nanog mailing list archives
Re: BGP prefix filter list
From: William Herrin <bill () herrin us>
Date: Thu, 30 May 2019 10:42:17 -0700
On Thu, May 30, 2019 at 10:11 AM Mel Beckman <mel () beckman org> wrote:Are your sure about your Error #2, where you say "Prefixes from the
same AS are not required to have direct connectivity to each other and many do not."?
From BGP definitions: The AS represents a connected group of one or more blocks of IP
addresses, called IP prefixes, that have been assigned to that organization and provides a single routing policy to systems outside the AS.
From -what- BGP definitions? This one?
https://www.scribd.com/document/202454953/Computer-Networking-Definitions Lots of things get claimed in books and CS courses that are neither reflected in the standards nor match universal practice. Heck, most networking courses still teach class A, B and C... definitions which were explicitly invalidated a quarter of a century ago. Even where authors are knowledgeable, they're constrained to present approximate explanations lest the common use get lost in the minutiae. When you want to act on the knowledge in an unusual way, you do not have that luxury. The experts in the IRTF Routing Research Group spent something like 6 years trying to find a way to filter the BGP RIB in the middle without damaging the Internet. They came up with zip. A big zero. They all but proved that it's impossible to build a routing protocol that aggregates anything anywhere but at the edges while still obeying the most basic policy constraints like not stealing transit. Forget getting BGP to do it, they couldn't come up with an entirely new protocol that did better. Regards, Bill Herrin -- William Herrin bill () herrin us https://bill.herrin.us/
Current thread:
- Re: BGP prefix filter list, (continued)
- Re: BGP prefix filter list Ross Tajvar (May 22)
- Re: BGP prefix filter list Sabri Berisha (May 24)
- Re: BGP prefix filter list Mike Hammett (May 24)
- Re: BGP prefix filter list William Herrin (May 24)
- Re: BGP prefix filter list Blake Hudson (May 24)
- Re: BGP prefix filter list William Herrin (May 24)
- Re: BGP prefix filter list James Jun (May 25)
- Re: BGP prefix filter list Robert Blayzor (May 30)
- Re: BGP prefix filter list William Herrin (May 30)
- Re: BGP prefix filter list Mel Beckman (May 30)
- Re: BGP prefix filter list William Herrin (May 30)
- Re: BGP prefix filter list Mel Beckman (May 30)
- Re: BGP prefix filter list William Herrin (May 30)
- Re: BGP prefix filter list Mel Beckman (May 30)
- Re: BGP prefix filter list Thomas Bellman (May 30)
- Re: BGP prefix filter list Mel Beckman (May 30)
- Re: BGP prefix filter list Valdis Klētnieks (May 30)
- Re: BGP prefix filter list Mel Beckman (May 30)
- Re: BGP prefix filter list Thomas Bellman (May 31)
- Re: BGP prefix filter list Valdis Klētnieks (May 30)
- Re: BGP prefix filter list Matt Corallo (May 30)