Netgear XCM8806 Chassis User Manual - Page 368

NETGEAR 8800 User Manual • Ingress QoS profiles (hardware queues) • Ingress traffic queues (software queues) • Egress traffic queues • Egress QoS profiles • Egress ports The CIR or minimum bandwidth configuration for a rate-limiting or rate-shaping component is a bandwidth guarantee for that component at a particular location in the traffic path. The guarantees for all components at a specified location should add up to less than 100% and should account for the traffic needs of the other components. For example, if you configure 25% minimum bandwidth for four out of eight queues at a particular location, there will be no available bandwidth for the remaining four queues when traffic exceeds the port capacity. Bandwidth unused by a queue can be used by other queues. The rate-shaping configuration is configured at the location to which it applies on most platforms. Meters are also used to provide ingress rate shaping on NETGEAR 8800 switches. Disabling Rate Limiting and Rate Shaping All switch platforms provide multiple QoS components in the traffic path that provide rate limiting or rate shaping. These components give you control over where and how the rate shaping is applied. However, your application might not require rate shaping at every component. The default configuration for most components provides no rate shaping. When rate shaping is disabled on a component, the CIR is set to 0 (minbw=0%) and the PR is set to the maximum bandwidth (maxbw=100%). This setting reserves no bandwidth for the component and allows the component to use 100% of the port bandwidth. If you need to remove rate shaping from a QoS component, configure these settings on that component. Scheduling Scheduling is the process that determines which traffic is forwarded when multiple QoS components are competing for egress bandwidth. The XCM8800 software supports the following scheduling methods: • Strict priority queuing: All higher priority queues are serviced before lower priority queues. This ensures that high priority traffic receives access to available network bandwidth immediately, but can result in lower priority traffic being starved. As long as a queued packet remains in a higher-priority queue, any lower-priority queues are not serviced. • Weighted fair queuing: All queues are given access to a relative amount of bandwidth based on the weight assigned to the queue. When you configure a QoS profile with a weight of 4, that queue is serviced four times as frequently as a queue with a weight of 1. The hardware services higher-weighted queues more frequently, but lower-weighted queues continue to be serviced at all times. Initially, the weight for all queues is set to 1, which gives them equal weight. If all queues are set to 4, for example, all queues still have equal weight, but each queue is serviced for a longer period. • Round-robin priority: All queues are given access based on the configured priority level and a round-robin algorithm. 368 | Chapter 15. QoS