[SR-Users] Very inconsistent calls

[Wilkins, Steve]

Thank you.  Yes I have been doing packet capturing and it does appear that sometimes there is a missing ACK back from Kamailio; it is just so, so confusing as to why sometimes (often, depending the provider) it works.  Your thoughts do help though!

-Steve

-----Original Message-----
From: sr-users [mailto:sr-users-bounces at lists.kamailio.org] On Behalf Of Michael Young
Sent: Monday, February 12, 2018 8:59 AM
To: 'Kamailio (SER) - Users Mailing List' <sr-users at lists.kamailio.org>
Subject: Re: [SR-Users] Very inconsistent calls

Do that google search. You aren't the only person who experiences that.

For instance, it can be caused by having multiple UAs behind a NAT router\firewall with a poor connection tracking implementation. The firewall can get confused and at times route an ACK to the wrong UA (As Brandon Armstead said, "this issue occurs when ACK is not routed to proper contact.")  Without details on your topology, no one here would be able to help you troubleshoot further or make other suggestions.

There is no substitute for packet capturing and a clear understanding of the call flow. 

Michael

-----Original Message-----
From: sr-users [mailto:sr-users-bounces at lists.kamailio.org] On Behalf Of Wilkins, Steve
Sent: Monday, February 12, 2018 6:26 AM
To: Kamailio (SER) - Users Mailing List <sr-users at lists.kamailio.org>
Subject: Re: [SR-Users] Very inconsistent calls

But very often a call will stay up indefinitely!  This is what is strange.

-----Original Message-----
From: sr-users [mailto:sr-users-bounces at lists.kamailio.org] On Behalf Of Michael Young
Sent: Sunday, February 11, 2018 9:07 PM
To: 'Kamailio (SER) - Users Mailing List' <sr-users at lists.kamailio.org>
Subject: Re: [SR-Users] Very inconsistent calls

And just to add to Alex's comment -- in my experience this is almost always a firewall issue. Whenever I see a call drop in 32 seconds, it is usually because a firewall did not allow the ACK through. 

Google "Asterisk drops calls after 32 seconds" and you get 1,180,000 results...  and the problem is not Asterisk itself. 

Michael

-----Original Message-----
From: sr-users [mailto:sr-users-bounces at lists.kamailio.org] On Behalf Of Alex Balashov
Sent: Sunday, February 11, 2018 7:27 PM
To: Kamailio (SER) - Users Mailing List <sr-users at lists.kamailio.org>
Subject: Re: [SR-Users] Very inconsistent calls



> I have found that calls are very inconsistent.  I use Kamailio 5, 
> Asterisk 14.  When certain Providers like (Sorenson, ZVRS) make calls 
> into a WebRTC client (tryit-jssip), sometime the calls stay up until I 
> close them (10-15 minutes), others times those calls drop in 30 
> seconds.  This is extremely confusing...does anyone else experience 
> this type of behavior?

It is hard to speculate without a capture, and indeed there are lots of moving parts with WebRTC. However, the typical reason why an established call would drop after ~30 sec (32, to be precise) is that the end-to-end ACK from the caller, which completes the required "three-way handshake"
for call establishment, does not reach the callee. This is because it's not constructed correctly by the calling UA, not routed correctly by intermediate entities, or isn't sent at all by the calling UA.

--
Alex Balashov | Principal | Evariste Systems LLC

Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/

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