Peering
Peering is the practice of exchanging
Internet traffic with peers.\nIt involves three elements:\n* the physical interconnection of the networks,\n* technical liaison between the networks to allow exchange of routes, and\n* the commercial and contractual peering agreements.
Internet service providers (ISPs) set up
peering points, the physical locations where exchanges happen and negotiate
peering agreements.\nMost peering points are located in colocation centres, where the different network operators 'co-locate' their
Points of Presence.
History of peering
In the early days of the Internet, a backbone network existed in the form of first the ARPANET and later the NSFNET. All other networkss connected with one another via the Internet backbone, and routing information was conveyed between the backbone and the other networks via the Exterior Gateway Protocol (EGP).
The modern Internet no longer has a backbone in the traditional meaning, rather it consists entirely of the various commercial ISPs and private networks. They are all connected at their peering points and supported by the Border gateway protocol (BGP) which allows them to coordinate the operation of the Internet without any central authority.
Types of peering agreements
The act of peering can be done as:\n* a private peering,\n* a peering via an Internet Exchange Point (ones that are independent of any single provider), or\n* as a customer-provider relationship.
Providers with large traffic volumes, often known as Tier 1 carriers, tend to peer without charge with other large providers, and charge for peering with smaller ISPs.
Providers with smaller traffic tend to converge at Internet exchange points, which provides them with a commercially neutral venue for peering.
Peering as a customer-provider relationship is most common at the bottom tiers of the Internet business. The latter is not a true peering relationship; rather, the customer pays for transit via their upstream ISP.
See also
\n* Autonomous system
