Registration, security, PDU session setup, mobility, paging, handover, and 5GC/NG-RAN signalling.
LTE Call FlowsLTE attach, authentication, security, service request, bearer setup, paging, TAU, and handover procedures.
VoNR Call Flow and ProceduresVoNR architecture, IMS registration, mobile-originated call, mobile-terminated call, emergency call, and EPS fallback.
VoLTE Call FlowsVoLTE registration, IMS session setup, dedicated bearer setup, mobile-originated and mobile-terminated calls, and call release.
Jump directly into the 5G and LTE call-flow category hubs.
Registration, service request, paging, and deregistration entry flows.
PDU Session ManagementPDU session establishment, modification, release, and recovery paths.
Mobility ProceduresN2/Xn handover, path switch, inter-RAT mobility, and mobility updates.
RRC ProceduresRRC setup, resume, reconfiguration, re-establishment, and release handling.
Security ProceduresAuthentication, NAS security, AS security, and identity recovery flows.
Voice Call ProceduresVoNR, IMS registration, voice continuity, EPS fallback, and emergency voice.
Network Slice ProceduresSlice-aware registration, rejection, admission, and session setup.
QoS Policy ProceduresQoS flow setup, modification, policy control, and charging updates.
Data Path ManagementUser-plane activation, path switching, continuity, and recovery behavior.
Roaming ProceduresVisited-network registration, authentication, and session-routing procedures.
NTN ProceduresNon-terrestrial access registration, timing, and session adaptations.
Multi-Access ProceduresATSSS, non-3GPP access, path steering, and multi-access continuity.
Attach, service request, TAU, paging, emergency attach, and detach.
RRC Connection & SecurityRRC setup, security mode, authentication, capability, and release procedures.
Bearer & SessionDefault bearer, dedicated bearer, E-RAB setup, modification, and release.
Paging, Idle & RecoveryPaging, idle return, connection release, resume, and radio-failure recovery.
Mobility & HandoverX2, S1, intra-LTE, inter-frequency, inter-RAT, and failure recovery flows.
Measurement & OptimizationMeasurement configuration, reporting, events, ANR, MDT, and positioning flows.
VoLTE & IMSIMS registration, VoLTE calls, dedicated bearer setup, SMS over IMS, and SRVCC.
CSFB & Legacy InterworkingCS fallback, GERAN/UTRAN/CDMA2000 interworking, and legacy continuity.
Failure & TroubleshootingFailure indication, error handling, recovery, and troubleshooting-oriented flows.
LTE-Advanced & WLANDual connectivity, split bearer, LWA, LWIP, and WLAN interworking.
Broadcast, MBMS & Group DeliverySystem information, ETWS, CMAS, MBMS, and group delivery procedures.
NB-IoT, Sidelink & Special LTENB-IoT, sidelink, V2X, relay, NTN, and special-case LTE procedures.
Core 5G registration, session, paging, mobility, security, and voice procedure entry points.
LTE access, bearer, paging, TAU, handover, CSFB, and radio-control procedures.
Voice-service procedures from IMS registration through call setup, emergency handling, and release.
Use message libraries while reading call flows to inspect each message, direction, trigger, and key fields.
A telecom call flow is a step-by-step signalling sequence showing how network nodes exchange protocol messages during procedures such as registration, attach, bearer setup, PDU session establishment, handover, paging, or IMS call setup.
The call-flow section covers 5G, LTE, IMS, VoLTE, VoNR, registration, attach, security, session setup, bearer setup, mobility, handover, paging, and troubleshooting flows.
Use call-flow pages to understand message order, node roles, interfaces, expected responses, and where failures may occur in protocol traces.
Call-flow pages explain the full procedure sequence. Message pages explain individual protocol messages, fields, direction, and troubleshooting details.
Use the related message libraries for 5G, LTE, NGAP, NAS, RRC, S1AP, and IMS SIP.