> if multiple addresses are available for a host, the chances are good
> that the paths associated with some of those addresses are significantly
> better, or worse, than others. with IPv4 multihoming, the routing system
> sorts out which path to use. this doesn't work perfectly but at least
> the decision is made in light of some information about the nature and
> current state of those paths. with IPv6 multihoming, the sending host is
> just guessing. it's difficult to believe that this will work well.
That's why you add some feedback-based smarts to the address-order
selection scheme, and overlap the connection attempts (perhaps
separating them by an RTT or so). Given typical distributed apps,
feedback selection based on end-to-end latency will be the right
answer in almost all cases; bandwidth-based feedback can also
potentially be done.
Given how hard it is to get an ISP do to anything special for you
these days, I really can't see a routing-system-based multihoming
actually scale down to, say, individual SOHO networks being
multihomed, while multiple-address-based multihoming doesn't require
anything special out of the ISP's..
- Bill