Chip, Thanks for the clarification as to how a URL works. Bob -----Original Message----- From: Chip Sharp [mailto:chsharp@CISCO.COM] Sent: Monday, June 19, 2000 1:44 PM To: ITU-SG16@mailbag.cps.intel.com Subject: Re: H.323 URL A few observations on the current proposal for an H.323 URL: URL Registration: If you want to define a new URL (i.e., H323:), please consider if you want a new registration tree for ITU or if you want to use the IETF registration tree. You might want to start an ITU registration tree, or even a ITU-SG16 registration subtree with IANA. See ftp://ftp.isi.edu/in-notes/bcp/bcp35.txt (BCP35) for more info on what I mean. Principle of "least surprise": If you click on the URL above for BCP35 you will probably expect your mail application to open an ftp application and download the file to your computer. If I click on a URL "telnet://foo.bar.com" I'd expect a telnet application to open that would telnet me to "foo.bar.com". I would expect an H.323 URL to do the same thing. For example if I click on the URL "h323:paulej@packetizer.com" given below, I would expect my H.323 application to open and attempt to call Paul using the address given (paulej@packetizer.com). My H.323 app would have to be configured with certain default parameters for operation (e.g., voice call, G.711 codec, etc.) as well as default operation for resolving the name to an IP address (e.g., use DNS to find the gatekeeper based on "packetizer.com" and use the identified gatekeeper to find Paul's IP address based on "paulej"). These may be defined in the H.323 URL definition. If you want H.323 URL to be used ubiquitously by end-users I'd recommend making its operation as simple as possible and as close as possible to other URLs. See Section 2 of ftp://ftp.isi.edu/in-notes/rfc2543.txt for how the SIP URL is defined as an example. email-id: I'm assuming when saying something should be in format defined in RFC822 that you mean the "addr-spec" production as defined in Appendix D of RFC822 since RFC822 also defines all the mail headers used in SMTP. I believe an H.323 URL could be encoded to be consistent with RFC822, but you have to take into account the escaping of special characters (e.g., ":" and "/") as well as semantics. I noticed the ABNF in one of the emails below substantially copies from RFC822 the definition of "addr-spec". If you do this, you might want to check the procedures for copying text from IETF RFCs as defined in A.5. What field to use: IMHO the only field a URL should be put into is the URL-id field. A URL is self-identifying in terms of application (e.g., "mailto:" -> email, "ftp:" -> FTP, "http:" -> HTTP, etc.). Putting a URL into one of the other fields would require careful definition of the interaction of the semantics of the field name and the URL type. Of course, there may be advantages of putting URLs into other fields that I'm not aware of. ABNF reference: To be consistent with other recommendations (e.g., H.248), reference ftp://ftp.isi.edu/in-notes/bcp/rfc2234.txt (RFC2234) for the definition of ABNF instead of RFC822. This is the IETF Standards Track RFC defining ABNF. Also, a nit about the ABNF in TD40 is that RFC2234 (and RFC822) use a "/" instead of "|" to denote a choice. This is a common mistake. KISS principle: Related to principle of least surprise, I'll echo Bob's concern buried in this thread that making the URL too complex (especially at the front end) will minimize its usefulness. A user should have the same level of expectation of what will happen if they click on an H.323 URL as they do for a HTTP URL. Chip At 03:15 AM 6/19/00 -0400, Paul E. Jones wrote:
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Callaghan, Robert