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:
Francois,
If I want to provide a means of allowing somebody to call me by placing a URL on a web page, I need to provide something that can be resolved universally by H.323 endpoints. Bob mentioned querying a database-- that's certainly a possibility, assuming that that database contains all of the information it needs to resolve an address.
What I am afraid of here is that we are introducing syntax to reach a resource without defining any procedure.
If I see this url: <mailto:h323:paulej@packetizer.com>h323:paulej@packetizer.com
What does that tell the H.323 entity? Is there a GK that is expecting a LRQ, AccessRequest, or is it something else entirely? Perhaps the right solution is to define (in normative text) the procedure for using SRV DNS records to query the packetizer.com domain.
As Pete rightfully pointed out, an H.323 URL would be the perfect place to place conference identifiers for multipoint conferences:
<mailto:h323:conf-server1@packetizer.com;cid:XXXX-XXXX-XXXX-XXXX>h323:conf- server1@packetizer.com;cid:XXXX-XXXX-XXXX-XXXX
I think we need to work on the procedural part of this now. Who is working on that?
Paul
----- Original Message ----- From: <mailto:audet@NORTELNETWORKS.COM>Francois Audet To: <mailto:ITU-SG16@mailbag.cps.intel.com>ITU-SG16@mailbag.cps.intel.com Sent: Friday, June 16, 2000 11:48 AM Subject: Re: H.323 URL
I would agree with Bob here.
Using an H.323 URL for a telephone number would imply that you can only be reached using H.323. Is this you intention?
-----Original Message----- From: Callaghan, Robert
[<mailto:Robert.Callaghan@ICN.SIEMENS.COM>mailto:Robert.Callaghan@ICN.SIEMEN S.COM]
Sent: Friday, June 16, 2000 5:39 AM To: <mailto:ITU-SG16@MAILBAG.INTEL.COM>ITU-SG16@MAILBAG.INTEL.COM Subject: Re: H.323 URL
Paul,
I think that this is getting complicated.
I did not envision the use of the H.323-URL to encompase a telephone number. I only conceede for the purpose of progress.
I saw the H.323-URL to be an identifier that would be used to access a database. The DNS portion would identify the database, the userID would be the entry in the database. The database would then return the necessary information to complete the call. It is highly propable that this information would include an E.164 or PNP address. This is especially true when the call must be ompleted over the SCN.
I saw telephone numbers being defined in the "Tel:" URL defined in RFC2806. This URL covers many of optional fields needed to make an SCN call which are not presently covered in H.323.
If we are to have multiple forms of an H.323 URL, I would prefer to have multi-URL IDs.
Bob
P.S. (By the way, the complex, cover everything, is where the last try at an H.323 URL diaappeared.)
------------------------------------------------------------------ Robert Callaghan Siemens Enterprise Networks Tel: +1.561.923.1756 Fax: +1.561.923.1403 Email: Robert.Callaghan@ICN.Siemens.com ------------------------------------------------------------------
-----Original Message----- From: Paul E. Jones [<mailto:paulej@packetizer.com>mailto:paulej@packetizer.com] Sent: Friday, June 16, 2000 3:11 AM To: Callaghan, Robert; 'Orit Levin' Cc: Mailing list for parties associated with ITU-T Study Group 16 (E-mail) Subject: Re: H.323 URL
Bob,
I'm still surprised that you don't want to see the URL expanded... especially to address party number types. Here is is currently:
H323-URL = "H323:" user ["@" hostport] user = username | phone-number username = *( unreserved | escaped | "&" | "=" | "+" | "$" | "," ) hostport = host [ ":" port ] host = hostname | IPv4address hostname = *( domainlabel "." ) toplabel [ "." ] domainlabel = alphanum | alphanum *( alphanum | "-" ) alphanum toplabel = alpha | alpha *( alphanum | "-" ) alphanum IPv4address = 1*digit "." 1*digit "." 1*digit "." 1*digit port = *digit reserved = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "+" |"$" | "," digits = 1*DIGIT
However, to be useful, information that follows the "h323:" should be something in a form that an H.323 Gatekeeper can resolve. Those things include: dialedDigits h323-ID email-ID partyNumber or one of the transportAddress types.
This seems to be a reasonable syntax:
H323-URL = "H323:" Address Address = AliasAddress / TransportAddress AliasAddress = dialedDigits / h323-ID / email-ID / partyNumber dialedDigits = "dialedDigits=" 1*digit h323-ID = "h323-ID=" 1*OCTET ; UTF-8 string represting the BMPString email-ID = "email-ID=" email-ID-spec partyNumber = e164Number / dataPartyNumber / telexPartyNumber / privateNumber / nationalStandardPartyNumber email-ID-spec = mailbox / group group = phrase ":" [ mailbox ] ";" phrase = 1*word word = atom / quoted-string atom = 1*CHAR ; any CHAR except specials, SPACE and CTLs specials = "(" / ")" / "<" / ">" / "@" ; Must be in quoted- / "," / ";" / ":" / "\" / <"> ; string, to use / "." / "[" / "]" ; within a word. quoted-string = mailbox = addr-spec / phrase route-addr addr-spec = local-part "@" domain local-part = word *("." word) domain = sub-domain *("." sub-domain) sub-domain = domain-ref / domain-literal domain-ref = atom domain-literal = "[" *(dtext / quoted-pair) "]" dtext = 1*CHAR ; Any CHAR excluding "[", "]", "\" & CR, ; & including linear-white-space> linear-white-space = 1*([CRLF] LWSP-char) LWSP-char = SP / HTAB quoted-pair = "\" CHAR phrase = 1*word route-addr = "<" [route] addr-spec ">" route = "@" domain ":" e164Number = "e164Number=" publicTypeOfNumber "," digits digits = 1*(DIGIT / "#" / "*" / ",") publicTypeOfNumber = "unknown" / "internationalStandard" / "nationalNumber" / "networkSpecificNumber" / "subscriberNumber" / / "abbreviatedNumber" dataPartyNumber = "dataPartyNumber=" digits telexPartyNumber= "telexPartyNumber=" digits privatePartyNumber = "privatePartyNumber=" privateTypeOfNumber "," digits privateTypeOfNumber = "unknown" / "level2RegionalNumber" / "level1RegionalNumber" / "pISNSpecificNumber" / "localNumber" / "abbreviatedNumber" TransportAddress = ipAddress / ipSourceRoute / ipxAddress / ip6Address / netBios / nsap / nonStandardAddress ipAddress = ip ":" port ip = 1*DIGIT "." 1*DIGIT "." 1*DIGIT "." 1*DIGIT port = 1*DIGIT ipSourceRoute = ip ":" port "," ip *1("," ip) ";" ("strict" / "loose") ipxAddress = 1*DIGIT ":" 1*DIGIT ":" 1*DIGIT ip6Address = 1*HEXDIGIT 14*(":" [1*HEXDIGIT]) 1*HEXDIGIT HEXDIGIT = DIGIT / "A" / "B" / "C" / "D" / "E" / "F" netBios = ;; and so forth nsap = nonStandardAddress =
Now, there may be an error or two in there, but at least it is more complete and an H.323 system knows how to work with these. (Note I did not address the new V4 alias "mobileIUM")
If we used this grammar, I don't think we would need a lot of strange rules about what you do with the URL. Basically, you take it apart according to its internal parts to form an alias address that a Gatekeeper can resolve.
Paul
----- Original Message ----- From: "Callaghan, Robert" <Robert.Callaghan@icn.siemens.com> To: "'Orit Levin'" <orit@radvision.com>; "'Paul E. Jones'" <paulej@PACKETIZER.COM> Cc: "Mailing list for parties associated with ITU-T Study Group 16 (E-mail)" <ITU-SG16@mailbag.cps.intel.com> Sent: Wednesday, June 14, 2000 3:50 PM Subject: RE: H.323 URL
Orit,
In my opinion, an email-ID alias conforms to RFC-822 and is interpreted according the rules stated in H.225.0. An H.323-URL-ID conforms to TD-40a/Osaka and is interpreted according to the rules stated in TD-40a. An H.323-ID is a character string without any rules of interpretation. I see no need to blend these contexts. All three addressing modes can be use; each in its own context.
However, these are my opinion. Maybe more work is needed in Portland.
Bob
------------------------------------------------------------------ Robert Callaghan Siemens Enterprise Networks Tel: +1.561.923.1756 Fax: +1.561.923.1403 Email: Robert.Callaghan@ICN.Siemens.com ------------------------------------------------------------------
-----Original Message----- From: Orit Levin
[<mailto:orit@radvision.com>mailto:orit@radvision.com]
Sent: Wednesday, June 14, 2000 11:45 AM To: Callaghan, Robert; 'Paul E. Jones' Cc: Mailing list for parties associated with ITU-T Study Group 16 (E-mail) Subject: Re: H.323 URL
Hello Bob and Paul! I don't see backwards compatibility problem, when the URL says explicitly H323-URL. An appropriate change may be to state, that the default meaning of url, encoded into email-ID alias, is according to RFC-822. Now, I feel a need to put a chapter explaining what is the meaning of email URL (apart from its syntax) when used in H.323 Network. There is some explanation in H.225.0 Appendix IV. Do you find it clear and sufficient? Orit Levin RADVision Inc. 575 Corporate Drive Suite 420 Mahwah, NJ 07430 Tel: 1 201 529 4300 (230) Fax: 1 201 529 3516 www.radvision.com orit@radvision.com -----Original Message----- From: Callaghan, Robert <Robert.Callaghan@icn.siemens.com> To: 'Paul E. Jones' <paulej@PACKETIZER.COM>; 'Orit Levin' <orit@radvision.com> Cc: Mailing list for parties associated with ITU-T Study Group 16 (E-mail) <ITU-SG16@mailbag.cps.intel.com> Date: Wednesday, June 14, 2000 9:56 AM Subject: H.323 URL
Paul,
I have a backward compatibility item for you to think about.
TD-40/Osaka states that the H323-URL may be coded into the email-ID for alias address. However, H.225.0 states that the email-ID shall conform to RFC822. This is an exclusionary requirement in that other standards may not be used. Also, Note 4 of the BNF definition of the H323-URL clearly states that that the H323-URL is *not* compatible with RFC822.
Therefor, I propose that the H323-URL cannot be coded into the email-ID for alias address because of compatibility problems.
Bob
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Callaghan, Robert