Network Working Group                                         T. Goddard
Internet-Draft                                 ICEsoft Technologies Inc.
Expires: August 13, 2004                               February 13, 2004

                           NETCONF Over SOAP

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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Copyright Notice

   Copyright (C) The Internet Society (2004). All Rights Reserved.


   The device management protocol NETCONF is applicable to a wide range
   of devices in a variety of environments. The emergence of Web
   Services gives one such environment, and is presently characterized
   by the use of SOAP over HTTP.  NETCONF finds many benefits in this
   environment: from the re-use of existing standards, to ease of
   software development, to integration with deployed systems.  Herein,
   we describe a SOAP over HTTP binding that, when used with persistent
   HTTP connections, yields an application protocol sufficient for

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Table of Contents

   1.    Introduction . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.    SOAP Background for NETCONF  . . . . . . . . . . . . . . . .  4
   2.1   Use and Storage of WSDL and XSD  . . . . . . . . . . . . . .  4
   2.2   SOAP over HTTP . . . . . . . . . . . . . . . . . . . . . . .  5
   2.3   HTTP Drawbacks . . . . . . . . . . . . . . . . . . . . . . .  5
   2.4   BCP56: On the Use of HTTP as a Substrate . . . . . . . . . .  6
   2.5   Important HTTP 1.1 Features  . . . . . . . . . . . . . . . .  6
   2.6   SOAP Implementation Considerations . . . . . . . . . . . . .  7
   2.6.1 SOAP Feature Exploitation  . . . . . . . . . . . . . . . . .  7
   2.6.2 SOAP Headers . . . . . . . . . . . . . . . . . . . . . . . .  7
   3.    A SOAP Web Service for NETCONF . . . . . . . . . . . . . . .  8
   3.1   Fundamental Use Case . . . . . . . . . . . . . . . . . . . .  8
   3.2   NETCONF Sessions . . . . . . . . . . . . . . . . . . . . . .  8
   3.3   Capabilities Exchange  . . . . . . . . . . . . . . . . . . .  8
   3.4   A NETCONF/SOAP example . . . . . . . . . . . . . . . . . . .  9
   4.    Security Considerations  . . . . . . . . . . . . . . . . . . 11
   4.1   Integrity, Privacy, and Authentication . . . . . . . . . . . 11
   4.2   Vulnerabilities  . . . . . . . . . . . . . . . . . . . . . . 11
   4.3   Environmental Specifics  . . . . . . . . . . . . . . . . . . 12
         Normative References . . . . . . . . . . . . . . . . . . . . 13
         Informative References . . . . . . . . . . . . . . . . . . . 15
         Author's Address . . . . . . . . . . . . . . . . . . . . . . 15
   A.    WSDL Definitions . . . . . . . . . . . . . . . . . . . . . . 16
   A.1   NETCONF SOAP Binding . . . . . . . . . . . . . . . . . . . . 16
   A.2   Sample Service Definition  . . . . . . . . . . . . . . . . . 17
         Intellectual Property and Copyright Statements . . . . . . . 18

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1. Introduction

   Given the use of XML [2] and the remote procedure call
   characteristics, it is natural to consider a binding of the NETCONF
   [1] operations to a SOAP [3] application protocol. This document
   proposes a binding of this form.

   In general, SOAP over HTTP is a natural application protocol for
   NETCONF, essentially because of the remote procedure call character
   of both, but care must be taken in some cases as HTTP is inherently
   synchronous and client-driven.

   Four basic topics are presented: SOAP specifics of interest to
   NETCONF, specifics on implementing NETCONF as a SOAP-based web
   service, security considerations, and an appendix with functional
   WSDL.  In some sense, the most important part of the document is the
   brief WSDL document presented in the Appendix.  With the right tools,
   the WSDL combined with the base NETCONF XML Schemas provide machine
   readable descriptions sufficient for the development of software
   applications using NETCONF.

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2. SOAP Background for NETCONF

   Why introduce SOAP as yet another wrapper around what is already a
   remote procedure call message?  There are, in fact, both technical
   and practical reasons.  The technical reasons are perhaps less
   compelling, but let's examine them first.

   The use of SOAP does offer a few technical advantages. SOAP is
   fundamentally an XML messaging scheme (which is capable of supporting
   remote procedure call) and it defines a simple message format
   composed of a "header" and a "body" contained within an "envelope".
   The "header" contains meta-information relating to the message, and
   can be used to indicate such things as store-and-forward behaviour or
   transactional characteristics.  In addition, SOAP specifies an
   optional encoding for the "body" of the message. However, this
   encoding is not applicable to NETCONF as one of the goals is to have
   highly readable XML, and SOAP-encoding is optimized instead for ease
   of automated deserialization. These benefits of the SOAP message
   structure are simple, but worthwhile due to the fact that they are
   already standardized.

   It is the practical reasons that truly make SOAP over HTTP an
   interesting choice for device management.  It is not difficult to
   invent a mechanism for exchanging XML messages over TCP, but what is
   difficult is getting that mechanism supported in a wide variety of
   tools and operating systems and having that mechanism understood by a
   great many developers.  SOAP over HTTP (with WSDL) is seeing good
   success at this, and this means that a device management protocol
   making use of these technologies has advantages in being implemented
   and adopted.  Admittedly, there are interoperability problems with
   SOAP and WSDL, but such problems have wide attention and can be
   expected to be resolved.

2.1 Use and Storage of WSDL and XSD

   One of the advantages of using machine readable formats such as Web
   Services Description Language (WSDL) [4] and XML Schemas [5] is that
   they can be used automatically in the software development process.
   With appropriate tools, WSDL and XSD can be used to generate classes
   that act as remote interfaces or application specific data
   structures. Other uses, such as document generation and service
   location, are also common.  A great innovation found with many
   XML-based definition languages is the use of hyperlinks for referring
   to documents containing supporting definitions. For instance, in
   WSDL, the import statement

     <import namespace=""

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    imports the definitions of XML types and elements from the base
   NETCONF schema.  Ideally, the file containing that schema is hosted
   on a web server under the authority of the standards body that
   defined the schema.  In this way, dependent standards can be built up
   over time and all are accessible to automated software tools that
   ensure adherence to the standards. Thus, it will gradually become as
   important for to host documents like

    as the IETF now hosts documents such as

2.2 SOAP over HTTP

   While it is true that SOAP focuses on messages and can be bound to
   different underlying protocols such as HTTP, SMTP, or BEEP, most
   existing SOAP implementations support only HTTP or HTTP/TLS.  For
   this discussion we will assume SOAP over HTTP or HTTP/TLS unless
   otherwise specified. (This also includes applications of IPSec to
   SOAP over HTTP.)

   Note that there are a number of advantages to considering SOAP over
   protocols other than HTTP, as HTTP assigns the very distinct client
   and server roles by connection initiation. This would cause
   difficulties in supporting asynchronous notification and could be
   relieved in many ways by replacing HTTP with BEEP.

2.3 HTTP Drawbacks

   HTTP is not the ideal transport for messaging, but it is adequate for
   the most basic interpretation of "remote procedure call".  HTTP is
   based on a communication pattern whereby the client (which initiates
   the TCP connection) makes a "request" to the server.  The server
   returns a "response" and this process is continued (possibly over a
   persistent connection, as described below).  This matches the basic
   idea of a remote procedure call where the caller invokes a procedure
   on a remote server and waits for the return value.

   Potential criticisms of HTTP could include the following:

   o  server-initiated data flow is awkward

   o  headers are verbose and text-based

   o  idle connections may be closed by intermediate proxies

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   o  data encapsulation must adhere to MIME

   o  bulk transfer relies on stream-based ordering

   In many ways these criticisms are directed at particular compromises
   in the design of HTTP.  As such, they are important to consider, but
   it is not clear that they result in fatal drawbacks for a device
   management protocol.

2.4 BCP56: On the Use of HTTP as a Substrate

   Best Current Practice 56 [9] presents a number of important
   considerations on the use of HTTP in application protocols.  In
   particular, it raises the following concerns:

   o  HTTP may be more complex than is necessary for the application

   o  The use of HTTP may mask the application from some firewalls

   o  A substantially new service should not re-use port 80 as assigned
      to HTTP

   Fundamentally, these concerns lie directly with SOAP over HTTP,
   rather than the application of SOAP over HTTP to NETCONF.  As BCP 56
   indicates, it is debatable whether HTTP is an appropriate protocol
   for SOAP at all, and it is likely that BEEP would be a superior
   protocol for most SOAP applications. Unfortunately, SOAP over HTTP is
   in common use and must be supported if the practical benefits of SOAP
   are to be realized.

   It is possible, however, to respond to the concern on the re-use of
   port 80. A NETCONF SOAP service can be offered on any desired port,
   and it is recommended that a new standard port for SOAP over HTTP, or
   a new standard port for NETCONF over SOAP (over HTTP) be defined.

2.5 Important HTTP 1.1 Features

   HTTP 1.1 [8] includes two important features that provide for
   relatively efficient transport of SOAP messages.  These features are
   "persistent connections" and "chunked transfer-coding".

   Persistent connections allow a single TCP connection to be used
   across multiple HTTP requests. This permits multiple SOAP request/
   response message pairs to be exchanged without the overhead of
   creating a new TCP connection for each request. Given that a single
   stream is used for both requests and responses, it is clear that some
   form of framing is necessary.  For messages whose length is known in
   advance, this is handled by the HTTP header "Content-length".  For

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   messages of dynamic length, "Chunking" is required.

   HTTP "Chunking" or "chunked transfer-coding" allows the sender to
   send an indefinite amount of binary data.  This is accomplished by
   informing the receiver of the size of each "chunk" (substring of the
   data) before the chunk is transmitted.  The last chunk is indicated
   by a chunk of zero length.  Chunking can be effectively used to
   transfer a large XML document where the document is generated on-line
   from a non-XML form in memory.

   In terms of application to SOAP message exchanges, persistent
   connections are clearly important for performance reasons, and are
   particularly important when it is the persistence of authenticated
   connections that is at stake.  When one considers that messages of
   dynamic length are the rule rather than the exception for SOAP
   messages, it is also clear that Chunking is very useful.  In some
   cases it is possible to buffer a SOAP response and determine its
   length before sending, but the storage requirements for this are
   prohibitive for many devices. Together, these two features provide a
   good foundation for device management using SOAP over HTTP.

2.6 SOAP Implementation Considerations

   It is not the goal of this document to cover the SOAP [3]
   specification in detail.  Instead, we provide a few comments that may
   be of interest to an implementor of NETCONF over SOAP.

2.6.1 SOAP Feature Exploitation

   NETCONF over SOAP does not make extensive use of SOAP features.  For
   instance, NETCONF operations are not broken into SOAP message parts,
   and the SOAP header is not used to convey <rpc> metadata.  This is a
   deliberate design decision as it allows the implementor to easily
   provide NETCONF over multiple substrates while handling the messages
   over those different substrates in a common way.

2.6.2 SOAP Headers

   Implementors of NETCONF over SOAP should be aware of the following
   characteristic of SOAP headers: a SOAP header may have the attribute
   "mustUnderstand" and, if so, the recipient must either process the
   header block or not process the SOAP message at all, and instead
   generate a fault.  A "mustUnderstand" header must not be silently

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3. A SOAP Web Service for NETCONF

3.1 Fundamental Use Case

   The fundamental use case for NETCONF over SOAP (NETCONF/SOAP) over
   HTTP is that of a management console ("manager" role) managing one or
   more devices running NETCONF agents ("agent" role).  The manager
   initiates an HTTP connection to an agent and drives the NETCONF
   session via a sequence of SOAP messages over HTTP requests.  When the
   manager closes the HTTP connection, the NETCONF session is also

3.2 NETCONF Sessions

   NETCONF sessions are persistent for both performance and semantic
   reasons.  NETCONF session state contains the following:

   1.  Authentication Information

   2.  Capability Information

   3.  Locks

   4.  Pending Operations

   5.  Operation Sequence Numbers

   Authentication must be maintained throughout a session due to the
   fact that it is expensive to establish. Capability Information is
   maintained so that appropriate operations can be applied during a
   session. Locks are released upon termination of a session as this
   makes the protocol more robust.  Pending operations come and go from
   existence during the normal course of RPC operations. Operation
   sequence numbers provide the small but necessary state information to
   refer to operations during the session.

   In the case of SOAP over HTTP, a NETCONF "session" is supported by an
   HTTP connection with an authenticated user. To support automated
   cleanup, a NETCONF over SOAP session is closed when the HTTP
   connection is closed.

3.3 Capabilities Exchange

   Capabilities exchange, if defined through a NETCONF RPC operation,
   can easily be accommodated in the SOAP binding.

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3.4 A NETCONF/SOAP example

   Since the proposed WSDL (in Appendix A.1) uses document/literal
   encoding, the use of a SOAP header and body has little impact on the
   representation of a NETCONF operation.  This example shows HTTP/1.0
   for simplicity.

   POST /netconf HTTP/1.0
   Content-Type: text/xml; charset=utf-8
   Accept: application/soap+xml, text/*
   Cache-Control: no-cache
   Pragma: no-cache
   Content-Length: 470

   <?xml version="1.0" encoding="UTF-8"?>
       <rpc id="101" xmlns="">
           <config xmlns="">

   The HTTP/1.0 response is also straightforward:

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   HTTP/1.0 200 OK
   Content-Type: text/xml; charset=utf-8

   <?xml version="1.0" encoding="UTF-8"?>
       <rpc-reply id="101" xmlns="">
         <config xmlns="">

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4. Security Considerations

   NETCONF is used to access and modify configuration information, so
   the ability to access this protocol should be limited to users and
   systems that are authorized to view or modify the agent's
   configuration data.

   Because configuration information is sent in both directions, it is
   not sufficient for just the client or user to be authenticated with
   the server.  The identity of the server should also be authenticated
   with the client.

   Configuration data may include sensitive information, such as user
   names or security keys.  So, NETCONF should only be used over
   communications channels that provide strong encryption for data

   If the NETCONF server provides remote access through insecure
   protocols, such as HTTP, care should be taken to prevent execution of
   the NETCONF program when strong user authentication or data privacy
   is not available.

4.1 Integrity, Privacy, and Authentication

   The NETCONF SOAP binding relies on an underlying secure transport for
   integrity and privacy.  Such transports are expected to include TLS
   [12] and IPSec. There are a number of options for authentication
   (some of which are deployment-specific):

   o  within the transport (such as with TLS client certificates)

   o  within HTTP (such as Digest Access Authentication [10])

   o  within SOAP (such as a digital signature in the header [16])

   HTTP and SOAP level authentication can be integrated with RADIUS [13]
   to support remote authentication databases.

4.2 Vulnerabilities

   The above protocols may have various vulnerabilities, and these may
   be inherited by NETCONF/SOAP.

   NETCONF itself may have vulnerabilities due to the fact that an
   authorization model is not currently specified.

   It is important that device capabilities and authorization remain

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   constant for the duration of any outstanding NETCONF session. In the
   case of NETCONF, it is important to consider that device management
   may be taking place over multiple substrates (in addition to SOAP)
   and it is important that the different substrates have a common
   authentication model.

4.3 Environmental Specifics

   Some deployments of NETCONF/SOAP may choose to use HTTP without
   encryption.  This presents vulnerabilities but may be selected for
   deployments involving closed networks or debugging scenarios.

   A device managed by NETCONF may interact (over protocols other than
   NETCONF) with devices managed by other protocols, all of differing
   security.  Each point of entry brings with it a potential

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Normative References

   [1]   Enns, R., "XMLCONF Configuration Protocol",
         draft-enns-xmlconf-spec-00 (work in progress), Feb 2003,

   [2]   Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler,
         "Extensible Markup Language (XML) 1.0 (Second Edition)", W3C
         REC REC-xml-20001006, October 2000, <

   [3]   Box, D., Ehnebuske, D., Kakivaya, G., Layman, A., Mendelsohn,
         N., Nielsen, H., Thatte, S. and D. Winer, "Simple Object Access
         Protocol (SOAP) 1.1", W3C Note NOTE-SOAP-20000508, May 2000,

   [4]   Christensen, E., Curbera, F., Meredith, G. and S. Weerawarana,
         "Web Services Description Language (WSDL) 1.1", W3C Note
         NOTE-wsdl-20010315, March 2001, <

   [5]   Thompson, H., Beech, D., Maloney, M. and N. Mendelsohn, "XML
         Schema Part 1: Structures", W3C Recommendation
         REC-xmlschema-1-20010502, May 2001, <

   [6]   Freed, N. and N. Borenstein, "Multipurpose Internet Mail
         Extensions (MIME) Part One: Format of Internet Message Bodies",
         RFC 2045, November 1996, <>.

   [7]   Freed, N. and N. Borenstein, "Multipurpose Internet Mail
         Extensions (MIME) Part Two: Media Types", RFC 2046, November
         1996, <>.

   [8]   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, <

   [9]   Moore, K., "On the use of HTTP as a Substrate", RFC 3205,
         February 2002, <>.

   [10]  Franks, J., Hallam-Baker, P., Hostetler, J., Leach, P.,
         Luotonen, A., Sink, E. and L. Stewart, "An Extension to HTTP:
         Digest Access Authentication", RFC 2069, January 1997, <http://>.

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   [11]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", RFC 2119, March 1997, <

   [12]  Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A. and
         P. Kocher, "The TLS Protocol Version 1.0", RFC 2246, January
         1999, <>.

   [13]  Rigney, C., Willens, S., Rubens, A. and W. Simpson, "Remote
         Authentication Dial In User Service (RADIUS)", RFC 2865, June
         2000, <>.

   [14]  Rose, M. and D. New, "Reliable Delivery for syslog", RFC 3195,
         November 2001, <>.

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Informative References

   [15]  Barton, J., Nielsen, H. and S. Thatte, "SOAP Messages with
         Attachments", W3C Note NOTE-SOAP-attachments-20001211, Dec
         2000, <

   [16]  Brown, A., Fox, B., Hada, S., LaMacchia, B. and H. Maruyama,
         "SOAP Security Extensions: Digital Signature", W3C Note
         NOTE-SOAP-dsig-20010206, Feb 2001, <

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

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

Author's Address

   Ted Goddard
   ICEsoft Technologies Inc.
   Suite 300, 1717 10th St. NW
   Calgary, AB  T2M 4S2

   Phone: (403) 663-3322

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Appendix A. WSDL Definitions


   The following WSDL document assumes a hypothetical location for the
   NETCONF schema.

   <?xml version="1.0" encoding="UTF-8"?>

     <import namespace=""

     <message name="rpcRequest">
       <part name="in" element="xb:rpc"/>
     <message name="rpcResponse">
       <part name="out" element="xb:rpc-reply"/>

     <portType name="rpcPortType">
       <operation name="rpc">
         <input message="tns:rpcRequest"/>
         <output message="tns:rpcResponse"/>

     <binding name="rpcBinding" type="tns:rpcPortType">
       <SOAP:binding style="document"
       <operation name="rpc">
           <SOAP:body use="literal"
           <SOAP:body use="literal"

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A.2 Sample Service Definition

   The following WSDL document assumes a hypothetical location for the
   NETCONF/SOAP WSDL definitions.  A typical deployment of a device
   manageable via NETCONF/SOAP would provide a service definition
   similar to the following to identify the address of the device.

   <?xml version="1.0" encoding="UTF-8"?>

     <import namespace=""

     <service name="netconf">
       <port name="rpcPort" binding="xs:rpcBinding">
         <SOAP:address location="http://localhost:8080/netconf"/>


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Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
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   The IETF invites any interested party to bring to its attention any
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   this standard. Please address the information to the IETF Executive

Full Copyright Statement

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   This document and the information contained herein is provided on an

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

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