How Traffic Prioritization Works - 3Com SuperStack 3 3812 Implementation Manual

How Traffic
Prioritization Works
The 3Com Network Supervisor application supplied on the CD-ROM
accompanying your Switch is the main tool for configuring QoS, and
3Com recommends that you use this application to configure QoS.
You can also configure QoS via the command line interface (CLI), for a
detailed description of the commands that you require refer to the
Management Interface Reference Guide supplied in HTML format on the
CD-ROM that accompanies your Switch.
Configure Class of Service using 3Com Network Supervisor in the
following way:
1 Apply Traffic classification First identify the types of traffic requiring
special treatment. These types are defined in the QoS feature through the
creation of classifiers. The Switch supports two types of packet attributes
on which to classify incoming traffic, Differentiated Services Code Point
(DSCP) and IEEE 802.1D.
2 Identify Service Levels You must then identify the level of service each
classifier should receive. Note that DSCP service levels will be set
somewhere else in the network and not in the Switch itself. Note also
that 802.1D service levels are fixed and cannot be altered.
3 Create Profiles The next step is to create a profile, which associates
classifiers with service levels.
4 Apply CoS profile After a CoS profile has been created, it can be
assigned to the Port(s). When the profile is assigned to the port(s), the
QoS configuration defined in the profile will immediately become active.
Traffic prioritization ensures that high priority data is forwarded through
the Switch without being delayed by lower priority data. Traffic
prioritization uses the eight traffic queues that are present in the
hardware of the Switch to ensure that high priority traffic is forwarded on
a different queue from lower priority traffic. High priority traffic is given
preference over low priority traffic to ensure that the most critical traffic
gets the highest level of service.
The Switch employs three methods of classifying traffic for prioritization.
Traffic classification is the means of identifying which application
generated the traffic, so that a service level can be applied to it.
The three supported methods for classifying traffic are:

How Traffic Prioritization Works

53