nanog mailing list archives
Re: [Idr] draft-ietf-idr-as0-00 (bgp update destroying transit on redback routers ?)
From: Brian Dickson <brian.peter.dickson () gmail com>
Date: Sat, 3 Dec 2011 12:22:56 -0500
Can anyone familiar with this knob and its usage, answer a question: Would anything break, in terms of use of that knob, if instead of "zeroing" the AGGREGATOR, the local AS (as seen from the outside world, in the case of confederations) were used? Would the functionality of the knob, in reducing updates, be preserved? Would routes be considered malformed or would it trigger any other bad behavior? Perhaps this is a way of resolving the conflict between this knob and the AS0 draft? Brian On Fri, Dec 2, 2011 at 8:12 AM, Daniel Ginsburg <dbg () net-geek org> wrote:
Hi, This is true that "no-aggregator-id" knob zeroes out the AGGREGATOR attribute. The knob, as far as I was able to find out, dates back to gated and there's a reason why it was introduced - it helps to avoid unnecessary updates. Assume that an aggregate route is generated by two (or more) speakers in the network. These two aggregates differ only in AGGREGATOR attribute. One of the aggregates is preferred within the network (due to IGP metric, for instance, or any other reasons) and is announced out. Now if something changes within the network and the other instance of the aggregate becomes preferred, the network has to issue an outward update different from the previous only in AGGREGATOR attribute, which is completely superfluous. If the network employs the "no-aggregator-id" knob to zero out the AGGREGATOR attribute, both instances of the aggregate route are completely equivalent, and no redundant outward updates have to be send if one instance becomes better than another due to some internal event, which nobody in the Internet cares about. In other words, the "no-aggregator-id" knob has valid operational reasons to be used. And, IMHO, the draft-ietf-idr-as0-00 should not prohibit AS0 in AGGREGATOR attribute. On 02.12.2011, at 1:56, Jeff Tantsura wrote:Hi, Let me take it over from now on, I'm the IP Routing/MPLS Product Manager at Ericsson responsible for all routing protocols. There's nothing wrong in checking ASN in AGGREGATOR, we don't really want see ASN 0 anywhere, that's how draft-wkumari-idr-as0 (draft-ietf-idr-as0-00) came into the worlds. To my knowledge - the only vendor which allows changing ASN in AGGREGATOR is Juniper, see "no-aggregator-id", in the past I've tried to talk to Yakov about it, without any results though. So for those who have it configured - please rethink whether you really need it. As for SEOS - understanding that this badly affects our customers and not having draft-ietf-idr-error-handling fully implemented yet, we will temporarily disable this check in our code. Patch will be made available. Please contact me for any further clarifications. Regards, Jeff P.S. Warren has recently included AGGREGATOR in the draft, please see 2. Behavior This document specifies that a BGP speaker MUST NOT originate or propagate a route with an AS number of zero. If a BGP speaker receives a route which has an AS number of zero in the AS_PATH (or AS4_PATH) attribute, it SHOULD be logged and treated as a WITHDRAW. This same behavior applies to routes containing zero as the Aggregator or AS4 Aggregator._______________________________________________ Idr mailing list Idr () ietf org https://www.ietf.org/mailman/listinfo/idr
Current thread:
- Re: bgp update destroying transit on redback routers ?, (continued)
- Re: bgp update destroying transit on redback routers ? Christopher Morrow (Dec 01)
- Re: bgp update destroying transit on redback routers ? Warren Kumari (Dec 01)
- RE: bgp update destroying transit on redback routers ? Jeff Tantsura (Dec 01)
- Re: bgp update destroying transit on redback routers ? Rob Shakir (Dec 01)
- Re: bgp update destroying transit on redback routers ? Randy Bush (Dec 02)
- Re: bgp update destroying transit on redback routers ? Igor Ybema (Dec 01)
- draft-ietf-idr-as0-00 (bgp update destroying transit on redback routers ?) Daniel Ginsburg (Dec 02)
- RE: draft-ietf-idr-as0-00 (bgp update destroying transit on redback routers ?) Jeff Tantsura (Dec 03)
- Re: [Idr] draft-ietf-idr-as0-00 (bgp update destroying transit on redback routers ?) Brian Dickson (Dec 03)
- Re: bgp update destroying transit on redback routers ? Alexandre Snarskii (Dec 02)
- Re: bgp update destroying transit on redback routers ? Christopher Morrow (Dec 02)
- RE: bgp update destroying transit on redback routers ? Jeff Tantsura (Dec 02)
- Re: bgp update destroying transit on redback routers ? Olivier Benghozi (Dec 22)
- RE: bgp update destroying transit on redback routers ? Jeff Tantsura (Dec 22)