TS2 --- A Modified TCP Timestamps Mechanism
This memo proposes a modified TCP Timestamps mechanism called "TS2". It uses the existing "TCP Timestamps option" specified in RFC1323 and a new TCP option called "the TCP Old Timestamps option", which is specified in this memo. As a fallback, an RFC1323-compatible mode called "TS1" is also available. The base mechanism of TS2 includes the definitions of those two TCP Timestamps options, mode negotiation to enable TS1 or TS2, and a rule for updating internal states. The applied mechanisms of TS2 include an accurate RTT measurement mechanism that is correct even for duplicate ACK segments (RTTM/TS2), a reordering-robust mechanism to detect wrapped sequence numbers (PAWS/TS2), a lightweight mechanism to detect spoofed segments (PASA/TS2), a loss inference mechanism applicable to both original and retransmitted data segments (DLI/TS2), and a spurious loss inference detection mechanism that operates without waiting for one RTT by sending arbitrary in-window data (SLID/TS2).