Wes & Hemant, Can we walk through the situation of hosts without routers where you suggest a possible issue?
HostA ----(link)---- HostB HostA: 2002:db8:100::1234/64 2002:db8:200::1234/64 HostB: 2002:db8:100::9999/64 Are we suggesting HostA may src from 2002:db8:200::1234 to 2002:db8:100::9999, ie, we are forgoing source-address selection and are overriding this behaviour? Assuming that is the case, and assuming HostB did in fact populate a Neighbour Cache entry with 2002:db8:200::1234 - STALE, I cannot see how this would affect HostB's next-hop/on-link determination. According to the current text in RFC4861 HostB would perform the following on the first packet to send to 2002:db8:200::1234: 1) Check destination cache (empty, never seen this destination before) 2) Check Prefix List for on-link determination (off-link) - 2002:db8:200::1234 is not in the Prefix List 3) If off-link, select a router from Default Router List and determine next-hop IP (no default routers) --end in our example as there are no routers-- 4) Consult Neighbour Cache for link-layer address of next-hop, invoke Address Resolution if needed 5) Cache result in destination cache I understand Neighbour Cache is not consulted for next-hop/on-link determination, and Destination Cache is updated with the result of the Prefix-List lookup (next-hop determination). So while there is a STALE entry in the Neighbour Cache, it is never queried. Similar to the case of a router, I think we would need to update a host's equivalent (the Prefix List) to affect forwarding. It would be good to better understand the scenario you are seeing between host and host. Best Regards, -David -----Original Message----- From: Wes Beebee (wbeebee) [mailto:[EMAIL PROTECTED] Sent: Friday, 27 June 2008 12:29 AM To: Wojciech Dec (wdec); Brian Haberman; ipv6@ietf.org Cc: MILES DAVID; Bob Hinden Subject: RE: 6MAN WG Last Call:draft-ietf-6man-ipv6-subnet-model-00.txt This rule derives directly from the Terminology section of RFC 4861 (definition of on-link). Note that the presence of a bogus entry causes no harm (the routing table takes precedence over the ND cache in this case). However, the removal of the rule DOES cause harm in the case of communication without routers. Therefore, we currently see no reason to change the text. - Wes & Hemant -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Wojciech Dec (wdec) Sent: Thursday, June 26, 2008 10:05 AM To: Brian Haberman; ipv6@ietf.org Cc: MILES DAVID; Bob Hinden Subject: RE: 6MAN WG Last Call:draft-ietf-6man-ipv6-subnet-model-00.txt Based on a recent thread (http://www.ops.ietf.org/lists/v6ops/v6ops.2008/msg00896.html) the following paragraph from the draft appears to warrant some more thought if not outright a revision " In addition to the Prefix List, individual addresses are on-link if they are the target of a Redirect Message indicating on-link, or the source of a valid Neighbor Solicitation or Neighbor Advertisement message. Note that Redirect Messages can also indicate an address is off-link. Individual address entries can be expired by the Neighbor Unreachability Detection mechanism." Using unconditionally the source address of a neighbour solicitation or NA to determine on-link would indeed appear to be undesirable, unless the intent is allow some direct host-host cross subnet/prefix communication without a router involved at any stage (this is not a good idea IMO). A constraint could be introduced such as: A host only learns on-link addresses from the source of NS and NA messages iff it already has an on-link prefix that would cover that address. Learning from Redirect messages would continue to be allowed. My 2c. -Woj. > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf > Of Brian Haberman > Sent: 26 June 2008 14:17 > To: ipv6@ietf.org > Cc: Bob Hinden > Subject: 6MAN WG Last Call:draft-ietf-6man-ipv6-subnet-model-00.txt > > All, > This message starts a 3-week 6MAN Working Group Last Call on > advancing: > > Title : IPv6 Subnet Model: the Relationship between > Links and Subnet Prefixes > Author(s) : H. Singh, et al. > Filename : draft-ietf-6man-ipv6-subnet-model-00.txt > Pages : 8 > Date : 2008-05-08 > > as a Proposed Standard. Substantive comments and statements of > support for advancing this document should be directed to the mailing > list. > Editorial suggestions can be sent to the document editor. > This last call will end on July 10, 2008. > > Regards, > Brian & Bob > 6MAN co-chairs > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- > -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 -------------------------------------------------------------------- -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
