07.603GPPGeneral Packet Radio Service (GPRS)Mobile Station (MS) supporting GPRSTS
The following figure 2: Transmission Plane shows the relationship of the GPRS Bearer terminating at the SNDCP layer to the rest of the GPRS environment. It is shown for reference purposes only and detailed information can be found in GSM 03.60.
NOTE: In the SGSN and GGSN UDP is mandatory. TCP is optional but recommended for X.25 services.
Figure 2: GPRS Transmission Plane