1. 1. Introduction

2. Data Communication Data Data Communication
Information presented in whatever form is agreed upon by the parties creating and using the data
Binary information units (0s and 1s)
Data Communication
Exchange of data between two devices via transmission medium
Fundamental Characteristics
Delivery: deliver data to correct destination
Accuracy: deliver data accurately
Timeliness:
Deliver data in a timely manner
Delivering data as they are produced, in the same order that they are produced, and without significant delay
Real-time transmission

3. Data Communication System Component

4. Data Communication System Components (cont.)
Message
Information (data) to be communicated
Sender
Device sending data message
Receiver
Device receiving message
Medium
Physical path by which a message travels
Protocol
Set of rules governing data communication
Agreement between communicating devices

5. Direction of Data Flow Simplex Unidirectional communication
Keyboard, monitor

6. Direction of Data Flow (cont.)
Half-duplex
Both transmit and receive, but not at the same time
Walkie-talkie

7. Direction of Data Flow (cont.)
Full-duplex
Transmit and receive simultaneously
Telephone network

8. Network
Network
A set of devices (nodes) connected by communication links

9. Network Criteria Performance Reliability Security
Throughput, delay, jitter, loss…
Factors including number of users, type of transmission medium, hardware, software
Reliability
Frequency of failure, recovery time of a network after a failure, network’s robustness in a catastrophe
Security
Protecting data from unauthorized access

10. Physical Structure Type of Connection Point-to-Point
Provide a dedicated link between two devices
Reserve entire capacity of the channel for transmission between two devices

11. Physical Structure (cont.)
Type of Connection (cont.)
Multipoint (or Multidrop)
More than two devices share a single link
Spatially shared: several devices use link simultaneously
Timeshare:users must take turns

12. Physical Structure (cont.)
Physical Topology
The way in which a network is laid out physically

13. Physical Structure (cont.)
Physical Topology (cont.)
Mesh
Every device has a dedicated p-to-p link to every other device
Guarantee data load between two devices
Robust, meaning one link failure does not halt entire system
Privacy or security
Easy fault identification and fault isolation
Amount of cabling and number of I/O ports required (n(n-1)/2)

14. Physical Structure (cont.)
Physical Topology (cont.)
Star
Dedicated p-to-p link to central controller (hub)
Less expensive than mesh
Easy to install and reconfigure due to only one link and one I/O port
Robustness due to easy fault identification and fault isolation
More cabling than other topologies (tree, ring, bus)
Single failure problem

15. Physical Structure (cont.)
Physical Topology (cont.)
Bus
Multipoint configuration
Ease of installation
Limited number of taps a bus can support and distance
Difficult reconfiguration and isolation

16. Physical Structure (cont.)
Physical Topology (cont.)
Ring
Dedicated p-to-p configuration with two devices on either side
Easy to install and reconfigure
Simplified fault isolation
Unidirectional traffic
A break in the ring can disable entire network

17. Categories of Networks
Classification of interconnected processors by scale

18. Categories of Networks (cont.)
Local Area Network (LAN)
Privately owned and limited size to a few kilometers
Allow resources to be shared between PCs or workstations
Bus, ring or star

19. Categories of Networks (cont.)
Metropolitan Area Network (MAN)
Extend over an entire city
Single network or a means of connecting LANS into a larger network
(ex) Telco.s provide a popular MAN service called SMDS (Switched Multi-megabit Data Services)

20. Categories of Networks (cont.)
Wide Area Network (WAN)
Provide long-distance transmission of data over large geographical areas (country or continent)
Utilize public, leased, or private communication equipment
Enterprise Network
WAN that is wholly owned and used by a single company

21. Categories of Networks (cont.)
Internetworks
internetworks or internet
Collection of interconnected networks

22. Brief History of Internet
ARPANET
Advanced Research Projects Agency (ARPA) in the DOD : presented ideas of ARPANET, 1967
Reality : 1969 (UCLA, UCSB, SRI, U of Utah)
Birth of the Internet
Vint Cerf and Bob Kahn devised to interconnect networks, in 1972
Presented TCP concepts in 1973; later, TCP  splitting into TCP and IP
In 1983, TCP/IP became to official protocol for the ARPANET

23. Internet Today
More than 36 million hosts
More than 134,000 networks

24. Internet
Specific
worldwide
internet

25. Protocols Set of rules (conventions) governing data communications
Key Element
Syntax
Structure or format of data, meaning the order in which they are presented
Semantics
Meaning of each section of bits
Timing
Two characteristics: when data should be sent and how fast they can be sent
Entity
Anything capable of sending or receiving information

26. Standards Standard Categories De Jure standards De Facto Standards
Essential in creating and maintaining an open and competitive market and in guaranteeing national and international interoperability
Categories
De Jure standards
Legislated by an officially recognized body
De Facto Standards
Have not been approved by an organized body but have been adopted as standards through widespread use

27. Standard Organizations
Standards Creation Committees
International Standards Organization (ISO)
International Telecommunications Union-Telecommunication Standards Sector (ITU-T, formerly CCITT)
American National Standards Institute (ANSI)
Institute of Electrical and Electronics Engineers (IEEE)
Electronic Industries Association (EIA)

28. Standard Organizations (cont.)
Forum
Developed by special-interest groups to accommodate the need for working models and agreements and to facilitate the standardization process
Speed acceptance and use of technologies in telecommunications community
Frame relay forum, ATM forum and ATM consortium
Internet Society (ISOC) and Internet Engineering Task Force (IETF)
Regulatory Agencies
Government agencies regulating all communications technology
FCC

29. Internet Standards Internet Standard
A thoroughly tested specification that is useful to and adhered by those who work with the Internet
A specification begins as an Internet draft
Working document with no official status and six-month life-time
RFC (Request for Comment)
Recommendation from Internet authorities