Paul, Thanks for your response and support :-)
Regards, Yong -----Original Message----- From: Paul Kyzivat [mailto:[EMAIL PROTECTED] Sent: Friday, February 23, 2007 11:18 AM To: [EMAIL PROTECTED] Cc: [email protected] Subject: Re: [Sip-implementors] RFC 2327 SDP "c=" line question Yong Xin wrote: > Hi, > > We have different interpretation regarding to the "c=" line definition > in RFC 2327. > > Session description > c=* (connection information - not required if included in all > media) > > Media description > c=* (connection information - optional if included at > session-level) > > I think "c=" line is optional when SDP has no "m=" line, since I don't > see a use case to present connection info when there's no media > description. But some people think the above definition indicates the > "c=" line is mandatory and must be present in either session or media level in any case. > > Could anyone tell me which interpretation is correct? That is an interesting question. The interpretation you propose makes more sense to me than the alternative. The question is whether the text in RFC 4566 supports that interpretation. I think the following from section 5.7 is the relevant text to interpret: A session description MUST contain either at least one "c=" field in each media description or a single "c=" field at the session level. It MAY contain a single session-level "c=" field and additional "c=" field(s) per media description, in which case the per-media values override the session-level settings for the respective media. Now suppose you have a session description that has no media descriptions. Does that 'have at least one "c=" field in each media description'? I think so. It has one "c=" in each (in this case none) media descriptions. So I support you. Paul _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
