How to check IP phone voice Latency

[Kuldeep singh]

Hi,

How we can check voice latency of Cisco ip phones 7912 / 7960.

Plz see given below scenerio;

At Location A, Cisco call Manager and one ip phone placed

At Location B, only one ip phone is there

then what will be the testing process of voice Latency from Location B to Location A,

am i need to ping call Manager ip address from Location B or  Ping Location A' ip phone

ip address ? I am very confused bcoz how can i ping remote location ip address from

ip phones ( ip phone is not like as computer) ?

KS

[Tapan Dutt]

CMR files can help you!

Export the CMR file and open it in Excel with Options (Delimited and Comma).

Tapan

[Kuldeep singh]

What is CMR file and how to export it ? what types of logs it contain.

Can i not check voice latency through ping from Remote location ?

[Jean-Christophe Majchrzak]

Tapan Dutt a écrit:
CMR files can help you!
Export the CMR file and open it in Excel with Options (Delimited and Comma).
Tapan

Can we trust CMR values ?

For example Latency on LAN between 2 phones 8945 shows sometimes more than 100 ms in CMR.

Due to the fact that bugs are existing concerning call quality parameters (CSCug69210 8945 SCCP firmware reporting incorrect jitter during video calls), I'm not sure if Latency has not the same bug.

Thanks,

JC

[paolo bevilacqua]

Latency is the same as ping RTT / 2.

It is what it is and doesn't really matter much, you can avoid thinking too much about it.

[Kuldeep singh]

RTT / 2  ???  Plz give me one example

[paolo bevilacqua]

http://en.wikipedia.org/wiki/Round-trip_delay_time

[Kuldeep singh]

Anybody can help me to check out voice latency

[paolo bevilacqua · Accepted solution]

Kuldeep singh wrote:
Anybody can help me to check out voice latency 

Read above.

[Kuldeep singh]

Hi Paolo,

Check Voice latency is very critial task for me bcoz we are responsible for detecting charges from one of our client

after seeing report of Latency, Availability and etc. That's way i am thinking lot...

KS

[paolo bevilacqua]

Is not that difficult if you could read above, what is not clear to you ?

[Jean-Christophe Majchrzak]

Hello Paolo,

Why do you say about latency "It is what it is and doesn't really matter much" ?

I agree Packet Loss and Jitter have more visible impact if above what adaptative buffer and codec replay can deal with.

However (as far as I'm concerned) latency on the LAN shows there's an issue somewhere, even if not noticeable.

JC,

[paolo bevilacqua]

Jean-Christophe MAJCHRZAK wrote:
Hello Paolo,
Why do you say about latency "It is what it is and doesn't really matter much" ?
I agree Packet Loss and Jitter have more visible impact if above what adaptative buffer and codec replay can deal with.
However (as far as I'm concerned) latency on the LAN shows there's an issue somewhere, even if not noticeable.
JC,

What issue? OP has nor reported anything except his curiosity. At times I talk over sat circuits with 1 second RTT without any problem.

[Jean-Christophe Majchrzak]

I agree with you. For remote locations, we also are for some offices far beyond the Cisco recommended maximum value of 150 ms latency.

On the LAN latency should be 1 ms and it's not the case for me. I've high latency values in CMR for LAN to LAN calls, also in the same building, and even if nobody noticed it I'm curious to find out the root cause.

JC.

[paolo bevilacqua]

To meaure latency properly you need expensive test devices, not ping to to/from PCs and routers.