UCB Improvements in Core-Stateless Fair Queueing (CSFQ) Ling Huang U.C. Berkeley cml.me.berkeley.edu/~hlion

UCB Achievements Analyze the limitation of current approach Failure to work with congestion avoidance algorithm. Heavy dependence on the estimation algorithms Estimation has big deviation when many flows startup simultaneously and during bursty traffic. Achieve three improvements Achieving fair share when working with congestion avoidance algorithm. Application of high order Low-Pass-Filter (LPF) in flow arrival rate estimation. Application of control-theory in fair share estimation.

UCB Algorithm of CSFQ Edge routers put flow state in packet‘s header. Core routers estimate fair share and drop. incoming packets with probability of A flow should get bandwidth. Core router updates fair share  as follows: if (A > C)  new =  old * C / F else  new = max (r i ), where r i  active flows Combining fair share computation and probabilistic dropping to approximate fair queueing!

UCB Improv.1: CSFQ working with TCP Vegas CSFQ get fare share to incoming flows, but Not accurately approximate delay properties of Fair Queueing. Incompatible with congestion avoidance mechanisms. Fig 1. CSFQ work with TCP Reno Fig 2. CSFQ work with TCP Vegas

UCB Improv. 1: CSFQ working with TCP Vegas High priority queue in core router Flows whose rates are less than their fare share go into high priority queue and get service first. Restores fairness when work with TCP Vegas. Fig 3. CSFQ + Priority Queue Fig 4. CSFQ + Priority Queue work with TCP Reno work with TCP Vegas

UCB Improv. 2: LPF in arrival rate estimation Current Approach employ 1 st order Low-Pass-Filter: Better properties from 2 nd order Low-Pass-Filter: Fast response to burst traffic. Estimation result more smooth.

UCB Improv. 2: LPF in arrival rate estimation Fast response to burst traffic Input singal Output of 1st order LPF Output of 2nd order LPF Followings are the same Fig 5. Response to pulse signal

UCB Improv. 2: LPF in arrival rate estimation Rate estimation for arrival traffic Fig 6. Estimation of arrival rate for UDP(1Mbps) Fig 7. Estimation of arrival rate for TCP (0.5Mbps)

UCB Improv. 2: LPF in arrival rate estimation Results of 2 nd Low-Pass-Filter in CSFQ Service allocated to flows more fare. Fig 8. CSFQ + Priority Queue + 2 nd LPF Fig 9. CSFQ + Priority Queue + 2 nd LPF work with TCP Reno work with TCP Vegas

UCB Improv. 3: Applying control theory in CSFQ Picture: Traffic model faucet and Flow 1 Flow n Exponential Average Exponential Average Arrival Rate Arrival Rate Estimating accepting rate Packet Dropper Observer R C s Q 0 Q Fig 10. Architecture of CSFQ scheduling: the same model as that in a water reservation system R C s Q 0 Q

UCB Improv. 3: Applying control theory in CSFQ Dynamic equation: using queue occupancy information to compute arrival rate. R: the aggregate accepted traffic during one update interval. C s : the output link capacity. Q: the buffer occupancy at current time. Q 0 : equilibrium point that we want the buffer occupancy to be. R C s Q 0 Q

UCB Improv. 3: Applying control theory in CSFQ Use queue occupancy information to predict the next allowed accepting rate: flow and congestion control. Allocate the allowed accepting rate to the incoming flows, fair share is the unique solution of equation:

UCB Results Improv. 3: Applying control theory in CSFQ Fig 11. CSFQ + control theory Fig 12. CSFQ + control theory work with TCP work with TCP Reno

UCB Results (cont.) Improv. 3: Applying control theory in CSFQ Fig 13. CSFQ + control theory work with TCP Vega Possible reason: priority queue confusing control system with buffer length. Fig 14. Average throughput by a TCP sharing a link of capacity 10 Mbps with (n-1) UDP flows. ( Import from [Hoon-Tong’00] )

UCB Conclusion: control theory produce stable and robust system. Without the the estimation of aggregate arrival rate and accepted traffic. Compute fare share continuously. Exhibit good transient and steady behavior. Achieve high utilization. Improv. 3: Applying control theory in CSFQ

UCB Three improvements in CSFQ High priority helps CSFQ achieve fair share when working with congestion avoidance algorithm. High order Low-Pass-Filter (LPF) helps improve fair share rate. Control-theory produce robust and highly utilized system. CS268 is a productive class Paper review and lecture let me know every aspect of network. Class project help me go deep into algorithm of resource allocation and packet scheduling. Work hard, you get achievement! Summary

UCB CSFQ work with TCP Renog CSFQ + Priority Queue work with TCP Reno CSFQ + Priority Queue + 2 nd LPF CSFQ + control theory work with TCP Reno work with TCP Reno

UCB CSFQ work with TCP Vegas CSFQ + Priority Queue work with TCP Vegas CSFQ + Priority Queue + 2 nd LPF CSFQ + control theory work with TCP Vegas work with TCP Vegas