Transit

A transit customer's network connects to its transit provider, which advertises the complete internet routing table to that customer via BGP, giving the customer's own traffic a path to reach essentially any destination on the internet through that single upstream relationship. In exchange, the customer typically pays for the capacity and access, and its own network's routes get advertised onward by the provider so traffic can also reach the customer from elsewhere on the internet.

The reason most networks maintain both transit and peering relationships rather than relying exclusively on one is that they solve different parts of the same underlying reachability problem — peering can eliminate transit costs for traffic exchanged with specific peer networks where a mutually beneficial direct relationship is viable, but no realistic amount of peering covers the entire internet, leaving transit as the necessary fallback that guarantees complete reachability regardless of how extensively a network has built out its own peering relationships. This is precisely why transit functions as the reliability backbone underlying most networks' internet connectivity even when peering handles a meaningful share of total traffic volume: transit's paid, contractual nature provides a guaranteed reachability floor that voluntary, mutual-benefit-based peering arrangements don't inherently promise in the same way. For CE verticals, transit is typically the connectivity relationship enterprises and smaller operators actually purchase directly, working through an internet service provider that itself manages the underlying mix of transit and peering relationships needed to deliver complete internet reachability to its own customers.