问题补充：2012-7-2 16:59
我查了下3gpp协议，不知道对不对

EPS update type value (octet 1, bit 1 to 3)

Bits

3  2  1    
0  0  0    TA updating
0  0  1    combined TA/LA updating
0  1  0    combined TA/LA updating with IMSI attach
0  1  1    periodic updating
1  0  0    unused; shall be interpreted as "TA updating", if received by the network.
1  0  1    unused; shall be interpreted as "TA updating", if received by the network.

All other values are reserved.

"Active" flag (octet 1, bit 4)
Bit

4        
0        No bearer establishment requested
1        Bearer establishment requested