Subject: Removal of SCTP from comedia draft.

From: "Fairlie-Cuninghame, Robert" <[email-masked]>
Date: Wed, 7 Mar 2001 03:47:56 -0800

Hello,

I would like to discuss the removal of the SCTP from David Yon's
draft-ietf-mmusic-sdp-comedia-00.txt. I have spoken privately with David
about this and he suggest I bring it to the work gorups attention.

There are a number of reasons why I think that SCTP is not a
connection-oriented media transport mechanism in way that the draft is using
the term. I think an SDP profile for SCTP need's its own draft for a number
of reasons. The SCTP-SDP draft may well reference this comedia draft but
should not not be included within it.

Reasons why SCTP is different to TCP in terms of being
"connection-oriented":
- For SCTP, the connection/association is only between SCTP endpoints and is
not on a per media connection basis. 
- Once the SCTP association is established between endpoints, no connection
is required to start or stop using a particular stream (as far as I can
tell), that is, you just send data to a stream much like a connectionless
datagram protocol.

Reasons why comedia draft is insufficient for SCTP:
- SCTP MUST use an existing SCTP endpoint association if one exists such
that the direction parameter MUST be ignored in many connection cases. 
- Single IP address ("c=") and "m=" line port is not sufficient to identify
an SCTP stream. An IP address, port and stream number is needed.
- Single IP address, port & stream number is only sufficient to identify an
existing association and not sufficient to create a new SCTP association
(which is necessary in my opinion). [EG need to supply multiple transport
local addresses, number of streams, direction, etc]

I am in favor of removing the mention of SCTP from the comedia draft and
beginning work on a dedicated SCTP SDP profile which addresses these issues.
I feel at this preliminary  stage the tsvwg WG mailign list is a more
appropriate discussion place with migration to mmusic when work nears
completion.

Comments please (especially if I have an SCTP details wrong). [Reply to
[email-masked] is probably best.]

Regards,

Robert.