[SIPForum-discussion] BYE during setup phase

[Devaraja G M]

Hi Anshu,

If  UAC send BYE during calll setup phase then what would be the
response for BYE method. 
Scenario is:- 

UAC                                        UAS, 

INVITE- - -- - - --- -- - - - -- - - -- - - -- -> 
<- - - -- - - - -- - - ---- - - -- - -- --- - -- - - 100 Trying 
<- - - -- - - - -- - - ---- - - -- - -- --- - -- - - 180 Ringing 
BYE  - -- - - --- -- - - - -- - - -- - - -- ->

 

Answer (rfc 3261 : section : 15)

 

A UA MUST NOT send a BYE outside of a dialog. The caller's UA MAY send a
BYE for either confirmed or early dialogs, and the callee's UA MAY

send a BYE on confirmed dialogs, but MUST NOT send a BYE on early
dialogs. However, the callee's UA MUST NOT send a BYE on a confirmed
dialog until it has received an ACK for its 2xx response or until the
server transaction times out.

The impact of a non-2xx final response to INVITE on dialogs and sessions
makes the use of CANCEL attractive. The CANCEL attempts to force a
non-2xx response to the INVITE (in particular, a 487). Therefore, if a
UAC wishes to give up on its call attempt entirely, it can send a
CANCEL. If the INVITE results in

2xx final response(s) to the INVITE, this means that a UAS accepted the
invitation while the CANCEL was in progress. The UAC MAY continue with
the sessions established by any 2xx responses, or MAY terminate them
with BYE.

 

Note : For the callee's UA, it would typically imply a BYE; presumably,
when the user picked up the phone, a 2xx was generated, and so hanging

up would result in a BYE after the ACK is received. This does not mean a
user cannot hang up before receipt of the ACK, it just means that the

 software in his phone needs to maintain state for a short while in
order to clean up properly. If the particular UI allows for the user to
reject a

 call before its answered, a 403 (Forbidden) is a good way to express
that. As per the rules above, a BYE can't be sent.

 

A UAS first processes the BYE request according to the general UAS
processing described in Section 8.2.

A UAS core receiving a BYE request checks if it matches an existing
dialog. If the BYE does not match an

existing dialog, the UAS core SHOULD generate a 481 (Call/Transaction
Does Not Exist) response and pass

that to the server transaction. This rule means that a BYE sent without
tags by a UAC will be rejected.

 

In the early dialog establishment, it is better to send Cancel for the
above scenario, if  we send BYE instead of Cancel, then UAS should send
4XX Response ( It should be 481 response code (Call/Transaction Does Not
Exist))

 

 

Regards,

Devaraj G.M

________________________________

From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Anshupriya Nayak
Sent: Thursday, September 06, 2007 9:18 AM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] BYE during setup phase

 


HI All, 

If  UAC send BYE during calll setup phase then what would be the
response for BYE method. 
Scenario is:- 

UAC                                        UAS, 

INVITE- - -- - - --- -- - - - -- - - -- - - -- -> 
<- - - -- - - - -- - - ---- - - -- - -- --- - -- - - 100 Trying 
<- - - -- - - - -- - - ---- - - -- - -- --- - -- - - 180 Ringing 
BYE  - -- - - --- -- - - - -- - - -- - - -- -> 
                                ?????? 


Regards 
Anshu

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