这个在TS24.008的9.4.3中有明确说明:
“This message is sent by the MS to the network if at least one of the following conditions is fulfilled:
- a P-TMSI and/or a TMSI was included within the attach accept message; or
- the network has requested the MS to provide feature-related information.”
主要是前者的情况,就是SGSN给MS分配了P-TMSI。