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CLARK UNIVERSITY College of Professional and Continuing Education (COPACE). Management Information Systems. Lection 04 Networks. Plan. Basic terms Classification of networks Topology of networks Model OSI Types of environmental data. Basic terms.
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CLARK UNIVERSITY College of Professional and Continuing Education (COPACE) Management Information Systems Lection 04 Networks
Plan • Basic terms • Classification of networks • Topology of networks • Model OSI • Types of environmental data
Basic terms Computer network isa collection of computers and other hardware interconnected by communication channels that allow sharing of resources and information.
Basic terms Server Client Client-server
Computer entirely dedicated to servicing the requests of other computers, plays the role of a dedicated server Basic terms
The computer that combines the functions of a client and a server, is a peer node. Basic terms 7
Classification of networks Speed of data transfer Territorial prevalence Organization of interaction of computers Environment data transmission
Low speed (less then10 Мbit/sec) Middle speed (less then100 Мbit/sec) Classification of networks Speed of data transfer: High speed (more then 100 Мbit/sec)
Local networks (LAN) Speed: 10 Мbit/sec- 10 Gbit/sec Urban network (MAN) Speed: dozens Mbit/sec Global networks (WAN) Speed: dozens Kbit/sec– dozens Mbit/sec Classification of networks Territorial prevalence
Wires network Wireless network Classification of networks Environment data transmission:
Peer-to-peer network Hybrid network Network with dedicated server Classification of networks Organization of interaction of computers:
Peer-to-peer network Peer-to-peer operating systems include server and client components of network services. Examples: LANtastic WindowsforWorkgroups Windows NT Workstation Windows 95/98
Advantages: 1. Low price 2. Simplicity of installation and operation Peer-to-peer network Disadvantages: Complexity of the information protection Efficiency depends on the number of computers
Number of computers in the network 10-20 Security problems are not critical You don’t wait significant expansions of your company When do we use peer-to-peer networks?
Network with a dedicated server Advantages: Division of resources Protection Data backup Big number of users Disadvantages: • Necessity of additional OS for the server • High complexity of installation and modernization of the network • Necessity of a separate PC as a server
Network topology Network topology describes the physical location of the computers, cables and other network components
Fully connected topology It is the topology of a network in which each workstation is connected to all the others. The physical fully connected topology is generally too costly and complex for practical networks, although the topology is used when there are only a small number of nodes to be interconnected
Topology "bus" is a topology with a common cable (called the bus), which is connected to all workstations. At the ends of the cable there are terminators to prevent signal reflection. Bus topology
Bus topology When building large networks there is a problem if a limited length of cables between nodes, in this case, the network is divided into segments. Segments are connected by various devices - repeaters, concentrators or hubs. For example, the technology allows the use of Ethernet cable up to 185 meters. 25
Advantages: a little time of setting up a network the cheapness (requires less cable and network devices) easy set-up the failure of some workstation does not affect the work of the whole network Bus topology Disadvantages: • any failures in the network, as the cable break, leads to the failure of the whole network • complex localization of faults • The network performance falls with the addition of new workstations
"Star“ is the basic topology of a network in which all computers are connected to the central node (usually a switch or a hub),forming a physical network segment. This segment can function both individually and like a part of a complex topology as “tree”. Star topology
Better performance Isolation of devices We can increase the size of the network very easily. Easy to detect faults and to remove parts. Advantages of star networks
Disadvantages of star networks • failure of the central switch will result to an inability of the network (or network segment) • it often requires more cable than for most other topologies • number of workstations in the network (or network segment) is limited by the number of ports in the central switch
Ring is the basic topology of a network in which workstations are connected sequentially to each other, forming a closed network. Ring topology
ease of installation practically complete absence of the additional equipment the possibility of stable work without a significant drop in speed of data transmission with heavy network traffic Advantages of ring topology
Disadvantages of ring topology • the failure of a single workstation, and other problems (the cable break) leads to the failure of the whole network • the complexity of the configuration and customization • the complexity of troubleshooting
OSI model In 1984 the number of international standardization organizations (ISO, ITU-T and others) developed the Open System Interconnection model(OSI). The OSI model defines the different levels of interoperability, gives them the standard names and indicates which functions levels must perform.
Physical layer It means the transferring of bits by physical channels, such as a coaxial cable, “twisted pair”, optic cable, wireless networks.
Data link level This level is a very powerful and complete set of functions for sending messages between network nodes. It gives us the opportunity of detection and correction of errors. Bits are grouped into sets called frames
Network layer Agreement of different technologiessimplification of addressing in large networks. Creation of reliable and flexible barriers on the way of unwanted traffic between networks. Messages on this level are called packages
Transport layer guaranteed delivery of data (it gives an acknowledgement of reception of packages) detection of errors at the level of the sender and recipient (it allows the host system to detect bad packages)
Session layer It manages the dialogue, i.e. it fixes which side is currently active and provides the synchronization
Presentation layer It works only with the form of data, without changing the its content. The information is always clear to the application layer of another system. Can overcome the syntactic differences in the data models, or differences in the codes of characters, such as ASCII codes Encrypt data
Application layer It gives a set of protocols which allow users an access to shared resources, such as files, printers or web-pages, and organizes their work together
Types of networks: Wires networks Wireless networks
