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Re: [p2prg] New version of p2prg-mythbustering

Ray.Bellis at nominet.org.uk wrote:
Have you considered the case where the ISP might prefer *that their users *not** localise the traffic?
The dominant wholesale xDSL technology in the UK is BT's IPStream product. All customer traffic is backhauled via L2TP to the ISP's network (almost always to London telehouses) and no geographic localisation is possible.
This means that two neighbouring customers of the same ISP are no closer in network terms than two customers at opposite ends of the country.
Why this is particularly significant for UK ISPs is that BT's IPStream backhaul product ("BT Central") is typically 10 times more expensive than global IP transit. Currently BT charge at least £100 per Mbps pcm, whereas volume IP transit can be had for £10 per Mbps or even less.
If two customers mutually exchange traffic at 1 Mbps continuously it'll cost the ISP £200 per month. If one of the parties is off-net it'll only cost them £110.
Hence IMHO for most UK ISPs it's better for their leeching customers to be getting their data from a neighbour that's **not** on the same network.
This is the extreme case of the much more common "I would prefer to export this traffic via free peering than to transport it to one of my own customers on the other side of the country" case. 

Matthew Kaufman
ps. As someone who's designed nationwide ISP networks several times, I've often wondered why consumer ISPs care so much about uploaders. Once you've got the traffic out of the end-link multiplexing (which of course you can trivially manage) you are either handing it to another ISP you peer with, or sending it to a transit provider over a circuit that you've bought as symmetric full-duplex bandwidth but which (as you're a consumer ISP) you mostly use the downstream side of, both of which have zero incremental cost. Unless of course you have the misfortune of a user who manages to find someone on your network to send the data to.