One document matched: draft-patel-ecrit-sos-parameter-03.txt

Differences from draft-patel-ecrit-sos-parameter-02.txt

ECRIT Working Group                                             M. Patel
Internet-Draft                                                    Nortel
Intended status: Standards Track                        January 22, 2009
Expires: July 26, 2009


 SOS Uniform Resource Identifier (URI) Parameter for Marking of Session
    Initiation Protocol (SIP) Requests related to Emergency Services
                 draft-patel-ecrit-sos-parameter-03.txt

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   Copyright (c) 2009 IETF Trust and the persons identified as the
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Abstract

   This document defines a new Session Initiation Protocol (SIP) Uniform



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   Resource Identifier (URI) parameter intended for marking SIP
   registration requests related to emergency services.  The usage of
   this new URI parameter complements the usage of the Service Uniform
   Resource Name (URN) and is not intended to replace it.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   4.  The "sos" URI Parameter . . . . . . . . . . . . . . . . . . . . 4
     4.1.  REGISTER Request  . . . . . . . . . . . . . . . . . . . . . 4
     4.2.  2xx Reponse to REGISTER Request . . . . . . . . . . . . . . 4
   5.  Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 6





























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1.  Introduction

   One way to differentiate a SIP-based emergency call from an ordinary
   call is by the presence of the Service URN as defined in RFC 5031
   [RFC5031] (and used in the IETF emergency services architecture
   described in PhoneBCP[I-D.ietf-ecrit-phonebcp]).  The 3GPP IP
   Multimedia Subsystem (IMS) emergency services architecture,
   illustrated in 3GPP TS 23.167 [3GPP.23.167], specifies that the User
   Equipment (UE) performs emergency registration prior to or during the
   initiation of an emergency call.  The circumstances where such an
   emergency registration is required are listed below:

   - the UE is not registered with its home network;

   - is currently registered but roaming (to ensure that the emergency
   call is handled in the visited network, as required by some
   jurisdictions).

   Emergency registration is possible only when the UE has sufficient
   credentials to register with its home network and can detect that an
   emergency session is initiated.  Unfortunately, marking of the
   emergency registration can not be fulfilled by the use of the Service
   URN.

   In some countries, it is a regulatory requirement that devices be
   able to place emegency calls in circumstances where other calls may
   not be permitted.  When a UE issues an emergency marked REGISTER
   request it informs the registrar that the contact address and the
   address-of-record being registered is to be used for emergency calls,
   and roaming and barring restrictions should not be applied for the
   registered address-of-record.  A call back from a PSAP would be
   routed to the registered contact address.

   This document proposes a way to mark a REGISTER message as an
   emergency registration.


2.  Terminology

   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 BCP
   14, RFC 2119 [RFC2119]


3.  Requirements

   Req: It shall be possible to distinguish emergency registration from



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   non-emergency registration by providing an appropriate indication in
   the SIP header fields.


4.  The "sos" URI Parameter

   This section provides an overview of the proposed new URI parameter
   to be used for marking REGISTER requests related to emergency
   services.

   A new URI parameter "sos" is defined in this document.  The "sos"
   parameter is appended to a URI consistent with RFC 3261 [RFC3261].
   It is proposed that use of this URI parameter is restricted to the
   Contact header included in the REGISTER request (and the 2xx response
   to the REGISTER request) related to an emergency call only.  The
   "sos" URI parameter MUST NOT be considered as a replacement for the
   Service URN for emergency calls originated by a UA.

4.1.  REGISTER Request

   When the UA sends a REGISTER request for emergency registration, the
   "sos" URI parameter MUST be appended to the URI in the Contact
   header.  This serves as an indication to the registrar that the
   request is for emergency registration.

   Example:

   Contact: "Alice" <sip:alice@example.com;sos> ;q=0.7; expires=3600

   In the event that more than one Contact header field is included in
   the REGISTER request, only the contact addresses that include the
   "sos" URI parameter shall be considered as emergency registered
   contact addresses.

4.2.  2xx Reponse to REGISTER Request

   The "sos" URI parameter MUST be present in the Contact header in the
   200 (OK) response sent by the registrar upon successful registration.
   The "sos" URI parameter is appended to the URI included in the
   Contact header, thus indicating to the UA that this contact address
   will be included in the Contact header of an INVITE for emergency
   call intiation.


5.  Formal Syntax

   The following syntax specification uses the augmented Backus-Naur
   Form (BNF) as described in RFC 2234 [RFC2234]



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   uri-parameter = *(";"value)

   value = sos


6.  IANA Considerations

   This specification defines one new SIP URI parameter, as per the
   registry created by RFC 3969 [RFC3969]

   Parameter Name: sos

   Predefined Values: none

   Reference: [RFCXXXX]

   [NOTE TO IANA: Please replace XXXX with the RFC number of this
   specification.]


7.  Security Considerations

   As an identifier, the "sos" parameter itself does not raise any
   particular security issues.  The semantic described by the "sos"
   parameter are meant to be well-known so privacy considerations do not
   apply to the URN.  The main possibility of attack involves use of the
   "sos" parameter to bypass the normal procedures in order to achieve
   fraudulent use of services or to bypass security procedures.  The
   usage of this parameter as described in this document is purely for
   the purpose of the REGISTER message and hence in presence of user
   authentication it is ensured that the respective user can be held
   accountable.

   It is RECOMMENDED to log events of misuse of the "sos" URI parameter,
   for example by including it in a request or response not related to
   an emergency calls.


8.  Acknowledgements

   The author would like to thank Keith Drage, Milo Orsic, Deb Barclay,
   John-Luc Bakker, Andrew Allen, Hiroshi Ishikawa, Sean Schneyer, Peter
   Leis, Georg Mayer, Marvin Bienn, Ricky Kaura, Steve Norreys, Laura
   Liess, AC Mahendran, Roozbeh Atarius, Ramachandran Subramanian and
   Sandeep Sharma, Brian Rosen, Hannes Tschofenig, Christer Holmberg and
   Henning Schulzrinne for the discussions and contributions that lead
   to this work.




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9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.

   [RFC2234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 2234, November 1997.

   [RFC3969]  Camarillo, G., "The Internet Assigned Number Authority
              (IANA) Uniform Resource Identifier (URI) Parameter
              Registry for the Session Initiation Protocol (SIP)",
              BCP 99, RFC 3969, December 2004.

9.2.  Informative References

   [I-D.ietf-ecrit-phonebcp]
              Rosen, B. and J. Polk, "Best Current Practice for
              Communications Services in support of Emergency  Calling",
              draft-ietf-ecrit-phonebcp-06 (work in progress),
              November 2008.

   [RFC5031]  Schulzrinne, H., "A Uniform Resource Name (URN) for
              Emergency and Other Well-Known Services", RFC 5031,
              January 2008.

   [3GPP.23.167]
              3GPP, "IP Multimedia Subsystem (IMS) emergency sessions",
              3GPP TS 23.167 7.11.0, December 2008.


Author's Address

   Milan Patel
   Nortel
   Maidenhead Office Park, Westacott Way
   Maidenhead, Berkshire, UK

   Email: milanpa@nortel.com






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