Administrator Guide

Layer 2 Switching Commands 725
0 - 6.25% of maximum drop probability
1 - 18.75% of maximum drop probability
2 - 30.25% of maximum drop probability
3 - 43.75% of maximum drop probability
4 - 56.25% of maximum drop probability
5 - 68.75% of maximum drop probability
6 - 81.25% of maximum drop probability
7 - 92.75% of maximum drop probability
As an example, with a drop probability of 50%, a minimum threshold of 10%
and a maximum threshold of 90%, the drop probability from 10% to 20%
congestion is 3.125%, from 21% to 30% congestion is 9.375%, ...
The drop probability scale supports values in the range 0-10% and the discrete
values 25%, 50%, 75%, and 100%. Other values are silently truncated to the
next lower value by the hardware.
Explicit Congestion Notification (ECN):
ECN capability is an end-to-end feedback mechanism. Both ends of the TCP
connection must participate. When ECN is enabled, packets marked as ECN
capable and selected for discard by WRED are marked CE and are not
dropped. In cases of extreme congestion, ECN capable packets may be
dropped.
Use the show interfaces traffic command to see color aware drops and
congestion levels.
ECN capability can be enabled in Windows Server 2008 and later releases
using the following command:
netsh interface tcp set global ecncapability=enabled
N1500 Series Switches
N1500 Series switches only support a simple RED capability. The N1500
Series switch does not support configuration of the maximum threshold nor
can the threshold or drop probability be configured for non-TCP traffic.
Dell Networking N1500 Series switches implements a simple Random Early
Discard (RED) capability. Only the minimum threshold (min-thresh) and
drop probability (drop-prob-scale) may be configured for the TCP colors
2CSNXXX_SWUM204.book Page 725 Monday, January 25, 2016 1:25 PM