H.323 URL Specification (second try)

Callaghan, Robert Robert.Callaghan at icn.siemens.com
Tue Sep 5 10:54:49 EDT 2000

See below.
Robert Callaghan
Siemens Enterprise Networks
Tel: +1.561.923.1756              Fax: +1.561.923.1403
Email:      Robert.Callaghan at ICN.Siemens.com
(0) The use of url means the "address resolution" is done (by the local GK)
using the DNS, not RAS! This is why the "user only" url of H.323, is really
an exceptional case. It is a question, if we want to keep it within the url.
It lets the local (source) GK know, that the "address resolution" procedure
should performed by other, then DNS, means. The "protocol" means: the
signaling H.323 protocol to contact the (next hop towards the) destination,
after the IP address had been resolved.
(0)   I will remove the reference to RAS and expect to see an explicit
description of the procedure in Annex O.  What I would expect is that the
hostport part will resolve to a GK to which LRQ messages are directed.
 [RWC] Now I am confused.  I thought that DNS was used to locate the
resolution server.  Then LRQ(RAS) was used to communicate with that server
to resolve the address of the user.  The server doing the address resolution
may not be involved in the final connections.
(1) I disagree that it is the exception.  I would contend that calling a
specific machine would be the exception.  Sure, one can call and endpoint
directly, but that's not typical.  It is in testing and development
environments, but in production environments, users enter telephone numbers.
Also, I can imagine intranets where the h323 URL might be used.  At work, I
might post a page with "h323:paulej", but I would never post
"h323:@cisco.com".  However, the latter is allowed, of course.  What I do
not want is "h323:paulej@" on a web page.  That's ugly, in my opinion.  I
realize that the SIP folks chose that, but it seems illogical to me.
[RWC] I do not see any relationship between an URL and a telephone number.
If a user enters a telephone number the connection should be established
using either the dialedDigits alias or the partyNumber alias not the URL-id
alias.  For me, the URL user should be a name type structure like in email
users.  This allows for a number as a name but not as a telephone number.  I
do not accept the SIP and ENUM concept where telephone numbers are funny
names with a default domain for DNS.  In fact, I think that this will not
work due to difficulties with administration ownership of telephone numbers.
[RWC]  I do agree that user only will be an exception because it forces the
use of a default domain for DNS.  It is not likely that there will be
universal default domain.
(2) If I provided "h323:@;proto=q931", a device should assume
that it can reach it on the default 1720 port or the default Annex E port
(as described in Annex E).  If, however, I use a different port like
"h323:@;proto=q931", I would say that Annex E is out of the
picture.  That is another reason why I believe the first step to resolution
should be through a Gatekeeper.  The gatekeeper can not only resolve the
address, but also indicate any non-standard ports, including both the TCP
and Annex E transport information.
[RWC] In this case the endpoint that wished to use Annex E must support the
requirement of Annex E that requires the ability to fall back to TCP.
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