[Users] ACK is answered after the INVITE. But ACK arrived first!

Klaus Darilion klaus.mailinglists at pernau.at
Fri Apr 21 09:25:02 CEST 2006


Bruno Machado wrote:
> Hi all
> 
> Im in trouble with this problem: I have a Openser the connect to a 
> carrier. I need that this proxy answer the messages in order that it 
> receive. In my situation, other device one hope behind it, sends an ACK 
> and, miliseconds after, it sends an INVITE to change the session. The 
> server where the Openser is installed receive the ACK first than INVITE, 
> but it ALWAYS forward this INVITE first. This way, I cant connect my 
> proxy to the carrier. I need to know how I can change this behavior: the 
> SIP proxy needs to send the ACK first. First in, first out..... Anybody 
> knows how to do it?

Hi!

The client which receives the reINVITE before the ACK should be smart 
enough to accept the reINVITE (which is also an implicit ACK), and then 
ignore the late coming ACK.

btw: I've also seen this phenomenon recently when testing with SIPP. The 
basic scenario sends INVITE-ACK-BYE. The BYE is sent immediately after 
the ACK. In openser, the BYE overtakes the ACK - everytime. Is there 
some special processing for ACK which takes more time the for other in 
dialog requests?


regards
Klaus




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