Subject: [Tsvwg] SCTP multi-homing

From: devayya <[email-masked]>
Date: Tue, 28 Mar 2006 17:50:05 +0530

Hi,

In case of SCTP multi-homing, if the Heartbeat is disabled on all the 
paths and there is no traffic running on an of the paths, is there 
anyway by which we can know the destination path status?
Does anybody have any test set up plan / procedure for SCTP multi-homing ?

Thanks and regards,
devayya

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Tue, 28 Mar 2006 05:31:12 -0700

devayya,

devayya wrote:                                 (Tue, 28 Mar 2006 17:50:05)
> anyway by which we can know the destination path status?

A good reason why not to disable HEARTBEAT.

> Does anybody have any test set up plan / procedure for SCTP multi-homing ?

There are some multi-homing tests in ETSI TS 102 369.

(These are test purposes, not ATS, but creating an ATS from them
is fairly straightforward.  I have implemented most of them.)

I think Randall also has some testing scenarios from the interops.

--brian

-- 
Brian F. G. Bidulock
[email-masked]
http://www.openss7.org/

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From: Michael Tuexen <[email-masked]>
Date: Tue, 28 Mar 2006 17:17:58 +0200

Dear all,

see my comments in-line.

Best regards
Michael

> A good reason why not to disable HEARTBEAT.
If you do not send anything, how could you know. So let HEARTBEATS been
turned on.
> is fairly straightforward.  I have implemented most of them.)
All of them are implemented under BSD license using the SCTP test  
tool (stt).
The tool and the tests are available from
http://sctp.fh-muenster.de

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From: Mark Butler <[email-masked]>
Date: Tue, 28 Mar 2006 08:27:00 -0700

> anyway by which we can know the destination path status?

No.  That is what heartbeats are for.

The exception might be if your routing setup is sufficiently 
sophisticated that a route is withdrawn for bad paths. On Internet 
scales, that normally takes tens of seconds, and of course it requires 
the SCTP endpoints to run a routing protocol like OSPF, a complexity 
SCTP normally nicely avoids.

> Does anybody have any test set up plan / procedure for SCTP 

One thing to keep in mind is that in general you will need to establish 
static routes to keep the paths to independent peer addresses 
independent of each other.

 - Mark B.

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From: Mark Butler <[email-masked]>
Date: Tue, 28 Mar 2006 09:07:29 -0700

Mark Butler wrote:

> One thing to keep in mind is that in general you will need to 
> establish static routes to keep the paths to independent peer 
> addresses independent of each other.

A couple more things:

    1. For a route withdrawal to be immediately effective at the SCTP 
layer, the SCTP implementation must be smart enough to switch paths 
immediately when packets get rejected by the IP layer for lack of route 
(or interface down, etc).

    2. Dynamic route updates and static routes do not mix very well, so 
if you want outbound path independence with dynamic routes, and the 
routes are not naturally independent due to network topology, the 
independence will have to be accomplished via the routing protocol 
configuration instead.

 Unfortunately, common routing protocols are not designed to provide 
independent routes to a destination, but rather to provide the preferred 
(usually shortest) route to a destination.  So if you want guaranteed 
path independence, you either run parallel networks, or make sure that 
none of the paths share the same transit AS.   Source address routing is 
an easy way to accomplish the latter, if your SCTP implementation 
supports it.

 - Mark B.