Re: multicast (was Re: Readiness for IPV6)

[Joel Jaeggli <joelja () darkwing uoregon edu>]

an example of a on-demand reliable multicast transport application that 
you can deploy is:

http://www.digital-fountain.com/technology/index.htm

in part it employs them mechanism you describe.

joelja

On Wed, 10 Jul 2002, Scott A Crosby wrote:

> On Tue, 9 Jul 2002, Stephen Sprunk wrote:
>
> > Even worse, multicast is truly only suitable for live applications;
> > on-demand content can't be realistically mcasted, and users will not
> > settle for "the movie starts every 15 minutes" when they've been used
> > to live VOD with unicast.  The only saving grace may be things like
> > TiVo, where an intelligent agent slurps up live mcasts in hopes that
> > the user may want to watch it "live" later.
>
> I remember seeing a presentation about 3-4 years ago for techniques for
> doing on-demand stream sending. They assume multicast, sufficient buffer
> capacity on clients to hold the entire stream, and that clients have
> enough bandwidth to recieve, say, 1.2-3.5 streams at once. There are many
> techniques, but the basic idea is to 'merge' streams together...
>
> Say, for example, you have two multicast streams  *.1 and *.2
>  *.1 is free and unused.
>  *.2 is 2 minutes into a movie.
>
> A client makes a request at T=0, and subscribes to *.1 and *.2.  *.1 sends
> the first 2 minutes of the movie then closes. The clients buffers *.2
> during those 2 minutes to get minutes 2-4 of the movie. The client drops
> *.1 which is now free. Now, at T=2, the client is listening on *.2 giving
> it minutes 4-120 of the movie, and minutes 2-4 are buffered on its hard
> drive. Now, stream *.1 is free, and two clients are on stream *.2.
>
> Thats the idea, and it can be scaled up.. I think the presentation I saw
> claimed that where clients listen to at most 2 streams, and servers send
> out at most 8 streams, then the delay before starting a 2 hour movie can
> be <12 seconds, instead of <15 minutes.
>
> Some googling finds:
>     http://www.cs.washington.edu/homes/zahorjan/homepage/
>
> Which can be read or mined for references.
>
> Scott

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Joel Jaeggli          Academic User Services   joelja () darkwing uoregon edu    
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