Lost packets & poor voice quality...

[jebb]

What I have is Multi-Tech VOIP’s that are between 2 of the locations. I’ll call them S1 (VOIP MVP-800) & S2 (VOIP MVP-210) which have different IP subnets. Between S1 & S2, which is about 150 miles, we have a Point to Point dedicated T-1 with Cisco 1721 routers. There's also other data running through this line in addtion to the VOIP traffic. The router programming is below:

class-map match-all VOICE
match ip dscp ef
policy-map VOICE
class VOICE
priority 256
class class-default
fair-queue

The VOIP's are setup with Net Coder@9.6kbps with the Silence Compression, Echo Cancellation, Forward Error Correction active. The diffserve is active on both VOIP's. The problem is that on the MVP-210 the voice quality is sometime poor due to lost packets. When I watch the call progress on the MVP-210 approximatly 10% - 15% of the packets are lost. When I watch the call progress on the MVP-800 there is almost no lost packets and the voice quality is excelent. I'm thinking something is up with the IP packets coming from the MVP-800. I didn't program the router and I'm not so good with it ether so I don't know if it's set up correctly, because I can't find anything else on the network that would cause the problems. Does anyone have any ideas.

Thanks,
Jebb

 

[BuckWeet]

I would check speed/duplex on all ethernet links..


BuckWeet

 

[jebb]

The speeds and duplex are diffrent, one VOIP operates at 10mb because it's manufactured like that and the other operates at 10mb or 100mb because its auto negotiate. The Multi-Tech tech support said this shouldn't be a problem, but I'm going to try a switch on the auto negotiate VOIP to force it to 10mb to see if it makes a diffrence.

Jebb

 

[BuckWeet]

Do you have managable switches to where you could via the statistics of the ethernet ports?

 

[ccmuser]

post a show policy-map interface from both routers..
Post a config from both routers..

What is your average usage of this link?
The first command will verify LLQ config on both routers..

 

[GoTellBigDaddy]

You will want to look at the traffic at both ends and do some tracing/monitoring.

reference:

http://www.protocols.com/

http://www.slac.stanford.edu/xorg/nmtf/nmtf-tools.html

http://www.voiptroubleshooting.com/

http://www.ethereal.com

10-15% lost packets is a good indication that:

a) possible misconfiguration - UNLESS it worked well before point X

b) if it did work well before then your network config may not be electrcially protected end-to-end


BTW- AutoNegotiate usually results in duplex and mismatching so AVOID it. Know the ports/speeds and set them accordingly. Hope your switches are managed.