Overview of Data Communication and Computer Networks 1

Overview of Data Communication and Computer Networks 1

n n n When we communicate, we are sharing information. This sharing can be local or remote. Between individuals, local communication usually occurs face to face, while remote communication takes place over distance. 2

n The term telecommunication, which includes telephony, telegraphy, and television, means communication at a distance (tele means "far“ in Greek) The effectiveness of a data communications system depends on four fundamental characteristics: delivery, accuracy, timeliness, and jitter. n 3

Data Communication: Definition n Data Communication: Transfer of data from one device to another via some form of transmission medium. 4

Data Communication Hi, how are you? Hi, how are you? Computer 01010001 5

Components in Communication 1 Message Hi, how are you? 5 Protocol 2 Sender 3 Receiver 4 Medium 6

Data Representation n Numbers 8/16/32 bit integers n floating point n n n ASCII, Unicode Images n n 2 Text n n 150 255 Bit patterns, Graphics formats JPG/GIF/etc Audio Samples of continuous signal Video Sequence of bitmap images 7

Protocols and Standards n Protocol n A set of rules governing data communications Syntax: format of data block n Semantics: meaning of each section n Timing: speed and sequencing n n Standards n De facto (in practice) standards not approved but widely adopted n De jure (in law) standards approved by an organization 8

Direction of Data Flow n Simplex: One direction only data flow Monitor Server data flow Keyboard 9

Direction of Data Flow n Half Duplex: Both directions, one at a time data flow at time 1 data flow at time 2 n E. g. , walkie-talkies 10

Direction of Data Flow n Full Duplex: Both directions simultaneously data flow n n E. g. , telephone Can be emulated on a single communication link using various methods 11

Types of Connections n n Point-to-point Multipoint (multidrop) 12

Point-To-Point Connection 13

Multipoint Connection Wireless 14

Topology n Topology: physical or logical arrangement of devices Point-to-point n Mesh n Star n Bus n Ring n Hybrid n 15

Point-to-Point Connection 16

Fully Connected Mesh Topology E A D B C 17

Fully Connected Mesh Topology 18

Fully Connected Mesh Topology n Pros: n n n Dedicated links Robustness Privacy Easy to identify fault Cons: n n n A lot of cabling I/O ports Difficult to move 19

Star Topology A D Hub B Drop C Drop 20

Star Topology A D Switch B C 21

Star Topology A D Hub B C 22

Star Topology n Pros: n n n Hub n n n One I/O port per device Little cabling Easy to install Robustness Easy to identify fault Cons: n n Single point of failure More cabling still required 23

Bus Topology Drop line Tap Terminator 24

Bus Topology A B C D 25

Bus Topology 26

Bus Topology n Pros: n n n Little cabling Easy to install Cons: n n n Difficult to modify Difficult to isolate fault Break in the bus cable stops all transmission 27

Ring Topology C D B A 28

Ring Topology 29

Ring Topology n Pros: n n n Easy to install Easy to identify fault Cons: n n Delay in large ring Break in the ring stops all transmission 30

Hybrid Topologies 31

Networks n Network: a set of devices connected by media links Laptop Workstation Media Links Server Printer Scanner 32

Network Categories n n n Local Area Network (LAN) Wide Area Network (WAN) Metropolitan Area Network (MAN) 33

Local Area Networks n Network in a single office, building, or campus 34

Wide Area Networks n Network providing long-distance communication over a country, a continent, or the whole world 35

Metropolitan Area Networks n Network extended over an entire city Bangkhen Kampangsaen 37

Network of Networks Company B Company A Network Interface Card (NIC) Company C Company D 38

Internetworking n n n How to allow devices from different standards to communicate Gateways/routers – devices capable of communicating in several standards These become "network of networks" 39

Internetworks n Two or more networks connected become an internetwork, or internet Network 1 Network 2 Gateway Network 3 n Example: The Internet 40

The Internet n n The largest internetwork (network of networks) in the world Devices communicating with TCP/IP protocol suite Stanford U. of Utah UC Santa Barbara UCLA 41

Summary n Data communication n n Protocols and standards Computer networks Topologies n LAN/MAN/WAN n n Internetworks (networks of networks) 42