Computer Networks

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Computer Networks

• Dr. Taek Mu Kwon
• Department of Electrical and Computer
• Engineering

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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.

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Computer Center Concept

• 60s to mid 80s
• 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.

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Distributed Computing Concept

• A large number of separate but interconnected
  autonomous computers do the job (computer
  network).

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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)

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Classification of Interconnections by Scale
0.1m Circuit Board Dataflow computer
1m System Multiprocessor
10m Room Local Area Network
100m Building Local Area Network
1Km Campus Local Area Network
10Km City Metropolitan Area Network
100Km Country Long haul network (Wide Area Network)
1000Km Continent Long haul network (Wide Area Network)
10,000Km Planet Long haul network (Wide Area Network)
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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,
   multi-processor 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.

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Communication Model
Source
Transmitter
Transmission System
Receiver
Destination
Input data
Transmitted signal
Received signal
Output data
Information
Output Informa- tion
Modem
Modem
PC
Server
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• 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.

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• 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.

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David Clarks Theory of Standards
Billion dollars of investments
Research
Standard
Activity
Time
Early proliferation of propriety networks GM net,
SABRE, SNA, DNA, ARPA net
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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.
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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.

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OSI Model
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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).
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Internet Standards
Internet Architecture Board (IAB) issues
standards by publishing a series of documents
called Request for Comments.
IAB
Internet Research Task Force (IRTF)
Internet Engineering Task Force (IETF)
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TCP/IP Protocol Suite
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TCP/IP Communication
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Internet
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IPv4 Address
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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