MGCP & h.323 Gateways - Pros & Cons?

Unanswered Question
Mar 6th, 2007

I'm just curious about what everyone thinks about the Pros & Cons of MGCP and h.323 Gateways with CCM. I know MGCP Gateways are controlled by CCM and h.323 are all router controlled, but what about stuff like: Are calls dropped when the gateways are reset or will the gateway not reset till all calls are over? Can you run gateway utilization reports on both types of gateways? Any pros and cons would be appreciated! Thanks!

I have this problem too.
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j.huizinga Wed, 03/07/2007 - 00:50


I have done many CM installations and my first choice is always to use MGCP. It just works nice and easy.

Sometimes I must use H323 because I want to intercept the call on the gateway and want to route it through a TCL script which you can't do with MGCP.

About resetting:

H323 resets the local CM configuration and should not affect the gateway.

MGCP resets will affect the gateway but will not bring down active B-channels (depending on IOS and hardware)

MGCP gives you also a very good controll about usage of your lines, with H323 the controll of line usage requires a lot of dial-peer configurations.

I would use MGCP and configuration and ressetting gateways is something you should not do in general during "working" hours.

Resetting a MGCP gateway can cause several minutes of "downtime"


mparekh Wed, 03/07/2007 - 22:12

Use h323 if you are planning on using NFAS which is not supported on MGCP.

Also h323 has better call preservation than MGCP when site falls into SRST mode. Calls are preserved on MGCP gateways only if the connecting circuit is an analog or a T1 CAS circuit, if its a PRI active calls will be dropped because the D-channel is back-hauled to the CM. In h323 you can configure the gateway to preserve the call even as the site falls into SRST so an active call will remain active.

From configuration standpoint i've heard many say MGCP is easier because you don't have to deal with dialpeers. However, if you are going to configure MGCP fallback on the MGCP gateway then you will need to configure dial-peers, so its almost equivalent to configuring a h323 gateway.

Also personally I find troubleshooting on h323 gateways easier than on MGCP gateways.

Kris Thompson Fri, 03/23/2007 - 06:05

An MGCP and T1 CAS warning.

MGCP and T1 CAS can be a challenging combination due to "dual state machine". With MGCP and T1 PRI, the state machine for the channels is in the CallManager. When using MGCP and T1 CAS avoid the following defects:

CSCse94014: ccm-manager config (aka trombone) can drop active T1 CAS calls when resetting a PRI and lead to "OOS - Out of Service Channels" and subsequently provide Dead Air treatment to inbound callers. Watch channel state in Perfmon > Cisco MGCP T1CAS. State should be "2" or "3" (idle or busy).

CSCse48014: MGCP Gateway Failover (registers with other CallManager) can lead to Dead Air (this time without the Perfmon indicator).

Both of these defects have fixes in them and are critical in MGCP T1 CAS enviroments.

CallManager 4.2(3)SR2 and later also provides Channel OOS Recovery Improvements. See:

CSCef58219: CCM will handle incoming calls on OOS T1 CAS channel.

CSCsg60213: CCM will attempt to recovery OOS T1 CAS channels

The "ccm-manager config" feature (trombone) can also overwrite any "voice-port" configuration that may require tuning such as Wink timers that need to be tuned for slow responses (See CSCsh17666).

T1 CAS may be better supported on H.323 if the dial plan allows for it.

msolak Sat, 03/24/2007 - 05:01

a comparison of h.323 and mgcp is documented here:

I think the discusssion about pro & contr. of the protocols is obsolete, because the choice of protocol depends from the requirements of the customer.

An example: if you need QSIG Integration, you have the best interoperability with MGCP.




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