Subject: [Sigtran] multi-homing association

From: devayya <[email-masked]>
Date: Fri, 05 May 2006 17:29:29 +0530

Hi,

I have question, Is it possible or mandatory for the upper layer to know 
that the SCTP endpoints(source and destination) are multi-homed? and 
also the list of destination ip address available with the SCTP 
multi-homed destination?

Consider if the SCTP layer is multi-homed(source and peer end) and the 
upper layer knows only about a single address, through which the upper 
layer asks the SCTP to initiate a association. Suppose during this 
initiation if the peer end address through which initiation is 
happening, is down. Is there any approach where the upper layer knows 
the list of multihomed destination ip addresses, and it tries to initate 
the through the other destination ip addresses?
If not possible,  is it that the association between these to endpoints 
will never come up untill the known destination ip address comes up?

Please clarify...

Thanks and regards,
devayya

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From: Michael Tuexen <[email-masked]>
Date: Fri, 5 May 2006 14:25:00 +0200

Hi,

see my comments in-line.

Best regards
Michael

On May 5, 2006, at 1:59 PM, devayya wrote:

> Hi,
>
> I have question, Is it possible or mandatory for the upper layer to  
> know that the SCTP endpoints(source and destination) are multi- 
> homed? and also the list of destination ip address available with  
> the SCTP multi-homed destination?
The interface between SCTP and its upper layer is not specified in an  
RFC. However, there
is an ID describing the socket API which is implemented by some SCTP  
stacks like
the one in *BSD, Linux (LKSCTP), and Solaris.
>
> Consider if the SCTP layer is multi-homed(source and peer end) and  
> the upper layer knows only about a single address, through which  
> the upper layer asks the SCTP to initiate a association. Suppose  
> during this initiation if the peer end address through which  
> initiation is happening, is down. Is there any approach where the  
> upper layer knows the list of multihomed destination ip addresses,  
> and it tries to initate the through the other destination ip  
> addresses?
If the initiating endpoint knows more than one address of the peer,  
it can use the
connectx() or sendx() call to make use of this knowledge. It is up to  
the implementation
how to make use of it.
> If not possible,  is it that the association between these to  
> endpoints will never come up untill the known destination ip  
> address comes up?
If the endpoint knows only one address of the peer and that address  
is not reachable, than
the association can not be setup.

However, in the SIGTRAN environment is is pretty common (at least  
from my experience) that
an endpoint knows all the addresses of the peer in advance (by  
configuration) and can
make use of it even during associations setup.