Thus it is supposed that {TAIL ~ the as old acting SGSN} receives {HEAD ~ a GTP U packet} from a GGSN 
Thus it is supposed that { TAIL ~ the as old acting SGSN } receives { HEAD ~ a GTP U packet } from a GGSN
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH