Software Distribution via Multicast?

RockyMountain asks: "When it took me over 24 hours to download the latest Mandrake ISOs, I got to wondering...why do we still put up with servers overloaded with zillions of simultaneous TCP connections, all sending copies of the same thing?Hasn't multicasting evolved to the point where there's a better way? A quick look at Freshmeat turned up no obvious candidates. Are there any protocols or programs for distributing software via multicast? Are there any evolving standards? Or are there fundamental problems with this approach that I am overlooking?" An interesting question. With my limited understanding of Multicast, I would think that, at the very least, if you are a software distribution site you can have software distribution "channels", where each channel serves one piece of software. Milticast clients wanting a specific piece of software would connect to the right channel and wait until the next time it starts serving the software from the beginning (or, in the case of an interrupted connection, when the channel gets to the appropriate resume point). Might such a system be ideal for multicast? Can any of you come up with others?

Comments

Big Problem.

[UnifiedTechs]

The biggest problem I see with a multicast method for ISO images isn't the varying start times, but the varying connection speeds of users.

Multicast video works because there is only X number of bits needed at any one time. Aka, a 24k video stream only needs 24k of pipe to work, having a T1 down won't help you get the video faster. But having a T1 will help you download an ISO image faster so you can start the install process.

Also streaming video and such does not require a perfect stream... if a piece is missing it just ignores it and goes on its way. But an ISO image needs to be perfect. If not you just made a nice coaster for your coffee cup.

The only way I see it working is if everyone agreed to download at the speed of the slowest link. And I'm not going to agree to let my DSL line go to waste so I can download at the 33.6k of the dialup user who wants to wait 4 days for a download. Also having to be perfect would require the server to resend anytime a client reported a lost or corrupted packet. One needs only to be familiar with Norton Ghost and a lab with one bad NIC or HDD to see the crawl this will result in till the bad box times out.

So while nice in theory I doubt it would have much benefit outside of a controlled lab environment where everyone is on the same high-speed connection and there is very little loss of packets.