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FTOS Configuration Guide for the C-Series - Force10 Networks

FTOS Configuration Guide for the C-Series - Force10 Networks

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Apply a WRED profile to traffic<br />

Once you create a WRED profile you must specify to which traffic <strong>FTOS</strong> should apply <strong>the</strong> profile.<br />

<strong>FTOS</strong> assigns a color (also called drop precedence)—red, yellow, or green—to each packet based on it<br />

DSCP value be<strong>for</strong>e queuing it. DSCP is a 6 bit field. <strong>Force10</strong> uses <strong>the</strong> first three bits of this field (DP) to<br />

determine <strong>the</strong> drop precedence. DP values of 110 and 100 map to yellow, and all o<strong>the</strong>r values map to green.<br />

If you do not configure <strong>FTOS</strong> to honor DSCP values on ingress (Honor DSCP values on ingress packets on<br />

page 571) see all traffic defaults to green drop precedence.<br />

Assign a WRED profile to ei<strong>the</strong>r yellow or green traffic from QOS-POLICY-OUT mode using <strong>the</strong><br />

command wred.<br />

Configure WRED <strong>for</strong> Storm Control<br />

Configure WRED <strong>for</strong> Storm Control is supported only on plat<strong>for</strong>m e<br />

Storm control limits <strong>the</strong> percentage of <strong>the</strong> total bandwidth that broadcast traffic can consume on an<br />

interface (if configured locally) or on all interfaces (if configured globally). For storm-control broadcast<br />

50 out, <strong>the</strong> total bandwidth that broadcast traffic can consume on egress on a 1Gbs interface is 512Mbs.<br />

The method by which packets are selected to be dropped is <strong>the</strong> "tail-drop" method, where packets<br />

exceeding <strong>the</strong> specified rate are dropped.<br />

WRED can be used in combination with storm control to regulate broadcast and unknown-unicast traffic.<br />

This feature is available through an additional option in command storm-control [broadcast |<br />

unknown-unicast] at CONFIGURATION. See <strong>the</strong> <strong>FTOS</strong> Command Line Reference <strong>for</strong> in<strong>for</strong>mation on<br />

using this command.<br />

Using <strong>the</strong> command storm-control broadcast 50 out wred-profile, <strong>for</strong> example, first <strong>the</strong> total bandwidth<br />

that broadcast traffic can consume is reduced to 50% of line rate. Even though broadcast traffic is<br />

restricted, <strong>the</strong> rate of outgoing broadcast traffic might be greater than o<strong>the</strong>r traffic, and if so, broadcast<br />

packets would consume too much buffer space. So, <strong>the</strong> wred-profile option is added to limit <strong>the</strong> amount of<br />

buffer space that broadcast traffic can consume.<br />

Display Default and Configured WRED Profiles<br />

Display default and configured WRED profiles and <strong>the</strong>ir threshold values using <strong>the</strong> command show qos<br />

wred-profile from EXEC mode, as shown in Figure 406.<br />

Figure 406 Displaying WRED Profiles<br />

<strong>Force10</strong>#show qos wred-profile<br />

Wred-profile-name min-threshold max-threshold<br />

wred_drop 0 0<br />

wred_ge_y 1000 2000<br />

wred_ge_g 2000 4000<br />

wred_teng_y 4000 8000<br />

wred_teng_g 8000 16000<br />

<strong>FTOS</strong> <strong>Configuration</strong> <strong>Guide</strong>, version 7.7.1.0 575

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