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LANsNetworking means connecting two or more computers together to share files and resources. The usual purpose of computer networks is for business use, where multiple employees can work on centrally stored files, from their individual workstaions. These networks usually have a mainframe "File Server," or other powerful machines which contain all of the login credentials and permissions needed to allow the employees logon to the Domain to access customer records and data files stored on the servers, from their less powerful, or "dumb" workstations. The main computers are referred to as "Domain Controllers, File Servers, or Terminal Servers," and the remote computers, or networked keyboards, are called "Workstations," or "Terminals." The Servers allow employees at their workstations to read, and or write to the data files that are stored on the Server's hard drives. This relationship is a Master-Slave system.
The computers making up the network contain Network Interface Cards (NICs), which are connected by cabling, typically CAT5, to devices called "network hubs," which regulate the flow of data between the Servers, the Workstations, and the network printers. Often, the printers are connected to a special device called a "Print Server," which can feed one or more Laser printers with print jobs originating from various Workstations.
All of the computers that interconnect physically in one building are referred to a Local Area Network, or "LAN." Often, employees on the road, or at other corporate buildings, or in other cities, must connect to the Domain by remote wired, wireless, or dial-in connections. This expanded network is called a Wide Area Network, or "WAN." The Internet is actually a WAN.
I mentioned that the system which has Domain Controllers with File Servers and Workstations is a Master-Slave system. There is also a network system caller "Peer-to-Peer."
Advantage and Disadvantage of Networking
There are so many benefits with networking it is little wonder that it has become the most highly used tool in Executive and Management job hunting.
Advantages are as follows:
- You can be afforded an opportunity not yet advertised therefore reducing the competition significantly.
- A job may be specifically created for you based on an employer’s requirement.
- You are in the enviable position of focussing attention on the qualities and strengths you possess.
- Networking provides social contact and stimulation.
- Rather than having to make a cold call or attend an interview with people who are unknown to you, you will have a referral that will make the process easier.
- Openings are created for you to be opportunistic and flexible. You must actively listen to the communication that is going on around you.
- Networking is a two way process that can enable you to help others.
- Networking is a proactive job search method.
- Networking puts you in control, setting your own pace and course. It is less stressful than sifting through tons of advertisements and is far more productive over time.
Disadvantages are as follows:
- While networking is a very effective technique one must always be aware of the possibility of indiscretion. Choose your contacts wisely and ensure that you maintain confidentiality at all times.
- Networking can be a waiting game where you have to wait it out patiently for the right opportunity or the right contact to come available.
Local Area Networks (LAN)
Definition: A local area network (LAN) supplies networking capability to a group of computers in close proximity to each other such as in an office building, a school, or a home. A LAN is useful for sharing resources like files, printers, games or other applications. A LAN in turn often connects to other LANs, and to the Internet or other Wan
Most local area networks are built with relatively inexpensive hardware such as Ethernet cables, network adapters, and hubs. Wireless LAN and other more advanced LAN hardware options also exist.
Specialized operating system software may be used to configure a local area network. For example, most flavors of Microsoft Windows provide a software package called internetA computer network that covers a relatively small area. Most LANs cover a single building or group of buildings. A system of LANs can be connected over any distance through telephone lines and radio waves, creating a wide-area network.
Peer-to-Peer Networks
In a Peer-to-Peer network all of the computers that are interconnected are able to function as either Master or Slave, in their local area network. These are typically found in small offices or businesses where everybody is able to work with data files stored on their own machines. While Peer-to-Peer systems may have certain files stored on one master machine, it is not necessarily so, and any workstation computer can become a file server for the others on the network, if it is so decided.
It used to be that networking multiple computers was strictly in the domain of advanced business systems, requiring the services of a systems administrator knowledgable in the mysteries of Windows NT operating systems and Domains.
While this job position is still very much in demand for businesses, networking has now spilled over into the home computer market. The Internet phenomenon has led to many families having more than one computer in the household, especially those users with high-speed broadband connections.
Many of my service calls now involve setting up home computer "peer-to-peer" networks
In the star LAN topology, each station is directly connected to a common central node. Typically, each station attaches to a central node, referred to as the star coupler, via two point-to-point links, one for transmission and one for reception. In general, there are two alternatives for the operation of the central node. One approach is for the central node to operate in a broadcast fashion. A transmission of a frame from one station to the node is retransmitted on all of the outgoing links. In this case, although the arrangement is physically a star, it is logically a bus; a transmission from any station is received by all other stations, and only one station at a time may successfully transmit. Another approach is for the central node to act as a frame switching device. An incoming frame is buffered in the node and then retransmitted on an outgoing link to the destination station.
In the ring topology, the network consists of a set of repeaters joined by point-topoint links in a closed loop. The repeater is a comparatively simple device, capable of receiving data on one link and transmitting them, bit by bit, on the other link as fast as they are received, with no buffering at the repeater. The links are unidirectional; that is, data are transmitted in one direction only and all are oriented in the same way. Thus, data circulate around the ring in one direction (clockwise or counterclockwise).
Each station attaches to the network at a repeater and can transmit data onto the network through that repeater. As with the bus and tree, data are transmitted in frames. As a frame circulates past all the other stations, the destination station recognizes its address and copies the frame into a local buffer as it goes by. The frame continues to circulate until it returns to the source station, where it is removed. Because multiple stations share the ring, medium access control is needed to determine at what time each station may insert frames.
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WAN - Wide Area Network
As the term implies, a WAN spans a large physical distance. The Internet is the largest WAN, spanning the Earth.A WAN is a geographically-dispersed collection of LANs. A network device called a router connects LANs to a WAN. In IP networking, the router maintains both a LAN address and a WAN address.
A WAN differs from a LAN in several important ways. Most WANs (like the Internet) are not owned by any one organization but rather exist under collective or distributed ownership and management. WANs tend to use technology like ATM, Frame realy and X.25 for connectivity over the longer distances.
WAN's PROTOCOLS
Related Protocols
LAN, MAN , TCP/IP
Circuit Switching
Circuit switching is a WAN switching method in which a dedicated physical circuit is established, maintained, and terminated through a carrier network for each communication session. Circuit switching accommodates two types of transmissions: datagram transmissions and data-stream transmissions. Used extensively in telephone company networks, circuit switching operates much like a normal telephone call. Integrated Services Digital Network (ISDN) is an example of a circuit-switched WAN technology.
Packet Switching
Packet switching is a WAN switching method in which network devices share a single point-to-point link to transport packets from a source to a destination across a carrier network. Statistical multiplexing is used to enable devices to share these circuits. Asynchronous Transfer Mode (ATM), Frame Relay, Switched Multimegabit Data Service (SMDS), and X.25 are examples of packet-switched WAN technologies.
SUMMARY:
Computer networks link two or more computers so that they can exchange data and share resources, such as printers, scanners, and an Internet connection. Networks are of two primary types: local area networks (LANs), which serve a building or a small geographic area, and wide area networks (WANs), which can span buildings, cities, states, and nations. Networks consist of special hardware, software, and people. For example, most networks have nodes (which can be workstations, communications devices, or file servers), NICs, network operating systems, and network administrators.
Computer networks can reduce hardware costs, enable application sharing, create a means of pooling an organization’s mission-critical data, and foster teamwork and collaboration. Disadvantages of computer networks include loss of autonomy, threats to security and/or privacy, and potential productivity losses due to network outages.
A peer-to-peer LAN doesn’t use a file server. It is most appropriate for small networks of one or two dozen computers. Client/server networks include one or more file servers as well as clients such as desktops, laptops, and even PDAs. The client/server model works with any size or physical layout of LAN and doesn’t slow down with heavy use.
The physical layout of a LAN is called its network topology. A topology isn’t just the arrangement of computers in a particular space; a topology provides a solution to the problem of contention, which occurs when two workstations try to access the LAN at the same time. The three different LAN topologies are bus (single connections to a central line), star (all connections to a central hub), and ring (tokens carry messages around a ring).
Protocols define how network devices can communicate with each other. A network requires many protocols to function smoothly. When a computer sends a message over the network, the application hands the message down the protocol stack, where a series of protocols prepares the message for transmission through the network. At the other end, the message goes up a similar stack.
The most widely used LAN protocol is Ethernet, which is available in two versions that use hubs and twisted pair wiring: 10BaseT (10 Mbps) or 100BaseT or Fast Ethernet (100 Mbps). The newest version, Gigabit Ethernet, can transfer data at the rate of 1,000 Mbps or 1 Gbps.
The special components that distinguish a WAN from a LAN are a point of presence and backbones. A point of presence (POP) is a WAN network connection point that enables users to access the WAN by a local analog telephone call (using a modem) or a direct digital hookup that enables a continuous, direct connection. Backbones are the high-capacity transmission lines that carry WAN traffic.
Circuit switching creates a permanent end-to-end circuit that is optimal for voice and real-time data. Circuit switching is not as efficient or reliable as packet switching; it is also more expensive. Packet switching does not require a permanent switched circuit. A packet-switched network can funnel more data through a medium with a given data transfer capacity. However, packet switching introduces slight delays that make the technology less than optimal for voice or real-time data.
