Network Topology network structure and network topology, Star, bus , LAN and WAN

network structure and network topology, Star, bus , lan and wan

1. NETWORK STRUCTURE (NETWORK TOPOLOGY)

2. Network structure is a term used to describe the method of how data on a network is organized viewed.

3. Network topology Types Bus topology Star topology Mesh topology Ring topology

4. NETWORK TOPOLOGY BUS TOPOLOGY

5. BUS TOPOLOGY A bus topology uses one cable to connect multiple computers . The cable is also called a trunk , a backbone, and a segment. Most of the time, as seen in Figure below, T-connectors are used to connect to the cabled segment. They are called T-connectors because they are shaped like the letter T. You will commonly see coaxial cable used in bus topologies

6. Advantages One advantage of a bus topology is cost . The bus topology uses less cable than the star topology or the mesh topology. Another advantage is the ease of installation . With the bus topology, you simply connect the workstation to the cable segment, or backbone. You need only the amount of cable to connect the workstations you have.

7. Disadvantages The main disadvantage of the bus topology is the difficulty of troubleshooting. When the network goes down, usually it is from a break in the cable segment. With a large network this can be tough to isolate.

8. Star Topologies

9. Star Topologies In a star topology, all computers are connected through one central hub or switch , as illustrated in Figure. This is a very common network scenario. Computer in a star topology are all connected to a central hub A star topology actually comes from the days of the mainframe system. The mainframe system had a centralized point where the terminals connected.

10. Advantages One advantage of a start topology is the centralization of cabling . With a hub, if one link fails, the remaining workstations are not affected like they are with other topologies, which we will look at in this chapter. Centralizing network components can make an administrator’s life much easier in the long run.

11. Disadvantages On the flip side to this is the fact that if the hub fails, the entire network, or a good portion of the network, comes down. This is, of course, an easier fix than trying to find a break in a cable in a bus topology. Another disadvantage of a star topology is cost to connect each workstation to a centralized hub, you have to use much more cable than you do in a bus topology

12. Mesh Topologies

13. Mesh Topology A mesh topology is not very common in computer networking, but you will have to know it for the exam. The mesh topology is more commonly seen with something like the national phone network. With the mesh topology, every workstation has a connection to every other component of the network , as illustrated in Figure.

14. Advantages The biggest advantage of a mesh topology is fault tolerance . If there is a break in a cable segment, traffic can be rerouted. This fault tolerance means that the network going down due to a cable fault is almost impossible.

15. Disadvantages A mesh topology is very hard to administer and manage because of the numerous connections. Another disadvantage is cost . With a large network, the amount of cable needed to connect and the interfaces on the workstations would be very expensive .

16. Ring Topologies

17. In a ring topology, all computers are connected with a cable that loops around. As shown in Figure, the ring topology is a circle that has no start and no end. Terminators are not necessary in a ring topology. Signals travel in one direction on a ring while they are passed from one computer to the next. Each computer checks the packet for its destination and passes it on as a repeater would. If one of the computers fails, the entire ring network goes down .

18. Advantages The nice thing about a ring topology is that each computer has equal access to communicate on the network. With bus and star topologies, only one workstation can communicate on the network at a time.

19. Disadvantages The biggest problem with a ring topology is that if one computer fails or the cable link is broken the entire network could go down . With newer technology this isn’t always the case. The concept of a ring topology is that the ring isn’t broken and the signal hops from workstation to workstation , connection to connection.

20. YEAR TECHNOLOGY LANGUAGES INPUT DEVICE OUTPUT DEVICE MEMORY STORAGE COMPUT-ATIONAL SPEED PERFORMA-NCE SIZE EXAMPLES First generation 1940-56 Vacuum tubes Binary coded languages Punched cards and paper tape Printouts Vacuum tubes for circuitry, magnetic drums for memory Fast at their times. Generate large amount of heat. Large amount of electricity needed. Very huge , required lot of space ENIAC,EDVAC and UNIVAC Second generation 1956-1963 Transistors Cobol and fortran Punched cards Printouts Primary memory: magnetic cores Secondary memory: magnetic disks In microseconds cheaper and energy efficient. Size became reduced. PDP-8, IBM 1401 and IBM 7090 Third generation 1964 – early 1970’s Integrated circuits (single chip) Supports many high level languages. Keyboards Monitors Primary memory: magnetic cores Secondary memory: magnetic disks In nanoseconds. reliable, cheaper, runs many applications and efficient. Production becomes easier. Became smaller NCR 395 and B6500 Fourth generation Early 70’s – till date Microprocessors (circuits maintaining millions of transistors) Interconnection of systems and resource sharing Mouse and keyboards, introduction of GUI. Monitors Semiconductor memories faster Powerful, compact , economical. LSI,VLSI,ULSI Apple- II, CRAY-1 Fifth generation Present and beyond Artificial intelligence ( human like computer) Mega chips: SLSI, millions of electronic components in a single chip. Parallel processing: Parallel access several instructions at a time. AI: it includes ES,NLP, vision recognition, robotics. It simulate and reproduce the human like behaving.

21. LAN A  Local Area Network  (LAN) is a  computer network  that interconnects computers in a limited area such as a home, school, computer laboratory, or office building using network media.  The defining characteristics of LANs, in contrast to  wide area networks  (WANs), include their smaller geographic area, and non-inclusion of  leased telecommunication lines .

22. WAN A  Wide Area Network  (WAN) is a network that covers a broad area (i.e., any telecommunications network  that links across metropolitan, regional, or national boundaries) using private or  public  network transports. Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations. In essence, this mode of telecommunication allows a business to effectively carry out its daily function regardless of location.

23. MAN A Metropolitan Area Network (MAN), connects across the cities, which are accessed only by certain group of users. It is more secured.

24. INTRANET (LAN) An intranet is a private network that uses Internet protocols to securely share any part of an organization's information or operational systems within that organization. The term is used in contrast to internet - a network between organizations - and instead refers to a network within an organization .

25. Benefits of intranets Workforce productivity- help users to locate and view information faster and use applications relevant to their roles and responsibilities. perform their jobs faster, more accurately, and with confidence that they have the right information Time Communication- Intranets can serve as powerful tools for communication within an organization , vertically and horizontally

26. Benefits of intranets Cost-effective- Users can view information and data via web-browser rather than maintaining physical documents such as procedure manuals, internal phone list and requisition forms. This can potentially save the business money on printing, duplicating documents, and the environment as well as document maintenance overhead. Promote common corporate culture - Every user is viewing the same information within the Intranet. Enhance Collaboration - With information easily accessible by all authorized users, teamwork is enabled .

27. Benefits of intranets Cross-platform Capability - Standards-compliant web browsers are available for Windows, Mac, and UNIX. Immediate Updates- With an Intranet and providing your audience with "live" changes, they are never out of date , which can limit a company's liability.

28. INTERNET (WAN) In the past two decades, personal computers have played a significant role in our everyday lives. Its popularity and the increasing need for communication, resource sharing and information access led to the development of computer networks . This in turn, led to the evolution of Internet . Computer Networks : Collection (group) of computer connected together is called Computer Networks.

29. BASIC INTERNET TERMS Web Page Website : Browser Uniform Resource Locator Domain Name HyperText Internet Service Provider (ISP ) Web Server

30. TYPES OF INTERNET CONNECTION The modem must be connected to a telephone line to access the web. Some of the common types of Internet access are: Dial-up ISDN (Integrated Services Digital Network) Cable Modem Leased Line DSL (Digital Subscriber Line) Service Broadband

31. INTERNET SERVICES IRC, Chatting Internet Telephony Telnet Mailing List FTP E-Mail Newsgroups Commerce Internet

32. World Wide Web (WWW) Electronic Mail (E-mail) File Transfer Protocol (FTP) Telnet Internet Relay Chat (IRC) Chatting and Instant Messaging Internet Telephony Video Conferencing Commerce through Internet Newsgroups (Usenet) INTERNET SERVICES