Origination Time Stamp
Origination Time Stamp is the time at which the originating entity initiated the request. The time stamp is in UTC format.
MME/SGSN and TWAN/ePDG contain the Origination Time Stamp IE on S11/S4 and S2a/S2b interfaces, respectively.
SGW receives the Origination Time Stamp IE from MME/SGSN and includes the IE on the S5/S8 interface.