Disallow direct tracking of TCP.
Address some reviewer comments: Add section on applicability. Change default Ack Ratio to two. Add paragraph about packet sizes.
Refer explicitly to SACK-based TCP, include more detail on sender-side congestion control, use appropriate "byte" counting, add Security and IANA considerations, small wording updates.
Clarify ECN nonces, piggybacked acknowledgements, and the Acknowledgement Number. Wording.
Clarify discussion on when to acknowledge an acknowledgement.