Router what it is

Quite often, the following generalized definition of a router is given in computer literature: “A router is a network layer device of the OSI reference model that uses one or more metrics to determine the optimal transmission path for network traffic based on network layer information.” From this definition it follows that the router is primarily necessary to determine the further path of the data sent to a large and complex network. The user of such a network sends his data to the network and indicates the address of his subscriber. And that’s all. Data passes through the network and at points with branching routes arrives at routers, which are just installed at such points. The router chooses the best future path. Which way is better is determined by quantitative indicators called metrics. The best path is the path with the least metric. The metric can take into account several indicators, for example, path length, travel time, etc. Routers are implemented in different ways. Routers are divided into devices of the upper, middle and lower classes. High-end, high-end routers are used to integrate enterprise networks. They support many protocols and interfaces, not only standard, but sometimes quite exotic. Devices of this type can have up to 50 ports of local or global networks. Using middle-class routers, smaller enterprise-wide networking is formed. The standard configuration includes two to three LAN ports and four to eight wide area network ports. These routers support the most common routing and transport protocols. The lower class routers are designed for local networks of divisions – they connect small offices with the network of the enterprise. Typical configuration: one LAN port (Ethernet or Token Ring) and two WAN ports, designed for low-speed leased lines …

Routers for core networks and remote offices have a different architecture, because they have different functional and operational requirements. Core network routers must be extensible. Branch office local area routers, for which, as a rule, a fixed configuration of ports is pre-installed, contain only one processor that controls the operation of three or four interfaces. They use approximately the same protocols as core network routers, but the software is more aimed at facilitating installation and operation, since most remote offices do not have enough qualified network service specialists.

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