Subject: FW: [Speechsc] WGLC MRCPv2-12

From: Eric Burger <[email-masked]>
Date: Tue, 22 May 2007 19:48:42 +0800

OK, MMUSIC folks, can you help us SPEECHSC folks out?

Magnus noted the following may be an issue:
> ------ Forwarded Message
> From: Magnus Westerlund <[email-masked]>
> Date: Fri, 30 Mar 2007 09:12:56 -0700
[snip]
> In section 4.2 you define behavior for using the comedia a=connection
> attribute with the TCP/MRCPv2 protocol. Based on the text and example
> (add recognizer example starting on page 16) it seems that you try to
> allow that multiple m= lines reuses the same TCP connection. However it
> is far from obvious that comedia (RFC 4145) support this behavior. It
> doesn't talk about any relation between multiple m= lines and their TCP
> connections. I would recommend discussing this with MMUSIC.
------ End of Forwarded Message

The "section 4.2" referenced is to MRCPv2, draft-ietf-speechsc-mrcpv2:

When using TCP the m-lines MUST conform to comedia [10], which describes the
usage of SDP for connection-oriented transport.
[snip]
The a=setup attribute, as described in comedia [10], MUST be "active" for
the offer from the client and MUST be "passive" for the answer from the
MRCPv2 server. The a=connection attribute MUST have a value of "new" on the
very first control m-line offer from the client to an MRCPv2 server.
Subsequent control m-line offers from the client to the MRCP server MAY
contain "new" or "existing", depending on whether the client wants to set up
a new connection or share an existing connection, respectively.

Do you think we are OK?  If not, why not, and how can we fix it?

Thanks.

Notice:  This email message, together with any attachments, may contain information  of  BEA Systems,  Inc.,  its subsidiaries  and  affiliated entities,  that may be confidential,  proprietary,  copyrighted  and/or legally privileged, and is intended solely for the use of the individual or entity named in this message. If you are not the intended recipient, and have received this message in error, please immediately return this by email and then delete it.

_______________________________________________
Speechsc mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/speechsc
Supplemental web site:
&lt;http://www.standardstrack.com/ietf/speechsc&gt;

---

From: Gonzalo Camarillo <[email-masked]>
Date: Wed, 23 May 2007 14:27:23 +0300

Hi Eric,

comedia was not designed to handle different m lines sharing a single 
TCP connection. Some time ago, the best practice was not to use the same 
port number in two m lines (assuming the same IP address). Nowadays that 
rule does not seem to apply any longer and some specs use the same port 
in different m lines.

For example, Section 8.1 of the draft below explains how to use a single 
TCP connection for different MSRP sessions. The trick there is that they 
fill the SDP parameters with dummy values and then define their own 
stuff in an MSRP-specific way:

http://www.ietf.org/internet-drafts/draft-ietf-simple-message-sessions-19.txt

If sharing a single TCP connection between different m lines is 
something we want to specify (and it should not be hard to specify), I 
would suggest that it is done in a way that can be reused by any 
upper-layer protocol so that we do not need to re-define the same stuff 
over and over again.

Something else to think about is TCP-ICE and its interactions with 
shared transport connections.

Cheers,

Gonzalo

Eric Burger wrote:
> mmusic mailing list
> [email-masked]
> https://www1.ietf.org/mailman/listinfo/mmusic
>