3GPP Scout / Reference / 5GS NAS timers / T3550

TS 24.501NAS timer

Timer T3550: 5GS mobility management, AMF side

TS 24.501 V20.1.0Clause 10.2Table 10.2.2Checked 2026-10-15

In plain words

This timer starts when REGISTRATION ACCEPT is transmitted as specified in clauses 5.5.1.2.4 and 5.5.1.3.4, and triggers its retransmission on expiry.

Our summary of the spec text quoted below.

What the spec says

Timer value

6s In WB-N1/CE mode, 18s For access via a satellite NG-RAN cell, 11s NOTE 12

Source: 3GPP TS 24.501 V20.1.0, clause 10.2, table 10.2.2. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24501-k10.zip in the 3GPP archive.

Started when

Transmission of REGISTRATION ACCEPT message as specified in clause 5.5.1.2.4 and 5.5.1.3.4

Source: 3GPP TS 24.501 V20.1.0, clause 10.2, table 10.2.2. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24501-k10.zip in the 3GPP archive.

Stopped when

REGISTRATION COMPLETE message received

Source: 3GPP TS 24.501 V20.1.0, clause 10.2, table 10.2.2. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24501-k10.zip in the 3GPP archive.

On expiry

Retransmission of REGISTRATION ACCEPT message

Source: 3GPP TS 24.501 V20.1.0, clause 10.2, table 10.2.2. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24501-k10.zip in the 3GPP archive.

State

5GMM-COMMON-PROCEDURE-INITIATED

Source: 3GPP TS 24.501 V20.1.0, clause 10.2, table 10.2.2. © 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC). Official text: 24501-k10.zip in the 3GPP archive.

Same timer in EPS (TS 24.301)

TS 24.301 defines the corresponding timer for EPS. Its page quotes the EPS wording.

How this page was made

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.