[asterisk-users] Audio lag on SIP connections...

[Gordon Henderson]

Had something recently on 2 separate sites where there was a lot of audio 
lag on a call - and by a lot I'm talking 5 seconds or so.

Two different sites, but the setup is similar:

SIPphone A <internet> Asterisk <IAX/Internet> Asterisk <-> SIPphoneB


If the phone called extensions local to it's asterisk there was no lag, 
but if it called out (separate IAX trunk) or to the SIP phone on another 
asterisk box then there was lag...

Googling doesn't find much (other than others complaining about something 
similar), so does anyone have any insight?

The lag issue was cured by rebooting the ADSL router at SIP phone A's end.

The other site that experienced this has an identical router - Draytek 
2820, and that also was cured by rebooting, but I'm keen to get to the 
bottom of it.

Two things going through my mind - One - DNS. Could something be doing a 
DNS lookup which is being stalled by the router (routers are the DNS 
servers in this case) causing a delay on the audio? Or could the routers 
themselves be queueing up 5 seconds of traffic? (Unlikely, but I've seen 
Drayteks do other weird things)

Any clues, suggestions, etc. welcome!

Thanks,

Gordon