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.
The case of backhaul per-bit cost being higher than transit is actually
not that uncommon. However, even without localization, peers (seeders in
particular) would keep generating traffic and the resulting total cost
would consist of both transit AND backhaul. Localization in such
scenarios could help at least reduce the transit component. IOW,
localization does not produce more seeders in the local network; if it
did, it's use in such scenarios I agree would be harmful.
> 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.
Well, no, if the content was locally available (i.e. one seeder
existed), but the local leecher downloaded it from outside, the total
cost of the traffic generated by the two peers would amount to £220 as
the seeder would just be serving some other off-net leecher (and thus
costing another £110).
--
Ciao,
Enrico
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