[ppml] Proposed Policy: 4-Byte AS Number Policy Proposal

Geoff Huston gih at apnic.net
Wed Dec 14 15:03:56 EST 2005

At 09:37 PM 14/12/2005, Michael.Dillon at btradianz.com wrote:
> > Again, not so. I'll say it again: Please _read_ these references, as
> > are intended to describe the transition situation in as comprehensive
> > manner as possible.
>That's the problem, they are too darn comprehensive.
>Why didn't you just say that people can continue to run
>their existing BGP code and they will see any large AS
>numbers as a special ASN 23456. People running the new code
>will map to and from ASN 23456.

(we are probably off in the weeds here as this discussion on the cited 
references is now heading well beyond the attributes of the proposal 
itself, so I'll respond on the list this time, but followup 1:1 if required 
- geoff)

The cited references describe how the mechanism operates, and, in 
particular describe how the combination of auto-translation and 
auto-tunnelling at the boundaries of the 2-byte and 4-byte AS realms 
jointly preserve the essential attributes of the AS_PATH attribute in the 
context of inter-domain Routing: namely preservation of the inter-AS path 
metric and loop detection. For many folk reading those articles the 
description of how this is achieved is as, or more, important as the 
description of the outcome of these mechanisms.



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