On 17/12/2008, at 12:35 AM, Jasper Bryant-Greene wrote:
People still seem to actively seek out "appointment media" even when alternatives are available (for example listening to live radio stations online when they could download music from any number of legit and non-legit sources). I don't doubt live content as a proportion of total volume is dropping, but I don't think it'll disappear entirely any time soon, and I'd even go so far as to say the volume won't be insignificant for a while yet.
It occurs to me that multicast could be a useful mechanism for subscription media. Podcasts, for example. If someone subscribes to a TV show or a podcast, why would you wait until you want to watch it before you start the download? Reducing the amount of streaming media means we can care less about latency and jitter in the network, which probably makes engineering a bit easier.
What about distributing Linux ISOs?
Well, the sender would have to send at the speed of the slowest likely receiver, and who wants to wait half an hour for the next Gentoo ISO broadcast to roll around? ;)
I guess you could have several differently-paced streams, but it strikes me that the problem of distributing Linux ISOs has been quite adequately solved already...
Divide the file in to 120x5MB chunks, play over and over on 64k or 128k streams. At 128kbit/s that's 15Mbit for a 600MB ISO, with a minimum download time of 15 minutes. Adjust the chunk sizes to fit your available bandwidth. Client can subscribe to as many as they want at a time - and we have things like RSVP so they can figure out how many they can ask for concurrently (I think.. I haven't used RSVP before). or Why do you have to start listening at the start of the file? As long as you know how far through you are who cares where you start? The start is going to come later, and if not you can fall back to unicast to grab it. Several streams of different bitrates works fine in that situation. Let's say we do the following bitrate streams: 64, 128, 192, 256, 384, 512, 768, 1024, 1536, 2048, 3072, 4096, 6144, 8192 (kbit/s). That's ~28Mbit/s total, which let's you distribute content to as many people as you want, up to 8Mbit/s. From a network point of view, it occurs to me that network providers would be much happier if all those Linux ISOs were one or two streams in over their international circuits, instead of one per end user. Also, bit torrent uses lots of upstream - which seems wasteful. I'm not sure if it's a problem right now though - probably not in NZ, I don't know of any ISPs providing Internet access to end users with constrained upstream. This is a rather interesting thought exercise. -- Nathan Ward