6.896 Summary and Speculations

1. 6.896 Summary and Speculations Hari Balakrishnan EECS & LCS MIT December 7,1998

2. Goals • Gain exposure to classic and recent papers in networking • Focus on protocols, architecture, applications • Not on link technologies or hardware • Learn how to do networking research; develop the ability to pick problems and critique research • Conduct networking research via term project (and homework questions)

3. Results • Studied about 50-odd papers across a wide-range of topics, in varying levels of detail • Focused on key contributions and ideas, not details; focused on methodology and key results • 17 different term projects • An impressive array of topics and excellent progress so far • Homework questions turned out being semi-research projects too!

4. What Did We Learn in 6.896? • Philosophy and Architecture • Methodology and Techniques • Congestion Control and Management • Data transport and end-to-end methods • Queue management • Routing • Unicast • Multicast • Fast router design • Mobility and Wireless

5. What Did We Learn in 6.896? (cont.) • Applications • HTTP; interactions between HTTP & TCP • Adaptive multicast applications • Re-thinking the Service Model • Integrated and differentiated services • Utilities, incentive structures, priorities • Reliable Multicast • Programmable Networks • Middleware (Web Caching & DNS) • Network Security (IPSec) • Experimental Performance Analysis

6. Philosophy and Architecture • Layering • Soft-state; fate-sharing • End-to-end argument • “Keep the interior simple” • ALF • IETF approach to standardization • “Rough consensus and working code”

7. Research Methodology • Theoretical analysis (e.g., Bolot delay paper) • Design (e.g, using simulation) • Implementation • Experimental analysis and evaluation • Deployment issues

8. End-to-end Congestion Management • Stability of AIMD schemes • Rate vs. window • DECBit scheme • TCP

9. Queue Management • Scheduling vs. buffer management • Fair queueing • RED • Recommendations to encourage end-to-end mechanisms

10. Unicast Routing • Distance-vector vs. link-state • Intra-domain protocols (RIP, OSPF) • Inter-domain protocols (EGP, BGP) • Landmark hierarchy

11. Multicast Routing • IGMP • DVMRP • CBT • PIM

12. High-Speed Routers • BBN 50 Gbps router • High-speed forwarding techniques

13. Mobility • Mobile IP • Routing • Weak authentication • Route optimization • Alternate approaches using… • Multicast • Naming (say, DNS or better)

14. Wireless Transport • Problems • Errors • Asymmetry • Small windows • Snoop protocol (handles errors)

15. Media-Access • CSMA/CA and 802.11 • “Listen-before-transmit” with exponential backoff • MACA and MACAW • RTS/CTS/DS/DATA/ACK • Scalable channel access • Scheduling • Minimum-energy routing

16. HTTP • Simple object download protocol • Multiple objects concurrent through concurrent connections • Interacts badly with TCP congestion mechanisms • Persistent connections and pipelining (HTTP/1.1) • Not the best solution!

17. Multicast Video • IVS: Scalable feedback based on random sliding key scheme • RLM: Layered video plus adaptive join/leave control mechanism

18. Integrated and Differentiated Services • More than just best-effort • Reservation mechanisms (ISPN) • RSVP • Diff-serv models • Two-bit scheme with bandwidth broker • Assured service

19. Utilities and Incentives • Utility vs. rate (or delay) curves • Framework for arguing about right service model • And arguing about admission control • Elastic vs. inelastic apps • Analysis for layered video and priority-drop gateways

20. Reliable Multicast • Key problem: message implosion • RMTP (designated receivers) • SRM (random damping + suppression and ALF) • Digital fountain (no feedback, good FEC) • Replier-based scheme (router support for local recovery)

21. Programmable Networks • Eases deployment of new services • Active networks • General-purpose programmability • Capsules • Switchware • Active services

22. Web Caching • Ease load on servers and network, improve latency • HTTP/1.1 support • Harvest • ICP • Summary Cache • Adaptive Web Caching • Cisco CacheDirector

23. Naming • DNS • Future efforts • Active names • Intentional names

24. Network Security • IPSec • Intrusion detection • Public key infrastructure • Multicast key management

25. Performance Analysis • Self-similarity and LRD • Synchronization of weakly-coupled independent periodic processes • End-to-end Internet dynamics • SPAND: Shared and passive network performance

26. A Sample of the Future • Change caused by link technology, applications, scale, heterogeneity, pervasiveness • Architecture & service model • Technological advances • Enormous diversity of wireless and wired links • Satellite networks (poised to make a big splash!) • Ubiquity • Embedded devices • Sensors & actuators • Interactions with the world around us (“deeply networked systems”)

27. Futures (cont.) • Naming and Location • Of objects, services, software, people, nodes, … • E.g, Active naming; intentional naming • Application-level routing • Adaptation (protocols and apps) • Congestion, load, errors, variability, mobility • Self-configuration and self-organization • “Spontaneous networks” • Programmability • Active nodes (in some form) almost certain

28. Futures (cont.) • Novel services • E.g., telephony, telepresence, graphics apps, games • Security • Economic structure • Physics • Understanding the “physics” of networking and large-scale systems (like the Internet) • A global measurement and analysis infrastructure