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Function A router acts as a junction between two or more networks to transfer data packets among them. A router is different from a switch. A switch connects devices to form a local area network (LAN). One easy illustration for the different functions of routers and switches is to think of switches as neighbourhood streets, and the router as the intersections with the street signs. Each house on the street has an address within a range on the block. In the same way, a switch connects various devices each with their own IP address(es) on a LAN. However, the switch knows nothing about IP addresses except its own management address. Routers connect networks together the way that on-ramps or major intersections connect streets to both highways and freeways, etc. The street signs at the intersection (routing table) show which way the packets need to flow. So for example, a router at home connects the Internet service provider's (ISP) network (usually on an Internet address) together with the LAN in the home (typically using a range of private IP addresses, see network address translation (NAT)) and a single broadcast domain. The switch connects devices together to form the LAN. Sometimes the switch and the router are combined together in one single package sold as a multiple port router. In order to route packets, a router communicates with other routers using routing protocols and using this information creates and maintains a routing table. The routing table stores the best routes to certain network destinations, the "routing metrics" associated with those routes, and the path to the next hop router. See the routing article for a more detailed discussion of how this works. Routing is most commonly associated with IP, although other less-popular routed protocols are in use. History The first router was created at Stanford University by a staff researcher named William Yeager in January of 1980. His boss at the time told him that he was the "network guy" and to find a way to connect the computers in the computer science department, medical center and department of electrical engineering. He first wrote a network operating system and routing code to run on a DEC PDP-11/05. He used Alan Snyder's Portable C compiler but it generated too much code so he modified the compiler to improve the code generators. That still wasn't good enough so he wrote an optimizer for PDP-11/05 assembler that reduced the code size further. Types of routers
Manufacturers of routers There are a number of manufacturers of routers including: "Software" routers With the proper software and 2 or more network cards, ordinary PCs, even old ones, can be made into routers. Most Unix-like operating systems include all necessary software to perform routing: The list includes only some examples that specialise in routing. NAT has been a built-in function of the Linux kernel since version 1.3. Originally an option that needed to be compiled into the kernel, most modern versions have NAT as a module that merely needs to be turned on. See List of Linux distributions, BSD, Unix-like for more. Other solutions include: See also | ||||||||||||
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