Question: Where does encapsulation functionality exist in a GPRS network to ensure correct delivery of PDP PDUs to their associated PDP context?
Option 1: Only at the MS (Mobile Station) and GGSN/P-GW (Gateway GPRS Support Node/Packet Data Network Gateway)
Option 2: Exclusively at the RNC (Radio Network Controller), SGSN (Serving GPRS Support Node), and S-GW (Serving Gateway)
Option 3: At multiple points including the MS, RNC, Iu mode BSC (Base Station Controller), SGSN, S-GW, and GGSN/P-GW
Option 4: Solely at the network edge, i.e., only at the GGSN/P-GW and the MS
Explanation: Encapsulation is crucial for routing PDP PDUs correctly within a GPRS network. To ensure seamless delivery across various network segments, encapsulation functionality must be present at multiple strategic points, including the Mobile Station for initial encapsulation, Radio Network Controller and Iu mode Base Station Controller for radio interface aspects, Serving GPRS Support Node and Serving Gateway for managing network mobility and session contexts, and finally at the Gateway GPRS Support Node/Packet Data Network Gateway for interfacing with external packet data networks. This ensures PDP PDUs are correctly associated with their PDP context throughout.