VoIP and RTP

rakem

Does RTP do sequencing??

If yes, i assume this means that VoIP packets can arrive out of order?

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Met44

Yes, RTP does sequencing.

VoIP clients usually have a jitter buffer feature. Softphones I have seen are usually around 20ms. Within that 20ms buffer, RTP re-orders voice packets (if necessary) and spaces them out so we hear a steady stream of voice.

kryolla

it time stamps the packets

mzinz

What does Cisco consider the highest amount of allowable latency between two VoIP hosts?

networker050184

The recommendation is that delay should not exceed 150ms one way (from mouth to ear). I have ran VoIP networks that were upwards of 300ms delay one way with success though.

rakem

networker050184 wrote: »

The recommendation is that delay should not exceed 150ms one way (from mouth to ear). I have ran VoIP networks that were upwards of 300ms delay one way with success though.

Yea Cisco say 150 but i have read other places that say 250. I would say that getting higher than 300 would definitely start to cause some issues.

AlanJames

rtp = real time. The end user needs to receive them in order, so it has to be time stamped :P

What does Cisco consider the highest amount of allowable latency between two VoIP hosts?

250ms

If you have call manager across sites, it needs to be 40ms round trip delay for successful coms between servers.

kryolla

I was just in a class about setting up a Satellite link to replace our backhaul in case it goes down and this would introduce a delay of 250ms one-way which they said was acceptable but needed an echo can. Did anybody else have to put an echo can for the increase in delay? THanks

rakem

kryolla wrote: »

I was just in a class about setting up a Satellite link to replace our backhaul in case it goes down and this would introduce a delay of 250ms one-way which they said was acceptable but needed an echo can. Did anybody else have to put an echo can for the increase in delay? THanks

wtf is an echo can?

shodown

AlanJames wrote: »

rtp = real time. The end user needs to receive them in order, so it has to be time stamped :P

250ms

If you have call manager across sites, it needs to be 40ms round trip delay for successful coms between servers.

Only if they are in the same cluster. You can have trunks to other sites that have there own cluster and this problem goes away.

networker050184

rakem wrote: »

wtf is an echo can?

Echo canceler, which basically removes echo from voice calls by removing redundant signals.

If you are using Cisco the echo cancellation will take place in the DSPs. I have never had to use it on satellite links, your millage may vary.