IANA Registration of New Session Initiation Protocol (SIP) Resource-Priority Namespace for Mission Critical Push To Talk service

The third generation partnership project (3GPP) has defined a Mission Critical Push To Talk (MCPTT) over LTE service . The MCPTT service supports an enhanced PTT service, suitable for mission critical scenarios, based upon 3GPP Evolved Packet System (EPS) services. The requirements for the MCPTT service defined within 3GPP can also form the basis for a non-mission critical Push To Talk (PTT) service. 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 Push To Talk service to e.g., public safety, transport companies, utilities or 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 which 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. These priorities take into account among other things 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 . 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 in . 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 . High priority calls when there is danger of life, for either the public safety worker or any other human, need to be set up immediately and thus require preemption. Other calls may be less sensitive in call set-up time but have a high priority once established. For these calls a queueing mechanism is more appropriate. MCPTT data transfer currently under development can benefit from a queueing mechanism. This document creates additional Session Initiation Protocol (SIP) Resource-Priority namespaces to meet the requirements of the 3GPP defined Mission Critical Push To Talk, and places these namespaces in the IANA registry.

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 network is undefined.

This document introduces the MCPTT namespaces mcpttp and mcpttq, the name coming from the 3GPP defined Mission Critical Push To Talk service.

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.5 mcpttp.6 mcpttp.7 mcpttp.8 mcpttp.9 mcpttp.10 mcpttp.11 mcpttp.12 mcpttp.13 mcpttp.14 mcpttp.15 (highest priority) 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.8 mcpttq.9 mcpttq.10 mcpttq.11 mcpttq.12 mcpttq.13 mcpttq.14 mcpttq.15 (highest priority) Intended algorithm for mcpttq is queuing. New Warning code: No. New SIP response code: No.

This document has the same Security Considerations as .

Abiding by the rules established within and , this is an Informative RFC registering two new namespaces, their associated priority-values, and intended algorithms.

The authors would like to thank Bob Fredericks, Baruh Hason, Mary Barnes and Keith Drage for comments and discussions.

[RFC EDITOR NOTE: Please remove this section when publishing] Changes from draft-holmberg-dispatch-mcptt-rp-namespace-01. - Removal of Conventions section. - Editorial changes. Changes from draft-holmberg-dispatch-mcptt-rp-namespace-00. - The two namespaces have been spelt out explicitly. - The numbering of priority levels is changed from 1-16 to 0-15. - Address of one author has changed.