Re: Evaluation: draft-ietf-ipngwg-ipv6-anycast-analysis

[Randy Bush <randy@psg.com>]

> Anycast is supplying the ability to address a topologically close
> instantiation of a service in a transparent (to the host) way. It
> makes no guarantees that any packet sent to the given anycast
> address will arrive at the same node.
> 
> Many of the problems seem to arise from stateful protocol uses of
> anycast. In my opinion the reason they don't work is because they
> are misusing the service supplied by anycast.
> 
> This draft doesn't seem to be stating that directly.
> 
> A solution to almost all the problems seems to be to send a
> packet to the anycast server, acquire it's unicast address and use
> that from then on (i.e., resolve the anycast address using the
> routing infrastructure). This strikes me as a proper use of the
> anycast service.

glad you like it.  but folk have been successfully using anycast for
more long-lived flows for at least a decade of which i am aware.  we
can pretend it is not happening and does not work, or we can document
it and warn of its dangers.

>> o A provider-independent IPv4 address prefix is allocated from an RIR.
> no need for it to be provider-independent. Can even be
> RFC1918 w/in a domain

or it could be acquired from one's provider

>> o A host route, or a route that covers the address prefix is advertised
>>   from all of the locations.
> maybe. A /32 is injected into the IGP by the router(s)
> adjacent to the host with the anycast address

it may not be igp

randy