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Network Architecture (R02) - L2

Network Architecture (R02) - L2. Jon Crowcroft, http://www.cl.cam.ac.uk/~jac22 http://www.cl.cam.ac.uk/teaching/1213/R02/. Polyglot Networking. There was a time before the Internet A long, long, long time ago… … … There were other protocol architectures too (gasp!) ISO, CCITT

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Network Architecture (R02) - L2

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  1. Network Architecture (R02) - L2 Jon Crowcroft, http://www.cl.cam.ac.uk/~jac22 http://www.cl.cam.ac.uk/teaching/1213/R02/

  2. Polyglot Networking • There was a time before the Internet • A long, long, long time ago… … … • There were other protocol architectures too (gasp!) • ISO, CCITT • DECNET, XNS, SNA • CR82, Color Book • How to Interconnect?

  3. Interworking different arch • Application Layer Relay • Transport Service Relay • Protocol Translator • Other? • Future Nets • Internet of Things (e.g. sensors) • Space Networks

  4. Delay Tolerant Networking • Interplanetary Networking • Delays (hours!) • Disruption (solar flares!) • Disconnections (eclipse!) • What would “network” look like?

  5. DTN • Store, Carry, Forward • Like an Email Net • Also like UUCP (Usenet) • Custodians • Routing • Predictable/Schedule (bus, train, spaceship, satellite) • Random? • Errors? FEC, Redundency?

  6. For next week oct 22 • You talk about • ipmc (Ghao Gao) • pgm (Natacha Crooks) • All of you start to read/write about one of • I3, IPNL, ROFL or ILNP • See http://www.cl.cam.ac.uk/teaching/1213/R02/papers/ http://www.cl.cam.ac.uk/teaching/1213/R02/essays/essay0.txt

  7. Multicast - Classic • Make the Internet one big Ethernet • Steve Deering (w/ Dave Cheriton) 1988 • New address (“Class D”) = Host Group, G • Forwarding Scheme = away from S • Prune/Graft per interface “towards” G • Need (S,G) state, Per Router… • State Management…

  8. Group State Management • Implicit • Traffic Driven • Explicit • IGMP Driven • More Overheads! • So not only state overhead is S*G • But also control overhead O(G) messages • Aggregation probably doesn’t do much • Any Source v. Source Specific v. Single

  9. Single Source • Can use reverse path fwd only • Can auth/check source • (exactly same as Best Practice RPF check) • Not much use for many-to-many apps? • N.b. looking at main early use of multicast (“mbone”) - • was many-to-many video conf • main use now? IPTV, Radio, S/W

  10. Reliable Multicast • Seems to be no “one size fits all” • Nack, Ack Aggr & Code based schemes • Need various ordering semantics (if n-m) • Interesting e.g. of new style WG in standards • Did “building blocks” • Then composed RM protocols from these • One v. interesting idea - GRA • minimal router processing engine needed for e2e protocol support • Precursor of other middle box ideas…

  11. RM - Congestion Control & Failures • Two things hard to define • How should multicast flow “compete” with TCP? • What are the “late join”, “early leave” and “fail” semantics for some members? • Again, no “one size fits all” answer…

  12. The “Truth” about Multicast • In fact, in a conference in 2006 • Berkeley Sys Admins reported that • Turning on IP multicast broke Unicast! • Classic deployment dilemma • Specially Bad Case • Multicast has to be in “fast path” • Multicast routing depends closely on Unicast (viz PIM) • It also depended on monitoring data to drive routing update • So new control plane interface to fast path :-(

  13. For next week - oct 22 • 2 of you talk about • Deployment Issues for IP Multicast & • Pragmatic Generalized Multicast • All of you read the two papers • See http://www.cl.cam.ac.uk/teaching/1213/R02/papers/ Don’t forget…for nov 2 http://www.cl.cam.ac.uk/teaching/1213/R02/essays/essay0.txt

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