[SIPForum-discussion] Should ACK sent by SS1 before receiving from UAC?

[Binan AL Halabi]

Hi Siddharth,
The ACK for 2xx responses is end-to-end. So when 200 OK reaches the SIP phone, the ACK is generated from the SIP phone and forwarded to SS1.

// Binan



________________________________
 Från: siddharth sharma <sid77sharma77 at gmail.com>
Till: discussion at sipforum.org 
Skickat: torsdag, 29 augusti 2013 13:51
Ämne: [SIPForum-discussion] Should ACK sent by SS1 before receiving from	UAC?
 


Hi All,
 
I have one issue here. 
 
Call scenario is like below.
 
SIP phone ---> SS1 ----> SBC ----> SS2 ---> MGW ---> PSTN user.
 
In the above scenario, call is originated by SIP phone and sent to PSTN user. 180 ringing message was sent from SS2 and send to SS1 and SS1 sent it to SIP phone.
PSTN user answered the phone. So, 200 Ok was sent by SS2 to SS1. Here, SS1 is sending ACK message first to SS2 and then it is sending 200Ok to SIP phone.
 
During this time, connectivity was lost between SS1 to SIP phone. So, SS1 keep sending 200Ok message and after certain timer, call released by SS1 by sending BYE message. 
 
In this case, CDR was not generated at SS1 end because it was failed call for SS1. But SS2 generated CDR because it has received ACK message. 
 
I want to know is SS1 behaving properly?
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