Subject: SDP (s=,t=) fields and PINT

From: Bernie Höneisen <[email-masked]>
Date: Mon, 23 Aug 1999 16:39:41 +0300 (EET DST)

Hi,

From RFC 2327 (SDP):
The "s=" field is the session name. There must be
ONE and ONLY ONE "s=" field per session description.

--> This means, the "s=" field is mandatary. 

Furthermore in RFC 2327 the "t=" field is not optional.

--> Both of them are omitted in the PINT spec examples.

(Also in RFC 2543 (SIP), there can be found some examples without "t="
field.)

I don't think, that this is a problem in most applications.
But if an SDP parser is following strictly the roules, it might crash
because of that.

Was this discussed earlier? Results?
Comments?

Could it be that future SDP versions make these fields ("s=", "t=")
optional?

t. Bernie

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From: Scott Petrack <[email-masked]>
Date: Mon, 23 Aug 1999 18:19:34 -0400 (EDT)

You are correct, I myself just noticed the same oversight over the
weekend. 

Personally, I think that s= and t= line should be optional, but for the
moment, I will put them into the PINT examples.

BTW, you are also correct that some SIP examples in the RFC are missing
the t= field. This is a good example of being careful in what one sends
and generous in what one receives. I certainly would not be proud of an
implementation which rejected a PINT request because of a missing s= line
or t= line, but this is what the SDP spec says we should do.

Finally, note that the SDP spec says that a time of 0 in start or stop
means that the session is regarded as "unbounded" (i.e. started in the
infinite past or will end in the infinite future). Since of course this is
not possible, this just signifies lack of information. 

Bottom line:

an empty "s=" line is as if there were no s= line, except that it complies
with the spec.

a "t=0 0" line is as if there were no t= line, except that it complies
with the spec.

Scott

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