Network Working Group M. Mealling
Internet-Draft NSI
Expires: December 15, 2000 June 16, 2000
The 'go' URI Scheme for the Common Name Resolution Protocol
draft-ietf-cnrp-uri-01.txt
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Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract
This document defines a URI scheme, 'go:' to be used with the Common
Name Resolution Protocol. Specifically it lays out the syntactic
components and how those components are used by URI Resolution to
find the available transports for a CNRP service. Care should be
taken with several of the URI components because, while they may
look like components found in other URI schemes, they often do not
act like them. The "go"scheme has more in common with the location
independent "news" scheme than any other URI scheme.
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Table of Contents
1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Syntax Rules . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1 General Syntax . . . . . . . . . . . . . . . . . . . . . . . 5
3.2 ABNF Grammar . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3 Special Cases and Default Values . . . . . . . . . . . . . . 5
3.3.1 If there is only a server . . . . . . . . . . . . . . . . . 5
3.3.2 If server is empty then server=localhost . . . . . . . . . . 6
3.3.3 Default Port . . . . . . . . . . . . . . . . . . . . . . . . 6
3.4 Encoding Rules . . . . . . . . . . . . . . . . . . . . . . . 6
4. Transport Independence . . . . . . . . . . . . . . . . . . . 7
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . 9
References . . . . . . . . . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . 10
A. Registration Template . . . . . . . . . . . . . . . . . . . 11
Full Copyright Statement . . . . . . . . . . . . . . . . . . 12
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1. Goals
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.
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2. Terminology
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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3. Syntax Rules
3.1 General Syntax
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 ABNF is the only
authoritative syntax definition.
go://[<host>]?[<common-name>]*[;<attribute>=<value>]
and
go:<common-name>*[;<attribute>=<value>]
3.2 ABNF Grammar
The full ABNF[2] (certain values are included by reference from
RFC2396[1]):
cnrp-uri = "go:" (form1 / form2)
form1 = "//" [server] ["?" (common-name / id-req) *avpair ]
form2 = common-name *avpair
id-req = "id=" value
avpair = ";" attribute "=" value
server = // as specified in RFC2396
common-name = *(unreserved | escaped)
attribute = *(unreserved | escaped)
value = *(unreserved | escaped)
unreserved = // as specified in RFC2396
escaped = "%" hex hex
hex = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" |
"8" | "9" | "A" | "B" | "C" | "D" | "E" | "F" |
"a" | "b" | "c" | "d" | "e" | "f"
3.3 Special Cases and Default Values
3.3.1 If there is only a server
In the case where the CNRP URI contains only the server production
then the URI identifies a given CNRP server, not any particular
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query that is to be done. A client can assume that this server will
at least answer the 'servicequery' request.
3.3.2 If server is empty then server=localhost
If the 'server' element has no value then its value MUST be assumed
to be "localhost".
3.3.3 Default Port
CNRP's well known port is 1096. If the port value portion of the
server production is not specified then port 1096 MUST be used.
3.4 Encoding Rules
The common-name, query parameters, or its 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.
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4. Transport Independence
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.
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5. Examples
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.
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.w3.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.w3.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.
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6. Security Considerations
In addition to the security considerations inherent in CNRP itself,
the URI mechanism can also be used to redirect to 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 linked to where ever the BMW
common-name currently points 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.
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References
[1] Berners-Lee, T., Fielding, R.T. 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] Moseley, M., Mealling, M. and N. Popp, "CNRP PROTOCOL
SPECIFICATION", Internet-Draft draft-ietf-cnrp-protocol-02,
February 2000.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, BCP 14, March 1997.
[5] The Unicode Consortium, "The Unicode Standard, Version 2.0:
Appendix A.2", ISBN 0-201-48345-9, January 1988.
Author's Address
Michael Mealling
Network Solutions, Inc.
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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
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