Re: [NAILS REQUESTED PREVIEW]: Re: SCTP failover

From: Janardhan Iyengar <iyengar@mail.eecis.udel.edu>
Date: Fri Feb 11 2005 - 16:20:03 EST

('binary' encoding is not supported, stored as-is) ('binary' encoding is not supported, stored as-is) Hi David,

> >>I need to correct my former post. Assuming a steady flow
> >>of data chunks, the switch-over with Ulticom's stack will
> >>actually be in a fraction of a second since the FR will
> >>notice the problem long before the RTO.
> >
> > Hmm... I think that is getting too aggressive. This behavior could
> > cause reordering and induce false fast retransmits. Why would you do that?
>
> I don't like to wait! :-) It seems to work well.

SCTP (and TCP) increase their cwnds until a sender observes loss. An SCTP
sender *has* to see loss to cut its cwnd. Even at equilibrium, an SCTP
sender will keep seeing loss. Which means that your sender will keep
moving back and forth among the different destinations all the time.

Switching over to an alternate on an FR may give you really good failover,
but will likely hurt performance when there's no failure (the common
case). Optimizing for the common case makes sense.

regards,
jana

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Janardhan R. Iyengar http://www.cis.udel.edu/~iyengar
Protocol Engineering Lab -- CIS -- University Of Delaware
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Received on Fri Feb 11 16:32:02 2005