Revised H.323 URL document

Orit Levin orit at
Fri Sep 8 15:57:07 EDT 2000

Hello Paul and Bob!
I prepared the following "speech" for the mailing list, but it is definitely better to try to understand each other first...


I hate to disappoint you, but I would strongly disagree with the proposed "mode" terminology.
I will try to explain below, why it does not fit the URL concept.

1. The MAIN purpose of URL is to use the Internet DNS Infrastructure for SERVICE+ADDRESS resolution ACROSS the DOMAINS.
(The use of the "user-only" URL is [just] a possible additional feature.)

2. The H.323 "direct vs. routed" concept specifies the relations between an End Point and ITS Gatekeeper. It is an local policy issue WITHIN their zone.
Today, according to H.323 specification, the real flavor of the operational mode in the DESTINATION zone is UNKNOWN (and irrelevant) to the originator of the call. 
Not mentioning the future possible GK decomposition!...

3. Following the proposed "mode" terminology, I guess, "routed" would mean "LRQ" or "Access Request" and "direct" would mean "Setup". In reality, the LRQ would lead to the "direct call" and the Setup would lead to the "routed call". And how to distinguish between the all three?

4. The INTER-ZONE communication haven't been solidly defined so far. (LRQ ? Annex G?)
The INTER-DOMAIN communication is the subject of H.225.0 Annex G.  
The URL approach is an OPTION for all of the "intra" and "inter" H.323 Zone and H.323 Domain cases.
It may be used as a first lookup, before the LRQ or Annex G are performed.
It may also have an overlapping functionality with LRQ and with very specific PARTS of Annex G.
The relations between the H.323 URL and H.225.0 "Annex G" are very close to those of the SIP-URL and TRIP in a "SIP system". Both have their uses and complement each other.

5. The proposal is to have a possibility to "publish", using the URL, the first procedure, to be issued towards the destination "domain".
By its nature, it is not an issue for standardization. It is a policy of the destination domain, which also is responsible for the URL itself.
The first procedure (i.e. the "method") required for establishing of a specific call across domains/zones can be either of the following:
-    H.225.0 Annex G/AccessRequest
-    H.225.0/LRQ
-    H.225.0/CALL SETUP
Once, the first message is issued towards the destination (which is a result of DNS lookup using the URL), the rest of the procedures are, indeed, very well defined by H.323 and H.225.0 Annex G all together. 

Best Regards,
Orit Levin
RADVision Inc.
575 Corporate Drive Suite 420
Mahwah, NJ 07430
Tel: 1 201 529 4300  (230)
Fax: 1 201 529 3516
orit at
  -----Original Message-----
  From: Callaghan, Robert <Robert.Callaghan at ICN.SIEMENS.COM>
  Date: Thursday, September 07, 2000 8:17 AM
  Subject: Re: Revised H.323 URL document



  I definitely like “mode” as a replacement for “protocol.”  It clearly represents the required procedure without over doing details.


  I think that we got it.





  Robert Callaghan

  Siemens Enterprise Networks

  Tel: +1.561.923.1756              Fax: +1.561.923.1403

  Email:      Robert.Callaghan at



  -----Original Message-----
  From: Paul E. Jones [mailto:paulej at]
  Sent: Wednesday, September 06, 2000 11:20 PM
  To: Robert Callaghan; Orit Levin; ITU-SG16 at
  Subject: Revised H.323 URL document


  Orit, Bob, et al,


  Attached is the revised section covering the syntax of the H.323 URL.  This (I hope) includes all of the changes we have discussed so far.  I am not sure that we settled on the "mode" parameter, but I made the change here in this document-- feedback is welcome.


  Best Regards,


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