So what is an IXP?
The Internet. The network of networks. I connect mine to yours, you connect yours to theirs, they connect theirs to another, and so on and so on. In just a few hops I can communicate with anyone, anywhere, anytime. Sounds simple enough. The Internet has become a tool in everyday life and work all around the world. People and businesses are connected with one another through a multitude of devices with many applications making our lives easier, more fun, more interactive and definitely closer together on a global scale.
But how does it really work? If I have to sign a 15-page agreement just to install software on my PC, how is it that I can traverse the globe from my desktop and only pay a small monthly fee to my local Internet Service Provider?
The Internet is founded on principles of openness, neutrality and decentralization. Designed to place intelligence at the edge of the network, and to separate traffic from specific hardware, the Internet is able to rapidly adopt advances in communications technology and infrastructure while maintaining compatibility with existing equipment. In fact, the only job of the Internet is to efficiently transport packets from end to end, in a way that is tolerant to failures, congestion and other impairments.
Your local ISP typically provides connectivity to you home through your local telephone exchange or cable service. In hard-to-reach locations, it may even be via a wireless or satellite connection. In some cases your provider may own the physical cables, in other cases they simply rent the use of them in order to provide you with service. Competition for your business helps keep the costs down, and everyone's a winner.
So now you are connected to your provider's network. So far, so good. But if you want to browse further than the other computers that are also on your ISP's network, you have to hand off the data from one network to another. That's the extraordinary value of the Internet. You're not depending on your ISP to win customers, you are simply able to exchange data with anyone around the globe!
So how do I get from one network to another? Who decides how these networks will be interconnected? What equipment is used, and who pays for it all? The answer is "It Depends".
Some networks agree to carry traffic for others in exchange for a fee. This is called Transit, and is often used when a small network wants to send data across a large network.
In other cases networks agree to a Peering arrangement, where traffic is exchanged between networks for the mutual benefit of both parties. Strictly speaking, peering is meant to be 'settlement-free' or no cost, although sometimes fees may be applied to specific peering agreements.
In either case, the exchange of data between networks is usually done in a facility dedicated to that purpose: the Internet Peering Exchange, or Internet Exchange Point. Transit connections can be made at any convenient Point of Presence in a Carrier's network, but Internet Exchanges tend to be located in carrier-neutral, purpose-built facilities that permit interconnections between the equipment of many different network operators. The ISPs all bring their Network to the Exchange, and the exchange creates the environment where they can all Peer efficiently with each other. The exchanges are often neutral network -independent organizations, either owned in Association like many in Europe or owned by carrier neutral datacenters like in the US or Asia - Pacific.
So Peering between networks always happens at exchanges? Not necessarily, two ways of peering exist, private peering and public peering . Public peering happens at exchanges, where the neutral Internet exchange infrastructure is between the networks. Private peering is a direct private interconnect between the two network routers of the peering parties.
As said there are many Internet exchanges small and large, most countries have one or more exchanges, mostly in the larger cities as this is where the Internet traffic and infrastructure is, as well as end-user concentration. Some of these exchanges have grown to become regional hubs or even continental or international hubs. Most though have a national focus, interconnecting the parties in a country to keep local traffic local.
Internet exchanges add to the stability of the Internet as they provide stability, efficiency and redundancy to the net’s infrastructure. By connecting to several IXPs the networks have many routes to one another keeping the traffic exchange stable and redundant without having to invest heavily in many many direct interconnects. This way the Web is created, as networks will design their infrastructure to the profile of the users and content they consume, none of them the same.
So to resume there are 3 ways for networks to exchange traffic with one another: public peering, private peering and transit. Most networks will try to ‘peer-away’ as much traffic as they can on exchanges as it is most economic and gives the most control over the traffic flows. For some larger traffic flows they will direct peer with parties based on specific business arrangements or just to off-load public peering infrastructure. Some of the very large networks around the world only do private peering with each other to be a Tier-1 network, as it is called. These networks can reach All of the Internet routes directly. Those Tier-1 networks, are mostly the ones that sell transit commercially, where other parties trust them to deliver their traffic to the final destination.
The Internet thus is truly a web of networks where the traffic will find its way if one of the routes is not available. The IP protocol and the underlying network technology will just tell the packets to go the next best route. So in case of a failure somewhere on the globe the traffic flows shift real-time.
Say there is a problem with a fiber-cable between Paris and Amsterdam you will see networks automatically reroute traffic Paris - Frankfurt-Amsterdam or Paris- London- Amsterdam. Of course on these routes there is redundancy and more likely you will just see parties starting to use another fiber-pair. Similarly if there is a problem on an IXP the networks all have other routes by peering at other IXPs and transit they can use to still make sure their end-users are not or least affected. All IXPs have one major condition for networks to join and that is that they have to be an Autonomous network, meaning they take responsibility for managing their traffic flows, so they plan for redundancy.
The type of arrangement between networks will be influenced by many factors, including the kind and amount of traffic and the type of customer. It may prove interesting to describe a few terms:
- Eyeball network: refers to a network with lots of users who tend to pull in lots of content. Examples would include most consumer-oriented ISPs. Where the customers 'eyeballs' are of value to potential peers.
- Content Network: refers to network destinations that contain information that customers want to see. Examples include Google, Yahoo, MSN, as well as distributed content providers like Akamai and Limelight.
- Carrier Network: refers to global or continental networks which sell reachability to distant locations. These networks are also often referred as tier-one and tier-two networks.
- Hosting providers: refers to companies that provide server capacity to other companies thus providing the base for many many websites and applications all over the Web.
All of these types of Internet companies exchange traffic through a combination of public and private peering or transit at key locations throughout their region, country, continent or even on a global scale. Please tell/visualize our story ……