Transcript Computer Networks

Computer Networks
Dr. Taek Mu Kwon
Department of Electrical and Computer
Engineering
ECE 4321 Computer Networks
• ECE Technical Elective Course
• 3 Credits
• Network Lab (MWAH 60)
• Network Programming Project (3 – 4)
• Written Exams
• Course Objective: On completion of this course students are
expected to learn and understand characteristics of network
transmission media, OSI model, TCP/IP, data link protocols,
routing algorithms, various LAN technologies, WAN
technologies, and network programming.
Computer Center Concept
60’s to mid 80’s
 A powerful single computer is doing all the
work.
 Users bring work to the computer instead of
bringing the computer to the user.
 Expensive hardware cost.

Distributed Computing Concept

A large number of separate but
interconnected autonomous computers do
the job (computer network).
Advantages of Distributed
Computing

Resource sharing
 Higher reliability
 Better price/performance ratio
 Better communication medium
 Special server computers for efficient
computing (video server, database server)
Classification of Interconnections by Scale
0.1m
Circuit Board
Dataflow computer
1m
System
Multiprocessor
10m
Room
100m
Building
1Km
Campus
10Km
City
Metropolitan Area Network
100Km
Country
1000Km
Continent
Long haul network (Wide
Area Network)
10,000Km Planet
Local Area Network
Integrated Service Revolution (1990 - )
1) The fundamental difference between data processing
(computer) and data communication (transmission and
switching equipment) have blurred. Ex) Half of OS is
concerned with computer networks.
2) The fundamental difference among data, voice, and
video communication have blurred.
3) The line between single-processor computer, multiprocessor computer, local network, metropolitan
network, and long-haul network have blurred.
4) WWW became an integration point of all types of
communications: data, voice, video.
Communication Model
Source
Information
Transmitter
Input
data
Transmission
System
Transmitted
signal
Receiver
Received
signal
Destination
Output
data
Output
Information
Modem
Modem
PC
Server

Interface: electrical and procedural connection between each stage
from the source to destination

Synchronization: receiver must know a signal when it begins to
arrive, when it ends, and the duration of each signal elements.

Exchange Management: For a two party telephone
conversation, one party must dial the number of the other. The called
party must then lift the receiver and confirm the connection of the
intended party.

Error Detection and Correction: ACK, NACK, Telephone–
ask repeat

Flow Control: the source should not send data faster than the
receiver can process or absorb.

Addressing and Routing

Recovery: File transfer can be interrupted due to a system fault. The
objective of recovery is to restore the activity at the point of
interruption.

Message Formatting: An agreement between two parties as to
the form of the data to be exchanged.

Security: Sender wishes to be assured that only intended parties
receive the data or message.

Network Management: To monitor the status or configure the
system.
David Clark’s Theory of Standards
Billion dollars
of investments
Research
Activity
Standard
Time
Early proliferation of propriety networks
GM net, SABRE, SNA, DNA, ARPA net
Open System Interconnection (OSI)
reference model
This model is based on a proposal developed by
the International Standards Organization (ISO)
as a first step towards international
standardization of various protocols. The
reference model was adopted in 1984 as ISO
7498. It is not an actual working model, but
serves as a standard model for classifying
communication functions.
International Standards Organization
It is a voluntary and non-treaty international
organization found in 1946. Its members include
national standard organizations of 89 member
countries. Examples include ANSI (US), BSI
(Great Britain), AFNOR (France), DIN
(Germany), … It issues standards on a vast
number of subjects from nuts and volts to
telecommunication standards.
OSI Model
TCP/IP Protocol Architecture
TCP/IP architecture is a result of research and development
conducted on the experimental packet-switched network,
funded by the Defense Advanced Research Project Agency
(DARPA). This protocol suite consists of a large collection of
protocols that have been issued as Internet standards by the
Internet Architecture Board (IAB).
Internet Standards
Internet Architecture Board (IAB) issues standards by
publishing a series of documents called Request for
Comments.
IAB
Internet Engineering
Task Force (IETF)
Internet Research
Task Force (IRTF)
TCP/IP Protocol Suite
TCP/IP Communication
Internet
IPv4 Address
IPv6
128 bit address: Allow 6x1023 unique
addresses per square meter of surface of the
earth.
 Address Auto-configuration
 Improved Option Mechanism
 Support Different Types of Traffic Flow
