noise during call setup

[Eugene Meyer]

Hi all.

I have a client who is complaining about a loud crackling noise whenever they try to make a call. The noise stops as soon as the person on the other end answers the call and the actual conversation starts between the two parties. So the problem is with he signaling traffic, but Im not sure where to start with this. 

To add confusion, they have one data network, and two voice networks in the office building. Users on the one voice network registers to CM1 and users on the other voice network registers to CM2. This is achieved by using different VLAN's and option 150 (its messy, but makes sense after they explained the reasons behind this). Each voice network has its own voice gateways, but uses the same WAN gateway. The issue is only with phones on voice network 1. All phones on the other voice network seems to be fine and have no crackling noise during call set up.

Phone model is a 79XX series SCCP phone.

[Manish Gogna]

You can check the following:

>> Is the issue dependent on which gateway/trunk is used to send the call out?

>> does it affect any particular phone model or all of them?

>> If you register the phone that is working fine ( registered to CM2 ) to the other CM ( CM1 ), does the problem with the phone go away? Does it make the call go out via a different gateway/trunk?

Most likely the issue is outside CUCM but you need to narrow down to the gateway/link that is causing the issue.

HTH

Manish

[Eugene Meyer]

Hi Manish,

Thanks for your help.

1. It could be gateway dependent, but I cant say for sure since each gateway registers to its own Call Manager (Voice network 1 [faulty network] has a MGCP GW, Voice network 2 has an H323 GW)

2. Its all of the phones on voice network 1 that is affected

3. I have registered a phone from voice network 1 (faulty network) to voice network 2 (not faulty), and the issue was gone. This is only on the one voice network.

The noise starts as soon as you lift the receiver (before even dialing a number) and only stops once the call connects to the other party. Also, on SOME internal calls we dont even get a ring back.

I have attached a simple network diagram to give you a better idea of how the network looks.

At first I thought this is a QoS issue, but considering the network design I doubt this is QoS.

[Manish Gogna]

If the noise starts as soon as you lift the receiver then it must be impacting the internal calls as well? Can you please confirm this because in that case the focus of troubleshooting would be on cucm rather than gateway or network.

HTH

Manish

[Eugene Meyer]

This is on internal calls as well, and as mentioned, in some cases internal calls there arent even ring back.

[Manish Gogna]

Can you post the following from the server to which the phones ( with the issue ) register?

show version active

show status

show hardware

utils core active list

utils diagnose test

Manish

[Mohammed al Baqari]

Hi,

Can you check the config on both CMs for ringback (also called early-media) under SIP Profiles (assuming that they use SIP trunk).

It sounds that one CM is generating local ringback while the other CM is doing voice cut-through and getting ringback from outside.

Let's start with this as its the only possibility I know for problem with CM. Other than this as Manish mentioned, it can be external problem (outside CM).

[Eugene Meyer]

Hi Mohammed,

Thanks for your time. 

There are no SIP trunks between the gateways and Call Mangers yet on either of the two voice networks. I have attached a simple network diagram in my reply to  Manish.

[jaroslavs]

Hello Eugene, 

Have you managed to resolve this issue? Because, I think I have the same problem. Crackling noise during call setup

[jason-mcgee]

Jaroslavs,

Is it limited to one phone or multiple phones?

Jason

[jaroslavs]

Hi Jason, 

The issue is for all phones on the office. 

It happens intermittently. When user dials pstn number, he hears very loud pitching sound along with dial tones. Once call connects, that sound dissappeares.

Call flow: cucm - h323 gateway - pstn.

Calls to pstn from other gatewas are OK. 

[jason-mcgee]

jaroslavs,

What is your pstn set up? PRI/BRI? Analog via a VG 224 or something similar? Are the calls that are going through other gateways in the same physical location? Same service provider? What is the config for the port/gateway causing the issue vs. the config that is not causing issues if they are from the same service provider?

Sorry for all the questions, I want to make sure I completely understand the situation before I throw out a bunch of possibilities.

Jason