Echo On TDM Calls - card not there

[mitelmitel]

I have echo cancellation cards for all our systems except for one.

We are getting intermittent echo.

This is the card config on the 3300 that hasnt got one:- is an echo canceller card needed?

1
1, 1
2
T1/E1 W/DUAL INBAND LOOPBACK

2
--
--
--

3
--
--
--

4
--
--
--

5
--
--
--

6
47, 6
0
4 SHARC 21161 DSP

7
94, 6
2
4 SHARC 21363 DSP

 

[M1tel]

Depends on the part number some are built in

 

[IrwinMFletcher]

If you have intermittent echo, then you have echo cancellers. If you didn't have any, you couldn't even make an IP to TDM call.

Most likely you have a base MXe, which uses two of the 363 DSPs for echo cancelling. Do a DumpDspBootInfo and it should show you.

As for why the echo? What type of sets/lines are you calling? Basically, what is your setup?

 

[mitelmitel]

MXe Server [user gateway]

2 x MXe's for O/G.
1 x MXe's for I/C

60 channel on each O/G system.

120 Channels on I/C system.

2 x O/G systems connected to a network providers box that converts ISDN30 to IP which is connected to an Extreme switch and then fibre.

1 x I/C system is connected to a separate box that connected to same extreme switch and same fibre.

Echo has only been evident intermittently on O/G calls.

All internal calls are fine [and a lot of internal calls are made].

 

[IrwinMFletcher]

If I get what you are saying, let's take a typical call. I have an IP set making an O/G call, I call through the MXe, which will convert it to TDM, out the ISDN trunk to the network box, that converts it back to IP, and eventually out to the PSTN.

The echo in this case would most likely be generated at the IP/PSTN interface, ie, within the network box. Easiest way to prove it is with tests calls from an ONS set off of the MXe.

Btw, you mentioned though that you don't have any ECs on the MXe boxes. The base MXe can't do 120 or even 60 channels of E2T without one of those cards. 60 or 120 USERS, yes, but not E2T channels.

 

[mitelmitel]

The problem is that it is very intermittent so we would have to hammer the ons calls I suppose. I will try.

The system I was enquiring about does not have an additional E2T card [the only system without one]. It has 60 channels [2 x ISDN30] and the following card config:-

Do you think this is below spec?

, 1
2
T1/E1 W/DUAL INBAND LOOPBACK

2
--
--
--

3
--
--
--

4
--
--
--

5
--
--
--

6
47, 6
0
4 SHARC 21161 DSP

7
94, 6
2
4 SHARC 21363 DSP

 

[IrwinMFletcher]

I don't have access to the Eng Guidelines right now, but if you do, look for the number of ECs supplied by a single 21363 DSP. I recall that the 21161 can do 10, I would be surprised if the 21363 could do 30, which is what you would need to guarantee 60 TDM trunks. Keep in mind that this isn't itself your problem. If you were running into the channel limit problems, you would have call failures, not intermittent echo.

Thinking about it some more, the ONS test won't nec prove anything unless there is a lot of echo. The echo may be small enough that you need the extra 60-80ms of delay that IP introduces to hear it. Can you trace any calls off of the network box? Port mirror any of the ports? That might be easier.

 

[mitelmitel]

I'll get hold of the Eng Guidelines.

I have had reports of calls cutting out mid call, also on call setup, also have some trunks stuck in releasing state. When I busy them and attempt to RTS them ESM locks up which means the controller needs a reboot [happened to all 3 trunking gateways].

 

[IrwinMFletcher]

Calls cutting out mid-call would be network related, on call setup could be a lack of resources (logs would tell).

 

[mitelmitel]

I recall that the 21161 can do 10, I would be surprised if the 21363 could do 30"

Surely that will total only 40 channels [if a 21363 was a 30 EC]

I think we are under resourced.

Does an additonal E2T card have inbuilt EC?

 

[IrwinMFletcher]

You mis-understood, a single 21161 can do 10, you have 4 of them, and 4 21363's.

 

[mitelmitel]

Ah, sorry I missed out the number of cards on my pasted info!