Internet DRAFT - draft-winterbottom-sipcore-locparam
draft-winterbottom-sipcore-locparam
SIPCORE J. Winterbottom
Internet-Draft Winterb Consulting Services
Updates: RFC6442 (if approved) R. Jesske
Intended status: Standards Track Deutsche Telekom
Expires: November 30, 2018 B. Chatras
Orange Labs
A. Hutton
Unify
May 29, 2018
Location Source Parameter for the SIP Geolocation Header Field
draft-winterbottom-sipcore-locparam-03.txt
Abstract
There are some circumstances where a geolocation header field may
contain more than one location value. Knowing the identity of the
node adding the location value allows the recipient more freedom in
selecting the value to look at first rather than relying solely on
the order of the location values.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on November 30, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8.1. Registration of loc-src Parameter for geolocation header
field . . . . . . . . . . . . . . . . . . . . . . . . . . 6
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . 6
10.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
The SIP geolocation specification [RFC6442] describes the
"Geolocation" SIP header field which is used to indicate that the SIP
message is conveying location information. The specification
suggests that only one location value should be conveyed. However,
some communications architectures, such as 3GPP [TS23-167] and ETSI
[M493], prefer to use information provided by edge-proxies or
acquired through the use of core-network nodes, before using
information provided solely by user equipment (UE). These solutions
don't preclude the use of UE provided location but require a means of
being able to distinguish the identity of the node adding the
location value to the SIP message from that provided by the UE.
[RFC6442] stipulates that the order of location values in the
geolocation header field is the same as the order in which they were
added to the header field. Whilst this order provides guidance to
the recipient as to which values were added to the message earlier in
the communication chain, it does not provide any indication of which
node actually added the location value. Knowing the identity of the
entity that added the location to the message allows the recipient to
choose which location to consider first rather than relying solely on
the order of the location values in the geolocation header field.
This document adds a location-source (loc-src) parameter to the
location values in [RFC6442] so that the entity adding the location
value to geolocation header field can identify itself using its
hostname. How the entity adding the location value to the header
field obtains the location information is out of scope of this
document.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Rationale
The primary intent of the parameter defined in this specific is for
use in emergency calling. There are various architectures defined
for providing emergency calling using SIP-based messaging. Each has
it own characteristics with corresponding pros and cons. All of them
allow the UE to provide location information, however, many also
attach other sources of location information to support veracity
checks, provide backup information, or to be used as the primary
location.
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This document makes no attempt to comment on these various
architectures or the rationale for them wishing to include multiple
location values. It does recognize that these architectures exist
and that there is a need to identify the entity adding the location
information.
The parameter defined in this specification adds the location source
generating the location value to increase the trustworthiness of the
location information.
The loc-src parameter is applicable within a single private
administrative domain or between different administrative domains
where there is a trust relationship between the domains. Thus it is
intended to use this parameter only in trust domains where Spec(T) as
described in [RFC3325] exists.
The loc-src parameter is not included in a SIP message sent to
another network if there is no trust relationship. The The loc-src
parameter is not applicable if the administrative domain manages
emergency calls in a way that does not require location source
generating the location.
The functional architecture described within ETSI [M493] is an
example of architecture where this parameter makes sense to be used.
4. Mechanism
The mechanism employed adds a parameter to the location value defined
in [RFC6442] that identifies the hostname of the entity adding the
location value to the geolocation header field. The Augmented BNF
(ABNF) [RFC5234] for this parameter is shown in Figure 1.
location-source = "loc-src=" (hostname )
hostname = <defined in RFC3261>
Figure 1: Location Source
Only a fully qualified host name is valid, an IP address MUST NOT be
added by an entity conforming with this specification. If a node
conforming to this specification receives a geolocation header field
with a loc-src parameter containing an IP address then the parameter
MUST be removed.
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Any proxy adding a location value to a geolocation header field
SHOULD also add its host name using the loc-src parameter so that it
is clearly identified as the node adding the location. A UE MUST NOT
provide a loc-src parameter value. If a proxy receives a message
from an untrusted source with the loc-src parameter set then it MUST
remove the loc-src parameter before passing the message into a
trusted network.
5. Example
The following example shows a SIP INVITE message containing a
geolocation header field with two location values. The first
location value points to a PIDF-LO in the SIP body using a content-
indirection (cid:) URI per [RFC4483] and this is provided by the UE.
The second location value is an https URI the provided by a proxy
which identifies itself using the loc-src parameter.
INVITE sips:bob@biloxi.example.com SIP/2.0
Via: SIPS/2.0/TLS pc33.atlanta.example.com;branch=z9hG4bK74bf9
Max-Forwards: 70
To: Bob <sips:bob@biloxi.example.com>
From: Alice <sips:alice@atlanta.example.com>;tag=9fxced76sl
Call-ID: 3848276298220188511@atlanta.example.com
Geolocation: <cid:target123@atlanta.example.com>,
<https://lis.example.com:8222/y77syc7cuecbh>;
loc-src=edgeproxy.example.com
Geolocation-Routing: yes
Accept: application/sdp, application/pidf+xml
CSeq: 31862 INVITE
Contact: <sips:alice@atlanta.example.com>
Content-Type: multipart/mixed; boundary=boundary1
Content-Length: ...
Figure 2: Example Location Request.
6. Privacy Considerations
This document doesn't change any of the privacy considerations
described in [RFC6442]. While the addition of the loc-src parameter
does provide an indicator of the entity that added the location in
the signaling path this provides little more exposure than a proxy
identity being added to the record-route header field.
7. Security Considerations
This document introduces the ability of a proxy or middle box to
insert a host name indicating the that they added the specific
location value to the geolocation header field. The intent is for
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this field to be used by the location recipient in the event that the
SIP message contains multiple location values. As a consequence this
parameter should only be used by the location recipient in a trusted
network.
The use of this parameter is not restricted to a specific
architecture but using multiples locations and loc-src may end in
compatibility issues. [RFC6442] already addresses the issue of
multiples locations. To avoid problems of wrong interpretation of
loc-src the value may be discarded when passed to an other domain.
8. IANA Considerations
8.1. Registration of loc-src Parameter for geolocation header field
This document calls for IANA to register a new SIP header parameter
as per the guidelines in [RFC3261], which will be added to header
sub-registry under http://www.iana.org/assignments/sip-parameters.
Header Field: geolocation
Parameter Name: loc-src
9. Acknowledgements
The authors would like to thank Dale Worley for his extensive review
of the draft The authors would like to acknowledge the constructive
feedback provided by Paul Kyziva and Christer Holmberg.
10. References
10.1. 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,
<https://www.rfc-editor.org/info/rfc2119>.
[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,
<https://www.rfc-editor.org/info/rfc3261>.
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[RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private
Extensions to the Session Initiation Protocol (SIP) for
Asserted Identity within Trusted Networks", RFC 3325,
DOI 10.17487/RFC3325, November 2002,
<https://www.rfc-editor.org/info/rfc3325>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC6442] Polk, J., Rosen, B., and J. Peterson, "Location Conveyance
for the Session Initiation Protocol", RFC 6442,
DOI 10.17487/RFC6442, December 2011,
<https://www.rfc-editor.org/info/rfc6442>.
10.2. Informative References
[M493] European Telecommunications Standards Institute,
"Functional architecture to support European requirements
on emergency caller location determination and transport",
ES 203 178, V 1.1.1, Februar 2015.
[RFC4483] Burger, E., Ed., "A Mechanism for Content Indirection in
Session Initiation Protocol (SIP) Messages", RFC 4483,
DOI 10.17487/RFC4483, May 2006,
<https://www.rfc-editor.org/info/rfc4483>.
[TS23-167]
3rd Generation Partnership Project, "3rd Generation
Partnership Project; Technical Specification Group
Services and System Aspects; IP Multimedia Subsystem (IMS)
emergency sessions", TS 23.167, V 12.1.0, March 2015.
Authors' Addresses
James Winterbottom
Winterb Consulting Services
Gwynneville, NSW 2500
AU
Phone: +61 448 266004
Email: a.james.winterbottom@gmail.com
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Roland Jesske
Deutsche Telekom
Heinrich-Hertz Str, 3-7
Darmstadt 64295
Germany
Email: r.jesske@telekom.de
URI: www.telekom.de
Bruno Chatras
Orange Labs
38-40 rue du General Leclerc
Issy Moulineaux Cedex 9 F-92794
France
Email: bruno.chatras@orange.com
Andrew Hutton
Unify
Technology Drive
Nottingham NG9 1LA
UK
Email: andrew.hutton@unify.com
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