In network engineering, peering is an agreement between Internet service providers(ISPs) to exchange traffic. Such peerings can be made between two or more service providers and allow the ISPs to use the backbones of the other service providers participating in the peering for data transmission.
Peering includes not only the networks of large ISPs, but also those of smaller ones in order to reach the regional endpoints of Internet Access Providers(IAPs) through them. It is often based on reciprocity, with no mutual charging for traffic. However, fee-based agreements - paid peering - can also be made when large Internet service providers, known as tier 1 providers, exchange data with smaller providers, known as tier 2 providers. The data exchange itself takes place via the Internet nodes, the peering points( PP) or Internet exchange points( IXP). In Germany, the German Commercial Internet Exchange( DE-CIX) in Frankfurt is the largest Internet Exchange Point; others are BCIX in Berlin, ECIX in Düsseldorf and N-IX in Nuremberg.
Peering itself reflects the Internet, as providers network with each other and transport other providers' traffic over their networks. Peering and mutual networking give the Internet greater stability, as traffic can be redirected via other provider networks if one provider fails. Data traffic becomes cheaper and faster because data packets can take the shortest route.