Subject: [Idr] RFC 4360 clarification (BGP Extended Communities Attribute)

From: <[email-masked]>
Date: Fri, 31 Jul 2009 01:14:55 +0200

Hi all,

We have a clarification question regarding RFC 4360. Section "6.
Operations" states that "If a route has a non-transitivity extended
community, then before advertising the route across the Autonomous
System boundary the community SHOULD be removed from the route."

Is it compliant with the specification to:
-a- set / add, on the outbound policy of an eBGP session, a non
transitive extended community?
-b- expect that the eBGP peer will not remove it to enforce the
non-transitivity?

It seems to us that this is compliant: 
-a- seems to be inlined with the operation of well know communities
defined in RFC 1997 where the advertisement restrictions applies when
BGP receive a route with this community, not when it advertise it.
-b- RFC 4360 does not ask the eBGP to enforce the non-transitivity (and
besides, non-transivity is a SHOULD, not a MUST)

- Could you please correct or confirm this?
- If your BGP implementation removes a non-transitive community received
over an eBGP session, could you please tell us? (either privately or on
the mailing list).

Thanks,
Regards,
Bruno