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How Networks Interact — Peering and Transit Explained
Raindeer writes to share his article about peering and transit between networks, which begins:
"In 2005, AT&T CEO Ed Whitacre famously told BusinessWeek, 'What they [Google, Vonage, and others] would like to do is to use my pipes free. But I ain't going to let them do that...Why should they be allowed to use my pipes?'
The story of how the Internet is structured economically is not so much a story about net neutrality, but rather it's a story about how ISPs actually do use AT&T's pipes for free, and about why AT&T actually wants them to do so. These inter-ISP sharing arrangements are known as 'peering' or 'transit,' and they are the two mechanisms that underlie the interconnection of networks that form the Internet. In this article, I'll take a look at the economics of peering and transit in order to give you a better sense of how traffic flows from point A to point B on the Internet, and how it does so mostly without problems, despite the fact that the Internet is a patchwork quilt of networks run by companies, schools, and governments."
These inter-ISP sharing arrangements are known as 'peering' or 'transit,'
This makes it sound like 'peering' and 'transit' mean the same thing, and cover all traffic-sharing agreements. To my knowledge, that's not the case (and wikipedia agrees: http://en.wikipedia.org/wiki/Peering).
There are three types of relationships. In one, called peering, A and B accept traffic from each other and don't exchange money. In the two other, A accepts traffic and money from B, while B accepts traffic from A. From B's point of view, that's called transit, while from A's point of view it's called customer.
(I hope at least some of you learned something you didn't know already. Otherwise, I've wasted the interpipe transit peering capacity).
The difference between transit and peering is explained on the first page of the article. Congratulations for posting before reading even that far.
Generally peering happens at an IX, where a bunch of service providers chip in together towards the cost of running the IX (which has it's own independent management structure.) Service providers with a presence at the IX pay for their own infrastructure (switches, routers, Xbox 360s...)
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Normally each side would pay for their physical plant... to the peering point, and meet in the middle. The rooma at a datacenter of sufficient size to do so, is called a meet-me room.
I personally find it funny to see AT&T talking about tier-1 status peering, when referring about themselves... It's my understanding it's been a while since they did so.
Peering means that two networks each pay their costs to connect to a common point where the networks are interconnected and then they each accept traffic to their own network from the other network without compensation. (Actually that's called "settlement free peering", this is all gradual.) Often the common point is a third party operated facility which is dedicated to interconnecting many networks. These facilities are called "common internet exchanges," abbreviated CIX. All providers connected at such an exchange pay for that service. Here are some graphs showing the total traffic at the biggest internet exchange in Germany, DE-CIX: http://www.decix.de/content/network.html
Well, obviously somebody pays for the physical plant. It doesn't just magically appear in a shower of sparkles whenever two networks sign a peering agreement. But, each network just buys whatever equipment they need, and then they plug it together. It's just like if I decided I was going to run a cat. 5 cable to my neighbor's house. We'd basically have a peering arrangement where I could see his network, and he could see mine. He would own his switch, and I would own my switch. But, no money would change hands between us. I wouldn't pay for him to buy a switch so there is something for me to plug into. We would just each have the needed equipment. Maybe we would set up a two way redundant link, and each of us would buy an extra long cat 5 cable for the peering.
Peering between major networks is fundamentally the exact same thing as peering between home networks, or department networks on a school campus, or any other networks. The complexity of the networks being joined together may be different, and the equipment being used to do it may range from a ten dollar hub to a zillion dollar fiber optic monster, but the concept is the same.
When you sign up for Qwest DSL or whatever, it isn't like Qwest has a giant cable running from their building to THE INTERNET. The Internet is just a collection of networks. Some networks make you pay to connect. Others just connect between each other. That's the difference between transit and peering.
AT&T and every other provider can dip as many times as they want. It's mostly a "truth in advertising" thing: If you call yourself an internet provider, you basically have to provide access to the whole internet. If you can persuade other providers, your users and remote networks to pay you, that's fine. However, if you can't make a remote network pay you and you stop providing access to that network or reduce the quality of the connection as to render it unusable, then you are no longer an internet provider and should not be allowed to call yourself that. Your customers should then be allowed to cancel their contracts for your failure to deliver the advertised service.
Is that why I pay for my incoming SMS and calls? ;)
It's why I don't pay for calling you if you have a cellphone and I don't. And why I don't pay more for RECEIVING a call from a cellphone. Or, when YOU'RE calling a cellphone, it doesn't cost you twice as much as if you're calling a landline phone.
They want to do the equivalent of charging people calling you for your airtime, and charging you for your airtime as well. If you do the equivalent of making a call from a cellphone to another cellphone, they want to charge you twice.
Telstra provides the pipe leases to all the ISP's.. at stupidly high rates, resulting in those annoying (explative deleted)s which invade every slashdot thread talking about how "awesome" regressing back 2 decades to metered internet is.
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Yes.
Google may be a bad example - I'd bet they have enough of their own network to be a Tier-1 peer by now (guess)
But imagine some random website, your favorite blog or something. Blog pays for bandwidth, you pay for bandwidth. AT&T (and the other providers) want to charge Blog for the right to use bandwidth they already paid for.
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