Network end users to pull down 2 gigabytes a day, continuously?

Sean Donelan sean at
Wed Jan 10 05:08:40 UTC 2007

On Tue, 9 Jan 2007, Valdis.Kletnieks at wrote:
> Multicast streaming may be a big win when you're only streaming the top
> 5 or 10 networks (for some value of 5 or 10).  What's the performance
> characteristics if you have 300K customers, and at any given time, 10%
> are watching something from the "long tail" - what's the difference between
> handling 30K unicast streams, and 30K multicast streams that each have only
> one or at most 2-3 viewers?

1/2, 1/3, etc the bandwidth for each additional viewer of the same stream?
The worst case for a multicast stream is the same as the unicast stream, 
but the unicast stream is always the worst case.

Multicast doesn't have to be real-time. If you collect interested 
subscribers over a longer time period, e.g. scheduled downloads over the 
next hour, day, week, month, you can aggregate more multicast receivers 
through the same stream.  TiVo collects its content using a broadcast

A "long tail" distribution includes not only the tail, but also the 
head.  30K unicast streams may be the same as 30K multicast streams, but
30K multicast streams is a lot better than 300,000 unicast streams.
Although the long tail steams may have 1, 2, 3 receivers of a stream, the 
Parato curve also has 1, 2, 3 streams with 50K, 25K, 12K receivers.

With Source-Specific Multicast addressing there isn't a shortage of 
multicast addresses for the typical broadcast usage.  At least not until
we also run out of IPv4 unicast addresses.

There is rarely only one way to solve a problem.  There will be multiple
ways to distribute data, video, voice, etc.

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