Date: Mon, 15 Oct 2001 11:55:27 +0200 (CEST) From: Iljitsch van Beijnum <iljitsch@muada.com>
I'm looking for information about the way networks use communities in BGP.
It seems that many of the larger networks only use communities to supply their customers with a mechanism to adjust the local preference to indicate which connection is preferred when a customer connects over more than one link (something that can also be done with the MED).
Remember that local-pref has higher priority than as-path length; MED is the lowest priority before router ID. For instance, I match "_asnthatIdontlike_" and penalize local-pref to [try to] avoid routing traffic over an ASN that I think has poor performance. If I penalize AS65000, then me 3549 65500 65432 65432 65432 65123 will be preferred over me 6347 65000 65123 This is one reason that redistributing one's upstream routes via BGP can be bad despite as-path length: If someone uses local-pref, it's quite conceivable that one will take the erroneous path that some edge idiot[1] leaked into the table. [1] I'm an edge-dweller. I can insult them. Note, however, that upstreams _should_ filter their downstreams to prevent improper adverts... but the root of the problem is the one at the edge. [ snip ]
And how about things like congestion?
How do you mean?
Is there any need for more "well known" communities?
I wish that providers would set a community indicating route ingress. I know, for instance, that GBLX does this... but their system with hundreds of communites leaves some to be desired, IMHO. I'd like to see providers tag "route learned in this region" at various granularity levels. As for providers listening to communities, I like selective as-path padding... I'd have to dig up the thread, but this has been discussed in the past few months. Eddy --------------------------------------------------------------------------- Brotsman & Dreger, Inc. - EverQuick Internet Division Phone: +1 (316) 794-8922 Wichita/(Inter)national Phone: +1 (785) 865-5885 Lawrence --------------------------------------------------------------------------- Date: Mon, 21 May 2001 11:23:58 +0000 (GMT) From: A Trap <blacklist@brics.com> To: blacklist@brics.com Subject: Please ignore this portion of my mail signature. These last few lines are a trap for address-harvesting spambots. Do NOT send mail to <blacklist@brics.com>, or you are likely to be blocked.