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Re: Real Media and M-Bone feeds

  • From: Tim Wolfe
  • Date: Tue Oct 05 18:41:07 1999

On Tue, 5 Oct 1999, Sam Thomas wrote:

> What would be the point of this?

The point is that 

1.  It saves you external (transit) bandwidth, which for smaller/non-US
providers is one of the larger expenses, for on-demand types of services, eg
Real Video/Audio.  This is one of the key factors, in my opinion, of really
getting to the goal of an internet that is equally accessible to most/all
locations globally.

2.  It allows you to control the quality of service, due to the fact that
the server (cache) to client connection is all inside your own network,
unlike the multicast scheme which relies on (possibly) many external
networks to deliver the content.

> With multicast, if there is a large enough collection
> of receivers to justify a cache, there will be at most 1*bitrate on any
> single connection on the internal provider network. 

You seem to be basing your calculations on the fact that all of the intended 
recipients would be capable of receiving native multicast, which I haven't  
found to be the case..

> The cache solution is less optimal in this case. 

Forcing me to point out once again that multicast does little or nothing for
on-demand services, which contrary to popular opinion will be a much more
significant percentage than live multimedia, in my opinion.

> If you suggest a hierachical cache (i.e. main
> cache takes a feed, replicates to n distributed caches closer to the
> receivers) you have just re-invented multicast, and not very well. ;-)

A heirarchical caching scheme would be similar to multicast in that you'd
only need 1 stream from the source into your top level cache, but with the
added benefit that you would be able to deal with on-demand services as well
as live.

At least that's how it would all seem to me.  I'm not claiming to be an
expert on this topic, I'll leave that to Alex and Vadim.. :)


|       Timothy M. Wolfe | Wireless Internet = Get Some     |
| Chief Network Engineer | 1.800.338.2629 [email protected]   |
| ClipperNet Corporation | |