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Data Communications Eighth Edition by William Stallings Chapter 1 – Data Communications, Data Networks, and the Internet.

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Presentation on theme: "Data Communications Eighth Edition by William Stallings Chapter 1 – Data Communications, Data Networks, and the Internet."— Presentation transcript:

1 Data Communications Eighth Edition by William Stallings Chapter 1 – Data Communications, Data Networks, and the Internet

2 Data Communications, Data Networks, and the Internet  The fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point - The Mathematical Theory of Communication, Claude Shannon

3 Contemporary Data Comms  Trends influenced by: traffic growth at a high & steady rate traffic growth at a high & steady rate Requirement / development of new services Requirement / development of new services advances in technology advances in technology  significant change in requirements led to: emergence of high-speed LANs emergence of high-speed LANs corporate WAN needs corporate WAN needs Use of digital electronics Use of digital electronics

4 A Communications Model

5 Key Communications Tasks Transmission system utilizationAddressing InterfacingRouting Signal generationRecovery SynchronizationMessage formatting Exchange managementSecurity Error detection and correctionNetwork management Flow control

6 Data Communications Model

7 Transmission Medium  selection is a basic choice internal use entirely up to business internal use entirely up to business long-distance links made by carrier long-distance links made by carrier  rapid technology advances affects choice fiber optic – high capacity, getting cheaper fiber optic – high capacity, getting cheaper Wireless - mobility Wireless - mobility  transmission cost is still high  hence interest in efficiency improvements – multiplexing and compression

8 Networking  growth of number & power of computers is driving need for interconnection  also seeing rapid integration of voice, data, image & video technologies  two broad categories of communications networks: Local Area Network (LAN) Local Area Network (LAN) Wide Area Network (WAN) Wide Area Network (WAN)

9 Wide Area Networks  span a large geographical area  rely in part on common carrier circuits  alternative WAN technologies used include: circuit switching circuit switching packet switching packet switching frame relay frame relay Asynchronous Transfer Mode (ATM) Asynchronous Transfer Mode (ATM)

10 Circuit Switching  uses a dedicated communications path established for duration of communication  comprising a sequence of physical links  with a dedicated logical channel  eg. telephone network

11 Packet Switching  data sent out in sequence  small chunks (packets) of data at a time  packets passed from node to node between source and destination  used for terminal to computer and computer to computer communications

12 Frame Relay  packet switching systems have large overheads to compensate for errors  modern systems are more reliable  errors can be caught in end system  Frame Relay provides higher speeds  with most error control overhead removed

13 Asynchronous Transfer Mode  ATM - evolution of frame relay  fixed packet (called cell) length  with little overhead for error control  anything from 10Mbps to Gbps  constant data rate using packet switching technique with multiple virtual circuits

14 Local Area Networks  smaller scope Building or small campus Building or small campus  usually owned by same organization as the attached devices  data rates much higher within  switched LANs, eg Ethernet  wireless LANs

15 Metropolitan Area Networks  MAN  middle ground between LAN and WAN  private or public network  high speed  large area – city or metro

16 1.16 Types of connections: point-to-point and multipoint

17 1.17 Categories of topology

18 1.18 A fully connected mesh topology (five devices)

19 1.19 A star topology connecting four stations

20 1.20 A bus topology connecting three stations

21 1.21 A ring topology connecting six stations

22 1.22 A hybrid topology: a star backbone with three bus networks

23  # In a network with 25 computers, which topology would require the least extensive cabling? Mesh Mesh Star Star Bus Bus Ring Ring # For six devices connected in mesh, how many cables are needed? How many ports are needed for each device? # What is the consequence if a connection fails for five devices arranged in: a) Mesh b) Star (excluding hub) c) Bus d) Ring

24 The Internet  Internet evolved from ARPANET first operational packet network first operational packet network applied to tactical radio & satellite nets also applied to tactical radio & satellite nets also had a need for interoperability had a need for interoperability led to standardized TCP/IP protocols led to standardized TCP/IP protocols

25 Internet Elements

26 Internet Architecture

27 Example Configuration

28 MCQ  The protocol/medium/signal/all the above is the physical path over which message travels.  The information to be communicated in a data communications system is the medium/protocol/message/transmission.  Frequency of failure and network recovery time after a failure are measures of the performance/reliability/security/feasibility of a network.

29 Summary  introduced data communications needs  communications model  defined data communications  overview of networks  introduce Internet


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