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RFC 5730

 Errata 
STD 69
Pages: 67
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Extensible Provisioning Protocol (EPP)

Part 1 of 3, p. 1 to 19
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STD 69 is also:    5731    5732    5733    5734
Obsoletes:    4930


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Network Working Group                                      S. Hollenbeck
Request for Comments: 5730                                VeriSign, Inc.
STD: 69                                                      August 2009
Obsoletes: 4930
Category: Standards Track


                 Extensible Provisioning Protocol (EPP)

Abstract

   This document describes an application-layer client-server protocol
   for the provisioning and management of objects stored in a shared
   central repository.  Specified in XML, the protocol defines generic
   object management operations and an extensible framework that maps
   protocol operations to objects.  This document includes a protocol
   specification, an object mapping template, and an XML media type
   registration.  This document obsoletes RFC 4930.

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) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

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Table of Contents

   1. Introduction ....................................................3
      1.1. Conventions Used in This Document ..........................3
   2. Protocol Description ............................................4
      2.1. Transport Mapping Considerations ...........................7
      2.2. Protocol Identification ....................................8
      2.3. Hello Format ...............................................8
      2.4. Greeting Format ............................................8
      2.5. Command Format ............................................12
      2.6. Response Format ...........................................13
      2.7. Protocol Extension Framework ..............................16
           2.7.1. Protocol Extension .................................16
           2.7.2. Object Extension ...................................17
           2.7.3. Command-Response Extension .........................18
      2.8. Object Identification .....................................18
      2.9. Protocol Commands .........................................19
           2.9.1. Session Management Commands ........................19
                  2.9.1.1. EPP <login> Command .......................20
                  2.9.1.2. EPP <logout> Command ......................22
           2.9.2. Query Commands .....................................23
                  2.9.2.1. EPP <check> Command .......................23
                  2.9.2.2. EPP <info> Command ........................25
                  2.9.2.3. EPP <poll> Command ........................26
                  2.9.2.4. EPP <transfer> Query Command ..............30
           2.9.3. Object Transform Commands ..........................31
                  2.9.3.1. EPP <create> Command ......................32
                  2.9.3.2. EPP <delete> Command ......................33
                  2.9.3.3. EPP <renew> Command .......................34
                  2.9.3.4. EPP <transfer> Command ....................35
                  2.9.3.5. EPP <update> Command ......................38
   3. Result Codes ...................................................39
   4. Formal Syntax ..................................................45
      4.1. Base Schema ...............................................45
      4.2. Shared Structure Schema ...................................56
   5. Internationalization Considerations ............................59
   6. IANA Considerations ............................................59
   7. Security Considerations ........................................60
   8. Acknowledgements ...............................................61
   9. References .....................................................62
      9.1. Normative References ......................................62
      9.2. Informative References ....................................62
   Appendix A.  Object Mapping Template ..............................64
   Appendix B.  Media Type Registration: application/epp+xml .........66
   Appendix C.  Changes from RFC 4930 ................................67

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1.  Introduction

   This document describes specifications for the Extensible
   Provisioning Protocol (EPP) version 1.0, an XML text protocol that
   permits multiple service providers to perform object-provisioning
   operations using a shared central object repository.  EPP is
   specified using the Extensible Markup Language (XML) 1.0 as described
   in [W3C.REC-xml-20040204] and XML Schema notation as described in
   [W3C.REC-xmlschema-1-20041028] and [W3C.REC-xmlschema-2-20041028].
   EPP meets and exceeds the requirements for a generic registry
   registrar protocol as described in [RFC3375].  This document
   obsoletes RFC 4930 [RFC4930].

   EPP content is identified by MIME media type application/epp+xml.
   Registration information for this media type is included in an
   appendix to this document.

   EPP is intended for use in diverse operating environments where
   transport and security requirements vary greatly.  It is unlikely
   that a single transport or security specification will meet the needs
   of all anticipated operators, so EPP was designed for use in a
   layered protocol environment.  Bindings to specific transport and
   security protocols are outside the scope of this specification.

   The original motivation for this protocol was to provide a standard
   Internet domain name registration protocol for use between domain
   name registrars and domain name registries.  This protocol provides a
   means of interaction between a registrar's applications and registry
   applications.  It is expected that this protocol will have additional
   uses beyond domain name registration.

   XML is case sensitive.  Unless stated otherwise, XML specifications
   and examples provided in this document MUST be interpreted in the
   character case presented to develop a conforming implementation.

1.1.  Conventions Used in This Document

   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].

   In examples, "C:" represents lines sent by a protocol client and "S:"
   represents lines returned by a protocol server.  Indentation and
   white space in examples are provided only to illustrate element
   relationships and are not REQUIRED features of this protocol.  A
   protocol client that is authorized to manage an existing object is
   described as a "sponsoring" client throughout this document.

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2.  Protocol Description

   EPP is a stateful XML protocol that can be layered over multiple
   transport protocols.  Protected using lower-layer security protocols,
   clients exchange identification, authentication, and option
   information, and then engage in a series of client-initiated command-
   response exchanges.  All EPP commands are atomic (there is no partial
   success or partial failure) and designed so that they can be made
   idempotent (executing a command more than once has the same net
   effect on system state as successfully executing the command once).

   EPP provides four basic service elements: service discovery,
   commands, responses, and an extension framework that supports
   definition of managed objects and the relationship of protocol
   requests and responses to those objects.

   An EPP server MUST respond to client-initiated communication (which
   can be either a lower-layer connection request or an EPP service
   discovery message) by returning a greeting to a client.  A server
   MUST promptly respond to each EPP command with a coordinated response
   that describes the results of processing the command.  The following
   server state machine diagram illustrates the message exchange process
   in detail:

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              |
              V
      +-----------------+                  +-----------------+
      |   Waiting for   |     Connected    |     Prepare     |
      |      Client     |----------------->|     Greeting    |
      +-----------------+    or <hello>    +-----------------+
         ^                                           |
         | Close Connection                     Send |
         |     or Idle                      Greeting |
      +-----------------+                            V
      |       End       |     Timeout      +-----------------+
      |     Session     |<-----------------|   Waiting for   |
      +-----------------+                  |      Client     |
         ^    ^    ^        Send +-------->|  Authentication |
         |    |    |    Response |         +-----------------+
         |    |    |     +--------------+            |
         |    |    |     | Prepare Fail |            | <login>
         |    |    +-----|   Response   |            | Received
         |    |    Send  +--------------+            V
         |    |    2501          ^         +-----------------+
         |    |   Response       |         |   Processing    |
         |    |                  +---------|     <login>     |
         |    |                  Auth Fail +-----------------+
         |    |       Timeout                         |
         |    +-------------------------------+       | Auth OK
         |                                    |       V
         |   +-----------------+  <hello>  +-----------------+
         |   |     Prepare     |<----------|   Waiting for   |
         |   |     Greeting    |---------->|   Command or    |
         |   +-----------------+   Send    |     <hello>     |
         | Send x5xx             Greeting  +-----------------+
         | Response  +-----------------+  Send    ^  |
         +-----------|     Prepare     | Response |  | Command
                     |     Response    |----------+  | Received
                     +-----------------+             V
                                ^          +-----------------+
                        Command |          |   Processing    |
                      Processed +----------|     Command     |
                                           +-----------------+

   Figure 1: EPP Server State Machine

   EPP commands fall into three categories: session management commands,
   query commands, and object transform commands.  Session management
   commands are used to establish and end persistent sessions with an
   EPP server.  Query commands are used to perform read-only object
   information retrieval operations.  Transform commands are used to
   perform read-write object management operations.

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   Commands are processed by a server in the order they are received
   from a client.  Though an immediate response confirming receipt and
   processing of the command is produced by the server, the protocol
   includes features that allow for offline review of transform commands
   before the requested action is actually completed.  In such
   situations, the response from the server MUST clearly note that the
   command has been received and processed but that the requested action
   is pending.  The state of the corresponding object MUST clearly
   reflect processing of the pending action.  The server MUST also
   notify the client when offline processing of the action has been
   completed.  Object mappings SHOULD describe standard formats for
   notices that describe completion of offline processing.

   EPP uses XML namespaces to provide an extensible object management
   framework and to identify schemas required for XML instance parsing
   and validation.  These namespaces and schema definitions are used to
   identify both the base protocol schema and the schemas for managed
   objects.  The XML namespace prefixes used in examples (such as the
   string "foo" in "xmlns:foo") are solely for illustrative purposes.  A
   conforming implementation MUST NOT require the use of these or any
   other specific namespace prefixes.

   All XML instances SHOULD begin with an <?xml?> declaration to
   identify the version of XML that is being used, optionally identify
   use of the character encoding used, and optionally provide a hint to
   an XML parser that an external schema file is needed to validate the
   XML instance.  Conformant XML parsers recognize both UTF-8 (defined
   in RFC 3629 [RFC3629]) and UTF-16 (defined in RFC 2781 [RFC2781]);
   per RFC 2277 [RFC2277], UTF-8 is the RECOMMENDED character encoding
   for use with EPP.

   Character encodings other than UTF-8 and UTF-16 are allowed by XML.
   UTF-8 is the default encoding assumed by XML in the absence of an
   "encoding" attribute or a byte order mark (BOM); thus, the "encoding"
   attribute in the XML declaration is OPTIONAL if UTF-8 encoding is
   used.  EPP clients and servers MUST accept a UTF-8 BOM if present,
   though emitting a UTF-8 BOM is NOT RECOMMENDED.

   Example XML declarations:

   <?xml version="1.0" encoding="UTF-8" standalone="no"?>

   <?xml version="1.0" standalone="no"?>

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

   <?xml version="1.0"?>

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2.1.  Transport Mapping Considerations

   As described previously, EPP can be layered over multiple transport
   protocols.  There are, however, a common set of considerations that
   MUST be addressed by any transport mapping defined for EPP.  These
   include:

   -  The transport mapping MUST preserve command order.

   -  The transport mapping MUST address the relationship between
      sessions and the client-server connection concept.

   -  The transport mapping MUST preserve the stateful nature of the
      protocol.

   -  The transport mapping MUST frame data units.

   -  The transport mapping MUST be onto a transport, such as TCP
      [RFC0793] or Stream Control Transmission Protocol (SCTP)
      [RFC4960], that provides congestion avoidance that follows RFC
      2914 [RFC2914]; or, if it maps onto a protocol such as SMTP
      [RFC5321] or Blocks Extensible Exchange Protocol (BEEP) [RFC3080],
      then the performance issues need to take into account issues of
      overload, server availability, and so forth.

   -  The transport mapping MUST ensure reliability.

   -  The transport mapping MUST explicitly allow or prohibit
      pipelining.

   Pipelining, also known as command streaming, is when a client sends
   multiple commands to a server without waiting for each corresponding
   response.  After sending the commands, the client waits for the
   responses to arrive in the order corresponding to the completed
   commands.  Performance gains can sometimes be realized with
   pipelining, especially with high-latency transports, but there are
   additional considerations associated with defining a transport
   mapping that supports pipelining:

   -  Commands MUST be processed independent of each other.

   -  Depending on the transport, pipelining MAY be possible in the form
      of sending a complete session in a well-defined "batch".

   -  The transport mapping MUST describe how an error in processing a
      command affects continued operation of the session.

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   A transport mapping MUST explain how all of these requirements are
   met, given the transport protocol being used to exchange data.

2.2.  Protocol Identification

   All EPP XML instances MUST begin with an <epp> element.  This element
   identifies the start of an EPP protocol element and the namespace
   used within the protocol.  The <epp> start element and the associated
   </epp> ending element MUST be applied to all structures sent by both
   clients and servers.

   Example "start" and "end" EPP elements:

   <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
   </epp>

2.3.  Hello Format

   EPP MAY be carried over both connection-oriented and connection-less
   transport protocols.  An EPP client MAY request a <greeting> from an
   EPP server at any time between a successful <login> command and a
   <logout> command by sending a <hello> to a server.  Use of this
   element is essential in a connection-less environment where a server
   cannot return a <greeting> in response to a client-initiated
   connection.  An EPP <hello> MUST be an empty element with no child
   elements.

   Example <hello>:

   C:<?xml version="1.0" encoding="UTF-8" standalone="no"?>
   C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
   C:  <hello/>
   C:</epp>

2.4.  Greeting Format

   An EPP server responds to a successful connection and <hello> element
   by returning a <greeting> element to the client.  An EPP greeting
   contains the following elements:

   -  An <svID> element that contains the name of the server.

   -  An <svDate> element that contains the server's current date and
      time in Universal Coordinated Time (UTC).

   -  An <svcMenu> element that identifies the services supported by the
      server, including:

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      o  One or more <version> elements that identify the protocol
         versions supported by the server.

      o  One or more <lang> elements that contain the identifiers of the
         text response languages known by the server.  Language
         identifiers MUST be structured as documented in [RFC4646].

      o  One or more <objURI> elements that contain namespace URIs
         representing the objects that the server is capable of
         managing.  A server MAY limit object management privileges on a
         per-client basis.

      o  An OPTIONAL <svcExtension> element that contains one or more
         <extURI> elements that contain namespace URIs representing
         object extensions supported by the server.

      o  A <dcp> (data collection policy) element that contains child
         elements used to describe the server's privacy policy for data
         collection and management.  Policy implications usually extend
         beyond the client-server relationship.  Both clients and
         servers can have relationships with other entities that need to
         know the server operator's data collection policy to make
         informed provisioning decisions.  Policy information MUST be
         disclosed to provisioning entities, though the method of
         disclosing policy data outside of direct protocol interaction
         is beyond the scope of this specification.  Child elements
         include the following:

         *  An <access> element that describes the access provided by
            the server to the client on behalf of the originating data
            source.  The <access> element MUST contain one of the
            following child elements:

            +  <all/>: Access is given to all identified data.

            +  <none/>: No access is provided to identified data.

            +  <null/>: Data is not persistent, so no access is
               possible.

            +  <personal/>: Access is given to identified data relating
               to individuals and organizational entities.

            +  <personalAndOther/>: Access is given to identified data
               relating to individuals, organizational entities, and
               other data of a non-personal nature.

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            +  <other/>: Access is given to other identified data of a
               non-personal nature.

         *  One or more <statement> elements that describe data
            collection purposes, data recipients, and data retention.
            Each <statement> element MUST contain a <purpose> element, a
            <recipient> element, and a <retention> element.  The
            <purpose> element MUST contain one or more of the following
            child elements that describe the purposes for which data is
            collected:

            +  <admin/>: Administrative purposes.  Information can be
               used for administrative and technical support of the
               provisioning system.

            +  <contact/>: Contact for marketing purposes.  Information
               can be used to contact individuals, through a
               communications channel other than the protocol, for the
               promotion of a product or service.

            +  <prov/>: Object-provisioning purposes.  Information can
               be used to identify objects and inter-object
               relationships.

            +  <other/>: Other purposes.  Information may be used in
               other ways not captured by the above definitions.

         *  The <recipient> element MUST contain one or more of the
            following child elements that describes the recipients of
            collected data:

            +  <other/>: Other entities following unknown practices.

            +  <ours>: Server operator and/or entities acting as agents
               or entities for whom the server operator is acting as an
               agent.  An agent in this instance is defined as a third
               party that processes data only on behalf of the service
               provider for the completion of the stated purposes.  The
               <ours> element contains an OPTIONAL <recDesc> element
               that can be used to describe the recipient.

            +  <public/>: Public forums.

            +  <same/>: Other entities following server practices.

            +  <unrelated/>: Unrelated third parties.

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         *  The <retention> element MUST contain one of the following
            child elements that describes data retention practices:

            +  <business/>: Data persists per business practices.

            +  <indefinite/>: Data persists indefinitely.

            +  <legal/>: Data persists per legal requirements.

            +  <none/>: Data is not persistent and is not retained for
               more than a brief period of time necessary to make use of
               it during the course of a single online interaction.

            +  <stated/>: Data persists to meet the stated purpose.

         *  An OPTIONAL <expiry> element that describes the lifetime of
            the policy.  The <expiry> element MUST contain one of the
            following child elements:

            +  <absolute/>: The policy is valid from the current date
               and time until it expires on the specified date and time.

            +  <relative/>: The policy is valid from the current date
               and time until the end of the specified duration.

   Data collection policy elements are based on work described in the
   World Wide Web Consortium's Platform for Privacy Preferences
   [W3C.REC-P3P-20020416] specification.

   Example greeting:

   S:<?xml version="1.0" encoding="UTF-8" standalone="no"?>
   S:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
   S:  <greeting>
   S:    <svID>Example EPP server epp.example.com</svID>
   S:    <svDate>2000-06-08T22:00:00.0Z</svDate>
   S:    <svcMenu>
   S:      <version>1.0</version>
   S:      <lang>en</lang>
   S:      <lang>fr</lang>
   S:      <objURI>urn:ietf:params:xml:ns:obj1</objURI>
   S:      <objURI>urn:ietf:params:xml:ns:obj2</objURI>
   S:      <objURI>urn:ietf:params:xml:ns:obj3</objURI>
   S:      <svcExtension>
   S:        <extURI>http://custom/obj1ext-1.0</extURI>
   S:      </svcExtension>
   S:    </svcMenu>
   S:    <dcp>

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   S:      <access><all/></access>
   S:      <statement>
   S:        <purpose><admin/><prov/></purpose>
   S:        <recipient><ours/><public/></recipient>
   S:        <retention><stated/></retention>
   S:      </statement>
   S:    </dcp>
   S:  </greeting>
   S:</epp>

2.5.  Command Format

   An EPP client interacts with an EPP server by sending a command to
   the server and receiving a response from the server.  In addition to
   the standard EPP elements, an EPP command contains the following
   elements:

   -  A command element whose tag corresponds to one of the valid EPP
      commands described in this document.  The command element MAY
      contain either protocol-specified or object-specified child
      elements.

   -  An OPTIONAL <extension> element that MAY be used for server-
      defined command extensions.

   -  An OPTIONAL <clTRID> (client transaction identifier) element that
      MAY be used to uniquely identify the command to the client.
      Clients are responsible for maintaining their own transaction
      identifier space to ensure uniqueness.

   Example command with object-specified child elements:

   C:<?xml version="1.0" encoding="UTF-8" standalone="no"?>
   C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
   C:  <command>
   C:    <info>
   C:      <obj:info xmlns:obj="urn:ietf:params:xml:ns:obj">
   C:        <obj:name>example</obj:name>
   C:      </obj:info>
   C:    </info>
   C:    <clTRID>ABC-12345</clTRID>
   C:  </command>
   C:</epp>

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2.6.  Response Format

   An EPP server responds to a client command by returning a response to
   the client.  EPP commands are atomic, so a command will either
   succeed completely or fail completely.  Success and failure results
   MUST NOT be mixed.  In addition to the standard EPP elements, an EPP
   response contains the following elements:

   -  One or more <result> elements that document the success or failure
      of command execution.  If the command was processed successfully,
      only one <result> element MUST be returned.  If the command was
      not processed successfully, multiple <result> elements MAY be
      returned to document failure conditions.  Each <result> element
      contains the following attribute and child elements:

      o  A "code" attribute whose value is a four-digit, decimal number
         that describes the success or failure of the command.

      o  A <msg> element containing a human-readable description of the
         response code.  The language of the response is identified via
         an OPTIONAL "lang" attribute.  If not specified, the default
         attribute value MUST be "en" (English).

      o  Zero or more OPTIONAL <value> elements that identify a client-
         provided element (including XML tag and value) or other
         information that caused a server error condition.

      o  Zero or more OPTIONAL <extValue> elements that can be used to
         provide additional error diagnostic information, including:

         *  A <value> element that identifies a client-provided element
            (including XML tag and value) that caused a server error
            condition.

         *  A <reason> element containing a human-readable message that
            describes the reason for the error.  The language of the
            response is identified via an OPTIONAL "lang" attribute.  If
            not specified, the default attribute value MUST be "en"
            (English).

   -  An OPTIONAL <msgQ> element that describes messages queued for
      client retrieval.  A <msgQ> element MUST NOT be present if there
      are no messages queued for client retrieval.  A <msgQ> element MAY
      be present in responses to EPP commands other than the <poll>
      command if messages are queued for retrieval.  A <msgQ> element
      MUST be present in responses to the EPP <poll> command if messages
      are queued for retrieval.  The <msgQ> element contains the
      following attributes:

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      o  A "count" attribute that describes the number of messages that
         exist in the queue.

      o  An "id" attribute used to uniquely identify the message at the
         head of the queue.

      The <msgQ> element contains the following OPTIONAL child elements
      that MUST be returned in response to a <poll> request command and
      MUST NOT be returned in response to any other command, including a
      <poll> acknowledgement:

      o  A <qDate> element that contains the date and time that the
         message was enqueued.

      o  A <msg> element containing a human-readable message.  The
         language of the response is identified via an OPTIONAL "lang"
         attribute.  If not specified, the default attribute value MUST
         be "en" (English).  This element MAY contain XML content for
         formatting purposes, but the XML content is not specified by
         the protocol and will thus not be processed for validity.

   -  An OPTIONAL <resData> (response data) element that contains child
      elements specific to the command and associated object.

   -  An OPTIONAL <extension> element that MAY be used for server-
      defined response extensions.

   -  A <trID> (transaction identifier) element containing the
      transaction identifier assigned by the server to the command for
      which the response is being returned.  The transaction identifier
      is formed using the <clTRID> associated with the command if
      supplied by the client and a <svTRID> (server transaction
      identifier) that is assigned by and unique to the server.

   Transaction identifiers provide command-response synchronization
   integrity.  They SHOULD be logged, retained, and protected to ensure
   that both the client and the server have consistent temporal and
   state-management records.

   Example response without <value> or <resData>:

   S:<?xml version="1.0" encoding="UTF-8" standalone="no"?>
   S:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
   S:  <response>
   S:    <result code="1000">
   S:      <msg lang="en">Command completed successfully</msg>
   S:    </result>
   S:    <trID>

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   S:      <clTRID>ABC-12345</clTRID>
   S:      <svTRID>54321-XYZ</svTRID>
   S:    </trID>
   S:  </response>
   S:</epp>

   Example response with <resData>:

   S:<?xml version="1.0" encoding="UTF-8" standalone="no"?>
   S:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
   S:  <response>
   S:    <result code="1000">
   S:      <msg>Command completed successfully</msg>
   S:    </result>
   S:    <resData>
   S:      <obj:creData xmlns:obj="urn:ietf:params:xml:ns:obj">
   S:        <obj:name>example</obj:name>
   S:      </obj:creData>
   S:    </resData>
   S:    <trID>
   S:      <clTRID>ABC-12345</clTRID>
   S:      <svTRID>54321-XYZ</svTRID>
   S:    </trID>
   S:  </response>
   S:</epp>

   Example response with error value elements:

   S:<?xml version="1.0" encoding="UTF-8" standalone="no"?>
   S:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
   S:  <response>
   S:    <result code="2004">
   S:      <msg>Parameter value range error</msg>
   S:      <value xmlns:obj="urn:ietf:params:xml:ns:obj">
   S:        <obj:elem1>2525</obj:elem1>
   S:      </value>
   S:    </result>
   S:    <result code="2005">
   S:      <msg>Parameter value syntax error</msg>
   S:      <value xmlns:obj="urn:ietf:params:xml:ns:obj">
   S:        <obj:elem2>ex(ample</obj:elem2>
   S:      </value>
   S:      <extValue>
   S:        <value xmlns:obj="urn:ietf:params:xml:ns:obj">
   S:          <obj:elem3>abc.ex(ample</obj:elem3>
   S:        </value>
   S:        <reason>Invalid character found.</reason>
   S:      </extValue>

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   S:    </result>
   S:    <trID>
   S:      <clTRID>ABC-12345</clTRID>
   S:      <svTRID>54321-XYZ</svTRID>
   S:    </trID>
   S:  </response>
   S:</epp>

   Example response with notice of waiting server messages:

   S:<?xml version="1.0" encoding="UTF-8" standalone="no"?>
   S:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
   S:  <response>
   S:    <result code="1000">
   S:      <msg>Command completed successfully</msg>
   S:    </result>
   S:    <msgQ count="5" id="12345"/>
   S:    <trID>
   S:      <clTRID>ABC-12345</clTRID>
   S:      <svTRID>54321-XYZ</svTRID>
   S:    </trID>
   S:  </response>
   S:</epp>

   Command success or failure MUST NOT be assumed if no response is
   returned or if a returned response is malformed.  Protocol
   idempotency ensures the safety of retrying a command in cases of
   response-delivery failure.

2.7.  Protocol Extension Framework

   EPP provides an extension framework that allows features to be added
   at the protocol, object, and command-response levels.

2.7.1.  Protocol Extension

   The EPP extension framework allows for definition of new protocol
   elements identified using XML namespace notation with a reference to
   an XML schema that defines the namespace.  The <epp> element that
   identifies the beginning of a protocol instance includes multiple
   child element choices, one of which is an <extension> element whose
   children define the extension.  For example, a protocol extension
   element would be described in generic terms as follows:

   C:<epp>
   C:  <extension>
   C:    <!-- One or more extension elements. -->
   C:    <ext:foo xmlns:ext="urn:ietf:params:xml:ns:ext">

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   C:      <!-- One or more extension child elements. -->
   C:    </ext:foo>
   C:  </extension>
   C:</epp>

   This document does not define mappings for specific extensions.
   Extension specifications MUST be described in separate documents that
   define the objects and operations subject to the extension.

2.7.2.  Object Extension

   EPP provides an extensible object management framework that defines
   the syntax and semantics of protocol operations applied to a managed
   object.  This framework pushes the definition of each protocol
   operation into the context of a specific object, providing the
   ability to add mappings for new objects without having to modify the
   base protocol.

   Protocol elements that contain data specific to objects are
   identified using XML namespace notation with a reference to an XML
   schema that defines the namespace.  The schema for EPP supports use
   of dynamic object schemas on a per-command and per-response basis.
   For example, the start of an object-specific command element would be
   described in generic terms as follows:

   C:<EPPCommandName>
   C:  <object:command xmlns:object="urn:ietf:params:xml:ns:object">
   C:    <!-- One or more object-specific command elements. -->
   C:  </object:command>
   C:</EPPCommandName>

   An object-specific response element would be described similarly:

   S:<resData>
   S:  <object:resData xmlns:object="urn:ietf:params:xml:ns:object">
   S:    <!-- One or more object-specific response elements. -->
   S:  </object:resData>
   S:</resData>

   This document does not define mappings for specific objects.  The
   mapping of EPP to an object MUST be described in separate documents
   that specifically address each command and response in the context of
   the object.  A suggested object mapping outline is included as an
   appendix to this document.

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2.7.3.  Command-Response Extension

   EPP provides a facility for protocol command and response extensions.
   Protocol commands and responses MAY be extended by an <extension>
   element that contains additional elements whose syntax and semantics
   are not explicitly defined by EPP or an EPP object mapping.  This
   element is OPTIONAL.  Extensions are typically defined by agreement
   between client and server and MAY be used to extend EPP for unique
   operational needs.  A server-extended command element would be
   described in generic terms as follows:

   C:<command>
   C:  <!-- EPPCommandName can be "create", "update", etc. -->
   C:  <EPPCommandName>
   C:    <object:command xmlns:object="urn:ietf:params:xml:ns:object">
   C:      <!-- One or more object-specific command elements. -->
   C:    </object:command>
   C:  </EPPCommandName>
   C:  <extension>
   C:    <!-- One or more server-defined elements. -->
   C:  </extension>
   C:</command>

   A server-extended response element would be described similarly:

   S:<response>
   S:  <result code="1000">
   S:    <msg lang="en">Command completed successfully</msg>
   S:  </result>
   S:  <extension>
   S:    <!-- One or more server-defined elements. -->
   S:  </extension>
   S:  <trID>
   S:    <clTRID>ABC-12345</clTRID>
   S:    <svTRID>54321-XYZ</svTRID>
   S:  </trID>
   S:</response>

   This document does not define any specific server extensions.  The
   mapping of server extensions to EPP MUST be described in separate
   documents that specifically address extended commands and responses
   in the server's operational context.

2.8.  Object Identification

   Some objects, such as name servers and contacts, can have utility in
   multiple repositories.  However, maintaining disjoint copies of
   object information in multiple repositories can lead to

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   inconsistencies that have adverse consequences for the Internet.  For
   example, changing the name of a name server in one repository but not
   in a second repository that refers to the server for domain name
   delegation can produce unexpected DNS query results.

   Globally unique identifiers can help facilitate object-information
   sharing between repositories.  A globally unique identifier MUST be
   assigned to every object when the object is created; the identifier
   MUST be returned to the client as part of any request to retrieve the
   detailed attributes of an object.  Specific identifier values are a
   matter of repository policy, but they SHOULD be constructed according
   to the following algorithm:

   a.  Divide the provisioning repository world into a number of object
       repository classes.

   b.  Each repository within a class is assigned an identifier that is
       maintained by IANA.

   c.  Each repository is responsible for assigning a unique local
       identifier for each object within the repository.

   d.  The globally unique identifier is a concatenation of the local
       identifier, followed by a hyphen ("-", ASCII value 0x002D),
       followed by the repository identifier.



(page 19 continued on part 2)

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