Internet exchange point
An Internet Exchange Point is a point at which Internet Service Providers, and sometimes end user organizations, can exchange traffic for one anothers' customers. In this context, autonomous systems that exchange reachability information for their own customers are called peers, not to be confused with the use of the word peer to describe a generic BGP session. The most common model of peering at an IXP is multilateral, with all willing AS exchanging customer routes and not charging one another for the service, since it is of mutual benefit.
The exchange is most commonly done through a set of high-speed data link layer switches, with the minimum connection speed being 100 Mbps, 1 Gbps common, and faster links in use. Some IXPs have several sites, and interconnect their switches with links of at least 10 Gbps.
While it is technically possible to use an IXP connection for access to an Internet transit provider, this is generally not allowed. The fundamental purpose of an IXP is revenue-neutral exchange, by providers considering one another as equals, of access to their customers. A customer-provider relationship goes against the economic model of exchange points.
It may be possible, at a given IXP, to run a physical link from the customer AS to the transit provider AS; the IXP may charge a one-time fee or a continuing fee for this sort of "private peering".