Korea Advanced Institute of Science and Technology Network Systems Lab. 1 Dual-resource TCP/AQM for processing-constrained networks INFOCOM 2006, Barcelona, Apr. 25, 2006 Minsu Shin and Song Chong Department of EECS, KAIST, Korea Injong Rhee Department of CS, NC State Univ., USA

Network Systems Lab. 2 Outline Motivation Processing-constrained network Dual-resource environment Objective Dual-resource fair allocation Dual-resource TCP/AQM (DRQ) DRQ objective DRQ implementation Simulation results Conclusion

Network Systems Lab. 3 Processing-constrained network Link bandwidth grows fast Advancement in optical network technology Over-provisioning as the solution to congestion The rise of in-network applications IP forwarding Packet classification and filtering Network address translation Web-switching VPN & IPSec Data Transcoding Duplicate data suppression Firewall Complexity increases Traditional network Future network Virus detection

Network Systems Lab. 4 Dual-resource environment Both bandwidth and CPU can be a bottleneck Can existing congestion control (TCP) be applied? CPU Switch User Malicious user Congestion What is fair and efficient resource allocation?

Network Systems Lab. 5 Objective To propose a dual-resource fairness criteria Extend the proportional fairness to the dual- resource environment Provide fair and efficient resource usages To propose a dual-resource queue (DRQ) Active queue management (AQM) strategy Approximate dual-resource fairness for TCP sources Scalable : Not maintaining per-flow states or queues Incrementally deployable : No changes in TCP stacks

Network Systems Lab. 6 Single-resource fairness Only considering link bandwidth constraint Assume that network consists of L links Maximization problem rate r 1 Tx Output Link B l (Mbps) rate r S maximum throughput proportional fair max-min fair Selection of [Mo 00] [Low 99]

Network Systems Lab. 7 Dual-resource fairness Considering both CPU and bandwidth constraint Network consists of L links and K CPUs TxCPU Output Link C (cycles/sec) B (Mbps) rate r 1 rate r S Maximization problem : processing density Indicating required CPU cycles per bit Proportional fairness is weight of flow s Selection of

Network Systems Lab. 8 Performance Single link case Dual-resource fair allocationSingle-resource fair allocation TxCPU Output Link C (cycles/sec) B (Mbps) rate r 1 rate r 4 w = [1, 2, 4, 8] 40% utilization increases CPU fair share

Network Systems Lab. 9 Dual-resource fair rate Congestion price of resources CPU price : θ, Link price : π Increasing : demand > resource capacity Decreasing : demand < resource capacity Positive when the resource becomes a bottleneck Zero when not a bottleneck Fair rate Inversely proportional to the aggregate price Weighted CPU price sumLink price sum

Network Systems Lab. 10 Dual-resource TCP/AQM Extend dual-resource fairness to TCP network DRQ modifies RED algorithm Tx B 1 (Mbps) C 2 (cycles/s) Tx B 3 (Mbps) p2p2 Packet drop with probability p 1 p3p3 CPU TCP Sender ( w ) TCP receiver TCP Sending rate ≈ α Current TCP/AQM TCP Sending rate ≈ α Our Goal

Network Systems Lab. 11 DRQ algorithm Tx B 1 (Mbps) C 2 (cycles/s) Tx B 3 (Mbps) p2p2 packet drop with probability p 1 p3p3 CPU TCP Sending rate ≈ α Our Goal Each resource drops packet with p 2 (link), or (wp) 2 (CPU) Communication between resources is needed TCP Sender ( w ) TCP receiver

Network Systems Lab. 12 DRQ algorithm At link 1, mark packet with prob. At CPU 2, mark packet with prob. At link 3, mark packet with prob. If already marked, then drop packet! (link), or (CPU) : Intra-marking probability (link), or (CPU) : Inter-marking probability No explicit communication between resources! Red card! Yellow card!

Network Systems Lab. 13 DRQ-ECN implementation Three ECN cases ECN = 00 : Initial state ECN = 10 : Signaling-marked (No congestion notification) ECN = 11 : Congestion-marked (TCP source decreases its window size by half) DRQ’s ECN marking algorithm When a packet arrives if(ECN ≠ 11) set ECN to 11 with red-card probability if(ECN == 00) set ECN to 10 with yellow-card probability if(ECN == 10) set ECN to 11 with yellow-card probability

Network Systems Lab. 14 Performance evaluation Comparison partners RED-RED : CPU and link queues use original RED Very cheap. Most of current network system architecture DRR-RED : Scheduling CPU using per-flow queue Expensive approach. Similar architecture to current computing system TxCPU Output Link C (cycles/sec) B (Mbps) RED TxCPU Output Link C (cycles/sec) B (Mbps) RED DRR DRQ’s complexity : RED-RED but, DRQ’s performance : DRR-RED

Network Systems Lab. 15 Single CPU and link case Topology DRQ In DRQ, each follows fair rates. 40 TCP sources, which require different processing (0.25, 0.50, 1.00, 2.00) Varying CPU capacity Average throughput of each source

Network Systems Lab. 16 Single CPU and link case Comparison of bandwidth utilization RED-RED has much lower bandwidth utilization DRQ performance is comparable to DRR-RED Efficiency improves !

Network Systems Lab. 17 Impact of high processing flows Insert a few high processing flows (w=10.0) DRQ and DRR-RED prevent their domination but RED-RED doesn’t Prevent CPU domination!Increase total throughput

Network Systems Lab. 18 Multiple-link simulation(1) Throughput of TCP/DRQ in multiple link simulations Parking-lot topology, with various cross- traffic DRQ follows theoretic fair rates very well.

Network Systems Lab. 19 Partial deployment Network edge Pushing complicated tasks to the edge of Internet DRQ can be initially deployed to the edge system Simulation topology DRQ is implemented at only IE1 and EE1 Source groups SG1 : High processing SG2 : low processing Others : Negligible processing

Network Systems Lab. 20 Partial deployment Throughput of processing-constrained edge Increase throughput of IE1 Partial deployment is also beneficial to improve efficiency

Network Systems Lab. 21 Conclusion Contribution of this paper Finding an efficient and fair allocation policy in the dual-resource environment Suggestion of the practical implementation guideline

Network Systems Lab. 22 References [Kelly 98] “Rate control in communication networks: shadow prices, proportional fairness and stability", J. of the Operational Research Society, 1998 [Mo 00] “Fair end-to-end window-based congestion control", IEEE/ACM TON 2000 [Wolf 00] “Commbench – a telecommunications benchmark for network processors", ISPASS 2000 [Low 99] “Optimization flow control I : Basic algorithm and convergence", IEEE/ACM TON 1999 [Floyd 93] “Random early detection gateways for congestion avoidance", IEEE/ACM TON 1993 [Low 03] “A duality model of TCP and queue management algorithms", IEEE/ACM TON 2003 [Pappu 02] “Scheduling processing resources in programmable routers”, IEEE INFOCOM 2002