H.320 gateways a MEGACO / ITU

Gary A. Thom gthom at DELTA-INFO.COM
Wed Mar 31 20:08:57 EST 1999

This problem is independent of the type of encoding being used (PER or text). The problem that
you describe is related more to the use of dynamic ports which prevents simple packet filtering.
An h.323 proxy must parse the call signalling and H.245 messages to find the dynamic ip
address/port pair assignments. The h.323 proxy will be required whether the encoding is asn.1 or
text or anything else.


  From: Melinda Shore <shore at ITHACA-VIENNASYS.COM>
  Subject: Re: H.320 gateways a MEGACO / ITU
  Date: Wed, 31 Mar 1999 16:45:05 -0500

> There's a problem in that it makes the signaling channel sufficiently
> complicated to parse that you end up having to put a proxy, or something
> that looks an awful lot like a proxy, on the firewall in order to
> pick up dynamically-allocated address/port tuples.  This has somewhat
> negative architectural implications in that in a multi-firewall
> environment (which is, alas, the norm when traversing multiple
> administrative domains) you end up with tandemed signaling loops.
> The short answer is that IP is supposed to be end-to-end
> and that firewalls create a big disconnect between the IP network
> and the IP telephony application-layer network.
> Melinda

Name   : Gary A. Thom
Company: Delta Information Systems, Inc.
Address: 300 Welsh Rd., Bldg 3
         Horsham, PA 19044 USA
Phone  : +1-215-657-5270         Fax : +1-215-657-5273
E-mail : gthom at delta-info.com

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