From: Vincent Mashburn (vmashburn@fedex.com)
Date: Mon Jan 29 2007 - 11:24:54 ART
Think about how policing works for a second. If congestion occurs on a
policed link (or type of traffic), the policer can either drop the
traffic or remark it to a lesser preferred DSCP value. When the packet
is remarked, the DSCP value in the IP header is re-written. This is
similar to what is happening with ECN. When congestion occurs, the ECN
bit in the DSCP field is turned on, allowing flow control for all
endpoints that understand ECN. Now unless the routers and / or end
systems are configured to understand and respond to ECN's, they mean
absolutely nothing. Hope this helps.
Vince Mashburn
Sr. Voice / Data Engineer
901-263-5072
CCVP, CCNP
Cisco IP Telephony Support Specialist
Cisco IP Telephony Operations Specialist
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Blastmor
Sent: Sunday, January 28, 2007 4:37 AM
To: Cisco certification
Subject: ECN and "bandwidth" keyword interconnection
In IEWBv3 Vol II Lab 7 Task 8.1 there is a task about enabling ECN when
congestion occurs.
But I misunderstand when the ECN starts marking packets.
And how can we explicitly configure threshold of interface load when ECN
marking should be started?
In UniverCD there are only poor examples and explanations (such as ECN
is
switched on when congestion occurs - that's all)
-- SY, Alexey
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