How do you put a TV station on the Mbone?

Jeffrey S. Young young at jsyoung.net
Sun May 8 03:09:51 CDT 2011


On 08/05/2011, at 4:10 PM, Michael Dillon <wavetossed at googlemail.com> wrote:

>> Many years ago I was the MCI side of the Real Broadcast Network.  Real Networks arranged to broadcast a
>> Rolling Stones concert.  We had the ability to multicast on the Mbone and unicast from Real Networks caches.
>> We figured that we'd get a hit rate of 70% multicast (those who wanted to see the event as it happened) and
>> 30% unicast (those who would wait and watch it later).
> 
> You do realize that unicast from Real Networks caches *IS* multicast,
> just not IP Multicast. Akamai runs a very large and successful multicast
> network which shows that there is great demand for multicast services,
> just not the low level kind provided by IP Multicast.
> 
> In fact, the most important use for IP Multicast is to work around the
> problem of the "best route". In the financial industry, they don't want
> their traffic to take the best route, because that creates a chain
> of single points of failure. So instead, they build two multicast trees,
> send a copy of each packet into each tree, and arrange that the
> paths which the trees use are entirely separate. That means
> separacy of circuits and routers and switches.
> 
> -- Michael Dillon
> 

In 1997, Real Networks caches were sending unicast.  If they now operate
differently I'm not aware (Real dumped the relationship in the DSL heyday
to chase eyeballs -- iMCI was a backbone).  

But you've got one over on me, I've never heard of Akamai's "multicast"
and given that they don't run a backbone to my knowledge it sounds as if
they're using their server installs to route packets or have an interesting 
way of source routing or tunneling multiple streams of the same data 
through ISP networks.  

As for the financial industry I was only aware of some of the reliable mcast
software in use to push ticker information to trading desks.

All very interesting but the point was that the world of entertainment video
consumption has long since become on-demand; many of the points being 
made for the use of IP multicast as a pseudo-broadcast mechanism have 
been made before (and will be made again).  I personally think P2P is a much
more interesting topic for (legally) distributing video these days and P4P
may even solve the inter provider problem that multicast never seemed to
crack.

jy



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