Dell PowerConnect J-8216 Software Guide for JUNOS version 10.3 - Page 2946

Dell PowerConnect J-Series Ethernet Switch Complete Software Guide for Junos OS classes if they receive a larger amount of offered load than their allocated bandwidth allows. Transmission Rate The transmission-rate control determines the actual traffic bandwidth from each forwarding class you configure. The rate is specified in bits per second. Each queue is allocated some portion of the bandwidth of the outgoing interface. This bandwidth amount can be a fixed value, such as 1 megabit per second (Mbps), a percentage of the total available bandwidth, or the rest of the available bandwidth. You can allow transmission bandwidth to exceed the configured rate if additional bandwidth is available from other queues. In case of congestion, configured amount of transmission rate is guaranteed for the queue. This property allows you to ensure that each queue receives the amount of bandwidth appropriate to its level of service. Scheduler Buffer Size To control congestion at the output stage, you can configure the delay-buffer bandwidth. The delay-buffer bandwidth provides packet buffer space to absorb burst traffic up to the specified duration of delay. Once the specified delay buffer becomes full, packets with 100 percent drop probability are dropped from the tail of the buffer. The default scheduler transmission rate for queues 0 through 7 are 95, 0, 0, 0, 0, 0, 0, and 5 percent of the total available bandwidth. The default buffer-size percentages for queues 0 through 7 are 95, 0, 0, 0, 0, 0, 0, and 5 percent of the total available buffer. NOTE: On J-EX8200 switches, the default scheduler transmission rates for queues 0 through 7 are 75, 0, 20, 0, 0, 0, 0, and 5 percent of the total available bandwidth. The default buffer-size percentages for queues 0 through 7 are 75, 0, 20, 0, 0, 0, 0, and 5 percent of the total available buffer. For each scheduler, you can configure the buffer size as one of the following: • A percentage of the total buffer. • The remaining buffer available. The remainder is the buffer percentage that is not assigned to other queues. For example, if you assign 40 percent of the delay buffer to queue 0, allow queue 2 to keep the default allotment of 20 percent, allow queue 7 to keep the default allotment of 5 percent, and assign the remainder to queue 3, then queue 3 uses approximately 35 percent of the delay buffer. Priority Scheduling Priority scheduling determines the order in which an output interface transmits traffic from the queues, thus ensuring that queues containing important traffic are provided better access to the outgoing interface. Priority scheduling is accomplished through a procedure in which the scheduler examines the priority of the queue. The Junos OS supports two levels of transmission priority: 2874