GMSC (Gateway Mobile Switching Center)

The Gateway MSC is the MSC that interconnects a mobile network with the PSTN or another mobile network for incoming calls. It performs the SRI query to the HLR to find the called subscriber's current MSC and routes the call accordingly. GMSC functionality is largely subsumed by IMS gateways (MGCF, IBCF) in modern VoLTE-based networks.

Categories: Core NetworkRoaming and InterconnectIdentity and Subscriber

GMSC in context

The mobile core carries subscriber sessions, mobility and policy. 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.

Roaming and interconnect are where two operators exchange signaling and user-plane traffic. Trust boundaries here are the primary attack surface for location tracking, SMS interception and fraud, which is why GSMA now mandates SEPP with PRINS on 5G interconnect.

To place GMSC in the wider telecom-security picture, review GSMA, GGSN, HLR, PGW, Cryptography and GTP Firewall: each entry cross-references back to this page so you can walk the topic in either direction.

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