Subject: issue 63

From: Yakov Rekhter <[email-masked]>
Date: Fri, 18 Oct 2002 10:06:15 -0700

63) Clarify MED Removal Text
----------------------------------------------------------------------------
Following suggestion from Curtis, here are the changes:

In 5.1.4 replace:

   An implementation MAY also (based on local configuration) alter the
   value of the MULTI_EXIT_DISC attribute received over EBGP.
   If it does so, it shall do so prior to determining the degree of
   preference of the route and performing route selection (decision
   process phases 1 and 2).

with:

   An implementation MAY also (based on local configuration) alter the
   value of the MULTI_EXIT_DISC attribute received over EBGP.
   This MAY be done prior to determining the degree of preference
   of the route and performing route selection (decision process phases
   1 and 2). See section 9.1.2.2 for necessary restricts on this.
      
In 9.1.2.2 replace:

   Similarly, neighborAS(n) is a function which returns the neighbor
   AS from which the route was received.
      
with:

   Similarly, neighborAS(n) is a function which returns the
   neighbor AS from which the route was received.  If the route is  
   learned via IBGP, it is the neighbor AS from which the other
   IBGP speaker learned the route, not the local AS.

   If a MULTI_EXIT_DISC attribute is removed before redistributing
   a route into IBGP, the MULTI_EXIT_DISC attribute may only be      
   considered in the comparison of EBGP learned routes, them
   removed, then the remaining EBGP learned route may be compared    
   to the remaining IBGP learned routes, without considering the    
   MULTI_EXIT_DISC attribute for those EBGP learned routes whose
   MULTI_EXIT_DISC will be dropped before advertising to IBGP.
   Including the MULTI_EXIT_DISC of an EBGP learned route in the
   comparison with an IBGP learned route, then dropping the
   MULTI_EXIT_DISC and advertising the route has been proven to
   cause route loops.

In the absence of objections I'll make the above changes.

Yakov.