Question on detecting duplicate segments
Murali Bashyam <mbashyam@cisco.com> Sun, 11 May 2003 21:03 UTC
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Date: Sun, 11 May 2003 14:03:37 -0700
From: Murali Bashyam <mbashyam@cisco.com>
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Subject: Question on detecting duplicate segments
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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
- Question on detecting duplicate segments Murali Bashyam