In telecommunications, the term routing refers to the pathfinding of information or data streams, from the source to its destination. It is mostly used in the context of data networks and describes the route taken via individual network nodes (routers) for the transmission and delivery of data packets. In order to achieve this, the router knows either individual links or complete network topologies and chooses the best network node to forward the data packet on to next, based on its destination address and certain criteria. Routing algorithms and protocols are used to reach the decision. The term routing is also used for the inbound and outbound processing of telephone calls in telephone systems.