4 ms·

you think so? can you explain more? I am not looking at the theory of it, rather interested in working models where multicast is being used to deliver online co

by prakash 18y ago

you think so? can you explain more? I am not looking at the theory of it, rather interested in working models where multicast is being used to deliver online content.

johns 18y ago
http://www.pbs.org/cringely/pulpit/2007/pulpit_20071221_003697.html http://www.pbs.org/cringely/pulpit/2007/pulpit_20071221_0036...
- tptacek 18y ago
  Akamai --- or, more likely, Comcast and AT&T --- could accomplish the same thing without detonating your routing tables, just by adding servers and indirecting content with a traffic manager. Cringely is nuts.
wmf 18y ago
Multicast does not work on the Internet today. But it could work if ISPs invested some effort.
- prakash 18y ago
  what incentives are preventing the ISP's from investing effort?
  - wmf 18y ago
    AFAIK, turning on multicast would create many additional RIB/FIB entries in routers, possibly running routers out of RAM and requiring upgrades. Also, because multicast duplicates packets, it could increase bandwidth usage in ways that are not easy to bill for, potentially increasing costs without increasing revenue. I don't think this is a real problem, but some people have cited it.
    - tptacek 18y ago
      Think about this for a second. IP addresses (which we're running out of) address hosts. There are hundreds of millions of active full-time hosts. Multicast addresses address content. How much more content is there than hosts? Do you really think it's feasible to give an IP address to every popular piece of content? YouTube allegedly gets almost 100,000 new videos per day. The fact is, multicast hasn't been a success because it's simply not a good fit for the routing layer of the Internet. But edge overlay networks can build arbitrarily complex and interesting multicast service models on top of the Unicast Internet, and those overlays have been huge successes.
      - wmf 18y ago
        I think SSM solves that problem.
        tptacek 18y ago
        No, SSM reduces an explosively intractable routing problem to merely an intractable routing problem, by guaranteeing that video streams will only have a single sender (which is not even a win when you're competing with edge overlays). You still need to have every upstream router maintain awareness of every piece of content being viewed by every downstream user.
- tptacek 18y ago
  No, multicast cannot work on the Internet if the ISPs invest more effort. There remain fundamentally unresolved problems in Deering-model (IP-level) multicast. The future of one-to-many content delivery is in edge delivery networks like Akamai. Maybe they'll use a (drastically simplified) multicast model internally, but that's an implementation detail.

by prakash 18y ago

you think so? can you explain more? I am not looking at the theory of it, rather interested in working models where multicast is being used to deliver online content.

johns 18y ago

http://www.pbs.org/cringely/pulpit/2007/pulpit_20071221_003697.html http://www.pbs.org/cringely/pulpit/2007/pulpit_20071221_0036...

tptacek 18y ago
Akamai --- or, more likely, Comcast and AT&T --- could accomplish the same thing without detonating your routing tables, just by adding servers and indirecting content with a traffic manager. Cringely is nuts.

wmf 18y ago

Multicast does not work on the Internet today. But it could work if ISPs invested some effort.

prakash 18y ago
what incentives are preventing the ISP's from investing effort?
- wmf 18y ago
  AFAIK, turning on multicast would create many additional RIB/FIB entries in routers, possibly running routers out of RAM and requiring upgrades. Also, because multicast duplicates packets, it could increase bandwidth usage in ways that are not easy to bill for, potentially increasing costs without increasing revenue. I don't think this is a real problem, but some people have cited it.
  - tptacek 18y ago
    Think about this for a second. IP addresses (which we're running out of) address hosts. There are hundreds of millions of active full-time hosts. Multicast addresses address content. How much more content is there than hosts? Do you really think it's feasible to give an IP address to every popular piece of content? YouTube allegedly gets almost 100,000 new videos per day. The fact is, multicast hasn't been a success because it's simply not a good fit for the routing layer of the Internet. But edge overlay networks can build arbitrarily complex and interesting multicast service models on top of the Unicast Internet, and those overlays have been huge successes.
    - wmf 18y ago
      I think SSM solves that problem.
      - tptacek 18y ago
        No, SSM reduces an explosively intractable routing problem to merely an intractable routing problem, by guaranteeing that video streams will only have a single sender (which is not even a win when you're competing with edge overlays). You still need to have every upstream router maintain awareness of every piece of content being viewed by every downstream user.
tptacek 18y ago
No, multicast cannot work on the Internet if the ISPs invest more effort. There remain fundamentally unresolved problems in Deering-model (IP-level) multicast. The future of one-to-many content delivery is in edge delivery networks like Akamai. Maybe they'll use a (drastically simplified) multicast model internally, but that's an implementation detail.