1. Part I. Overview of Data Communications and Networking
Chapter 1. Introduction
COMP 3270 Computer Networks
Computing Science
Thompson Rivers University

2. Chapter Contents Data communications Computer networks The Internet
Protocols and standards

3. Learning Objectives Define data communications and networking.
Identify five components of data communication.
Identify three data flows.
Describe three network performance criteria.
Draw two types of connection with their examples.
Draw five categories of topology with their examples.
Explain four categories of networks with their examples.
Distinguish an internet and the Internet.
Describe the hierarchical organization of the Internet.
Define a protocol with the three key elements.
Explain the need of standards.
Relate protocols and standards in the Internet.

4. 1. Data Communications Definition of data communications Components
Data representation
Direction of data flow

5. Definition of data communications
The exchange of data between two devices via some form of transmission medium such as a wire cable.

6. Five components of data communication
Usually in packets

7. Sender, receiver Medium (link) Message
Electrical devices having some computing power
☺ Examples?
Medium (link)
Physical path
Digital/analog electric/electromagnetic signals
Message
Information to be exchanged in the form of packets (or called frames)
☺ How to be loaded on electric or electromagnetic signals?
☺ What happens if the data is lost?
In order to make two nodes exchange messages correctly, they need to use some agreed rules. That is called …
Protocol
Definition: A set of rules, which governs the exchange of data
Highly related to the format of packets being exchanged
☺ Is it software?

8. Data Representation In messages, On signals, Text Numbers Images Audio
Code: ASCII, Unicode, ISO, …
Numbers
Images
Audio
Video
On signals,
☺ How is information loaded on electric or electromagnetic signals passing through a transmission medium?
Encoding/Decoding.
☺ What happens if the information is lost during the transmission?

9. Direction of Data Flow Simplex Half-duplex Full-duplex
☺ Examples for each type?

10. 2. Computer Networks Distributed Processing Network Criteria
Physical Structures
Categories of Networks

11. Distributed Processing
A network is …
A set of nodes connected by communication links (transmission media or media links)
☺ Examples?
Most networks use distributed processing.
☺ What are the advantages of distributed processing?
More products
Fast
Fault tolerant
☺ What is parallel processing anyway?
☺ How are they different?
Grid computing >> cluster computing >> parallel computing

12. Network Criteria Performance Reliability Security
Transit time and response time
Bandwidth – related to transmission speed
Delay – related to transmission time
Jitter – variance of delay
Depends on
The number of users
The type of transmission medium
Hardware
Software
Reliability
Frequency of failure
Recovery time
Security
Unauthorized access

13. Physical Structure Type of connection (line configuration)
Point-to-point (not p2p communications)
Multipoint

14. Physical topology
Physical or logical arrangement of links: Mesh, star, bus, ring, hybrid

15. Physical topology Physical or logical arrangement of links
There are advantages and disadvantages in terms of
Speed
Installation cost
Fault tolerance ☺
Mesh
Point-to-point
Advantages?
Disadvantages?
Star ?
Bus
Multipoint
Ring

16. Categories of Networks
PAN
DAN
HAN
☺ LAN (?)
☺ MAN (?)
☺ WAN (?)
☺ WAN is the Internet?
☺ Is the Internet a WAN?
☺ Internetwork (or internet)?

17. LAN (Local Area Network)

18. LAN - cont.

19. MAN (Metropolitan Area Network)

20. WAN (Wide Area Network)

21. 3. The Internet
A Brief History
The Internet Today

22. A Brief History ARPANET: 1969 TCP: 1973
To provide data exchange between main frames in research labs
TCP: 1973
Split into TCP and IP, TCP/IP: 1978
WWW: late 1991
Commercial system: mid-1990s

23. The Internet Today ☺ Examples of services in the Internet?
☺ How many computers in the Internet?
☺ How many people use the Internet?
The Internet: A logical collection of ASes (Autonomous System) managed by ISPs (Internet Service Provider) AS
A set of logical IP networks, which is managed by an ISP
A unit for routing
Types
International AS
National AS
Regional AS
Local AS
AS-1
AS-2
AS-N

24. 1.4 Protocols and Standards
Standards Organizations
Internet Standards

25. Protocols ☺ Definition?
Protocols are concerned with what, how and when
Key elements
Syntax: the structure or format of the data to exchange
Header + body (oac payload) [+ trailer]
Semantics: the meaning of each section of bits
Timing: when and how fast
Type
Dest.
Addr.
Src
Addr. …
Payload

26. Standards Protocols are usually standardized.
☺ Why is the standardization essential?
Public agreement for the interoperability of data and technologies among devices manufactured by different companies
Types of standardization
De facto: by convention (fact)
Examples?
De jure: by regulation (law)
☺ Advantages of having standards?
Easy deployment of technologies
Less cost of devices …

27. Standard Organizations
Internet standards
ISOC (Internet Society)
IETF (Internet Engineering Task Force):
RFC (Request For Comment):
Committees
ISO (International Organization for Standards)
ITU-T (International Telecommunication Union – Telecommunication Standards): especially for telecommunications
ANSI (American National Standard Institute)
IEEE (Institute of Electrical and Electronics Engineers): especially for LAN
EIA (Electronic Industries Association)
Forums
ATM
WWW …