Re: new draft on IPv6 CPE router available for review

["Rémi Denis-Courmont" <rdenis@simphalempin.com>]

Le lundi 7 juillet 2008 21:01:47 Hemant Singh (shemant), vous avez écrit :
> http://www.ietf.org/internet-drafts/draft-wbeebee-ipv6-cpe-router-01.txt

   Note that if the home does not cascade CPE routers, then ULA's are
   not needed for the LAN interfaces, since link-local addresses are
   sufficient for configuration.  After the WAN interface initializes,
   then the LAN interface(s) can acquire global unicast addresses.

This is simply not true. Most (at least quite many) IPv6 applications are 
incapable of using link-local addresses, owing to the peculiar way the socket 
API deals with them. Namely, it requires that the socket address scope ID be 
set. The only way to have fully operational LAN communications is to keep an 
ULA prefix always, regardless of cascading. And it should preferably remain 
present even if the WAN connection has succeeded, so that:
 - pre-existing connections don't break needlessly when the WAN goes up,
 - boxes can easily check if a host is "outside" or "inside",
 - connections don't break if the delegated prefix changes.

-- 
Rémi Denis-Courmont
http://www.remlab.net/