Satellite KPI to measure Service Access Time for 3G and 4G

Hi Folks,
Any one is using Satellite KPI to measure Service Access Time for 3G and 4G?
If yes, what is value of that KPI or attach time (Ms)?

Attach time usually range 400-600 ms on average for short call scenario.
And Service delay time usually just 20-25 ms less than attach time.
In LTE Ericsson system.

I am having +900 ms.

Service from idle to connected, right?

No,
RRC request (just after attach request) to RRC reconfig complete (just before attach complete).

Can be possible depend on different network.

Yes, I am having doubt that delay during authentication procedures and some times failures.

This depend upon CORE delay.

Yes I am checking E2E.

Sat formula = attach time/successful attach.

Yes, it depends.