|
North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: multicast (was Re: Readiness for IPV6)
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 > > -- -------------------------------------------------------------------------- Joel Jaeggli Academic User Services [email protected] -- PGP Key Fingerprint: 1DE9 8FCA 51FB 4195 B42A 9C32 A30D 121E -- In Dr. Johnson's famous dictionary patriotism is defined as the last resort of the scoundrel. With all due respect to an enlightened but inferior lexicographer I beg to submit that it is the first. -- Ambrose Bierce, "The Devil's Dictionary"
|