RE: CPE router acting as host on its WAN interface (RE: draft-ietf-v6ops-ipv6-cpe-router-03.txt WGLC)

["Hemant Singh (shemant)" <shemant@cisco.com>]

>-----Original Message-----
>From: Templin, Fred L [mailto:Fred.L.Templin@boeing.com] 
>Sent: Tuesday, January 05, 2010 12:00 PM

>The IsRouter discussion was on this list (v6ops); not
>the 6man list. Maybe you were talking about a different
>discussion on the 6man list?

No.  I am talking about "Stub Router Advertisements in IPv6
NeighborDiscovery" that was being discussed in the 6man mailer between
you, Bob Hinden and Thomas Narten.  One example of your IsRouter
discussion is an email with following date, time, etc. to the 6man list
of ipv6@ietf.org.

"Sent: Tuesday, November 24, 2009 11:37 AM"


>The final sentence of Appendix D also says:

>  "In these cases, a subsequent Neighbor
>   Advertisement or Router Advertisement message will set
>   the correct IsRouter value."

>but if the CPE will not send any RA messages over its
>WAN interface then the NA is the only other option for
>setting the correct IsRouter value.

Yes, the CE Rtr is not expected to send any RA over its WAN interface
upstream to the SP.  So what's the concern if the SP router upstream of
the CE Rtr has an incorrect IsRouter value temporarily?  When the CE Rtr
is a requesting router for delegated prefix, the SP router knows the CE
Rtr is a router.  Note the CE Rtr is both a host and a router.

>If a provider router garbage-collects a FIB entry because
>it sees that IsRouter in the nexthop nbr cache entry is
>FALSE, the FIB entry is gone and there is no route to the
>CE router's prefixes. That is what I am meaning to say
>regarding interoperability issues and circumstances.
>First, the delegating router need not be co-resident on
>the provider router that sends RA to the CE router; it
>could be behind a chain of relays instead. Second, just
>because the delegating router (and I guess also any
>relays in the chain) come to know that the CE router is
>a requesting router does not necessarily mean that the
>provider router will know enough to reach into its kernel
>and set the IsRouter flag in the nbr cache entry to TRUE.
>Or, maybe that behavior is specified somewhere that I
>didn't see?

The FIB does NOT include the Neighbor cache, so why are you discussing
"nbr cache entry"? Further, since DHCPv6 (used for requesting a
delegated prefix) travels over a link-local address, the CE Rtr will see
only the SP router that is in the CE Rtr link-local domain.  Therefore
any discussion of relay and chains is moot.  Sorry, I still don't see a
clear problem definition from you.

Hemant