PLMN (Public Land Mobile Network)

A Public Land Mobile Network is a regulator-licensed mobile network identified globally by the combination of its Mobile Country Code and Mobile Network Code (the PLMN-ID, e.g. 208-10 for a French operator). The PLMN-ID is broadcast on every cell, included in the IMSI/SUPI, and used in inter-operator signalling to identify the home and visited operator. In 5G, PLMN-IDs feed into SEPP routing and PRINS protection of N32 messages between networks.

Categories: Radio Access NetworkSignalingRoaming and Interconnect

PLMN 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.

Signaling protocols carry the control-plane instructions that set up calls, register subscribers, hand over sessions and route SMS. SS7, Diameter, GTP-C and SIP are the four dominant families, and interconnect exposure of any of them is treated by GSMA FS.11 / FS.19 / FS.20 as a top-tier telecom risk.

To place PLMN in the wider telecom-security picture, review PSTN, Firewall, Interconnect Security Model, Inter-PLMN Security, Telecom Attack Surface Mapping and GRX.

Related terms

Related topic hubs

  • 5G Security 5G SBA, SEPP, SUCI, 5G-AKA, N32 and service-based interface security.
  • Roaming Security IPX/GRX interconnect risk, home-routed vs local-breakout, SEPP.
  • SEPP Security N32-c/N32-f, PRINS, JWE and OAuth 2.0 at the 5G roaming edge.
  • 5G Penetration Testing Pentesting the 5G core, SBA, SEPP, and gNB interfaces.

More from the TelcoSec Glossary

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