Routers

Routers connect networks with identical protocols or addressing mechanisms. The main task of a router is to perform the routing for the transmission of data packages from the sender to the recipient. Routers are able to effectively reduce the data traffic between individual networks by using different algorithms. The dynamic routing leads to a load reduction for the entire network. If the router has several alternative routes to the target station available, it will always choose the optimum way depending on the current load on the network and the expected costs.

In contrast to the switches which forward the packets on the basis of layer 2 (e.g. ETHERNET), the routers operate on layer 3 (e.g. IP). While the switches forward the packets on the basis of the MAC addresses, the routers evaluate the contained IP addresses. For this purpose, when receiving a data package a router first has to remove the outer telegram frame in order to be able to interpret the addresses of the inner protocol and then it has to re-assemble the data package again before forwarding it. This results in higher latency periods (time of stay) of the data within the router itself. The investigation of a data package necessary for routing makes clear that a router has to be able to process all network protocols to be routed over this router. Due to the increasing spread of heterogeneous networks, today often routers are used which are able to support several network protocols (e.g. IP, IPX, DECnet, AppleTalk) instead of special IP routers. Such routers which are able to process several network protocols are called multi-protocol routers. Some routers additionally have a bridge functionality (bridge routers, Brouters) which enables them to also forward the data packages of protocols a router cannot interpret or which do not support the routing function (e.g. NetBios).