CIXs

Commercial Internet Exchange (CIX) refers to a class of early Internet exchange facilities that enabled commercial Internet service providers to peer directly with one another. CIXs were established in the late 1980s and early 1990s to facilitate efficient interconnection, reduce transit costs, and improve routing performance as the Internet transitioned from research to commercial use. Networks joined these exchanges to exchange traffic locally rather than paying upstream carriers for transit, often through shared switching fabric located in major metropolitan data centers.

Typically, CIXs operated as membership organizations or consortia. Member networks paid dues and adhered to peering policies that defined how routes would be exchanged and priced. Interconnection could be public, via a shared switch fabric, or private, through direct links between members in the same facility. The technical underpinnings included bilateral or multi-lateral BGP route exchanges, Ethernet-based switching, and commonly available IP routing equipment of the era.

Over time, many CIXs either evolved into or were superseded by dedicated Internet Exchange Points (IXPs) operated by neutral bodies or commercial data-center operators. The CIX model helped popularize peering and influenced the governance and operation of later IXPs, contributing to the broad adoption of Internet interconnection practices.

See also: Internet exchange point; peering; transit.