EXHIBIT 10.20
                                   CAIS, INC.
                             1232 22nd Street, N.W.
                            Washington, D.C.  20037
                              Tel. (202) 463-8500
                               Fax (202) 463-7190
                                        
                                                    January 26, 1999

Mr. David D. Goodman
Inline Connection Corporation
730 N. Danville Street
Arlington, VA  22201
 
Dear David:

This will confirm our agreement regarding certain modifications to the November
5, 1996 Agreement for Cooperative Use of Communication Patents between Inline
Connection Corporation and you in your individual capacity, on the one hand, and
CAIS, Inc., on the other hand, as previously amended (the "Agreement").

For good and valuable consideration, the receipt and sufficiency of which is
hereby acknowledged, the Agreement is hereby clarified, and to the extent
required, amended and modified as follows:

1.   Inline, CAIS, and you agree that the $750,000 compensation benchmark as set
forth in the first paragraph of Section 11 of the Agreement is deemed to have
been met by CAIS. Pursuant to the terms of Section 11, fifty percent (50%) of
the ownership of Inline's interest in all of the properties set forth on
Appendix I of the Agreement, as same may be supplemented from time to time in
accordance with the provisions of this Agreement, shall be assigned to CAIS.
Inline and you agree to timely execute all assignment and/or other similar
documents as reasonably requested by CAIS to effectuate and evidence such
assignments. The parties acknowledge that the terms of this paragraph 1 shall
not apply to, or affect, those patent rights related to PCT Serial No.
PCT/US97/12045 that have previously been assigned to CAIS under the terms of a
letter agreement between Inline and CAIS dated January 6, 1999, and assignment
documents entered into concurrently therewith.

2.   Inline, CAIS, and you agree that for purposes of Section 7.4 of the
Agreement, CAIS or a CAIS affiliate shall be deemed to be the "underlying
provider" of the Internet or other information service, video service, or
digital audio radio service that is delivered to end users in a structure by use
of the TWP Technology that is installed in such structure where either:

     (i)  CAIS or a CAIS affiliate is selling its own Internet or other
     information services, video services, or digital audio radio services, or

     (ii) CAIS or a CAIS affiliate is re-selling a third party's Internet or
     other information services, video services, or digital audio radio
     services.:

3.   With regard to Inline's payment of its patent expenses, CAIS agrees to
advance $75,000 in funds to Inline for Inline toward such expenses within two
months of today's date pursuant to  the terms of the letter amendment to the
Agreement dated August 1, 1997.  CAIS shall negotiate an arrangement acceptable
to CAIS and Inline's patent counsel, Fish & Richardson, as to the timing of
Inline's payments to Fish & Richardson from such advances.

4.   Inline and CAIS agree that the "first anniversary" minimum annual royalty
payment by CAIS to Inline as provided for in Section 8 of the Agreement shall be
paid to Inline upon CAIS's receipt of funds from the private placement.  Inline
acknowledges that, as provided in paragraph 1(b) of the letter 

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amendment to the Agreement dated August 1, 1997, 50% of the initial $100,000
minimum annual royalty paid shall be offset as repayment by Inline of patent
expense advances previously made by CAIS to Inline.

5.   CAIS and Inline agree that the  "second anniversary" minimum annual royalty
payment by CAIS to Inline as provided for in Section 8 of the Agreement shall be
due to Inline from CAIS on December 31, 1999, and subsequent anniversary minimum
royalty payments shall be due from Inline to CAIS on December 31 of each year
thereafter, subject to the terms of the Agreement as amended; provided, however,
that in the event that Inline fails to complete the video subsystem of the TWP
System as described in Section 4 of the Agreement on or before December 31,
1999, the minimum annual royalty obligation shall be suspended until such time
as Inline completes such video subsystem.  CAIS agrees to expend up to an
additional $100,000 for R&D efforts for such video subsystem subject to the
budgeting and other provisions applicable to such R&D expenditures as provided
in Section 4.

6.   CAIS agrees to advance Inline $200,000 within 60 days following the date
any initial public offering of common shares or other equity securities of
CAIS's parent company, CGX Communications, Inc., pursuant to a registration
statement filed on Form S-1, or such other form as may then be applicable,
becomes effective under the Securities Act of 1933, as amended, and the rules
and regulations thereunder.  Such $200,000 advance shall be offset against
future royalty payment obligations that would otherwise be due from CAIS to
Inline after December 31, 2000.

All other terms and conditions of the Agreement, as previously amended, remain
in full force and effect.

If the above reflects your understanding and meets with your approval, please so
indicate by countersigning below on behalf, respectively, of Inline and in your
individual capacity.

Sincerely,

CAIS, Inc.

By: /s/ Ulysses G. Auger, II 
  ---------------------------------      
    Ulysses G. Auger, II, President
                                    
                                    Agreed to:

                                    Inline Connection Corporation

                                    By:    /s/ David D. Goodman 
                                        ----------------------------------------
                                           David D. Goodman, President

                                             1/26/99
                                    ---------------------------         
                                    Date

                                    Agreed to:

                                           /s/ David D. Goodman 
                                    --------------------------------------------
                                    David D. Goodman, in his individual capacity

                                             1/26/99
                                    ---------------------------         
                                    Date

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