1 / 29

Data Communications

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

JasminFlorian
Download Presentation

Data Communications

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

  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 • Requirement / development of new services • advances in technology • significant change in requirements led to: • emergence of high-speed LANs • corporate WAN needs • Use of digital electronics

  4. A Communications Model

  5. Key Communications Tasks

  6. Data Communications Model

  7. Transmission Medium • selection is a basic choice • internal use entirely up to business • long-distance links made by carrier • rapid technology advances affects choice • fiber optic – high capacity, getting cheaper • 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) • 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 • packet switching • frame relay • 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 • 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. Types of connections: point-to-point and multipoint

  17. Categories of topology

  18. A fully connected mesh topology (five devices)

  19. A star topology connecting four stations

  20. A bus topology connecting three stations

  21. A ring topology connecting six stations

  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 • Star • Bus • 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 • applied to tactical radio & satellite nets also • had a need for interoperability • 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

More Related