'Re: [Sip-implementors] Transaction Overlap(CANCEL/BYE with INVITE)'

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List:       sip-implementors
Subject:    Re: [Sip-implementors] Transaction Overlap(CANCEL/BYE with INVITE)
From:       ravshiv () pgsolutions ! com
Date:       2001-06-28 5:07:26
Message-ID: OF399EDD71.EBC615FA-ON65256A79.001AE908 () phl ! com
[Download RAW message or body]

Hi,
   See my comments inline.

                                                                                      \

                    "Ramachandran Iyer"                                               \

                    <rama14@yahoo.com>                  To:     \
                sip-implementors@cs.columbia.edu                              
                    Sent by:                            cc:                           \

                    sip-implementors-admin@cs.co        Subject:     \
                [Sip-implementors] Transaction Overlap(CANCEL/BYE with   
                    lumbia.edu                          INVITE)                       \

                                                                                      \

                                                                                      \

                    06/28/01 09:42 AM                                                 \

                                                                                      \

                                                                                      \

hi,

when i was trying to put a state machine for CANCEL
and
BYE... the problem i face is as below..

now CANCEL and BYE can be issued at (say) any point of
time in the call...

1> Initial (no call) ..
     in this CANCEL and BYE will result in error
     as there is no active session ..no c-seq found
     so a straigh foward error..fine
2> calling
3> call procedding
      In both the cases where the session is waiting
      on a reponse(prov/final)..say CANCEL or BYE
      occurs..(kind of transaction overlap)..
      but still according to the SIP theory we have
      to complete the INVITE session by ACK'ing it
      and then entertain the CANCEL or BYE..
      then what is the point in CANCEL /BYE coming
      in the middle of a INVITE..it still has to wait
      till the ACK'ing is completed..

   So is it safe to consider that..CANCEL and BYE
   transaction states will always follow after the
   completion of the INVITE..(b'cos even if it arrived
   in the middle..it still has to wait till the INVITE

   transaction is complete)..

> in this case if the CANCEL request comes there is no need for you to
wait. It is said nowhere in the RFC that > CANCEL request must be issued
after the transaction is completed. If the CANCEL request comes to the
Proxy
> it immediately responds with a 200 class response. Then it generates a
new CANCEL, and forwards the request
> to all destinations with pending requests. The behaviour of the UAS on
receiving the CANCEL request depends
> on whether the server has already sent a final response for the original
request. If it has, the CANCEL
> request has no effect on the transaction. It sends an OK response to the
UAC. If it has not sent a final
> response, it immediately responds to the  original request with a
487(Request terminated)response. Then the
> UAC sends an ACK request to confirm receipt of any final response. If the
UAS has no record of the request
> being cancelled, the CANCEL is responded with a 481(Transaction/call leg
does not exist).

> in the case of a BYE request, the user has to wait until the transaction
is completed.

   Also then how does this conform to the logic
that each transaction is independent..

Rama

Ravi.B.S.
Analyst programmer,
Phoenix Global  Solutions,
Bangalore-1
Email ID:ravshiv@pgsolutions.com
Phone:6575561,6573610
Extn:2401
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