A Brief History of Multicast Jon Crowcroft (University of Cambridge)
20 years in the doldrums <ul><li>IP Multicast arrived way way too soon, in 1988 </li></ul><ul><ul><li>Remember, 1988 was t...
The “Killer” App <ul><li>To make matters worse, we also built the killer app 20 years too soon </li></ul><ul><ul><li>Vic, ...
Go Native? Leave comfort of home? <ul><li>First deployment of IP multicast was an overlay of IP tunnels (mrouted/dvmrp) </...
Plan B: Reliable Multicast? <ul><li>So in early 1990s, community tried 2nd wave killer app:- Content Distribution via reli...
Post hoc rationalisation of failure <ul><li>Diot et al wrote a long diatribe which was well received “explaining” why IP m...
So now we have IP TV <ul><li>And we have DSL access (yes 6Mbps> original Ethernet:) </li></ul><ul><ul><li>And we have tiny...
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A Brief History of Multicast

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A Brief History of Multicast

  1. 1. A Brief History of Multicast Jon Crowcroft (University of Cambridge)
  2. 2. 20 years in the doldrums <ul><li>IP Multicast arrived way way too soon, in 1988 </li></ul><ul><ul><li>Remember, 1988 was the year TCP congestion control was first deployed </li></ul></ul><ul><ul><li>The NSFNet had not been deconstructed, and was still the “core” - traffic between european countries went via it in the US </li></ul></ul><ul><ul><li>Most non academic users were on 56kbps dial up at best </li></ul></ul><ul><ul><li>There was no WWW. No URLs, No HTTP, no HTML, no XML </li></ul></ul><ul><ul><li>There was no P2P, facebook, myspace, Halo, secondlife </li></ul></ul><ul><ul><li>Steve Deering was just far too clever for us </li></ul></ul>23 July 2007 Microsoft
  3. 3. The “Killer” App <ul><li>To make matters worse, we also built the killer app 20 years too soon </li></ul><ul><ul><li>Vic, Vat, IVS, RAT, Wb, “Mbone” family of real-time multimedia tools that worked rather well </li></ul></ul><ul><ul><li>assumed all users on 10Mbps untrammelled internet access, and overprovisioned core </li></ul></ul><ul><ul><li>Some ISPs immediately banned all non DNS UDP traffic </li></ul></ul><ul><li>Worse was to be discovered - unintended DDoS </li></ul><ul><ul><li>Anyone could join any/all group, despite not having enough downlink speed </li></ul></ul><ul><ul><li>Anyone could setup groups </li></ul></ul><ul><ul><li>Group management wasn’t (managed) </li></ul></ul>23 July 2007 Microsoft
  4. 4. Go Native? Leave comfort of home? <ul><li>First deployment of IP multicast was an overlay of IP tunnels (mrouted/dvmrp) </li></ul><ul><li>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 </li></ul><ul><li>Then when cisco deployed PIM, they broke their _own_ unicast (publically documented by berkeley at SIGCOMM a few years ago) </li></ul><ul><li>And no-one could figure out inter-domain </li></ul>23 July 2007 Microsoft
  5. 5. Plan B: Reliable Multicast? <ul><li>So in early 1990s, community tried 2nd wave killer app:- Content Distribution via reliable multicast </li></ul><ul><ul><li>RMTP, PGM, Digital Fountain plethora of techniques </li></ul></ul><ul><ul><li>All work pretty well in fact </li></ul></ul><ul><ul><li>But all depend on IP multicast deployment which was stil waiting for Cisco to hire Isidor Kouvelas to fix Dino’s code:-) </li></ul></ul><ul><li>Meanwhile, web cache acceleration seemed to be the thing </li></ul><ul><ul><li>Akamai, Inktomi, and some small inkling of googles to come, altavista, scaled up data center </li></ul></ul><ul><ul><li>Optical backbone meant capacity fine so repeated unicast not regarded as insane the way it was in 1980s </li></ul></ul><ul><ul><li>Where was a poor multicaster going to earn a crust? </li></ul></ul>23 July 2007 Microsoft
  6. 6. Post hoc rationalisation of failure <ul><li>Diot et al wrote a long diatribe which was well received “explaining” why IP multicast would never be deployed </li></ul><ul><ul><li>Somehow, the reviewers failed to spot that the same explanations would have meant IP unicast was never deloyed:-) </li></ul></ul><ul><ul><li>Lack of security </li></ul></ul><ul><ul><li>Lack of prevention of DDoS </li></ul></ul><ul><ul><li>Lack of pricing model </li></ul></ul><ul><ul><li>Lack of killer app </li></ul></ul><ul><ul><li>… .see where I am heading? </li></ul></ul>23 July 2007 Microsoft
  7. 7. So now we have IP TV <ul><li>And we have DSL access (yes 6Mbps> original Ethernet:) </li></ul><ul><ul><li>And we have tiny 100$ machines that can do video </li></ul></ul><ul><ul><li>And not even the massive data center and optical capacity can run 1M TV live channels </li></ul></ul><ul><ul><li>So multicast to the rescue!!! </li></ul></ul><ul><li>Of course, we also have </li></ul><ul><ul><li>IGMPv3, source specific multicast, and a bunch of overlays that allowed us to evolve a business model for CDNs, to be fair:-) </li></ul></ul>23 July 2007 Microsoft

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