qos issue between a vg224 and a 2800 router - weird jitter on fax calls
Have a vg224 and a 2800 router. vg224 has fax machines and 2800 has PRI to PSTN. Fax calls from the vg224 to the PSTN have very high jitter often (400-1200 ms). However, regardless of jitter value the faxes always succeed. (The jitter is a problem because Callmanager ART reports the jitter with a QoS Alert; we are getting false positives making the QoS Alert ineffective).
Strangely, jitter is only reported on the vg224, not the 2800. There are no routers in the mix, everything is plugged into the same switch on the same subnet, QoS configs have been verified by Cisco. No problem jitter coming from anywhere else on the network.
Here is the output of jitter resulting from a "sh call active voice | inc Jitter":
CPRTR01#sh call active voice | inc Jitter
FaxRelayMaxJitterBufDepth = 0 ms
FaxRelayJitterBufOverFlow = 0
CPRTR03#sh call active voice | inc Jitter
One solution I am thinking about is somehow configuring the vg224 to consider it's leg a fax call the same way the 2800 considers it (you'll notice that the 2800 has a fax relay jitter buffer as well as, I assume, a packetized voice jitter buffer, which may be what accounts for fax success??). Perhaps this is IOS version problem, I don't know.
Re: qos issue between a vg224 and a 2800 router - weird jitter o
Also, it looks like the 2800 is configured to use G.729 is the preferred codec, but 14,400 bps is the rate. This might be a problem because G.729's rate is only 8,000 bps.
Both sides are set to prefer T.38 fax relay with Cisco as fallback. That should be fine, but fax relay is designed for networks with high latency or packet loss. Fax Passthrough might be more appropriate for your setup.
IntroductionCUCM Routing RulesDial String implementation PolicyCUCM Routing LogicSIP URI Call Routing Analysis+++ Case Study: 1 ++++++ Case Study: 2 +++Conclusion
Over the last few months, I have had the privilege of working on SI...
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...