[Nanog] Lies, Damned Lies, and Statistics [Was: Re: ATT VP: Internet to hit capacity by 2010]

Alexander Harrowell a.harrowell at gmail.com
Tue Apr 22 07:35:41 CDT 2008


On Tue, Apr 22, 2008 at 1:13 PM, Mark Smith <
nanog at 85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org> wrote:

> On Tue, 22 Apr 2008 11:55:58 +0100
> <michael.dillon at bt.com> wrote:
>
> > But there is another way. That is for software developers to build a
> > modified client that depends on a topology guru for information on the
> > network topology.
>
> <snip>
>
> Isn't TCP already measuring throughput and latency of the network for
> RTO etc.? Why not expose those parameters for peers to the local P2P
> software, and then have it select the closest peers with either the
> lowest latency, the highest throughput, or a weighed combination of
> both? I'd think that would create a lot of locality in the traffic.
>
> Regards,
> Mark
>

This is where you hit a serious problem. If you implemented that in a
client, it could be much worse than naive P2P for quite a lot of networks -
for example all the UK ISPs. If you have a bitstream/IPStream architecture,
your bits get hauled from local aggregation sites to your routers via L2TP
and you get billed by the telco for them; now, if you strictly localise P2P
traffic, all the localised bits will be transiting the bitstream sector
TWICE, drastically increasing your costs.

(Assumption: your upstream costs are made up of X amount of wholesale
transit+Y amount of peering, unlike your telco costs which in this case are
100% transit-like and paid for by the bit.)

Things also vary depending on the wholesale transit and peering market; for
example, someone like a customer of CityLink in Wellington, NZ would be
intensely relaxed about local traffic on the big optical ethernet pipes, but
very keen indeed to save on international transit due to the highly
constrained cable infrastructure. But if you were, say, a Dutch DSL operator
with incumbent backhaul, you might want to actively encourage P2Pers to
fetch from external peers because international peering at AMSIX is
abundant.

Basically, it's bringing traffic engineering inside the access network.

Alex



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