Subject: [Sipping] Tunnelling QSIG over SIP

From: "Elwell, John" <[email-masked]>
Date: Mon, 02 Jun 2003 14:31:14 +0100

I am exploring ways of tunnelling QSIG over SIP making use of the MIME type
already defined for this purpose. One scenario of interest involves
significant QSIG traffic between a given pair of gateways, and to support
this efficiently a single SIP dialog is used to transport multiple QSIG
calls. The dialog would be established on a semi-permanent basis and QSIG
calls would be established and released on demand over this dialog.

The main difficulty is the fact that each QSIG call will require a pair of
RTP streams and therefore call establishment or call clearing will require
an update to the session description (by means of UPDATE or re-INVITE). The
question is how to represent the session, which at any instant will comprise
n pairs of RTP streams, and relate these streams to QSIG channels. A
possible solution is to use multiple m= (typically m=audio) lines, where the
first m= line corresponds to channel 1, the second to channel 2, etc. The
last m= line would correspond to the highest numbered QSIG channel in use.
Any unused channels within the range would be marked as inactive
(a=inactive). This convention would need to be understood only by the
gateways concerned.

I would welcome any comments on this proposal, or any alternative solutions.

John Elwell ([email-masked])

_______________________________________________
Sipping mailing list  https://www1.ietf.org/mailman/listinfo/sipping
This list is for NEW development of the application of SIP
Use [email-masked] for questions on current sip
Use [email-masked] for new developments of core SIP

---

From: Rohan Mahy <[email-masked]>
Date: Tue, 3 Jun 2003 14:37:05 -0700

> last m= line would correspond to the highest numbered QSIG channel in 

rather than using specific m-lines, you could use the flow, group, and 
media-stream id concepts defined here:

draft-ietf-mmusic-fid-0?.txt  (i'm on an airplane)

thx,
-r