Data Communication and Networking

1. Chapter 12 Data Communication and Networking

2. Communication • sending or receiving information • Beating of drums • Mirrors reflecting sunlight • Homing pigeons • Telegraph, telephone • Computers … Data Communication

3. Data Communication

4. DATA COMMUNICATION • Exchange of data between two devices • wired or wireless transmission medium • Communication system (collection of hardware, software …)

5. Five components of a data Communication System

6. Data Transmission Modes

7. Analog & Digital Transmission

8. Analog & Digital Transmission … • Analog to analog • Voice (Analog Data) Telephone  Analog Signal • Digital to analog • PC ( Digital Data) Modem  Analog Signal • Analog to digital • Voice ( Analog Data)  CODEC  Digital Signal • Digital to Digital • PC ( Digital Data) Digital Transmitter  Digital Signal • Analog • Signals- Sine waves • Amplitude • Frequency • Wavelength

9. Data Communication Measurement • It Changes

10. Transmission Media

12. Radio Frequency Propogation

14. Modulation

15. Multiplexing

16. Multiplexing …

17. Synchronization- Controlling time • Asynchronous Transmission • Each character of data is treated independently • Synchronous Transmission • For sending large blocks of data • Control schemes • Character-oriented • Bit-oriented

18. Switching • 4 Employee Office • Direct Lines to each of them! • Point to point communication Impractical & Wasteful Route calls by making temporary connection!

19. Use Switches or Exchanges Some switches are directly connected to a comminication device while others are dedicated to route/forward information

20. Circuit switching • Major Attributes • Dedicated fixed BW channel • Data (sent/received) path is determined by the circuit • Data path does not change within the lifetime of connection • Simple method. Used in Public Service Telephone Network (PSTN) • Disadvantage? • Waste when there is no data flowing • Cannot change the circuit after it is established even if there are other (cheaper) routes possible

21. Packet Switching • Major Attributes • Focuses on data communication (vs. voice) • Break data into packets • Package Assembler and Disassembler (PAD) • Packets from a single message will not necessarily follow the same route • Packet Header • Destination • Priority • … • Packet Switching Exchange (PSE) • Efficient? “Message Switching” is obsolete

22. Computer Network • Standalone versus Networked Environment • How can we connect (physically)? • Network Operating Systems • Manage multiple computers on a network • Client/Server (NOS) • Client request and server serves • Access to resources • Peer to peer network (NOS?) • Equal peer nodes • Both server & client • Music/File sharing!

23. Client/Server • How it works • Client sends request for service to server • Server fulfills request and send results to client • Client and server may share processing • Benefits • Reduces volume of data traffic • Allows faster response for each client • Nodes can be less expensive computers

24. Standalone Vs. Networked Environment Topology – Physical layout of components

25. Computer Network • LAN • MAN • WAN • CAN

26. LAN- Local Area Network • Connections over short distances through communications media • Connecting LANs • Bridge – connects networks with similar protocols • Router – directs traffic via best path • IP switches • Replacing routers • Less expensive • Faster • Gateway • Connects LANs with dissimilar protocols • Performs protocol conversion

27. WAN- Wide Area Network • Link computers in geographically distant locations

28. Network Topology • Bus topology • Ring topology • Star topology • Tree topology • Mesh topology

29. OSI Model • Textbook P 445

30. OSI Model … • Layer 1 - Physical • Defines the cable or physical medium itself • e.g., thinnet, thicknet, unshielded twisted pairs (UTP). • All media are functionally equivalent. • Layer 2 - Data Link • Defines the format of data on the network • A network data frame, aka packet, includes • checksum, • source and destination address, and • data. • The largest packet that can be sent through a data link layer defines the Maximum Transmission Unit (MTU). net interface to handle connections to the outside world, and a loopback interface to send packets to itself.

31. OSI Model … • Layer 3 - Network • NFS uses Internetwork Protocol (IP) which is responsible for routing, directing datagrams from one network to another. • The layer may have to break large datagrams, larger than MTU, into smaller packets and host receiving the packet will have to reassemble the fragmented datagram. • Layer 4 - Transport • Subdivides user-buffer into network-buffer sized datagrams • enforces desired transmission control. • Two transport protocols sits at this layer • Transmission Control Protocol (TCP) • User Datagram Protocol (UDP) • Reliability and speed are the primary difference between these two protocols.

32. OSI Model … • Layer 5 - Session • Defines the format of the data sent over the connections • The NFS uses the Remote Procedure Call (RPC) for its session protocol • RPC may be built on either TCP or UDP • Layer 6 - Presentation • External Data Representation (XDR) sits at this level. • Converts local representation of data to its canonical form and vice versa. • The canonical uses a standard byte ordering and structure packing convention, independent of the host. • Layer 7 - Application • Provides network services to the end-users. Mail, ftp, telnet, DNS, NIS, NFS … network applications.

33. Network Devices • NIC • Repeater • Hub • Bridge • Switch • Router • Gateway • P449