3Com SuperStack 3 3812 Implementation Manual

Contents

How Traffic Prioritization Works 53The 3Com Network Supervisor application supplied on the CD-ROMaccompanying your Switch is the main tool for configuring QoS, and3Com recommends that you use this application to configure QoS.You can also configure QoS via the command line interface (CLI), for adetailed description of the commands that you require refer to theManagement Interface Reference Guide supplied in HTML format on theCD-ROM that accompanies your Switch.Configure Class of Service using 3Com Network Supervisor in thefollowing way:1 Apply Traffic classification First identify the types of traffic requiringspecial treatment. These types are defined in the QoS feature through thecreation of classifiers. The Switch supports two types of packet attributeson 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 eachclassifier should receive. Note that DSCP service levels will be setsomewhere else in the network and not in the Switch itself. Note alsothat 802.1D service levels are fixed and cannot be altered.3 Create Profiles The next step is to create a profile, which associatesclassifiers with service levels.4 Apply CoS profile After a CoS profile has been created, it can beassigned to the Port(s). When the profile is assigned to the port(s), theQoS configuration defined in the profile will immediately become active.How TrafficPrioritization WorksTraffic prioritization ensures that high priority data is forwarded throughthe Switch without being delayed by lower priority data. Trafficprioritization uses the eight traffic queues that are present in thehardware of the Switch to ensure that high priority traffic is forwarded ona different queue from lower priority traffic. High priority traffic is givenpreference over low priority traffic to ensure that the most critical trafficgets the highest level of service.The Switch employs three methods of classifying traffic for prioritization.Traffic classification is the means of identifying which applicationgenerated the traffic, so that a service level can be applied to it.The three supported methods for classifying traffic are: