Re: subnet router anycast

[Mark Smith <[e-mail]>]

Hi,


On Sun, 03 Jul 2011 23:50:25 +0200
Roland Bless <[e-mail]> wrote:

> Hi,
> 
> On 03.07.2011 19:03, Karl Auer wrote:
> > Which RFCs (or other sources) describe how IPv6 subnet anycast *works*?
> > In particular how it works when there are multiple routers in a single
> > subnet?
> 
> That's a good question. I was also looking for that. It's distributed
> across various RFCs:
> -----------------------------------------------------------------------

To make a higher level observation, I don't think it is any different
to the operation of host anycast, as the destination address in the
packet matches one of the router's own addresses, so the router would
process the packet in "host mode" rather than "forwarding mode". 

I suspect it was inspired by Appletalk's assignment of node ID zero on
each cable range to attached routers. That in turn was used by the Name
Binding Protocol for mapping host names to DDP addresses. Since
the goals of Multicast DNS and DNS-based Service Discovery are similar
to NBP, it may be possible that IPv6 router anycast could be used in a
similar way with mDNS and DNS-SD. 

Here's an ID on the topic of NBP/mDNS/DNS-SD - 

http://tools.ietf.org/html/draft-cheshire-dnsext-nbp-10

If you're interested in the Appletalk spec that talks about DDP and
NBP, do an Internet search for "Inside Appletalk". It used to be a
freely downloadable PDF on Apple's website, but it seems to have
disappeared.

Regards,
Mark.