Mobile Packet Core

In mobile network, we have the control plane, and the user plane.

The control plane carries signaling messages between the nodes

While, the user plane carries user data.

As example, in the process of the 'PDP context activation', 

First, the nodes use the 'Control Plane' to exchange below signaling messages that will establish the PDP between the UE and the GGSN,

After the PDP is established, the 'User Plane' carries the user data sent between the UE, and the PDN.

Summary

• The 'Control Plane' carries signaling messages between nodes.
• The 'User Plane' carries user data sent between the UE and the PDN.