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    <title>Information About QoS </title>
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<a name="wp1247974"> </a><h1 class="pTitle">
Information About QoS

</h1>
<a name="wp1247975"> </a><p class="pBody">
QoS implementation in the Cisco MDS 9000 Family follows the differentiated services (DiffServ) 
model. The DiffServ standard is defined in RFCs 2474 and 2475. The Cisco MDS 9000 Family supports 
QoS for internally and externally generated control traffic. Within a switch, control traffic is sourced to 
the supervisor module and is treated as a high priority frame. By default, the QoS feature for certain 
critical control traffic is enabled. These critical control frames are assigned the highest (absolute) 
priority. A high priority status provides absolute priority over all other traffic and is assigned in the 
following cases:

</p>
<div class="pSmartList1"><ul class="pSmartList1">
<a name="wp1247976"> </a><li class="pSmartList1">Internally generated time-critical control traffic (mostly Class F frames).
</li>
<a name="wp1247977"> </a><li class="pSmartList1">Externally generated time-critical control traffic entering a switch in the Cisco MDS 9000 Family 
from a another vendor’s switch. High priority frames originating from other vendor switches are 
marked as high priority as they enter a switch in the Cisco MDS 9000 Family.
</li>
</ul></div>
<a name="wp1247978"> </a><p class="pBody">
Quality of service (QoS) offers the following advantages:

</p>
<div class="pSmartList1"><ul class="pSmartList1">
<a name="wp1247979"> </a><li class="pSmartList1">Provides relative bandwidth guarantee to application traffic.
</li>
<a name="wp1247980"> </a><li class="pSmartList1">Controls latency experienced by application traffic.
</li>
</ul></div>
<a name="wp1243643"> </a><p class="pBody">
Prioritizes one application over another (for example, prioritizing transactional traffic over bulk traffic) 
through bandwidth and latency differentiation.

</p>
<hr /><br><p class="pBody">Copyright 2010-2013, Cisco Systems, Inc. All rights reserved.</p> 

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