On Jul 4, 2011, at 3:16 PM, Karl Auer wrote: > On Mon, 2011-07-04 at 22:12 +0930, Mark Smith wrote: >> If every router supports the subnet anycast address, because it is a >> mandated requirement, you can develop and deploy something that relies >> on it. If the availability is limited, you end up duplicating the same >> mechanism some other way at the cost of additional effort, or don't >> bother at all because those additional costs are too high. > > For situations apparently needing the subnet router anycast address, > there is the all-routers-on-link multicast address. Not that it would > normally be needed, because any node on the link has (or can cheaply > build) a list of all routers on the link by just watching the RAs, > something it has to do anyway. A node can then choose a router at > random, or any router based on any criteria it likes. Alternatively an > application can ping the all-routers-on-link multicast address and build > a list of responders. There is no need for the subnet router anycast > address.
A residential gateway router is not going to be able to do this for a variety of reasons. - Mark > > The subnet anycast addresses are reserved but not necessarily used. Any > node actually sending to one must therefore first acquire information > about which one to send to. The source of that information could just as > well supply any address. On the other side of the equation, an > application wanting to use one of the reserved addresses must somehow > publish information about which one it is using. Again, that could just > as well convey information about any address. There is no need for the > subnet anycast addresses to be reserved. > > Seriously, I'm not being bloody-minded. I simply cannot see a good > reason for either of these two reserved address sets. If someone can > provide any, I will immediately retract everything I have said and > maintain the opposite :-) > > Regards, K. > > -- > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > Karl Auer (ka...@biplane.com.au) +61-2-64957160 (h) > http://www.biplane.com.au/kauer/ +61-428-957160 (mob) > > GPG fingerprint: DA41 51B1 1481 16E1 F7E2 B2E9 3007 14ED 5736 F687 > Old fingerprint: B386 7819 B227 2961 8301 C5A9 2EBC 754B CD97 0156 > -------------------------------------------------------------------- > 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 --------------------------------------------------------------------
