Different Network Devices

 Repeater:-  A repeater is the simplest facility used for network interconnection, whose major function is to receive a network signal from one LAN terminal cable segment and to regenerate and retransmit the signal as it is in its original strength over a one or more other cable segment. Basically repeater regenerates the strength of the signal before transmitting it.

Hub:-  A hub is a Networking Device that contains several ethernet ports that connects several computers. Connecting a hub to a network is very easy. You can simply connect a hub to your router, and then several computers to the hub.  Hubs work by broadcasting data to all computers that are connected to it. When a computer or program makes a request for information from another computer, the originating computer sends (broadcasts) the request to the hub. The hub will then brodcast the request to all computers that are connect to it. When the destination computer receives the request, it sends the information back to the hub. Once again the hub broadcasts the information to all computers, with only the requesting computer acting on the information.

Switches:-  Switches occupy the same place in the network as hubs. Unlike hubs, switches examine each packet and process it accordingly rather than simply repeating the signal to all ports. Switches map the Ethernet addresses of the nodes residing on each network segment and then allow only the necessary traffic to pass through the switch. When a packet is received by the switch, the switch examines the destination and source hardware addresses and compares them to a table of network segments and addresses. If the segments are the same, the packet is dropped ("filtered"); if the segments are different, then the packet is "forwarded" to the proper segment. Additionally, switches prevent bad or misaligned packets from spreading by not forwarding them.

Bridges:-  A bridge is a device that separates two or more network segments within one logical network (e.g. a single IP-subnet). A bridge is usually placed between two separate groups of computers that talk with each other, but not that much with the computers in the other group. A good example of this is to consider a cluster of Macintoshes and a cluster of Unix machines. Both of these groups of machines tend to be quite chatty amongst themselves, and the traffic they produce on the network causes collisions for the other machines who are trying to speak to one another. The job of the bridge is to examine the destination of the data packets one at a time and decide whether or not to pass the packets to the other side of the Ethernet segment. The result is a faster, quieter network with less collisions. The bridging code decides whether to bridge data or to drop it not by looking at the protocol type (IP, IPX, NetBEUI), but by looking at the MAC-address unique to each NIC.

Routers:- A router is equipment that creates a link between different networks or sub networks. Routers "route" data from a LAN to another router, then another router until the data reaches the destination. Routers are traffic cops, permitting only authorized machines to send data to the local network so that privacy of information is maintained. Also the router can keep a tab of network usage statistics, handle security issues and also keep a tab on the errors.

When you send an email to your pal on the other side of the country, it is the routing technology that makes sure that he or she gets the message and not every other computer that is connected online. Router directs the flow of traffic among networks.

Gateway:- A gateway is a node that allows you to gain entrance into a network and vice versa. On the Internet the node which is the stopping point can be a gateway or a host node. A computer that controls the traffic your network or your ISP (Internet Service Provider) receives is a node. In most homes a gateway is the device provided by the Internet Service Provider that connects users to the internet.
When a computer server serves as a Gateway node, the gateway node also operates as a firewall and a proxy server. A firewall is a system created to prevent unauthorized admission into a private network. A proxy server is located right between a client application such as a web browser and the real server. The proxy server sees if the client applications requests can be carried out by the real server

CSU/DSU:-  A Channel Service Unit/Digital Service Unit (CSU/DSU), sometimes called Data Service Unit, is a device that converts the digital signal format used on LANs into one used on WANs. Such translation is necessary because the networking technologies used on WANs are different from those used on

LANs. The CSU/DSU sits between the LAN and the access point provided by the telecommunications company.  Many router manufacturers are now incorporating CSU/DSU functionality into their products.

ISDN Adapters:- Integrated Services Digital Network (ISDN) is a remote access and WAN technology

that can be used in place of a Plain Old Telephone Service (POTS) dial-up link if it is available. The availability of ISDN depends on whether your local telecommunications service provider offers the service, the quality of the line to your premises, and your proximity to the provider’s location.

ISDN offers greater speeds than a modem and can also pick up and drop the line considerably faster.

Wireless Access Point:- Wireless access points (APs) are a transmitter and receiver (transceiver)

device used to create a wireless LAN (WLAN). APs are typically a separate network device with a built-in antenna, transmitter, and adapter. APs use the wireless infrastructure network mode to provide a connection point between WLANs and a wired Ethernet LAN. APs also typically have several ports

allowing a way to expand the network to support additional clients.

Modems:- Modem, short for modulator-demodulator is an electronic device that converts a computer’s digital signals into specific frequencies to travel over telephone or cable television lines. At the destination, the receiving modem demodulates the frequencies back into digital data. Computers use modems to communicate with one another over a network.
The modem has significantly evolved since the 1970s when the 300 baud modem was used for connecting computers to bulletin board systems (BBSs). Each bit, represented digitally by a 1 or 0, in this original version was transmitted as a specific tone. The receiving modem responded with its own dedicated frequencies so that the two could “talk at the same time.” The technical term for this type of modem is asynchronous.

Transereceivers (Media Converters):- The term transceiver does describe a separate network device, but it can also be technology built and embedded in devices such as network cards and modems. In a network environment, a transceiver gets its name from being  both a transmitter and a receiver of signals—thus the name transceivers. Technically, on a LAN, the transceiver is responsible for placing signals onto the network media and also detecting incoming signals traveling through the same wire. Given the description of the function of a transceiver, it makes sense that that technology would be found with network cards.

Firewalls:- A firewall can either be software-based or hardware-based and is used to help keep a network secure. Its primary objective is to control the incoming and outgoing network traffic by analyzing the data packets and determining whether it should be allowed through or not, based on a predetermined rule set. A network's firewall builds a bridge between an internal network that is assumed to be secure and trusted, and another network, usually an external (inter)network, such as the Internet, that is not assumed to be secure and trusted

August 06, 2012 Tags : Technology