[NNagain] are you Bill Woodcock?

[Bill Woodcock]

> On Jan 18, 2024, at 22:51, le berger des photons via Nnagain <nnagain at lists.bufferbloat.net> 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