Traffic Prioritization and your Switch 51
How traffic is processed to provide Quality of Service
A received packet at the ingress port is checked for its DSCP and IEEE
802.1D attributes to determine the level of service that the packet should
receive .
802.1D packets are categorized into the 8 traffic classes defined by IEEE
802.1D; the higher the class the higher the pr iority given the packet on
transmission.
DSCP packets are categorized into the six service levels as shown in
Figure12 and mapped to the appropriate queue.
The priority defi ned in the service le vel directs the pack et to the
appropriate egress queue. When a packet comes in with both 802.1D
and DSCP priority markings, the higher of the priorities will be used.
Received packets in the Switch 4200 are only checked for DSCP and
802.1D attributes. No other attributes are supp orted.
Traffic queues are preset on a per-unit basis on the Switch 4200.
Configuring traffic prioritization for QoS on a Switch 4200
QoS can be configured on your Switch using the 3Com Network
Supervisor or via the Command Line Inter face (CLI).
The 3Com Network Supervisor application suppli ed on the CD-ROM
accompanying your Switch is the m ain tool for configuring QoS, and
3Com recommends that you use this application t o configure QoS.
You can also configure QoS via the command line interface (CLI). For a
detailed description of the commands that you requ ire refer to the
Management Interface Reference Guide supplied in HTML format on the
CD-ROM that accompanies your Switch.
Configure Quality of service in the Switch 4200 in the following way:
1 Apply Traffic classification First identify the t ypes of traffic requiring
special treatment. These types are defined in the QoS feature through the
creation of classifiers. The Switch 4200 supports t wo 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