Hi krishna,
The sdp sessions may be created with the "<username>, <session id>,
<network type>, <address type> and <address> " as id. In that case,
version field is the only way to say the change in sdp for that particular
session. Or else the sdp message will go different sdp session but that sip
session already has some sdp session assoicated. Since sdp can be sent email
or any other means, this is more of a sdp requirement than sip requirement.
Correct me if I am wrong.
Thanks
Karthik
----- Original Message -----
From: "KrishnaKanthT 70508" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, March 26, 2004 6:54 AM
Subject: Re: [Sip-implementors] A doubt in offer/answer model
> Hi elias,
>
> Are you saying that the restriction was imposed only for the sole reason
to identify if the remote party has changed his sdp or not. Cant the same
logic be like this:-
> 1. If the origin line in the offer has been changed, then it means that
the sdp has been changed
> 2. If the origin line is same, then check the version field, If it has
been incremented, then sdp has been changed
> 3. If the version is not incremented, then the sdp has not changed. In
this case the party receiving the sdp must just verify that that sdp has not
been changed.
>
> Correct me if am wrong.
>
> Rgds
> Krishna
>
> Elias wrote:
>
> >"When issuing an offer that modifies the session, the "o=" line of the
new
> >SDP MUST be identical to that in the previous SDP,
> >except that the version in the origin field MUST increment by one from
the
> >previous SDP. If the version in the
> >origin line does not increment, the SDP MUST be identical to the SDP with
> >that version number."
> >
> >- study along with the next statement. If there is a change in the
session
> >then the offerer increments the version # in the o line to denote the
> >session change. But the other fields in the o line remain the same,
because
> >it is from the same offerer.
> >
> >"The answer to an offered session description is based on the offered
> >session description. If the answer is
> >different from the offer in any way (different IP addresses, ports,
etc.),
> >the origin line MUST be different in
> >the answer, since the answer is generated by a different entity. In that
> >case, the version number in the "o="
> >line of the answer is unrelated to the version number in the o line of
the
> >offer."
> >
> >- Answer is generated by a different entity, so the o line is bound to be
> >different.
> >
> >Have a look @ draft-johnston-mmusic-offer-answer-examples for examples
and
> >flows.
> >-Elias
> >Hughes Software Syatems
> >http://www.hssworld.com
>
> >KrishnaKt wrote:
>
> >>Hi all,
> >>
> >>I have one doubt in rfc 3264. Section 8 of rfc3264 says that
> >>
> >>"When issuing an offer that modifies the session,the "o=" line of the
new
> >>SDP MUST be identical to that in the previous SDP"
> >>
> >>1. Is there any specific reason to enforce this condition?
> >>2. Why isn't the same restriction enforced while giving an answer SDP.
> >>
>
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