    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

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           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]).

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       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]).

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       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>

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          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.

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       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.

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       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>

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           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

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           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

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       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>

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    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.

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       [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.

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    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)

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    Author's Address

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

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

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    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
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       The limited permissions granted above are perpetual and will not be
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       This document and the information contained herein is provided on an
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       TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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       HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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    Acknowledgement

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

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