Fw: Re: the requirements for NAT traversal ofH.323 multimedia systems

Jianfang Li lijianfang at mail.ritt.com.cn
Sat Oct 9 02:54:50 EDT 2004


This is certainly true.  For these reasons, devices behind NATs should
really do H.245 tunneling to avoid the problem.  Alternatively, the NAT ALG
handling the H.323 signaling could just discard the H.245 address received
from, say, the calling party.  In that case, only one side can initiate the
H.245 connection.  Discarding the called side's H.245 address is probably

Anyway, these are just ideas... not necessarily the best solution.
Certainly, this would be a good topic for discussion in Q5/16.  (Copying the
SG16 list.)


> -----Original Message-----
> From: Laurent Barbero [mailto:barbero at col.bsf.alcatel.fr]
> Sent: Thursday, September 30, 2004 5:06 AM
> To: imtch323implementors at mail.imtc.org
> Subject: [imtch323implementors] conflict resolution in simultaneous H245
> connections
> Hi all,
> H323 recommandation says in case of separate H245 connections conflicts
> that the
> GW/Enpoint with the numerically smaller h245address shall close the TCP
> connection it
> opened to keep only one control channel.
> If you have both ends A and B, each in a private network and  H323 NAT in
> the middle,
> and if the address translation gives :
> private H245address of A < translated H245address of B
> private H245address of B < translated H245address of A
> Both H245connections are closed.
> Is there a common implementation workaround except control policy of the
> H323 address
> translation in the NAT to avoid such an issue.
> Thanks in advance.
> Best regards.
> L.B
> ---
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