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

 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

 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

 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

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

 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

 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 needs  Communications servers are set up to allow users remote access to the network

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

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

 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

 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

 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

 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

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 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