H323

Unanswered Question
Oct 7th, 2013
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  Hello


I would like to have information about H323 and Gatekeeper...Right now I'M  have call manager  and IP phones . I would to autorise H323 on my Firewall.


The call Manager is at my main site wich connected through MPLS  to remote site (with cisco router on every site)


What are the Pre-requisite to use H323 



DO the call Manager is consiered as gatekeeper.


I have several location , do my routers are considered as gatekeepers too.


Wich ports should I allow on my routers and my Firewall to make the H323 works



Thanks by advance  for your help..

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Jorge Armijo Mon, 10/07/2013 - 20:39
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Hello Kamal,


Well, your question has a laaaarge answer.


-Understanding H.323 Gatekeepers

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


One of the main functions of a Gatekeeper is CAC (Call Admission Control). Think about a centralized directory, if a H323 device needs to call a remote site, it will ask to the Gateeper how to call a certain number.



http://www.cisco.com/image/gif/paws/5244/gk-01.gif


-Prerequisites for a H323 Gatekeeper; to have H323 endpoints, could be a Gateway, H323 Phone, H323 Video Endpoint, CUCM with a H323 Trunk to the GK, that's what comes to the top of my head rigth now.


-No, CUCM is not considered as a Gatekeeper, but you can have multiple H323 trunks to remote sites, and all of the sites can route all the calls to CUCM and then CUCM can route the calls accordingly, but I think that ins't a good idea if you have a cluster with many clients; phones, softphones, media resources, etc. At this point, I think you're talking about SME:


-Unified Communications Manager - Session Manager Edition: Session Manager Designs

http://docwiki.cisco.com/wiki/Unified_Communications_Manager_-_Session_Manager_Edition:_Session_Manager_Designs


Session Manager.jpg


-If you have several sites, with several routers, they are not necessarily considered Gatekeepers. That would be part of the design, to consider what is the best deployment model.


-Regarding the TCP/UDP that H323 Gateways/Gatekeepers use:


RAS uses User Datagram Protocol (UDP) ports 1719 (H.225 RAS messages)           and 1718 (multicast gatekeeper discovery).


H.225 call control signaling is used to setup connections between H.323       endpoints. A reliable (TCP) call control channel is created across an IP network       on TCP port 1720


-Mentioned ports are signaling only, meaning the Ports that the protocol itself uses, you have to be aware of the RTP Ports:


http://www.voip-info.org/wiki/view/RTP+Ports


RTP:

UDP ports 16384-32767


I hope my answer will give you a better idea of what are you dealing with



--
Jorge Armijo

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