The two goals of the CNRP [3] URI [1] are to identify both a specific
common-name record at a specific server and to identify a possibly
dynamic query or entry point into the query process. Since CNRP
requires that the ID be a core query term, these two cases can be
generalized down to simply specifying a query that contains only the
ID of the item.
On first glance it would seem a simple enough exercise to
canonicalize the XML encoded query and then insert it into the query
portion of the URL. The problem here is that, due to the encoding
rules, any remotely complex query will quickly blow out the URI
length limitations. The suggested solution is to provide a
simplified query syntax that is a subset of what is available via the
XML.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [4].
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RFC 3368 CNRP URI Specification August 2002
The CNRP URI comes in two forms. The first form is for talking to a
specific server. The second form is for expressing a query that is
meant to be sent to several different CNRP services. The following
two examples are for pedagogical purposes only. The complete ABNF
grammar in Section 3.2 is the only authoritative syntax definition.
go://[<host>]?[<common-name>]*[;<attribute>=[<type>,]<value>]
and
go:<common-name>*[;<attribute>=[<type>,]<value>]
In the case where the CNRP URI contains only the server production
then the URI identifies a given CNRP server, not any particular query
that is to be done. A client can assume that this server will at
least answer the 'servicequery' request.
CNRP's well known HTTP transport port is 1096. If the port value
portion of the server production is not specified then port 1096
SHOULD be used if the client has no prior knowledge about other ports
or transports that the service may support.
The common-name, query parameters, and parameter values must be
encoded using the UTF-8 encoding scheme [5], and any octet that is
not one of the permitted characters per the above grammar MUST
instead be represented by a "%" followed by two characters from the
<hex> character set above. The two characters give the hexadecimal
representation of that octet.
As stated in the CNRP protocol specification [3], CNRP is allowed to
be expressed over multiple transport protocols with HTTP being
mandatory to implement. In the case where a client attempts to
resolve a CNRP URI and it knows nothing about the service being
referenced in that URI, then it SHOULD use HTTP on the CNRP default
port (1096).
go:Mercedes%20Benz
This example shows a general query for the common-name "Mercedes
Benz". The intent is that the query should be packaged with any
client provided defaults and sent to the one or more services that
the client has configured to ask.
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RFC 3368 CNRP URI Specification August 2002
go://?Mercedes%20Benz
This example shows a general query for the common-name "Mercedes
Benz" that is sent to the server running on the 'localhost'.
go://cnrp.foo.com?Mercedes%20Benz;geography=US-ga
This example shows a query for the common-name "Mercedes Benz" in
the geographic area "US-ga" which should be sent to the server
found at cnrp.foo.com.
go://cnrp.foo.org?Martin%20J.%20D%C3%BCrst
This example includes a UTF-8 character encoded using hex
escaping. The value encoded is a u-umlaut (a 'u' with two dots
over it). This simple query is sent to a server found at
cnrp.foo.org with no parameters.
go://cnrp.foo.com?id=5432345
Here only an id is given which means that his example points
directly at a particular common-name record on a particular
server. This example would probably be found in a link on a web
page of some type.
In addition to the security considerations inherent in CNRP itself
(see the Security Considerations section of RFC 3367 [3]), the URI
mechanism can also be used to retrieve a URI identifying some other
site by including just the ID and not the common-name being linked
to. I.e., the user may think he/she is being shown the URI currently
mapped to the "BMW" common-name but in the case where only the ID is
used the actual common-name is not part of the URI, thus making it
possible to use a CNRP URI without knowing which common-name it is
referring to.
The IANA is asked to register the URL registration template found in
Appendix A in accordance with RFC 2717 [6].
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RFC 3368 CNRP URI Specification August 2002
References
[1] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
[2] Crocker, D., "Augmented BNF for Syntax Specifications: ABNF",
RFC 2234, November 1997.
[3] Popp, N., Mealling, M. and M. Moseley, "Common Name Resolution
Protocol (CNRP)", RFC 3367, August 2002.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[5] The Unicode Consortium, "The Unicode Standard, Version 2.0:
Appendix A.2", ISBN 0-201-48345-9, January 1988.
[6] Petke, R. and I. King, "Registration Procedures for URL Scheme
Names", BCP 35, RFC 2717, November 1999.
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RFC 3368 CNRP URI Specification August 2002
Appendix A. Registration Template
URL scheme name: go
URL scheme syntax: Section 3.2
Character encoding considerations: Section 3.4
Intended usage: Section 1
Applications and/or protocols which use this scheme: [3]
Interoperability considerations: None not specified in [3]
Security considerations: Section 6
Relevant publications: [3]
Contact: CNRP Working Group
Author/Change Controller: IESG
Author's Address
Michael Mealling
VeriSign, Inc.
21345 Ridgetop Circle
Dulles, VA 20170
US
Phone: (703) 742-0400
EMail: michael@verisignlabs.com
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RFC 3368 CNRP URI Specification August 2002
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