Proposed change at the Interconnect

skw skw
Tue Nov 10 09:16:37 UTC 1992

This change will take place with today's update.  
  --Steve Widmayer

 >Date: Mon, 2 Nov 92 17:26:04 EST
 >From: epg at
 >To: regional-techs at
 >Subject: Proposed change at the Interconnect
 >Cc: epg at
 >The T1 backbone and the T3 backbone have provided a backup path to
 >mid-level networks which peered with both backbones. 
 >                                x
 >                               / \
 >                              /   \
 >                     +------+      +------+
 >                     |      |      |      |
 >                     |  T1  |------| T3   |
 >                     |      |      |      |
 >                     +------+      +------+
 >                    /     \          /     \
 >                   /       \        /       \
 >                 a          \      /         \
 >                             \ y  /           b
 >This was done by announcing all known networks from one backbone
 >to the other via the interconnection between the two. One of the
 >benefits of doing this was that it provided a transition from the
 >T1 backbone to the deployment of the T3 backbone.
 >Now that almost all of the peers that were known to the T1 are
 >also known directly to the T3 and the T3 has implemented 
 >backup plans in addition to the T1 backbone, we would like to
 >stop announcing the networks associated with dual homed peers
 >from the T3 to the T1. This means that T1 only networks will
 >no longer have a backup path through the T3 if a dual homed site
 >loses its connectivity to the T1 backbone.
 >In this proposed configuration, at the interconnection, the
 >T1 will announce networks a, x and y to the T3.  At the interconnection,
 >the T3 will announce network b to the T1. This plan will have the
 >following affect:
 >1)  if the connection between x and the T1 breaks,
 >b will reach x via the T3
 >y will reach x via the T3
 >a will find x unreachable 
 >2)  if the connection between x and the T3 breaks,
 >b will reach x via the interconnect to the T1 
 >y will reach x via the interconnect with the return path via the T1
 >a will reach x via the T1
 >CA*net and EASInet are the only peers which remain T1 only.  We have
 >contacted them previously concerning this proposal and they are
 >aware of the proposed change.  We are also in the process of working with
 >those two organizations to convert them to the T3 backbone.
 >We would like to make this configuration change by the end of this
 >week, November 6, 1992. This step will help to maintain the T1
 >backbone until the remaining peers have transitioned to the T3
 >by reducing the amount of routing information that the RTs need
 >to assimilate.  It is also another step in preparation to
 >the eventual dismantlement of the T1 backbone.
 >If you have any questions concerning this proposal
 >please notify us as soon as possible.
 >Thank you.
 >             --Elise

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