3GPP Message Database

Browse 3GPP telecom signaling message references for NR RRC, 5G NAS, NGAP, LTE RRC, and S1AP, with message overviews, protocol context, and links into related procedures across LTE and 5G networks.

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5G/NR Protocol

NR RRC Messages NR RRC messages manage radio control between the UE and gNB in 5G access. 5G NAS Messages NAS messages connect the UE to the 5G core for mobility, authentication, and session handling. NGAP Messages NGAP carries N2 signaling between the gNB and AMF in 5G core deployments. F1AP Messages F1AP carries signaling between the gNB-CU and gNB-DU in split gNB deployments. E1AP Messages E1AP carries signaling between the CU-CP and CU-UP in split user plane architectures. XnAP Messages XnAP carries signaling between gNB nodes over Xn for mobility and coordination. IMS / SIP Messages This category is reserved for SIP and IMS signaling used by VoNR procedures under the 5G architecture.

LTE Protocol

LTE RRC Messages LTE RRC messages cover system information, connection setup, reconfiguration, security mode, paging, measurements, UE capability exchange, and handover signaling between the UE and eNodeB. LTE NAS Messages LTE NAS messages cover EPS mobility management, attach, authentication, service handling, TAU, detach, and bearer-related signaling between the UE and the MME. S1AP Messages S1AP handles control signaling between LTE eNBs and the MME over the S1-MME interface.

Popular Messages

NAS 5G

5G NAS - Registration Request

Starts a 5G registration or mobility update by sending UE identity and registration intent to the core.

UE -> AMF 3GPP TS 24.501

RRC 5G

5G NR - RRC Setup

Downlink NR RRC message sent by the gNB to establish SRB1 and move the UE into the connected RRC procedure.

gNB -> UE 3GPP TS 38.331

NGAP 5G

5G NR - Initial UE Message

NGAP initiating message used by the NG-RAN to transfer the UE's first uplink NAS message to the AMF.

NG-RAN -> AMF 3GPP TS 38.413

NAS LTE

LTE Attach Request

Attach Request is the EPS NAS message the UE uses to start the LTE attach procedure and ask the network to create EPS mobility-management context.

UE -> MME 3GPP TS 24.301

LTE RRC LTE

LTE RRC Connection Setup

Downlink LTE RRC message sent by the eNodeB to establish SRB1 and move the UE into connected-mode signaling.

eNodeB -> UE 3GPP TS 36.331

LTE RRC LTE

LTE RRC SIB1 - System Information Block Type 1

Broadcast LTE RRC message on BCCH and DL-SCH that gives the UE the essential access identity, cell selection, scheduling, and change-detection context needed before it can use the wider SIB set.

eNodeB -> UE 3GPP TS 36.331

NAS LTE

LTE Security Mode Command

Security Mode Command is the EPS NAS message the MME sends to activate the selected NAS security algorithms and move the LTE/EPS procedure into protected signaling.

MME -> UE 3GPP TS 24.301

RRC 5G

5G NR - RRC Setup Complete

Uplink NR RRC message sent by the UE on SRB1 and DCCH to confirm successful RRC connection establishment and transfer the initial NAS message.

UE -> gNB 3GPP TS 38.331

NAS LTE

LTE Authentication Request

Authentication Request is the EPS NAS message the MME uses to challenge the UE during EPS NAS authentication and verify the subscriber before later security and mobility procedures continue.

MME -> UE 3GPP TS 24.301

LTE RRC LTE

LTE RRC SIB2 - System Information Block Type 2

Broadcast LTE RRC system information block carried inside System Information that gives the UE the common radio, access barring, timer, and uplink-related context needed before normal LTE access can proceed.

eNodeB -> UE 3GPP TS 36.331

Recently Added Messages

NAS 5G

5G NAS - Service Request

Service Request is the NAS message the UE uses to request service resumption when it already has a valid registration context but needs active signaling again.

UE -> AMF 3GPP TS 24.501

NAS 5G

5G NAS - UL NAS Transport

UL NAS Transport is the NAS wrapper message the UE uses to send a payload upward toward the core when the NAS procedure needs to carry additional information transparently.

UE -> AMF 3GPP TS 24.501

NAS 5G

5G NAS - Registration Complete

Registration Complete is the UE-to-AMF NAS message used to confirm that the UE has accepted the registration context returned by the network.

UE -> AMF 3GPP TS 24.501

NAS 5G

5G NAS - Registration Reject

Registration Reject is the NAS message the AMF sends when a 5G registration attempt is refused and the UE must stop the current registration path.

AMF -> UE 3GPP TS 24.501

NAS 5G

5G NAS - Security Mode Command

Security Mode Command is the NAS message the AMF sends to activate the selected NAS security algorithms and move the 5GMM procedure into a protected signaling state.

AMF -> UE 3GPP TS 24.501

NAS 5G

5G NAS - Security Mode Complete

Security Mode Complete is the NAS message the UE sends to confirm that it accepted the selected NAS security algorithms and has switched into the commanded protected signaling state.

UE -> AMF 3GPP TS 24.501

NAS 5G

5G NAS - Security Mode Reject

Security Mode Reject is the NAS message the UE sends when it cannot accept the NAS security configuration selected by the AMF in Security Mode Command.

UE -> AMF 3GPP TS 24.501

NAS 5G

5G NAS - Identity Response

Identity Response is the NAS message the UE sends after Identity Request to provide the specific identity type the network asked for, such as SUCI, IMEI, IMEISV, or another requested identifier.

UE -> AMF 3GPP TS 24.501

NAS 5G

5G NAS - Notification

Notification is the NAS message the network sends to inform the UE about an event that requires the UE's attention in the current mobility-management context.

AMF -> UE 3GPP TS 24.501

NAS 5G

5G NAS - Notification Response

Notification Response is the NAS message the UE sends after receiving Notification from the network to acknowledge the NAS indication and let the protected procedure continue.

UE -> AMF 3GPP TS 24.501

Browse by Procedure

5G

Access and Registration PDU Session Management Mobility Procedures RRC Procedures Security Procedures Voice Call Procedures Network Slice Procedures QoS Policy Procedures Data Path Management Roaming Procedures NTN Procedures Multi-Access Procedures

LTE

Access and Registration Procedures RRC Connection and Security Procedures Bearer and Session Procedures Paging, Idle and Recovery Procedures Mobility and Handover Procedures Measurement and Optimization Procedures VoLTE and IMS Procedures CSFB and Legacy Interworking Procedures Failure Reporting and Troubleshooting Procedures LTE Advanced, Dual Connectivity and WLAN Procedures Broadcast, MBMS and Group Delivery Procedures NB-IoT, Sidelink and Special LTE Procedures