Thursday, October 16, 2014

Explain Devices :Modems,Repeater,Hub,Bridge,Router,Gateway

Components of network:-
·        Modem is modulation and demodulation it will convert analog signal in to digital and digital signal into analog.
·        The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from light emitting diodes to radio.
·        The most familiar example is a voice band modem that turns the digital data of a personal computer into modulated electrical signals in the voice frequency range of a telephone channel.
·        These signals can be transmitted over telephone lines and demodulated by another modem at the receiver side to recover the digital data.
·        Modems are generally classified by the amount of data they can send in a given unit of time, usually expressed in bits per second (bit/s, or bps).
·        Modems can alternatively be classified by their symbol rate, measured in baud. The baud unit denotes symbols per second, or the number of times per second the modem sends a new signal.
·        A network device where the information flow is accumulated and then distributed various groups and users.
·        It can be used between users on the same to LAN and the users on different LAN also [local area network].
·        It serves as the central point where cables from all nodes come together.
·        HUBs are available in different shapes and size it also provides limited management facility
·        Dumb Hub (passive hub):- this type of hub only use for the data communication and there is no management facility.
·        Intelligent Hub (Active hub);- this type of hub used for communication and also decision making it also has management facility.
·        A device that supports LAN to LAN communication is bridge.
·        It will remember all the network addresses on both side of LANs and regulate the flow of traffic.
·        Network bridging describes the action taken by network equipment to allow two or more communication networks, or two or more network segments creating an aggregate network.
·        Bridging is distinct from routing which allows the networks to communicate independently as separate networks.
·        A network bridge is a network device that connects more than one network segment. In the OSI model bridging acts in the first two layers.
·        There are four types of network-bridging technologies: simple bridging; multiport bridging; learning, or transparent bridging; and source-route bridging.
·        Transparent bridging was originally developed by the Digital Equipment Corporation (DEC) in the 1980s.
·        Router interconnects two or more physical and logical network and work at network layer.
·        It distinguishes data packets according to protocol like, TCP/IP, FTP, HTTP etc.
·        It will remember matrices to determine the optimal path of workstation in computer network.
·        A router is a device that forwards data packets between computer networks, creating an overlay internetwork.
·        A router is connected to two or more data lines from different networks. When a data packet comes in on one of the lines, the router reads the address information in the packet to determine its ultimate destination.
·        Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey. Routers perform the "traffic directing" functions on the Internet.
·        A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it gets to its destination node.
·        A shared connection between LAN and a larger system such as mainframe computer or a large packet switching network whose communication protocols are different.
·        It usually is slower than bridge or a router, it is a communication of hardware or software.
·        It has its own processor and memory used to perform protocol conversion.
·        A gateway is a network point that acts as an entrance to another network. On the Internet, a node or stopping point node or a host (end-point) node.
·        Both the computers of Internet users and the computers that serve pages to users are host nodes, while the nodes that connect the networks in between are gateways.
·        For example, the computers that control traffic between company networks or the computers used by internet service providers (ISPs) to connect users to the internet are gateway nodes.
·        In the network for an enterprise, a computer server acting as a gateway node is often also acting as a proxy server and a firewall server.
·        A gateway is often associated with both a router, which knows where to direct a given packet of data that arrives at the gateway, and a switch, which furnishes the actual path in and out of the gateway for a given packet.

Difference Router v/s Modem
·        A router is used to connect two or more networks while a modem is used to connect to a phone line.
·        A router only connects to RJ45 connectors while modems need an RJ45 and an RJ11 for the phone line.
·        A router provides security measures to protect your network but a modem does not.
·        A modem is essential to connect to the internet while a router isn’t.

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