[prev in list] [next in list] [prev in thread] [next in thread] 

List:       sip-implementors
Subject:    Re: [Sip-implementors] A SIP question?
From:       Christer Holmberg <christer.holmberg () lmf ! ericsson ! se>
Date:       2001-04-30 6:27:59
Message-ID: 3AED05EF.ECA4B1C7 () lmf ! ericsson ! se
[Download RAW message or body]


Hi,

First, you must always ACK the final response to the INVITE, no matter
what it is, and no matter what other requests (ie a CANCEL to cancel the
INVITE) you have sent.

Second, currently it is allowed to send a BYE instead of a CANCEL. This
has also recently been discussed on the SIP mailing list, so you may
want to have a look in the archieves.

So, I guess your flow would look something like this:

UAC --INVITE----------> UAS
UAC --BYE/CANCEL------> UAS
UAC <--487(INVITE)----- UAS
UAC <--200(BYE/CANCEL)- UAS
UAC --ACK-------------> UAS

There are also some special scenarios, ie when a 200(INVITE) from the
UAS and a CANCEL from the UAC are sent at the same time. In this case,
if the UAC sends a CANCEL, and still receive a 200 final response, the
UAC shall ACK the final response and then send a BYE. If the final
response is non-200 the UAC only needs to ACK the INVITE.

Regards,

Christer Holmberg
Ericsson Finland


Vijay Ramachandran Iyer wrote:
> 
>         Another question which I couldnt find an answer to in the spec.
> Can a BYE be sent by a UAC immediately after an INVITE (without getting a
> response to the INVITE?). Or is a BYE to be sent only after getting some
> sort of reponse to the INVITE (thus enforcing the 3-phase-ness of
> an invitation).
>         Also I think the 3-phase-ness of invitation is compromised when it
> is said that a UAC on receiving a 200 OK to an INVITE may ACK or send a
> BYE if it no longer wishes to talk to the UAS..
> Thus the above looks like:
> 
> UAC --INVITE--> UAS
> UAC <--200 OK-- UAS
> UAC--BYE---->  UAS   (instead of an ACK)
> UAC <--200OK(bye)-- UAS
>                                 (I am following RFC 2543)
> 
>  Thus now it become 4 phase!!!
> 
>  what is the current bis # ??
> 
> Vijay
> 
> _______________________________________________
> Sip-implementors mailing list
> Sip-implementors@cs.columbia.edu
> http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
["christer.holmberg.vcf" (text/x-vcard)]

[prev in list] [next in list] [prev in thread] [next in thread]