[SIPForum-discussion] Issue in sending ACK

[Deepak Rawat]

Hi Satya, Step 1    A-----Invite------------>BStep 2    A<----180 ring---------B
Step 3    A<-----200 OK---------B Step 4    A---------X---------------B

Now if the ACK was not sent by A to B, UA B will think about it's 200OK which he sent to A at step 3. The time when UA B sent the 200OK, he set's the timer to 0.5 sec and waited for .5 sec. Since no response in the form of ACK from A,

 UA B will think either his 200 OK lost somewhere in the network  

OR 

UA A received my 200 OK but UA A is not responding back 

OR 

UA  A did sent the ACK , but probably ACK lost somewhere . 

Due to all above , UA B will retransmit the 200OK and will set the timer this time to 1 sec and it will go on . Total of 7   200 OK (.5 sec, 1 sec, 2 sec, 4 sec, 8 sec, 16 sec, 32 sec). If still no response , UA B will send the cancel message. Step 1    A-----Invite------------>BStep 2    A<----180 ring---------B
Step 3    A<-----200 OK---------B   .5 secStep 4    A---------X---------------B
Step 5 A <-------200OK--------B 1.0 sec
Step 6 A ->------X---------------B
Step 7 A <--------200 OK------B 2 sec
 




Regards,
Deepak Rawat
Date: Tue, 26 Mar 2013 15:10:25 +0530
From: rsatya568 at gmail.com
To: discussion at sipforum.org
Subject: [SIPForum-discussion] Issue in sending ACK

Hi All,

Let A is sending invite to B then B will send 180 ringing ,200 OK but A will not sending ACK so
Is voice path will establish in between A and B ?


so what will happen if A will not sending ACK ?
whats the problem of A why A is not sending ACK ?



Regards
satya


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