Subject: [Sipping] Invite with Participant Header - Conferece Server Ebhavior

From: [email-masked]
Date: Tue, 12 Feb 2002 13:16:40 -0500

From:  Tom Gray@MITEL on 02/12/2002 01:16 PM

In the SIP Extensions for Conferencing draft
(http://search.ietf.org/internet-drafts/draft-miladinovic-sip-multiparty-ext-00.txt),

section 4.4 contains the text:

'When a dial-in conference server receives an INVITE request from a user that
wants to join in an existing conference and when the conference server allows
this user to join, it SHOULD check if there is a participant header field in
this request. If yes, the value of this header field is compared with the
participant list of the conference server. If there is no difference, the 200
(OK) response is sent without the participant header field. If there is a
difference or if the participant header field is missing in the INVITE request,
the conference server SHOULD insert the participant header field with an actual
list of participants in the 200 (OK) response.'

What is the point of the comparison of the participant list contained in the
INVITE with the list held at the conference server? This will add to the
overhead at the conference server for no reason that is obvious to me. This is
especially true given that the specification is listed with strength SHOULD and
the UAC cannot rely on this behavior being carried out. It would seem that if
the UAC wanted a comparison of this sort for some reason, it should just send
the INVITE without a participant header, receive the 200OK with the current list
of participants and then do the comparison itself - although I do not see why it
would want to do this.

Also, is there one too many SHOULDs in the passage, Doing the comparison without
also complying with the specification on the provision of participant lists
does not seem to make sense.

tg

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---

From: "Igor Miladinovic" <[email-masked]>
Date: Wed, 13 Feb 2002 18:15:53 +0100

Hi,

> In the SIP Extensions for Conferencing draft
(http://search.ietf.org/internet-drafts/draft-miladinovic-sip-multiparty-ext
-00.txt),
> of participants and then do the comparison itself - although I do not see
why it

The intention was to make sure that the user wants to participate to a
specified conference (the participants list in a INVITE request would be an
additional criteria besides the requestURI). But because a reqeustURI is
unique for a conference, it seems that it is not necessary and that it only
produces overhead in the server. We will change this part in the next
version of the draft.

Thank you very much for your feedback.

Regards,

Igor