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IETF RFC 6915
Last modified on Thursday, April 11th, 2013
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Internet Engineering Task Force (IETF) R. Bellis
Request for Comments: 6915 Nominet UK
Updates: 6155 April 2013
Category: Standards Track
ISSN: 2070-1721
Flow Identity Extension for HTTP-Enabled Location Delivery (HELD)
 Abstract
RFC 6155 specifies an extension for the HTTP-Enabled Location
Delivery (HELD) protocol, allowing the use of an IP address and port
number to request a Device location based on an individual packet
flow.
However, certain kinds of NAT require that identifiers for both ends
of the packet flow must be specified in order to unambiguously
satisfy the location request.
This document specifies an XML Schema and a URN Sub-Namespace for a
Flow Identity Extension for HELD to support this requirement.
This document updates RFC 6155 by deprecating the port number
elements specified therein.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/RFC 6915.
Bellis Standards Track PAGE 1 
RFC 6915 Flow Identity for HELD April 2013
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5.1. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:held:flow . . . . . . . . . 6
5.2. XML Schema Registration . . . . . . . . . . . . . . . . . 7
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . . 8
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RFC 6915 Flow Identity for HELD April 2013
1. Introduction
Work at the Emergency Location Task Group of NICC Standards Limited
(the UK's telecoms industry standards body) prompted the addition of
port number identifiers in HELD Identity [RFC 6155] to allow HELD
[RFC 5985] requests for Devices that are behind NAT devices.
Subsequent analysis has determined that in the presence of particular
types of NAT devices, and in particular Carrier Grade NATs, it is
necessary to know the complete tuple of (Layer 3 protocol, Layer 4
protocol, source address, source port, destination address,
destination port) in order to unambiguously identify a flow, and
subsequently the true Device.
This document specifies an XML Schema and a URN Sub-Namespace for a
Flow Identity Extension to support this requirement and provides a
more generally applicable means of identifying a Device based on the
parameters of a network flow of which it is an endpoint.
Since the Location Recipient may not know in advance whether the
Device is behind a NAT device, the port number elements from Section
3.3 of [RFC 6155] are deprecated and MUST NOT be used in new client
implementations. Note that server implementations of this
specification may still encounter requests formed by clients that
have implemented only [RFC 6155], and those requests might contain the
deprecated port element.
For implementation details not specified in this document, please
refer to [RFC 6155] and [RFC 5985].
2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC 2119].
The terms "Device" and "Target" are used as defined in [RFC 6280].
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RFC 6915 Flow Identity for HELD April 2013
3. Usage
An example HELD request is shown below:
<locationRequest xmlns="urn:ietf:params:xml:ns:geopriv:held"
responseTime="8">
<locationType exact="true">geodetic</locationType>
<flow xmlns="urn:ietf:params:xml:ns:geopriv:held:flow"
layer4="tcp" layer3="ipv4">
<src>
<address>192.0.2.25</address>
<port>1024</port>
</src>
<dst>
<address>198.51.100.238</address>
<port>80</port>
</dst>
</flow>
</locationRequest>
The <flow> element MUST contain:
o a "layer3" attribute with a value of "ipv4" or "ipv6".
o a "layer4" attribute with a value of "udp" [RFC 768], "tcp"
[RFC 793], "sctp" [RFC 4960], "dccp" [RFC 4340], or a decimal
integer representing any applicable protocol from the IANA
Assigned Internet Protocol Numbers Registry.
o an <src> element and a <dst> element whose child elements contain
the Layer 3 address (which MUST conform to the relevant
"IPv4address" or "IPv6address" grammar as defined in [RFC 3986])
and the Layer 4 port number of each end of the flow.
and MAY optionally contain:
o a "target" attribute with a value of "src" (default) or "dst" to
indicate which end of the flow corresponds to the Target of the
<locationRequest> with respect to the HELD protocol.
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RFC 6915 Flow Identity for HELD April 2013
4. XML Schema
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema targetNamespace="urn:ietf:params:xml:ns:geopriv:held:flow"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:flow="urn:ietf:params:xml:ns:geopriv:held:flow"
elementFormDefault="qualified">
<xs:annotation>
<xs:appinfo
source="urn:ietf:params:xml:schema:geopriv:held:flow">
HELD Flow Identity</xs:appinfo>
<xs:documentation
source="http://www.rfc-editor.org/rfc/RFC 6915.txt">
This document defines Flow Identity elements for HELD.
</xs:documentation>
</xs:annotation>
<xs:element name="flow" type="flow:flowIdentity"/>
<xs:complexType name="flowIdentity">
<xs:sequence>
<xs:element name="src" type="flow:flowEndpoint"/>
<xs:element name="dst" type="flow:flowEndpoint"/>
</xs:sequence>
<xs:attribute name="target" default="src">
<xs:simpleType>
<xs:restriction base="xs:token">
<xs:pattern value="(src|dst)"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<xs:attribute name="layer3" use="required">
<xs:simpleType>
<xs:restriction base="xs:token">
<xs:pattern value="(ipv4|ipv6)"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<xs:attribute name="layer4" use="required">
<xs:simpleType>
<xs:restriction base="xs:token">
<xs:pattern value="(udp|tcp|sctp|dccp|\d+)"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
</xs:complexType>
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RFC 6915 Flow Identity for HELD April 2013
<xs:complexType name="flowEndpoint">
<xs:all>
<xs:element name="address">
<xs:simpleType>
<xs:restriction base="xs:token"/>
</xs:simpleType>
</xs:element>
<xs:element name="port">
<xs:simpleType>
<xs:restriction base="xs:unsignedShort">
<xs:minInclusive value="1"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
</xs:all>
</xs:complexType>
</xs:schema>
5. IANA Considerations
5.1. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:held:flow
This section registers a new XML namespace,
"urn:ietf:params:xml:ns:geopriv:held:flow", as per the guidelines in
[RFC 3688].
URI: urn:ietf:params:xml:ns:geopriv:held:flow
Registrant Contact: IETF GEOPRIV Working Group (geopriv@ietf.org),
Ray Bellis (ray.bellis@nominet.org.uk)
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RFC 6915 Flow Identity for HELD April 2013
XML:
BEGIN
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<title>HELD Flow Identity Parameters</title>
</head>
<body>
<h1>Namespace for HELD Flow Identity Parameters</h1>
<h2>urn:ietf:params:xml:ns:geopriv:held:flow</h2>
<p>See <a href="http://www.rfc-editor.org/rfc/RFC 6915.txt">
RFC 6915</a>.</p>
</body>
</html>
END
5.2. XML Schema Registration
This section registers an XML Schema as per the guidelines in
[RFC 3688].
URI: urn:ietf:params:xml:ns:geopriv:held:flow
Registrant Contact: IETF GEOPRIV Working Group (geopriv@ietf.org),
Ray Bellis (ray.bellis@nominet.org.uk)
Schema: The XML for this schema can be found as the entirety of
Section 4 of this document.
6. Privacy Considerations
All of the considerations in [RFC 6155] apply to the use of the
mechanism defined in this document. Like [RFC 6155], this
specification assumes that the Location Server being queried already
has access to the internal state of the network near one end of the
flow being queried (for instance, access to the bindings in a NAT in
the path of the flow). Clients making queries using this
specification in environments where that assumption may not be true
should be aware that the request provides information about that
client's communications that the Location Server would not otherwise
be able to discern and may represent additional privacy exposure for
that client.
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RFC 6915 Flow Identity for HELD April 2013
7. Security Considerations
This document introduces no new security considerations beyond those
in [RFC 6155].
8. Acknowledgements
The author wishes to thank the members of the NICC Emergency Location
Task Group, the IETF GeoPriv Working Group, and the authors of
[RFC 6155], from which the text for the URN and XML Schema
Registrations were derived.
9. References
9.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
[RFC 3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC
3986, January 2005.
[RFC 5985] Barnes, M., "HTTP-Enabled Location Delivery (HELD)", RFC
5985, September 2010.
[RFC 6155] Winterbottom, J., Thomson, M., Tschofenig, H., and R.
Barnes, "Use of Device Identity in HTTP-Enabled Location
Delivery (HELD)", RFC 6155, March 2011.
9.2. Informative References
[RFC 768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC 793] Postel, J., "Transmission Control Protocol", STD 7, RFC
793, September 1981.
[RFC 4340] Kohler, E., Handley, M., and S. Floyd, "Datagram
Congestion Control Protocol (DCCP)", RFC 4340, March 2006.
[RFC 4960] Stewart, R., "Stream Control Transmission Protocol", RFC
4960, September 2007.
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RFC 6915 Flow Identity for HELD April 2013
[RFC 6280] Barnes, R., Lepinski, M., Cooper, A., Morris, J.,
Tschofenig, H., and H. Schulzrinne, "An Architecture for
Location and Location Privacy in Internet Applications",
BCP 160, RFC 6280, July 2011.
Author's Address
Ray Bellis
Nominet UK
Edmund Halley Road
Oxford OX4 4DQ
United Kingdom
Phone: +44 1865 332211
EMail: ray.bellis@nominet.org.uk
URI: http://www.nominet.org.uk/
Bellis Standards Track PAGE 9
RFC TOTAL SIZE: 14175 bytes
PUBLICATION DATE: Thursday, April 11th, 2013
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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