Routers – What They Are and What They Do
A router is a device that joins multiple networks together, forwarding packets of data along the networks to the computers connected to it. The point where two networks connect, at the gateway, is where the router is located. When a single data packet comes in from one network, the router uses software to direct the packet to its destination by reading the address information located within the packet. The internet itself, the largest network that exists in the world, has all its information directed through routers. Routers have routing tables inside them which enables them to filter both incoming and outgoing traffic based on IP addresses. The size and function of the router differs from network to network, depending on the network's requirements. So, it is difficult to identify a router by its physical appearance.
The two main types of routers, wired and wireless, usually share a number of defining characteristics. They have one or multiple network interface controllers (NICs) to support Fast Ethernet or Gigabit Ethernet. They also have wireless network interface controllers (WNICs) as separate chips on their circuit boards. Often, routers will have an Ethernet switch to support Fast Ethernet or Gigabit Ethernet. Routers may also include one or two USB ports for external devices such as printers or hard drivers. While wireless routers perform the same function as wired routers, but they are not directly connected to the network via a wired link. As such, wireless routers also have extra added levels of embedded security within them so they can function as wireless access points.
The history of the router goes back to 1972 when they were first used by a group of computer networking researchers called the International Network Working Group. At the time, routers were called "gateways" and this research group's aim was to consider the technical issues involved in connecting different networks. The function of the device back then was much different than today. Their router connected dissimilar networks, it was connectionless, and it left traffic direction entirely up to the hosts (today, routers are responsible for reliably delivering traffic). Then, in 1975, the first true IP routers were developed. Six years later, in 1981, researchers at MIT and Stanford independently developed multiprotocol routers. Although today, virtually all networking uses TCP/IP (Transmission Control Protocol/Internet Protocol), multiprotocol routers are still used in smaller percentages. Some of the largest router manufacturers today are Cisco Linksys, Juniper, Redback, 3Com, Nortel (Bay Networks), Lucent, and HP.