8.  XML Considerations

   XML serves as the encoding format for SPPF, allowing complex
   hierarchical data to be expressed in a text format that can be read,
   saved, and manipulated with both traditional text tools and tools
   specific to XML.

   XML is case sensitive.  Unless stated otherwise, the character casing
   of XML specifications in this document MUST be preserved to develop a
   conforming specification.

   This section discusses a small number of XML-related considerations
   pertaining to SPPF.

8.1.  Namespaces

   All SPPF elements are defined in the Namespaces in the "IANA
   Considerations" and "Formal Framework Specification" sections of this
   document.

8.2.  Versioning and Character Encoding

   All XML instances SHOULD begin with an <?xml?> declaration to
   identify the version of XML that is being used, optionally identify
   use of the character encoding used, and optionally provide a hint to
   an XML parser that an external schema file is needed to validate the
   XML instance.

   Conformant XML parsers recognize both UTF-8 (defined in [RFC3629])
   and UTF-16 (defined in [RFC2781]); per [RFC2277], UTF-8 is the
   RECOMMENDED character encoding for use with SPPF.

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

   Example XML declarations:

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

9.  Security Considerations

   Many SPPF implementations manage data that is considered confidential
   and critical.  Furthermore, SPPF implementations can support
   provisioning activities for multiple Registrars and Registrants.  As
   a result, any SPPF implementation must address the requirements for
   confidentiality, authentication, and authorization.

9.1.  Confidentiality and Authentication

   With respect to confidentiality and authentication, the substrate
   protocol requirements section of this document contains security
   properties that the substrate protocol must provide, so that
   authenticated endpoints can exchange data confidentially and with
   integrity protection.  Refer to Section 4 of this document and
   [RFC7878] for the specific solutions to authentication and
   confidentiality.

9.2.  Authorization

   With respect to authorization, the SPPF server implementation must
   define and implement a set of authorization rules that precisely
   address (1) which Registrars will be authorized to create/modify/
   delete each SPPF object type for a given Registrant(s) and (2) which
   Registrars will be authorized to view/get each SPPF object type for a
   given Registrant(s).  These authorization rules are a matter of
   policy and are not specified within the context of SPPF.  However,
   any SPPF implementation must specify these authorization rules in
   order to function in a reliable and safe manner.

9.3.  Denial of Service

   In general, guidance on Denial-of-Service (DoS) issues is given in
   "Internet Denial of Service Considerations" [RFC4732], which also
   gives a general vocabulary for describing the DoS issue.

   SPPF is a high-level client-server protocol that can be implemented
   on lower-level mechanisms such as remote procedure call and web-
   service API protocols.  As such, it inherits any Denial-of-Service
   issues inherent to the specific lower-level mechanism used for any
   implementation of SPPF.  SPPF also has its own set of higher-level
   exposures that are likely to be independent of lower-layer mechanism
   choices.

9.3.1.  DoS Issues Inherited from the Substrate Mechanism

   In general, an SPPF implementation is dependent on the selection and
   implementation of a lower-level substrate protocol and a binding
   between that protocol and SPPF.  The archetypal SPPF implementation
   uses XML [W3C.REC-xml-20081126] representation in a SOAP [SOAPREF]
   request/response framework over HTTP [RFC7230], probably also uses
   Transport Layer Security (TLS) [RFC5246] for on-the-wire data
   integrity and participant authentication, and might use HTTP Digest
   authentication [RFC2069].

   The typical deployment scenario for SPPF is to have servers in a
   managed facility; therefore, techniques such as Network Ingress
   Filtering [RFC2827] are generally applicable.  In short, any DoS
   mechanism affecting a typical HTTP implementation would affect such
   an SPPF implementation; therefore, the mitigation tools for HTTP in
   general also apply to SPPF.

   SPPF does not directly specify an authentication mechanism; instead,
   it relies on the lower-level substrate protocol to provide for
   authentication.  In general, authentication is an expensive
   operation, and one apparent attack vector is to flood an SPPF server
   with repeated requests for authentication, thereby exhausting its
   resources.  Therefore, SPPF implementations SHOULD be prepared to
   handle authentication floods, perhaps by noting repeated failed login
   requests from a given source address and blocking that source
   address.

9.3.2.  DoS Issues Specific to SPPF

   The primary defense mechanism against DoS within SPPF is
   authentication.  Implementations MUST tightly control access to the
   SPPF service, SHOULD implement DoS and other policy control
   screening, and MAY employ a variety of policy violation reporting and
   response measures such as automatic blocking of specific users and
   alerting of operations personnel.  In short, the primary SPPF
   response to DoS-like activity by a user is to block that user or
   subject their actions to additional review.

   SPPF allows a client to submit multiple-element or "batch" requests
   that may insert or otherwise affect a large amount of data with a
   single request.  In the simplest case, the server progresses
   sequentially through each element in a batch, completing one before
   starting the next.  Mid-batch failures are handled by stopping the
   batch and rolling back the data store to its pre-request state.  This
   "stop and roll back" design provides a DoS opportunity.  A hostile
   client could repeatedly issue large batch requests with one or more
   failing elements, causing the server to repeatedly stop and roll back

   large transactions.  The suggested response is to monitor clients for
   such failures and take administrative action (such as blocking the
   user) when an excessive number of rollbacks is reported.

   An additional suggested response is for an implementer to set their
   maximum allowable XML message size and their maximum allowable batch
   size at a level that they feel protects their operational instance,
   given the hardware sizing they have in place and the expected load
   and size needs that their users expect.

9.4.  Information Disclosure

   It is not uncommon for the logging systems to document on-the-wire
   messages for various purposes, such as debugging, auditing, and
   tracking.  At the minimum, the various support and administration
   staff will have access to these logs.  Also, if an unprivileged user
   gains access to the SPPF deployments and/or support systems, it will
   have access to the information that is potentially deemed
   confidential.  To manage information disclosure concerns beyond the
   substrate level, SPPF implementations MAY provide support for
   encryption at the SPPF object level.

9.5.  Non-repudiation

   In some situations, it may be required to protect against denial of
   involvement (see [RFC4949]) and tackle non-repudiation concerns in
   regard to SPPF messages.  This type of protection is useful to
   satisfy authenticity concerns related to SPPF messages beyond the
   end-to-end connection integrity, confidentiality, and authentication
   protection that the substrate layer provides.  This is an optional
   feature, and some SPPF implementations MAY provide support for it.

9.6.  Replay Attacks

   Anti-replay protection ensures that a given SPPF object replayed at a
   later time won't affect the integrity of the system.  SPPF provides
   at least one mechanism to fight against replay attacks.  Use of the
   optional client transaction identifier allows the SPPF client to
   correlate the request message with the response and to be sure that
   it is not a replay of a server response from earlier exchanges.  Use
   of unique values for the client transaction identifier is highly
   encouraged to avoid chance matches to a potential replay message.

9.7.  Compromised or Malicious Intermediary

   The SPPF client or Registrar can be a separate entity acting on
   behalf of the Registrant in facilitating provisioning transactions to
   the Registry.  Therefore, even though the substrate layer provides
   end-to-end protection for each specific SPPP connection between
   client and server, data might be available in clear text before or
   after it traverses an SPPP connection.  Therefore, a
   man-in-the-middle attack by one of the intermediaries is a
   possibility that could affect the integrity of the data that belongs
   to the Registrant and/or expose peering data to unintended actors.

10.  Internationalization Considerations

   Character encodings to be used for SPPF elements are described in
   Section 8.2.  The use of time elements in the protocol is specified
   in Section 3.2.  Where human-readable messages that are presented to
   an end user are used in the protocol, those messages SHOULD be tagged
   according to [RFC5646], and the substrate protocol MUST support a
   respective mechanism to transmit such tags together with those human-
   readable messages.

11.  IANA Considerations

11.1.  URN Assignments

   This document uses URNs to describe XML Namespaces and XML Schemas
   conforming to a Registry mechanism described in [RFC3688].

   Two URI assignments have been made:

   Registration for the SPPF XML Namespace:
   urn:ietf:params:xml:ns:sppf:base:1
   Registrant Contact: The IESG
   XML: None.  Namespace URIs do not represent an XML specification.

   Registration request for the XML Schema:

   URI: urn:ietf:params:xml:schema:sppf:1
   Registrant Contact: IESG
   XML: See "Formal Specification" (Section 12 of this document).

11.2.  Organization Identifier Namespace Registry

   IANA has created and will maintain a registry titled "SPPF OrgIdType
   Namespaces".  The formal syntax is described in Section 5.1.

   Assignments consist of the OrgIdType Namespace string and the
   definition of the associated Namespace.  This document makes the
   following initial assignment for the OrgIdType Namespaces:

         OrgIdType Namespace string                       Namespace
         --------------------------                       ---------
         IANA Enterprise Numbers                          iana-en

   Future assignments are to be made through the well-known IANA Policy
   "RFC Required" (see Section 4.1 of [RFC5226]).  Such assignments will
   typically be requested when a new Namespace for identification of SPs
   is defined.

12.  Formal Specification

   This section provides the XSD for the SPPF protocol.

   <?xml version="1.0" encoding="UTF-8"?>
   <schema xmlns:sppfb="urn:ietf:params:xml:ns:sppf:base:1"
   xmlns="http://www.w3.org/2001/XMLSchema"
   targetNamespace="urn:ietf:params:xml:ns:sppf:base:1"
   elementFormDefault="qualified" xml:lang="EN">
    <annotation>
     <documentation>
      ---- Generic object key types to be defined by specific
           substrate/architecture.  The types defined here can
           be extended by the specific architecture to
           define the Object Identifiers. ----
     </documentation>
    </annotation>
    <complexType name="ObjKeyType"
     abstract="true">
     <annotation>
      <documentation>
       ---- Generic type that represents the
            key for various objects in SPPF. ----
      </documentation>
     </annotation>
    </complexType>

    <complexType name="SedGrpOfferKeyType" abstract="true">
     <complexContent>
      <extension base="sppfb:ObjKeyType">
       <annotation>
        <documentation>
        ---- Generic type that represents
             the key for a SED Group Offer. ----
        </documentation>
       </annotation>
      </extension>
     </complexContent>
    </complexType>

    <complexType name="PubIdKeyType" abstract="true">
     <complexContent>
      <extension base="sppfb:ObjKeyType">
       <annotation>
        <documentation>
         ----Generic type that
         represents the key
         for a Pub ID. ----
        </documentation>
       </annotation>
      </extension>
     </complexContent>
    </complexType>

    <annotation>
     <documentation>
       ---- Object Type Definitions ----
     </documentation>
    </annotation>

    <complexType name="SedGrpType">
     <complexContent>
      <extension base="sppfb:BasicObjType">
       <sequence>
        <element name="sedGrpName" type="sppfb:ObjNameType"/>
        <element name="sedRecRef" type="sppfb:SedRecRefType"
                 minOccurs="0" maxOccurs="unbounded"/>
        <element name="dgName" type="sppfb:ObjNameType"
                 minOccurs="0" maxOccurs="unbounded"/>
        <element name="peeringOrg" type="sppfb:OrgIdType"
                 minOccurs="0" maxOccurs="unbounded"/>
        <element name="sourceIdent" type="sppfb:SourceIdentType"
                 minOccurs="0" maxOccurs="unbounded"/>
        <element name="isInSvc" type="boolean"/>
        <element name="priority" type="unsignedShort"/>

        <element name="ext"
        type="sppfb:ExtAnyType" minOccurs="0"/>
       </sequence>
      </extension>
     </complexContent>
    </complexType>
    <complexType name="DestGrpType">
     <complexContent>
      <extension base="sppfb:BasicObjType">
       <sequence>
        <element name="dgName"
        type="sppfb:ObjNameType"/>
       </sequence>
      </extension>
     </complexContent>
    </complexType>
    <complexType name="PubIdType" abstract="true">
     <complexContent>
      <extension base="sppfb:BasicObjType">
       <sequence>
        <element name="dgName" type="sppfb:ObjNameType"
                 minOccurs="0" maxOccurs="unbounded"/>
       </sequence>
      </extension>
     </complexContent>
    </complexType>
    <complexType name="TNType">
     <complexContent>
      <extension base="sppfb:PubIdType">
       <sequence>
        <element name="tn" type="sppfb:NumberValType"/>
        <element name="corInfo" type="sppfb:CORInfoType" minOccurs="0"/>
        <element name="sedRecRef" type="sppfb:SedRecRefType"
                 minOccurs="0" maxOccurs="unbounded"/>
       </sequence>
      </extension>
     </complexContent>
    </complexType>
    <complexType name="TNRType">
     <complexContent>
      <extension base="sppfb:PubIdType">
       <sequence>
        <element name="range" type="sppfb:NumberRangeType"/>
        <element name="corInfo" type="sppfb:CORInfoType" minOccurs="0"/>
       </sequence>
      </extension>
     </complexContent>
    </complexType>

    <complexType name="TNPType">
     <complexContent>
      <extension base="sppfb:PubIdType">
       <sequence>
        <element name="tnPrefix" type="sppfb:NumberValType"/>
        <element name="corInfo" type="sppfb:CORInfoType" minOccurs="0"/>
       </sequence>
      </extension>
     </complexContent>
    </complexType>
    <complexType name="RNType">
     <complexContent>
      <extension base="sppfb:PubIdType">
       <sequence>
        <element name="rn" type="sppfb:NumberValType"/>
        <element name="corInfo" type="sppfb:CORInfoType" minOccurs="0"/>
       </sequence>
      </extension>
     </complexContent>
    </complexType>
     <complexType name="URIPubIdType">
     <complexContent>
      <extension base="sppfb:PubIdType">
       <sequence>
        <element name="uri" type="anyURI"/>
        <element name="ext" type="sppfb:ExtAnyType" minOccurs="0"/>
       </sequence>
      </extension>
     </complexContent>
    </complexType>
    <complexType name="SedRecType" abstract="true">
     <complexContent>
      <extension base="sppfb:BasicObjType">
       <sequence>
        <element name="sedName" type="sppfb:ObjNameType"/>
        <element name="sedFunction" type="sppfb:SedFunctionType"
                 minOccurs="0"/>
        <element name="isInSvc" type="boolean"/>
        <element name="ttl" type="positiveInteger" minOccurs="0"/>
       </sequence>
      </extension>
     </complexContent>
    </complexType>
    <complexType name="NAPTRType">
     <complexContent>
      <extension base="sppfb:SedRecType">
       <sequence>
        <element name="order" type="unsignedShort"/>

        <element name="flags" type="sppfb:FlagsType" minOccurs="0"/>
        <element name="svcs" type="sppfb:SvcType"/>
        <element name="regx" type="sppfb:RegexParamType" minOccurs="0"/>
        <element name="repl" type="sppfb:ReplType" minOccurs="0"/>
        <element name="ext" type="sppfb:ExtAnyType" minOccurs="0"/>
       </sequence>
      </extension>
     </complexContent>
    </complexType>
    <complexType name="NSType">
     <complexContent>
      <extension base="sppfb:SedRecType">
       <sequence>
        <element name="hostName" type="token"/>
        <element name="ipAddr" type="sppfb:IPAddrType"
                 minOccurs="0" maxOccurs="unbounded"/>
        <element name="ext" type="sppfb:ExtAnyType" minOccurs="0"/>
       </sequence>
      </extension>
     </complexContent>
    </complexType>
    <complexType name="URIType">
     <complexContent>
      <extension base="sppfb:SedRecType">
       <sequence>
        <element name="ere" type="token" default="^(.*)$"/>
        <element name="uri" type="anyURI"/>
        <element name="ext" type="sppfb:ExtAnyType" minOccurs="0"/>
       </sequence>
      </extension>
     </complexContent>
    </complexType>
    <complexType name="SedGrpOfferType">
     <complexContent>
      <extension base="sppfb:BasicObjType">
       <sequence>
        <element name="sedGrpOfferKey" type="sppfb:SedGrpOfferKeyType"/>
        <element name="status" type="sppfb:SedGrpOfferStatusType"/>
        <element name="offerDateTime" type="dateTime"/>
        <element name="acceptDateTime" type="dateTime" minOccurs="0"/>
        <element name="ext" type="sppfb:ExtAnyType" minOccurs="0"/>
       </sequence>
      </extension>
     </complexContent>
    </complexType>
    <complexType name="EgrRteType">
     <complexContent>
      <extension base="sppfb:BasicObjType">

       <sequence>
        <element name="egrRteName" type="sppfb:ObjNameType"/>
        <element name="pref" type="unsignedShort"/>
        <element name="regxRewriteRule" type="sppfb:RegexParamType"/>
        <element name="ingrSedGrp" type="sppfb:ObjKeyType"
                 minOccurs="0" maxOccurs="unbounded"/>
        <element name="svcs" type="sppfb:SvcType" minOccurs="0"/>
        <element name="ext" type="sppfb:ExtAnyType" minOccurs="0"/>
       </sequence>
      </extension>
     </complexContent>
    </complexType>
    <annotation>
     <documentation>
      ---- Abstract Object and Element Type Definitions ----
     </documentation>
    </annotation>
    <complexType name="BasicObjType" abstract="true">
     <sequence>
      <element name="rant" type="sppfb:OrgIdType"/>
      <element name="rar" type="sppfb:OrgIdType"/>
      <element name="cDate" type="dateTime" minOccurs="0"/>
      <element name="mDate" type="dateTime" minOccurs="0"/>
      <element name="ext" type="sppfb:ExtAnyType" minOccurs="0"/>
     </sequence>
    </complexType>
    <complexType name="RegexParamType">
     <sequence>
      <element name="ere" type="sppfb:RegexType" default="^(.*)$"/>
      <element name="repl" type="sppfb:ReplType"/>
     </sequence>
    </complexType>
    <complexType name="IPAddrType">
     <sequence>
      <element name="addr" type="sppfb:AddrStringType"/>
      <element name="ext" type="sppfb:ExtAnyType" minOccurs="0"/>
     </sequence>
     <attribute name="type" type="sppfb:IPType" default="v4"/>
    </complexType>
    <complexType name="SedRecRefType">
     <sequence>
      <element name="sedKey" type="sppfb:ObjKeyType"/>
      <element name="priority" type="unsignedShort"/>
      <element name="ext" type="sppfb:ExtAnyType" minOccurs="0"/>
     </sequence>
    </complexType>
    <complexType name="SourceIdentType">
     <sequence>

      <element name="sourceIdentRegex" type="sppfb:RegexType"/>
      <element name="sourceIdentScheme"
               type="sppfb:SourceIdentSchemeType"/>
      <element name="ext" type="sppfb:ExtAnyType" minOccurs="0"/>
     </sequence>
    </complexType>
    <complexType name="CORInfoType">
     <sequence>
      <element name="corClaim" type="boolean" default="true"/>
      <element name="cor" type="boolean" default="false" minOccurs="0"/>
      <element name="corDate" type="dateTime" minOccurs="0"/>
     </sequence>
    </complexType>
    <complexType name="SvcMenuType">
     <sequence>
      <element name="serverStatus" type="sppfb:ServerStatusType"/>
      <element name="majMinVersion" type="token" maxOccurs="unbounded"/>
      <element name="objURI" type="anyURI" maxOccurs="unbounded"/>
      <element name="extURI" type="anyURI"
               minOccurs="0" maxOccurs="unbounded"/>
     </sequence>
    </complexType>
    <complexType name="ExtAnyType">
     <sequence>
      <any namespace="##other" maxOccurs="unbounded"/>
     </sequence>
    </complexType>
    <simpleType name="FlagsType">
     <restriction base="token">
      <length value="1"/>
      <pattern value="[A-Z]|[a-z]|[0-9]"/>
     </restriction>
    </simpleType>
    <simpleType name="SvcType">
     <restriction base="token">
      <minLength value="1"/>
     </restriction>
    </simpleType>
    <simpleType name="RegexType">
     <restriction base="token">
      <minLength value="1"/>
     </restriction>
    </simpleType>
    <simpleType name="ReplType">
     <restriction base="token">
      <minLength value="1"/>
      <maxLength value="255"/>
     </restriction>

    </simpleType>
    <simpleType name="OrgIdType">
     <restriction base="token"/>
    </simpleType>
    <simpleType name="ObjNameType">
     <restriction base="token">
      <minLength value="3"/>
      <maxLength value="80"/>
     </restriction>
    </simpleType>
    <simpleType name="TransIdType">
     <restriction base="token">
      <minLength value="3"/>
      <maxLength value="120"/>
     </restriction>
    </simpleType>
    <simpleType name="MinorVerType">
     <restriction base="unsignedLong"/>
    </simpleType>
    <simpleType name="AddrStringType">
     <restriction base="token">
      <minLength value="3"/>
      <maxLength value="45"/>
     </restriction>
    </simpleType>
    <simpleType name="IPType">
     <restriction base="token">
      <enumeration value="v4"/>
      <enumeration value="v6"/>
     </restriction>
    </simpleType>
    <simpleType name="SourceIdentSchemeType">
     <restriction base="token">
      <enumeration value="uri"/>
      <enumeration value="ip"/>
      <enumeration value="rootDomain"/>
     </restriction>
    </simpleType>
    <simpleType name="ServerStatusType">
     <restriction base="token">
      <enumeration value="inService"/>
      <enumeration value="outOfService"/>
     </restriction>
    </simpleType>
    <simpleType name="SedGrpOfferStatusType">
     <restriction base="token">
      <enumeration value="offered"/>
      <enumeration value="accepted"/>

     </restriction>
    </simpleType>
    <simpleType name="NumberValType">
     <restriction base="token">
      <maxLength value="20"/>
      <pattern value="\+?\d\d*"/>
     </restriction>
    </simpleType>
    <simpleType name="NumberTypeEnum">
     <restriction base="token">
      <enumeration value="TN"/>
      <enumeration value="TNPrefix"/>
      <enumeration value="RN"/>
     </restriction>
    </simpleType>
    <simpleType name="SedFunctionType">
     <restriction base="token">
      <enumeration value="routing"/>
      <enumeration value="lookup"/>
     </restriction>
    </simpleType>
    <complexType name="NumberType">
     <sequence>
      <element name="value" type="sppfb:NumberValType"/>
      <element name="type" type="sppfb:NumberTypeEnum"/>
     </sequence>
    </complexType>
    <complexType name="NumberRangeType">
     <sequence>
      <element name="startRange" type="sppfb:NumberValType"/>
      <element name="endRange" type="sppfb:NumberValType"/>
     </sequence>
    </complexType>
   </schema>

13.  References

13.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2277]  Alvestrand, H., "IETF Policy on Character Sets and
              Languages", BCP 18, RFC 2277, DOI 10.17487/RFC2277,
              January 1998, <http://www.rfc-editor.org/info/rfc2277>.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
              2003, <http://www.rfc-editor.org/info/rfc3629>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <http://www.rfc-editor.org/info/rfc3688>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <http://www.rfc-editor.org/info/rfc3986>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <http://www.rfc-editor.org/info/rfc5234>.

   [RFC7878]  Cartwright, K., Bhatia, V., Mule, J., and A. Mayrhofer,
              "Session Peering Provisioning (SPP) Protocol over SOAP",
              RFC 7878, DOI 10.17487/RFC7878, August 2016,
              <http://www.rfc-editor.org/info/rfc7878>.

   [W3C.REC-xml-20081126]
              Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and
              F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth
              Edition)", World Wide Web Consortium Recommendation REC-
              xml-20081126, November 2008,
              <http://www.w3.org/TR/2008/REC-xml-20081126>.

13.2.  Informative References

   [RFC2069]  Franks, J., Hallam-Baker, P., Hostetler, J., Leach, P.,
              Luotonen, A., Sink, E., and L. Stewart, "An Extension to
              HTTP : Digest Access Authentication", RFC 2069,
              DOI 10.17487/RFC2069, January 1997,
              <http://www.rfc-editor.org/info/rfc2069>.

   [RFC2781]  Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO
              10646", RFC 2781, DOI 10.17487/RFC2781, February 2000,
              <http://www.rfc-editor.org/info/rfc2781>.

   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
              May 2000, <http://www.rfc-editor.org/info/rfc2827>.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,
              <http://www.rfc-editor.org/info/rfc3261>.

   [RFC3403]  Mealling, M., "Dynamic Delegation Discovery System (DDDS)
              Part Three: The Domain Name System (DNS) Database",
              RFC 3403, DOI 10.17487/RFC3403, October 2002,
              <http://www.rfc-editor.org/info/rfc3403>.

   [RFC4725]  Mayrhofer, A. and B. Hoeneisen, "ENUM Validation
              Architecture", RFC 4725, DOI 10.17487/RFC4725, November
              2006, <http://www.rfc-editor.org/info/rfc4725>.

   [RFC4732]  Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
              Denial-of-Service Considerations", RFC 4732,
              DOI 10.17487/RFC4732, December 2006,
              <http://www.rfc-editor.org/info/rfc4732>.

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
              FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
              <http://www.rfc-editor.org/info/rfc4949>.

   [RFC5067]  Lind, S. and P. Pfautz, "Infrastructure ENUM
              Requirements", RFC 5067, DOI 10.17487/RFC5067, November
              2007, <http://www.rfc-editor.org/info/rfc5067>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <http://www.rfc-editor.org/info/rfc5246>.

   [RFC5486]  Malas, D., Ed. and D. Meyer, Ed., "Session Peering for
              Multimedia Interconnect (SPEERMINT) Terminology",
              RFC 5486, DOI 10.17487/RFC5486, March 2009,
              <http://www.rfc-editor.org/info/rfc5486>.

   [RFC5646]  Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
              Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646,
              September 2009, <http://www.rfc-editor.org/info/rfc5646>.

   [RFC6116]  Bradner, S., Conroy, L., and K. Fujiwara, "The E.164 to
              Uniform Resource Identifiers (URI) Dynamic Delegation
              Discovery System (DDDS) Application (ENUM)", RFC 6116,
              DOI 10.17487/RFC6116, March 2011,
              <http://www.rfc-editor.org/info/rfc6116>.

   [RFC6461]  Channabasappa, S., Ed., "Data for Reachability of Inter-
              /Intra-NetworK SIP (DRINKS) Use Cases and Protocol
              Requirements", RFC 6461, DOI 10.17487/RFC6461, January
              2012, <http://www.rfc-editor.org/info/rfc6461>.

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,
              <http://www.rfc-editor.org/info/rfc7230>.

   [SOAPREF]  Gudgin, M., Hadley, M., Moreau, J., and H. Nielsen, "SOAP
              Version 1.2 Part 1: Messaging Framework", W3C REC REC-
              SOAP12-part1-20030624, June 2003,
              <http://www.w3.org/TR/soap12-part1/>.

   [Unicode6.1]
              The Unicode Consortium, "The Unicode Standard, Version
              6.1.0", (Mountain View, CA: The Unicode Consortium,
              2012. ISBN 978-1-936213-02-3),
              <http://unicode.org/versions/Unicode6.1.0/>.

Acknowledgements

   This document is a result of various discussions held in the DRINKS
   working group and within the DRINKS protocol design team, with
   contributions from the following individuals, in alphabetical order:
   Syed Ali, Jeremy Barkan, Vikas Bhatia, Sumanth Channabasappa, Lisa
   Dusseault, Deborah A.  Guyton, Otmar Lendl, Manjul Maharishi, Mickael
   Marrache, Alexander Mayrhofer, Samuel Melloul, David Schwartz, and
   Richard Shockey.

Authors' Addresses

   Kenneth Cartwright
   TNS
   1939 Roland Clarke Place
   Reston, VA  20191
   United States

   Email: kcartwright@tnsi.com


   Vikas Bhatia
   TNS
   1939 Roland Clarke Place
   Reston, VA  20191
   United States

   Email: vbhatia@tnsi.com


   Syed Wasim Ali
   NeuStar
   46000 Center Oak Plaza
   Sterling, VA  20166
   United States

   Email: syed.ali@neustar.biz


   David Schwartz
   XConnect
   316 Regents Park Road
   London  N3 2XJ
   United Kingdom

   Email: dschwartz@xconnect.net