VoIP guru challenged here, handling de.....l.....ay

binarysoul

Given VoIP uses UDP for voice transmission, how do you determine delay?

I'm currently seeing 3000ms delay for MGCP, which is TCP-oriented. Isn't that too high?

Everybody emphasizes the fact that VoIP is sensitive to delay, dahhhhh, that's obvious, but nobody gives an idea of how much delay is acceptable. I've seen some Cisco docs that indicate anything about 250ms is unacceptable. First, how do they determine delay on UDP? Second, is it 250 for data (voice in this case) or for setup and control, coder/decoder?

To summarize, what's your experience with VoIP delay? We don't manage Cisco CallManager, but we're responsible for managing the network.

dtlokee

If you're using Cisco routers at or near your endpoints you can use IP SLA monitor to determine the delay over a period of time. RTCP keeps track of the RTP packets, delay, count and a few other pieces of information. A 3000 ms (3 second) delay on MGCP is not acceptable. That would indicate it takes 3 seconds for any control signals to reach the endpoint, leading to a 3 second delay between an off hook signal and a dial tone.

keenon

the documentation i have read on cisco site is 150ms max 1 way is acceptable but anything over you will hear problems. since your responsible for the network i would start looking /verifying your qos settings. I'm not a voice guy but get alot of voice troubleshooting