faqs.org - Internet FAQ Archives

RFC 3529 - Using Extensible Markup Language-Remote Procedure Cal


Or Display the document by number




Network Working Group                                          W. Harold
Request for Comments: 3529                                           IBM
Category: Experimental                                        April 2003

       Using Extensible Markup Language-Remote Procedure Calling
        (XML-RPC) in Blocks Extensible Exchange Protocol (BEEP)

Status of this Memo

   This memo defines an Experimental Protocol for the Internet
   community.  It does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

   XML-RPC is an Extensible Markup Language-Remote Procedure Calling
   protocol that works over the Internet.  It defines an XML format for
   messages that are transfered between clients and servers using HTTP.
   An XML-RPC message encodes either a procedure to be invoked by the
   server, along with the parameters to use in the invocation, or the
   result of an invocation.  Procedure parameters and results can be
   scalars, numbers, strings, dates, etc.; they can also be complex
   record and list structures.

   This document specifies a how to use the Blocks Extensible Exchange
   Protocol (BEEP) to transfer messages encoded in the XML-RPC format
   between clients and servers.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  BEEP Profile Identification  . . . . . . . . . . . . . . . .  2
       2.1  Profile  Initialization . . . . . . . . . . . . . . . .  3
   3.  XML-RPC Message Packages . . . . . . . . . . . . . . . . . .  4
   4.  XML-RPC Message Exchange . . . . . . . . . . . . . . . . . .  5
   5.  URL Schemes  . . . . . . . . . . . . . . . . . . . . . . . .  5
       5.1  The xmlrpc.beep URL Scheme. . . . . . . . . . . . . . .  5
            5.1.1 Resolving IP/TCP Address  Information . . . . . .  6
       5.2  The xmlrpc.beeps URL Scheme . . . . . . . . . . . . . .  7
   6.  Initial Registrations  . . . . . . . . . . . . . . . . . . .  9
       6.1  Registration: The XML-RPC Profile . . . . . . . . . . .  9
       6.2  Registration: The xmlrpc.beep URL Scheme. . . . . . . .  9

       6.3  Registration: The xmlrpc.beeps URL Scheme . . . . . . . 10
       6.4  Registration: The System (Well-Known) TCP port number
            for XML-RPC over BEEP . . . . . . . . . . . . . . . . . 10
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . 11
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . 11
   Appendix
   A. Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . 13
   B. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14
   Full Copyright Statement . . . . . . . . . . . . . . . . . . . . 15

1. Introduction

   This memo specifies how messages encoded in the XML-RPC [1] format
   are transmitted using a BEEP profile [2].

   Throughout this memo, the terms "request" and "response" refer to the
   "methodCall" and "methodResponse" elements defined by the XML-RPC
   specification [1].  Further the terms "peer", "client", "server", and
   "one-to-one" are used in the context of BEEP.  In particular,
   Sections 2.1 and 2.1.1 of [2] discuss BEEP roles and exchange styles.

2. BEEP Profile Identification

   The BEEP profile for XML-RPC is identified as

      http://iana.org/beep/transient/xmlrpc

   in the BEEP "profile" element during channel creation.

   In BEEP, when the first channel is successfully created, the
   "serverName" attribute in the "start" element identifies the "virtual
   host" associated with the peer acting in the server role, e.g.,

      <start number='1' serverName='stateserver.example.com'>
          <profile uri='http://iana.org/beep/transient/xmlrpc' />
      </start>

   The "serverName" attribute is analogous to HTTP's "Host" request-
   header field (c.f., Section 14.23 of [3]).

   There are two states in the BEEP profile for XML-RPC, "boot", the
   profile's initial state, and "ready":

   o  In the "boot" state, the peer requesting the creation of the
      channel sends a "bootmsg" (either during channel initialization or
      in a "MSG" message).

      *  If the other peer sends a "bootrpy" (either during channel
         initialization or in a "RPY" message), then the "ready" state
         is entered

      *  Otherwise, the other peer sends an "error" (either during
         channel initialization or in a "ERR" message), and no state
         change occurs.

   o  In the "ready" state, the initiating peer begins an XML-RPC
      message pattern by sending a "MSG" message containing a request.
      The other peer completes the message pattern by sending back a
      "RPY" message containing a response.

2.1 Profile Initialization

   The boot message is used to identify the resource accessed by the
   channel bound to the BEEP profile for XML-RPC.

   The DTD syntax for the boot message and its response are:

      <!ELEMENT bootmsg     EMPTY>
      <!ATTLIST bootmsg
                resource    CDATA             #REQUIRED>

      <!ELEMENT bootrpy     EMPTY>

   The boot message contains a single mandatory attribute: "resource",
   which is analagous to HTTP's "abs_path" Request-URI parameter (c.f.,
   Section 5.1.2 of [3])

   If the peer acting in the server role recognizes the requested
   resource, it replies with a boot response.  Otherwise, if the boot
   message is improperly formed, or if the requested resource isn't
   recognized, the peer acting in the server role replies with an error
   message (c.f., Section 7.1 of [2]).

   Typically, the boot message and its response are exchanged during
   channel initialization (c.f., Section 2.3.1.2 of [2]).

   For example, here the boot message and its response are exchanged
   during channel initialization:

      C: <start number='1' serverName='stateserver.example.com'>
      C:     <profile uri='http://iana.org/beep/transient/xmlrpc'>
      C:         <![CDATA[<bootmsg resource='/NumberToName' />]]>
      C:     </profile>
      C: </start>

      S: <profile uri='http://iana.org/beep/transient/xmlrpc'>
      S:     <![CDATA[<bootrpy />]]>
      S: </profile>

   The channel bound to the BEEP profile for XML-RPC is now in the
   "ready" state.

   Alternatively, here is an example in which the boot exchange is
   unsuccessful:

      C: <start number='1' serverName='stateserver.example.com'>
      C:     <profile uri='http://iana.org/beep/transient/xmlrpc'>
      C:         <![CDATA[<bootmsg resource='/NameToCapital' />]]>
      C:     </profile>
      C: </start>

      S: <profile uri='http://iana.org/beep/transient/xmlrpc'>
      S:     <![CDATA[<error code='550'>resource not
      S:                                supported</error>]]>
      S: </profile>

   Although the channel was created successfully, it remains in the
   "boot" state.

3. XML-RPC Message Packages

   The BEEP profile for XML-RPC transmits requests and responses encoded
   as UTF-8 using the media type "application/xml" [4], e.g.,

      I: MSG 1 1 . 0 364
      I: Content-Type: application/xml
      I:
      I: <?xml version="1.0"?>
      I:   <methodCall>
      I:     <methodName>examples.getStateName</methodName>
      I:     <params>
      I:       <param>
      I:         <value><i4>41</i4></value>
      I:       </param>

      I:     </params>
      I:   </methodCall>
      I: END

   and its associated response

      L: RPY 1 1 . 201 100
      L: Content-Type: application/xml
      L:
      L: <?xml version="1.0"?>
      L:   <methodResponse>
      L:     <params>
      L:       <param>
      L:         <value><string>South Dakota</string></value>
      L:       </param>
      L:     </params>
      L:   </methodRespose>
      L: END

4. XML-RPC Message Exchange

   A request/response exchange involves sending a request, which results
   in a response being returned.

   The BEEP profile for XML-RPC achieves this using a one-to-one
   exchange, in which the client sends a "MSG" message containing an
   request, and the server sends back a "RPY" message containing an
   response.

   The BEEP profile for XML-RPC does not use the "ERR" message for XML-
   RPC faults when performing one-to-one exchanges.  Whatever response
   is generated by the server is always returned in the "RPY" message.

5. URL Schemes

   This memo defines two URL schemes, "xmlrpc.beep" and "xmlrpc.beeps",
   which identify the use of XML-RPC over BEEP over TCP.  Note that, at
   present, a "generic" URL scheme for XML-RPC is not defined.

5.1 The xmlrpc.beep URL Scheme

   The "xmlrpc.beep" URL scheme uses the "generic URI" syntax defined in
   Section 3 of [5], specifically:

   o  the value "xmlrpc.beep" is used for the scheme component; and,

   o  the server-based naming authority defined in Section 3.2.2 of [5]
      is used for the authority component.

   o  the path component maps to the "resource" component of the boot
      message sent during profile initialization (if absent, it defaults
      to "/").

   The values of both the scheme and authority components are case-
   insensitive.

   For example, the URL

      xmlrpc.beep://stateserver.example.com/NumberToName

   might result in the example shown in Section 2.1.

5.1.1 Resolving IP/TCP Address Information

   The "xmlrpc.beep" URL scheme indicates the use of the BEEP profile
   for XML-RPC running over TCP/IP.

   If the authority component contains a domain name and a port number,
   e.g.,

      xmlrpc.beep://stateserver.example.com:1026

   then the DNS is queried for the A RRs corresponding to the domain
   name, and the port number is used directly.

   If the authority component contains a domain name and no port number,
   e.g.,

      xmlrpc.beep://stateserver.example.com

   the SRV algorithm [6] is used with a service parameter of "xmlrpc-
   beep" and a protocol parameter of "tcp" to determine the IP/TCP
   addressing information.  If no appropriate SRV RRs are found (e.g.,
   for "_xmlrpc-beep._tcp.stateserver.example.com"), then the DNS is
   queried for the A RRs corresponding to the domain name and the port
   number used is assigned by the IANA for the registration in Section
   6.4.

   If the authority component contains an IP address, e.g.,

      xmlrpc.beep://10.0.0.2:1026

   then the DNS is not queried, and the IP address is used directly.  If
   a port number is present, it is used directly; otherwise, the port
   number used is assigned by the IANA for the registration in Section
   6.4.

   While the use of literal IPv6 addresses in URLs is discouraged, if a
   literal IPv6 address is used in a "xmlrpc.beep" URL, it must conform
   to the syntax specified in [7].

5.2 The xmlrpc.beeps URL Scheme

   The "xmlrpc.beeps" URL scheme is identical, in all ways, to the
   "xmlrpc.beep" URL scheme specified in Section 5.1, with the exception
   that prior to starting the BEEP profile for XML-RPC, the BEEP session
   must be tuned for privacy.  In particular, note that both URL schemes
   use the identical algorithms and parameters for address resolution as
   specified in Section 5.1.1 (e.g., the same service name for SRV
   lookups, the same port number for TCP, and so on).

   There are two ways to perform privacy tuning on a BEEP session,
   either:

   o  a transport security profile may be successfully started; or,

   o  a user authentication profile that supports transport security may
      be successfully started.

   In either case the client must present the authority component of the
   URL in the "serverName" attribute of the "start" element it uses to
   tune the session for privacy.

   When TLS is used for privacy the client must verify that the
   authority component of the URL matches the server's identity as
   presented in the server's certificate.  Section 2.4 of [9] describes
   the matching process.

   For the URL:

      xmlrpc.beeps://stateserver.example.com/NumberToName

   the whole process might look like:

       S: <wait for incoming connection @ stateserver.example.com>
       C: <open connection to stateserver.example.com>
       C: RPY 0 0 . 0 52
       C: Content-Type: application/xml
       C:
       C: <greeting />
       C: END
       S: RPY 0 0 . 0 110
       S: Content-Type: application/xml
       S:
       S: <greeting>

       S:   <profile uri='http://iana.org/beep/TLS' />
       S:   <profile uri='http://iana.org/beep/SASL/DIGEST-MD5' />
       S: </greeting>
       S: END
       C: MSG 0 1 . 52 158
       C: Content-Type: application/xml
       C:
       C: <start number='1' serverName='stateserver.example.com'>
       C:   <profile uri='http://iana.org/beep/TLS'>
       C:     <![CDATA[<ready />]]>
       C:   </profile>
       C: </start>
       C: END
       S: RPY 0 1 . 110 121
       S: Content-Type: application/xml
       S:
       S: <profile uri='http://iana.org/beep/TLS'>
       S:   <![CDATA[<proceed />]]>
       S: </profile>
       S: END

       ... TLS negotiations ...

       S: RPY 0 0 . 0 88
       S: Content-Type: application/xml
       S:
       S: <greeting>
       S:   <profile uri='http://iana.org/beep/transient/xmlrpc'>
       S: </greeting>
       S: END
       C: RPY 0 0 . 0 52
       C: Content-Type: application/xml
       C:
       C: <greeting />
       C: END

       ... use the server's certificate to verify that it is
           in fact stateserver.example.com ...

       C: MSG 0 1 . 112 211
       C: Content-Type: application/xml
       C:
       C: <start number='3' serverName='stateserver.example.com'>
       C:     <profile uri='http://iana.org/beep/transient/xmlrpc'>
       C:         <![CDATA[<bootmsg resource='/NumberToName' />]]>
       C:     </profile>
       C: </start>
       C: END

       S: RPY 0 2 . 341 402
       S: Content-Type: application/xml
       S:
       S: <profile uri='http://iana.org/beep/transient/xmlrpc'>
       S:     <![CDATA[<bootrpy />]]>
       S: </profile>
       S: END

6. Initial Registrations

6.1 Registration: The XML-RPC Profile

   Profile Identification: http://iana.org/beep/transient/xmlrpc

   Messages exchanged during Channel Creation: bootmsg, bootrpy

   Messages starting one-to-one exchanges: bootmsg, methodCall

   Messages in positive replies: bootrpy, methodResponse

   Messages in negative replies: error

   Messages in one-to-many exchanges: none

   Message Syntax: methodCall, methodResponse as defined in [1]

   Message Semantics: c.f., [1]

   Contact Information: Ward Harold <wharold@us.ibm.com>

6.2 Registration: The xmlrpc.beep URL Scheme

   URL scheme name: xmlrpc.beep

   URL scheme syntax: c.f., Section 5.1

   Character encoding considerations: c.f., the "generic URI" syntax
      defined in Section 3 of [5]

   Intended usage: identifies a XML-RPC resource made available using
      the BEEP profile for XML-RPC

   Applications using this scheme: c.f., "Intended usage", above

   Interoperability considerations: n/a

   Security Considerations: c.f., Section 7

   Relevant Publications: c.f., [1], and [2]

   Contact Information: Ward Harold <wharold@us.ibm.com>

   Author/Change controller: the IESG

6.3 Registration: The xmlrpc.beeps URL Scheme

   URL scheme name: xmlrpc.beeps

   URL scheme syntax: c.f., Section 5.2

   Character encoding considerations: c.f., the "generic URI" syntax
      defined in Section 3 of [5]

   Intended usage: identifies a XML-RPC resource made available using
      the BEEP profile for XML-RPC after the BEEP session has been tuned
      for privacy

   Applications using this scheme: c.f., "Intended usage", above

   Interoperability considerations: n/a

   Security Considerations: c.f., Section 7

   Relevant Publications: c.f., [1], and [2]

   Contact Information: Ward Harold <wharold@us.ibm.com>

   Author/Change controller: the IESG

6.4 Registration: The System (Well-Known) TCP port number for XML-RPC
    over BEEP

   Protocol Number: TCP

   Message Formats, Types, Opcodes, and Sequences: c.f., Section 2.1

   Functions: c.f., [1]

   Use of Broadcast/Multicast: none

   Proposed Name: XML-RPC over BEEP

   Short name: xmlrpc-beep

   Contact Information: Ward Harold <wharold@us.ibm.com>

7. Security Considerations

   Although service provisioning is a policy matter, at a minimum, all
   implementations must provide the following tuning profiles:

   for  authentication: http://iana.org/beep/SASL/DIGEST-MD5

   for confidentiality: http://iana.org/beep/TLS (using the
      TLS_RSA_WITH_3DES_EDE_CBC_SHA cipher)

   for both: http://iana.org/beep/TLS (using the
      TLS_RSA_WITH_3DES_EDE_CBC_SHA cipher supporting client-side
      certificates)

   Further, implementations may choose to offer MIME-based security
   services providing message integrity and confidentiality, such as
   OpenPGP [8] or S/MIME [10].

   Regardless, consult [2]'s Section 9 for a discussion of BEEP-specific
   security issues.

8. References

   [1]  Winer, D., "XML-RPC Specification", January 1999,
        http://www.xmlrpc.com/spec

   [2]  Rose, M., "The Blocks Extensible Exchange Protocol Core", RFC
        3080, March 2001.

   [3]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L.,
        Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol --
        HTTP/1.1", RFC 2616, June 1999.

   [4]  Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC
        3023, January 2001.

   [5]  Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
        Identifiers (URI): Generic Syntax", RFC 2396, August 1998.

   [6]  Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for
        specifying the location of services (DNS SRV)", RFC 2782,
        February 2000.

   [7]  Hinden, R., Carpenter, B. and L. Masinter, "Format for Literal
        IPv6 Addresses in URL's", RFC 2732, December 1999.

   [8]  Elkins, M., Del Torto, D., Levien, R. and T. Roessler, "MIME
        Security with OpenPGP", RFC 3156, August 2001.

   [9]  Newman, C., "Using TLS with IMAP, POP3 and ACAP", RFC 2595, June
        1999.

   [10] Ramsdell, B., "S/MIME Version 3 Message Specification", RFC
        2633, June 1999.

   [11] O'Tuathail, E. and M. Rose, "Using the Simple Object Access
        Protocol (SOAP) in Blocks Extensible Exchange Protocol (BEEP)",
        RFC 3288, June 2002.

Appendix A. Acknowledgements

   This document is based, in part, on Using SOAP in BEEP [11] and the
   author gratefully acknowledges the contributions of Marshall Rose

Appendix B. IANA Considerations

   The IANA has registered the profile specified in Section 6.1, and has
   selected an IANA-specific URI, e.g.,

      http://iana.org/beep/xmlrpc

   The IANA has registered "xmlrpc.beep" and "xmlrpc.beeps" as URL
   schemes, as specified in Section 6.2 and Section 6.3, respectively.
   (See: http://www.iana.org/assignments/uri-schemes)

   The IANA has registered "XML-RPC over BEEP" as a TCP port number
   (602), as specified in Section 6.4.  (See:
   http://www.iana.org/assignments/port-numbers)

Author's Address

   Ward K Harold
   IBM
   11400 Burnet Road
   Austin,  Texas 78759
   US

   Phone: +1 512 838 3622
   EMail: wharold@us.ibm.com

Full Copyright Statement

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

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

 

User Contributions:

Comment about this RFC, ask questions, or add new information about this topic:

CAPTCHA