Networks: Superhighways for digital information

1. Networks: Superhighways for digital information What You Will Learn • Main types of computer networks • How computer connections increase the value of an organizations information technology investment • The importance of protocols in a computer network • Contrasts of circuit switching and packet switching as well as their strengths and weaknesses • Differences between peer-to-peer and client/server LANs • The most popular LAN protocol and it’s benefits • Business applications of WANs

2. What is a computer network? • A computer network consists of two or more computers linked together to exchange data and share resources • Main-frame computer systems do not fit the definition; Composed of main-frame and terminals

3. What are the types of networks? Metropolitan area network (MAN) Local area network (LAN) • Links computers within a building or group of buildings • Uses direct cables, radio or infrared signals • Links computers within a major metropolitan area • Uses fiber optic cables Wide area network • Links computers separated by a few miles or thousands of miles • Uses long-distance tranmission media

4. Why have a computer network? Reduce hardware costs Share applications • Users share software • File server enables all users to work with the same application program • Users share equipment Connects people • People can work together without being at the same location • Groupware enables sharing of schedules and communications Build information resources • Users create common pools of data that can be accessed by employees

5. Network Fundamentals

6. What are a computer network’s basic components? • Physical media • Cables- Telephone lines, coaxial cable, microwave, satellites, wireless, and fiber optic cables • Routers- Devices that examine the data transmitted and send it to its destination • Switches- High speed electronic switches maintain connections between computers • Protocols- Standards that specify how network components communicate with each other

7. What are Routers? • The routers determine where to send information from one computer to another. • Routers are specialized computers that send your messages and those of every other Internet user speeding to their destinations along thousands of pathways. • What is incredible about this process is that a message can leave one computer and travel halfway across the world through several different networks and arrive at another computer in a fraction of a second!

8. What are circuit switching and packet switching? Packet switching Circuit switching • Outgoing message is divided into fixed sized data units called packets • Packets are numbered and addressed to receiving computer • Routers examine the packets and send them to their destination • Network creates an end-to-end circuit between the sending and receiving computers • Same as voice networks • Suited to voice and real-time videoconferencing

9. Advantages and disadvantages of circuit switching and packet switching?

10. What are network protocols? • Protocols are fixed, formalized exchanges that specify how two dissimilar network components can establish communication • Proprietary protocols- Standards developed and protected by hardware manufacturers; Need to by all hardware from same manufacturer for network to function • Open protocols- Nonproprietary protocols; Established by independent organizations; Any hardware supporting the protocols will operate on the network

11. Local Area Networks (LAN)

12. What are local area networks (LAN)? • LANs connect computers and peripherals within a building or group of buildings • Users can access software, data and peripherals • Require special hardware and software • Computers connected to a LAN are called workstations or nodes • Different types: • Peer-to-peer • Client-server

13. What hardware and software do LAN computers need? Hardware Software • Network interface card (NIC)- Inserted into computer’s expansion slot • Operating system that supports networking (Unix, Linux, Windows, Mac OS) • Additional system software

14. What is a peer-to-peer LAN? • All computers on the network are equals • No file server • Users decide which files and peripherals to share • Isn’t suited for networks with many computers • Easy to set up; Home networks

15. What is a client-server network? • Typical corporate network • Various topologies or physical layouts • Requires file servers, networked computers (clients) and network operating system(NOS) • Clients send requests to servers for programs, data and to access peripherals

16. What is a file server? • A high speed, high capacity computer • Contains the network operating system ( Novell Netware, Windows NT, XP Server) • Contains network versions of programs and large data files

17. What are the LAN topologies? • Topologies resolve the problem of contention or users trying to access the LAN at the same time • Collisions or corrupt data occurs when computers use the network at the same time Bus topology Star topology • Called daisy chain • Every workstation connected to a single bus cable • Resolves collisions through contention management • Difficult to add workstations • Contains a hub or central wiring concentrator • Easy to add workstations • Resolves collisions through contention management Ring topology • All workstations attached in a circular arrangement • A special unit of data called a token travels around the ring • Workstations can only transmit data when it possesses a token

18. Types of LAN topologies Bus Topology Star Topology Ring Topology

19. What are LAN protocols? • Standards that govern the layers of the protocol stack • Lower layer protocols deal with contention between computers • Lower layer protocols are: • Ethernet • LocalTalk • Token ring • High layer protocols handle the network functions • Examples of high layer protocols are: • AppleTalk • IPX/SPX • NetBeui • TCP/IP

20. Wide Area Networks (WAN)

21. What are wide area networks (WAN)? • Similar to long-distance telephone systems • Have local access number called point of presence (POP) • Contains long-distance trunk lines called backbones

22. What is point of presence (POP)? • A WAN network connection point that enables customers to access the WAN by making a local telephone call • Uses leased lines, ISDN, ASDL, DSL or T1 lines to transmit data • A type of POP that uses packet switching is called permanent virtual circuit (PVC)

23. What are backbones? • High capacity transmission lines that carry WAN traffic • Backbones are regional, continental or transcontinental

25. What are the types of WANs? Internet Public Data Network (PDN) • Backbone providers charge fees to Internet Service Providers (ISP) • ISPs sell subscriptions to users • Not secure • Not ideal for businesses • A for-profit data communications network • Fees paid on a per-byte-transferred basis • Good security • High bandwidth Private Data Network • Used by corporations, banks and governments • Not open to the public • Most secure type of WAN • Virtual private network- Lines are leased to a single company

26. Types of WAN applications LAN-to-LAN Transaction Acquisition • WANs used to connect LANs at two or more geographic locations • Used to connect branches of a company into one network system • Information about transaction instantly relayed to corporate headquarters • Use point-of-sale (POS) terminal as cash register Electronic Data Interchange (EDI) • Standards that specify how companies set up business-to-business transactions • Speeds ordering, invoicing and payments

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