This document provides an overview of computer networks and data communications. It discusses trends driving changes in network requirements, common network types including LANs and WANs, and technologies like circuit switching, packet switching, and frame relay. It also compares the OSI reference model to the TCP/IP model and summarizes key functions of each layer, including physical, data link, network, and transport layers.

1. NETWORK DESIGN
TIJ3053
Chapter 1 – Overview of Computer
Network

2. Data Communications, Data
Networks, and the Internet
 Thefundamental problem of
communication is that of reproducing at
one point either exactly or approximately a
message selected at another point - The
Mathematical Theory of Communication,
Claude Shannon

3. Contemporary Data Comms
 trends
 traffic growth at a high & steady rate
 development of new services
 advances in technology
 significant change in requirements
 emergence of high-speed LANs
 corporate WAN needs
 digital electronics

4. A Communications Model

5. Communications Tasks
Transmission system utilization Addressing
Interfacing Routing
Signal generation Recovery
Synchronization Message formatting
Exchange management Security
Error detection and correction Network management
Flow control

6. Data Communications Model

7. Transmission Medium
 selection is a basic choice
 internal use entirely up to business
 long-distance links made by carrier
 rapid technology advances change mix
 fiber optic
 wireless
 transmission costs still high
 hence interest in efficiency improvements

8. Networking
 growth of number & power of computers is
driving need for interconnection
 also seeing rapid integration of voice,
data, image & video technologies
 two broad categories of communications
networks:
 Local Area Network (LAN)
 Wide Area Network (WAN)

9. Wide Area Networks
 span a large geographical area
 cross public rights of way
 rely in part on common carrier circuits
 alternative technologies used include:
 circuit switching
 packet switching
 frame relay
 Asynchronous Transfer Mode (ATM)

10. Circuit Switching
 uses a dedicated communications path
established for duration of conversation
 comprising a sequence of physical links
 with a dedicated logical channel
 eg. telephone network

11. Packet Switching
 datasent out of sequence
 small chunks (packets) of data at a time
 packets passed from node to node
between source and destination
 used for terminal to computer and
computer to computer communications

12. Frame Relay
 packet switching systems have large
overheads to compensate for errors
 modern systems are more reliable
 errors can be caught in end system
 Frame Relay provides higher speeds
 with most error control overhead removed

13. Asynchronous Transfer Mode
 ATM
 evolution of frame relay
 fixed packet (called cell) length
 with little overhead for error control
 anything from 10Mbps to Gbps
 constant data rate using packet switching
technique with multiple virtual circuits

14. Local Area Networks
 smaller scope
 Building or small campus
 usually owned by same organization as
attached devices
 data rates much higher
 switched LANs, eg Ethernet
 wireless LANs

15. Metropolitan Area Networks
 MAN
 middle ground between LAN and WAN
 private or public network
 high speed
 large area

16. The Internet
 Internet evolved from ARPANET
 first operational packet network
 applied to tactical radio & satellite nets also
 had a need for interoperability
 led to standardized TCP/IP protocols

17. Internet Elements

18. Internet Architecture

19. Example Configuration

20. OSI Reference Model &
TCP/IP (Comparison)
 How many layers that OSI & TCP/IP
Model?
 What are differences between OSI &
TCP/IP Model?
 What are similarities among OSI & TCP/IP
Model?

21. Applications – The Interface Between
Human and Data Networks
 Most applications such as web browsers or e-mail clients, incorporate
functionality of the OSI layer 5, 6, and 7.
 Most TCP/IP applications layer protocols were developed before the
emergence of personal computer, GUIs and multimedia objects.
 A comparison of the OSI and TCP/IP model

22. Applications – The Interface Between Human
and Data Networks
 There are six steps OSI encapsulation process.
3. Software and hardware convert
comm to a digital format
2. The app layer prepares
human comm for
4. App layer services initiate the data
transmission over the data
transfer 6. The app layer
network
receives data from the
1. People create the network and prepares it
communication for human use.
5. Each layer
plays its role

23. Roles of Transport Layer
 Provide services to the adjacent layers
 Prepare application data for transport over network
 Process network data for use by applications

24. Transport Layer Functions
 Primary Functions:
1. Tracking individual
communication between
applications on sender and
receiver
2. Segmenting data and
managing each piece
3. Reassembling segments into
streams of application data
4. Identifying the different
applications
5. Performing flow control
between end users
6. Enabling error recovery
7. Initiating a session

25. OSI network layer
 OSImodel layer 3
 TCP/IP model Internet layer
Application HTTP, FTP,
Data stream TFTP, SMTP
Presentation etc
Application
Session
Transport Segment TCP, UDP Transport
Network Packet IP Internet
Data link Frame Ethernet,
Network Access
WAN
Physical Bits
technologies

26. Layer 3 protocol
A layer 3 protocol such as IP version 4 must:
 Provide an addressing scheme to identify
networks and individual hosts
 Encapsulate a segment from layer 4 into a
packet and include addresses
 Direct the packet across one or many
networks to the destination host
 Decapsulate (remove the packet header)
and give the segment to layer 4.

27. Data Link Layer – Accessing
the Media
 It provides a means for exchanging data over a common local media.
 Also links many upper layer services responsible for packaging the data
for communication between hosts.
 Data Link layer to prepare Network layer packets for transmission and to
control access to the physical media.

28. Physical Layer Protocols &

Servicesthe binary digits that
The role of the OSI Physical layer is to encode
represent Data Link layer frames into signals and to transmit and receive
these signals across the physical media - copper wires, optical fiber, and
wireless - that connect network devices.

29. Physical Layer Protocols &

Services
The delivery of frames across the local media requires the following Physical layer
elements:
 a. The physical media and associated connectors
 b. A representation of bits on the media
 c. Encoding of data and control information
 d. Transmitter and receiver circuitry on the network devices

30. Physical Layer Protocols &

Services
There are three basic forms of network media on which data is represented:
 - Copper cable
 - Fiber
 - Wireless
The representation of the bits - that is,
the type of signal - depends on the type
of media.
 Copper cable media, the signals are
patterns of electrical pulses.
 Fiber, the signals are patterns of
light.
 Wireless media, the signals are
patterns of radio transmissions..

31. The TCP/IP Concept
 Use existing network hardware
 Interconnect networks
 Add abstractions to hide heterogeneity

32. TCP/IP
TCP/IP is designed to use all types of
networks
 Connection-oriented
 Connectionless
 Local Area Network (LAN)
 Wide Area Network (WAN)
 Point-to-point link
 Set of bridged networks

33. Examples Of Packet
Switched Networks
 Wide Area Nets
 ARPANET, NSFNET, ANSNET
 Common carrier services
 Leased line services
 Point-to-point connections
 Local Area Nets
 Ethernet
 Wi-Fi

34. Summary
 introduced data communications needs
 communications model
 defined data communications
 overview of networks
 introduce Internet
 OSI Reference Model & TCP/IP