3GPP Scout / Reference / 5GS NAS timers / T3540
TS 24.501NAS timer
In plain words
The UE starts T3540 upon receiving REGISTRATION REJECT or DEREGISTRATION REQUEST with listed 5GMM causes and releases the NAS signalling connection on expiry where specified.
Our summary of the spec text quoted below.
10s NOTE 7 (applicable to case f) in clause 5.3.1.3) NOTE 8 In WB-N1/CE mode, 34s (applicable to case f) in clause 5.3.1.3) NOTE 11 For access via a satellite NG-RAN cell, default 22s (applicable to case f) in clause 5.3.1.3) NOTE 12 NOTE 13 NOTE 14
Source: 3GPP TS 24.501 V20.1.0, clause 10.2, table 10.2.1. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24501-k10.zip in the 3GPP archive.
REGISTRATION REJECT message or DEREGISTRATION REQUEST message received with any of the 5GMM cause #3, #6, #7, #11, #12, #13, #15, #27, #31, #36, #62, #72, #73, #74, #75, #76, #78 or #80. [...]
Source: 3GPP TS 24.501 V20.1.0, clause 10.2, table 10.2.1. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24501-k10.zip in the 3GPP archive.
N1 NAS signalling connection released PDU sessions have been set up except for the case the UE has set Request type to "NAS signalling connection release" in the UE request type IE in the REGISTRATION REQUEST message as described in clause 5.3.1.3 case b) Other use cases see clause 5.3.1.3
Source: 3GPP TS 24.501 V20.1.0, clause 10.2, table 10.2.1. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24501-k10.zip in the 3GPP archive.
Release the NAS signalling connection for the cases a), a1), b), c), d), e), f), g), h), i), j), k) [...]
Source: 3GPP TS 24.501 V20.1.0, clause 10.2, table 10.2.1. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24501-k10.zip in the 3GPP archive.
Table 10.2.1 has 2 more rows for T3540 that cover other cases. Read them in the official text.
TS 24.301 defines the corresponding timer for EPS. Its page quotes the EPS wording.
3GPP Scout built this page from TS 24.501 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.