SRVCC (Single Radio Voice Call Continuity)

Also known as: Single Radio Voice Call Continuity

SRVCC is a 3GPP procedure that hands an active VoLTE (or VoNR) voice call from the IMS/PS domain over LTE or NR to a legacy circuit-switched bearer on 2G/3G when packet-switched coverage is lost. It relies on the MME (or AMF) and an SRVCC-capable MSC, and the handover reuses SS7/MAP toward the CS core. SRVCC creates a security transition point where PS-domain protections give way to CS-domain assumptions, and is often abused via SS7 signalling to intercept or redirect voice.

Categories: Radio Access NetworkCore NetworkSignaling

SRVCC in context

The radio access network is the layer where mobile devices attach to the operator's infrastructure. Attacks in this layer include IMSI catching, rogue base stations, downgrade attacks and jamming, and defenses hinge on mutual authentication, integrity-protected signaling and Open RAN supply-chain hygiene.

The mobile core is where subscriber sessions, mobility and policy live. In 4G it is the EPC (MME, HSS, S/PGW); in 5G it is the Service-Based Architecture with AMF, SMF, UPF, AUSF, UDM and the NRF. Core exposure is the difference between a single-subscriber leak and a fleet-wide breach.

To place SRVCC in the wider telecom-security picture, review VoNR, Femtocell, GPRS, IAP, Service-Based Architecture (SBA) Security and IMS-AKA.

Related terms

Related topic hubs

  • SS7 Security SS7/MAP/CAP/SCCP attacks and defenses across 2G/3G interconnect.
  • VoLTE Security IMS/VoLTE signaling risk: SIP, IMS-AKA, media plane attacks.
  • IMS Security Training Training on IMS, VoLTE/VoNR, SIP and RCS security.
  • SS7 Firewall GSMA FS.11 category 1/2/3 SS7 message screening at the STP edge.

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