From: Jared Scrivener (jscrivener@ipexpert.com)
Date: Tue Jul 01 2008 - 08:10:43 ART
Have you ever wondered why DSCP values only go up to 63? DSCP is a newer way
of using the 6 high-order bits in the TOS byte. There are 2 bits left,
however.
The other 2 bits are used for RFC 3168 based TCP Explicit Congestion
Notification. This is a way for the TCP stacks on sending and receiving
devices to back off their traffic flows in response to either the opposite
end or intermediary devices notifying them of congestion in the network. If
you set the "random-detect ecn" command then if a packet that supports ECN
may otherwise have been scheduled for dropping (which is used to force TCP
to reduce window size) it will instead be marked and transmitted so that the
end hosts can back off their transmission window.
FECN and BECN are a similar concept used at OSI Layer 2 in Frame Relay.
Cheers,
Jared Scrivener CCIE2 #16983 (R&S, Security), CISSP
Technical Instructor - IPexpert, Inc.
Telephone: +1.810.326.1444
Fax: +1.810.454.0130
Mailto: jscrivener@ipexpert.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of ccie
Sent: Tuesday, 1 July 2008 3:35 AM
To: ccielab@groupstudy.com
Subject: random-detect ecn !! what is the beneficiality of this command, if
I don't want to drop according to BECN nor FECN
Hi experts
policy-map CON_AVOID
class class-default
bandwidth percent 75
random-detect
random-detect ecn !! what is the beneficiality of this command, if I don't
want to drop according to BECN nor FECN
Regards,
Amin
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