Gateway Protocol Migration - H.323 to MGCP

Unanswered Question
Sep 22nd, 2009

I will be upgrading our gateways from 2851 to 3825 and migrating a few of the sites still on H.323 to MGCP. I good feel for both protocols but would like to know if anyone else has done this and what pitfalls to look out for.

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Paolo Bevilacqua Tue, 09/22/2009 - 14:29

I think you will be actually downgrading by changing to MGCP.

H.323 (or SIP) have more features: number manipulation, calling number routing, TCL/IVR scripting, simpler configuration, operates indipentelty from CM for toll-bypass, and much, much more.

MCGP have more cons that pro: confusing and buggy router configuration, contradictory switch to DP based config in SRTs,CME mode, and too many limitations that people realizes only after. The supposed advantages are relly much.

Other people may tell you differently, but the truth is that sophisticated, multi-site installations do not use MGCP.

Nicholas Matthews Tue, 09/22/2009 - 18:19

It's actually much harder to switch from MGCP to H323.

Brief steps:

-Shut down controller, voice port, and serial interface

-Add 'service mgcp' to end of controller, add 'isdn bind l3 ccm' to serial interface

-Add SRST configuration as needed

-Add MGCP gateway in CUCM

-Switch route patterns to point to new MGCP gateway

-Configure SRST reference points as needed

-Confirm that all the routes that the gateway needs to use exist in CUCM as route patterns.

-Confirm all translations, significant digits, and other manipulations

-If you're using any non-standard features, you'll need to check if this a good idea or not. There are quite a bit of feature differences as Paulo noted.

-Confirm existing gateway configuration for fax, input/output attenuation, ISDN switch type, etc in CUCM gateway page

The only case I'll really tell you to avoid MGCP for right now is if you're using G.729br8 for calls over the gateway, or if you're doing MGCP T38 fax. Both have severe problems at the moment.


Paolo Bevilacqua Wed, 09/23/2009 - 04:23

Or when you want QSIG Progress messages to be handled correctly... or if you want MGCP not to mess around with your configuration in an unpredictable manner... the list is a bit longer than that.

Nicholas Matthews Wed, 09/23/2009 - 12:35

The trick to MGCP is getting your working configuration and typing "no ccm config".

Haven't had many problems with QSIG, not more than anything else. I probably don't work with it as often as you might. I think most of them can get fixed, but the solution often requires changing some things you wouldn't expect.


Paolo Bevilacqua Wed, 09/23/2009 - 12:51

Call progress messages with busy PI in QSIG / MGCP, CM hangs-up with as "normal call termination" and user is never give a chance to use "callback on busy". That from a recent thread and related loud complaining.

To be totally honest another thread reported the very same issue with sip on the ISR (no cm).

Nicholas Matthews Wed, 09/23/2009 - 13:40

We're actually fixing that stuff in SIP from what I understand for some other various issues.

I could see that being a problem - just never run into it. I think the busy tone as a progress message is a European thing?

I understand MGCP if you have a simple deployment - maintaining a dial plan on all of your devices can be kind of a pain. I suppose you have to do it for SRST. Fact of the matter is that so many people use it because they don't have to do any gateway configuration.




This Discussion