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MGCP, H.323, SIP

guys can someone please explain the difference between these protocols i am a new bee to iptel.....whats is the main diff and what is the purpose that we will select h.323 over mgcp or sip.....thanks guys in advance

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Re: MGCP, H.323, SIP


MGCP is a master slave protocol model. With MGCP, CCM has abolute control of the voice gateways. Your q931 signals are backhauled to CCM. MGCP is of best choice when you need the following

1. Centralize your dial-peers. Usually you dont need to define any dial-peer in the gateway as only your route pattern in CCM is needed.

2. When you need to use QSIG protocol, especially when integrating CCM with PBX

3. This follows to point 1. Ease of dial-peer administration.

With MGCP, you Need to Note the following

1. Use Voice-translation rules on the gateway. So if you need to configure xlation rules, then it may not be the best option.

2. For SRST, you will need to manually create all your required dial-peers, otherwise your users will not be able to dial out during SRST.

3. With MGCP, if you have disparate codecs in your network then you will need to use a XCODER..

4. You cannot use H.323 gatekeepers


5. It does not support Caller-ID with FXO ports.

H.323 is a peer to peer protocol. The gateway is very intelligent and can make call routing decision on its own. It is usually more demanding to define all your required dial-peers on the gateway.

However H.323 offer a lot more flexibility in terms of defining voice translation rules, the use of gatekeepers for CAC and centralized dial-plan management.

With H.323 in SRST, you do not need to define any additional dial-peers, because they have already been defined.

H.323 also support Multiple Codecs, hence you may not need Xcoders with the gateway.


SIP is session based protocol. It is relatively new compared to the other 2 protocols. SIP is used for presence based applications, such as Cisco CUPS, Microsoft OCS. SIP is also becoming popular with service providers with use in IP-IP gateways.

SIP use is very broad, eg you can use SIP trunks with CME and CCM..ect


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Re: MGCP, H.323, SIP

The breakdown:

H323 is the most reliable and vetted protocol, and you will have greater interoperability

H323 also requires for you to enable your entire dial plan on every device. If you have a simple dial plan, this is a good choice.

MGCP is good for a configure-and-forget configuration. It's not quite as stable, but you won't need to change it (or understand it) nearly as well. All of the power and configuration is done on CUCM. It limits you from doing some things, at the expense of how easy it is to configure.

SIP is the next H323. A lot of new 3rd party devices are SIP only, as well as SIP trunks. When it eventually comes around, switching your trunks around will be more harmless.




Re: MGCP, H.323, SIP

Hi Guys, please let me ask you something, can I have MGCP and H323 running in the same GW (2650XM-4FXS), if do, what dial plan will be taken first: My MGCP controlled by my CCM dial plan or my h323 VOip Dial-peers.



Re: MGCP, H.323, SIP

Hi David,

If it's a PRI it will automatically choose MGCP first. You use the "ccm fallback-mgcp" command to fallback to H323.

If you have POTS (FXO/FXS), it will choose the first pots dial peer in your config, so make sure it is MGCP. With this type of configuration, you can just put a destination-pattern on the dial peer and have a 2-for-1 configuration.



Re: MGCP, H.323, SIP

Hi Nick, thanks for your answer, always the right point.

Best regards.


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