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

  • From: Marshall Eubanks
  • Date: Wed Jan 10 01:52:22 2007

Dear Valdis;

On Jan 9, 2007, at 10:02 PM, [email protected] wrote:

On Tue, 09 Jan 2007 11:29:32 EST, Gian Constantine said: 
If you considered my previous posts, you would know I agree streaming
is scary on a large scale, but unicast streaming is what I reference.
Multicast streaming is the real solution. Ultimately, a global
multicast network is the only way to deliver these services to a
large market.

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?

This is a very good point. It is very reasonable to expect viewing choices to follow
a Pareto distribution (such as Zipf's law or the 80-20 rule). That plus some reasonable
economic assumptions make 30K commercial channels not an unreasonable assumptions in a
few years. But that also implies that it is _not_ realistic to have "30K multicast streams that each have
only one or at most 2-3 viewers." You may have 30K streams, most may have only a few viewers, and
still have fairly large savings.

To flesh out your example,
if you have 1 million viewers on your network, and if you assume 30K channels and
the same Pareto distribution as web sites,

- the largest channel has 1.8% of the audience
- 50% of the audience is in the largest 2700 channels
- the least watched channel has ~ 10 simultaneous viewers
- the multicast bandwidth usage would be 3% of the unicast.

These same models IMHO makes cell phone RF multicast not incredibly compelling. Because there is less
feedback on a multicast RF, the power has to be greater for a multicast channel, and
in that case the bandwidth (or RF power) savings are small or even negative, because you only
have maybe 100 people on a cell watching.

Regards
Marshall