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LTE > Protocols > NAS > Timers and Constants

LTE NAS Timers

LTE NAS timers shape how EPS procedures behave after attach, during tracking area update, while restoring service, and when the network applies backoff or congestion control. This page is a direct reference for the LTE NAS timers most often checked in traces, including T3346, T3402, T3412, T3430, T3442, T3448, T3450, T3482, and T3485.

If you are reading LTE NAS message logs, start with the active procedure first, then check which timer is controlling the next UE action. A returned timer can explain why the UE waits before re-attaching, delays a service retry, performs periodic TAU, or stays quiet after a reject. That makes timers such as T3442, T3346, T3448, T3412, and T3430 some of the most useful LTE NAS fields to check in troubleshooting.

Quick facts

Technology LTE / EPS
Protocol scope EPS NAS timers, retry handling, and returned timer values
Main spec 3GPP TS 24.301
Most-linked timers T3346, T3402, T3412, T3442, T3448, T3450, T3470, T3482, and T3485
Main use Attach, service request, TAU, backoff handling, and UE retry timing

Quick lookup

Timer Main procedure context What it changes in practice Typical message pages
T3346 NAS congestion and access backoff Returned by the network to tell the UE to wait before retrying NAS behavior affected by congestion or overload control. Most visible in Attach Reject and Service Reject.
T3402 Attach retry backoff Controls how long the UE should wait before trying a new attach after a reject path that carries attach retry delay. Most visible in Attach Request, Attach Reject, and reject-driven recovery analysis.
T3411 Retry delay after attach or update failure Short retry wait used before the UE restarts certain mobility procedures after failure handling. Seen in mobility retry logic around attach and tracking area update.
T3412 Periodic tracking area update Defines when the UE should perform periodic TAU to refresh EPS registration presence. Most visible in Attach Accept and Tracking Area Update Request.
T3421 UE detach request supervision Starts when the UE sends Detach Request in a UE-initiated detach and supervises the wait for Detach Accept when normal completion applies. Most visible in LTE Detach Request and the later Detach Accept branch.
T3422 Network detach request supervision Supervises the network-side wait for Detach Accept after the MME sends network-initiated Detach Request. Most visible in network-initiated LTE Detach Request handling.
T3417 Service request retransmission control Supervises the service request attempt window in the standard service restoration path. Most visible in Service Request and Service Accept.
T3417ext Extended service request supervision Extends the supervision window for service restoration in variants where the longer handling path applies. Most visible in Service Request traces with extended restore handling.
T3460 Authentication and security message retransmission supervision Supervises network retransmission and waiting behavior during common NAS authentication and later security continuation branches. Most visible in Authentication Request, Authentication Response, and later NAS security continuation analysis.
T3470 Identity response supervision Supervises network-side waiting and retransmission behavior after Identity Request while the MME waits for Identity Response. Most visible in Identity Request and the following identification continuation.
T3482 PDN connectivity request supervision Starts when the UE sends PDN Connectivity Request as a standalone ESM procedure and supervises the wait for accept or reject handling. Most visible in PDN Connectivity Request and later default-bearer establishment analysis.
T3480 Bearer resource allocation or modification request supervision Supervises the UE-originated bearer resource allocation and bearer resource modification procedures while the UE waits for network outcome. Most visible in Bearer Resource Allocation Request and Bearer Resource Modification Request.
T3485 EPS bearer activation supervision Supervises network retransmission and waiting behavior after default or dedicated EPS bearer activation request messages while the network waits for the UE accept or reject message. Most visible in Activate Default EPS Bearer Context Request, Activate Dedicated EPS Bearer Context Request, and the following bearer activation completion branches.
T3489 ESM information request supervision Supervises network retransmission and waiting behavior after ESM Information Request while the network waits for ESM Information Response. Most visible in ESM Information Request and ESM Information Response.
T3492 PDN disconnect request supervision Supervises the UE-originated PDN disconnect procedure while the network decides whether to continue with bearer release or reject handling. Most visible in PDN Disconnect Request and the following bearer-release or reject branch.
T3447 NAS transport restriction after attach without PDN connection Restricts when the UE may send Uplink NAS Transport in EMM-CONNECTED mode after attaching without PDN connection, unless one of the allowed exceptions applies. Most visible in Uplink NAS Transport analysis, especially after attach without PDN connection.
T3495 EPS bearer deactivation supervision Supervises network retransmission and waiting behavior after Deactivate EPS Bearer Context Request while the network waits for the UE deactivation accept message. Most visible in Deactivate EPS Bearer Context Request and the following deactivation completion branch.
T3450 Attach and TAU accept supervision and retransmission control Supervises the network-side wait for Attach Complete or Tracking Area Update Complete after the corresponding accept message and controls retransmission behavior while the accepted mobility procedure is being finalized. Most visible in Attach Accept, Attach Complete, Tracking Area Update Accept, and Tracking Area Update Complete.
T3430 Tracking area update supervision Starts when the UE sends Tracking Area Update Request and supervises the TAU response path. Most visible in Tracking Area Update Request and later TAU accept or reject analysis.
T3442 CS service temporary unavailability wait Tells the UE to wait before retrying when CS service is temporarily unavailable in service-related reject handling. Most visible in Service Reject.
T3448 Control-plane user-data related wait or continuity handling Returned when control-plane user-data congestion or continuity handling needs timing guidance. Most visible in Service Accept, Service Reject, and some TAU contexts.

Overview

LTE NAS timers serve different roles. Some run after the UE sends a NAS message and supervise whether the procedure completes. Others are returned by the network and tell the UE when it may retry or when it should perform a periodic update. So the easiest way to read them is by procedure first: attach, tracking area update, service request, or retry backoff.

This page groups the timers by how they usually appear in live traces. It also points out the constant-style values carried inside NAS messages, because those returned timer values often explain why the UE waits, retries later, or stays silent after a reject.

Backoff and retry

These timers decide whether the UE retries immediately, waits for a backoff window, or delays the next mobility attempt after failure or congestion.

T3346

3GPP Specification: Release 10

Main procedure context: NAS congestion and access backoff

Returned by the network to tell the UE to wait before retrying NAS behavior affected by congestion or overload control.

Typical message pages: LTE Attach Reject , LTE Service Reject

Accepted values:

  • Signaled as GPRS timer 2 in LTE NAS messages.
  • Accepted unit encodings are 2 seconds, 1 minute, or decihours.
  • The timer may also be set to deactivated.
  • If another unit code appears, this protocol version interprets it as multiples of 1 minute.

T3402

3GPP Specification: Release 8

Main procedure context: Attach retry backoff

Controls how long the UE should wait before trying a new attach after a reject path that carries attach retry delay.

Typical message pages: LTE Attach Request , LTE Attach Reject

Accepted values:

  • Signaled as GPRS timer in LTE NAS messages.
  • Accepted unit encodings are 2 seconds, 1 minute, or decihours.
  • The timer may also be set to deactivated.
  • If another unit code appears, this protocol version interprets it as multiples of 1 minute.

T3411

3GPP Specification: Release 8

Main procedure context: Retry delay after attach or update failure

Short retry wait used before the UE restarts certain mobility procedures after failure handling.

Typical message pages: LTE Attach Request , LTE Tracking Area Update Request

Accepted values:

  • This is a procedure timer, not a carried timer IE in the LTE NAS messages on this page.
  • There is no signaled on-the-wire value to decode from the message body.
  • In traces, the effective value is inferred from UE behavior and the procedure timing defined by the implementation and spec handling.

Mobility and registration

These timers shape periodic presence refresh and supervision around attach or tracking area update behavior.

T3412

3GPP Specification: Release 8

Main procedure context: Periodic tracking area update

Defines when the UE should perform periodic TAU to refresh EPS registration presence.

Typical message pages: LTE Attach Accept , LTE Tracking Area Update Request

Accepted values:

  • Standard T3412 value is signaled as GPRS timer.
  • Accepted standard-unit encodings are 2 seconds, 1 minute, or decihours.
  • The standard timer may also be set to deactivated.
  • T3412 extended value uses GPRS timer 3, with accepted units of 10 minutes, 1 hour, 10 hours, 2 seconds, 30 seconds, or 1 minute, plus deactivated.

T3421

3GPP Specification: Release 8

Main procedure context: UE detach request supervision

Starts when the UE sends Detach Request in a UE-initiated detach and supervises the wait for Detach Accept when normal completion applies.

Typical message pages: LTE Detach Request , LTE Detach Accept

Accepted values:

  • This is a procedure timer, not a returned timer IE carried inside the LTE NAS message body.
  • There is no encoded on-the-wire timer value to decode directly from Detach Request.
  • In traces, use it to interpret how long the UE waits for Detach Accept in non-switch-off detach handling.

T3422

3GPP Specification: Release 8

Main procedure context: Network detach request supervision

Supervises the network-side wait for Detach Accept after the MME sends network-initiated Detach Request.

Typical message pages: LTE Detach Request , LTE Detach Accept

Accepted values:

  • This is a procedure timer, not a returned timer IE carried inside the LTE NAS message body.
  • There is no encoded on-the-wire timer value to decode directly from the network-initiated Detach Request.
  • In traces, use it to interpret retransmission and waiting behavior while the network expects Detach Accept from the UE.

T3450

3GPP Specification: Release 8

Main procedure context: Attach and TAU accept supervision and retransmission control

Supervises the network-side wait for Attach Complete or Tracking Area Update Complete after the corresponding accept message and controls retransmission behavior while the accepted mobility procedure is being finalized.

Typical message pages: LTE Attach Accept , LTE Attach Complete , LTE Tracking Area Update Accept , LTE Tracking Area Update Complete

Accepted values:

  • This is a procedure timer, not a returned timer IE carried inside the LTE NAS message body.
  • There is no encoded on-the-wire value to decode from Attach Accept, Attach Complete, Tracking Area Update Accept, or Tracking Area Update Complete.
  • In traces, use it to interpret retransmitted accept messages and the waiting window before the network gives up on the expected completion message.

T3430

3GPP Specification: Release 8

Main procedure context: Tracking area update supervision

Starts when the UE sends Tracking Area Update Request and supervises the TAU response path.

Typical message pages: LTE Tracking Area Update Request

Accepted values:

  • This timer is supervised by the procedure rather than delivered as a timer IE in the NAS message payload.
  • There is no direct encoded value field to decode from the TAU Request itself.
  • In traces, read it as a local supervision timer tied to the response window after the UE sends TAU Request.

Authentication and security

These timers are most useful when reading NAS authentication challenge handling, response supervision, and later security continuation.

T3460

3GPP Specification: Release 8

Main procedure context: Authentication and security message retransmission supervision

Supervises network retransmission and waiting behavior during common NAS authentication and later security continuation branches.

Typical message pages: LTE Authentication Request , LTE Authentication Response

Accepted values:

  • This is a procedure timer, not a returned timer IE carried inside the LTE NAS message body.
  • There is no encoded value field to decode directly from Authentication Request or Authentication Response.
  • In traces, read it as the supervision timer around common NAS authentication and related retransmission behavior.

T3470

3GPP Specification: Release 8

Main procedure context: Identity response supervision

Supervises network-side waiting and retransmission behavior after Identity Request while the MME waits for Identity Response.

Typical message pages: LTE Identity Request

Accepted values:

  • This is a procedure timer, not a returned timer IE carried inside the LTE NAS message body.
  • There is no encoded on-the-wire value to decode directly from Identity Request.
  • In traces, use it to interpret repeated Identity Request transmission and the waiting window before the network abandons the identification branch.

Service restoration

These timers are most useful when reading service request recovery, reject handling, and control-plane user-data behavior.

T3417

3GPP Specification: Release 8

Main procedure context: Service request retransmission control

Supervises the service request attempt window in the standard service restoration path.

Typical message pages: LTE Service Request , LTE Service Accept

Accepted values:

  • This is a procedure timer, not a dedicated NAS timer IE carried in the message payload.
  • There is no returned encoded value to decode directly from the NAS message body.
  • The practical read is behavioral: check how long the UE waits before the service request path retries or times out.

T3417ext

3GPP Specification: Release 8

Main procedure context: Extended service request supervision

Extends the supervision window for service restoration in variants where the longer handling path applies.

Typical message pages: LTE Service Request

Accepted values:

  • This is also a procedure timer rather than a returned NAS timer IE.
  • There is no message-carried encoded value to decode in the same way as T3346 or T3448.
  • Use the trace timing and the wider service procedure context to understand its effective value.

T3482

3GPP Specification: Release 8

Main procedure context: PDN connectivity request supervision

Starts when the UE sends PDN Connectivity Request as a standalone ESM procedure and supervises the wait for accept or reject handling.

Typical message pages: LTE PDN Connectivity Request , LTE Attach Request

Accepted values:

  • This is a procedure timer, not a returned timer IE carried inside the LTE NAS message body.
  • There is no encoded on-the-wire timer value to decode directly from PDN Connectivity Request.
  • When PDN Connectivity Request is sent together with Attach Request, the UE does not start T3482.

T3480

3GPP Specification: Release 8

Main procedure context: Bearer resource allocation or modification request supervision

Supervises the UE-originated bearer resource allocation and bearer resource modification procedures while the UE waits for network outcome.

Typical message pages: LTE Bearer Resource Allocation Request , LTE Bearer Resource Modification Request

Accepted values:

  • This is a procedure timer, not a returned timer IE carried inside the LTE NAS message body.
  • There is no encoded on-the-wire timer value to decode directly from bearer resource request messages.
  • In traces, use it to interpret repeated UE bearer-resource requests and the waiting window before the UE abandons the branch.

T3485

3GPP Specification: Release 8

Main procedure context: EPS bearer activation supervision

Supervises network retransmission and waiting behavior after default or dedicated EPS bearer activation request messages while the network waits for the UE accept or reject message.

Typical message pages: LTE Activate Default EPS Bearer Context Request , LTE Activate Dedicated EPS Bearer Context Request , LTE Activate Dedicated EPS Bearer Context Accept , LTE Attach Accept

Accepted values:

  • This is a procedure timer, not a returned timer IE carried inside the LTE NAS message body.
  • There is no encoded on-the-wire timer value to decode directly from EPS bearer activation request messages.
  • In traces, use it to interpret repeated bearer-activation requests and the waiting window before the network abandons the activation branch.

T3489

3GPP Specification: Release 8

Main procedure context: ESM information request supervision

Supervises network retransmission and waiting behavior after ESM Information Request while the network waits for ESM Information Response.

Typical message pages: LTE ESM Information Request , LTE ESM Information Response

Accepted values:

  • This is a procedure timer, not a returned timer IE carried inside the LTE NAS message body.
  • There is no encoded on-the-wire timer value to decode directly from the ESM information exchange messages.
  • In traces, use it to interpret repeated ESM Information Request transmission and the waiting window before the network aborts the PDN branch.

T3492

3GPP Specification: Release 8

Main procedure context: PDN disconnect request supervision

Supervises the UE-originated PDN disconnect procedure while the network decides whether to continue with bearer release or reject handling.

Typical message pages: LTE PDN Disconnect Request , LTE PDN Disconnect Reject

Accepted values:

  • This is a procedure timer, not a returned timer IE carried inside the LTE NAS message body.
  • There is no encoded on-the-wire timer value to decode directly from PDN Disconnect Request.
  • In traces, use it to interpret repeated disconnect requests and the waiting window before the UE gives up on PDN release.

T3447

3GPP Specification: Release 13

Main procedure context: NAS transport restriction after attach without PDN connection

Restricts when the UE may send Uplink NAS Transport in EMM-CONNECTED mode after attaching without PDN connection, unless one of the allowed exceptions applies.

Typical message pages: LTE Uplink NAS Transport , LTE Attach Accept

Accepted values:

  • This is a procedure timer, not a returned timer IE carried inside the LTE NAS message body.
  • There is no encoded on-the-wire timer value to decode directly from Uplink NAS Transport.
  • In traces, use it to explain why the UE may delay or suppress Uplink NAS Transport after attach without PDN connection.

T3495

3GPP Specification: Release 8

Main procedure context: EPS bearer deactivation supervision

Supervises network retransmission and waiting behavior after Deactivate EPS Bearer Context Request while the network waits for the UE deactivation accept message.

Typical message pages: LTE Deactivate EPS Bearer Context Request

Accepted values:

  • This is a procedure timer, not a returned timer IE carried inside the LTE NAS message body.
  • There is no encoded on-the-wire timer value to decode directly from bearer deactivation request messages.
  • In traces, use it to interpret repeated deactivation requests and the waiting window before the network abandons the release branch.

T3442

3GPP Specification: Release 8

Main procedure context: CS service temporary unavailability wait

Tells the UE to wait before retrying when CS service is temporarily unavailable in service-related reject handling.

Typical message pages: LTE Service Reject

Accepted values:

  • Signaled as GPRS timer in Service Reject.
  • Accepted unit encodings are 2 seconds, 1 minute, or decihours.
  • The timer may also be set to deactivated.
  • If another unit code appears, this protocol version interprets it as multiples of 1 minute.

T3448

3GPP Specification: Release 14

Main procedure context: Control-plane user-data related wait or continuity handling

Returned when control-plane user-data congestion or continuity handling needs timing guidance.

Typical message pages: LTE Service Accept , LTE Service Reject , LTE Tracking Area Update Request

Accepted values:

  • Signaled as GPRS timer 2 in LTE NAS messages.
  • Accepted unit encodings are 2 seconds, 1 minute, or decihours.
  • The timer may also be set to deactivated.
  • In control-plane CIoT paths, zero or deactivated can be treated as abnormal in specific UE handling branches even though the encoding itself is valid.

Returned timer values

In LTE NAS messages, the timer name and the returned timer value IE should be read together but not treated as the same thing. The timer name tells you which NAS behavior is being controlled. The value IE tells you what waiting time or periodic interval was actually assigned in that message.

This is why pages such as LTE Attach Accept, LTE Attach Reject, LTE Service Accept, and LTE Service Reject now link their Related timers field back to this page.

Where to use this page

Use this page as the common lookup target whenever an LTE NAS message lists Related timers. For example, LTE Service Reject can point directly to T3442, T3346, and T3448, while LTE Attach Reject can point directly to T3402 and T3346.

References

  • 3GPP TS 24.301, Non-Access-Stratum (NAS) protocol for EPS
  • 3GPP TS 23.401, GPRS enhancements for E-UTRAN access
  • 3GPP TS 36.300, E-UTRAN overall description

Release 18 reference context used here follows the latest ETSI-hosted TS 24.301 Release 18 publication line.

Related LTE NAS References