EECS 228a – Review

1. EECS 228a – Review Jean Walrand www.eecs.berkeley.edu/~wlr Fall 2002

2. Topics • Overview • Economics of Networks • Games • Mechanism Design • Routing • Congestion Control • Traffic Models

3. Overview • Big Picture: Peering Core Backbone Users Access Regional Metro Enterprise Campus

4. Overview • Routing: • Slow convergence of BGP after failure • No load awareness of OSPF and BGP • No QoS • Peer-to-peer and other new applications • Congestion Control: • TCP is poor for large bandwidth-delay product • Large queues and retransmissions • Poor for wireless • Unfair, large jitter, …

5. Overview (cont) • Economics: • How to make money with this technology? • Market and service differentiation? • Pricing links, services • Traffic Models: • LRD – Does it matter?

6. Economics Games Analysis Design VCG Non-cooperative Cooperative Nash Bargaining Eq. Shapley Value Static Stackelberg Repeated • Nash Equilibrium • Existence • Uniqueness • Convergence • Calculation Folk Theorem Prisoners’ Dilemma Matching Pennies Cournot

7. Economics Papers • R.B. Rosen. “Existence and Uniqueness of Equilibrium Points for Concave N-Person Games.” Econometrica, vol. 33, 1965. Convex games  Existence of Nash Equilibrium Suff. Condition for uniqueness (SDD)Technique: KT conditions 2. Orda, R. Rom, and N. Shimkin. “Competitive Routing in Multiuser Communication Networks,” IEEE/ACM Trans on Networking, Vol. 1, pp. 510-521, October 1993. Users choose among parallel links • Existence, uniqueness, properties of Nash Equilibrium 3. Y. A. Korilis, A. Lazar, and A. Orda. “Achieving Network Optima Using Stackelberg Routing Strategies,” IEEE/ACM Transactions on Networking, Vol. 5, No. 1, February 1997, pp. 161-173. Network manager controls some of the flow and drives the Nash equilibrium to a socially efficient equilibrium

8. Economics Papers 4. S. Shenker. "Making Greedy Work in Networks: A Game-Theoretic Analysis of Switch Service Disciplines," IEEE/ACM Trans on Networking, vol. 3, No. 6, Dec. 1995. Exponential server shared by different queues. Explores impact of service discipline on equilibrium point (users adjust their rate).  FCFS is not efficient; Fair share is. 5. Z. Dziong and L.G. Mason. “Fair–Efficient Call Admission Control Policies for Broadband Networks – a Game Theoretic Framework,” IEEE/ACM Trans. On Networking, vol.4, Feb. 1996. Admission control as a cooperative game. Compare different notions of cooperative equilibrium. • Trunk reservation and dynamic reservations approach optimal.

9. Economics Papers 6. Allan Gibbard, “Manipulation of Voting Schemes: A General Result.” Econometrica, 41(4):587-601, Jul. 1973. Any nondictatorial voting scheme with at least three possible outcomes is subject to individual manipulation. (One voter getting a preferable outcome to the honest one by misrepresenting his preferences.) 7. Roger Myerson, “Incentive Compatibility and the Bargaining Problem.” Econometrica, 47:61-73, 1979 Study of set of feasible expected utility allocations under incentive-compatible mechanisms. • Set is compact and convex and includes those achievable by other mechanisms. 8.Roger Myerson, “Optimal Auction Design.” Mathematics of Operations Research, 6:58-73, 1981 • Revelation Principle • Revenue Equivalence Theorem

10. Economics Papers 9. Wiliam Vickery, “Counterspeculation, Auctions, and Competitive Sealed Tenders,” Journal of Finance, 16(1):8-37, Mar.1961  (Highest bidder; 2nd highest price) is incentive-compatible

11. Routing • Abhay Parekh

12. Congestion Control • Objectives: • Efficiency • Fairness • Key observations: • Fairness is in the eye of the users • Delay x Gain < K for stability • Clever trick: virtual queue

13. Congestion Control • Primal/Dual: • Max. sum of utilities s.t. capacity constraints • Minimize sum of max. profits • Implementation: • Variation on Vegas • Note: Simple TCP models

14. Congestion Control - Papers • V. Misra, W. Gong and D. Towsley. Stochastic Differential Equation Modeling and Analysis of TCP Window Size Behavior, Proceedings of Performance'99, October 1999. Loss rate = f(packet rate); Packet rate = f(loss rate) • Solve fixed point 2. G. de Veciana, T.-J. Lee and T. Konstantopoulos.Stability and Performance of Networks Supporting Rate Control. Could the Internet be Unstable?In Proc. IEEE INFOCOM , 1999. Network load increases -> service rate decreases • Stability conditions 3. Chiu and R. Jain, Analysis of the Increase and Decrease Algorithms for Congestion Avoidance in Computer Networks, Journal of Computer Networks and ISDN, Vol. 17, No. 1, June 1989, pp. 1-14. AIMD should converge to fair efficient equilibrium 4. Frank Kelly, A.K. Maulloo and D.K.H. Tan, Rate control in communication networks: shadow prices, proportional fairness and stability, Journal of the Operational Research Society 49 (1998), 237-252. Primal/Dual; Implementation of dual with router indications (WPF)

15. Congestion Control - Papers 5. S. Low and D. Lapsley. Optimization Flow Control, I: Basic Algorithm and Convergence, IEEE/ACM Trans on Networking, December 1999. Generalize Primal/Dual; Study of stability with delays. 6. S. Kunniyur and R. Srikant.End-to-end congestion control: utility functions, random losses and ECN marks, Infocom 2000. Virtual queue for AQM; Adjust rate of VQ to increase utilization. 7. J. Mo and J. Walrand, Fair End-to-End Window-based Congestion Control, September 1998. • max-min is a form of WPF • Variation on Vegas solves dual 8. C. Hollot, V. Misra, D. Towsley and W. Gong. A Control Theoretic Analysis of RED, INFOCOMM 2001 Linearize RED dynamics. Show stability if gain x delay < K.

16. Traffic Models • Markov  Exp. Tails • LRD • Important fact: Close loop systemThus model should be - User Activity Behavior - File Size Distribution

17. Current Research in our Group • Smart Networks: • Real-time Network management • Wireless Ad Hoc • E2E CAC • Routing • Games: • P2P • Access Price • Adjustment of SLAs