Introducing Queuing Implementations参考.ppt

Implement the DiffServ QoS Model Introducing Queuing Implementations Congestion and Queuing Speed Mismatch Aggregation Definition Queuing is designed to accommodate temporary congestion on an interface of a network device by storing excess packets in buffers until bandwidth becomes available.队列是一个拥塞临时储存空间, 其通过在网络设备接口上使用缓存存储过多的数据包直到带宽允许时再将其向外转发. Queuing is a congestion-management mechanism that allows you to control congestion on interfaces.队列作为一种拥塞管理机制其可以让你在接口上进行拥塞管制. Congestion and Queuing Queuing Algorithms First in, first out (FIFO)先进先出 Priority queuing (PQ)优先级队列 Round robin循环 Weighted round robin (WRR)加权循环 FIFO Priority Queuing Round Robin Uses multiple queues使用多队列 No prioritization无优先级 Dispatches one packet from each queue in each round:在每一次循环中处理一个队列的数据包: One packet from queue No. 1处理第一个队列中的一个数据包 One packet from queue No. 2处理第二个队列中的一个数据包 One packet from queue No. 3处理第三个队列中的一个数据包 Then repeat然后重复 Weighted Round Robin Weighted Round Robin (Cont.) Problem with WRR: Some implementations of WRR dispatch a configurable number of bytes (threshold) from each queue for each round—several packets can be sent in each turn.在每一个循环中WRR根据配置的字节数(门限值)去处理每个队列中的数据包—几个数据包可能每一次轮换中被发出. The router is allowed to send the entire packet even if the sum of all bytes is more than the threshold.路由器始终发送完整的数据包即使如果其字节数超过配置的门限值. Router Queuing Components Each physical interface has a hardware and a software queuing system.每一个物理接口都有硬件和软件的队列系统. Router Queuing Components (Cont.) The hardware queuing system always uses FIFO queuing.硬件队列系统始终使用FIFO队列. The software queuing system can be selected and configured depending on the platform and Cisco IOS version.软件列队的选择和配置依赖于Cisco IOS版本和硬件的平台. The Software Queue Generally, a full hardware queue indicates interface congestion, and software queuing is used to manage it.通常一个硬件队列显示接口的拥塞,同时软件队列用于管理拥塞. When a packet is being forwarded, the router will bypass the software queue if the hardware queue has space in it(no congestion).当一个数据包被