Subject: [SIP] question on draft-manyfolks

From: Rohan Mahy <[email-masked]>
Date: Fri, 21 Jul 2000 12:45:11 -0700

Hi,

I have some quick clarifying questions on the semantics of the 
direction-tag and confirmation-tag in draft-manyfolks.

 >      qos-attribute    = "a=qos:" strength-tag SP direction-tag
 >                                [SP confirmation-tag]
 >      strength-tag     = ("mandatory" | "optional" | "success" |
 >                                "failure")
 >      direction-tag    = ("send" | "recv" | "sendrecv")
 >      confirmation-tag = "confirm"

Consider an INVITE from A to B with "a=qos:mandatory sendrecv confirm" in 
the SDP.  B replies with a 18x with  "a=qos:mandatory sendrecv confirm".

Because of A's request for qos, B can send an RSVP PATH and get back a 
RESV.  At this point, B knows that bandwidth is reserved from B to A.  B 
needs to send it's COMET right away.  Obviously it can't wait to see if 
bidirectional qos is established because a would wait for B, and B would 
wait for A.

Since B only knows that QoS was established from B to A, does it send 
"a=qos:success recv" in its COMET?  Example packets after the first call 
flow would help here considerably.

Also, presumably A could send a COMET early if it got positive indication 
of bidirectional qos [both a RESV (send direction) and a RESVCONF from B 
(recv direction)].  Is this allowed?

thanks,
-rohan

Relevant section from manyfolks:
 >   When the "Confirm" attribute is present in both the SDP sent by the
 >   session originator to the participant (e.g. in the SIP INVITE
 >   message), and in the SDP sent by the recipient back to the
 >   originator (e.g. in a SIP response message), the session originator
 >   would wait for the COMET message with the success/failure
 >   notification before responding with a COMET message, and responds
 >   instead with a CANCEL if a mandatory precondition is not met, or if
 >   a sufficient combination of optional preconditions are not met.  The
 >   recipient does not wait for the COMET message from the originator
 >   before sending its COMET message.

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