Timer value
NOTE 3
Source: 3GPP TS 24.301 V20.1.0, clause 10.2, table 10.2.1. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24301-k10.zip in the 3GPP archive.
3GPP Scout / Reference / EPS NAS timers / T3423
TS 24.301NAS timer
Timer T3423: EPS mobility management, UE side
In plain words
The UE starts T3423 when T3412 expires while ISR is activated and either T3346 runs or the UE is in a listed EMM-REGISTERED substate. The UE sets TIN to P-TMSI when T3423 expires.
Our summary of the spec text quoted below.
What the spec says
Started when
T3412 expires while ISR is activated and either T3346 is running, or the UE is in one of the following states: - EMM-REGISTERED.NO-CELL-AVAILABLE; - EMM-REGISTERED.PLMN-SEARCH; -EMM-REGISTERED.UPDATE-NEEDED; or -EMM-REGISTERED.LIMITED-SERVICE.
Source: 3GPP TS 24.301 V20.1.0, clause 10.2, table 10.2.1. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24301-k10.zip in the 3GPP archive.
Stopped when
When entering state EMM-DEREGISTERED or when entering EMM-CONNECTED mode.
Source: 3GPP TS 24.301 V20.1.0, clause 10.2, table 10.2.1. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24301-k10.zip in the 3GPP archive.
On expiry
Set TIN to "P-TMSI". For A/Gb mode or Iu mode, see 3GPP TS 24.008 [13]
Source: 3GPP TS 24.301 V20.1.0, clause 10.2, table 10.2.1. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24301-k10.zip in the 3GPP archive.
State
EMM-REGISTERED
Source: 3GPP TS 24.301 V20.1.0, clause 10.2, table 10.2.1. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24301-k10.zip in the 3GPP archive.
Note 3 of the table
NOTE 3: The value of this timer may be provided by the network in the ATTACH ACCEPT message and TRACKING AREA UPDATE ACCEPT message. The default value of this timer is identical to the value of T3412.
Source: 3GPP TS 24.301 V20.1.0, clause 10.2, table 10.2.1. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24301-k10.zip in the 3GPP archive.
How this page was made
3GPP Scout built this page from TS 24.301 V20.1.0 as indexed on 2026-10-15. The quotes are copied from the spec, and code checks each one against the stored text and the 3GPP archive file before publishing. The plain-words line was written by an AI model (GPT-6 Sol) and checked against the quotes by a second AI model from another company (Claude Opus 5.5). The official 3GPP text governs.