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Re: IPV6 renumbering painless?

  • From: Iljitsch van Beijnum
  • Date: Mon Nov 15 14:49:02 2004 
On 15-nov-04, at 18:03, [email protected] wrote:


only leaf sites use the 32 bit AS numbers. 32 bit AS numbers for
transit ASes are best avoided until everyone has upgraded.



How do we know/tell that "everyone" has upgraded? (As opposed to just

saying "It's been N+4 years now, everybody must have upgraded by
*now*"?)


Well, how do you know that everyone has upgraded from BGP3 to BGP4?




Of course, we *could* always declare "everybody" as "98% of the sites
that

have good contact info in the various Whois databases are ready to go,

the rest know about the issue, and those with bum contact info will get

what they deserve when we deploy" :)



The idea is that the new AS numbers are encoded in new path attributes.
For backward compatibility, a "special" AS number is put in the places
where a 16 bit number is expected. For obvious reasons, there isn't a
corresponding 16 bit AS number for every 32 bit one. So to a 16 bit
router all 32 bit ASes look like a single very big AS. Now this
shouldn't lead to any problems as long as you don't look too hard at
the 16 bit version of the AS path. For leaf sites this shouldn't be a
big deal, but for a transit AS the world is going to look a bit
confusing when observed through 16 bit glasses when 32 bit AS numbers
are becoming common.



So practically, we would have to wait until the big N venders support
this (for N � 2), wait a bit more and then see if we can start
unloading those 32 bit ASes on some poor unexpecting
wannabe-multihomers. :-)