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COMPUTER NETWORKS

COMPUTER NETWORKS. Without reference, identify principles relating to Computer Networks with at least 70 percent accuracy. . COMPUTER NETWORKS. Network A group of computers connected by cable, or other means, so they can share information Common network terms

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COMPUTER NETWORKS

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  1. COMPUTER NETWORKS Without reference, identify principles relating to Computer Networks with at least 70 percent accuracy.

  2. COMPUTER NETWORKS • Network • A group of computers connected by cable, or other means, so they can share information • Common network terms • Server - Usually the most powerful computer on the network that provides the services for the network • Client - A computer on the network that uses the services provided by the server • Peer - A computer that acts as both a client and a server • Media - The physical connection between devices on a network • Resources - Anything connected to the network that is available to a client • User - A person that uses a client to access the network • Protocol - any predetermined set of rules that define how two devices or pieces of software should communicate with each other

  3. COMPUTER NETWORKS • Networking Models • Describe how information is processed by the computers on the network • There are three basic models we need to discuss: • Centralized Networks • The first computers were large mainframes that were very large and very expensive • Large, intensive tasks were input into these systems and the results were later printed out • These early centralized networks gave users the ability to access the network from remote locations • Today's centralized networks keep shared information in one location, assuring everyone is working on the same information • Costs less overall to operate and maintain • Because the mainframe/server handles all of the processing, this type of network is generally slow • Additionally, if users have a variety of application needs, the users must have these applications set up separately • Connectivity can become a large problem since users must connect to a central site

  4. COMPUTER NETWORKS • Distributed Networks • The popularity of PC's enable the processing power of individual systems to be distributed to all computers on the network • Data processing and storage is done on the local workstati • Server do not need to be as powerful or as expensive • This type of network accommodates a variety of needs, yet allows the sharing of data, resources and services • A drawback to this type of network is the susceptibility of viruses • Developing an effective back up plan can be more difficult if users store shared files on their own systems • The disadvantages of a centralized network become the advantages of a distributed network, and vice-versa

  5. COMPUTER NETWORKS • Collaborative Networks • Collaborative computing allows computers to share processing power across a network • Applications can be written to take advantage of this power to accomplish tasks much faster than a single system • In addition to this capability, this type of network is similar to a distributed network in its ability to share data and resources • This type of network also shares the advantages and disadvantages of a distributed network • Networking Types • Peer-to-Peer • The simplest form of networking • Each workstation acts as a client and a server • There is no central repository for data and no dedicated server to maintain • Data and resources are distributed throughout the network with each user responsible for sharing these items connected to their systems • Small, inexpensive networks can easily be set up using peer-to-peer

  6. COMPUTER NETWORKS • This type of network is ideal for small offices or home offices that require sharing of resources • All that is needed for a peer-to-peer network are the network adapter cards, cable (transmission media) and a networking operating system • A large disadvantage of this type of network is the number of users connected • Once the number reaches 10, degradation of performance becomes apparent depending upon how much the network resources are used • Additionally, shared files can have several different revisions based upon who is accessing them • Different resources are usually attached to different systems • Each user is responsible for maintaining administrative control of their systems, though they may be improperly trained • Security of the network is difficult to maintain • Very dependent on user training

  7. COMPUTER NETWORKS • Client/Server or Server-Based • A dedicated computer acts as a central repository for files and/or applications • The server controls the data, printers and other resources that clients need to access • Usually a very fast system with large amounts of memory and hard drive space • Having a powerful server allows the clients to be less powerful since they only request resources • The server will not normally act as a workstation as it's only purpose is to provide resources and services to clients • Multiple servers can be utilized within the same network, each having unique task handling capabilities • File and print servers are optimized to hand out files to clients and handle printing requests • Application servers actually handle all the processing requirements of an application being run on a client • Mail servers are specifically set up to handle client e-mail needs • Communications servers are set up to allow users remote access to the network

  8. COMPUTER NETWORKS • If your network has over 10 users, a server-based network should be considered • With a dedicated server, a synchronized file set can be maintained that everyone works from • Security of the network is easier to manage since only the server needs to maintain the accounts, rather than each workstation • Specific users can be granted access to resources using their server account • A peer-to-peer network uses a single password that is used by everyone to access a resource • A server based network is also more cost efficient than a peer-to-peer network • The server stores most of the files and applications that are shared on the network, so workstations do not need large hard drives or large amounts of memory • This helps offset the cost of the server since workstations do not need to be as powerful • One of the biggest disadvantages of having a server based network is the requirement of having a network administrator • Networking Services • File Services • Print Services • Message Services • Directory Services • Database Services

  9. COMPUTER NETWORKS • LANs, MANs and WANs • Local Area Network (LAN) • The smallest network size is referred to as a LAN • Normally contained within one building or in a small group of buildings • A LAN is typically a high speed, inexpensive network with very few or no errors generated on the network • Metropolitan Area Network (MAN) • This is a group of LANs located within a city or metropolitan area • Since the LANs are geographically separated, specialized equipment is required for connecting them to create a MAN • Typically, MANs are slower than LANs and carry a higher price • A MAN will have few errors, but more than a LAN • Wide Area Network (WAN) • This is the largest network size • WANs can interconnect both LANs and MANs across a city, state, country or even the world • The term Enterprise WAN refers to a network that contains all the LANs and MANs within an organization • WANs use connections world-wide and are prone to errors • WANs are much slower than LANs or MANs • Highly specialized equipment that is very expensive

  10. COMPUTER NETWORKS • Topologies • Description of how computers are connected without regard to how they communicate • Bus • Simplest to install • All devices on the network are connected to one primary trunk cable • Each end of the trunk cable needs to be properly terminated • Bus topologies normally use coaxial cable • Advantages • Easy to install and configure • Inexpensive • Easily extended • Disadvantages • Performance degradation • Weakened signal • Difficult troubleshooting

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  12. COMPUTER NETWORKS • Ring • Looks like a bus topology with connected ends • Provide high performance for a large number of users • Data flowing on the ring travels from computer to computer in one direction • The signal is retransmitted by each system when passed on to its neighbor • Token passing is frequently used on the ring topology • Advantages • provides an orderly network in which every device has access to the token and can transmit • performs well under a heavy load • Disadvantages • Malfunctioning workstations and cables create problems for the entire network • Changes made when adding or removing a device affect the entire network

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  14. COMPUTER NETWORKS • Star • Uses a separate cable for each workstation • The cable connects the workstation to a central device, typically a hub • Provides a more reliable network that is easily expanded • There is no central point of failure in the cable • To add more workstations, just add another hub • Hubs • Can be used as more than a central connection point. • Passive hub • Used to connect computers in a broadcast network • The signal sent to a passive hub is sent to all workstations with no regeneration or amplification • Active hub • Uses an external power source • It regenerates the signal before sending it out to all workstations in a broadcast network • Greater cable distances are allowed

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  16. COMPUTER NETWORKS • Switched hub • Directs the signal directly to the recipient • Can greatly reduce network traffic • Advantages (STAR) • Easily expanded • Easier to troubleshoot • Multiple cable types supported by hubs • Disadvantages (STAR) • Hub failure • Requires more cable • May require a device to rebroadcast signals across the network • Mesh • Provides the highest level of fault tolerance • A true mesh network uses separate cables to connect each device to every other device on the network, providing a straight communications path • Requires a large amount of cable and can quickly become confusing • Advantages • Enhanced fault tolerance provided by redundant links • Easy to troubleshoot

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  18. COMPUTER NETWORKS • Disadvantages • Difficult to install • Costly to provide redundant links • Ethernet Standard • The Ethernet standard was originally developed by Xerox in the 1970's • In the 1980's, Xerox let the Institute of Electrical and Electronics Engineers (IEEE) take over control of the standard • IEEE 802.3 is actually called the CSMA/CD committee although the term Ethernet is what is commonly used in the industry today • Although technically there is a difference between the two, the terms are used interchangeably

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