Network2/Concept/Router

Routers are network nodes which forward encapsulated payload messages by receiving link-layer messages containing encapsulated payloads over one link and by decapsulating, inspecting, and potentially re-encapsulating the received payload for retransmission along a (usually) different link in the hopes of bringing the encapsulated payload closer to its destination. Routers permit the creation of internetworks from simpler networks.

The route along which a message is sent as it travels from its source to a destination is called a path. A message which is sent to one or more destinations along one or more routes is said to have been routed along a multipath.

(Alternately, if internetworks are networks of nodes (which are networks) joined by media which are themselves unions of links, peering agreements, and transit agreements, then routers are the interfaces attaching these nodes to their media.)