[Asterisk-Users] IAX2 jitter issue at interval

[Markus Mayer]

We are running 2 Asterisk boxes (ast-a and ast-b) connecting our 2 
offices. We did some voice quality testing as follows:


ast-b calls ast-a externally (ie. over public phone lines), ast-a 
forwards the call back to ast-b over IAX. Since ast-b can't access the 
public phone network by itself it has to talk to ast-a over IAX to reach 
public phone lines that way.

So the external phone-call really looks like this (dialing external 
number of ast-a at ast-b):

ast-b [ IAX ] ============> ast-a [ public phone network ]
                               ^      |
                               |      |
                               --------

Then ast-a transfers call to a different extension at the ast-b location 
(over IAX). So we have:

ast-b => [IAX] => ast-a => [ phone network ] => ast-a => [IAX] => ast-b

We discovered the following pattern of noise on the line: after about 4 
minutes 45 seconds there'll be tiny interruptions in the transmission 
for about 4-5 seconds, after that it would be ok for about 1:35 at which 
point another 4-5 second disruption occurs. Then it would start all over 
again.

Transmission ok for 4:45, disruption, transmission ok for 1:35, 
disruption, ...

So that follows a pattern. Any ideas how to find out what exactly is 
going on here and which box is tropping/losing packets or if it happens 
somewhere in betweeen (hops we can't control)?

Best regards,
Markus