How do you put a TV station on the Mbone?
young at jsyoung.net
Tue May 3 07:49:16 UTC 2011
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On 03/05/2011, at 1:33 PM, George Bonser wrote:
> f there are 10,000 Comcast subscribers watching exactly the same live
> event on the net, sending 10,000 streams of exactly the same data is
> dumb and it doesn't have to be that way.
It's pretty likely that those 10,000 streams will originate in as few as 5 but
as many as 40 or so individual CDN-type devices imbedded deep in
Comcast local networks. Therefore, the consumption of bandwidth that
seems wasteful is limited and in proportion to the distance between the
viewers and these devices. The same devices can be used to originate
long-tail (not often watched) content, Video on Demand content, time-
shifted content and so forth.
Multicast is an elegant solution to a dwindling problem set. Patrick rightly
points out that enabling multicast to the end user may just not be worth the
operational cost. Multicast as a tool the provider uses on the other hand
is well worth the expense. You might use it to broadcast content to your
CDN-like devices or keep your trading desks up to date with the latest ticker
feeds. AT&T uses multicast to push video channels (the IP equivalent of
broadcast TV) down to and through DSLAMs for UVerse.
But viewing habits dictate technology used. For instance, AT&T might use
multicast to 'broadcast' television channels but for an "instant channel
change" feature hoards of unicast servers stand ready to feed UVerse
users who haven't figured out how to use a program guide to navigate
their sets and can't bear the latency of a S,G join. :-)
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