The 'go' URI Scheme for the Common Name Resolution Protocol
RFC 3368

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.

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RFC 3368                CNRP URI Specification               August 2002

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 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 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"

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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.

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   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 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.

7. IANA Considerations

   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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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

Full Copyright Statement

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
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   The limited permissions granted above are perpetual and will not be
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.

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