computer networking note.

Introduction
Networking is the process of connecting one computer terminal with the others. A communication system that supports
many users can be called a Network or we can say network is a communication system, which interconnects many users who have something in common, either with respect to the type of data being sent or to the geographic areas that the users cover. Networks can be sued between people, between people and computers, between computers and equipment or between computers, Today, organizations use networks in all possible ways. Depending on the application, the network needs different speed, degree of reliability, and cost.
    One of the largest networks in the world is at the National Aeronautics and Space Agency (NASA). This network combines all of the worldwide space tracking stations, the NASA research facilities, and the NASA operational offices. Data from any location can be instantly sent to any other, as can memos, messages, and conversations.

Computer Networks:

           Multiple nodes of computers, which are connected with each other, are called computer network, A computer network is created when several computers and terminals include Microcomputer, Minicomputers,  Medium scale computers & large computers. Each computer in a network can have its own processing capabilities and can also share computer hardware, programs, software and data files.
           Computer Network is an interconnection between two or more than two computers through physical component and logical component. These components are as follows:

                    #        Network Typologies
                    #        Cabling
                    #        Network Interface cards
                    #        Protocol
                    #        Hum/Switches
                    #        Modem (For Cyber Networking)

            Due to tremendous impact of computers and computer networks on society during the past decade, this period is called 'Information Age'. The information age is equally dependent on the computer and network. The network exists to meet one goal namely, the transfer and exchange of data between the computers and terminals.
            A Network allows may users to share a common pathway to communicate with each other whereas a computer network is a number of computers (usually called terminals)interconnected by one or more transmission paths. The design and installation of a network involves many considerations.

What is Local Area Network?
               Computer Networks are classified to different types based upon the geographical area that they span into:
      1.     Local Area Network (LAN)
      2.     Metropolitan Area Network (MAN)
      3.     Wide Area Network (WAN)

Local Area Network (LAN):
         

               A logical Area Network (LAN) is that where two or more computers directly linked within a small well-defined area such a room, office building, or a campus. A LAN can be made up of only microcomputers or any combination of microcomputer and large system.  Main benefit of a LAN is the reduction of hardware and software cost because user an share several computers, peripheral devices such as HDD, modem, and LAN platform software. Another benefit is that the user can share the same data.
               One mos LANs, cable connect the LAN by linking the network cards that reside within each computer or printer on the network. We talk about situations where cable is not the means of connections "wireless networks. LAN is a system in which linked computers and peripheral services, CD-ROMs, and /or the use of group scheduling programs and e-mail.
                Famous LANs available for microcomputers use include, Ethernet, Novell, PCs network etc. they vary in type and number of computers that may be connected the speed at which data may be transferred, and the type of software used to control the network.
                 A LAN generally consists of the following:
                 1.    Two or more computers.
                 2.    A diameter of not more than few kilometers
                 3.    Software to control the operation of the computers.
                 4.    Peripheral devices such as modem, HDD etc.
                 5.    C0-axial or fiber optic cables are usually used to connect the computers and other devices.
                 6.    A plug in board to handle the data transmissions.

                  The length of cable connecting to computer through a LAN also varies. Most permit cables of about one thousands feet, but the same permit cables of several miles to be used. The speed of data transfer range from several thousand bit per second to 10 million BPS.
                   A private network within a range of 10 kilometers owned and controlled by a single organization. Local Area Network has the following main characteristics.

a.A total data rate of at least several mbps.
b.Complete ownership by a single organization.
c.The connections between the workstations are usually distances of a few hundred feet, up to several thousand feet.
d. The LAN transmits data between user stations and computers (some LANs transport voice and video images as well).
e.The LAN transmission capacity is usually greater than that of a Wide Area Network; typical bit rates range from 1Mb/s to 20Mb/s.
f.The LAN channels is typically privately owned by the organization using the facility.

With a LAN, you can do all of the following:
  i.      Perform file-management tasks.
          *       Share files
          *       Transfer files
          *       Share application
  ii.      Share peripheral devices
          *        Printers
          *        CD-ROMs
          *        Scanners
          *        Fax Modems
          *        Tape drivers
  ii.Interact with other user on the network
          *         Schedule group meetings
          *         Send and receive e-mails
          *         Hold electronic meetings
          *         Play network games.

what is Metro Area Network (MAN)?
   

A MAN is a Network that is larger than a LAN. it is called Metropolitan since it normally covers the area of a city. Cable Televisions (CATV) networks are examples of Metro Area Networking for television distribution. It is a new physical network technology that operates at high speeds (usually hundreds of megabit per second through several gigabits per second) over distance sufficient for a metropolitan area.

        A MAN is a network that covers an entire city, but uses LAN technology. Cables Television (CATV) networks are examples of analog Man's for television distribution. The Man's we are interested in are digital and are intended to connect computers together, not televisions sets, although some of them may use broadband coaxial as the transmission medium. Networks come in range of sizes. Your network can start small, and then grow with your organization.

        It is a new physical network technology that operates at high speeds (usually, hundreds of megabit per second through several gigabits per second) over distances sufficient for a metropolitan area.

What is Wide Area Network?
                 A wide Area Networking is a two or more geographically isolated computer, linked by communication facilities such as telecommunication or microwave relays. In other words one of the most significant aspects of a Wide Area Networking while comparing it with freedom of local area network is the involvement of public telecommunications authority. WAN is usually limited to use by large organizations and government agencies due to high costs involved in building and maintaining them.

                  A Wide Area Network (WAN) typically consists of 2 or more LANs. The computers are farther apart and are linked by telephone lines, dedicated telephone lines, or radio waves. The Internet is the largest Wide Area Network in existence.

                   In other words one of the most significant aspects of a Wide Area Networking while comparing it with freedom of local area network is the involvement of public telecommunications authority. WAN usually limited to use by large organization and government agencies due to high costs involved in building and maintaining them.

   

A Wide Area Networking is extensions of a data network that uses telecommunication links to connect to geographically separated areas. Wide Area Network is also called WAN. WAN coves worldwide using Satellite as the transmission Medium.

Internet (Public) and Internet (Private) are the examples of Wide Area Network.

The WAN in contrast to the LAN has got the following features:

1.It typically spans entire countries

2.It has data rates below 1 Mbps.

                                                3.It is owned by multiple organizations ( the carrier owns the          communications subnet and numerous clients own the hosts.

                                                      4.Channels are usually provide by an inter exchange carrier (such as     MCI and At&T), at a monthly cost for leased lines and usage cost for dial-up lines.                                     5.Channels are relatively slow.

6.Channels are relatively error prone (if using conventional telephone circuits)

What is Peer-to-Peer Network?

         Peer-to-Peer networks represent a new and entirely different concept in networking than client-server networks. Rather than giving every computer on the network a central storage ground, Peer-to-Peer networking connects a group of totally independent computers. Each computer generally keeps its applications on its own hared disk so that if something happens to the network, it simply breaks down into a group of individual yet functional computers. If one work station goes down, life can go on for the rest of the network if all users keep their needed files at their down, life can go on for the rest of the network if all network enables very workstation to lead a double life: to be a workstation and file server.

                                                            Peer-to-Peer Network

                 Peer-to-Peer networks give their users many of the same capabilities that client server networks do. Each user decides what capabilities and peripheral devices he or she will share with the rest of the network and then shares them. You can share things selectively, saying perhaps, "Accounting gets to use the C drive and personnel gets to use the printer," and you can attach passwords to your resources so that unauthorized people can't access them. On the subject of sharing resources, remember that because important information on a Peer-to-Peer LAN is distributed throughout the network, you 'll have to leave networked machines on and logged on to the network as long as anyone is working who needs the information on those machines. 

                      Peer-to-Peer to networks is a form of micro Computer based network in the sense that the entire computer in network is peer, equal "buddies". All of them can act as a network resource, providing file, printer and even disk storage to the others, At the same time, all are also capable of working on their own, because thy have internal resources-disk storage, sufficient memory and processing power to act as stand alone computers.

                          Peer-to-Peer to network are recommended for small groups of five to ten workstation located in the same area, as in small office. Although they do not offer the complication of large networks in terms of security and centralized management. Peer-to-Peer to networks offset their limitations with ease installation, relatively low cost and ease of administration.

                         In a Peer-to-Peer network, there is no central authority figure, no network administration who handles security, user accounts, password, management and so on. Although there might well be one individual who knows more about networked computer than anyone else and so becomes the network counselor through either design or default. The main advantage is that Peer-to-Peer network are not inexpensive, but they are also easy to implement. Each computer in the network simply needs a network card that enables it to communicate with the other, TV type coaxial or telephone type twisted pair wiring to link it with its peer, and an operating system such as Windows '98 or Windows NT workstation, that has been built to support peer to peer networking. Disadvantage of peer-to-peer networks are limited in size and scope and they are not designed with security in mind. Each user must responsibility for the security and management of his or her own machine.

How to judge Peer-to-Peer packages ?
          When shopping for a peer-to-peer network, you should keep three things in mind:

*               How good are its communication abilities?
                        Most Peer-to-Peer packages include their own e-email and chat capabilities, allowing both e-mail and real-time communications. A good package provides users with a list of other users available for hats and has both single-mode and ulti-mode chat utilities.

*              How capable is its resource sharing?
                       Although peer-to-peer network often expect workstation to keep its own applications on file, you may prefer to locate some applications centrally and let people pick them up from another machine. You'll also be sharing devices such as drives, CD-ROM, and printers. The best packages notify users when a workstation with shared resources leaves the network.

*              How suitable is if for small-office use (since that's likely what you'll be using it for?)
                      Because peer-to-peer networks rarely have network managers, you'll want a network that is as easy to control as possible. A good peer-to-peer should be easy to install and set up, and have good print and file management tools to control shared resources. Although peer-to-peer networks are not famous for their security, you'll also want some way of controlling access to shared resource.

Weighing the Advantages of using a Peer-to-Peer network:
           At first glance, client-server networks seem to have all the advantages. when you look again, however, you discover that isn't necessarily the case. For small networks, peer-to-peer has a number of advantages:
*         It doesn't require a dedicated workstation.
*         It's an easy way to connect and share information on the workstations that you already have in your              office.
*         It's cheaper than duplicating your purchases of printers, CD-ROMs etc. for every person in the                    office, and probably more efficient for printer sharing than products such as print buffers and physical            print spoolers.
*         It costs less than a server-server LAN and doesn't require a degree in engineering to set up and                    administer.

In short, peer-to-peer networking does not offer the flexibility or the complete security of a file server workstation relationship, but for a small installation it will probably more than fit the bill.

What is Client/Server network?

Client/Server Network:

           

Client/Server networks are for more powerful and wide-ranging than peer-to-peer networks. They can support thousand of clients and they can link multiple computing platform, such as windows ‘95’98’NT’2000’XP and Macintosh. Like mainframe based centralized server and are administered from a central location.

            Whereas a peer-to-peer network consists have Computers linked to one and other, client/server networks consists of computer linked, again by means of cabling to a centralized server. The serer must be capable of running a Network Operating System (NOS), such as Windows’NT server, linux or Novel Netware. Such NOS are much more complex than a typical desktop operating system.

Client:

            Network clients are typically desktop computers with their own local storage and their own processing power. In order to communicate, both client Computers and server must be equipped with a network adapter card, or Network Interface Card (NIC card), which is usually installed in one of the expansion slots inside the machine. The network adapter card is responsible for both sending message  and for monitoring- ‘listening’ to the network for incoming message addressed to the client.

            To actually connect the client to the network cabling, the network adapter include a post that accept a cable ending in one of several types of connectors.

Server:

            Network serves are the behinds the scene workhorses that provide service requested by the client computer. The servers themselves can be categorized in different ways, depending on the type of work they do: Dedicated and Non Dedicated servers.

·                     Dedicated Server:

                        Dedicated Server are the quite powerful machines that powerful machines that power that network and provide resource but are never used for the tasks performed by the client desktop PC and workstations that request their services. This machine must be fast a powerful to handle simultaneous user requests and to run a network operating system that provides for network security, administration and management.

·                     Non-Dedicated server:

                          Non-dedicated server typical of peer to peer networks are: machines that are set up to they can both provide  (server) resources and do the work required of a client machine. These machines can be normal desktop PC in their day-to-day lives as long as they run an operating system, such as windows’98, NT workstation that gives them the ability to share files and resources. A non-dedicated server requires less processing power, memory and disk storage than a dedicated server so, typically it can a machine along the lines of a Pentium class desktop computer with say, a standard serving of 32 to 64 MB of RAM and hard disk of 3 GB or more.

            What is  LAN topologies?

Introduction:

            One factor that is often a key to select a LAN is whether it must connect with other systems. If so, a server based solution is probably the best choice. This is because server based LANs are prevalent in the business world where networks are more sophisticated Consequently, there is a wide range of compatible products available to link the LAN with other computers.

            The type and configuration of the NICs used on our network should be chosen based on several factors: These factors are speed, cost, and expansions use either the Ethernet or ARCHnet topologies. These are advantage and disadvantage to both. Ethernet provides a fast interface to the file server, however its performance can degrade as the network traffic increase. For a small 5 to 25 – node network, this should not present a problem. ARCHnet is slower than Ethernet but does not suffer from the same performance degradation as traffic increase.

            Another choice we must make is which topology to use. For server based LANs such as Netware, we must decide. As there is an increasing demand for interconnecting networks, it makes sense to adopt a standard topology. The two widely used ones are Ethernet and IBM Token Ring.

What is Bus Network?

Bus Networks:

            The simplest and easiest topology to implement a bus network (also known as a liner bus) consists of a single cable to which the client computers and servers connect.

            A bus network has open end. Each PC is connected to the network via a network card. Each peripheral, such as printers, can also be added to the network, each connected computer or peripherals is called terminal or node. Each end of the network is connected by a terminating resistor, which prevents signal interference. The most common example of this type of network is Ethernet network.

On a bus network, the nodes are passive participants, “listening” on the line and waiting for message address to them. This type of network can transmit to any other node whenever it wants, each message is broadcast, along with the recipient’s unique network address. Transmissions are limited to one computer at a time, so at any given time, one computer is master of the network and any other are waiting to transmit must wait until the line is free.

            Message on the bus network travel in either direction (“left” to “right” or “right” to “left). Because the network is based on a single cable, also called a trunk or backbone the ends of the cable must be equipped with a device called a terminator.

            Bus networks are easy to implement and requires less cabling than other topologies. In addition, nodes are relatively easy to add and remove. On the negative side, problem can be difficult such a network and a break in the trunk cable mean a breakdown in the entire network. It performance is too slow the network because the node must wait for longer periods being able to transmit over an open line.

Advantage of BUS Network:

i)                    Easy to extend terminals

                  We want to extend any terminal or want to add workstation to an existing bus network at any point along its length. More extensive additions can be achieved by adding extra segments cancelled by a type of signal amplifier called repeater.

ii)                  Simple wiring layout

                As we know that there is single common data path connecting all terminals. Bus type network decreases the installation cast because, the bus topology allows a very short cable length to be used , and lead to a simple, wiring layout and easy to maintain.

iii)                Flexible architecture

                The bus architecture has an inherent simplicity that makes it very reliable from every point of view. Because there is a single cable through which all data passes and to which all terminals are connected.

Disadvantage of the Bus network:

i)                    Fault diagnosis is difficult

                   Fault diagnosis is not a simple matter. In most LANs bases on a bus control of the network is not centralized in any particular terminal. This means detection of a fault may be performed from much point in the work.

ii)                  Fault isolation is difficult

                  If any terminal is faulty on a bus, it must be rectified at the point where the terminal is connected to the network. Once the fault has been located, the terminal can simply be removed. But in the star topology a defective terminal can easily be isolated from the network by removing its connection at the center.

iii)                Repeater configuration

                When a bus topology type network has its backbone extended using repeater reconfiguration may be necessary. This may be involved tailoring cable length, adjusting terminators, etc.

What is Ring Network?

           

A Ring networks is form of circle, at least as for as the nodes are connected. Network transmissions travel from node to node, in one direction only, in a closed, round robin loop. When a transmissions has traveled the full circuit, it has moved from the node that started the transmission to the computer connected to that node and so an until it has gone around the loop and returned to the starting node.

            A Ring network has tow characteristics that are supposed to solve the problems or bus network: It’s closed network, in which only one message (the token) can circulate at any given time, which makes it impossible to have collisions. To transmit, a node connected to the network must read the token when it arrives and retransmit it if it hasn’t reached its destination. The terminal that’s the destination of token must send an Acknowledgement. This doesn’t have to be send to specific address, because only the terminal that send the message is waiting for an acknowledgment. Other terminals simply retransmit it. This technology seems to solve the problems simply and efficiently there is, however, a downside to it: Nothing prevents one terminal from trying up the entire network, because all the other terminal (Node) are waiting for message sender to free token.

            Each node communicates directly with only two others; the node that transmits to the node it transmits to. When a node has some information to transmit, it waits until it receives the token.

            Ring network don’t require massive amounts of  cabling a fancy hardware to its implement and one of their great advantages is in giving each node an equal opportunity to transmit.

Advantage and Disadvantage of ring network?

Advantages of the Ring Network:

i)                    No wiring closet space required

As we know that there is only once cable connecting each terminal to its immediate neighbors, it is not necessary to allocate space in the building of wiring closets.

ii)                  Short cable length

The cable used, in a ring network is comporting to the bus, but it is smaller then the star network. This means that less connection will be needed, which will in turn increase network reliability.

Disadvantage of the Ring network:

i)                    Difficult to diagnose faults

Whenever any terminal gets failed, that will effect all others. It may be necessary to check (examine) a series of adjacent terminal to  determine the faulty terminal.

ii)                  failure of terminal causes network fail

As we know that the communication or transmission of data on a Ring network goes through every connected terminal on the ring before returning to the sender. If any terminal fail to pass data through itself. The entire network has failed and no data can flow until the defective terminal has been removed from the ring.

iii)                Network reconfiguration is difficult

If any one wants to modify the geographical scope of the network or want to add any other terminal than ring type network causes problem because it is not possible to shut down a small section of the ring while keeping the majority of its working normally.

What is Star Network or Star Topology?

            In a star  network, several devices or computer are connected to one centralized computer as shown  in figure. The advantage of star networks is that none of the other computer can communicate with each other if the central computer breaks down. If its is desired to transmit information from one computer to another. Only sending the details the central computer can do it, which in turn send them to the destination. A star network is used in banking sector for centralized record keeping in an on-line office environment.

           

A star network has characteristic that make it more efficient that make it more efficient that bus or token ring networks. Data exchanges are better organized and more efficient, because they are different cable, there’s risk of collision. However, this type of architecture is more expensive: it requires extra cables and a controller. To optimize the function of a network without incurring exorbitant costs, several Network Architecture can be used at the same time. Then the various networks can be linked by an inter-networks link.

            A star-network; extended out in different directions from a central location. This locations is occupied by physical equipment known as a Hub.

            Each computer is connected to the hub by its own cable segment. Only a single computer can transmit at a time and every computer on the network will examine the data to see if it is meant for them. Because of the star network is made up of single device attached to the end of single cables a break in the cable affects only the device attached to that cable. Failure of a single node will not affect the rest of the network. If, however the central hub fails the entire network will go down.

            Star topology can be implemented as a passive or an active design depending on the type of Hub. A passive hub is often utilized for small networks. All data received by a passive Hub is passed directly to all computers connected to the Hub. An active Hub, amplifies incoming signals before transmitting them to the other computers.

Advantage and Disadvantage of star network?

Advantages of Star Network:

i)                    Simple access protocols

As we know that a star network involves only the central terminal and one peripheral terminal. In this situation, contention for those who has control of the medium for transmission purposes is easily solved.

ii)                  Problem Diagnosis

As the central terminal is connected directly to every other terminal in star network so, the fault can easily detected and isolated. When this type of problems occurs then simply disconnected failing terminals from the network.

iii)                Ease of service

Easily service available for every directly to every because star topology has a number of concentration point i.e. at intermediate wiring closet. These provide easy access for service of reconfiguration of the network.

Disadvantage of star network:

i)                    Control Node (terminal) Dependency

As all the terminals depend on the central node(terminal), so that the problem arises is that if the central terminal (server) in a star network fails, the entire network is rendered in operation. This introduces heavy reliability and recurrence constraints on this terminal.

ii)                  long Cable length:

As in star network each terminal is directly connected to the center, also a star network is consist of a large quantity of cable so that overloading in cable channel and maintenance and installation problems can increase costs.

What is Tree network or Tree topology?

  In a Tree network several  devices or computer are linked in a hierarchical fashion as shown in figure. Tree network is also know as Hierarchical network. This type of  distribution system is commonly used in the organization where headquarters communicate with regional office and regional offices communicate with district offices & so on.

            It is easier to add new terminals or branches of it because the tree network divided into sub-units.

Advantages of Tree Network:

i)                    Fault Isolation

It is very easy to diagnose the defective terminals, simply disconnect the whole branches of the network from the main structure. This makes it easier to isolate a defective terminals.

ii)                  Easy to extend

It is easier to add new terminals of branches of it because the tree network divided into sub-units.

Disadvantages of the Tree Network:

i)                    Dependent on the Root

As the problems arises in star network, same reliability problems arises in the Tree network, because if the ‘head end’ device fail to operate, the entire network is rendered in operable.+

What is NIC (Network Interface Card)?

NIC (Network Interface Card):

            A Network Interface Card (NIC) is a network card or we can say add-on-card configured to fit our computer. The work (role) of network card is our computer  is to work on both side of the network connection. Network Interface Card (NICs) connects the PC to the network cable. NICs must be matched to the type of network and the type of network cable that you are using. It is important to choose a NICs manufacturers provide models that can connect to multiple network type, such as Coaxial, Twisted pair, and fiber optic.

           

The network card accommodation for a network connection to the network typically involves an external connector that lets the medium be hooked up; hooking up with cable of same kind is what makes the connection between the network card (NIC) and network possible.

            Now days the network card, which comes in 16 bit from going to be absolute and replace by new technology cards, these card comes in the form of 32 bit also called Gigabit Ethernet. There is lot of advantage the immediate choice for network interface card is fast Ethernet PCI adapter. Beside lower prices, fast Ethernet is compatible with older 10 MBPS network.

Ideally the card should support following features.

i)                    Support for plug play (PnP).

ii)                   Bus mastering technology since it helps economize on CPU utilization by allowing network request to by pass the processor and go straight to adapter.

iii)                 Support for remote boot ROM.

The Network Interface Card (NIC), or the adapter card, is a card that you use to connect your workstation to the files servers or the other workstations. You need to be aware of various components of a Network Interface Card.

·                    Interrupt Request (IRQ) Settings.

·                    Base I/O address

·                    Direct Memory Access (DMA) chips.

Your computer will depend of the type of topology you are using-specifically, Peer-to-Peer versus Client-Server. Also, the card will probably be cable-specific that is, it may need to use coaxial cable, 10/100 BaseT or Fiber-optic cable, depending on the card.

IRQ:

      Some memory chips are sited on your NIC. The purpose of these memory chips is to give packets that are addressed to your machine someplace to go when they arrive at your workstation. Unfortunately, the computer’s CPU, which is the brains of the operation, cannot see that memory sitting on the NIC. Therefore, somebody has to move that information from the memory of the NIC to the main memory of your system so that the CPU can process it. The component charged with the task of moving information from the memory of the NIC to your main memory is also a CPU, but his CPU is located on the network adapter.

      Each device that needs to use an IRQ must use a unique IRQ. Otherwise, you can expect your computer to crash! Using different IRQs for different cards in your system is not optional ;it is very important.

Base Memory Address:

      The location that an adapter card occupies in memory is refereed to its base memory address or base I/O address. This is the location that the CPU goes to when it needs to exchange information with the adapter card. The IRQ is used to signal to the CPU that there is information waiting. Then the CPU access these memory addresses to retrieve that information. It can also work in reverse when the system is sending information to the network.

DMA chips (Direct Memory Access):

      The next order of business is to find out how DMA chips move the information from the NIC to main memory.

            Your motherboard contains two DMA chips, and each chips supports four DMA channels, making a total of eight DMA channels on your motherboard. Every device that needs to use DMA must use a unique DMA channel.

What is data communication?

Data Communication:

           

Every person need to send message to, or use the same data, or receive messages from, or share program at many different locations. One answer to this problem is to keep separate data files at each location, but this approach is very costly and potentially a dangerous solution. It is very expensive to maintain these redundant files of data and difficult to ensure the continuing accuracy of data at any one location. The solutions of both, the need for more power and ability to receive, send messages and share data is found in data communication technology.

            The spending of data electronically from one location to another is data communication. In the computers located in same room, in office or in a building, the communication of data is done through a direct cable link; for e.g. a multi-user system is linked by a several systems through direct cable.

            Communications usage is growing day by day. Today’s, mini and large machines are in constant communication with outlying terminals. Computers can use telecommunications Hotel reservation system, Airlines etc.

Form of Data Transmission:

            There are two forms transmission of data:

i)                    Digital data transmission

ii)                   Analog data transmission

Digital Data Transmissions (DDT)

            Digital data transmission is the transmission of data using distinct OFF and ON electrical states. Computer represents the data in the form OFF and ON electrical states. These two states are represented by a 0 for OFF and 1 for ON.

Analog Data Transmission (ADT)

            Analog data transmission is the data transmission of data in a continues waveform for example telephone system is designed for analog data transmission.

Techniques of Data Transmission.

Techniques of Data Transmission:

           

The telephone lines transmit the human voice and data in a computer system, and this data remains in computer in the form of pulses. Hence for communication between computer and telephone line, it’s necessary that the digital pulse is converted into analog signal, before they are transmitted.

            The analog signal needs to be converted into digital pulse, so that the data can be received by the computer, after its journey is over in telephone lines. The process of converting digital pulses to an analog signal is called Modulation. The process of reconverting an analog signal to digital pulses is called Demodulation.

            The device that accomplishes modulation-demodulation process is called MoDem.

Transmission Modes:

            Data transmission any one of the following mode:

a)                  Simplex mode

b)                  Half-duplex mode

c)                  Full-duplex mode

Simplex Mode:

            In simplex mode data can be transmitted in one direction. The device using simplex mode of data transmission. A device using the simplex mode of transmission can either send or receive data, but it cannot do both.

Half-duplex Mode:

            In half duplex mode, data can be transmitted back and forth between two stations but data can only go in one of the direction at any point of time. An example i.e. wireless (generally used by military) where the user must either or listen, but can not do both at the same time.

Full-duplex Mode:

            The full duplex mode allows a devices to receive and send data simultaneously. A full duplex mode is faster, since it avoids the delay that occurs in half duplex circuit.

What is Integrated Services Digital Network (ISDN)?

Integrated Services Digital Network (ISDN)

            The ISDN is a networking Concept providing for the integrated of voice, video and data services using digital transmission media combining both circuit and packet switching techniques. ISDN was firs launched in Singapore in 1990. ISDN is a type of telephone service, which is an alternative to another computer at a speed, which is faster than even faster than even fastest Modem. If ISDN is available in our area, we should consider it as an alternative to using a Modem with a regular phone line.

          

  ISDN has following features:

·                    Processing of various types of voice, video, data etc.

·                    Transmission and processing of digital data

·                    E-mail box

·                    Tel-conference

·                    Tele-fax, video-fax etc.

ISDN is a type of telephone service, which is an alternative to a regular phone line. The great advantage of ISDN for us is that it allows use to connect to another computer at a consider it as an alternative to using mode regular phone line.

            ISDN services are delivered in one of 2 ways:

1.                  Basic Rate Interface (URL).

2.                  Primary Rate Interface (PRI).

BRI is for home and small business where as PRI is an expensive, large scale service suitable of big company needing to connect many computers and devices.

            One ISDN line provides a number of channels each of which offers a specific amount of bandwidth. Here, bandwidth refers to the capacity to transmit information. A BRI provides three channels:

·                    2 B channels and

·                    1 D channel

B channels carry the bulk of data via computer connections, voice conversations, and fax transmissions and so on. B stands for bearer channel. If offers bandwidth of 64 KBPS. We combine 2 B channels to give up to 128 KBPS.

            The D channel is used for control of ISDN itself. It is used for sending the set up and signaling information back and forth between the telephone system and our devices. The name “D Channel stands for Data Channel”. Actually it carries the internal ISDN data. Our data is actually carried on the B Channels. It has 16 KBPS, however it is used by ISDN itself and so it is not available for use with a computer or telephone.

            A ISDN adapter has to be connected at both end (one at transmitting end and one at receiving end) of the connection in order to use this ISDN connection.

           

            ISDN truly represents the next generation of the world’s telephone service for all forms of telecommunications, including voice.

What is Coaxial Cable?

Coaxial Cable:

            Coaxial cable, often referred to as BNC cable (the initials refers to the Baynonet-Naur Connector-a byonet-shaped for thin coaxial cables), is made of a single copper wire encased in insulation and then covered with a layer of aluminum or copper braid that protects the wire from outside interference. If you need more bandwidth and noise protection than twisted-pair can provide, but can’t afford fiber-optic, coaxial cable is the way to go.

            Coaxial cable has four parts:

·                    Inner conductor: A central wire

·                    Dielectric: A layer of insulation that surrounds the inner conductor.

·                    Shield: A layer of foil or metal braid that covers the dielectric.

·                    Jacket: A final layer of insulation.

If is a popular cable for the connective of the computer terminals. It consist of the two conductor surrounded by two insulting layers. The first layer of insulation encloses a central copper conductor wire. This layer has an outer shielding conductor braided over the top of it.

            Coaxial Cable prefer mostly bus topology network. Each device must be connected to a T-connector. Each T-connector is connected to the next with a coaxial cable. After all of the devices are connected, the ends of the cable must then be terminated with terminator, a coaxial network is configured in a bus topology.

Four varieties of coaxial cable are available. Each is used with different types of LAN:

·                    Ethernet: used frequently as a backbone for large coax networks. Often referred to as 10Base5,a standard set by the institute for Electrical & Electronics Engineer (IEEE), and also called Thicknet.

·                    RG-58A/U: Used in coax Ethernet networks. Often referred to as 10Base2 and also called Thicknet.

·                    RG-59/U:Used on CATV (Cable TV) and ARCnet (an older network topology).

·                    RG-62/U:Used on ARCnet and IBM terminals .

What is Fiber optic cable?

Fiber optics

    The major Network system new support fiber-optic cabling because fiber-optic cables transmit data as light pulses through glass cables and the significant advantage of this type of cabling over others, is that it provide the fastest transmission speed and more reliable. Fiber optic is thin on flexible.

     Fiber optic also called optical fiber is usually found where long cable length are required, where extremely high speed is desire. It is much less weak to these environmental difficulties because it uses light impulses along a glass or plastic wear or fiber, rather than electrical signals through on electrically conductive medium light signal protection from environmental interface. The light produce fro the end of a fiber optic device as the light could damage your eyes as permanently.

      Fiber optic is usually refereed to simply as fiber. Each segment of fiver optic cable must be connected at each end with a special fiber optic connector.

               In other words we can say fiber-optic networks can be used to obtain high transmission speeds. Fiber-optic cable transmits light rather than electrical signals. Light is reflected by the sides of the fiver. The transmission speed of the signals is equal to the speed of light in the material used for the cable, which is not huge speed improvement over transmitting electrical signals. However, the advantage is that fiver-optic signals are not sensitive to electromagnetic fields. We can therefore achieve maximum transmission speeds using a conductive fiber that is nothing more than a simple, uninsulated piece of plastic. Moreover, its easy to multi-fiber cables, because there is no interference between one fiber optic conductor and another. The data transfer speed on such networks can reach 150 MBPS, which is 15 times the speed of the today’s standard networks. At these speeds it’s possible to transmit sound and even animated image in real time.

Twisted Pair Cable:

Twisted pair cable is common type of network cable, because of low cost. Physically, in its simplest form twisted pair cable consists of a pair of insulated copper wires twisted around each other.

Twisted pair cable is considerably less expensive than the other types of cabling. Large network installations the lower price of cable offsets the cost of a hub and makes twisted pair low cost network solution.

On this category include various type of twisted pair, these are: Unshielded twisted pair (UTP), Shielded twisted pair (STP) 10BaseT,100BaseT. All of them UIP cable prefer Hub based network solution.

Unshielded Twisted-Pair:

                     

The unshielded twisted pair cables are highly sensitive electromagnetic interference. It is commonly used for telephone connections. Now a day they are also used for L AN purpose. The twisted pair compress of two wires twisted together six turns per inch to provide shielding from electrical interference plus consisting impedance; or in other word we can say it is a cabling system that we can use for Ethernet or Token ring networks and many other types of data communications. UTP, unlike coaxial or IBM type 1 cable, in not inherently food at carrying high-seed data. However, it does provide satisfactory results over short distances. Its attraction is that it is thin, cheap, and already in place in many buildings. Standard telephone wiring uses UTP.

UTP is more flat to interference that Type 1 cable, which is shielded. Its installation should be left to specialists if good results are to be achieved. However, its low cost allows buildings to be flood wiered, so network access point can be provided anywhere there is likely to be a desk. Or any place someone may carry or want to use a portable laptop machine! Given the frequency with which people move offices, the increasing availability of portable computers, and the cost  of changing networks that use traditional cabling methods, this is a big selling point. UTP will surly become more popular in the future.

Shield Twisted Pair

This wires are generally thicker than UTP and are shielded from any electrical interference by protective coat of insulated material.

Types of Connectors.
Types of Connectors
You can’t just go out get cables and expect to run your network. First, you need some way of catch your computer to the network via those cables. In other words, you now need to investigate connector possibilities.
The kind of connectors you need depends on the kind of cable that you use. If you buy Ethernet T-connectors for you future network, you’d better be prepared to go with an Ethernet network because Ethernet connectors won’t work with twisted-pair or fiber. Each kind of cable uses different connectors.

BNC Connectors:
You’ll use three kinds of connectors on an Ethernet bus network.

* T-Connectors:  

Link the cable to the cards making T-Shape. The T-connector plugs into the card         you’ve installed in your PC. The cable connects to the crossbar of the T.

* BNC connectors:      
link cables together and connect them to T-connectors.


* Terminators:
Terminate the LAN on either end. Terminators are made for either 50-ohm or 75-ohm cable; 50-ohm terminators are     usually the standard. Pay attention coax network cable system needs 50-ohm terminators.

* RJ-45:

Most unshielded twisted-pair cable terminates using connectors that look like chunkier versions of the connectors used to plug your telephone into the wall. These are called RJ-45 whereas your telephone uses RJ-11 connectors. One end plugs into your computer card, and the other plugs into a punch-down block in the wiring closet or a hub. The moment just understand that the way UTP terminates renders it unsuitable for any kind of wiring other than the star topology.

what is Network Connection Device?

Network Connection Device:

The devices Bridge, Repeater, Gateway and Router are inter networks commonly use these special devices. To extend connection within local area network.

Bridge:

A bridge interconnects two networks that use the same technology (such as ARCNET or Ethernet). When a bride interconnects two networks called “Westside” and “eastside”. In addition to interconnecting networks, Bridges often boost performance security and reliability. For example, we know that a collision detection system required a computer to delay transmission after a data collision occurs. As we add more computers to a network, the number of data collision rises.

Network administrators often use a bride to create two or more small networks even if performance is not a problem on this network. As we have learned in a ring or bus topology, a single break in a data bus stops all network communication. By partitioning  a single LAN into multiple LANs (connected by a bridge), a Network administrator reduces the impact of a break in the data bus.

A Repeater:

A repeater is a device, which copies or repeats signals that it receives. However a repeater also amplifies all received signal before re –transmission. This means a repeater increases the size of Analog wave forms it receives. By increasing the size of the waveform (without changing its frequency) or we can say that a repeater strengthens an increasing signal before sending the signal on its way. By strategically placing repeaters along a network bus, Engineers can extend the distance between adjacent computers.

A Gateway:

It is a generic term that can refer to three types of network entities; we can refer to a router as a gateway. A gateway is identical to a router or also refers to something called an application gateways translate data that specific network programs use . the most common type of gateway is one that e-mail application use.

A router:

It translate the data between networks and a router commonly transfers data between different technologies such as IBM Token Ring and Ethernet, by using some technology. Since internet consists of thousands of networks that use many different technologies, router is an essential part of the Internet. A router has an address on the network, whereas a bridge does not.

In other words we can say that a computer can send a packet destined for another network to a router. The router will transfer the packet to the other network. Whereas a bridge must examine all the data on the bus to determine which packets to transfer between networks. As such, computer never send packets directly to the bridge doing so are unnecessary. A router never examines a packet on the data bus unless the packets contain the router’s address.

What is Network Operating System (NOS)?

Network Operating System (NOS):

              Every computer needs an operating system; they may be UNIX, DOS, OS/2 or NOS. if you want to run our computer properly in a network than NOS must be loaded properly. Networks Operating System sometime fails internally due to the bugs in codes. There can also be problems due to the drivers that access the Network Interface Card (NIC) or adapters. Apart from the above, may failures occur due to applications designed to run on server when they access the NOS services with illegal function calls

                               The network operating system has two basic components: the network server operating system itself and the workstation. The network server operating system runs. Within the server machine and processes all the services the network operating system usually supplied by a manufacturer OEM, sometimes building on a general-purpose operating system . The workstation components run in the workstation and establish the connection with the network server and control the flow of communication.

OSI Model:

The international organization for standardization (ISO) develops the OSI (Open System Interconnection) model in 1997. the OSI model defines the rules that apply to the following issues:

How Network devices contact each other and how they understand the language of each other and how thy communicate with each other.

Methods by which a device in which a network know when to transmit data and when not to.

Methods to insure that network transmissions are received correctly and by the right recipient.

How the physical transmission media are arranged and connected.

How to ensure that network devices maintain a proper rate of data flow.

How bits are represented on the network media.

The OSI model is nothing tangible it is simply a conceptual framework. The OSI model doesn’t perform functions in the communiation process. The actual work is done by the appropriate software and hardware the OSI model protocols will handle those task. The OSI model consists of seven layers.

1. Application layer:

The application layer is eh topmost layer of the OSI model and it provides services that directly support user application such as database access,, e-mail and file transfer. It also allows application to communicate with application on other computers as though they were on the same computer. This application layer includes the basic service from any network including dealing with files. Sending messages to other network.

2. Presentation Layer:

The presentation layer translates the data access from the application layer in the language understandable by network or computer. The presentation layer does protocol conversion, data translation, compression and encryption, character  set of conversion and the interpretation of graphics commands. The network redirector operates at this level . the network redirector is what makes the files on a file visible to the client’s computer.

The network redirector also makes remote printers act as though they are attached to the local computer.

This layer is responsible for ensuring that data is in a form everyone can understand and work with takes the data from the session layer and passes it along to the application layer.

3. Session Layer:

This layer establishes a session in which the communication has done between two computers. This layer provides services such as name look up and security to allow two programs to find each other and established he communicate on link the session layer also provides for data synchronization and check pointing so that in the event of network failure, only the data sent after the point of failure need by resend this layer also controls the dialogue between two processes after mining who can transmit and who can receive at what point during the communication. Session layer protocol establishes and manages session using a data’s taken toe determine which can talk and when talk to communicate the computer one to others all data packet’s information knows as token.

4. Transport Layer:

The network layer ensures that packets are delivered error free, in sequence, and with no loses or duplication it provides error free transmission of data from one computer to another. The transport layer message from the session layer into packet to be sent to the destination computer and reassembles packets into message to be presented to the session layer the transport layer typically sends and acknowledgement to  the originator for message receive.. the transport layer is home to a number of protocols: TPO, TP1,TP2 and so on. These layer handle the packet of message and reassembly and error recovery.

5. Network Layer:

The network layer decides the best route for data transfer, which are adopted from transport layer and forwarded packets of devices that are further away then a single link. The network layer translates logical network addresses into physical machine addresses. This layer also determine the quality of service such as the priority of the message and the route message will take if there are several ways a message can get to it’s destination.

The network layer also break large packets into small chunks if the packet is larger than  the largest data frame the data link layer will accept the network resembles the hunks. Into packets at the receiving in the protocols at this layer may choose a specific route through an interact work to avoid the access traffic caused by sending date over networks.

Networks layer defines how the network moves information from one device to another. This layer corresponds to the hardware interface function BIOS of and individual PC, because it provides a common software interface.

6. Data Link Layer:

The data link layer provides for the flow of data over a single link from one device to another. It accepts packets from the network layer and packages the information into data unit called frames to be presented to the physical layer of transmission. The data link layer adds control information such as frame types routing to the data being sent. Actually this layer provides for the error free transfer of frames from one computer to another. a cycle redundancy check added to the data frame can detect damaged frames. The data link layer can also detect when frames are lost and request that those frames be sent again. This layer further divided into two sub-layer,

a. logical link control, which establish and maintains links between the communicating devices.

b. Media access control (MAC), which controls the way multiple devices share the same media channel.

If defines how information gains access to the wiring system. The data link layer defines the basic protocol used in the local network. If decide and send a message over the cable at any given item the form of messages and the transmission method of those message.

Physical Layer:

The physical layer is simply responsible gains access to the wiring system. The data link layer defines the basic protocol used in the local network. if decide and send a message over the cable at any given item, the form of messages and the transmission method of those message.

The following item are addressed at the physical layer.

Network connection type

Physical topologies

Analog and Digital signaling.

Base band and Broad band transmission.

Termination.

The first layer of the OSI Reference Model is the physical layer, which defines the basic hardware of network, which is the cable that conducts the flow of information between the devices linked by the network. this layer defines the type of wire such as coaxial, twisted  pair cable, length and connection and the interface of the cabling system.

What is Protocols?

Protocols:

Protocol establishes standards for such transmission of data. Both sending and receiving device must be capable of communicating using the same protocols. Some common protocols are the followings:

TCP/IP

IPX/XPX

Net BEUI

TCP/IP (Transmission Control Protocol/Internet Protocol):

Transmission Control Protocol (TCP) is responsible for delivering information correctly TCP establishes a connection between sender and receiver before transferring data.

IPX/SPX:

Internet Packet Exchange/Sequential Packet Exchange is the mostly commonly used with Novel Netware operating system for  networking purpose. It is fast, well-established protocol; but not used on the internet.

Net BEUI:

Net BIOS Extended User Interface (NetBEUI) is transport Protocol that is commonly found is smaller networks, NetBEUI is fastest protocol than others. It is roundtable on Internet. It can send and receive files and folder.

What is windows networking?

The term networking covers a broad range of the topics and technologies. A computer network is segmented into different parts to share the data and resourced between the different computers of a network. Microsoft has released the operating systems that have the networking capabilities so Microsoft windows 98, Microsoft Windows 2000, Windows 2003, windows XP Professional and Windows Vista all are the network operating systems. All these operating systems have built inn capabilities of files and printer sharing , security, network administrative control, protocols support such as TCP/IP, NetBIOS, IPX/SPX and network hardware support.

Naming computer

All computers in windows based network requires a unique name for their identification i.e. the name of ht computer A cannot be assigned to the computer B and so on. Assign a meaningful computer name to all the computer and the name should be easy longer than the 15 characters and thy contain no spaces in the. Also try to avoid the special names while naming the computers such as /\ *,:,. To assign a computer name in Windows XP and Windows 2000 do the following things.

Right click on the My computer.

Click Properties.

Click on Computer name.

Assign a unique and meaningful computer name.

Naming Workgroup and Domains 

A Windows based computer network can be a workgroup (Peer to Peer) or domain (client/server). You can make your computer a part of the workgroup or a domain. If you have centralized server then your computer will be part of the domain and if you have no server then all computers will be having peer to peer networking. In both cases while joining your computer to a domain or a workgroup always assign unique, sequenced, memorable and meaningful names to the computers. Do not use duplicate names and the special character such as /\*,:,,. In order to join a computer to a domain of workgroup in Windows 20000 and Windows XP Professional do the following.

Right Click on my computer.

Click Properties

click on Computer Name.

In workgroup or domain, enter the name of the workgroup or domain.

If everything is correct such as unique computer name, unique IP address, correct workgroup or domain name then you computer will be the part of the workgroup or domain in the few seconds and you will be see a welcome to domain or workgroup message and will be prompted to restart the computer name.

How to set the Network in computer?

You can get a complete home network up and running in easy steps. Here’s a summary of what’s involved:

Take a stock of your existing hardware.

Decide what type of network technology you wish to use.

Make a list of the hardware you need for each computer.

Install the network adapters and install you Modem or, Router with Hub(Switch).

Physically cable the computes together.

Switch on all computers. Printers and other peripherals,

Make sure the ICS host is connected to the Internet or, Internet connection to the hub (switch ) through Router.

Run the Network Setup Wizard on the ICS host.

Run the Network Setup Wizard on the other computers on the network.

1.  Take a stock of your existing hardware

Note each computer’s location and its hardware, including peripherals such as printers and modems.

2.   Choose a network technology

The most common choices are Ethernet and wireless LANs. For an Ethernet LAN you will need to install a network interface card, or NIC, in each computer and run cabling between the computers.

Depending on the size of your network, you may also need a network hub or router to provide interconnection between PCs on the LAN. Two PCs can get y using and RJ-45 crossover cable; three or more computers require a hub or multi-speed hub (called a switch).

If you have a high-speed Internet connection, a high-speed router is a good option. The network Setup Wizard includes links to detailed advice about configuring you network, including help on designing a network layout to suit your home.

If you opt for a wireless LAN, you’ll also need a NCI for each PC. The big benefit for home environments is that a wireless LAN does away with the need for cabling. On the down side, though, wireless LANs tend to be slower, less robust and appreciably more expensive than traditional Ethernet LANs. In particular, wireless LANs do not always live up to their sated working range, and you may find factors such as you home’s construction and may need to add a expensive Access Point to extend the range of the LAN and , even so, it the store will refund your money if the LAN will not provide reliable performance within the specified range.

3.   Make a list of the hardware needed

Make a list of the hardware you need for each computer, not forgetting any cabling, and buy it. If you’re a little dazzled by the choices and configurations, consider purchasing a networking kit. These kits contain all you need to set up a two- or three-PC network. if possible, look for hardware which features the Windows XP logo, indicating it is fully compatible with XP.

4.   Install the adapters

Install the network adaptors and install your modem on the ICS host computer (you can also let the computers connect to the Internet independently by installing modems on each)

5.     Cable the computers

Physically cable the computers (and hubs or routers) together. Of course, you won’t need to do this if you’ve chosen to go the wireless rout.

   If you’re installing and Ethernet network and have a lot of cabling work to do, you may prefer to get a professional to come in and do this work for you. It won’t be cheap, but you can be sure you get the job done correctly and hopefully with minimal damage done to walls ceilings and floors.

6.     Switch it on

Switch on all computers , printers and other peripherals.

7.      Connect to the internet

Go to the ICS host computer and make sure it is connected to the Internet. or, make a Internet connection to the Network Hub (Switch) through the router.

8.     Run the network setup Wizard on the ICS host or on all computers

XP’s Network Setup Wizard takes much of the pain out of setting up a home network.

What is wired network?

Wired networks, also know as Ethernet networks, connect your computer to your Internet connection with a cable that looks like a thick phone wire. Wired networks are highly reliable, very secure, extremely fast, and easy to se up. They’re also the least expressive type of network. you should use a wired network whenever it’s practical. Wired networks also offer better reliability for high-quality video than wireless networks do.

Wired networks do have a drawback, however: the wires. Wires can be messy, and you may need to hire an electrician if the computer you are using is in a different room than the one with the internet connection. Installing a network connection port requires an electrician. (A network connection port looks like a large version of the port you use to plug in your telephone).

Network cables, also know as Ethernet or “Cat 5” cables, can be up to 300 feet long. However, you probably don’t want cables running across your floors. If you have a computer in a different room from your Internet connection and want to connect if to the Internet, you can extend your wired network across your home’s power lines using a wall-plugged network extended kit. When choosing a network extended kit, opt for the fastest speed available.

  With network extender kits, network speeds (known as bandwidth ) vary according to your home’s wiring. Typically, extenders provide about one-third the speed of a standard wired network. that’s fast enough to browse the eb, listen to music across your network, play Internet games, and even wach video (as long as it’s not high-definition video).

What is wireless network?

Wireless networks

Wired  networks are the best choice for connecting desktop computers and stationary devices (such as Xbox 360 and digital video recorders). But the Internet is even more fun to use when you’re not tied to one spot. Laptops, Tablet PCs, and many pocket PCs can connect to wireless networks, such as 802.11b and 802.11g, giving you the freedom to use the Internet in your living room, kitchen, backyard, or anywhere around your home.

While wired networks are reliable and relatively easy to set up, wireless networks can be more complex, for the easiest installation, use Windows XP with Service Pack 2 and a wireless access point that supports Windows Connect Now technology.

Note: Hardware vendors or manufactures) claim wired and wireless networks have particular bandwidth capacities. Deciphering this information can be confusing. In genera., higher is always better. When you’re comparing wireless bandwidth to wired bandwidth, divide what the vendor claims the bandwidth will be by 4. for example,802.11b wireless networks claims to have 11 megabits per second(Mbps) of bandwidth. Yet they typically achieve less than 3 Mbps, which might not be enough to take full advantage of your broadband Internet connection. If a wireless access point claims it is 54 Mbps, you can expect to get about 18 Mbps of throughput. Wall-plugged network extenders similarly exaggerate bandwidth. Wired networks that don’t use extenders get about two-thirds of their claimed bandwidth. The most common network, 100-Base-T, gets about 60 to 70 Mbps bandwidth.

You can choose from several different wireless technologies. If the following list seems overwhelming, don’t worry-just buy 802.11g networking equipment. The full list of wireless technologies includes:

How to set a wired network?
Wired networks are the best way to connect your desktop computer to the internet and to other computers in your home. While wireless networks offer flexibility for portable computes, wired networks offer unbeatable performance, reliability, and security.

If you have a single computer, connecting to the internet is as simple as plugging a network cable into your computer and your modem. If you have more than one computer, you need to connect a router between your modem and your computers. If one (or more) of  your computers is in a different room from your router, you can use a network extended to connect the computer.