TEID (Tunnel Endpoint Identifier)

The Tunnel Endpoint Identifier is a 32-bit field in every GTP-C and GTP-U packet that identifies the specific bearer or signalling session at the receiving endpoint. Each side of a GTP tunnel allocates and tracks its own TEIDs. Predictable, leaked, or replayed TEIDs are central to many GTP attacks (session hijacking, IMSI disclosure, denial of service), so TEID hygiene, randomisation, rapid expiry, peer validation, is a core control enforced by GTP firewalls.

Categories: Radio Access NetworkCore NetworkSignaling

TEID 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 TEID in the wider telecom-security picture, review GTP-U, CSCF, IMS, AMF, GTP and IPsec.

Related terms

Related topic hubs

  • GTP Firewall GSMA FS.20 GTP-C/GTP-U screening on GRX/IPX borders.
  • GTP Security GTP-C/GTP-U threats across S5/S8, N3/N9 and GRX/IPX borders under GSMA FS.20.
  • Signaling Firewall Unified SS7/Diameter/GTP/SMS signaling firewall framework.
  • SS7 Firewall GSMA FS.11 category 1/2/3 SS7 message screening at the STP edge.

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