VoIP sets get constant dead air calls!! 1

[snobleky]

We have an 81c connected to a Nortel Branch office via a PTP T1. All the sets on the Branch Office register back to my signaling server and will fail over to their signaling server if the T1 fails. The problem is the I2004 sets get lots of dead air calls both internally and exteranlly. The few I2004 sets we have here at our main location experience the same issues anyone have an idea where to start?

 

[johnpoole]

how tight is your bandwidth? and how clean

john poole
bellsouth business
columbia,sc

 

[snobleky]

Bandwidth as far as I can tell is clean. We have the T1 segmented with 384k for voice and 768k for data.
We do see some packet loss showing up on the switch but with 3.0 I understand that may not mean anything.
There is no Qos which we are getting ready to implement, this may be the whole reason, but we only seen this the last few months.

 

[sl1input]

It will most likely be QOS.

I had the same prob with IP sets at remote sites.

They had one way transmission.

As soon as the QoS was implemented, hey presto!!!

I think the data guy made the switch ports "Trusted Ports" and turned on QoS on the uplink.

Also make sure you have the latest patches on both Sig Servers, both Call Servers, all your Media Cards and have the latest Telephone Firmware.

 

[snobleky]

Starting to set up Qos in the morning I hope this solves the problem. Thanks for the information, I will post back with the results.

 

[Sennback]

this could also be a network problem, not related to bandwidth.

Sometimes when IP calls doesnt work properly, it can be a firewall or router either blocking the voice stream, or pointing in the wrong direction.

Sometimes signaling works, the call is presented, but "voice" cant be transported.
This could be both ways or just in one direction.

 

[snobleky]

Well we had Bell South work with us to do Qos end to end and it didnt change it a bit. Seems the calls are always from digital to ip that fails so we are replacing the media gateway card tomorrow I hope it helps.

 

[3Sixty]

The media card provides the interface between the IP phones and TDM and lines etc.

Did it ever work?

What size of MSC card is it?

What codec are you using on the system?

Can you confirm the card is configured correctly.

Marshall

http://www.nortelsupport.net

 

[teekow]

You also need to make sure everything is patched and updated. What versions are the vgmc, ss, and pbx?

 

[I2007]

The most common problem for one way speech on nortel systems is that the packets are NAT'ed behind a firewall. If you can route it instead it is a huge advantage. If you use NAT you have to setup up an echo server.

i2007

 

[snobleky]

Ok we replaced the media card and so far no dead air calls,
however we now have poor voice quality on TDM to IP calls only, the IP to IP are crystal clear. Working on tweaking the Qos settings to see if this resolves the problem.

 

[sl1input]

Take a look at your DSCP (Diff Serve) settings on the Sig Server.

Node > Edit > Signalling Servers > QoS > DSCP

The default values are 46 for Voice and 40 for Control.

You need to make sure that your data switches (Nortel or Cisco??) are set to work correctly with these values.

i.e. DSCP 46 for Voice must be given highest priority (Expedited Forwarding)

DSCP 40 for control packets can also be highest priority but i would set Control a lesser priority.

Also think about tracing some calls on a mirrored port using a sniffer to make sure your DSCP markers are being passed.

 

[snobleky]

Thank God its working!!!

We had replaced the media gateway card and eliminated the dead air issue but got terrible incomming voice.

We put the old gateway card back in and everything works great I dont even get any packet loss messages.

 

[acewarlock]

Probally just need to reseat the original card. Cheap quality on the contacts they use these days.