Remote H.323 RTP Ports

[malibu1979]

Working on a IPO 9.0.1.0 build 845 and I'm have audio issues on a remote H.323 phone. The phone registers fine but sometimes when I go off hook to make a call, there is no system dial tone or audio if I place a call. Per the knowledgebase, I have port 1719 UDP and 1720 TCP, I also have the system configuration correctly. My question is about the RTP port range and the correct way to set it. Per the knowledgebase,

"It is assumed that the domestic router allows all outbound traffic from the home network to pass through and allows all symmetric traffic. That is, if the phone sends RTP/RTCP to a public IP address and port, it will be able to receive RTP/RTCP from that same IP address and port. If this is not the case, the configuration of the user's router to support that is not covered by this documentation."

If I understand correctly, at the user side, RTP ports 49152-53246 need to be opened up and point to the IP address of the H.323 phone? Can I restrict the RTP range and still have a working phone? I thought I also read that a H.323 extn only needs 2 ports, per extn.

Thanks

 

[hairlessupportmonkey]

No on the host side you open those ports.

You can also adjust the range of RTP ports in manager.

I would leave them on default. You can tie down your firewall to accept incoming connections from a range of IP addresses to help with security

ACSS - SME
General Geek

 

[malibu1979]

Thanks for the reply hairlessupportmonkey. So your saying along with forwarding 1719 and 1720 to the IPO, 49152-53246 needs to be forwarded to the IPO as well? Are all 4094 ports really being used?

 

[sizbut]

If that's the range enabled on the IP Office then yes. The two ranges have to match. Not hard.

Stuck in a never ending cycle of file copying.

 

[malibu1979]

Sizbut, I agree it's not hard. Going by what the knowledgebase state "Set the RTP Port Number Range (Remote Extn) range to encompass the port range that should be used for remote H.323 extension RTP and RTCP traffic. The range setup must provide at least 2 ports per extension being supported." it sounds like it could be set up only using a couple ports. Thats what I'm wanting to know, can I set a smaller range (couple ports) and make this work.

 

[vfonseca76]

malibu1979, as I understand, you have a remote IP phone behind a router with the public IP, and you are forwarding ports in your router from the public IP do the internal IP of the phone, is that correct ?

A VoIP call uses 2 IP connections, 1 for control of the call (signaling) and 1 for streaming the audio.
In your case, the call establishes correctly so the signaling part is OK (I think port 1720 is the port for H.225 call setup).

The RTP part, which carries the audio, is more tricky. For any given call, the PBX creates 1 connection from the pool of ports configured, plus the port defined for RTCP (in SIP calls, the RTCP is exchanged in adjacent connection: Ex.port 49152 for call, port 49153 for RTCP)

It's a good practice to make the available port's equal on both sides, but if you limit the ports on the PBX side, you limit the amount of calls it can support simultaneously. So if you don't want to open the full range of ports on the remote, you'll have to negotiate a compromise

My advice: determine how many call's you should have simultaneously on the PBX (worst case scenario) and add 50% and configure that range on the PBX.
Ex.20 call's simultaneously + 50% = 30, so you configure range 49152 - 49182.
Open that range on the remote side, and you should be OK.

Note: all this came mostly from field experience and protocol info, NOT directly or explicitly from the Avaya manuals.

Hope it helps

Vasco

 

[IPGuru]

My advise is if you need more than the 4 remote H323 extns that Avaya provide free of charge then you would be better off connecting a VPN handset through a suitable VPN gateway.
Remote H323 handsets can be flakey depending on the home users ISP (for example they do not work with Virgin media in the UK)

as previously stated the port range can be specified in the IPO so a smaller range can be allocated, this is strongly recommended.


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