NSAPI

NSAPI refers to 'Network layer Service Access Point Identifier'.

The MS generates the NSAPI in the 'PDP context activation' procedure, And the MS sends it in the 'Active PDP context request' sent to the SGSN.

After the 'PDP context activation' completes, a 'PDP context' will exist on the MS, the SGSN, and the GGSN.

The NSAPI will exist in the PDP context. And this will help the MS, the SGSN, and the GGSN, to identify the PDP context from other PDP contexts.

TI

The TI refers to 'Transaction Identifier'.

The MS or the SGSN generates the TI in the process of 'PDP context activation'. And the TI differentiates the PDP context from other PDP contexts.

In fact, the MS, or the SGSN is having the ability to initiate the 'PDP context activation' procedure.

In case the MS initiated the PDP activation, The MS will generate the TI.

While, in case the SGSN initiated the PDP activation, the SGSN will generate the TI.

Also, the MS sends the TI in the “Active PDP context request”, and the TI will exist in the PDP context, which exist on the MS, the SGSN , and the GGSN.