Network Working Group M. Mealling
Request for Comments: 3368 VeriSign, Inc.
Category: Standards Track August 2002

The 'go' URI Scheme for the Common Name Resolution Protocol

Status of this Memo

This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2002). 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.

Table of Contents

1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Syntax Rules . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1 General Syntax . . . . . . . . . . . . . . . . . . . . . . . 3
3.2 ABNF Grammar . . . . . . . . . . . . . . . . . . . . . . . . 3
3.3 Special Cases and Default Values . . . . . . . . . . . . . . 4
3.3.1 If There is Only a Server . . . . . . . . . . . . . . . . . 4
3.3.2 If Server is Empty Then server=localhost . . . . . . . . . . 4
3.3.3 Default Port . . . . . . . . . . . . . . . . . . . . . . . . 4
3.4 Encoding Rules . . . . . . . . . . . . . . . . . . . . . . . 4
4. Transport Independence . . . . . . . . . . . . . . . . . . . 4
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 5
References . . . . . . . . . . . . . . . . . . . . . . . . . 6
A. Registration Template . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . 7
Full Copyright Statement . . . . . . . . . . . . . . . . . . 8

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.

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 RFC2119 [4].

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 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>]

3.2 ABNF Grammar

The full ABNF [2] (certain values are included by reference from RFC
2396 [1]):

cnrp-uri = "go:" (form1 / form2)
form1 = "//" [server] ["?" ((common-name *avpair) / id-req) ]
form2 = common-name *avpair

id-req = "id=" value
avpair = ";" attribute "=" [ type "," ] value

server = // as specified in RFC2396

common-name = *(unreserved escaped)
attribute = *(unreserved escaped)
value = *(unreserved escaped)
type = *(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 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 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.

3.4 Encoding Rules

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.

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 on the CNRP default
port (1096).

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://?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.

6. Security Considerations

In addition to the security considerations inherent in CNRP itself
(see the Security Considerations section of RFC3367 [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.

7. IANA Considerations

The IANA is asked to register the URL registration template found in
Appendix A in accordance with RFC2717 [6].

References

[1] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC2396, August 1998.

[2] Crocker, D., "Augmented BNF for Syntax Specifications: ABNF",
RFC2234, November 1997.

[3] Popp, N., Mealling, M. and M. Moseley, "Common Name Resolution
Protocol (CNRP)", RFC3367, August 2002.

[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC2119, 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, RFC2717, November 1999.

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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