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

[Vikram Ragukumar]

Hello,

Scenario 1
----------
  ---------    --------    --------    --------    --------
|Cellphone|--|Wireless|--|Internet|--|Kamailio|--|Asterisk|
|         |  |Router  |  |        |  |rtpproxy|  |        |
  ---------    --------    --------    --------    --------
                       |<-Lowlatency->|
Scenario 2
----------
  ---------    --------     --------    --------    --------
|Cellphone|--|Wireless|---|Internet|--|Kamailio|--|Asterisk|
|         |  |Router  |   |        |  |rtpproxy|  |        |
  ---------    --------     --------    --------    --------
                       |<-Highlatency->|

Both scenario 1 and scenario 2 are similar in setup, excepting that in 
scenario 2 there is a greater latency involved in SIP and RTP 
transmission between the wireless router and Kamailio+rtpproxy server.

In scenario 1 calls from the cellphone using a SIP softphone app go 
through 100% of the time with both endpoints of the call being audible.
However in scenario 2, calls from the cellphone go through with both 
endpoints of the call being audible only sometimes, and during all other 
attempts, call goes through with no voice from the cellphone.

In scenario 2 the SIP softphone can always register, the SDP connection 
address is always rewritten to use rtpproxy so it does not appear to be 
a NAT issue, rtpproxy's logs show a session being set up and torn down, 
with RTP stats for caller being 0.

In both scenarios, the equipment and their configuration are identical. 
(Both cellphone's are Nokia e51, router's are Netgear wgr614) What might 
be probable causes for the behavior seen in scenario 2 ? Could there be 
a timing/latency related issue ?

Any pointers on how to approach this problem will be appreciated.

Thanks and Regards,
Vikram.