[SIPForum-discussion] Time interval between requests

[mustafa aydin]

Hi All,
 
First of all , I would like to thank you for all these valuable comments. 
 
I know  that "CANCEL" can not be sent to the initial INVITE unless UAC gets a provisional response. However, I could  not find anything which states that it is also applicable to RE-INVITE requests and also the SBC vendor does not want to change their code to wait for  1xx response before sending CANCEL since they also say that it is not particularly mentioned in RFCs (although they reply with 100 trying to Re-invite :) ). But for me  it is very logical to wait for 1xx response due to the fact that UAS can receive CANCEL before the RE-INVITE and it would cause a race condition.
 
@Abhisek,
 
Everything is going well here, I hope the same for you. I believe you can send a cancel to re-invite, first of all there is nothing in RFCs which says we can't do it, secondly, how can the UAC terminate the re-invite request other than sending a CANCEL message ?  If you google it , you can see lots of example with Re-Invite-Cancel, but unfortunatelly none of them mentions about waiting for provisional response.
 
You can find the call flow below, you know the softswitch vendor very well :)
 
                SIP PBX                SBC (B2BUA)              Softswitch
 
                     ------ ReInvite------>               --- Re-INVITE-->     
                     <----- 100 trying-----                 ---CANCEL--->    <0.0004 sec later>
0.003 sec ltr    ------CANCEL------>             <-- 200ok (to cancel) --  
                   <-- 200ok (to cancel) --             <--- 200 ok w SDP (to re-invite)--    
                                                         <softswitch keeps on sending 200ok w sdp until timeout>
 
It is another question why softswitch does not send back 487 although it sends back 200 OK to Cancel. It might be because of not being able to process CANCEL message (but somehow it can send back 200 OK to cancel), but it is not our main concern for now. 200 ok w SDP messages are most probably also the result of congestion on softswitch side.
 
Regards,
Mustafa AYDIN
 
 

________________________________
From: Abhisek Acharya <abhisek.acharya at gmail.com>
To: mustafa aydin <mustafaydin82 at yahoo.com> 
Cc: "discussion at sipforum.org" <discussion at sipforum.org> 
Sent: Wednesday, September 5, 2012 9:25 PM
Subject: Re: [SIPForum-discussion] Time interval between requests


how is borusan doing by the way buddy  



On Wed, Sep 5, 2012 at 10:37 PM, Abhisek Acharya <abhisek.acharya at gmail.com> wrote:

Hey mustafa , 
>
>
>one correction....
>
>
>For example, can UAC send CANCEL of a RE-INVITE just 0.0004 sec later ?  
>
>
>you can not CANCEL a RE-INVITE as CANCEL is always for a unestablished call and RE-INVITE is a mid-dialog request which means that session is already established and one party is sending a RE-INVITE to change the media session and if the other party is not ready to accespt that the it can always send a 4xx error response and it will have no impact on the call.
>
>
>regardsabhisek 
>
>
>
>
>On Wed, Sep 5, 2012 at 10:28 PM, Abhisek Acharya <abhisek.acharya at gmail.com> wrote:
>
>Aside pls send me a trace  
>>
>>
>>abhisek 
>>GSLAB,PUNE
>>
>>
>>
>>On Wed, Sep 5, 2012 at 10:26 PM, Abhisek Acharya <abhisek.acharya at gmail.com> wrote:
>>
>>hey Mustafa, 
>>>
>>>
>>>few questions.
>>>
>>>
>>>CANCEL is always after proviisonal response.Is there a B2B involved in u r picture.If UAC sending CANCEL after receiving 1xx response then the B2B or the UAS MUST process the CANCEL accordingly.Timer really does not matter.Please test in your lab and lemme know with your result or you can send me the call trace.
>>>
>>>
>>>aside how can u be sure CANCEL is being not processed ?
>>>
>>>
>>>abhisek 
>>>
>>>
>>>
>>>
>>>On Wed, Sep 5, 2012 at 1:00 PM, mustafa aydin <mustafaydin82 at yahoo.com> wrote:
>>>
>>>Hi All,
>>>>
>>>>Is there any time frame mentioned in RFCs which defines time interval between REQUESTS? For example, can UAC send CANCEL of a RE-INVITE just 0.0004 sec later ?  I tested some SIP servers , but none of them could handle the CANCEL properly when it comes just in such a short interval, but I  need to refer to RFCs in order to prove this wrong behaviour to vendor.
>>>>
>>>>Thanks,
>>>>Mustafa AYDIN
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>>>>
>>>
>>
>
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