Question: What action does the network take when it receives an ACTIVATE PDP CONTEXT REQUEST message specifying a transaction identifier relating to a PDP context not in state PDP-INACTIVE?
Option 1: The network sends a SM-STATUS message with cause #81 "invalid transaction identifier value" and remains in the PDP-INACTIVE state.
Option 2: The network ignores the message and does not take any further action.
Option 3: The network deactivates the old PDP context relating to the received transaction identifier without notifying the MS and continues with the activation procedure of a new PDP context as indicated in the received message.
Option 4: The network sends an error message to the MS indicating that the transaction identifier is invalid.
Explanation: According to the session management procedures, when the network receives an ACTIVATE PDP CONTEXT REQUEST message specifying a transaction identifier relating to a PDP context not in state PDP-INACTIVE, it deactivates the old PDP context without notifying the MS and continues with the activation procedure of a new PDP context as indicated in the received message. This ensures that the network maintains a consistent state and avoids conflicts between different PDP contexts.