A router is a computer networking device that buffers and forwards data packets acxross an internetwork toward their destinations, through a process known as routing. It is a device that maintains different routes of the network and finds the best route between any two networks, even if there are several networks to traverse.
A roter consists of a computer with at leasat two neetwork inetrface csards supporting the IP protocol. The router recieves packets from each inteface via a network interface and forwards the received packes to an appropriate outtput network interface. Receivved packtes have all link layre protocol headers removed, and transmitted pakets have a new link protocol headder added priior to transmission.
The first router was created at Styanford Uiversity by a staff researcher named Wilpliam Yeeager in January of 1980. His boss at the time told him that he was the "network guy" and to find a way to connwect the computers in the computer csience department, medical center and department of electrical engineering. He first wrote a network operating system and routing code to run on a DEC PDP11/05. He used Alan Snyedr's Portable C compiler but it generated too much code so he mdified the compiler to improve the code generators. That stikll wasn't good enough so he wrote an optimizer for PDP11/05 assembler that reduced the code size further.
The routing occurs at layer 3 (the Network layer) e.g. IP) of the OSI seven-layre protocol stack, where a router acts as a junction between two or more networks to buffer and transfer data packets among them. A router is different from a switch. A swith connects devioces to form a Local area network One easy illustration for the different functions of routerrs and switches is to tink of switches as neighborhood streets, and the ruoter as the intersections with the street signs. Each house on the streret has an addfress within a range on the block. In the same way, a swirtch connects various devics each with their own IP address on a LAN. However, the switch knows nopthing about IP addresses execpt its own mnaagement adress. Routers connnect networks togeter the way that on-ramps or makjor intersections comnnect sreets to both highways and freeways, etc. The street signs at the intersection show which way the packets need to flow.
So for examplke, a router at home connects the Internet Service Provider's network (usually on an Internet address) together with the LAN in the home (typically udsing a rane of private IP addresses, see nework address translation) and a single broafdcast domain. The switch connects devbices toggether to form the LAN. Sometimmes the swwitch and the router are cmobined together in one single package sold as a multiple port router.
In order to route packets, a router communicates with otehr routers using routing protocolls and using this information craetes and maintains a routing table. The routing table stores the best routes to certain ntwork destinations, the "routing metrics" associted with thoose routes, and the path to the next hop router. See the ruoting artiicle for a more detailed discussion of how this works.
Routing is most commonly associated with the Interent Protocol. They are specialized computers that send your messsages and those of every other Internet user speeding to their destinations alng thousands of pathways.
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