An Internet Exchange Point, or IXP, is a shared physical location where independently operated networks meet and hand traffic directly to one another. Instead of every network buying transit from a larger provider to reach the rest of the internet, networks that are present at the same exchange can peer, sending traffic to each other over a common switching fabric. This keeps local traffic local, lowers cost, and reduces latency, since packets between two networks at the same exchange need not detour through a distant third party.
IETF documentation treats the IXP as a well-understood building block of the internet’s structure. RFC 7948, “Internet Exchange BGP Route Server Operations” (Hilliard, Jasinska, Raszuk, and Bakker, September 2016), opens by noting that “the popularity of Internet Exchange Points brings new challenges to interconnecting networks,” and it describes the mechanics of how participants at an exchange establish the BGP sessions through which they swap routing information and traffic.
The defining technical problem at an IXP is scale. If every participant must set up a direct BGP session with every other participant, the number of sessions grows roughly with the square of the number of members, which becomes an administrative burden as exchanges reach dozens or hundreds of members. RFC 7948’s central subject, the route server, addresses this: each participant peers once with a shared route server, which redistributes routes among all members. This collapses a full mesh of n(n-1)/2 sessions down to n sessions and, as the RFC puts it, “can dramatically reduce the administrative and operational overhead associated with connecting to IXPs.”
Exchanges became important as the internet commercialized in the early 1990s. When the NSFNET backbone’s acceptable use policy discouraged commercial traffic, providers needed neutral places to interconnect that were independent of any single backbone. Early commercial exchange points and metropolitan area exchanges filled that role, and the NSFNET transition plan of 1995 deliberately reorganized the U.S. internet around network access points where backbones would meet. The neutral, many-to-many exchange became the standard way networks join the internet’s fabric.
Because they concentrate so much interconnection in one place, IXPs are also points where reliability and security matter intensely. RFC 7948 devotes attention to operational hazards such as path hiding, prefix leakage, and next-hop hijacking, reflecting the fact that a misbehaving member or route server can affect many networks at once. Today large IXPs in cities around the world carry an enormous share of global traffic, and being present at the right exchanges is a core part of how networks engineer their connectivity.