WLAN Wireless LAN WiFi Wireless Fidelity A wireless

WLAN (Wireless LAN) • Wi-Fi (Wireless Fidelity) – A wireless technology that connects computers without cables • Access Point (AP) – A device (base station) that connects wireless devices together – Usually connected to a wired-network • Hotspot – The area covered by wireless access points

Network Interface Card (NIC) NICs are printed circuit boards that are installed in computer workstations. They provide the physical connection and circuitry required to access the network. They provide the physical connection between the network cable and the workstation. In addition, they possess the circuitry necessary to gain access to the network.

Network Interface Card In the past, computers did not come with a pre-installed NIC. However, most modern computers are shipped with NIC already installed and ready to be connected to a network. Each NIC has a distinctive 6 -byte hardware address that identifies the workstation within a segment, such as Ethernet 00 -00 -A 2 -9 A-4 E-10 called as MAC address (or Physical Address). Each NIC has at least one connection port where the network cable is attached. Only one port may be used at any one time. The NIC formats information from the workstation so that it can be transmitted across the network.

Repeaters As a signal travels through a transmission medium, it encounters resistance and gradually becomes weak and distorted. This loss in signal strength is called as “attenuation”. When signal is transmitted over long distance , at some point it become too weak and distorted to be received reliably. Repeaters are used to overcome this problem. Repeater is cconnectivity device used to regenerate and amplify weak signals, thus extending the length of the network. Repeaters perform no other action on the data. Repeaters are placed between transmitting and receiving devices on the transmission medium and they does not make any change in signal.

Hub is a device used to connect several computers together. It is also called as concentrator. It is basically multiport repeater. The basic function of a hub is to take data from one of the connected devices and forward it to all the other ports on the hub

Hub Hubs direct data packets to all devices connected to the hub, regardless of whether the data package is destined for the device.

Hub Most hubs are referred to as either active or passive. Active hubs regenerate a signal before forwarding it to all the ports on the device and requires a power supply. Passive hubs, which today are seen only on older networks, do not need power and they don’t regenerate the data signal.

Modem A modem is a device that makes it possible for computers to communicate over telephone lines. The word modem comes from Modulate and Demodulate. Because standard telephone lines use analog signals, and computers digital signals, a sending modem must modulate its digital signals into analog signals. The computers modem on the receiving end must then demodulate the analog signals into digital signals. Modem is a device which performs modulation and demodulation operations.

Modems can be external, connected to the computers serial port by an RS-232 cable or internal in one of the computers expansion slots. Modems connect to the phone line using standard telephone RJ -11 connectors By V. A. Pathan

Bridges are used to divide larger networks into smaller sections. Bridges connect network segments typically using the same communication protocol, passing information from one network to the other. Bridges break networks into separate segments and direct transmission to the appropriate segment much like a police officer directs automobile traffic. PORTS A B E F BRIDGE C D G H

Switch A connection device in a network that functions much like a bridge, but directs transmissions to specific workstations rather than forwarding data to all workstations on the network. It is a small hardware device that joins multiple computers together within one local area network (LAN). Rather than forwarding data to all the connected ports, a switch forwards data only to the port on which the destination system is connected.

Switch By forwarding data only to the connection that should receive it, the switch can improve network performance and reduce network congestion. Switches allow each workstation to transmit information over the network independent of the other workstations.

Routers link two or more different networks together. These networks can consist of various types of LAN segments, for example, Ethernet, token ring, or Fiber Distributed Data Interface (FDDI). Router work at network layer of OSI architecture. A router receives packets and selects the optimum path to forward the packet across the network. Routers contain internal tables of information called routing tables that keep track of all known network addresses and possible paths throughout the internetwork, along with cost of reaching each network. Routers sends packets to destination node based on the available paths and their costs.

Gateways A gateway is a device used to connect networks using different protocols. Gateways operate at the network layer of the OSI model in order to communicate with a host on another network. They are able to convert the format of data in one computing environment to a format that is usable in another computer environment.