For an MS to be able to send and receive data to and from the PDN, it must have an active PDP context. The 'PDP context' exist on the MS, the SGSN, and the GGSN. This PDP context can be in one of two states. Those two states are the Session Management 'SM' states.
Session Management 'SM' states
The SM sates are 'INACTIVE' and 'ACTIVE'.
In this state, the MS can’t send or receive data to and from the PDN.
In this state, the MS can send and receive data to and from the PDN.
Transition between ACTIVE and INACTIVE states
Moving from ACTIVE to INACTIVE,
An ACTIVE PDP context moves to INACTIVE state when,
- 'PDP deactivation' procedure is initiated.
- The MM state of the MS moves to IDLE in 2G, or PMM-DETACHED in 3G.
Later, we will dicuss the process of 'PDP deactivation'.
Moving from INACTIVE to ACTIVE,
- The PDP context moves from INACTIVE to ACTIVE state when a 'PDP context activation' procedure is done.