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Internet Engineering Task Force (IETF)                       C. HolmbergRequest for Comments: 8101                                      J. AxellCategory: Informational                                         EricssonISSN: 2070-1721                                               March 2017IANA Registration of New Session Initiation Protocol (SIP)Resource-Priority Namespace for Mission Critical Push To Talk ServiceAbstract   This document creates additional Session Initiation Protocol (SIP)   Resource-Priority namespaces to meet the requirements of the   3GPP-defined Mission Critical Push To Talk (MCPTT) and places these   namespaces in the corresponding IANA registry.Status of This Memo   This document is not an Internet Standards Track specification; it is   published for informational purposes.   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).  Not all documents   approved by the IESG are a candidate for any level of Internet   Standard; seeSection 2 of RFC 7841.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc8101.Copyright Notice   Copyright (c) 2017 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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.Holmberg & Axell              Informational                     [Page 1]

RFC 8101                   MCPTT R-P Namespace                March 2017Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .22.  Applicability . . . . . . . . . . . . . . . . . . . . . . . .33.  New SIP Resource-Priority Namespaces Created  . . . . . . . .33.1.  Introduction  . . . . . . . . . . . . . . . . . . . . . .33.2.  The MCPTT Namespaces  . . . . . . . . . . . . . . . . . .34.  Security Considerations . . . . . . . . . . . . . . . . . . .55.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .56.  Normative References  . . . . . . . . . . . . . . . . . . . .5   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .6   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .61.  Introduction   The Third Generation Partnership Project (3GPP) has defined a Mission   Critical Push To Talk (MCPTT) over LTE service [TS.3GPP.22.179].  The   MCPTT service supports an enhanced Push To Talk (PTT) service that is   suitable for mission critical scenarios and is based upon 3GPP   Evolved Packet System (EPS) services.  The requirements for the MCPTT   service defined within 3GPP can also form the basis for other PTT   services.   The MCPTT service is intended to support communication between   several users (a group call), where each user can gain permission to   talk in an arbitrated manner.  However, the MCPTT service also   supports private calls between pairs of users.   MCPTT is primarily targeted to provide a professional PTT service to,   e.g., public safety, transport companies, utilities, and industrial   and nuclear plants.  In addition to this, a commercial PTT service   for non-professional use (e.g., groups of people on holiday) may be   delivered through an MCPTT system.  Based on their operational model,   the performance and MCPTT features in use vary per user organization,   where functionality that is more mission-critical-specific (e.g.,   Imminent Peril Call) might not be available to commercial customers.   The MCPTT service provides its users with different priorities for   the access to network resources in order to provide means to   prioritize between calls when resources are scarce.  Among other   things, these priorities take into account the priority and role of   the caller, the priority and type of the group, and the situation in   which the call is made.   The SIP-level call control procedures using these namespaces are   specified in [TS.3GPP.24.379].  The namespaces defined here will   support a wide range of queuing options.  The namespaces correspond   to what can be supported over the 3GPP Rx interface, defined inHolmberg & Axell              Informational                     [Page 2]

RFC 8101                   MCPTT R-P Namespace                March 2017   [TS.3GPP.29.214].  The usage of the namespaces can be tailored to the   needs of the operator.  The mechanism to do this is to configure   which values a specific user is allowed to use.  This configuration   is specified in [TS.3GPP.24.384].   High-priority calls (when the life of either a public safety worker   or anyone else is in danger) need to be set up immediately; thus,   they require preemption.  Other calls may be less sensitive in call   setup time but have a high priority once established.  For these   calls, a queueing mechanism is more appropriate.  The MCPTT data   transfer service currently under development can benefit from a   queueing mechanism.  Another example is video-only calls that are not   critical in call setup time but where keeping the call is important.   This document creates additional SIP Resource-Priority namespaces to   meet the requirements of the 3GPP-defined MCPTT and places these   namespaces in the IANA registry.2.  Applicability   This document defines namespaces applicable for MCPTT services   defined by 3GPP that use the network services of a 3GPP-defined LTE   network.  The use of this namespace outside such networks is   undefined.3.  New SIP Resource-Priority Namespaces Created3.1.  Introduction   This document introduces the following MCPTT namespaces: mcpttp and   mcpttq.  The names of which come from the 3GPP-defined MCPTT service.3.2.  The MCPTT Namespaces   The mcpttp namespace uses the priority levels listed below from   lowest to highest priority.      mcpttp.0 (lowest priority)      mcpttp.1      mcpttp.2      mcpttp.3      mcpttp.4      mcpttp.5Holmberg & Axell              Informational                     [Page 3]

RFC 8101                   MCPTT R-P Namespace                March 2017      mcpttp.6      mcpttp.7      mcpttp.8      mcpttp.9      mcpttp.10      mcpttp.11      mcpttp.12      mcpttp.13      mcpttp.14      mcpttp.15 (highest priority)   The Namespace Numerical Value is 46.   Intended algorithm for mcpttp is preemption.   New Warning code: No.   New SIP response code: No.   The mcpttq namespace uses the priority levels listed below from   lowest to highest priority.      mcpttq.0 (lowest priority)      mcpttq.1      mcpttq.2      mcpttq.3      mcpttq.4      mcpttq.5      mcpttq.6      mcpttq.7      mcpttq.8Holmberg & Axell              Informational                     [Page 4]

RFC 8101                   MCPTT R-P Namespace                March 2017      mcpttq.9      mcpttq.10      mcpttq.11      mcpttq.12      mcpttq.13      mcpttq.14      mcpttq.15 (highest priority)   The Namespace Numerical Value is 47.   Intended algorithm for mcpttq is queuing.   New Warning code: No.   New SIP response code: No.4.  Security Considerations   This document does not have any impact on the security of the SIP   MCPTT protocol.  Its purpose is purely administrative in nature.5.  IANA Considerations   Abiding by the rules established within [RFC4412] and [RFC7134], this   is an Informational RFC creating two new namespaces, their associated   priority-values, and intended algorithms.6.  Normative References   [RFC4412]  Schulzrinne, H. and J. Polk, "Communications Resource              Priority for the Session Initiation Protocol (SIP)",RFC 4412, DOI 10.17487/RFC4412, February 2006,              <http://www.rfc-editor.org/info/rfc4412>.   [RFC7134]  Rosen, B., "The Management Policy of the Resource Priority              Header (RPH) Registry Changed to "IETF Review"",RFC 7134,              DOI 10.17487/RFC7134, March 2014,              <http://www.rfc-editor.org/info/rfc7134>.Holmberg & Axell              Informational                     [Page 5]

RFC 8101                   MCPTT R-P Namespace                March 2017   [TS.3GPP.22.179]              3GPP, "3rd Generation Partnership Project; Technical              Specification Group Services and System Aspects; Mission              Critical Push To Talk (MCPTT) over LTE; Stage 1", 3GPP              TS 22.179 13.3.0, December 2015.   [TS.3GPP.29.214]              3GPP, "3rd Generation Partnership Project; Technical              Specification Group Core Network and Terminals; Policy and              Charging Control over Rx reference point;", 3GPP TS 29.214              13.7.0, September 2016.   [TS.3GPP.24.379]              3GPP, "3rd Generation Partnership Project; Technical              Specification Group Core Network and Terminals; Mission              Critical Push To Talk (MCPTT) call control; Protocol              specification;", 3GPP TS 24.379 13.2.0, September 2016.   [TS.3GPP.24.384]              3GPP, "3rd Generation Partnership Project; Technical              Specification Group Core Network and Terminals; Mission              Critical Push To Talk (MCPTT) configuration management;              Protocol specification", 3GPP TS 24.384 13.2.0, September              2016.Acknowledgments   The authors would like to thank Bob Fredericks, Baruh Hason, Mary   Barnes, and Keith Drage for comments and discussions.Authors' Addresses   Christer Holmberg   Ericsson   Hirsalantie 11   Jorvas  02420   Finland   Email: christer.holmberg@ericsson.com   Joergen Axell   Ericsson   Groenlandsgatan 31   Stockholm  16480   Sweden   Email: jorgen.axell@ericsson.comHolmberg & Axell              Informational                     [Page 6]