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Introduction 1.1.1. Scope This manual provides configuration information for new software features found in V1.20 of the 3Com Router operating system. Use this addendum to supplement configuration information found in the 3Com Router Configuration Guide. 1.1.2. Online Resources Download the Router 3000 Installation Guide from: Download the Router 5000 Installation Guide from: Download the 3Com Router Command Reference Guide from: Download the 3Com Router Configuration Guide from: Download other current software updates and release notes from: Chapter 1 Configuring Class-Based Queuing As an extension of WFQ, class based queuing (CBQ) provides users with class definition support. CBQ assigns individual FIFO reservation queues to the classes defined by each user to buffer data of the same class. When there is network congestion, CBQ matches outbound packets according to the classification rule defined by users to make them enter relevant queues. Before queue entry of packets, the congestion avoidance mechanism (tail-drop or weighted random early detection [WRED]) and bandwidth limit must first be checked. When packets leave the queues, weighted fair scheduling of packets in the queues corresponding to each class should be performed. Figure 1-1 CBQ diagram If CBQ performs weighted fair treatment to queues of all classes, voice packets, the delay-sensitive data flow may not be sent out in time. Therefore, PQ is introduced to CBQ to create low latency queuing (LLQ), which provides strictly preferred sending service for such delay-sensitive data flow as voice packets. LLQ strictly combines PQ with CBQ. When a user defines a class, he can specify it to accept strict priority service. The class of this type is called priority class. All packets of the priority class enter the same priority queue. Before they enter a queue, the bandwidth limit of each class of packets should be checked. When packets go out of the queues, the packets in the priority queue are forwarded before packets in the queues corresponding to other classes. But if the maximum reservation bandwidth configured for LLQ is exceeded, the packets in other queue are sent. Weighted fair scheduling will be performed to the packets in other queues when they are forwarded. In order to avoid long time delay of packets in other queues, the maximum available bandwidth can be specified for each priority class during LLQ application for traffic policing upon congestion. If no congestion occurs, the priority class is permitted to use bandwidth exceeding the assigned value. In case of congestion, packets exceeding the assigned bandwidth of the priority class will be discarded. Burst size is also configurable under LLQ. When the system matches packets with rules, it matches priority classes before other classes. If there are multiple priority classes, they are matched one by one according to configuration sequence. The same procedure is used to match packets and rules in other classes. If there are multiple rules in a class, they are also matched one by one according to the configuration sequence. 1.2 CBQ Configuration Tasks CBQ (Class Based Queuing) configuration includes: .. Define a class and enter the class view .. Configure matching rules of a class .. Define the policy and enter the policy view .. Configure class in policy and enter policy-class view .. Configure features of a class .. Apply a policy to an interface 1.2.1 Define a Class and Enter the Class View Defines a class and enters class view. Perform the following configurations in the system view. Table 1-1 Define a class and enter the class view Operation Command Define a Class and Enter the Class View qos class [ logic-and | logic-or ] class-name Delete a class and enter class view undo qos class [ logic-and | logic-or ] class-name By default, a class named default-class is defined in the system. The class name defined by the user “class-name” cannot be default-class. By default, the defined class is logic-and and the interrelationship between matching rules in the class view is logical AND. 1.2.2 Configure Matching Rules of a Class 1) Define the rule for matching all packets Perform the following configurations in class view. Table 1-2 Define/delete the rule matching all packets Operation Command Define the rule matching all packets if-match [logic-not ] any Delete the rule matching all packets undo if-match [logic- not ] any 2) Define the class matching rule Perform the following configurations in class view. Table 1-3 Define/delete the class matching rule Operation Command Define the class matching rule if-match [ logic-not ] class class-name Delete the class matching rule undo if-match [ logic-not ] class cla...