Peering

Bilateral and Multilateral Peering

Peering is a direct BGPBorder Gateway Protocol. The routing protocol that exchanges reachability information between autonomous systems, effectively determining how data traverses the internet. Often called the "postal service of the internet." interconnection between two networks for the purpose of exchanging each other traffic — and only their own traffic — without payment. Bilateral peering involves direct BGP sessions and explicit route exchange between two Autonomous System (AS)A large network or group of networks under a single administrative policy, identified by a unique Autonomous System Number (ASN). The internet is composed of tens of thousands of interconnected autonomous systems. operators. Multilateral peering at an Internet Exchange Point (IXP)A physical facility where multiple ISPs and networks interconnect to exchange traffic directly rather than through upstream transit providers. IXPs reduce latency, lower costs, and improve redundancy. uses a route server to distribute routes among all participating members, greatly simplifying the operational overhead of peering with many networks simultaneously.

Open vs. Selective Peering Policies

Large networks publish peering policies that define which organisations they will peer with. Open peering policies accept sessions from any network meeting minimum traffic and technical criteria. Selective peering policies require minimum traffic volumes, geographic presence at multiple Internet Exchange Point (IXP)A physical facility where multiple ISPs and networks interconnect to exchange traffic directly rather than through upstream transit providers. IXPs reduce latency, lower costs, and improve redundancy. locations, and 24/7 NOC coverage. Networks that do not qualify for direct peering must purchase TransitA paid arrangement where one network (the customer) pays another (the transit provider) for access to the rest of the internet. Unlike peering, transit provides full routing table access and is the primary way smaller networks connect to the global internet. instead. Tier 1 networks maintain purely settlement-free peering among themselves, creating the backbone of the internet without any payment flowing between them.

Private Network Interconnect

High-volume peering pairs often establish Private Network Interconnects — dedicated physical or DWDM wavelength connections between their facilities — bypassing shared IXP switch fabric entirely. PNIs carry traffic at 10, 100, or 400 Gbps, with lower LatencyThe time delay for a data packet to travel from source to destination, typically measured in milliseconds (ms). Lower latency is critical for real-time applications like video calls, gaming, and financial trading. and higher reliability than shared infrastructure. Major CDNContent Delivery Network. A geographically distributed network of servers that caches and serves content from locations close to end users, reducing latency and improving load times. Major providers include Cloudflare, AWS CloudFront, and Akamai. providers establish PNIs with large ISPInternet Service Provider. A company that provides internet access to consumers and businesses, assigning public IP addresses and routing traffic to the wider internet. Examples include Comcast, AT&T, and SK Broadband. networks to deliver video and software update traffic at scale without congesting IXP ports. Use IP Lookup to identify the ASNAutonomous System Number. A unique identifier (e.g., AS13335 for Cloudflare) assigned by a Regional Internet Registry to an autonomous system. ASNs are used in BGP routing to identify networks on the internet. of any IP address and understand its peering ecosystem.