[Cluster-devel] SCTP versus OpenAIS/corosync time-outs

[Fabio M. Di Nitto]

Lars Marowsky-Bree wrote:
> On 2009-11-02T08:41:43, Christine Caulfield <ccaulfie at redhat.com> wrote:
> 
> A quite different trick for redundant networking would be to assign
> static addresses to lo:X and run OSPF over all links, and having DLM
> connect to the static IPs. That's quite trivial to setup, give us
> "resilient" TCP (w/o needing to mess with SCTP, bonding, or anything).
> 
> Comments?
> 

OSPF timings to converge networks can be very long as it involves link
UP/DOWN events, flapping protection and so on and so forth... IMHO,
while the idea is valid, it introduces a new whole set of timeouts to
take into account.

IMHO it´s a lot simpler to do something like this:

monitor the links status, if UP assign a static route with different
metric so that one link is always preferred over another. On link DOWN
event, remove the static route, flush the route cache (speed up kernel
look ups into the new route with higher or lower metric), and traffic
will flow very quickly again on the new link.

I use a very similar setup using a patched version of vtun (we clearly
don´t want or need that), and the response time is in the order of a
couple of seconds (it could be a lot lower with proper trimming to the
setup).

Fabio