BCM450 VoIP Echo Problems

[tjl052628]

I have went over the QOS with the network IT guy as Avaya requested in the doc. We are running one flat vlan with no router, static assigned IP address to all the BCM and voip phones. around 175 to 200 phones. codac is set G711 and G729 both set at 20 ms, TRO, TAD are on all the bcm. I have tryed turning on the QOS on the voip phones did not make a diffrence. I am just trying to get it to work as good as possable for the cust. I did look at 2 of the cust switches they are Dell Power connect 3548P not sure what the other schools are useing probley the same with this being a school just looking for any ideas that might help this cust. Been working with our Atac people making call and running wire shark when making calls. The echo is not allways there on all the calls. I went to Jr high made calls sound good then went to Technology bldg and sound good then echo started back. Maybe when the network starts getting loaded up the echo starts? Fiber between all schools. Thank you for any ideas you might have, at this point I would try anything that might make a inprovement. The echo starts after the call is connected for 4 sec then sounds good. I had one person make the comment to set the codac to G729 on all the bcm and ip phones and no auto neg the call will not sound as good but thought the echo would go away by fource to use G729 the call would sound more like a cell phone call. Any one with a though that might help inprove the VoIp call? Thanks

 

[DigitelD]

I would certainly separate the IP phones and your data network by having a separate VLAN for voice. Quality of service on your network is essential. The Dell switches have advanced QoS.

SHK Certified (School of Hard Knocks)
NCSS, ATSP/IP

 

[tjl052628]

Yes sir all ready separate the voice and data

 

[ucxguy]

QoS settings, codecs that are used, VLANs and similar IP related items usually have absolutely nothing to do with echo. Thus, changing them shouldn't have any real impact. You haven't mentioned anything about the area that is likely to cause the echo - that is the connection of the BCM450 system to the PSTN.
When you make a direct call between two phones connected to the BCM450 system (i.e., an internal call), do you get any echo (you should not). Do you get echo on PSTN calls?

 

[tjl052628]

It's on a PRI, there was echo on the entire system (according to customer reports). We set the codec to 729 and it actually went away, beginning to believe the customer has us bandwidth restricted on the VLAN they built for us.

 

[ucxguy]

Bandwidth limitations would cause different symptoms (crackling, missing fragments of speech, etc.) - but not echo. What is the configuration of echo cancellation on your BCM (Application Resources - Media Gateways)? If you have non-linear processing (NLP) enabled, you may consider trying to turn off this feature - in some environemnts, you can get better results without NLP.

 

[tjl052628]

I will try to turn off the NLP today. Will a person ever totaly make the Echo go away? or just get it to the best it can be

 

[telcodog]

I've found that switching your ISDN interface under your Resources tab from ISDN to PSTN (or vice versa) can eliminate echo on IP sets. Also have a look at your CSU Line build setting. Try changing the gain amount.