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RE: ISP failures and site multihoming [Re: Enforcing unreachability of site local addresses]
I am on multi6 and just listen and send clarification questions to
various participants. But a short comment here.
> Has the end-to-end principle failed to teach us anything?
> Reliability begins and ends in the end hosts. If each host is
> connected over two service providers there are four possible
> paths the hosts can switch between on a per-packet basis.
> Then the only problem becomes detecting failure. The end
> hosts are in an excellent position to do this without having
> to generate keepalive messages; a well designed protocol
> could switch to an alternate path within a few round trip
> times when a path failure occurs.
I agree with the above view and much of the problem can be solved by
intelligent code and configuration being done by the end system for new
IPv6 development and some existing network application infrastructure
that is a direct port from IPv4 that has been ported and deployed. SCTP
is a clear winner for us here over TCP and it's a new API so we could go
there. But more importantly the transition to this requires code on the
end systems from suppliers, and then either apps change or shims are
built on the end systems. Doing it with TCP is possible till SCTP is
more dominant. This is solving the problem at layer 7 and 4. And that
means we need new platform code releases and development to make it
happen. Which is fine but will take time.
Layer 1 and 3 may be able to do something too but that will take time
and require new code and platform releases.
I think we need to first pick which way we want to specify this or both
and provide technical spec on what each mean.
It is really transparent to IPv6 but IPv6 has a better chance of getting
> Multi6 has been gravitating towards multi-address multihoming
> solutions for a while now, but unfortunately it seems
> impossible to move foward.
Hmmm. At some point this needs to get done folks. Not sure what will
cause it, but I believe it may be external forces resolve it for us.
P.S. Mutli6 should not MUST SCTP as Diameter tried (well was forced)
that and all the Diameter products shipping are doing it with TCP and
same for some other things like RDMA. But Multi6 could do the community
a big favor by stressing that SCTP really helps this problem within its
inherent failover capabilities via the network association for the