One document matched: draft-ietf-xmpp-6122bis-09.xml

<?xml version="1.0"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
<?rfc compact="yes"?>
<?rfc strict="yes"?>
<?rfc symrefs="yes"?>
<?rfc toc="yes"?>
<?rfc tocdepth="4"?>

<rfc category="std" docName="draft-ietf-xmpp-6122bis-09" ipr="trust200902" obsoletes="6122">

  <front>

    <title abbrev="XMPP Address Format">Extensible Messaging and Presence Protocol (XMPP): Address Format</title>

    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization>Cisco Systems, Inc.</organization>
      <address>
        <postal>
          <street>1899 Wynkoop Street, Suite 600</street>
          <city>Denver</city>
          <region>CO</region>
          <code>80202</code>
          <country>USA</country>
        </postal>
        <phone>+1-303-308-3282</phone>
        <email>psaintan@cisco.com</email>
      </address>
    </author>

    <date/>

    <area>RAI</area>
    <workgroup>XMPP</workgroup>
    <keyword>Extensible Messaging and Presence Protocol</keyword>
    <keyword>XMPP</keyword>
    <keyword>Jabber</keyword>
    <keyword>Messaging</keyword>
    <keyword>Instant Messaging</keyword>
    <keyword>Presence</keyword>
    <keyword>Extensible Markup Language</keyword>
    <keyword>XML</keyword>
    <keyword>Internationalization</keyword>
    <keyword>PRECIS</keyword>

    <abstract>
      <t>This document defines the address format for the Extensible Messaging and Presence Protocol (XMPP), including support for code points outside the ASCII range.  This document obsoletes RFC 6122.</t>
    </abstract>

  </front>

  <middle>

  <section title="Introduction" anchor="intro">
    <t>The Extensible Messaging and Presence Protocol (XMPP) <xref target='RFC6120'/> is an application profile of the Extensible Markup Language <xref target="XML"/> for streaming XML data in close to real time between any two or more network-aware entities.  The address format for XMPP entities was originally developed in the Jabber open-source community in 1999, first described by <xref target='XEP-0029'/> in 2002, and then defined canonically by <xref target='RFC3920'/> in 2004 and <xref target='RFC6122'/> in 2011.</t>
    <t>As specified in RFC 3920 and RFC 6122, the XMPP address format used the "stringprep" technology for preparation of non-ASCII characters <xref target='RFC3454'/>.  Following the migration of internationalized domain names away from stringprep, this document defines the XMPP address format in a way that no longer depends on stringprep (see the PRECIS problem statement <xref target='RFC6885'/>).  Instead, this document builds upon the internationalization framework defined by the IETF's PRECIS Working Group <xref target='I-D.ietf-precis-framework'/>, while attempting to ensure that the characters allowed in Jabber IDs under stringprep are still allowed and handled in the same way under PRECIS.</t>
    <t>This document obsoletes RFC 6122.</t>
  </section>

  <section title="Terminology" anchor="terms">
    <t>Many important terms used in this document are defined in <xref target='I-D.ietf-precis-framework'/>, <xref target='RFC5890'/>, <xref target='RFC6120'/>, <xref target='RFC6365'/>, and <xref target='UNICODE'/>.</t>
    <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in <xref target='RFC2119'/>.</t>
  </section>

  <section title="Addresses" anchor="addressing">

    <section title="Fundamentals" anchor="addressing-fundamentals">
      <t>An XMPP entity is anything that can communicate using XMPP.  For historical reasons, the network address of an XMPP entity is called a Jabber ID ("JID").  A valid JID is a string of Unicode code points <xref target='UNICODE'/>, encoded using UTF-8 <xref target='RFC3629'/>, and structured as an ordered sequence of localpart, domainpart, and resourcepart, where the first two parts are demarcated by the '@' character used as a separator and the last two parts are similarly demarcated by the '/' character (e.g., <juliet@example.com/balcony>).</t>
      <t>The syntax for a JID is defined as follows using the Augmented Backus-Naur Form (ABNF) as specified in <xref target="RFC5234"/>.</t>
      <figure>
        <artwork><![CDATA[
   jid           = [ localpart "@" ] domainpart [ "/" resourcepart ]
   localpart     = 1*1023(localpoint)
                   ;
                   ; a "localpoint" is a UTF-8 encoded 
                   ; Unicode code point that conforms to 
                   ; the "JIDlocalIdentifierClass" profile
                   ; of the PRECIS IdentifierClass
                   ;
   domainpart    = IP-literal / IPv4address / ifqdn
                   ;
                   ; the "IPv4address" and "IP-literal" 
                   ; rules are defined in RFC 3986, and 
                   ; the first-match-wins (a.k.a. "greedy") 
                   ; algorithm described in RFC 3986 
                   ; applies to the matching process
                   ;
                   ; note well that reuse of the IP-literal 
                   ; rule from RFC 3986 implies that IPv6 
                   ; addresses are enclosed in square 
                   ; brackets (i.e., beginning with '['
                   ; and ending with ']')
                   ;
   ifqdn         = 1*1023(domainpoint)
                   ;
                   ; a "domainpoint" is a UTF-8 encoded 
                   ; Unicode code point that conforms to 
                   ; RFC 5890
                   ;
   resourcepart  = 1*1023(resourcepoint)
                   ;
                   ; a "resourcepoint" is a UTF-8 encoded 
                   ; Unicode code point that conforms to 
                   ; the "JIDresourceFreeformClass" profile
                   ; of the PRECIS FreeformClass
                   ;
        ]]></artwork>
      </figure>
      <t>All JIDs are based on the foregoing structure.  However, note that the formal syntax provided above does not capture all of the rules and restrictions that apply to JIDs, which are described below.</t>
      <t>Each allowable portion of a JID (localpart, domainpart, and resourcepart) MUST NOT be zero octets in length and MUST NOT be more than 1023 octets in length, resulting in a maximum total size (including the '@' and '/' separators) of 3071 octets.</t>
      <t><list style='empty'><t>Implementation Note: The length limits on JIDs and parts of JIDs are based on octets (bytes), not characters.  UTF-8 encoding can result in more than one octet per character.</t></list></t> 
      <t><list style='empty'><t>Implementation Note: When dividing a JID into its component parts, an implementation needs to match the separator characters '@' and '/' before applying any transformation algorithms, which might decompose certain Unicode code points to the separator characters (e.g., under Unicode Normalization Form KC U+FE6B SMALL COMMERCIAL AT decomposes to U+0040 COMMERCIAL AT, although note that this decomposition does not occur under Unicode Normalization C, which is used in this specification).</t></list></t> 
      <t>This document defines the native format for JIDs; see <xref target="RFC5122"/> for information about the representation of a JID as a Uniform Resource Identifier (URI) <xref target="RFC3986"/> or Internationalized Resource Identifier (IRI) <xref target="RFC3987"/> and the extraction of a JID from an XMPP URI or IRI.</t>
    </section>

    <section title="Domainpart" anchor="addressing-domainpart">
      <t>The domainpart of a JID is that portion after the '@' character (if any) and before the '/' character (if any); it is the primary identifier and is the only REQUIRED element of a JID (a mere domainpart is a valid JID).  Typically a domainpart identifies the "home" server to which clients connect for XML routing and data management functionality.  However, it is not necessary for an XMPP domainpart to identify an entity that provides core XMPP server functionality (e.g., a domainpart can identify an entity such as a multi-user chat service <xref target='XEP-0045'/>, a publish-subscribe service <xref target='XEP-0060'/>, or a user directory).</t>
      <t>The domainpart for every XMPP service MUST be a fully-qualified domain name (FQDN), an IPv4 address, an IPv6 address, or an unqualified hostname (i.e., a text label that is resolvable on a local network).</t>
      <t><list style='empty'><t>Informational Note: The term "fully-qualified domain name" is not well defined.  In <xref target='RFC1034'/> it is also called an absolute domain name, and the two terms are associated in <xref target='RFC1535'/>.  The earliest use of the term can be found in <xref target='RFC1123'/>.  References to those older specifications ought not to be construed as limiting the characters of a fully-qualified domain name to the ASCII range; for example, <xref target='RFC5890'/> mentions that a fully-qualified domain name can contain one or more U-labels.</t></list></t> 
      <t><list style='empty'><t>Interoperability Note: Domainparts that are IP addresses might not be accepted by other services for the purpose of server-to-server communication, and domainparts that are unqualified hostnames cannot be used on public networks because they are resolvable only on a local network.</t></list></t>
      <t>If the domainpart includes a final character considered to be a label separator (dot) by <xref target='RFC1034'/>, this character MUST be stripped from the domainpart before the JID of which it is a part is used for the purpose of routing an XML stanza, comparing against another JID, or constructing an XMPP URI or IRI <xref target='RFC5122'/>. In particular, such a character MUST be stripped before any other canonicalization steps are taken.</t>
      <t>In general, the content of a domainpart is an Internationalized Domain Name ("IDN") as described in the specifications for Internationalized Domain Names in Applications (commonly called "IDNA2008"), and a domainpart is an "IDNA-aware domain name slot" as defined in <xref target='RFC5890'/>.  The following rules apply to a domainpart that consists of a fully-qualified domain name:</t>
      <t>
        <list style='symbols'>
          <t>The domainpart MUST contain only NR-LDH labels and U-labels as defined in <xref target='RFC5890'/> and MUST consist only of Unicode code points that conform to the rules specified in <xref target='RFC5892'/> (which includes Unicode normalization).<vspace blankLines='1'/></t>
          <t>The domainpart MUST NOT include A-labels as defined in <xref target='RFC5890'/>; each A-label MUST be converted to a U-label during preparation of a domainpart, and comparison MUST be performed using U-labels, not A-labels.<vspace blankLines='1'/></t>
          <t>After conversion of A-labels to U-labels if necessary, all uppercase and titlecase code points within the domainpart MUST be mapped to their lowercase equivalents.<vspace blankLines='1'/></t>
          <t>Fullwidth and halfwidth characters within the domainpart MUST be mapped to their dcomposition equivalents.<vspace blankLines='1'/></t>
          <t>After (and in addition to) case mapping and width mapping, other mappings MAY be applied to the domainpart, such as those defined in <xref target='I-D.ietf-precis-mappings'/> or <xref target='RFC5895'/>.</t>
        </list>
      </t>
      <t>After any and all normalization, conversion, and mapping of code points, a domainpart MUST NOT be zero octets in length and MUST NOT be more than 1023 octets in length.  (Naturally, the length limits of <xref target='RFC1034'/> apply, and nothing in this document is to be interpreted as overriding those more fundamental limits.)</t>
    </section>

    <section title='Localpart' anchor='addressing-localpart'>
      <t>The localpart of a JID is an optional identifier placed before the domainpart and separated from the latter by the '@' character.  Typically a localpart uniquely identifies the entity requesting and using network access provided by a server (i.e., a local account), although it can also represent other kinds of entities (e.g., a chat room associated with a multi-user chat service <xref target='XEP-0045'/>).  The entity represented by an XMPP localpart is addressed within the context of a specific domain (i.e., <localpart@domainpart>).</t>
      <t>A localpart MUST NOT be zero octets in length and MUST NOT be more than 1023 octets in length.  This rule is to be enforced after any normalization and mapping of code points.</t>
      <t>A localpart MUST consist only of Unicode code points that conform to the "JIDlocalIdentifierClass" profile of the "IdentifierClass" base string class defined in <xref target='I-D.ietf-precis-framework'/>.  The JIDlocalIdentifierClass profile includes all code points allowed by the IdentifierClass base class, with the exception of the following characters that are explicitly disallowed in XMPP localparts:</t>
      <t>
        <list style='hanging'>
          <t>U+0022 (QUOTATION MARK), i.e., "</t>
          <t>U+0026 (AMPERSAND), i.e., &</t>
          <t>U+0027 (APOSTROPHE), i.e., '</t>
          <t>U+002F (SOLIDUS), i.e., /</t>
          <t>U+003A (COLON), i.e., :</t>
          <t>U+003C (LESS-THAN SIGN), i.e., <</t>
          <t>U+003E (GREATER-THAN SIGN), i.e., ></t>
          <t>U+0040 (COMMERCIAL AT), i.e., @</t>
        </list>
      </t>
      <t><list style='empty'><t>Implementation Note: An XMPP-specific method for escaping the above-listed characters (along with U+0020, i.e., ASCII SPACE) has been defined in the JID Escaping specification <xref target='XEP-0106'/>.</t></list></t>
      <t>The normalization and mapping rules for the JIDlocalIdentifierClass are as follows, where the operations specified MUST be completed in the order shown:</t>
      <t>
        <list style='numbers'>
          <t>Fullwidth and halfwidth characters MUST be mapped to their decomposition equivalents.<vspace blankLines='1'/></t>
          <t>Additional mappings MAY be applied, such as those defined in <xref target='I-D.ietf-precis-mappings'/>.<vspace blankLines='1'/></t>
          <t>Uppercase and titlecase characters MUST be mapped to their lowercase equivalents.<vspace blankLines='1'/></t>
          <t>All characters MUST be mapped using Unicode Normalization Form C (NFC).</t>
        </list>
      </t>
      <t>With regard to directionality, applications MUST apply the "Bidi Rule" defined in <xref target='RFC5893'/> (i.e., each of the six conditions of the Bidi Rule must be satisfied).</t>
    </section>

    <section title="Resourcepart" anchor="addressing-resourcepart">
      <t>The resourcepart of a JID is an optional identifier placed after the domainpart and separated from the latter by the '/' character.  A resourcepart can modify either a <localpart@domainpart> address or a mere <domainpart> address.  Typically a resourcepart uniquely identifies a specific connection (e.g., a device or location) or object (e.g., an occupant in a multi-user chat room <xref target='XEP-0045'/>) belonging to the entity associated with an XMPP localpart at a domain (i.e., <localpart@domainpart/resourcepart>).</t>
      <t>A resourcepart MUST NOT be zero octets in length and MUST NOT be more than 1023 octets in length.  This rule is to be enforced after any normalization and mapping of code points.</t>
      <t>A resourcepart MUST consist only of Unicode code points that conform to the "JIDresourceFreeformClass" profile of the "FreeformClass" base string class defined in <xref target='I-D.ietf-precis-framework'/>.</t>
      <t>The normalization and mapping rules for the resourcepart of a JID are as follows, where the operations specified MUST be completed in the order shown:</t>
      <t>
        <list style='numbers'>
          <t>Fullwidth and halfwidth characters MAY be mapped to their decomposition equivalents.<vspace blankLines='1'/></t>
          <t>Map any instances of non-ASCII space to ASCII space (U+0020).<vspace blankLines='1'/></t>
          <t>Other additional mappings MAY be applied, such as those defined in <xref target='I-D.ietf-precis-mappings'/>.<vspace blankLines='1'/></t>
          <t>Uppercase and titlecase characters MAY be mapped to their lowercase equivalents.<vspace blankLines='1'/></t>
          <t>All characters MUST be mapped using Unicode Normalization Form C (NFC).<vspace blankLines='1'/></t>
          <t>Leading and trailing whitespace (i.e., one or more instances of the ASCII space character at the beginning or end of a resourcepart) MUST be removed (e.g., "stpeter " is mapped to "stpeter").</t>
        </list>
      </t>
      <t>With regard to directionality, applications MUST apply the "Bidi Rule" defined in <xref target='RFC5893'/> (i.e., each of the six conditions of the Bidi Rule must be satisfied).</t>
      <t>XMPP entities SHOULD consider resourceparts to be opaque strings and SHOULD NOT impute meaning to any given resourcepart.  In particular:</t>
      <t>
        <list style='symbols'>
          <t>Use of the '/' character as a separator between the domainpart and the resourcepart does not imply that XMPP addresses are hierarchical in the way that, say, HTTP URIs are hierarchical (see <xref target='RFC3986'/> for general discussion); thus for example an XMPP address of the form <localpart@domainpart/foo/bar> does not identify a resource "bar" that exists below a resource "foo" in a hierarchy of resources associated with the entity "localpart@domainpart".<vspace blankLines='1'/></t>
          <t>The '@' character is allowed in the resourcepart and is often used in the "handle" shown in XMPP chatrooms <xref target='XEP-0045'/>.  For example, the JID <room@chat.example.com/user@host> describes an entity who is an occupant of the room <room@chat.example.com> with a handle of <user@host>.  However, chatroom services do not necessarily check such an asserted handle against the occupant's real JID.</t>
        </list>
      </t>
      <t>In some contexts, it might be appropriate to apply more restrictive rules to the preparation and comparison of XMPP resourceparts.  For example, in XMPP Multi-User Chat <xref target='XEP-0045'/> it might be appropriate to apply the rules specified in <xref target='I-D.ietf-precis-nickname'/>.  However, the application of more restrictive rules is out of scope for resourceparts in general and is properly defined in specifications for the relevant XMPP extensions.</t>
    </section>

    <section title="Examples" anchor="addressing-examples">
      <t>The following examples illustrate a small number of JIDs that are consistent with the format defined above.</t>
      <figure>
        <preamble>Table 1: A sample of legal JIDs</preamble>
        <artwork><![CDATA[
+---------------------------------+---------------------------------+
| # | JID                         | Notes                           |
+---------------------------------+---------------------------------+
| 1 | juliet@example.com          | A "bare JID"                    |
+---------------------------------+---------------------------------+
| 2 | juliet@example.com/foo      | A "full JID"                    |
+---------------------------------+---------------------------------+
| 3 | juliet@example.com/foo bar  | Single space in resourcepart    |
+---------------------------------+---------------------------------+
| 4 | foo\20bar@example.com       | Single space in localpart, as   |
|   |                             | optionally escaped using the    |
|   |                             | XMPP "JID Escaping" extension   |
+---------------------------------+---------------------------------+
| 5 | fussball@example.com        | Another bare JID                |
+---------------------------------+---------------------------------+
| 6 | fußball@example.com    | The third character is LATIN    |
|   |                             | SMALL LETTER SHARP S (U+00DF)   |
+---------------------------------+---------------------------------+
| 7 | π@example.com         | A localpart of GREEK SMALL      |
|   |                             | LETTER PI (U+03C0)              |
+---------------------------------+---------------------------------+
| 8 | π@example.com/Σ | A resourcepart of GREEK CAPITAL |
|   |                             | LETTER SIGMA (U+03A3)           |
+---------------------------------+---------------------------------+
| 9 | π@example.com/σ | A resourcepart of GREEK SMALL   |
|   |                             | LETTER SIGMA (U+03C3)           |
+---------------------------------+---------------------------------+
| 10| π@example.com/ς | A resourcepart of GREEK SMALL   |
|   |                             | LETTER FINAL SIGMA (U+03C2)     |
+---------------------------------+---------------------------------+
| 11| henryiv@example.com/♚| A resourcepart of the Unicode   |
|   |                             | character BLACK CHESS KING      |
|   |                             | (U+265A)                        |
+---------------------------------+---------------------------------+
        ]]></artwork>
      </figure>
      <t>Several points are worth noting.  Regarding examples 5 and 6: although in German the character esszett (LATIN SMALL LETTER SHARP S, U+00DF) can mostly be used interchangeably with the two characters "ss", the localparts in these examples are different and (if desired) a server would need to enforce a registration policy that disallows one of them if the other is registered.  Regarding examples 8, 9, and 10: case-mapping of GREEK CAPITAL LETTER SIGMA (U+03A3) to lowercase (i.e., to GREEK SMALL LETTER SIGMA, U+03C3) during comparison would result in matching the JIDs in examples 8 and 9; however, because the PRECIS mapping rules do not account for the special status of GREEK SMALL LETTER FINAL SIGMA (U+03C2), the JIDs in examples 8 and 10 or examples 9 and 10 would not be matched.  Regarding example 11: symbol characters such as BLACK CHESS KING (U+265A) are allowed by the PRECIS FreeformClass and thus can be used in resourceparts.</t>
      <t>The following examples illustrate strings that are not JIDs because they violate the format defined above.</t>
      <figure>
        <preamble>Table 2: A sample of strings that violate the JID rules</preamble>
        <artwork><![CDATA[
+---------------------------------+---------------------------------+
| # | Non-JID string              | Notes                           |
+---------------------------------+---------------------------------+
| 12| "juliet"@example.com        | Quotation marks (U+0022) in     | 
|   |                             | localpart                       |
+---------------------------------+---------------------------------+
| 13| foo bar@example.com         | Space (U+0020) in localpart     |
+---------------------------------+---------------------------------+
| 14| juliet@example.com/ foo     | Leading space in resourcepart   |
+---------------------------------+---------------------------------+
| 15| <@example.com/>             | Zero-length localpart and       |
|   |                             | resourcepart ('<' and '>' are   |
|   |                             | used here to show the start and |
|   |                             | end of the JID in question)     |
+---------------------------------+---------------------------------+
| 16| henryⅣ@example.com   | The sixth character is ROMAN    |
|   |                             | NUMERAL FOUR (U+2163)           |
+---------------------------------+---------------------------------+
| 17| ♚@example.com        | A localpart of BLACK CHESS KING | 
|   |                             | (U+265A)                        |
+---------------------------------+---------------------------------+
        ]]></artwork>
      </figure>
      <t>Here again, several points are worth noting.  Regarding example 13, even though ASCII SPACE (U+0020) is disallowed in the PRECIS IdentifierClass, it can be escaped to "\27" in XMPP localparts by using the JID Escaping rules defined in <xref target='XEP-0106'/>, as illustrated by example 4 in Table 1.  Regarding example 16, the Unicode character ROMAN NUMERAL FOUR (U+2163) has a compatibility equivalent of the string formed of LATIN CAPITAL LETTER I (U+0049) and LATIN CAPITAL LETTER V (U+0056), but characters with compatibility equivalents are not allowed in the PRECIS IdentiferClass.  Regarding example 17: symbol characters are not allowed in the PRECIS IdentifierClass; however, both of the non-ASCII characters in examples 16 and 17 are allowed in the PRECIS Freeform class and therefore in the XMPP resourcepart (as illustrated for U+265A by example 11 in Table 1).</t>
    </section>

  </section>

  <section title="Enforcement in JIDs and JID Parts" anchor="enforcement">
    <t>Enforcement of the XMPP address format rules is the responsibility of XMPP servers.  Although XMPP clients SHOULD prepare complete JIDs and parts of JIDs in accordance with this document before including them in protocol slots within XML streams (such that JIDs and parts of JIDs are in conformance), XMPP servers MUST enforce the rules wherever possible and reject stanzas and other XML elements that violate the rules (for stanzas, by returning a <jid-malformed/> error to the sender as described in Section 8.3.3.8 of <xref target='RFC6120'/>).</t>
    <t>Enforcement applies to complete JIDs and to parts of JIDs.  To facilitate implementation, this document defines the concepts of "JID slot", "localpart slot", and "resourcepart slot" (similar to the concept of a "domain name slot" for IDNA2008 defined in Section 2.3.2.6 of <xref target='RFC5890'/>):</t>
    <t>
      <list style='hanging'>
        <t hangText="JID Slot:">An XML element or attribute explicitly designated in XMPP or in XMPP extensions for carrying a complete JID.<vspace blankLines='1'/></t>
        <t hangText="Localpart Slot:">An XML element or attribute explicitly designated in XMPP or in XMPP extensions for carrying the localpart of a JID.<vspace blankLines='1'/></t>
        <t hangText="Resourcepart Slot:">An XML element or attribute explicitly designated in XMPP or in XMPP extensions for carrying the resourcepart of a JID.</t>
      </list>
    </t>
    <t>A server is responsible for enforcing the address format rules when receiving protocol elements from clients where the server is expected to handle such elements directly or to use them for purposes of routing a stanza to another domain or delivering a stanza to a local entity; two examples from <xref target='RFC6120'/> are the 'to' attribute on XML stanzas (which is a JID slot used by XMPP servers for routing of outbound stanzas) and the <resource/> child of the <bind/> element (which is a resourcepart slot used by XMPP servers for binding of a resource to an account for routing of stanzas between the server and a particular client).  An example from <xref target='RFC6121'/> is the 'jid' attribute of the roster <item/> element.</t>
    <t>A server is not responsible for enforcing the rules when the protocol elements are intended for communication among other entities, typically within the payload of a stanza that the server is merely routing to another domain or delivering to a local entity.  Two examples are the 'initiator' attribute in the Jingle extension <xref target='XEP-0166'/> (which is a JID slot used for client-to-client coordination of multimedia sessions) and the 'nick' attribute in the Multi-User Chat extension <xref target='XEP-0045'/> (which is a resourcepart slot used for administrative purposes in the context of XMPP chatrooms).  In such cases, clients SHOULD enforce the rules themselves and not depend on the server to do so, and client implementers need to understand that not enforcing the rules can lead to a degraded user experience or to security vulnerabilities.  However, when an add-on service (e.g., a multi-user chat service) handles a stanza directly, it ought to enforce the rules as well, as defined in the relevant specification for that type of service.</t>
    <t>This document does not provide an exhaustive list of JID slots, localpart slots, or resourcepart slots.  However, implementers of core XMPP servers are advised to consider as JID slots at least the following elements and attributes when they are handled directly or used for purposes of routing to another domain or delivering to a local entity:</t>
    <t>
      <list style='symbols'>
        <t>The 'from' and 'to' stream attributes and the 'from' and 'to' stanza attributes <xref target='RFC6120'/>.</t>
        <t>The 'jid' attribute of the roster <item/> element for contact list management <xref target='RFC6121'/>.</t>
        <t>The 'value' attribute of the <item/> element for Privacy Lists <xref target='RFC3921'/> <xref target='XEP-0016'/> when the value of the 'type' attribute is "jid".</t>
        <t>The 'jid' attribute of the <item/> element for Service Discovery defined in <xref target='XEP-0030'/>.</t>
        <t>The <value/> element for Data Forms <xref target='XEP-0004'/>, when the 'type' attribute is "jid-single" or "jid-multi".</t>
        <t>The 'jid' attribute of the <conference/> element for Bookmark Storage <xref target='XEP-0048'/>.</t>
        <t>The <JABBERID/> of the <vCard/> element for vCard 3.0 <xref target='XEP-0054'/> and the <uri/> child of the <impp/> element for vCard 4.0 <xref target='XEP-0292'/> when the XML character data identifies an XMPP URI <xref target='RFC5122'/>.</t>
        <t>The 'from' attribute of the <delay/> element for Delayed Delivery <xref target='XEP-0203'/>.</t>
        <t>The 'jid' attribute of the <item/> element for the Blocking Command <xref target='XEP-0191'/>.</t>
        <t>The 'from' and 'to' attributes of the <result/> and <verify/> elements for Server Dialback <xref target='RFC3921'/>, <xref target='XEP-0220'/>.</t>
        <t>The 'from' and 'to' attributes of the <iq/>, <message/>, and <presence/> elements for the Jabber Component Protocol <xref target='XEP-0114'/>.</t>
      </list>
    </t>
    <t>Developers of XMPP clients and specialized XMPP add-on services are advised to check the appropriate specifications for JID slots, localpart slots, and resourcepart slots in XMPP protocol extensions such as Service Discovery <xref target='XEP-0030'/>, Multi-User Chat <xref target='XEP-0045'/>, Publish-Subscribe <xref target='XEP-0060'/>, SOCKS5 Bytestreams <xref target='XEP-0065'/>, In-Band Registration <xref target='XEP-0077'/>, Roster Item Exchange <xref target='XEP-0144'/>, and Jingle <xref target='XEP-0166'/>.</t>
  </section>

  <section title="Internationalization Considerations" anchor="i18n">
    <t>XMPP applications MUST support IDNA2008 for domainparts as described under <xref target='addressing-domainpart'/>, the "JIDlocalIdentifierClass" profile for localparts as described under <xref target='addressing-localpart'/>, and the "JIDresourceFreeformClass" profile for resourceparts as described under <xref target='addressing-resourcepart'/>.  This enables XMPP addresses to include a wide variety of characters outside the ASCII range.  Rules for enforcement of the XMPP address format are provided in <xref target='RFC6120'/> and specifications for various XMPP extensions.</t>
    <t><list style='empty'><t>Interoperability Note: For backward compatibility, many existing XMPP implementations and deployments support IDNA2003 <xref target='RFC3490'/> for domainparts, and the stringprep <xref target='RFC3454'/> profiles Nodeprep and Resourceprep <xref target='RFC3920'/> for localparts and resourceparts.</t></list></t>
  </section>

  <section title="IANA Considerations" anchor="iana">
    <t>The following completed templates provide the information necessary for the IANA to add 'JIDlocalIdentifierClass' and 'JIDresourceFreeformClass' to the PRECIS Profiles Registry.</t>
    <section title="JIDlocalIdentifierClass" anchor="iana-jidlocal">
      <t>
        <list style='hanging'>
          <t hangText='Name:'>JIDlocalIdentifierClass.</t>
          <t hangText='Applicability:'>Localparts of XMPP addresses.</t>
          <t hangText='Base Class:'>IdentifierClass.</t>
          <t hangText='Replaces:'>Nodeprep.</t>
          <t hangText='Width Mapping:'>Map fullwidth and halfwidth characters to their decomposition equivalents.</t>
          <t hangText='Additional Mappings:'>None required or recommended.</t>
          <t hangText='Case Mapping:'>Map uppercase and titlecase characters to lowercase.</t>
          <t hangText='Normalization:'>NFC.</t>
          <t hangText='Directionality:'>The "Bidi Rule" defined in RFC 5893 applies.</t>
          <t hangText='Exclusions:'>Eight legacy characters in the ASCII range: U+0022, U+0026, U+0027, U+002F, U+003A, U+003C, U+003E, U+0040.</t>
          <t hangText='Enforcement:'>In general, XMPP servers are responsible for enforcing the rules (although XMPP clients and components can also be responsible for doing so, depending on the JID slots, localpart slots, and resourcepart slots where JIDs or parts of JIDs are used).</t>
          <t hangText='Specification:'>RFC XXXX. [Note to RFC Editor: please change XXXX to the number issued for this specification.]</t>
        </list>
      </t>
    </section>
    <section title="JIDresourceFreeformClass" anchor="iana-jidresource">
      <t>
        <list style='hanging'>
          <t hangText='Profile:'>JIDresourceFreeformClass.</t>
          <t hangText='Applicability:'>Resourceparts of XMPP addresses.</t>
          <t hangText='Base Class:'>FreeformClass</t>
          <t hangText='Replaces:'>The Resourceprep profile of Stringprep.</t>
          <t hangText='Width Mapping:'>Optional.</t>
          <t hangText='Additional Mappings:'>Map non-ASCII space to ASCII space.</t>
          <t hangText='Case Mapping:'>Optional.</t>
          <t hangText='Normalization:'>NFC.</t>
          <t hangText='Directionality:'>The "Bidi Rule" defined in RFC 5893 applies.</t>
          <t hangText='Exclusions:'>None.</t>
          <t hangText='Enforcement:'>In general, XMPP servers are responsible for enforcing the rules (although XMPP clients and components can also be resonsible for doing so, depending on the JID slots, localpart slots, and resourcepart slots where JIDs or parts of JIDs are used).</t>
          <t hangText='Specification:'>RFC XXXX. [Note to RFC Editor: please change XXXX to the number issued for this specification.]</t>
        </list>
      </t>
    </section>
  </section>

  <section title="Security Considerations" anchor="security">
    <section title="Reuse of PRECIS" anchor="security-PRECIS">
      <t>The security considerations described in <xref target="I-D.ietf-precis-framework"/> apply to the "IdentifierClass" and "FreeformClass" base string classes used in this document for XMPP localparts and resourceparts, respectively.  The security considerations described in <xref target="RFC5890"/> apply to internationalized domain names, which are used here for XMPP domainparts.</t>
    </section>
    <section title="Reuse of Unicode" anchor="security-unicode">
      <t>The security considerations described in <xref target='UTS39'/> apply to the use of Unicode characters in XMPP addresses.</t>
    </section>
    <section title="Address Spoofing" anchor="security-spoofing">
      <t>There are two forms of address spoofing: forging and mimicking.</t>
      <section title="Address Forging" anchor="security-forging">
        <t>In the context of XMPP technologies, address forging occurs when an entity is able to generate an XML stanza whose 'from' address does not correspond to the account credentials with which the entity authenticated onto the network (or an authorization identity provided during negotiation of SASL authentication <xref target='RFC4422'/> as described in <xref target='RFC6120'/>).  For example, address forging occurs if an entity that authenticated as "juliet@im.example.com" is able to send XML stanzas from "nurse@im.example.com" or "romeo@example.net".</t> 
        <t>Address forging is difficult in XMPP systems, given the requirement for sending servers to stamp 'from' addresses and for receiving servers to verify sending domains via server-to-server authentication (see <xref target='RFC6120'/>).  However, address forging is possible if:</t>
        <t>
          <list style='symbols'>
            <t>A poorly implemented server ignores the requirement for stamping the 'from' address.  This would enable any entity that authenticated with the server to send stanzas from any localpart@domainpart as long as the domainpart matches the sending domain of the server.</t>
            <t>An actively malicious server generates stanzas on behalf of any registered account at the domain or domains hosted at that server.</t>
          </list>
        </t>
        <t>Therefore, an entity outside the security perimeter of a particular server cannot reliably distinguish between JIDs of the form <localpart@domainpart> at that server and thus can authenticate only the domainpart of such JIDs with any level of assurance.  This specification does not define methods for discovering or counteracting the kind of poorly implemented or rogue servers just described.  However, the end-to-end authentication or signing of XMPP stanzas could help to mitigate this risk, since it would require the rogue server to generate false credentials for signing or encryption of each stanza, in addition to modifying 'from' addresses.</t>
      </section>
      <section title="Address Mimicking" anchor="security-mimicking">
        <t>Address mimicking occurs when an entity provides legitimate authentication credentials for and sends XML stanzas from an account whose JID appears to a human user to be the same as another JID.  Because many characters are visually similar, it is relatively easy to mimic JIDs in XMPP systems.  As one simple example, the localpart "ju1iet" (using the Arabic numeral one as the third character) might appear the same as the localpart "juliet" (using lowercase "L" as the third character).</t>
        <t>As explained in <xref target='RFC5890'/>, <xref target='I-D.ietf-precis-framework'/>, <xref target='UTR36'/>, and <xref target='UTS39'/>, there is no straightforward solution to the problem of visually similar characters.  Furthermore, IDNA and PRECIS technologies do not attempt to define such a solution.  As a result, XMPP domainparts, localparts, and resourceparts could contain such characters, leading to security vulnerabilities such as the following:</t>
        <t>
          <list style='symbols'>
            <t>A domainpart is always employed as one part of an entity's address in XMPP.  One common usage is as the address of a server or server-side service, such as a multi-user chat service <xref target='XEP-0045'/>.  The security of such services could be compromised based on different interpretations of the internationalized domainpart; for example, a user might authorize a malicious entity at a fake server to view the user's presence information, or a user could join chatrooms at a fake multi-user chat service.<vspace blankLines='1'/></t>
            <t>A localpart can be employed as one part of an entity's address in XMPP.  One common usage is as the username of an instant messaging user; another is as the name of a multi-user chat room; and many other kinds of entities could use localparts as part of their addresses.  The security of such services could be compromised based on different interpretations of the internationalized localpart; for example, a user entering a single internationalized localpart could access another user's account information, or a user could gain access to a hidden or otherwise restricted chat room or service.<vspace blankLines='1'/></t>
            <t>A resourcepart can be employed as one part of an entity's address in XMPP.  One common usage is as the name for an instant messaging user's connected resource; another is as the nickname of a user in a multi-user chat room; and many other kinds of entities could use resourceparts as part of their addresses.  The security of such services could be compromised based on different interpretations of the internationalized resourcepart; for example, two or more confusable resources could be bound at the same time to the same account (resulting in inconsistent authorization decisions in an XMPP application that uses full JIDs), or a user could send a private message to someone other than the intended recipient in a multi-user chat room.</t>
          </list>
        </t>
        <t>XMPP services and clients are strongly encouraged to define and implement consistent policies regarding the registration, storage, and presentation of visually similar characters in XMPP systems.  In particular, service providers and software implementers are strongly encouraged to apply the policies recommended in <xref target='I-D.ietf-precis-framework'/>.</t>
      </section>
    </section>
  </section>

  <section title="Conformance Requirements" anchor="conformance">
    <t>This section describes a protocol feature set that summarizes the conformance requirements of this specification (similar feature sets are provided for XMPP in <xref target='RFC6120'/> and <xref target='RFC6121'/>).  This feature set is appropriate for use in software certification, interoperability testing, and implementation reports.  For each feature, this section provides the following information:</t>
    <t>
      <list style='symbols'>
        <t>A human-readable name</t>
        <t>An informational description</t>
        <t>A reference to the particular section of this document that normatively defines the feature</t>
        <t>Whether the feature applies to the Client role, the Server role, or both (where "N/A" signifies that the feature is not applicable to the specified role)</t>
        <t>Whether the feature MUST or SHOULD be implemented, where the capitalized terms are to be understood as described in <xref target='RFC2119'/></t>
      </list>
    </t>
    <t>The feature set specified here provides a basis for interoperability testing and follows the spirit of a proposal made by Larry Masinter within the IETF's NEWTRK Working Group in 2005 <xref target='INTEROP'/>.</t>
    <t>
      <list style='hanging'>
        <t hangText="Feature:">address-domain-length</t>
        <t hangText="Description:">Ensure that the domainpart of an XMPP address is at least one octet in length and at most 1023 octets in length, and that it conforms to the underlying length limits of the DNS.</t>
        <t hangText="Section:"><xref target='addressing-domainpart'/></t>
        <t hangText="Roles:">Server MUST, client SHOULD.</t>
      </list>
    </t>
    <t>
      <list style='hanging'>
        <t hangText="Feature:">address-domain-prep</t>
        <t hangText="Description:">Ensure that the domainpart of an XMPP address conforms to IDNA2008, that it contains only NR-LDH labels and U-labels (not A-labels), and that all uppercase and titlecase code points are mapped to their lowercase equivalents.</t>
        <t hangText="Section:"><xref target='addressing-domainpart'/></t>
        <t hangText="Roles:">Server MUST, client SHOULD.</t>
      </list>
    </t>
    <t>
      <list style='hanging'>
        <t hangText="Feature:">address-localpart-length</t>
        <t hangText="Description:">Ensure that the localpart of an XMPP address is at least one octet in length and at most 1023 octets in length.</t>
        <t hangText="Section:"><xref target='addressing-localpart'/></t>
        <t hangText="Roles:">Server MUST, client SHOULD.</t>
      </list>
    </t>
    <t>
      <list style='hanging'>
        <t hangText="Feature:">address-localpart-prep</t>
        <t hangText="Description:">Ensure that the localpart of an XMPP address conforms to the "JIDlocalIdentifierClass" profile.</t>
        <t hangText="Section:"><xref target='addressing-localpart'/></t>
        <t hangText="Roles:">Server MUST, client SHOULD.</t>
      </list>
    </t>
    <t>
      <list style='hanging'>
        <t hangText="Feature:">address-resource-length</t>
        <t hangText="Description:">Ensure that the resourcepart of an XMPP address is at least one octet in length and at most 1023 octets in length.</t>
        <t hangText="Section:"><xref target='addressing-resourcepart'/></t>
        <t hangText="Roles:">Server MUST, client SHOULD.</t>
      </list>
    </t>
    <t>
      <list style='hanging'>
        <t hangText="Feature:">address-resource-prep</t>
        <t hangText="Description:">Ensure that the resourcepart of an XMPP address conforms to the "JIDresourceFreeformClass" profile.</t>
        <t hangText="Section:"><xref target='addressing-resourcepart'/>
</t>
        <t hangText="Roles:">Server MUST, client SHOULD.</t>
      </list>
    </t>
  </section>

  </middle>

  <back>

    <references title="Normative References">

<reference anchor='I-D.ietf-precis-framework'>
<front>
<title>Precis Framework: Handling Internationalized Strings in Protocols</title>
<author initials='P' surname='Saint-Andre' fullname='Peter Saint-Andre'>
    <organization>Cisco</organization>
</author>
<author initials='M' surname='Blanchet' fullname='Marc Blanchet'>
    <organization>Viagenie</organization>
</author>
<date month='October' day='18' year='2013' />
<abstract><t>Application protocols using Unicode code points in protocol strings need to prepare such strings in order to perform comparison operations (e.g., for purposes of authentication or authorization).  This document defines a framework enabling application protocols to handle various classes of strings in a way that depends on the properties of Unicode code points and that is agile with respect to versions of Unicode; as a result, this framework provides a more sustainable approach to the handling of internationalized strings than the previous framework, known as Stringprep (RFC 3454).  A specification that reuses this framework can either directly use the base string classes or subclass the base string classes as needed.  This framework takes an approach similar to the revised internationalized domain names in applications (IDNA) technology (RFC 5890, RFC 5891, RFC 5892, RFC 5893, RFC 5894) and thus adheres to the high-level design goals described in RFC 4690, albeit for application technologies other than the Domain Name System (DNS).  This document obsoletes RFC 3454.</t></abstract>
</front>
<seriesInfo name='Internet-Draft' value='draft-ietf-precis-framework-11' />
<format type='TXT'
        target='http://www.ietf.org/internet-drafts/draft-ietf-precis-framework-11.txt' />
</reference>

<reference anchor='RFC1034'>
<front>
<title abbrev='Domain Concepts and Facilities'>Domain names - concepts and facilities</title>
<author initials='P.' surname='Mockapetris' fullname='P. Mockapetris'>
<organization>Information Sciences Institute (ISI)</organization></author>
<date year='1987' day='1' month='November' /></front>
<seriesInfo name='STD' value='13' />
<seriesInfo name='RFC' value='1034' />
<format type='TXT' octets='129180' target='http://www.rfc-editor.org/rfc/rfc1034.txt' />
</reference>

<reference anchor="RFC2119">
<front>
<title abbrev='RFC Key Words'>Key words for use in RFCs to Indicate Requirement Levels</title>
<author initials='S.' surname='Bradner' fullname='Scott Bradner'>
<organization>Harvard University</organization>
<address>
<postal>
<street>1350 Mass.  Ave.</street>
<street>Cambridge</street>
<street>MA 02138</street></postal>
<phone>- +1 617 495 3864</phone>
<email>sob@harvard.edu</email></address></author>
<date month='March' year='1997' />
<area>General</area>
<keyword>keyword</keyword>
<abstract>
<t>
   In many standards track documents several words are used to signify
   the requirements in the specification.  These words are often
   capitalized.  This document defines these words as they should be
   interpreted in IETF documents.  Authors who follow these guidelines
   should incorporate this phrase near the beginning of their document:

<list>
<t>
      The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
      NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and
      "OPTIONAL" in this document are to be interpreted as described in
      RFC 2119.
</t></list></t>
<t>
   Note that the force of these words is modified by the requirement
   level of the document in which they are used.
</t></abstract></front>
<seriesInfo name='BCP' value='14' />
<seriesInfo name='RFC' value='2119' />
<format type='TXT' octets='4723' target='ftp://ftp.isi.edu/in-notes/rfc2119.txt' />
<format type='HTML' octets='14486' target='http://xml.resource.org/public/rfc/html/rfc2119.html' />
<format type='XML' octets='5661' target='http://xml.resource.org/public/rfc/xml/rfc2119.xml' />
</reference>

<reference anchor='RFC3629'>
<front>
<title>UTF-8, a transformation format of ISO 10646</title>
<author initials='F.' surname='Yergeau' fullname='F. Yergeau'>
<organization /></author>
<date month='November' year='2003' /></front>
<seriesInfo name='STD' value='63' />
<seriesInfo name='RFC' value='3629' />
<format type='TXT' octets='33856' target='ftp://ftp.isi.edu/in-notes/rfc3629.txt' />
</reference>

<reference anchor='RFC5234'>
<front>
<title>Augmented BNF for Syntax Specifications: ABNF</title>
<author initials='D.' surname='Crocker' fullname='D. Crocker' role="editor">
<organization /></author>
<author initials='P.' surname='Overell' fullname='P. Overell'>
<organization /></author>
<date year='2008' month='January' />
<abstract>
<t>Internet technical specifications often need to define a formal syntax.  Over the years, a modified version of Backus-Naur Form (BNF), called Augmented BNF (ABNF), has been popular among many Internet specifications.  The current specification documents ABNF.  It balances compactness and simplicity with reasonable representational power.  The differences between standard BNF and ABNF involve naming rules, repetition, alternatives, order-independence, and value ranges.  This specification also supplies additional rule definitions and encoding for a core lexical analyzer of the type common to several Internet specifications. [STANDARDS TRACK]</t></abstract></front>
<seriesInfo name='STD' value='68' />
<seriesInfo name='RFC' value='5234' />
<format type='TXT' octets='26359' target='ftp://ftp.isi.edu/in-notes/rfc5234.txt' />
</reference>

<reference anchor='RFC5890'>
<front>
<title>Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework</title>
<author initials='J.' surname='Klensin' fullname='J. Klensin'>
<organization /></author>
<date year='2010' month='August' />
<abstract>
<t>This document is one of a collection that, together, describe the protocol and usage context for a revision of Internationalized Domain Names for Applications (IDNA), superseding the earlier version.  It describes the document collection and provides definitions and other material that are common to the set. [STANDARDS TRACK]</t></abstract></front>
<seriesInfo name='RFC' value='5890' />
<format type='TXT' octets='54245' target='http://www.rfc-editor.org/rfc/rfc5890.txt' />
</reference>

<reference anchor='RFC5891'>
<front>
<title>Internationalized Domain Names in Applications (IDNA): Protocol</title>
<author initials='J.' surname='Klensin' fullname='J. Klensin'>
<organization /></author>
<date year='2010' month='August' />
<abstract>
<t>This document is the revised protocol definition for Internationalized Domain Names (IDNs).  The rationale for changes, the relationship to the older specification, and important terminology are provided in other documents.  This document specifies the protocol mechanism, called Internationalized Domain Names in Applications (IDNA), for registering and looking up IDNs in a way that does not require changes to the DNS itself.  IDNA is only meant for processing domain names, not free text. [STANDARDS TRACK]</t></abstract></front>
<seriesInfo name='RFC' value='5891' />
<format type='TXT' octets='38105' target='http://www.rfc-editor.org/rfc/rfc5891.txt' />
</reference>

<reference anchor='RFC5892'>
<front>
<title>The Unicode Code Points and Internationalized Domain Names for Applications (IDNA)</title>
<author initials='P.' surname='Faltstrom' fullname='P. Faltstrom'>
<organization /></author>
<date year='2010' month='August' />
<abstract>
<t>This document specifies rules for deciding whether a code point, considered in isolation or in context, is a candidate for inclusion in an Internationalized Domain Name (IDN).</t><t> It is part of the specification of Internationalizing Domain Names in Applications 2008 (IDNA2008). [STANDARDS-TRACK]</t></abstract></front>
<seriesInfo name='RFC' value='5892' />
<format type='TXT' octets='187370' target='http://www.rfc-editor.org/rfc/rfc5892.txt' />
</reference>

<reference anchor='RFC5893'>
<front>
<title>Right-to-Left Scripts for Internationalized Domain Names for Applications (IDNA)</title>
<author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
<organization /></author>
<author initials='C.' surname='Karp' fullname='C. Karp'>
<organization /></author>
<date year='2010' month='August' />
<abstract>
<t>The use of right-to-left scripts in Internationalized Domain Names (IDNs) has presented several challenges.  This memo provides a new Bidi rule for Internationalized Domain Names for Applications (IDNA) labels, based on the encountered problems with some scripts and some shortcomings in the 2003 IDNA Bidi criterion. [STANDARDS-TRACK]</t></abstract></front>
<seriesInfo name='RFC' value='5893' />
<format type='TXT' octets='38870' target='http://www.rfc-editor.org/rfc/rfc5893.txt' />
</reference>

<reference anchor="RFC6120">
<front>
<title>Extensible Messaging and Presence Protocol (XMPP): Core</title>
<author initials='P.' surname='Saint-Andre' fullname='P. Saint-Andre'>
<organization /></author>
<date year='2011' month='March' />
<abstract>
<t>The Extensible Messaging and Presence Protocol (XMPP) is an application profile of the Extensible Markup Language (XML) that enables the near-real-time exchange of structured yet extensible data between any two or more network entities.  This document defines XMPP's core protocol methods: setup and teardown of XML streams, channel encryption, authentication, error handling, and communication primitives for messaging, network availability ("presence"), and request-response interactions.  This document obsoletes RFC 3920. [STANDARDS-TRACK]</t></abstract></front>
<seriesInfo name='RFC' value='6120' />
<format type='TXT' octets='451942' target='http://www.rfc-editor.org/rfc/rfc6120.txt' />
</reference>

<reference anchor="UNICODE" target="http://www.unicode.org/versions/Unicode6.2.0/">
  <front>
    <title>The Unicode Standard, Version 6.2</title>
    <author>
      <organization>The Unicode Consortium</organization>
    </author>
    <date year="2012" />
  </front>
</reference>

<reference anchor="UTR36" target='http://www.unicode.org/reports/tr36/'>
  <front>
    <title>Unicode Technical Report #36: Unicode Security Considerations</title>
    <author>
      <organization>The Unicode Consortium</organization>
    </author>
    <date month="July" year="2012" />
  </front>
  <format type='HTML' target='http://www.unicode.org/reports/tr36/'/>
</reference>

    </references>

    <references title="Informative References">

<reference anchor='I-D.ietf-precis-mappings'>
<front>
<title>Mapping characters for PRECIS classes</title>
<author initials='Y' surname='Yoneya' fullname='Yoshiro Yoneya'>
    <organization />
</author>
<author initials='T' surname='NEMOTO' fullname='Takahiro NEMOTO'>
    <organization />
</author>
<date month='October' day='20' year='2013' />
<abstract><t>The framework for preparation and comparison of internationalized strings ("PRECIS") defines several classes of strings for preparation and comparison.  In the framework, case mapping is defined because many protocols handle case-sensitive or case-insensitive string comparison and therefore preparation of the string is mandatory.  As described in the mapping for Internationalized Domain Names in Applications (IDNA) and the PRECIS problem statement, mappings for internationalized strings are not limited to case, but also width mapping and mapping of delimiters and other specials can be taken into consideration.  This document provides guidelines for authors of protocol profiles of the PRECIS framework and describes several mappings that can be applied between receiving user input and passing permitted code points to internationalized protocols.  The mappings described here are expected to be applied as Additional mapping in the PRECIS framework.</t></abstract>
</front>
<seriesInfo name='Internet-Draft' value='draft-ietf-precis-mappings-05' />
<format type='TXT'
        target='http://www.ietf.org/internet-drafts/draft-ietf-precis-mappings-05.txt' />
</reference>

<reference anchor='I-D.ietf-precis-nickname'>
<front>
<title>Preparation and Comparison of Nicknames</title>
<author initials='P' surname='Saint-Andre' fullname='Peter Saint-Andre'>
    <organization />
</author>
<date month='October' day='18' year='2013' />
<abstract><t>This document describes how to prepare and compare Unicode strings representing nicknames, primarily as used within textual chatrooms.  This profile is intended to be used by chatroom technologies based on both the Message Session Relay Protocol (MSRP) and the Extensible Messaging and Presence Protocol (XMPP).</t></abstract>
</front>
<seriesInfo name='Internet-Draft' value='draft-ietf-precis-nickname-07' />
<format type='TXT'
        target='http://www.ietf.org/internet-drafts/draft-ietf-precis-nickname-07.txt' />
</reference>

<reference anchor='INTEROP'>
<front>
<title>Formalizing IETF Interoperability Reporting</title>
<author initials='L' surname='Masinter' fullname='Larry Masinter'>
    <organization />
</author>
<date month='October' day='11' year='2005' />
<abstract><t>This document suggests another way of reforming IETF standards process by formalizing the mechanism for interoperability reporting, as a way of facilitating standards development. It establishes two kinds of reports: a 'Protocol Feature Set', which lays out the set of features from IETF specifications that constitute a protocol, and a 'Protocol Implementation Report', which is submitted by an individual or group to report on implementation and interoperability testing.</t></abstract>
</front>
<seriesInfo name='Work in' value='Progress' />
<format type='TXT'
        target='http://www.ietf.org/internet-drafts/draft-ietf-newtrk-interop-reports-00.txt' />
</reference>

<reference anchor='RFC1123'>
<front>
<title>Requirements for Internet Hosts - Application and Support</title>
<author initials='R.' surname='Braden' fullname='Robert Braden'>
<organization>University of Southern California (USC), Information Sciences Institute</organization>
<address>
<postal>
<street>4676 Admiralty Way</street>
<city>Marina del Rey</city>
<region>CA</region>
<code>90292-6695</code>
<country>US</country></postal>
<phone>+1 213 822 1511</phone>
<email>Braden@ISI.EDU</email></address></author>
<date year='1989' month='October' /></front>
<seriesInfo name='STD' value='3' />
<seriesInfo name='RFC' value='1123' />
<format type='TXT' octets='245503' target='http://www.rfc-editor.org/rfc/rfc1123.txt' />
</reference>

<reference anchor='RFC1535'>
<front>
<title abbrev='DNS Software Enhancements'>A Security Problem and Proposed Correction With Widely Deployed DNS Software</title>
<author initials='E.' surname='Gavron' fullname='Ehud Gavron'>
<organization>ACES Research Inc.</organization>
<address>
<postal>
<street>PO Box 14546</street>
<city>Tucson</city>
<region>AZ</region>
<code>85711</code>
<country>US</country></postal>
<phone>+1 602 743 9841</phone>
<email>gavron@aces.com</email></address></author>
<date year='1993' month='October' />
<abstract>
<t>This document discusses a flaw in some of the currently distributed name resolver clients.  The flaw exposes a security weakness related to the search heuristic invoked by these same resolvers when users provide a partial domain name, and which is easy to exploit (although not by the masses).  This document points out the flaw, a case in point, and a solution.</t></abstract></front>
<seriesInfo name='RFC' value='1535' />
<format type='TXT' octets='9722' target='http://www.rfc-editor.org/rfc/rfc1535.txt' />
</reference>

<reference anchor="RFC3454">
<front>
<title>Preparation of Internationalized Strings ("stringprep")</title>
<author initials='P.' surname='Hoffman' fullname='P.  Hoffman'>
<organization /></author>
<author initials='M.' surname='Blanchet' fullname='M.  Blanchet'>
<organization /></author>
<date month='December' year='2002' /></front>
<seriesInfo name='RFC' value='3454' />
<format type='TXT' octets='138684' target='ftp://ftp.isi.edu/in-notes/rfc3454.txt' />
</reference>

<reference anchor='RFC3490'>
<front>
<title>Internationalizing Domain Names in Applications (IDNA)</title>
<author initials='P.' surname='Faltstrom' fullname='P. Faltstrom'>
<organization /></author>
<author initials='P.' surname='Hoffman' fullname='P. Hoffman'>
<organization /></author>
<author initials='A.' surname='Costello' fullname='A. Costello'>
<organization /></author>
<date month='March' year='2003' /></front>
<seriesInfo name='RFC' value='3490' />
<format type='TXT' octets='51943' target='ftp://ftp.isi.edu/in-notes/rfc3490.txt' />
<annotation>See Section 1 for an explanation of why the normative reference to an obsoleted specification is needed.</annotation>
</reference>

<reference anchor='RFC3920'>
<front>
<title abbrev='XMPP Core'>Extensible Messaging and Presence Protocol (XMPP): Core</title>
<author initials='P.' surname='Saint-Andre' fullname='Peter Saint-Andre' role='editor'>
<organization>Jabber Software Foundation</organization>
<address>
<email>stpeter@jabber.org</email></address></author>
<date year='2004' month='October' />
<area>Applications</area>
<workgroup>XMPP Working Group</workgroup>
<keyword>RFC</keyword>
<keyword>Request for Comments</keyword>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<keyword>XMPP</keyword>
<keyword>Extensible Messaging and Presence Protocol</keyword>
<keyword>Jabber</keyword>
<keyword>IM</keyword>
<keyword>Instant Messaging</keyword>
<keyword>Presence</keyword>
<keyword>XML</keyword>
<keyword>Extensible Markup Language</keyword>
<abstract>
<t>This memo defines the core features of the Extensible Messaging and Presence Protocol (XMPP), a protocol for streaming Extensible Markup Language (XML) elements in order to exchange structured information in close to real time between any two network endpoints.  While XMPP provides a generalized, extensible framework for exchanging XML data, it is used mainly for the purpose of building instant messaging and presence applications that meet the requirements of RFC 2779.</t></abstract></front>
<seriesInfo name='RFC' value='3920' />
<format type='TXT' octets='194313' target='ftp://ftp.isi.edu/in-notes/rfc3920.txt' />
<format type='HTML' octets='279912' target='http://xml.resource.org/public/rfc/html/rfc3920.html' />
<format type='XML' octets='234610' target='http://xml.resource.org/public/rfc/xml/rfc3920.xml' />
</reference>

<reference anchor='RFC3921'>
<front>
<title abbrev='XMPP IM'>Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence</title>
<author initials='P.' surname='Saint-Andre' fullname='Peter Saint-Andre' role='editor'>
<organization>Jabber Software Foundation</organization>
<address>
<email>stpeter@jabber.org</email></address></author>
<date year='2004' month='October' />
<area>Applications</area>
<workgroup>XMPP Working Group</workgroup>
<keyword>RFC</keyword>
<keyword>Request for Comments</keyword>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<keyword>XMPP</keyword>
<keyword>Extensible Messaging and Presence Protocol</keyword>
<keyword>Jabber</keyword>
<keyword>IM</keyword>
<keyword>Instant Messaging</keyword>
<keyword>Presence</keyword>
<keyword>XML</keyword>
<keyword>Extensible Markup Language</keyword>
<abstract>
<t>This memo describes extensions to and applications of the core features of the Extensible Messaging and Presence Protocol (XMPP) that provide the basic instant messaging (IM) and presence functionality defined in RFC 2779.</t></abstract></front>
<seriesInfo name='RFC' value='3921' />
<format type='TXT' octets='217527' target='http://www.rfc-editor.org/rfc/rfc3921.txt' />
<format type='HTML' octets='274538' target='http://xml.resource.org/public/rfc/html/rfc3921.html' />
<format type='XML' octets='234468' target='http://xml.resource.org/public/rfc/xml/rfc3921.xml' />
</reference>

<reference anchor='RFC3986'>
<front>
<title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
<author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
<organization abbrev='W3C/MIT'>World Wide Web Consortium</organization>
<address>
<postal>
<street>Massachusetts Institute of Technology</street>
<street>77 Massachusetts Avenue</street>
<city>Cambridge</city>
<region>MA</region>
<code>02139</code>
<country>USA</country></postal>
<phone>+1-617-253-5702</phone>
<facsimile>+1-617-258-5999</facsimile>
<email>timbl@w3.org</email>
<uri>http://www.w3.org/People/Berners-Lee/</uri></address></author>
<author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
<organization abbrev='Day Software'>Day Software</organization>
<address>
<postal>
<street>5251 California Ave., Suite 110</street>
<city>Irvine</city>
<region>CA</region>
<code>92617</code>
<country>USA</country></postal>
<phone>+1-949-679-2960</phone>
<facsimile>+1-949-679-2972</facsimile>
<email>fielding@gbiv.com</email>
<uri>http://roy.gbiv.com/</uri></address></author>
<author initials='L.' surname='Masinter' fullname='Larry Masinter'>
<organization abbrev='Adobe Systems'>Adobe Systems Incorporated</organization>
<address>
<postal>
<street>345 Park Ave</street>
<city>San Jose</city>
<region>CA</region>
<code>95110</code>
<country>USA</country></postal>
<phone>+1-408-536-3024</phone>
<email>LMM@acm.org</email>
<uri>http://larry.masinter.net/</uri></address></author>
<date year='2005' month='January' />
<area>Applications</area>
<keyword>uniform resource identifier</keyword>
<keyword>URI</keyword>
<keyword>URL</keyword>
<keyword>URN</keyword>
<keyword>WWW</keyword>
<keyword>resource</keyword>
<abstract>
<t>
A Uniform Resource Identifier (URI) is a compact sequence of characters
that identifies an abstract or physical resource.  This specification
defines the generic URI syntax and a process for resolving URI references
that might be in relative form, along with guidelines and security
considerations for the use of URIs on the Internet.
The URI syntax defines a grammar that is a superset of all valid URIs,
allowing an implementation to parse the common components of a URI
reference without knowing the scheme-specific requirements of every
possible identifier.  This specification does not define a generative
grammar for URIs; that task is performed by the individual
specifications of each URI scheme.
</t></abstract></front>
<seriesInfo name='STD' value='66' />
<seriesInfo name='RFC' value='3986' />
<format type='TXT' octets='141811' target='ftp://ftp.isi.edu/in-notes/rfc3986.txt' />
<format type='HTML' octets='200858' target='http://xml.resource.org/public/rfc/html/rfc3986.html' />
<format type='XML' octets='165759' target='http://xml.resource.org/public/rfc/xml/rfc3986.xml' />
</reference>

<reference anchor='RFC3987'>
<front>
<title>Internationalized Resource Identifiers (IRIs)</title>
<author initials='M.' surname='Duerst' fullname='M. Duerst'>
<organization /></author>
<author initials='M.' surname='Suignard' fullname='M. Suignard'>
<organization /></author>
<date year='2005' month='January' />
<abstract>
<t><p>This document defines a new protocol element, the Internationalized Resource Identifier (IRI), as a complement of the Uniform Resource Identifier (URI). An IRI is a sequence of characters from the Universal Character Set (Unicode/ISO 10646). A mapping from IRIs to URIs is defined, which means that IRIs can be used instead of URIs, where appropriate, to identify resources.</p><p> The approach of defining a new protocol element was chosen instead of extending or changing the definition of URIs. This was done in order to allow a clear distinction and to avoid incompatibilities with existing software. Guidelines are provided for the use and deployment of IRIs in various protocols, formats, and software components that currently deal with URIs.</p></t></abstract></front>
<seriesInfo name='RFC' value='3987' />
<format type='TXT' octets='111190' target='ftp://ftp.isi.edu/in-notes/rfc3987.txt' />
</reference>

<reference anchor='RFC4422'>
<front>
<title>Simple Authentication and Security Layer (SASL)</title>
<author initials='A.' surname='Melnikov' fullname='A. Melnikov'>
<organization /></author>
<author initials='K.' surname='Zeilenga' fullname='K. Zeilenga'>
<organization /></author>
<date year='2006' month='June' />
<abstract>
<t>The Simple Authentication and Security Layer (SASL) is a framework for providing authentication and data security services in connection-oriented protocols via replaceable mechanisms. It provides a structured interface between protocols and mechanisms. The resulting framework allows new protocols to reuse existing mechanisms and allows old protocols to make use of new mechanisms. The framework also provides a protocol for securing subsequent protocol exchanges within a data security layer.</t><t> This document describes how a SASL mechanism is structured, describes how protocols include support for SASL, and defines the protocol for carrying a data security layer over a connection. In addition, this document defines one SASL mechanism, the EXTERNAL mechanism.</t><t> This document obsoletes RFC 2222. [STANDARDS-TRACK]</t></abstract></front>
<seriesInfo name='RFC' value='4422' />
<format type='TXT' octets='73206' target='http://www.rfc-editor.org/rfc/rfc4422.txt' />
</reference>

<reference anchor='RFC5122'>
<front>
<title>Internationalized Resource Identifiers (IRIs) and Uniform Resource Identifiers (URIs) for the Extensible Messaging and Presence Protocol (XMPP)</title>
<author initials='P.' surname='Saint-Andre' fullname='P. Saint-Andre'>
<organization /></author>
<date year='2008' month='February' />
<abstract>
<t>This document defines the use of Internationalized Resource Identifiers (IRIs) and Uniform Resource Identifiers (URIs) in identifying or interacting with entities that can communicate via the Extensible Messaging and Presence Protocol (XMPP). [STANDARDS TRACK]</t></abstract></front>
<seriesInfo name='RFC' value='5122' />
<format type='TXT' octets='55566' target='ftp://ftp.isi.edu/in-notes/rfc5122.txt' />
</reference>

<reference anchor='RFC5894'>
<front>
<title>Internationalized Domain Names for Applications (IDNA): Background, Explanation, and Rationale</title>
<author initials='J.' surname='Klensin' fullname='J. Klensin'>
<organization /></author>
<date year='2010' month='August' />
<abstract>
<t>Several years have passed since the original protocol for Internationalized Domain Names (IDNs) was completed and deployed.  During that time, a number of issues have arisen, including the need to update the system to deal with newer versions of Unicode.  Some of these issues require tuning of the existing protocols and the tables on which they depend.  This document provides an overview of a revised system and provides explanatory material for its components.  This document is not an Internet Standards Track specification; it is published for informational purposes.</t></abstract></front>
<seriesInfo name='RFC' value='5894' />
<format type='TXT' octets='115174' target='http://www.rfc-editor.org/rfc/rfc5894.txt' />
</reference>

<reference anchor='RFC5895'>
<front>
<title>Mapping Characters for Internationalized Domain Names in Applications (IDNA) 2008</title>
<author initials='P.' surname='Resnick' fullname='P. Resnick'>
<organization /></author>
<author initials='P.' surname='Hoffman' fullname='P. Hoffman'>
<organization /></author>
<date year='2010' month='September' />
<abstract>
<t>In the original version of the Internationalized Domain Names in Applications (IDNA) protocol, any Unicode code points taken from user input were mapped into a set of Unicode code points that "made sense", and then encoded and passed to the domain name system (DNS).  The IDNA2008 protocol (described in RFCs 5890, 5891, 5892, and 5893) presumes that the input to the protocol comes from a set of "permitted" code points, which it then encodes and passes to the DNS, but does not specify what to do with the result of user input.  This document describes the actions that can be taken by an implementation between receiving user input and passing permitted code points to the new IDNA protocol.  This document is not an Internet Standards Track specification; it is published for informational purposes.</t></abstract></front>
<seriesInfo name='RFC' value='5895' />
<format type='TXT' octets='16556' target='http://www.rfc-editor.org/rfc/rfc5895.txt' />
</reference>

<reference anchor='RFC6121'>
<front>
<title>Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence</title>
<author initials='P.' surname='Saint-Andre' fullname='P. Saint-Andre'>
<organization /></author>
<date year='2011' month='March' />
<abstract>
<t>This document defines extensions to core features of the Extensible Messaging and Presence Protocol (XMPP) that provide basic instant messaging (IM) and presence functionality in conformance with the requirements in RFC 2779.  This document obsoletes RFC 3921. [STANDARDS-TRACK]</t></abstract></front>
<seriesInfo name='RFC' value='6121' />
<format type='TXT' octets='244800' target='http://www.rfc-editor.org/rfc/rfc6121.txt' />
</reference>

<reference anchor='RFC6122'>
<front>
<title>Extensible Messaging and Presence Protocol (XMPP): Address Format</title>
<author initials='P.' surname='Saint-Andre' fullname='P. Saint-Andre'>
<organization /></author>
<date year='2011' month='March' />
<abstract>
<t>This document defines the format for addresses used in the Extensible Messaging and Presence Protocol (XMPP), including support for non-ASCII characters.  This document updates RFC 3920. [STANDARDS-TRACK]</t></abstract></front>
<seriesInfo name='RFC' value='6122' />
<format type='TXT' octets='50646' target='http://www.rfc-editor.org/rfc/rfc6122.txt' />
</reference>

<reference anchor='RFC6365'>
<front>
<title>Terminology Used in Internationalization in the IETF</title>
<author initials='P.' surname='Hoffman' fullname='P. Hoffman'>
<organization /></author>
<author initials='J.' surname='Klensin' fullname='J. Klensin'>
<organization /></author>
<date year='2011' month='September' />
<abstract>
<t>This document provides a list of terms used in the IETF when discussing internationalization.  The purpose is to help frame discussions of internationalization in the various areas of the IETF and to help introduce the main concepts to IETF participants.  This memo documents an Internet Best Current Practice.</t></abstract></front>
<seriesInfo name='BCP' value='166' />
<seriesInfo name='RFC' value='6365' />
<format type='TXT' octets='103155' target='http://www.rfc-editor.org/rfc/rfc6365.txt' />
</reference>

<reference anchor='RFC6885'>
<front>
<title>Stringprep Revision and Problem Statement for the Preparation and Comparison of Internationalized Strings (PRECIS)</title>
<author initials='M.' surname='Blanchet' fullname='M. Blanchet'>
<organization /></author>
<author initials='A.' surname='Sullivan' fullname='A. Sullivan'>
<organization /></author>
<date year='2013' month='March' />
<abstract>
<t>If a protocol expects to compare two strings and is prepared only for those strings to be ASCII, then using Unicode code points in those strings requires they be prepared somehow.  Internationalizing Domain Names in Applications (here called IDNA2003) defined and used Stringprep and Nameprep.  Other protocols subsequently defined Stringprep profiles.  A new approach different from Stringprep and Nameprep is used for a revision of IDNA2003 (called IDNA2008).  Other Stringprep profiles need to be similarly updated, or a replacement of Stringprep needs to be designed.  This document outlines the issues to be faced by those designing a Stringprep replacement.</t></abstract></front>
<seriesInfo name='RFC' value='6885' />
<format type='TXT' octets='72167' target='http://www.rfc-editor.org/rfc/rfc6885.txt' />
</reference>

<reference anchor="UTS39" target='http://unicode.org/reports/tr39/'>
  <front>
    <title>Unicode Technical Standard #39: Unicode Security Mechanisms</title>
    <author>
      <organization>The Unicode Consortium</organization>
    </author>
    <date month="July" year="2012" />
  </front>
</reference>

<reference anchor="XEP-0004">
  <front>
    <title>Data Forms</title>
    <author initials="R." surname="Eatmon" fullname="Ryan Eatmon">
      <organization/>
      <address>
        <email>reatmon@jabber.org</email>
      </address>
    </author>
    <author initials="J." surname="Hildebrand" fullname="Joe Hildebrand">
      <organization/>
      <address>
        <email>jhildebr@cisco.com</email>
      </address>
    </author>
    <author initials="J." surname="Miller" fullname="Jeremie Miller">
      <organization/>
      <address>
        <email>jer@jabber.org</email>
      </address>
    </author>
    <author initials="T." surname="Muldowney" fullname="Thomas Muldowney">
      <organization/>
      <address>
        <email>temas@jabber.org</email>
      </address>
    </author>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <date day="13" month="August" year="2007"/>
  </front>
  <seriesInfo name="XSF XEP" value="0004"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0004.html"/>
</reference>

<reference anchor="XEP-0016">
  <front>
    <title>Privacy Lists</title>
    <author initials="P." surname="Millard" fullname="Peter Millard">
      <organization/>
      <address>
        <email/>
      </address>
    </author>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <date day="15" month="February" year="2007"/>
  </front>
  <seriesInfo name="XSF XEP" value="0016"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0016.html"/>
</reference>

<reference anchor="XEP-0029">
  <front>
    <title>Definition of Jabber Identifiers (JIDs)</title>
    <author initials="C." surname="Kaes" fullname="Craig Kaes">
      <organization/>
      <address>
        <email>craigk@jabber.com</email>
      </address>
    </author>
    <date day="03" month="October" year="2003"/>
  </front>
  <seriesInfo name="XSF XEP" value="0029"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0029.html"/>
</reference>

<reference anchor="XEP-0030">
  <front>
    <title>Service Discovery</title>
    <author initials="J." surname="Hildebrand" fullname="Joe Hildebrand">
      <organization/>
      <address>
        <email>jhildebr@cisco.com</email>
      </address>
    </author>
    <author initials="P." surname="Millard" fullname="Peter Millard">
      <organization/>
      <address>
        <email/>
      </address>
    </author>
    <author initials="R." surname="Eatmon" fullname="Ryan Eatmon">
      <organization/>
      <address>
        <email>reatmon@jabber.org</email>
      </address>
    </author>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <date day="06" month="June" year="2008"/>
  </front>
  <seriesInfo name="XSF XEP" value="0030"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0030.html"/>
</reference>

<reference anchor="XEP-0045">
  <front>
    <title>Multi-User Chat</title>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <date day="8" month="February" year="2012"/>
  </front>
  <seriesInfo name="XSF XEP" value="0045"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0045.html"/>
</reference>

<reference anchor="XEP-0048">
  <front>
    <title>Bookmarks</title>
    <author initials="R." surname="Blackman" fullname="Rachel Blackman">
      <organization/>
      <address>
        <email>rcb@ceruleanstudios.com</email>
      </address>
    </author>
    <author initials="P." surname="Millard" fullname="Peter Millard">
      <organization/>
      <address>
        <email/>
      </address>
    </author>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <date day="07" month="November" year="2007"/>
  </front>
  <seriesInfo name="XSF XEP" value="0048"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0048.html"/>
</reference>

<reference anchor="XEP-0054">
  <front>
    <title>vcard-temp</title>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <date day="16" month="July" year="2008"/>
  </front>
  <seriesInfo name="XSF XEP" value="0054"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0054.html"/>
</reference>

<reference anchor="XEP-0060">
  <front>
    <title>Publish-Subscribe</title>
    <author initials="P." surname="Millard" fullname="Peter Millard">
      <organization/>
      <address>
        <email/>
      </address>
    </author>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <author initials="R." surname="Meijer" fullname="Ralph Meijer">
      <organization/>
      <address>
        <email>ralphm@ik.nu</email>
      </address>
    </author>
    <date day="12" month="July" year="2010"/>
  </front>
  <seriesInfo name="XSF XEP" value="0060"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0060.html"/>
</reference>

<reference anchor="XEP-0065">
  <front>
    <title>SOCKS5 Bytestreams</title>
    <author initials="D." surname="Smith" fullname="Dave Smith">
      <organization/>
      <address>
        <email>dizzyd@jabber.org</email>
      </address>
    </author>
    <author initials="M." surname="Miller" fullname="Matthew Miller">
      <organization/>
      <address>
        <email>linuxwolf@outer-planes.net</email>
      </address>
    </author>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <author initials="J." surname="Karneges" fullname="Justin Karneges">
      <organization/>
      <address>
        <email>justin@affinix.com</email>
      </address>
    </author>
    <date day="20" month="April" year="2011"/>
  </front>
  <seriesInfo name="XSF XEP" value="0065"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0065.html"/>
</reference>

<reference anchor="XEP-0077">
  <front>
    <title>In-Band Registration</title>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <date day="25" month="January" year="2012"/>
  </front>
  <seriesInfo name="XSF XEP" value="0077"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0077.html"/>
</reference>

<reference anchor="XEP-0106">
  <front>
    <title>JID Escaping</title>
    <author initials="J." surname="Hildebrand" fullname="Joe Hildebrand">
      <organization/>
      <address>
        <email>jhildebr@cisco.com</email>
      </address>
    </author>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <date day="18" month="June" year="2007"/>
  </front>
  <seriesInfo name="XSF XEP" value="0106"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0106.html"/>
</reference>

<reference anchor="XEP-0114">
  <front>
    <title>Jabber Component Protocol</title>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <date day="03" month="March" year="2005"/>
  </front>
  <seriesInfo name="XSF XEP" value="0114"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0114.html"/>
</reference>

<reference anchor="XEP-0144">
  <front>
    <title>Roster Item Exchange</title>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <date day="26" month="August" year="2005"/>
  </front>
  <seriesInfo name="XSF XEP" value="0144"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0144.html"/>
</reference>

<reference anchor="XEP-0165">
  <front>
    <title>Best Practices to Discourage JID Mimicking</title>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <date day="13" month="December" year="2007"/>
  </front>
  <seriesInfo name="XSF XEP" value="0165"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0045.html"/>
</reference>

<reference anchor="XEP-0166">
  <front>
    <title>Jingle</title>
    <author initials="S." surname="Ludwig" fullname="Scott Ludwig">
      <organization/>
      <address>
        <email>scottlu@google.com</email>
      </address>
    </author>
    <author initials="J." surname="Beda" fullname="Joe Beda">
      <organization/>
      <address>
        <email>jbeda@google.com</email>
      </address>
    </author>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <author initials="R." surname="McQueen" fullname="Robert McQueen">
      <organization/>
      <address>
        <email>robert.mcqueen@collabora.co.uk</email>
      </address>
    </author>
    <author initials="S." surname="Egan" fullname="Sean Egan">
      <organization/>
      <address>
        <email>seanegan@google.com</email>
      </address>
    </author>
    <author initials="J." surname="Hildebrand" fullname="Joe Hildebrand">
      <organization/>
      <address>
        <email>jhildebr@cisco.com</email>
      </address>
    </author>
    <date day="23" month="December" year="2009"/>
  </front>
  <seriesInfo name="XSF XEP" value="0166"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0166.html"/>
</reference>

<reference anchor="XEP-0191">
  <front>
    <title>Blocking Command</title>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <date day="18" month="July" year="2012"/>
  </front>
  <seriesInfo name="XSF XEP" value="0191"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0191.html"/>
</reference>

<reference anchor="XEP-0203">
  <front>
    <title>Delayed Delivery</title>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <date day="15" month="September" year="2009"/>
  </front>
  <seriesInfo name="XSF XEP" value="0203"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0203.html"/>
</reference>

<reference anchor="XEP-0220">
  <front>
    <title>Server Dialback</title>
    <author initials="J." surname="Miller" fullname="Jeremie Miller">
      <organization/>
      <address>
        <email>jer@jabber.org</email>
      </address>
    </author>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <author initials="P." surname="Hancke" fullname="Philipp Hancke">
      <organization/>
      <address>
        <email/>
      </address>
    </author>
    <date day="12" month="August" year="2012"/>
  </front>
  <seriesInfo name="XSF XEP" value="0220"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0220.html"/>
</reference>

<reference anchor="XEP-0292">
  <front>
    <title>vCard4 Over XMPP</title>
    <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre">
      <organization/>
      <address>
        <email>stpeter@jabber.org</email>
      </address>
    </author>
    <author initials="S." surname="Mizzi" fullname="Samantha Mizzi">
      <organization/>
      <address>
        <email>samizzi@cisco.com</email>
      </address>
    </author>
    <date day="09" month="October" year="2011"/>
  </front>
  <seriesInfo name="XSF XEP" value="0292"/>
  <format type="HTML" target="http://xmpp.org/extensions/xep-0292.html"/>
</reference>

<reference anchor='XML' target='http://www.w3.org/TR/2008/REC-xml-20081126'>
<front>
<title>Extensible Markup Language (XML) 1.0 (Fifth Edition)</title>
<author initials='E.' surname='Maler' fullname='Eve Maler'>
    <organization />
</author>
<author initials='F.' surname='Yergeau' fullname='Francois Yergeau'>
    <organization />
</author>
<author initials='C.' surname='Sperberg-McQueen' fullname='C. M. Sperberg-McQueen'>
    <organization />
</author>
<author initials='J.' surname='Paoli' fullname='Jean Paoli'>
    <organization />
</author>
<author initials='T.' surname='Bray' fullname='Tim Bray'>
    <organization />
</author>
<date month='November' day='26' year='2008' />
</front>
<seriesInfo name='World Wide Web Consortium Recommendation' value='REC-xml-20081126' />
<format type='HTML' target='http://www.w3.org/TR/2008/REC-xml-20081126' />
</reference>


    </references>

    <section title="Differences from RFC 6122" anchor="diffs">
      <t>Based on consensus derived from working group discussion, implementation and deployment experience, and formal interoperability testing, the following substantive modifications were made from RFC 6122.</t>
      <t>
        <list style='symbols'>
          <t>Changed domainpart preparation to use IDNA2008 (instead of IDNA2003).</t>
          <t>Changed localpart preparation to use the JIDlocalIdentifierClass profile of the PRECIS IdentifierClass (instead of the Nodeprep profile of Stringprep).</t>
          <t>Changed resourcepart preparation to use the JIDresourceFreeformClass profile of the PRECIS FreeformClass (instead of the Resourceprep profile of Stringprep).</t>
          <t>Specified that internationalized labels within domainparts must be U-labels (instead of "should be" U-labels).</t> 
          <t>Specified that fullwidth and halfwidth characters must be mapped to their decomposition equivalents (previously handled through the use of NFKC).</t>
          <t>Specified the use of Unicode Normalization Form C (instead of Unicode Normalization Form KC as specified in the Nodeprep and Resourceprep profiles of Stringprep).</t>
          <t>Specified that servers must enforce the address formatting rules.</t>
        </list>
      </t>
    </section>

    <section title="Acknowledgements" anchor="acks">
      <t>Thanks to Miguel Garcia, Joe Hildebrand, and Florian Zeitz for their feedback.</t>
      <t>Some text in this document was borrowed or adapted from <xref target='RFC5890'/>, <xref target='RFC5891'/>, <xref target='RFC5894'/>, and <xref target='XEP-0165'/>.</t>
    </section>

  </back>

</rfc>