Re: [MMUSIC] Offer/Answer PT Questions - text proposal

["Drage, Keith (Nokia - GB)" <[e-mail]>]

My assumption is that the term “session” in RFC 3264 is inherited from RFC 3261 when used in the context of SIP. That definition is as follows:

      Session: From the SDP specification: "A multimedia session is a
         set of multimedia senders and receivers and the data streams
         flowing from senders to receivers.  A multimedia conference is
         an example of a multimedia session." (RFC 2327 [1]) (A session
         as defined for SDP can comprise one or more RTP sessions.)  As
         defined, a callee can be invited several times, by different
         calls, to the same session.  If SDP is used, a session is
         defined by the concatenation of the SDP user name, session id,
         network type, address type, and address elements in the origin
         field.

I’d note that we have definitions of both “multimedia session” and “communication session” in RFC 7656. My assumption is that the definition above relates to “communication session”.

Given that we have a currently open revision of the SDP specification, it might be worth making a more robust definition by reference in that document.

Note that RFC 7656 also gives the definition of RTP session.

Regards

Keith

From: mmusic [mailto:[e-mail]] On Behalf Of EXT Roman Shpount
Sent: 03 March 2016 16:20
To: Christer Holmberg
Cc: Paul Kyzivat; [e-mail]
Subject: Re: [MMUSIC] Offer/Answer PT Questions - text proposal

On Thu, Mar 3, 2016 at 2:14 AM, Christer Holmberg <[e-mail]<mailto:[e-mail]>> wrote:
>> IF we agree that the PT binding is per session, and not per direction, we can update that part of 3264, because THAT’s what causing Martin’s issue.
>>
>> RFC 3264 might be slightly ambiguous about the answer since it does not even define the "session", but it never states that binding is per direction. It states
>> that binding MUST NOT change for the duration of a session with no direction mentioned in this restriction. This mean we might need a clarification but not necessarily an update.

Well, technically it is an update to RFC 3264, even if the new text only clarifies existing text :)

The biggest problem with RFC 3264 is coming from the fact that term "session" is not even defined and things like RTP session are not even mentioned.

>Bigger problem is that this requirement is unimplementable with 3pcc and routinely ignored. This is definitely a problem and needs an update to resolve.

But then, is it a good idea to say that the PT binding is for the whole O/A session? What preventing us from saying that it is per direction? The fact that it would conflict with the RTP session definition?

If there are more then two parties in the RTP session, i.e. if one of the parties in O/A is an RTP forwarder, the same PT cannot possibly be assigned to different codecs in different directions. This is why PT binding is per O/A session.
_____________
Roman Shpount