Dell PowerConnect J-EX8208, Software Manual

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the edges of the network might be required to alter the CoS settings of the packets that
enter the network to classify the packets into the appropriate service groups.
Figure 79 on page 2861 represents the network scenario of an enterprise. Switch A is receiving
traffic from various network nodes such as desktop computers, servers, surveillance
cameras, and VoIP telephones. As each packet enters, Switch A examines the packet’s
CoS settings and classifies the traffic into one of the groupings defined by the enterprise.
This definition allows Switch A to prioritize resources for servicing the traffic streams it
receives. Switch A might alter the CoS settings of the packets to better match the
enterprise’s traffic groups.
When Switch B receives the packets, it examines the CoS settings, determines the
appropriate traffic groups, and processes the packets according to those settings. It then
transmits the packets to Switch C, which performs the same actions. Switch D also
examines the packets and determines the appropriate groups. Because Switch D sits at
the far end of the network, it can rewrite the CoS bits of the packets before transmitting
them.
Figure 79: Packet Flow Across the Network
Default CoS Behavior on J-EX Series Switches
If you do not configure any CoS settings on the switch, the software performs some CoS
functions to ensure that user traffic and protocol packets are forwarded with minimum
delay when the network is experiencing congestion. Some CoS settings, such as classifiers,
are automatically applied to each logical interface that you configure. Other settings,
such as rewrite rules, are applied only if you explicitly associate them with an interface.
Related
Documentation
Understanding Junos OS CoS Components for J-EX Series Switches on page 2862
•
•
Understanding Junos OS EZQoS for CoS Configurations on J-EX Series Switches on
page 2879
•
Example: Configuring CoS on J-EX Series Switches on page 2883
•
Example: Combining CoS with MPLS on J-EX Series Switches on page 2898
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Chapter 107: Class of Service (CoS)—Overview