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Network Working Group                                       G. CamarilloRequest for Comments: 5002                                     G. BlancoCategory: Informational                                         Ericsson                                                             August 2007The Session Initiation Protocol (SIP)P-Profile-Key Private Header (P-Header)Status of This Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Abstract   This document specifies the SIP P-Profile-Key P-header.  This header   field is used in the 3rd-Generation Partnership Project (3GPP) IMS   (IP Multimedia Subsystem) to provide SIP registrars and SIP proxy   servers with the key of the profile corresponding to the destination   SIP URI of a particular SIP request.Table of Contents1. Introduction ....................................................22. Terminology .....................................................23. Scenario ........................................................24. Requirements ....................................................35. P-Profile-Key Header Field Definition ...........................36. Applicability ...................................................47. IANA Considerations .............................................48. Security Considerations .........................................59. Acknowledgements ................................................510. References .....................................................510.1. Normative References ......................................510.2. Informative References ....................................6Author*                      Informational                      [Page 1]

RFC 5002                 P-Profile-Key P-Header              August 20071.  Introduction   The 3rd-Generation Partnership Project (3GPP) IMS (IP Multimedia   Subsystem) uses SIP [RFC3261] as its main signalling protocol.  (For   more information on the IMS, a detailed description can be found in   3GPP TS 23.228 [3GPP.23.228] and 3GPP TS 24.229 [3GPP.24.229]).  3GPP   has identified a set of requirements that can be met, according to   the procedures in [RFC3427], by defining a new SIP P-header.   The remainder of this document is organized as follows.Section 3   describes the scenario considered by 3GPP andSection 4 discusses the   requirements derived from this scenario.Section 5 defines the P-   Profile-Key header field, which meets those requirements, andSection6 discusses the applicability and scope of this new header field.Section 7 registers the P-Profile-Key header field with the IANA andSection 8 discusses the security properties of the environment where   this header field is intended to be used.2.  Terminology   HSS:     Home Subscriber Server.   I-CSCF:  Interrogating - Call/Session Control Function.   Public Service Identity:            A SIP URI that refers to a service instead of a user.   S-CSCF:  Serving - Call/Session Control Function.   Wildcarded Public Service Identity:            A set of Public Service Identities that match a regular            expression and share the same profile.3.  Scenario   In the 3GPP IMS, there are scenarios where a set of proxies handling   a request need to consult the same user database, as described in   [RFC4457].  Those proxies typically use the destination SIP URI of   the request as the key for their database queries.  Nevertheless,   when a proxy handles a Wildcarded Public Service Identity, the key to   be used in its database query is not the destination SIP URI of the   request, but a regular expression instead.   Public Service Identities are SIP URIs that refer to services instead   of users.  That is, they address a specific application in an   Application Server.  Wildcarded Public Service Identities are a set   of Public Service Identities that match a regular expression and   share the same profile.  For example, the Public Service IdentitiesAuthor*                      Informational                      [Page 2]

RFC 5002                 P-Profile-Key P-Header              August 2007   'sip:chatroom-12@example.com' and 'sip:chatroom-657@example.com'   would match the Wildcarded Public Service Identity   'sip:chatroom-!.*!@example.com'.  For a description of Wildcarded   Public Service Identities, see 3GPP TS 23.003 [3GPP.23.003].   When a proxy queries the user database for a Public Service Identity   for which there is no profile in the user database, the user database   needs to find its matching Wildcarded Public Service Identity.  For   example, if the user database receives a query for   'sip:chatroom-657@example.com', the user database needs to go through   all the Wildcarded Public Service Identity it has until it finds a   matching one; in this case, 'sip:chatroom-!.*!@example.com'.  The   process to find a matching Wildcarded Public Service Identity can be   computationally expensive, time consuming, or both.   When two proxies query the user database for the same Public Service   Identity, which matches a Wildcarded Public Service Identity, the   user database needs to perform the matching process twice.  Having to   perform that process twice can be avoided by having the first proxy   obtain the Wildcarded Public Service Identity from the user database   and transfer it, piggy-backed in the SIP message, to the second   proxy.  This way, the second proxy can query the user database using   the Wildcarded Public Service Identity directly.   An alternative, but undesirable, solution would consist of having the   user database store every Public Service Identity and its matching   Wildcarded Public Service Identity.  The scalability and   manageability properties of this approach are considerably worse than   those of the approach described earlier.4.  Requirements   This section lists the requirements derived from the previous   scenario:   1.  It is necessary to optimize the response time for session       establishment in the 3GPP IMS.   2.  It is necessary to keep the user database's size and maintenance       manageable (e.g., storing individual Public Service Identities       matching a Wildcarded Public Service Identity in the user       database is not believed to be an acceptable solution).5.  P-Profile-Key Header Field Definition   This document defines the SIP P-Profile-Key P-header.  The P-   Profile-Key P-header contains the key to be used by a proxy to query   the user database for a given profile.Author*                      Informational                      [Page 3]

RFC 5002                 P-Profile-Key P-Header              August 2007   The augmented Backus-Naur Form (BNF) [RFC4234] syntax of the   P-Profile-Key header field is the following:      P-Profile-Key     = "P-Profile-Key" HCOLON (name-addr / addr-spec)                           *( SEMI generic-param )   The format of HCOLON, name-addr, addr-spec, and generic-param are   defined in [RFC3261].  The format of Wildcarded Public Service   Identities is defined in 3GPP TS 23.003 [3GPP.23.003].  They take the   form of Extended Regular Expressions (ERE) as defined in Chapter 9 of   IEEE 1003.1-2004 Part 1 [IEEE.1003.1-2004].   The following is an example of a P-Profile-Key header field that   contains a Wildcarded Public Service Identity:      P-Profile-Key: <sip:chatroom-!.*!@example.com>6.  Applicability   According to [RFC3427], P-headers have a limited applicability.   Specifications of P-headers such as this RFC need to clearly document   the useful scope of the proposal, and explain its limitations and why   it is not suitable for the general use of SIP on the Internet.   The P-Profile-Key header field is intended to be used in 3GPP IMS   networks.  This header field carries the key of a service profile,   that is stored in a user database referred to as HSS, between two   proxies, which are referred to as I-CSCF and S-CSCF.  The I-CSCF and   the S-CSCF belong to the same administrative domain and share a   common frame of reference to the user database.  The I-CSCF inserts   the P-Profile-Key header field into a SIP request and the S-CSCF   removes it before routing the request further.  (For a description of   how an I-CSCF and an S-CSCF query the same user database for a single   request, see [RFC4457].)   Typically, when SIP is used on the Internet, there are not multiple   proxies with a trust relationship between them querying the same user   database.  Consequently, the P-Profile-Key header field does not seem   useful in a general Internet environment.7.  IANA Considerations   This document defines a new SIP header field: P-Profile-Key.  This   header field has been registered by the IANA in the SIP Parameters   registry under the Header Fields subregistry.Author*                      Informational                      [Page 4]

RFC 5002                 P-Profile-Key P-Header              August 20078.  Security Considerations   The P-Profile-Key defined in this document is to be used in an   environment where elements are trusted and where attackers are not   supposed to have access to the protocol messages between those   elements.  Traffic protection between network elements is sometimes   achieved by using IPsec and sometimes by physically protecting the   network.  In any case, the environment where the P-Profile-Key header   field will be used ensures the integrity and the confidentiality of   the contents of this header field.  The P-Profile-Key header field   MUST NOT be used in environments that do not have these   characteristics.   The P-Profile-Key header field needs to be integrity protected to   keep attackers from modifying its contents.  An attacker able to   modify the contents of this header field could make the network apply   a different service than the one corresponding to the request   carrying the P-Profile-Key header field.   The contents of the P-Profile-Key field need to be kept confidential.   An attacker able to access the contents of this header field would   obtain certain knowledge about the way services are structured in a   given domain.9.  Acknowledgements   Alf Heidermark and Timo Forsman provided input to this document.   Miguel Angel Garcia-Martin performed an expert review on this   document on behalf of the SIPPING working group.  Jon Peterson   provided comments on this document.10.  References10.1.  Normative References   [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.   [RFC3427]           Mankin, A., Bradner, S., Mahy, R., Willis, D.,                       Ott, J., and B. Rosen, "Change Process for the                       Session Initiation Protocol (SIP)",BCP 67,RFC3427, December 2002.   [RFC4234]           Crocker, D. and P. Overell, "Augmented BNF for                       Syntax Specifications: ABNF",RFC 4234, October                       2005.Author*                      Informational                      [Page 5]

RFC 5002                 P-Profile-Key P-Header              August 2007   [3GPP.23.003]       3GPP, "Numbering, addressing and identification",                       3GPP TS 23.003 3.15.0, October 2006.   [IEEE.1003.1-2004]  "Standard for information technology - portable                       operating system interface (POSIX).  Base                       definitions", IEEE  1003.1-2004, 2004.10.2.  Informative References   [RFC4457]           Camarillo, G. and G. Blanco, "The Session                       Initiation Protocol (SIP) P-User-Database                       Private-Header (P-Header)",RFC 4457, April 2006.   [3GPP.23.228]       3GPP, "IP Multimedia Subsystem (IMS); Stage 2",                       3GPP TS 23.228 5.15.0, June 2006.   [3GPP.24.229]       3GPP, "Internet Protocol (IP) multimedia call                       control protocol based on Session Initiation                       Protocol (SIP) and Session Description Protocol                       (SDP); Stage 3", 3GPP TS 24.229 5.18.0, October                       2006.Authors' Addresses   Gonzalo Camarillo   Ericsson   Hirsalantie 11   Jorvas  02420   Finland   EMail: Gonzalo.Camarillo@ericsson.com   German Blanco   Ericsson   Via de los Poblados 13   Madrid  28033   Spain   EMail: German.Blanco@ericsson.comAuthor*                      Informational                      [Page 6]

RFC 5002                 P-Profile-Key P-Header              August 2007Full Copyright Statement   Copyright (C) The IETF Trust (2007).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Author*                      Informational                      [Page 7]