Peering

Peering is a direct interconnection between two autonomous systems for the purpose of exchanging traffic between their own networks and their respective customer networks. It is not a purchase of internet reachability — neither side promises to deliver traffic to the rest of the internet on the other's behalf. The arrangement is typically settlement-free when the traffic and value exchanged are roughly balanced, and paid when they are not.

Peering is established in two forms. Public peering happens at an Internet Exchange Point (IXP) such as DE-CIX, AMS-IX or LINX, where many networks connect to a shared switching fabric and run BGP sessions with each other over that fabric. It is cost-efficient for reaching a large number of networks with relatively modest volumes per peer. Private peering, or PNI (private network interconnect), is a dedicated cross-connect between two networks, typically inside the same data centre. PNIs are used when volumes are high enough that a dedicated link is cheaper or more predictable than shared IXP capacity.

Operationally, peering reduces the share of traffic that has to traverse a transit provider, which generally lowers cost and shortens the AS_PATH toward the peer's customers. Shorter paths and direct delivery also tend to improve latency and reduce the number of routing hops a packet crosses, which matters for real-time traffic. Peering does not replace transit: a network still needs transit to reach destinations it does not peer with directly. Peering policies (open, selective, restrictive) determine which networks an operator is willing to peer with and on what terms, and large content networks like Google, Meta and Netflix publish their policies publicly to make the request process predictable.