On Tue, 15 Jan 2008 17:56:30 +0900 Adrian Chadd <adrian@creative.net.au> wrote:
On Tue, Jan 15, 2008, Mark Smith wrote:
But the fat man isn't allowed to take up residence in the restaurant and continously eat - he's only allowed to be there in bursts, like we used to be able to assume people would use networks they're connected to. "Left running" P2P is the fat man never leaving and never stopping eating.
ffs, stop with the crappy analogies.
They're accurate. No network, including the POTS, or the road networks you drive your car on, are built to handle 100% concurrent use by all devices that can access it. Data networks (for many, many years) have been built on the assumption that the majority of attached devices will only occasionally use it. If you want to _guaranteed_ bandwidth to your house, 24x7, ask your telco for the actual pricing for guaranteed Mbps - and you'll find that the price per Mbps is around an order of magnitude higher than what your residential or SOHO broadband Mbps is priced at. That because for sustained load, the network costs are typically an order of magnitude higher.
The internet is like a badly designed commodity network. Built increasingly cheaper to deal with market pressures and unable to shift quickly to shifting technologies.
That's because an absolute and fundamental design assumption is changing - P2P changes the traffic profile from occasional bursty traffic to a constant load. I'd be happy to build a network that can sustain high throughput P2P from all attached devices concurrently - it isn't hard - but it's costly in bandwidth and equipment. I'm not against the idea of P2P a lot, because it distributes load for popular content around the network, rather than creating "the slashdot effect". It's the customers that are the problem - they won't pay $1000 per/Mbit per month I'd need to be able to do it... TCP is partly to blame. It attempts to suck up as much bandwidth as available. That's great if you're attached to a network who's usage is bursty, because if the network is idle, you get to use all it's available capacity, and get the best network performance possible. However, if your TCP is competing with everybody else's TCP, and you're expecting "idle network" TCP performance - you'd better pony up money for more total network bandwidth, or lower your throughput expectations. Regards, Mark. -- "Sheep are slow and tasty, and therefore must remain constantly alert." - Bruce Schneier, "Beyond Fear"