TEIDs

TEID, or Tunnel Endpoint Identifier, is a field within the control plane signaling messages of certain network protocols, most notably within the Gateway General Packet Radio Service (GPRS) Tunneling Protocol (GTP). Its primary function is to uniquely identify a specific GTP tunnel between two endpoints. These endpoints are typically a Serving GPRS Support Node (SGSN) and a Gateway GPRS Support Node (GGSN) in a mobile network, or between other network elements like the eNodeB and the Mobility Management Entity (MME) in LTE networks.

When data packets are tunneled between these network nodes, the TEID acts as a label or reference number. This allows the receiving node to distinguish between different active tunnels originating from the same source node. Without the TEID, a node receiving multiple GTP messages from a single source would not know which data session or flow each incoming message belonged to. This is crucial for managing mobile data traffic, charging, and ensuring that data is correctly routed to its intended destination within the mobile core network. The TEID is assigned during the tunnel establishment process and is maintained throughout the life of the tunnel.