lanwan network devices

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Vocational Training Course-2008

8LAN/WAN NETWORK DEVICES

Computer network consist of different devices such as router, hub, switch, gatewayand others. Without these network devices data cannot be transmitted from onecomputer to another in a LAN or WAN network. These devices link up all the local

and remote network segments with each other to make data communication fromone segment to another. The two important devices of a big network are routers andswitches. A computer network with good infrastructure with properly placed andconfigured network devices such as routers, switches etc. are helpful in reducing theoverall operational cost, improve the performance, manageability and reliability.

LAN Devices

Hub

A hub is a networking device, which is used to connect the two segments of a wired

network. In star topology, every computer is directly connected with the hub. Incase of any fault in the hub, the data communication in the network computersstops. In an Ethernet-based network a hub is a central device that is used toconnect all the computers with each other.

A hub has multiple ports such as 6, 8, 16 and 24 etc. When data packets arereached at hub, they are broadcasted to all the computers unlike a switch and onlythe destined computer receives the data. When you want to connect more thancomputers with each other a hub or switch is required in a local area network. Thereare two types of a hub passive hub and active hub.

LAN Card

LAN card, network interface card or NIC is used to join the computers in a network.A NIC card is installed in any available PCI port inside the computer. A unique MAC(Media Control Access) address is assigned to LAN card. A MAC address isconsists of two portions manufactures id and the card id (PROM on the networkinterface card holds the addresses). LAN card operates on the physical and datalink layer of the OSI model. A LAN card usually has twisted pair, BNC and AUIsockets where the Ethernet cables are connected.

Switch

AIR GWALIOR C.P.Harikumar-2008


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A network switch performs the same functionality in a network as a hub except adifferent that switch does not broadcast the data packets to all the computers in anetwork like a hub. A network switch has multiple ports like 4, 8, 16 and 24 etc. Allthe computers in a wired network are directly connected with the switch throughEthernet cable. Switches limit the traffic to and from each port and all the devices

connected to the switch has maximum available bandwidth. Switch doesnt providethe built-in firewall capabilities like the routers. In the telecommunication and packetswitched infrastructure switches play an important role. They transmit the datatowards its destination based on the IP address.

Gateway

A gateway can be hardware or software and it acts as a bridge between twonetworks. A gateway is an entrance point of a network. A gateway connects a LANwith internet. A router acts as a gateway device in a network. In big networks, acomputer server, which acts as a gateway, also acts as a proxy server and a firewall

server. A gateway computer is usually attached with the router and switch.

Repeater

A repeater is a network device that is used to retransmit the weaker signals in anetwork. A repeater receives the signals on the electromagnetic or opticaltransmission mediums. Repeater removes the unwanted noise from the incomingsignals. A series of the repeaters is used to amplify the signals in the big network.The can also relay the messages between subnetworks that use different protocolsbut a repeater cant perform intelligent routing like the routers.

WAN Devices

Routers

A router is a network communication device that is used to connect two or morelogically and physically different networks. A router can be used to connect a LAN-to-LAN, LAN to WAN and LAN to internet. A router acts as a post office wheresorting and distribution of the posts (packets in case of routers) is done. A routerworks on the basis of an IP address. Every router has built-in operating systemknown as IOS. A router works on the network layer of the OS model and it routes the

data towards the optimal path. Router uses the header information of the packetsand forwarding table to define the best shortest possible path of the data.

ISDN Adaptors

ISDN (Integrated Services Digital Network) is a data communication method and it isused over the regular telephone lines. To use the ISDN lines, you need to installadd-on adapters known as ISDN terminal adapters. ISDN Terminal Adapter workslike a digital modem i.e. it converts the signals from digital to analog and vice versa.ISDN Terminal adapter is plugged into the serial port of the system. Some ISDNadapters have the feature of switching between digital and analog modes.

CSU/DSU



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CSU/DSU stands for channel service unit and data service unit. CSU is used toconnect a terminal to a digital line. DSU is used to perform the protective anddiagnostic functions of the telecommunication line. CSU/DSU is a network device ofthe size of an external modem. The Channel service unit receives and transmits thesignals from the wide area network line. CSU/DSU are two separate devices and

they are sometimes used in conjunction with the T1 LAN cards.

Bridges

A bridge is a network communication device that is used to connect two segments ofa LAN that uses the same protocol. Bridge is like a router but it doesnt analyze thedata before sending. A bridge operates at the data link layer of the OSI model and itcan be used to connect the physically different networks and the networks that usethe different protocols such as Ethernet and Token Ring.

Modems

A modem is communication device that performs two different functions such asmodulation and demodulation i.e. it converts the digital data into analog and analoginto digital. The faster types of the modems are used by the internet such as DSLmodem, cable modem and optical modems. The features like BPS, auto answer,data compression, voice/data, fax capability and flash memory distinguish onemodem from the other.

Brouter

Network bridge and router combined together to form a device known as brouter.

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