1 / 24

Chapter 1: Data Communications & Networking: Overview

COE 341: Data and Computer Communications (3-0-3). Chapter 1: Data Communications & Networking: Overview. Acknowledgements. Many figures, slides, and course notes were made available by: Pearson Prentice-Hall (Publishers) Data & Computer Communications, W. Stallings

georgettesilva
Download Presentation

Chapter 1: Data Communications & Networking: Overview

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. COE 341: Data and Computer Communications (3-0-3) Chapter 1: Data Communications & Networking: Overview

  2. Acknowledgements Many figures, slides, and course notes were made available by: • Pearson Prentice-Hall (Publishers) • Data & Computer Communications, W. Stallings • McGraw-Hill (Publishers) • Data Communications & Networking, B. Forouzan • Previous Course Offerings at COE, KFUPM by: • Dr. Marwan Abu-Amara • Dr. Taha Landolsi • Dr. Ashraf Mahmoud

  3. Contents • Introduction • Merging of computing and communications • Integration of various types of data: Text, Pictures, Audio, Video • Communications Model • Main blocks and functionality • Communication Tasks • Data Communication • Data Communication Networks • Wide Area Networks (WAN) • Circuit switching • Packet switching • Local Area Networks (LAN) • Metropolitan Area Networks (MAN)

  4. Merging, Integration, and Blurring…. • Merging of computing and communications • Computers communicate and communication devices (e.g. cell phones, routers) compute!… • Integration of various types of information: Voice, Video, Text, Pictures, Data • Before, they used to be handled by different dedicated networks, e.g. telephone network for voice only • Blurring of boundaries in computing and communications • Microcomputer, Minicomputer, …. • Networks: LAN, MAN, WAN, …

  5. Routers, Switches Communication Hosts • Main purpose of a communication system is: “Reliable exchange of data between two entities” • 3 main areas: • Standards and Protocols • Networking • Covers technology & architecture of communication networks • Networks categorized into: LANs, MANs & WANs • Data Communications(Main Concern of COE 341) • Reliable & efficient data communication over a link • Covers signal transmission, transmission media, signal impairment, signal encoding, synchronization, error detection, data link control (error and flow), multiplexing

  6. Communication over a point-to-point link: A simplified model Generate Data Data to Signals Signals to Data Receive Data

  7. Noise, Distortion Interference Attenuation Signal Data 1101... Data 1101… Simplified Communications Model • Source (e.g. PC) • Generates data to be transmitted • Transmitter • Converts data into transmittable signals (modulation, encoding) • Transmission System (medium + equipment) • Carries signals, but introduces attenuation, noise, interference, etc. • Receiver • Converts received signals into data (demodulation, decoding) • Destination • Takes and uses incoming data

  8. Noise, Distortion Interference Attenuation Signal Data 1101... Data 1101… This deceptive simplicity hides many important tasks!(See pages 11-13 of the textbook for a good description) = Tasks covered in some detail in this course

  9. Simplified Data Communications Model Speech, Speech, • Information (say ASCII chars)  Data (bits) Signal (say 1 KHz signal) • Encoding of data g(t) as signals s(t) (Ch. 5) • Signal, s(t), should suit the transmission medium (Ch. 3 & 4) • Transmission Impairments: attenuation, noise, distortion, etc. (Section 3.3) • Is received data, g’, identical to original data, g ? Error detection(Ch. 6) • If not, Error correction at RX may help restore g • Otherwise, request retransmission of message (Error control), Also flow control(Ch. 7) • Better utilization of link capacity by multiplexing many channels (Multiplexing) (Ch 8)

  10. Networking: Why do we need networks? • Direct point-to-point communication is not always possible/practical/efficient: • Communicating entities can be too far apart for a single link • A large set of communicating entities (e.g. telephones) would need impractically large number of connections (full connectivity for N nodes needs N (N – 1) / 2 links) • Not all links would be needed all the time! • Solution is a communication network: • Wide Area Network (WAN) • Metropolitan Area Network (MAN) • Local Area Network (LAN)

  11. Wide Area Networks (WAN) • Large geographical area, e.g. the world • Usually not owned by one organization • Relies in part on common carrier circuits • Alternative technologies • Circuit switching, e.g. telephone network, ISDN* • Packet switching, e.g.: • Frame relay • Cell relay (Asynchronous Transfer Mode (ATM)) • Example:? * Integrated Services Digital Network

  12. WAN Technologies: Circuit Switching • Circuit switching was widely used for the public telephone networks for voice communication. • Dedicated path is established before the call (session) starts and lasts for its duration • Switching and transmission resources are committed for exclusive use of that call throughout its duration • OK with telephony, as people keep talking till end of call • Not the case with many computer data communication scenarios (bursty nature), e.g. Web browsing • Advantage: Reliable, predictable performance – Delay, data rate, etc. Once connection is established, end devices appear as if connected directly through a dedicated link • Disadvantage: Inefficient network utilization with computer type data communication

  13. Simple Switched Computer Network End-to-end transmission medium is a network Switching Is Physical Link Switching Nodes Host Network Computers (Switches) Computers

  14. WAN Technologies, Contd: Packet Switching (store and forward) • No dedicated circuit assigned for the full session duration • Data is split into small chunks (packets), each packet carries the destination address and a sequence number • Packets may travel different routes to the destination  arrive out of sequence, experiencedifferent delays, etc. • Packets are passed from node to node from source to destination (possibly on multiple routes simultaneously) • At destination, packets are assembled again to form the original message • Used for terminal-to-computer and computer-to-computer data communications • Possible problems for real-time traffic, e.g. telephony?: queuing delay, packet loss, etc. (Voice Over IP)

  15. Packet Switching Useful user data (payload) Additional header info addressing and control (overhead) Even if packets arrive out of sequence, they can still be re-assembled to reconstruct the message correctly at destination • Each packet carries: • Destination address • Sequence number indicating packet position • in original message

  16. Packet Switching (Store & Forward) Networks • Datagram (connectionless)Approach: • No pre-planned route 2. Virtual Circuit (connection) Approach: Frames follow one pre-planned route

  17. Evolution of Packet Switching Technology • Older packet switching systems (X.25) had a large overhead (redundancy) for handling errors • This limited the usefuluser data rates to 64 kbps • Now, modern transmission systems are more reliable ( fewer bit errors) • And remaining few errors can be easily handled by higher layers at end systems • Reducing data redundancy and processing at lower layers reduces the overhead, speeds up communication and increases useful (user) data rates

  18. Newer forms of Packet Switching:1. Frame Relay • Most overhead for error control is stripped off • Variable-length packets (called frames) • User data rates increased from 64KB to 2 Mbps

  19. Newer forms of Packet Switching: 2.ATM Cell Relay • Used on Asynchronous Transfer Mode (ATM) networks • An evolution of frame relay • Little overhead for error and flow control • Fixed-length packets (called cells): 48 bytes data + a 5-byte header • Higher data rates than frame relay:10 Mbps-Gbps • Handles data for various types of information, e.g. speech, video, text, etc.

  20. Local Area Networks (LANs Vs WANs) • Smaller geographical scope • A building or a small campus • Usually owned by the same organization that owns the attached devices (e.g. KFUPM) • Data rates are higher (this is made possible by the shorter distances- small total attenuation  can afford using higher frequencies, e.g.: Ethernet: 10 Mbps -10 Gbps over 100’s of meters • Originally use a shared broadcast medium, e.g. coaxial cable • But now some switched systems (originally WAN technology) are being introduced (Boundary Blurring!) • Example: The Ethernet (IEEE 802.3 standard)

  21. Some LAN Topologies:(For further readings, see Part 4 of the textbook) Bus Ring Tree Star

  22. Recent LAN Configurations(For further readings: see Part 4 of the textbook) • Switched LAN • Switched Ethernet • ATM LAN • Fibre Channel • Wireless LAN • Advantages: Mobility, Ease of installation • Example: WiFi (IEEE 802.11 standard)

  23. Metropolitan Area Networks (MAN) • Requirements: Large capacity (data rate) at low cost and high efficiency to cover the geographical area of say a city • Can be a private or public network • Middle ground between LAN and WAN: • Stretching of LAN technology • Scaling down of WAN technology • Now also going wireless!: • Example: WiMAX (IEEE 802.16 standard)

  24. Example NetworkingConfiguration:Two ways of accessing the Internet 1. Residential Access • - Tel Line • - ADSL Line • Cable Switched LAN Network 2. Through An access Network

More Related