B.2 On-network timers

24.3793GPPMission Critical Push To Talk (MCPTT) call controlProtocol specificationRelease 18TS

B.2.1 Timers in the controlling MCPTT function

The table B.2.1-1 provides a description of the timers used by the controlling MCPTT function, specifies the timer values, describes the reason for starting of the timer, normal stop and the action on expiry.

Table B.2.1-1: controlling MCPTT function timers

Timer

Timer value

Cause of start

Normal stop

On expiry

TNG1 (acknowledged call setup timer)

(NOTE 1)

Obtained from the group document in the <on-network-timeout-for-acknowledgement-of-required-members> element as specified in 3GPP TS 24.481 [31].

On reception of a SIP INVITE request to start a group session where the group document contains <on-network-required> group members as specified in 3GPP TS 24.481 [31].

On receipt of all SIP 200 (OK) responses to all SIP INVITE requests for <on-network-required> group members as specified in 3GPP TS 24.481 [31].

Either proceed with the set-up of the call or abandon the call.

TNG2

(in-progress emergency group call timer)

(NOTE 2)

Obtained from the <group-time-limit> element of the <emergency-call> element of the <on-network> element of the service configuration document as specified in 3GPP TS 24.484 [50].

On reception of a SIP INVITE request or SIP re-INVITE request that initiates an MCPTT emergency group call.

On acceptance of a request to cancel the in-progress emergency state of a group.

Cancels the in-progress emergency state of the group and return the session and/or call to normal priority level.

TNG3 (group call timer).

(NOTE 1).

Set to the value of the <on-network-maximum-duration> element from the group document.

On reception of a SIP INVITE request to start a group session after retrieval of the group document from the group management server.

For a temporary group call, when merging active group calls into a temporary group call.

When splitting a temporary group all into independent active calls

When the last MCPTT client has left the session.

When a temporary group call is split into independent active calls.

For active group calls, when merging them into a temporary group call.

Release the group call.

NOTE 1: More than one instance of this timer can be running in the controlling MCPTT function, each instance associated with a specific group call.

NOTE 2: More than one instance of this timer can be running in the controlling MCPTT function, each instance associated with a specific in-progress emergency state of a single group

B.2.2 Timers in the terminating participating MCPTT function

The table B.2.2-1 provides a description of the timers used by the terminating participating MCPTT function, specifies the timer values, describes the reason for starting of the timer, normal stop and the action on expiry.

Table B.2.2-1: controlling MCPTT function timers

Timer

Timer value

Cause of start

Normal stop

On expiry

TNP1 (call forwarding no answer timer)

(NOTE 1)

Obtained from the user profile document in the <call-forwarding-no-answer-timeout> element as specified in 3GPP TS 24.484 [50]. If the <call-forwarding-no-answer-timeout> element does not exist in the user profile document, the terminating participating MCPTT function shall use a default value of 20 seconds for the timer TNP1.

On reception of a SIP INVITE request to start a private call with the terminating MCPTT user having private call forwarding turned on with the <call-forwarding-condition> "NoAnswer" as specified in 3GPP TS 24.484 [50].

On receipt of a SIP 200 (OK) response to the SIP INVITE request for the private call to an MCPTT user having private call forwarding turned on with the <call-forwarding-condition> "NoAnswer" as specified in 3GPP TS 24.484 [50].

Retrieve new target from the <call-forwarding-target> element as specified in 3GPP TS 24.484 [50], and proceed according to 6.3.2.5

NOTE 1: More than one instance of this timer can be running in the controlling MCPTT function, each instance is associated with a specific private call.