15-441 Computer Networking ecture 22- Queue Management and QoS
15-441 Computer Networking Lecture 22 – Queue Management and QoS
Congestion Control Review What is congestion control? What is the principle of TCP?
2 Congestion Control Review • What is congestion control? • What is the principle of TCP?
Traffic and resource Management Resources statistically shared >Demand, (t)> Resource(t) Overload causes congestion packet delayed or dropped application performance suffer Local vs. network wide Transient vs persistent Challenge high resource utilization high application performance O
3 Traffic and Resource Management • Resources statistically shared • Overload causes congestion • packet delayed or dropped • application performance suffer • Local vs. network wide • Transient vs. persistent • Challenge • high resource utilization • high application performance
Resource Management Approaches > Demand, (t)>Resource(t) Increase resources install new links faster routers capacity planning provisioning traffic engineering happen at longer timescale Reduce or delay demand Reactive approach: encourage everyone to reduce or delay demand Reservation approach some requests will be rejected by the network
4 Resource Management Approaches • Increase resources • install new links, faster routers • capacity planning, provisioning, traffic engineering • happen at longer timescale • Reduce or delay demand • Reactive approach: encourage everyone to reduce or delay demand • Reservation approach: some requests will be rejected by the network
Congestion Control in Today' s Internet End-system-only solution(TCP) TCP dynamically estimates network state packet loss signals congestion TCP reduces transmission rate in presence of congestion routers play little role TCP F k edpac Capacit Control Planning Control Time scale RTT(ms) Months
5 Congestion Control in Today’s Internet • End-system-only solution (TCP) • dynamically estimates network state • packet loss signals congestion • reduces transmission rate in presence of congestion • routers play little role TCP TCP TCP Control Time scale Months Capacity Planning RTT (ms) Feedback Control