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

Wed Jan 10 06:49:20 UTC 2007

Dear Valdis;

On Jan 9, 2007, at 10:02 PM, Valdis.Kletnieks at vt.edu 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