Subject: SCTP multihoming: initiate connection to non-primary IP address

From: "Kiss, Zoltan (NSN - HU/Budapest)" <[email-masked]>
Date: Tue, 18 May 2010 17:07:57 +0200

Hi,

I have a question about a probable error situation of SCTP multihoming. In my example, we have two peer, both have 2 IP address. Peer A initiate the connection from its primary address Ax to Peer B's primary IP Bx. But Bx is unreachable, and for resiliency purposes it would be better if the A tries to connect to By (B's secondary address). But the question comes, how could A get knowledge of B's secondary address, if the INIT ACK doesn't comes? Is there any best practice to this problem? I have some ideas, but they are mostly just hacks.

Regards,

Zoltán, Kiss

---

From: Vlad Yasevich <[email-masked]>
Date: Tue, 18 May 2010 16:08:24 -0400

Kiss, Zoltan (NSN - HU/Budapest) wrote:
> Hi,
> 
> I have a question about a probable error situation of SCTP multihoming.
> In my example, we have two peer, both have 2 IP address. Peer A initiate
> the connection from its primary address Ax to Peer B's primary IP Bx.
> But Bx is unreachable, and for resiliency purposes it would be better if
> the A tries to connect to By (B's secondary address). But the question
> comes, how could A get knowledge of B's secondary address, if the INIT
> ACK doesn't comes? Is there any best practice to this problem? I have
> some ideas, but they are mostly just hacks.
> 

The answer is sctp_connectx() call.  The existence of By would have to
be known at the same time as Bx.  Peer A would pass both Bx and By as
part of the sctp_connectx() or sctp_sendx() and both addresses can then
be tried.

-vlad