Subject: issue 58: final

From: Yakov Rekhter <[email-masked]>
Date: Thu, 17 Oct 2002 09:09:10 -0700

58) Deprication of ATOMIC_AGGREGATE
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The following changes reflect the consensus of the WG:

Replace:
    
  5.1.6 ATOMIC_AGGREGATE

   ATOMIC_AGGREGATE is a well-known discretionary attribute.
 
   When a router aggregates several routes for the purpose of
   advertisement to a particular peer, and the AS_PATH of the aggregated
   route excludes at least some of the AS numbers present in the AS_PATH
   of the routes that are aggregated, the aggregated route, when
   advertised to the peer, MUST include the ATOMIC_AGGREGATE attribute.

   A BGP speaker that receives a route with the ATOMIC_AGGREGATE
   attribute MUST NOT remove the attribute from the route when
   propagating it to other speakers.
   
   A BGP speaker that receives a route with the ATOMIC_AGGREGATE
   attribute MUST NOT make any NLRI of that route more specific (as
   defined in 9.1.4) when advertising this route to other BGP speakers.

   A BGP speaker that receives a route with the ATOMIC_AGGREGATE
   attribute needs to be cognizant of the fact that the actual path to
   destinations, as specified in the NLRI of the route, while having the
   loop-free property, may not be the path specified in the AS_PATH
   attribute of the route.
 
with:

  5.1.6 ATOMIC_AGGREGATE

   ATOMIC_AGGREGATE is a well-known discretionary attribute.
         
   When a router aggregates several routes for the purpose of
   advertisement to a particular peer, the AS_PATH of the
   aggregated route normally includes an AS_SET formed from the set of
   AS from which the aggregate was formed.  In many cases the network
   administrator can determine that the aggregate can safely be
   advertised without the AS_SET and not form route loops.
  
   If an aggregate excludes at least some of the AS numbers present in
   the AS_PATH of the routes that are aggregated as a result of
   dropping the AS_SET, the aggregated route, when advertised to the
   peer, SHOULD include the ATOMIC_AGGREGATE attribute.
   
   A BGP speaker that receives a route with the ATOMIC_AGGREGATE
   attribute SHOULD NOT remove the attribute from the route when
   propagating it to other speakers.

   A BGP speaker that receives a route with the ATOMIC_AGGREGATE
   attribute MUST NOT make any NLRI of that route more specific (as
   defined in 9.1.4) when advertising this route to other BGP speakers.

   A BGP speaker that receives a route with the ATOMIC_AGGREGATE
   attribute needs to be cognizant of the fact that the actual path to
   destinations, as specified in the NLRI of the route, while having the
   loop-free property, may not be the path specified in the AS_PATH
   attribute of the route.
 
In 9.1.4 replace:
   
   If a BGP speaker chooses to aggregate, then it MUST add
   ATOMIC_AGGREGATE attribute to the route. A route that carries
   ATOMIC_AGGREGATE attribute can not be de-aggregated. That is, the
   NLRI of this route can not be made more specific. Forwarding along
   such a route does not guarantee that IP packets will actually
   traverse only ASs listed in the AS_PATH attribute of the route.

with:

   If a BGP speaker chooses to aggregate, then it SHOULD either
   include all AS used to form the aggreagate in an AS_SET or add the
   ATOMIC_AGGREGATE attribute to the route.  This attribute is now
   primarily informational.  With the elimination of IP routing
   protocols that do not support classless routing and the elimination
   of router and host implementations that do not support classless
   routing, there is no longer a need to deaggregate.  Routes SHOULD
   NOT be de-aggregated.  A route that carries ATOMIC_AGGREGATE
   attribute in particular MUST NOT be de-aggregated. That is, the NLRI
   of this route can not be made more specific. Forwarding along such
   a route does not guarantee that IP packets will actually traverse
   only ASs listed in the AS_PATH attribute of the route.

Yakov.

---

From: Jeffrey Haas <[email-masked]>
Date: Tue, 22 Oct 2002 09:49:13 -0400

Yakov,

> 58) Deprication of ATOMIC_AGGREGATE

This looks good.

-- 
Jeff Haas 
NextHop Technologies