outbound calls getting droped no ACK sent from UAC

orphol

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#1
I have just implemented a new elastix 1.3-2 and am finding out some of my outbound calls after 4 to 10 sec of the call it will get dropped however some calls are established with out any problems. I have connected my sip provider (Bandtel) and they are saying the UAC is not sending a call acknowledgment after the call is made. this is what they are telling me
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I will refer to the outbound calls you place where you are acting as the UAC. or client. section 13.2.2.4 clearly states in paragraph 3 " The UAC core MUST generate and ack request for each 2XX received from the transacton layer" since you are using asterisk it is most likely only a couple causes of the issue. 1 is that the core is not functioning correctly or 2) the security levels are set up so that if the DNS resolution takes place after a call is in the invite state and the signaling IP changes the original address is not used but the new address is used. or the message is blocked all together
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question is has anyone had this issue or have any thoughts on a fix ?
Thank you .
 

Bob

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#2
orphol,

First of all there are no security settings that should cause the DNS issue that they refer to. You have no IP filtering or similar on the Elastix system, so generally you can dismiss that possibility (unless you are blocking with Firewall/Router).

Secondly, the issue that they refer to on the ACK issue, was a well known issue with certain setups (e.g. firewalls) a few years ago, but Asterisk in general does respond with ACKs for each 2XX received. This line sounds like it came out of their knowledgebase, which looks like it is quoting the RFC's. However it does give an idea of where to start.

So in a nutshell, it is saying that your Elastix box is not responding with an ACK to a 2xx that they send. Now this could be that that your box is not receiving it to respond to. That is not to say that they did not sent it, just something blocked it or the packet was lost.

The concern is that you say some calls work, others don't, have you any pattern to this, such as Mobile calls work, landlines dont etc.

In the meantime however, I would start looking at your firewalls on your system (do you have a dedicated firewall or router - what type?). Have you setup port forwarding for SIP, or are you relying on NAT (which would be part of the issue). Have you setup SIP_NAT.CONF - have a read on google for this, in particular, externip= and localnet=. These have an impact on the SIP header, and could be a cause.

In fact I would look into the SIP_NAT.CONF first to see if this resolves your issue. I know it was an issue with a particular VSP here (and only one), and calls were dropping after 20secs, even though the call established.

Let us know how you go...

Regards

Bob
 

Mirko87

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Oct 20, 2008
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#3
Hi, I've got an Elastix PBX behind a fire-wall SmoothWall 2.0 and it works good.

But I'm trying to make another configuration for my friend, and it doesn't work.
The fire-wall is the same, in the net-work configuration is the same... and... the VoIP Service Provider is the same.

IP Address of the PBX-->192.168.2.251
Net-Mask -->255.255.255.0
Gateway -->192.168.2.254
DNS -->My WAN Address

The sip_nat.conf:
nat=yes
externip= My WAN Address
localnet=192.168.2.0/255.255.255.0
externrefresh=10

But the inbound calls getting dropped after 20/21 seconds.... And the outbound calls after a minute...

Could it be a router problem? Next week I'll change it... but I'm going crazy in the last 2 weeks for this routing problem...
 

orphol

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#4
I am still having problem with mine. I have taken the unit out side of firewall but still same issue only some out going calls after around 8 seconds it gets dropped . there is not a pattern per say.. and only it happens on the out going calls .. incoming calls work like a charm. hitting a wall ?
 

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