Hi all

In aggressive mode and with Intercept mode, the retransmission timeout will
reduce to half. In the highlighted snippet, it is stated that the timeout
will be 2, 4,8 and 16. Why is it increasing? It should be in reverse right?
I know, I am missing something. Please comment.


Snippet from
http://www.cisco.com/en/US/docs/ios/sec_data_plane/configuration/guide/sec_cfg_tcp_intercpt_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp1000893
 Changing the TCP Intercept Aggressive Thresholds

Two factors determine when aggressive behavior begins and ends: total
incomplete connections and connection requests during the last one-minute
sample period. Both thresholds have default values that can be redefined.

When a threshold is exceeded, the TCP intercept assumes the server is under
attack and goes into aggressive mode. When in aggressive mode, the following
occurs:

•Each new arriving connection causes the oldest partial connection to be
deleted. (You can change to a random drop mode.)

•The initial retransmission timeout is reduced by half to 0.5 seconds, and
so the total time trying to establish the connection is cut in half. (When
not in aggressive mode, the code does exponential back-off on its
retransmissions of SYN segments. The initial retransmission timeout is
1 second. The subsequent timeouts are 2 seconds, 4 seconds, 8 seconds, and
16 seconds. The code retransmits 4 times before giving up, so it gives up
after 31 seconds of no acknowledgment.)

•If in watch mode, the watch timeout is reduced by half. (If the default is
in place, the watch timeout becomes 15 seconds.)



With regards

Kings
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