> On Jan 18, 2024, at 22:51, le berger des photons via Nnagain
> <[email protected]> wrote:
> First I've ever seen the term IXP. It seems interesting. Can you point me
> to some documentation at a level which only requires the ability to read in
> english? Lots of what I've seen here has initials for things which I haven't
> even been able to decode.
> I've been connecting 200 families in a 25 km radius to internet via 8 fiber
> optic connections for the last 20 years.
> I've been thinking of inviting others to participate, help them get going.
> Thinking how it might be useful to provide each client two accesses. one to
> the global internet, one to a local network which isn't being watched by big
> brother.
> Does any of this warrant my looking further into IXP technology?
Hi, Jay.
I’m afraid I’m really bad at getting all this stuff written down, though I know
it would be useful. I am planning to write a doctoral thesis on exactly this
topic (the societal and economic impact of Internet exchange points) for
Universite Paris 8 next year, but that will need to be a bit more academic than
practical, to satisfy, you know, academia.
So, really basically, it sounds like you’re already building an internet
exchange. Internet exchanges are where Internet bandwidth comes from.
Internet service providers bring Internet bandwidth from IXPs to the places
where people want to use it: their homes, their offices, their phones.
Internet bandwidth is free _at_ the exchange, but transport costs money. Speed
times distance equals cost. So the cost of Internet bandwidth is proportional
to the speed and the distance from IXPs. Plus a profit margin for the Internet
service provider.
So, if one Internet user wants to talk to another Internet user, generally they
hand off their packet to an Internet service provider, who takes it to an
exchange, and hands it off to another Internet service provider, who delivers
it to the second user. When the second user wants to reply, the process is
reversed, but the two Internet service providers may choose a different
exchange for the hand-off: since each is economically incentivized to carry the
traffic the shortest possible distance (to minimize cost, speed x distance =
cost), the first ISP will always choose the IXP that’s nearest the first user,
for the hand-off, leaving the second ISP a longer distance to carry the packet.
Then, when their situations are reversed, the second ISP will choose the IXP
nearest the second user, leaving the first ISP to carry the packet a longer
distance.
This only works (and achieves “fairness”) if there’s an IXP near each of the
two users (or they’re both close to the same IXP). If there’s no IXP close to
the second user, they wind up paying for long-haul transport in both
directions, and their share of the costs are higher than the first user’s. So,
ISPs (and users) are economically incentivized to build small IXPs all over the
place.
IXPs are only maximally effective if they really are free. If they start
running up costs, which have to be defrayed, and placing the burden of those
costs on the ISPs which try to use them, then they increase the _average per
bit delivery cost_ or APBDC of the bandwidth, making it less affordable, and
causing ISPs to seek more affordable bandwidth elsewhere. So an effective IXP
is a cheap IXP. “Gold plating” IXPs kills them. Fancy is bad, simple is good.
In the 1990s, there were a diversity of kinds of IXPs… we were all trying
different experiments, and nobody had settled on a single best way of doing it
yet. Then, gradually, it all narrowed down to a single most-efficient model,
and all IXPs were an Ethernet switch in a closet, surrounded by BGP routers
which had one port facing the switch, and one or a small number of ports facing
their ISP’s network. But in the last ten years or so, things have started to
become a little more diverse again, so what you’re doing would probably be
recognized as a form of IXP by many people.
Economic compartmentalization is really important in IXPs. Some people call
this “neutrality,” but that’s a difficult word to define, because it means
different things to different people. What’s important is that the IXP is a
shared, communal, enterprise, and the group of parties who are collaborating to
make it go are often business competitors, which means that they need a very
simple system that doesn’t require that they trust each other very much. So,
if it handles money at all, it’s very hard to get over that trust threshold. If
it has complicated rules or governance, it has difficulty getting over that
trust threshold. Simple is good.
So, if you’re thinking of making things more complicated (commercial access
(“transit”) to the global Internet), that’s fine, and may be exactly the right
thing to do, under the circumstances… but you should be very careful to
compartmentalize that, and its finances and risks, into a separate entity than
the fiber, or the “exchange” or whatever else you’re doing. Otherwise people
will worry that you’re going to use fees from one thing to subsidize another,
which will compete with their interests. That’s not hypothetical, that’s
actually one of the most common ways IXPs fail: they lose their neutrality, and
lose the trust of their participants, who form a competing exchange nearby, and
all move over to it.
All of this is generally easier to explain in a dialog. I’m in Paris, so happy
to chat with you on the phone, if your spoken English is better than my spoken
French.
-Bill
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