See comments in-line below: -----Original Message----- From: Thomas Narten [mailto:nar...@us.ibm.com] Sent: Wednesday, May 06, 2009 1:28 PM To: JINMEI Tatuya / 神明達哉 Cc: Hemant Singh (shemant); Wes Beebee (wbeebee); erik.nordm...@sun.com; ipv6@ietf.org Subject: Re: comments on draft-ietf-6man-ipv6-subnet-model-03 OK, how about the following text
> OLD: > > 2. Note that Redirects cannot signal that an address is off-link. > In section 8.1 of [RFC4861], a Redirect message is silently > discarded if it does not have an IP source address that is the > same as the current first-hop router for the specified ICMP > Destination Address. An ICMP Destination Address on the same > link would have no current first-hop router. Any Redirect > message received could not have an IP source address that is the > same as the current (null) first-hop router, so the Redirect MUST > be dropped. > > NEW: > > 2. Note that Redirect Messages do not contain sufficient > information to signal that an address is off-link. Rather, they > indicate a preferred next-hop that is a more appropriate > choice to use than the originator of the Redirect. That > alternate next-hop may be the destination itself (in which case > packets would flow directly to a neighbor), or a router closer > the destination. Note, however, that the redirect message > itself does not contain sufficient information to distinguish > these cases. But that does not matter, because the receiver of > such a message does the same in either case, updating its > Neighbor Cache as defined in Section 8.1 of [RFC4861]. The core issue is not whether the host realizes that the Redirect is signalling an address is off-link (which obviously can't be done), but rather whether a router could be designed with a specially-crafted Redirect that will cause the host to behave as if the destination is off-link (which is an even stronger case). The answer is that you CAN craft a Redirect in such a way, by simply including the router as the next-hop (instead of the neighbor host which the node had as a next-hop). However, hosts will drop such a packet and not update their tables. The reason for the drop is that "a Redirect message is silently discarded if it does not have an IP source address that is the same as the current first-hop router for the specified ICMP Destination Address". - Wes -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
