Transit

What Transit Provides

Internet transit is a service in which an upstream network sells a downstream network full global IP reachability in exchange for a usage-based or flat-rate fee. The transit provider advertises the customer IP prefixes to the rest of the internet via 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." and forwards all inbound traffic destined for those prefixes. In return, the transit provider forwards all outbound traffic from the customer toward any internet destination through its own backbone and PeeringA mutual arrangement between two networks to exchange traffic directly and freely (settlement-free peering) at an interconnection point, bypassing third-party transit providers. Peering reduces costs and latency for both parties. relationships.

Transit vs. Peering Economics

PeeringA mutual arrangement between two networks to exchange traffic directly and freely (settlement-free peering) at an interconnection point, bypassing third-party transit providers. Peering reduces costs and latency for both parties. is settlement-free traffic exchange between networks of comparable size or strategic value. Transit is a commercial relationship where the buyer pays for access to the seller global routing table. Content-heavy networks that generate more traffic than they receive often find peering cheaper than transit for the majority of their traffic, especially when 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. membership allows them to peer directly with hundreds of 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. Networks that are primarily transit buyers rather than content originators — enterprises, smaller ISPs — rely heavily on transit.

Redundancy and Provider Selection

Operating with a single transit provider creates a single point of failure and gives that 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. leverage over pricing. Multi-homed networks maintain 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." sessions to two or more transit providers and use LOCAL_PREF and MED BGP attributes to control which provider handles which traffic. 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 use looking glass servers to verify that their prefixes are correctly visible across multiple transit paths before and after provider changes. Route filtering at transit boundaries is a key defence against BGP HijackAn attack or misconfiguration where a network falsely announces ownership of IP prefixes it does not control, causing internet traffic to be rerouted through the attacker's network. Can be used for surveillance, traffic interception, or denial of service. propagation.