Do other methods exist for analyzing poor QoS on a VoIP network?

Do other methods exist for analyzing poor QoS on a VoIP network?

I have a site that recently implemented an IP telephone system. It went from a flat IP network to a structured network with VLANs and QoS. After the implementation, users started complaining that their applications began to have poor performance. These applications varied from email client, mapped drive file access to telnet client response. Network statistics (pings & utilization stats) from switches and routers do not show any items of particular concern or high response times.

Is there anything else that you can recommend to consider without having to spend lots of money to analyze the problem? Note: all the infrastructure is Cisco.

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Have you thought about putting all applications on one switch and only voice applications on another? Sometimes that bit of segmentation is all that is needed. Also, you may want to check your software revision. You will also want to be sure that your VLANs are separate -- one for voice, one for data. Since all applications are having issues, I can also suggest that you look at anything else that is common. For instance, if all machines have a certain virus protection, you will want to make sure that it is up to date.

You did not say if you are using a switch in the phone or in the closet, but you will want to check and make sure that the users are on the correct VLAN as well. Hope this helps. Finally, look at your IP addresses -- make sure that you do not have too large a pool and that you are making efficient use of what you do have. Checking for subnet errors can also help.

This was first published in August 2006

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