Implications for Network Protocols

Therefore, the satellite channel must control its own allocation:

The advantages of this "shared medium" approach are:

• No Data Link Layer acknowledgements needed, each sender can verify the correctness of their own messages (because they can hear them).
• No routing problems in the Network Layer subnet (no subnet!).
• No congestion problems or topology optimization.
• Mobile users may be supported.

The disadvantages of this approach are:

• Long propagation delay of at least 270msec.
• All users receive all messages, introducing security implications, and there can be no central control of unethical users.

Question: How can a single communication channel be efficiently shared between uncoordinated users?