TCP's simultaneous open feature is seldom used.
(a) Propose a change to TCP in which this is disallowed. Indicate what changes would be made in the state diagram (and if necessary in the undiagrammed event responses).
(b) Could TCP reasonably disallow simultaneous close?
(c) Propose a change to TCP in which simultaneous SYNs exchanged by two hosts lead to two separate connections. Indicate what state diagram changes this entails, and also what header changes become necessary. Note that this now means that more than one connection can exist over a given pair of {host, port}s. (You might also look up the first "Discussion" item on page 87 of Request for Comments 1122.)