 lines. The switching process is based on information gathered through a routing process. A switching element might consult a table to determine, based on the number dialed, the most cost-effective trunk over which to forward a call. This switching process is relatively straightforward compared to the type of path determi- nation that IP routers in the Internet might use, which can be very complex. Routing, on the other hand, involves moving information from a source to a destination across an internetwork, which means moving information across net- works. In general, routing involves at least one intermediate node along the way, and it usually involves numerous intermediate nodes and networks. This implies an understanding of hierarchical addressing structure and switching. A router per- forms two basic activities: determining the optimal path and transporting informa- tion through an internetwork. Routing algorithms are necessary to initialize and maintain routing tables. Routing algorithms work with a whole slew of informa- tion, called metrics, to determine the best path to the destination. Some examples of the metrics that a routing algorithm might use are path length, destination, next- hop associations, reliability, delay, bandwidth, load, and communication cost. A router could use several variables to calculate the best path for a packet, to get it to a node that is one step closer to its destination. The route information varies depending on the algorithm used, and the algorithms vary depending on the rout- ing protocol chosen. Most manufacturers today support the key standards, including Routing Information Protocol (RIP), Open Shortest Path First (OSPF), Intermediate System to Intermediate System (IS-IS), Enhanced Interior Gateway Routing Proto- col (EIGRP), Border Gateway Protocol 4 (BGP4), and Multiprotocol Label Switch- ing (MPLS). Network engineers generally decide which of these protocols to use. Routing protocols can also be designed to automatically detect and respond to net- work changes. (Prot