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15-441: Computer Networking

15-441: Computer Networking. Lecture 26: Networking Future. Overview. Learning From Failures Changes in Various Layers New Services What Do I Work On?. Learning From Failures. Past failures Multicast QoS MobileIP. Why Did They Fail?. Scalability problems Incremental deployment

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15-441: Computer Networking

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  1. 15-441: Computer Networking Lecture 26: Networking Future

  2. Overview • Learning From Failures • Changes in Various Layers • New Services • What Do I Work On? Lecture 26: 12-06-01

  3. Learning From Failures • Past failures • Multicast • QoS • MobileIP Lecture 26: 12-06-01

  4. Why Did They Fail? • Scalability problems • Incremental deployment • Interfacing with applications/Building useful services • Debugging problems • Conservative network administrators Lecture 26: 12-06-01

  5. What Can We Learn? • Avoid same pitfalls • Clever techniques • Fair queuing, announce/suppress protocols, tunneling/encapsulation, etc. Lecture 26: 12-06-01

  6. Overview • Learning From Failures • Changes in Various Layers • New Services • What Do I Work On? Lecture 26: 12-06-01

  7. Link Layer • Optical links • Multiple wavelengths on a single fiber (WDM) • MPLS applied to wavelengths  MPλS • No longer broadcast • All optical networks • No buffering!!  How does this affect other protocols • Mobile/wireless links Lecture 26: 12-06-01

  8. Overlay Routing • Basic idea: • Treat multiple hops through IP network as one hop in overlay network • Run routing protocol on overlay nodes • Why? • For performance – can run more clever protocol on overlay • For efficiency – can make core routers very simple • For functionality – can provide new features such as multicast, active processing, IPv6 Lecture 26: 12-06-01

  9. IP Multicast Gatech Stanford CMU Berkeley Key Architectural Decision: Add support for multicast in IP layer Lecture 26: 12-06-01

  10. Overlay Multicast CMU Gatech Stan-LAN Stanford Stan-Modem Berk1 Berkeley Berk2 Overlay Tree Stan-LAN Gatech Stan-Modem CMU Berk1 Lecture 26: 12-06-01 Berk2

  11. Overlay Challenges • “Routers” no longer have complete knowledge about link they are responsible for • How do you build efficient overlay • Probably don’t want all N2 links – which links to create? • Without direct knowledge of underlying topology how to know what’s nearby and what is efficient? Lecture 26: 12-06-01

  12. Congestion Control • Is AIMD the right choice for everyone? • What are the requirements on choices  TCP-friendliness • Non-linear controls • Rate-based controls • Fixing poor interaction with HTTP Lecture 26: 12-06-01

  13. Denial of Service • Objective of attack: make a service unusable, usually by overloading the server or network • Example: SYN flooding attack • Send SYN packets with bogus source address • Server responds with SYNACK keeps state about TCP half-open connection • Eventually server memory is exhausted with this state • Solution: SYN cookies – make the SYNACK contents purely a function of SYN contents, therefore, it can be recomputed on reception of next ACK • More recent attacks have used bandwidth floods • How do we stop these? Lecture 26: 12-06-01

  14. Bandwidth DoS Attacks • Possible solutions • Ingress filtering – examine packets to identify bogus source addresses • Link testing – how routers either explicitly identify which hops are involved in attack or use controlled flooding and a network map to perturb attack traffic • Logging – log packets at key routers and post-process to identify attacker’s path • ICMP traceback – sample occasional packets and copy path info into special ICMP messages • IP traceback Lecture 26: 12-06-01

  15. Overview • Learning From Failures • Changes in Various Layers • New Services • What Do I Work On? Lecture 26: 12-06-01

  16. Network Location Service • Desirable to lookup performance between hosts • Why? • How to predict? • Based on historical measurements • Based on on-demand probing • What exactly is performance? • Bandwidth • Delay • Application response Lecture 26: 12-06-01

  17. Services For Mobile Users • Why? • (Example) Mobile users are more likely to search for services near them • Not well suited to administratively organized Internet systems • Example • Build a wide area service discovery that can support multiple search styles Lecture 26: 12-06-01

  18. Overview • Learning From Failures • Changes in Various Layers • New Services • What Do I Work On? Lecture 26: 12-06-01

  19. Three Project Areas • Congestion Control • Solving interaction between HTTP and TCP • Using congestion control to implement QoS • Mobile Networking • Making protocols adapt to dynamic conditions • Helping “ubiquitous” networks evolve • Sensor networks • Wide-Area Distributed Applications • Tools to help developers build large distributed applications • Overlay multicast Lecture 26: 12-06-01

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