Subject: Question on detecting duplicate segments

From: Murali Bashyam <[email-masked]>
Date: Sun, 11 May 2003 14:03:37 -0700

Hi

This pertains to the subject of detecting duplicate segments from
earlier incarnations of the same connection. For the same incarnation of
a connection, RFC 1323 recommends PAWS and it works correctly to detect
duplicate segments, but for a different incarnation (Appendix B.2 of the
RFC), it seems to indicate that PAWS as it is  will not work, and it
needs to be augmented with a  mechanism which  maintains a per host
timestamp cache which saves the last timestamp received from that host
and this value is needed to be used in the PAWS test.

I dont quite understand this, if the timestamp clock  of the sender is
guaranteed to increment by at least 1 since the last time the connection
was closed, the duplicate which appears after the new incarnation of the
connection has been established, should be detected by the PAWS test as
is, without requiring any additional mechanism. My intent is to
understand whether it is true that PAWS test (as it is w/o requiring any
additional mechanism) can  replace the functionality of detecting and
expiring duplicate segments provided by the TIME-WAIT state.

Thanks,
Murali