Internet

=== Service tiers ===
[[File:Internet Connectivity Distribution & Core.svg|thumb|Packet routing across the Internet involves several tiers of Internet service providers.]]

[[Internet service provider]]s (ISPs) establish the worldwide connectivity between individual networks at various levels of scope. End-users who only access the Internet when needed to perform a function or obtain information, represent the bottom of the routing hierarchy. At the top of the routing hierarchy are the [[tier 1 network]]s, large telecommunication companies that exchange traffic directly with each other via very high speed [[fiber-optic cable]]s and governed by [[peering]] agreements. [[Tier 2 network|Tier 2]] and lower-level networks buy [[Internet transit]] from other providers to reach at least some parties on the global Internet, though they may also engage in peering. An ISP may use a single upstream provider for connectivity, or implement [[multihoming]] to achieve redundancy and load balancing. [[Internet exchange point]]s are major traffic exchanges with physical connections to multiple ISPs. Large organizations, such as academic institutions, large enterprises, and governments, may perform the same function as ISPs, engaging in peering and purchasing transit on behalf of their internal networks. Research networks tend to interconnect with large subnetworks such as [[GEANT]], [[GLORIAD]], [[Internet2]], and the UK's [[national research and education network]], [[JANET]].