Archive for the ‘Networking Technology’ Category
November 19th, 2009 | 
Author: Computer networks are like snowflakes one two are the same. The basic components of computer networks All computer networks include some combination of the following applications and a network that will support the data traffic between the end stations. A computer network all share common devices, functions, and features,
Servers:
Servers are computers that hold shared files, programs, and the network operating system. Servers provide access to network to all the users of the network. There are many different kinds of servers, and one server can provide functions. File servers are located with files accounts and a record of the access rights of users or groups of users on the network. The server provides a shareable virtual disk to the users. File mapping schemes are implemented to provide the virtual ness of the files.
Clients:
Clients are computers that access and use the network and shared network resources. Client computers are basically the customers of the network as they request and receive services from the servers.
Transmission Media:
Transmission media are facilities used to interconnect computers in a network such as twisted-pair wire, coaxial cable and optical fiber cable. Transmission media are sometimes called channels links or lines.
Shared Data:
Shared data are data that files servers provide to clients, such as data files, printer access programs and email. Shares printers and peripherals are hardware resources provided to the users of the network by servers. Resources provided include data files printers software any other items used by clients on the network.
Local Operating and Networking Operating Systems:
A local operating system allows personal computers to access files print to a local printer and have and use or more disk and CD drives that are locate on the computer. The network operating system is a program that runs on computers and servers that allows the computer to communicate over a network. The NOS provides services to clients such as log in features, password authentication, printer access, network administration functions, and data file sharing. Some of the more popular network operating systems are should also provide unique feature. Sets and handoffs, land based to satellite handoff, registration.
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Network topology describes the layout or appearance of a network, that is, how the computers, cables and other components within a data communications network are interconnected, both physically and logically. The physical topology describes how the network is actually laid out, and the logical topology describes how data actually flow through the network. In a data communications network, two or more stations connect to a link, and one or more links form a topology. Topology is major consideration for capacity, cost, and reliability when designing a data communications network.
Star Topology and Bus Topology:
A star topology is a multipoint data communications network where remote stations are connected by cable segments directly to a centrally located computer called a hub, which acts like a multipoint connector. In essence, a star topology is simply a multipoint circuit comprised of many two-point circuits where each remote station communicates directly with a centrally located computer. A bus topology is a multipoint data communications circuit that makes it relatively simple to control data flow between and among the computers because this configuration allows all stations to receive every transmission over the network. With a bus topology, all the remote stations are physically or logically connected to a single transmission line called bus.
Ring Topology and Mesh Topology:
A ring topology is a multipoint data communications network where all stations are interconnected in tandem to form a closed loop or circle. A ring topology is sometimes called a loop. Each station in the loop is joined by point-to-point links to two other stations. Transmissions are unidirectional and must propagate through all stations in the loop. In a mesh topology, every station has a direct two point communications link to every other station on the circuit. The mesh topology is sometimes called fully connected. Advantages of a mesh topology are reduced traffic problems, increased reliability, and enhanced security.
Hybrid Topology:
A hybrid topology is simply combining two or more of the traditional topology to form a larger, more complex topology. Hybrid topologies are sometimes called mixed topology. Other hybrid configurations include the star ring, bus ring, and virtually every other combination you can think of.
Network are generally classified by size, which includes geographic area, distance between stations, number of computers, transmission speed, transmission media, and the network’s physical architecture. When two or more networks are connected together, they constitute an inter network or internet. An internet is sometimes confused with the internet. The term internet is a generic term that simply means to interconnect two or more networks, whereas internet is the name of a specific worldwide data communications network.
Local Area Network (LAN):
LAN are typically privately owned data communications networks in which 10 to 40 computers users share data resources with in one or more file servers. LANs use a network operating system to provide two-way communications at bit rates typically in the range of 10 MBPS to 100 MNPS and higher between a large variety of data communications equipment within a relatively small geographical area, such as in the same room, building, or building complex. LANs were designed for sharing resources between a wide range of digital equipment, including personal computers, work stations, and printers.
Wide Area Network (WAN):
WAN are the oldest type of data communications network that provide relatively slow-speed, long-distance transmission of data, voice, and video information over relatively large and widely dispersed geographical areas, such as a country or an entire continent. WANs typically interconnect cities and states. WANs typically operate at bit rates from 1.5 MBPS to 2.4 GBPS and cover a distance of 100 to 1000 miles. WANs may utilize both public and private communications systems to provide service over an area that is virtually unlimited.
Metropolitan Area Network (MAN):
MAN is a high-speed network similar to a LAN except MANs are designed to encompass larger areas, usually that of an entire city. Most MANs support the transmission of both data and voice and in some cases video. MANs typically operate at speeds of 1.5 MBPS to 10MBPS and range from miles to a few hundred miles in length. A MAN generally uses only one or two transmission cables and requires no switches. A MAN can be owned and operated entirely by a single, private company, or it could lease services and facilities on a monthly basis from the local cable or Telephone Company.
The basic principle behind a modem transmitter is to convert information received from the DTE in the form of binary digits to digitally modulated analog signals. The reverse process is accomplished in the modem receiver.
Serial Interface Circuit and Modular Circuit:
Interface the modem transmitter and receiver to the serial interface. The transmit section accepts digital information from the serial interface, convert it to the appropriate voltage levels, and then the direct the information to the modulator. The receive section receives digital information from the demodulator circuit, converts it to the appropriate voltage levels, and then directs the information to the serial interface. Receive digital information from the serial interface circuit. The digital information modulates an analog carrier, producing a digitally modulated analog signal. Inessence, the modulator converts digital changes in the information to analog changes in the carrier.
Bandpass Filter and Equalizer Circuit:
There are bandpass filter and equalizer circuits in both the transmitter and receiver sections of the modem. The transmit bandpass filter limits the bandwidth of the digitally modulated analog signals to a bandwidth appropriate for transmission over a standard telephone circuit. The receive bandpass filter limits the bandwidth of the signals allowed to reach the demodulator circuit, thus reducing noise and improving system performance. Equalizer circuits compensate for bandwidth and gain imperfections typically experienced on voice band telephone lines.
Telco Interface Circuit & Carrier and Clock Generation Circuit:
The primary functions of the telco interface circuit are to match the impedance of the modem to the impedance of the telephone line and regulate the amplitude of the transmit signal. The interface also provides electrical isolation and protection and serves as the separation point between subscriber equipment and telephone company-provided equipment. The telco line can be two-ire or four wires, and the modem can operate half or full duplex. When the telephone line is two wires, the telco interface circuit would have to perform four-wire-to-two-wire and two-wire-to-four-wire conversions. The carrier generation circuit produces the analog carriers necessary for the modulation and demodulation processes. The clock generation circuit generates the appropriate clock and timing signals required for performing transmit and receive function in an orderly and timely fashion.
Computer networks can be represented with two basic network models: peer-to-peer client/server and dedicated client/server. The client/server method specifies the way in which two computers can be communicate with software over a network. With client/server concept, a computer acting as a client initiates a software request from the client. The sever computer might then act as a client and request services from another computer.
Peer-to-peer Client/ Server Network:
A Peer-to-peer client/server network is one in which all computers share their resources, such as hard drives, printers, and so on, with all the computers on the network. Therefore, the peer-to-peer operating system divides its time between servicing the computer on which it is loaded and servicing requests from the other computers. In a peer-to-peer network, there are no dedicated servers or hierarchy among the computers. Each computer in the network can function as a client and/ or a server, and no single computer holds the network operating system or shared files. The users at each computer determine which data on their computer are shared with the other computers on the network.
Dedicated Client/ Server Network:
In a Dedicated client/server network, one computer is designated the server, and the rest of the computers are clients. As the network grows, additional computers can be designated servers. Generally, the designated servers function only as servers and are not used as a client or work station. The servers store all the network’s shared files and applications programs, such as word processor documents, compilers, database applications, spreadsheets, and the network operating system. Client computers can access the servers and have shared files transferred to them over the transmission medium .in some client/server networks; client computers submit jobs to one of the servers. The server runs the software and completes the job and then sends the results back to the client computers. In this type of client/server network, less information propagates through the network than with the file sever configuration because only data and not applications are transferred between computers.
