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A Brief History of Multicast

2. 20 years in the doldrums. IP Multicast arrived way way too soon, in 1988Remember, 1988 was the year TCP congestion control was first deployedThe NSFNet had not been deconstructed, and was still the

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A Brief History of Multicast

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    1. A Brief History of Multicast Jon Crowcroft (University of Cambridge)

    2. 2 20 years in the doldrums IP Multicast arrived way way too soon, in 1988 Remember, 1988 was the year TCP congestion control was first deployed The NSFNet had not been deconstructed, and was still the core - traffic between european countries went via it in the US Most non academic users were on 56kbps dial up at best There was no WWW. No URLs, No HTTP, no HTML, no XML There was no P2P, facebook, myspace, Halo, secondlife Steve Deering was just far too clever for us 23 July 2007 Microsoft

    3. 3 The Killer App To make matters worse, we also built the killer app 20 years too soon Vic, Vat, IVS, RAT, Wb, Mbone family of real-time multimedia tools that worked rather well assumed all users on 10Mbps untrammelled internet access, and overprovisioned core Some ISPs immediately banned all non DNS UDP traffic Worse was to be discovered - unintended DDoS Anyone could join any/all group, despite not having enough downlink speed Anyone could setup groups Group management wasnt (managed) 23 July 2007 Microsoft

    4. 4 Go Native? Leave comfort of home? First deployment of IP multicast was an overlay of IP tunnels (mrouted/dvmrp) Actually, predating this, we tried loose source routing, but broke all the cisco kit out there for unicast (documented in NANOG) - fixed by IP in IP tunnels, and throw away the MTU overhead Then when cisco deployed PIM, they broke their _own_ unicast (publically documented by berkeley at SIGCOMM a few years ago) And no-one could figure out inter-domain 23 July 2007 Microsoft

    5. 5 Plan B: Reliable Multicast? So in early 1990s, community tried 2nd wave killer app:- Content Distribution via reliable multicast RMTP, PGM, Digital Fountain plethora of techniques All work pretty well in fact But all depend on IP multicast deployment which was stil waiting for Cisco to hire Isidor Kouvelas to fix Dinos code:-) Meanwhile, web cache acceleration seemed to be the thing Akamai, Inktomi, and some small inkling of googles to come, altavista, scaled up data center Optical backbone meant capacity fine so repeated unicast not regarded as insane the way it was in 1980s Where was a poor multicaster going to earn a crust? 23 July 2007 Microsoft

    6. 6 Post hoc rationalisation of failure Diot et al wrote a long diatribe which was well received explaining why IP multicast would never be deployed Somehow, the reviewers failed to spot that the same explanations would have meant IP unicast was never deloyed:-) Lack of security Lack of prevention of DDoS Lack of pricing model Lack of killer app .see where I am heading? 23 July 2007 Microsoft

    7. 7 So now we have IP TV And we have DSL access (yes 6Mbps> original Ethernet:) And we have tiny 100$ machines that can do video And not even the massive data center and optical capacity can run 1M TV live channels So multicast to the rescue!!! Of course, we also have IGMPv3, source specific multicast, and a bunch of overlays that allowed us to evolve a business model for CDNs, to be fair:-) 23 July 2007 Microsoft

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