Which procedure establishes the data tunnel between a 2G/2.5G phone and the GGSN, making internet access possible?
The PDP Context Activation — "Activate PDP Context Request" — builds the tunnel between the smartphone and the GGSN, the core network element that manages internet access.
What it does:
- After GPRS Attach (registration for data), the phone still has no usable data path — it must request a PDP Context (Packet Data Protocol context)
- The Activate PDP Context Request asks the network to set up the tunnel from the phone through the SGSN to the GGSN
- The GGSN (the gateway managing access to external networks) assigns the phone its IP address and connects the tunnel to the internet
What a PDP context contains: the IP address, the APN (which external network to connect to), and QoS parameters — essentially "my data session profile."
The lineage: this is the ancestor of what later generations call bearers/sessions: GPRS PDP Context → LTE EPS Bearer (over GTP tunnels) → 5G PDU Session. The names change; the concept — an explicit, tunneled data session through the core — survives to this day.
Tip: Remember the order: (1) GPRS Attach = "I'm here and allowed to use data", (2) Activate PDP Context = "now actually build me my pipe to the internet."
Go deeper:
GPRS core network — PDP context & GTP tunnels (Wikipedia) — what the PDP context data structure holds (IP address, IMSI, tunnel endpoint IDs) and how GTP-U/GTP-C carry the user pipe from SGSN to GGSN.