Business Data Communications, Fourth Edition

Business Data Communications, Fourth Edition Chapter7: NetworkConcepts

Learning Objectives • Define the terms used when describing a network and its components • List the differences among circuit-switching, message-switching, packet-switching, and cell-switching networks • List the types of routing techniques used to move data through a network Chapter 7: Network Concepts 2

Learning Objectives • Describe the difference between a public network and private network • Illustrate the difference between a LAN and a WAN • Describe the functions of the Internet and intranets Chapter 7: Network Concepts 3

Learning Objectives • Describe the characteristics that distinguish a distributed network from other types of networks • List the types of distributed processing • Describe the types of files used in distributed systems Chapter 7: Network Concepts 4

Introduction • Basic concepts and terminology are needed for a foundation of the study of networks • Network switching and routing is critical to network operation • Network ownership • Types of networks • LANs • WANs • Internet • Intranets • Distributed Networks Chapter 7: Network Concepts 5

Basic Network Concepts • Network – the interconnection of devices for communications • Servers (hosts) – independent computer systems • Node – device with a network address • Link – connection between adjacent nodes • Path – series of links • Circuit – End-to-end connection (made up of links and paths) Chapter 7: Network Concepts 6

Chapter 7: Network Concepts 7

Networking Techniques • Non-switched network – Point-to-point link • Switched Networks – Nodes interconnected • Circuit-Switching • Dedicated path • Entire circuit must be available • Telephone network • Inefficient for data transmission • Used for intermittent data transmission Chapter 7: Network Concepts 10

Networking Techniques • Switched Networks • Message-switching • No dedicated circuit required • Messages pass through many nodes to the destination • Store-and-forward technique used • Similar to post office mail delivery • Some delays in delivery may occur Chapter 7: Network Concepts 12

Networking Techniques • Switched networks • Packet-switching • Similar to message-switching, but uses a fixed-size message, called a “packet” • All packets are the same length • Network performance is much better than on a message-switching network • Pipelining used • Instructions are available as soon as necessary to the receiving computer • Provides faster execution time Chapter 7: Network Concepts 14

Networking Techniques • Switched Networks • Packet-switching – Types • Datagram services – each packet treated independently • Switched Virtual Circuit (SVC) – logical connection established prior to transmission • Permanent Virtual Circuit (PVC) – permanent circuit, no call setup is needed Chapter 7: Network Concepts 17

Networking Techniques • Switched Networks • Cell-switching • Used in Asynchronous Transfer Mode (ATM) networks • Cell-based network • Cell is 53 bytes long • Uses a virtual circuit • More in Chapter 13 Chapter 7: Network Concepts 18

Networking Techniques • Broadcast Networks • Use radio waves • Packet radio network • National Weather Service uses it to gather information from remote sites • Also used on the U.S. Space Shuttle and the International Space Station (ISS) • Special modem is used • Uses the AX.25 protocol and TCP/IP Chapter 7: Network Concepts 19

Routing • Computers use routing to send data to the correct destination • Centralized routing • One node is the network routing manager • Central point of failure • Routing information may be far from central node • Distributed routing • Each node contains a routing table • Increased traffic on network due to sending updates to other nodes • Routing table used to determine best route Chapter 7: Network Concepts 20

Routing • Types of Routing • Static routing • Same route used from source to destination • Route is fixed • Data may not arrive if path is blocked • Dynamic (adaptive) routing • Route changes based on conditions on the network • The network software selects the best route • Broadcast routing • Transmit to all nodes in the network (flooding) Chapter 7: Network Concepts 22

Network Ownership • Private network • Built by a company for its own use • Public network • Built and owned by common carrier • Telephone network, ISPs, AOL • Virtual Private Network (VPN) • Private network that uses public carrier lines • Packet distribution network (PDN) • Use X.25 protocol • Packet-switching technology on public or private networks • Provide high-speed lines between nodes Chapter 7: Network Concepts 24

Network Types • Local Area versus Wide Area Networks • Local Area Network (LAN) • Nodes in a small area • Campus, office, building • Widely used • Owned entirely by the organization in which it resides Chapter 7: Network Concepts 25

Network Types • Local Area versus Wide Area Networks • Wide Area Network (WAN) • Nodes over a large area • Often uses common carrier lines • Originally developed for mainframe networks • Many functions taken over by LANs • Still exist for many applications Chapter 7: Network Concepts 26

Network Types • The Internet and Intranets • Internetwork (internet) • Refers to networks that are connected • Internet (uppercase I) • A specific, named network • World Wide Web • Intranet • Uses Internet technology on an internal network • Company calendars and forms may be posted Chapter 7: Network Concepts 28

Network Types • The Internet and Intranets • Access • Internet – open to anyone with proper access • Intranet – used only by selected people • Firewall – allows only authorized access to a network • Applications • Web pages (viewed using a Web browser) • John Deere (conversion of legacy systems) • Federal Express (customer access to shipping information) • Olivetti (employee collaboration over the Web) Chapter 7: Network Concepts 30

Distributed Systems • Evolution from centralized to distributed systems • Definition of Distributed Systems • Systems with independent processing capability • Spread across multiple locations • Processors function independently • Components: hardware, operating system software, application software, data • Control is centralized or distributed • Data is centralized or distributed Chapter 7: Network Concepts 31

Distributed Systems • Characteristics of Distributed Systems • Use smaller computers rather than large, centralized systems • Increased user involvement • Modular – an individual component can be easily replaced • User response time is faster • System is more flexible (uses many manufacturer’s equipment) Chapter 7: Network Concepts 37

Distributed Systems • Types of Distributed Systems • Distribution by Location • Hardware at many different geographic locations • Uses a network to communicate • Functions such as backup may not be done as required, due to lack of training • On-site specialists may be needed Chapter 7: Network Concepts 39

Distributed Systems • Types of Distributed Systems • Distribution by Function • Specific computers at different sites do different functions for the corporation • Individual departments have their own computers, isolated from other departments • May cause problems if data needs to be shared among departments Chapter 7: Network Concepts 41

Distributed Systems • Types of Distributed Systems • Distribution by Control • Refers to management of programmers and data • Creation of application programs may need to rely on data from another department • Systems need to work together Chapter 7: Network Concepts 43

Distributed Systems • Types of Distributed Systems • Distribution by Processing • System designed around how data is processed • Processing of data is done at many sites • Hierarchical distributed system (Vertical system) • Some processing on central computer, some done at a remote, smaller computer • Horizontal distributed system (Peer computers) • Computer systems are equal Chapter 7: Network Concepts 44

Distributed Systems • Implementation of Distributed Systems • File Handling • Distributed File System (DFS) is software used • Location independence means any application program can access data, no matter where it resides • Different architectures and operating systems must allow access to the data • Must overcome contention on the network for file access • Security of the file is also handled by the DFS • Maintains file directory of all files in system Chapter 7: Network Concepts 49

Distributed Systems • Data Distribution • Data may be stored in files or databases • Single storage site in centralized configuration • Copies of data kept at remote sites • Local computers may have independent file systems • May create inconsistent data • Must synchronize all data periodically • Separate data systems cannot share data Chapter 7: Network Concepts 50

Business Data Communications, Fourth Edition