed by the Parent Group
pursuant to this Agreement shall determine the timing of the recognition of Tax
items with respect to deferred intercompany transactions as defined in the
Consolidated Return Regulations and the determination of which group (and which
member thereof) shall bear the Tax benefit or burden of such Tax items, and each
group shall be responsible for the Tax items recognized by its respective
members with respect to any deferred intercompany transactions.

(c)       With respect to the first Determination Year, all computations under
Section 1.3(a) shall be made as if Parent Group and Sub Group first joined in
filing a Consolidated Tax Return as of the Effective Date and began a new
taxable period upon the Effective Date. Similarly, on the date that Sub Group
ceases to join Parent

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Group in filing a Consolidated Tax Return (the "Deconsolidation Date"), the
Determination Year shall end upon the Deconsolidation Date.

1.4      Adjustments
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(a)      If (I) as a result of any (A) final determination by or settlement with
the Service or (B) any court decision that has become final, the Tax of the
Parent Group for any taxable year is subsequently increased or decreased from
the amount shown on a return, amended return, or refund claim or (II) as a
result of any change in any item that affects the computations under Paragraph
1.3 hereof the Parent Group files an amended Tax return (the events described in
the immediately preceding clauses (I) and (II), a "Recomputation Event"), then a
recomputation of the amounts payable under Paragraph 1.3 hereof shall be made.
Sub shall pay to Parent, or Parent shall pay to Sub, as the case may be, an
amount equal to the difference between the amount due under Paragraph 1.3
hereof, as the case may be, after such recomputation and the amount previously
paid under such Paragraphs in respect thereof.

(b)      Any interest or penalties provided under the Code that are payable by
the Parent Group as a result of an adjustment described in this Paragraph 1.4
shall be equitably allocated between the Parent Group and the Sub Group to
reflect the extent to which the Sub Group's operations contributed to such items
in respect of a Determination Year.

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(c)  Sub shall pay to Parent such amounts as Parent shall reasonably request in
respect of payment made by Parent to a taxing authority on account of a
contested Federal income tax liability allocable to the Sub Group. Such amounts
shall be credited against the payments due to Parent pursuant to Paragraph
1.4(a) hereof, and any excess payments shall be repaid to Sub.

1.5      Reimbursement for Expenses
         --------------------------

          Sub shall reimburse Parent for any expenses (i.e., legal, accounting,
professional fees, and an allocable portion of administrative overhead)
reasonably incurred by Parent in connection with any Contest, but only to the
extent that such fees and related expenses are reasonably allocable to the
portion of such Contest as it may relate to a tax liability of the Sub Group.

1.6      Timing of Payments
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(a)  Any amount required to be paid by Sub to Parent as a result of an
adjustment or the imposition of interest or penalties pursuant to Paragraphs
1.4(a) or 1.4(b) hereof, respectively, or related to a payment pursuant to
Paragraph 1.4(c) hereof, shall be made no later than three (3) business days
preceding the date upon which Parent makes a corresponding payment to the taxing
authority; provided that Parent has notified Sub of its intention to make such
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payment no later than ten (10) business days prior to such payment date.
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(b)  In the case of any refund receivable by Parent as a result of an adjustment
pursuant to Paragraph 1.4(a) hereof, Parent may defer making a payment to Sub in
respect of Sub's share of such refund until three (3) business days following
the date upon which Parent receives the refund amount from the taxing authority.

(c)  Any amounts required to be paid pursuant to Paragraph 1.5 hereof shall be
made pursuant to a written request (a "Reimbursement Request") submitted by
Parent to Sub, which request shall set forth in reasonable detail the portion of
the expenses that are reasonably allocable, pursuant to Paragraph 1.5 hereof, to
the Sub Group. Any payment due from Sub shall be made no later than three (3)
business days after Parent has submitted a Reimbursement Request to Sub;
provided, however, that, in the case of out-of-pocket expenses, no payment shall
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be made by Sub earlier than ten business (10) days preceding the date upon which
Parent pays the out-of-pocket expenses to the person to whom such payment is due
and owing.

(d)  The parties hereto intend that all amounts required to paid hereunder shall
be paid in full when due. In the event that any such amount is not paid on or
prior to the due date hereunder, such amount shall bear interest, during the
period that such amount remains due and owing, at a rate equal to the short-term
applicable Federal rate(s) for such period as defined under section 1274(d)
under the Code and determined by the Service from time to time.
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1.7      Tax Attributes
         --------------

          Sub and Sub Group shall retain their respective tax attributes upon
deconsolidation from Parent Group in accordance with Treas. Reg. section 1.1502-
21(b).

2.   Elections and Determinations
     ----------------------------

2.1      Elections.
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          All actions and elections, including the taking or making of any
applicable deemed action or election under the Code (e.g., the making of (or
failing to make) any election, consent, or filing with respect to any matter
related to this Agreement and any deemed actions, elections, consents, or
filings of the members of the Sub Group which would affect their separately
calculated liability under this Agreement) shall be made or determined solely by
Parent.

2.2      Determinations.
         --------------

          The determination of all amounts due hereunder shall be made by
Parent; provided, however, that in performing the calculation under Paragraph
        --------  -------
1.3 hereof, each item of income, gain, loss, deduction, or credit of the members
of the Sub Group shall be determined in a manner consistent with the treatment
of such item for purposes of the Consolidated Tax Return as filed, and any
amendments thereto, to the extent permitted under the Code to a corporation
filing on the basis set forth in Paragraph 1.3 hereof. Sub shall, and shall
cause the members of the Sub Group to, cooperate reasonably with Parent and
provide to Parent, as Parent may reasonably request from time to time, access to
the books and records of the members of the Sub Group to
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cooperate reasonably with Parent and provide to Parent, as Parent may reasonably
request from time to time, access to the books and records of the members of the
Sub Group to permit Parent to make the foregoing determinations.

3.   State, Local, and Foreign Taxes
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     Parent, Sub, and the members of the Sub Group, shall each pay its own
state, local, and foreign income and franchise taxes; provided, however, in the
                                                      --------  -------
event that any member of the Sub Group and any member of the Parent Group are
required or may elect, under any state, local, or foreign income tax law, to
file combined, consolidated, unitary, or similar income or franchise tax
returns, and, in the case of an election, Parent elects, or causes any such
members to elect, to file such combined, consolidated, unitary, or similar
state, local, or foreign income or franchise tax returns for such members for
any Determination Year, the financial consequences to Parent and the Sub Group
of filing such returns shall be determined in a manner as similar as possible to
that provided herein for Federal income tax purposes.

4.   Indemnification
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     Parent shall be liable for, and shall indemnify, defend, and hold harmless
the members of the Sub Group from and against, (i) all Taxes (including
penalties and interest) of the Parent Group, (ii) all state, local, and foreign
taxes arising in connection with the filing of a combined, consolidated,
unitary, or similar income or
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franchise tax return described in the Paragraph 3 hereof, and (iii) all
liability (as a result of the application of Treasury Regulation section 1.1502-
6 or a comparable state or local law) for income taxes of (x) any member of the
Parent Group (other than any member or former member of the Sub Group) or (y)
any person which is or has been affiliated with any member of the Parent Group
(other than any member or former member of the Sub Group) or with which any
member of the Parent Group (other than any member or former member of the Sub
Group) joins, or has ever joined (or is or has ever been required to join) in
the filing of any consolidated, combined, unitary, or similar unitary income or
franchise tax return; provided, however, that (x) Parent shall not indemnify the
                      --------  -------
members of the Sub Group for any taxes referred to in clauses (i), (ii), and,
(iii) of this Paragraph 4 that are attributable to any amounts in respect of
such taxes that are payable by Sub to Parent pursuant to Paragraphs 1.3(a)(i),
1.4, and 3 hereof, but only to the extent that such amounts have not been
previously paid by Sub to Parent and (y) any amount paid by any member of the
Sub Group to a taxing authority in respect of any taxes referred to in the
clauses (i), (ii), and (iii) of this Paragraph 4 for which the members of the
Sub Group are precluded from seeking indemnification pursuant to the immediately
preceding clause (x) shall be applied to and reduce any amount owing by Sub to
Parent pursuant to Paragraphs 1.3(a)(i), 1.4, and 3 hereof.

5.   Tax Controversies
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     If any party is made aware as part of an audit or other administrative
proceeding affecting any taxable period during which Parent and Sub joined in
filing a Consolidated Tax Return (a "Contest" which term shall include any
judicial proceedings, or appeals of such proceedings, in connection therewith),
that a taxing authority is asserting a claim for any tax, then such party shall
promptly notify the other party of such claim in writing. In the case of any
Contest, Parent shall control the proceedings related to such Contest and shall
be entitled to select tax counsel (or other tax advisors) to represent Parent
Group or any member of the Parent Group in such proceedings. Sub shall, and
shall cause any member of the Sub Group to, execute any powers-of-attorney or
similar documents (including the execution of any document granting a waiver of
the statutory period for the assessment of any tax) as may be desired by, or
necessary for, Parent to control such Contest.

6.   Term
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     This Agreement shall continue in full force and effect until such time that
the parties hereto agree in writing to terminate this Agreement. For any taxable
year, or portion thereof, in which Sub is not included in the Consolidated Tax
Return (a "Nonconsolidating Period"), (i) Sub shall not be obligated to make
payments pursuant to Paragraph 1.3 hereof in respect of such Nonconsolidating
Period and (ii) Parent shall not be obligated to make payments pursuant to
Paragraph 1.4(a) hereof in respect of such Nonconsolidating Period.
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7.   Notices
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     All payments, notices, demands, or communications required or permitted to
be given hereunder shall be effective if delivered personally or if sent by
Federal Express or a similar courier service, or by certified mail return
receipt requested or facsimile transmission, addressed as follows:

     to Parent:

             [local address]

     with copy to:

             [legal counsel]

     to Sub

             [local address]

     with copy to:

             [legal counsel]

or to such other address or to the attention of such other person as a party
may, from time to time, designate by written notice to the other party. Any
notice given hereunder shall be deemed to be given on the date when such notice
is (i) personally delivered, (ii) sent by Federal Express or a similar courier
service, (iii) transmitted via facsimile, or (iv) delivered based on the date
reflected in the certified mail return receipt.

8.   Amendment of Agreement
     ----------------------
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     This Agreement may not be amended, supplemented or discharged, except by an
instrument in writing signed by all parties hereto.

9.   Successors and Assigns
     ----------------------

     This Agreement shall be binding upon, and inure to the benefit of Parent,
Sub, and their respective successors and assigns and any reference herein to
Parent and Sub shall be deemed to include their respective successors and
assigns.

10.  Severability
     ------------

     If any term, provision, covenant, or restriction of this Agreement is held
by a court of competent jurisdiction to be invalid, void, or unenforceable, (i)
the remainder of the terms, provisions, covenants, and restrictions set forth
herein shall remain in full force and effect and shall in no way be affected,
impaired, or invalidated and (ii) the parties hereto shall use their best
efforts to find and employ an alternate means to achieve the same or
substantially the same result as that contemplated by such term, provision,
covenant, or restriction.

11.  Further Assurances
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     The parties hereto shall make, execute, acknowledge, and deliver such other
instruments and documents, and take all such other actions, as may be reasonably
required in order to effectuate the purposes of this Agreement and to consummate
the transactions contemplated hereby.

12.  Waivers
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     No failure or delay on the part of the parties in exercising any power or
right hereunder shall operate as a waiver thereof, nor shall any single or
partial exercise of any such right or power, or any abandonment or
discontinuance of steps to enforce such a right or power, preclude any other or
further exercise thereof or the exercise of any right or power. No modification
or waiver of any provision of this Agreement nor consent to any departure by the
parties therefrom shall in any event be effective unless the same shall be in
writing, and then such a waiver or consent shall be effective only in the
specific instance and for the purpose for which given.

13.  Setoff
     ------

     All payments to be made by any party under this Agreement shall be made
without setoff, counterclaim, or withholding, all of which are expressly waived.

14.  Change of Law
     -------------

     If, due to any change in applicable law or regulations or
interpretation thereof by any court of law or other governing body having
jurisdiction subsequent to the date of this Agreement, performance of any
provision of this Agreement or any transaction contemplated thereby shall become
impracticable or impossible, the parties hereto shall use their best efforts to
find and employ an alternate means to achieve the same or substantially the same
result as that contemplated by such provision.

15.  Headings
     --------
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     Descriptive headings are for convenience only and shall not control or
affect the meaning or construction of any provision of this Agreement.

16.  Counterparts
     ------------

     For the convenience of the parties, any number of counterparts of this
Agreement may be executed by the parties hereto, and each such executed
counterpart shall be, and shall be deemed to be, an original instrument.

17.  Effect of this Agreement
     ------------------------

     This Agreement shall supersede any other tax sharing arrangement or
agreement in effect between the parties. Nothing in this Agreement is intended
to change or otherwise affect any election made by or on behalf of the Parent
Group with respect to the calculation of earnings and profits under section 1552
of the Code.

18.  Entire Agreement
     ----------------

     This Agreement constitutes the entire Agreement among the parties relating
to the allocation of the consolidated and combined tax liabilities of the Parent
Group between or among the parties.

19.  Governing Law
     -------------

     This Agreement shall be governed by and construed in accordance with the
laws of the State of ____________.

                                    Parent
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                         By:___________________________________
                            Name:
                            Title:


                         Sub


                         By:___________________________________
                            Name:
                            Title: