The Internet is a collection of separate and distinct networks referred to as autonomous systems. The relationships between these networks are generally described by one of the following categories:
Transit (or pay) – The network operator pays money (or settlement) to another network for Internet access (or transit).
Peer (or swap) – Two networks exchange traffic between their users freely, and for mutual benefit.
Customer (or sell) – A network pays another network money to be provided with Internet access.
Motivations for peering are, for example: increased redundancy, capacity for extremely large amounts of traffic, routing control over one’s traffic and performance.