13-交换数据网的拥塞控制

1、chapter 13 Congestion in data networks数据网络中的拥塞、PRESENTED BY YONGMIN QI(qiyong min QI)、Overview，13.1 Effects of Congestion拥塞的影响13 congestion occurs when the number of packets being transmitted through the network approaches the packet handling capacity of the network congent of the network congent pa

2、ckets arriving are stored at input buffers routing decision made packet moves to output buffer if packets arrive to fast to be routed，Or to be outed ，吞吐量：网络传递到目标系统的组数。延迟，Practical Performance，Ideal assumes infinite buffers and no overhead to packet transmission or congestion Control buffers are fini

3、te严重拥塞：吞吐量下降。网络已禁用死锁，网络负载，吞吐量，0，拥塞控制角色，13.2 congestion control，backpressure反压，If node becomes congestedE.g. ICMP source quench源点抑制组from router Or destination source cuts back until no more source quench message源点抑制消息sent for every discarded pap Or Antinguse fulon connection less(datagram)networks、ex

4、plicit congestion signaling显式拥塞信号、Network alerts end systems of increasing connetworksforwards forwards forwards forward forward congestion avoidance in same direction as packet required，categories of explicit signaliesFairness公平Quality of service QoS may want different treatment for different connections reservations保留e . g . ATM traffic contract between un Worksend control packet to some or all source nodes requires additional traffic during congestion rely on routing informa