[Kamailio-Users] Possible timing/latency related problem ?

[Alex Balashov]

Latency is not in itself an impediment to a successful VoIP 
conversation;  latency is just uncustomary for humans, and causes them 
to talk over each other not unlike satellite or microwave long-distance 
telephone conversations between hemispheres.

The problem that is often present in connection with the underlying 
causes of high latency but is a different phenomenon than latency is 
jitter.  Jitter is the presence of nonlinear temporal deltas between the 
arrival of RTP packets.  RTP arrival at non-constant intervals causes 
audio distortion, "drop-outs," static, repetition, and stream 
synchronisation problems.

The bottom line: if there is high but very constant latency, you can 
still have a manageable conversation.  However, the same things that 
cause high latency -- for example, link congestion -- often cause 
jitter.  The degree of packet queue saturation and/or bandwidth 
exhaustion often varies across time and creates stochastic, 
indeterminate effects that jitter buffers cannot be designed around, and 
certainly not perfectly at any rate.

I would bet that jitter is the cause of your problem, simply because it 
often goes hand-in-hand with latency.

-- 
Alex Balashov - Principal
Evariste Systems LLC
1170 Peachtree Street
12th Floor, Suite 1200
Atlanta, GA 30309
Tel: +1-678-954-0670
Fax: +1-404-961-1892
Web: http://www.evaristesys.com/