h323 gatekeepers ?

[fran19422]

Hello, I am trying to understand in what situation you would use a gatekeeper apart from being used between two CM clusters.

For instance, would you use a gatekeeper if you only had CME gateways in multiple cities. Each city had their own set of extension numbers and you wanted to network these cities together ?

In that case, why would you not just install a CUCM to perform exactly the same role ?

Or are gatekeepers simply for networks where there are only CME gateways being used i.e. for whatever reason there is no CUCM to provide central controller functions ?

Thanks for any clarification.

[islam.kamal · Accepted solution]

HI

1- For Gatekeeper is used to control H323 gateways , as you use gatekeeper you can get the below benefits:-

A-E.164 (Phone #) address resolution to IP address and call setup

B-CAC (call admision control) via bandwidth management .

C-Least cost routing .

D-Authentication using Radisu and Tacacs.

2-The call trough GK using g729 is 16 KBPS which save your bandwith over huge netwroks.

3-The GK can be used if you have many CMEs and you need to do call routing between them .Other solution if you have Cucm cluster and many registered H323 gateways and you need to make call routing , GK is the best for H323 management.

4-If you have more than CUCM cluster which are in different location and there is a routing between them you can use intercluster between CUCM without GK , this other solution.

For more information , please find the below links

http://www.cisco.com/en/US/tech/tk1077/technologies_tech_note09186a00800a8928.shtml

http://www.cisco.com/en/US/tech/tk1077/technologies_tech_note09186a00800c5e0d.shtml

Thank you

please rate all useful information

[Andrey Chertolyas · Accepted solution]

Hi,

According to SRND, gatekeepers should be used in multisite model with distributed call processing. If you have several CUCM clusters connected with each other via WAN you can implement gatekepeers in order to provide CAC and to simplify routing. Exactly the same thing for the distributed voice network built on voice gateways with CME.

I am not sure why Kamal have mentioned G729 in context of gatekepeers since they are not processing voice flows, they are dealing with signalling only.

So again, just to clarify: main gatekeeper functions are:

1) To simplify routing in distributed H323 voice network;

2) To provide CAC;

3) To provide AAA using Radius and Tacacs protocols.

As a rule, if you have a simple voice network there is no need to implement gatekeepers.

Kind regards,
Andrew C.