Question: In GPRS networks, what is a characteristic of IP datagrams used within the context of a TCP connection in the packet domain?
Option 1: They always require encryption for transmission.
Option 2: They are routed based solely on the mobile terminal's IMSI.
Option 3: The TCP/IP header may be compressed to reduce overhead.
Option 4: They are restricted from accessing external IP networks.
Explanation: In the context of GPRS and its interworking with Internet Protocol (IP) networks, optimizing data transmission is crucial. One method to achieve this is by compressing headers in protocols, which reduces overhead and enhances efficiency. Specifically, for TCP/IP datagrams transmitted within a TCP connection, header compression can significantly decrease the amount of data being sent, thereby improving network performance and user experience.