Download Introduction - Department of Computer Science and Engineering

COMP 361, Fall 2000
Computer Communication Networks I
Dr. Mounir Hamdi
[email protected]
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How Important is COMP 361?
• Computer Networking is the backbone of the
information technology
• Information technology is having and will be
having a tremendous impact on our social lives,
the economy, and the way we work
• The knowledge of this class, COOMP 361, is a
key factor to be an active and productive
member of the information technology
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You Will Learn
• Networking Terminology
• Communication basics
– Media and signals
– Data transmission characteristics
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asynchronous and synchronous communication
serial and parallel transmission
bandwidth, throughput and noise
multiplexing
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You Will Learn [continued]
• Networking and Network Technologies
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Packet Switching, Circuit/virtual Switching
Protocols and Layering
Network Addressing
Interconnection (bridges, switches, routers)
Local Area Networks (star, ring, bus, mesh)
Routing
Flow, Error and Congestion Control
State-of-the-art in networks
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You Will Learn [continued]
• Applications and Network Services
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Network Programming
Client-server communications
Hierarchical naming (DNS)
File transfer (FTP)
Remote login (TELNET)
Email (SMTP, POP, IMAP)
Web technologies (HTTP, HTML, Java)
Network Security
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I’ll Do My Part
• Help you learn and enjoy the course
• Answer email promptly
• Be fair and impartial
• Encourage discussion and questions
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You Do Your Part
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Have the drive to learn and work hard
Be present and attentive
Don’t wait until the last minute
Contribute in discussions
Ask questions
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Grading
• Homework/Quiz
20%
– 2 homeworks and 2 quizes (best 3 out 4)
• Midterm Exam
25%
• Final Exam
30%
• Labs programming/project
25%
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Tentative Schedule - Lecture
• Week 1:
Introduction
• Week 2:
Physical Layer
• Week 3-4:
Data Link Layer
• Week 5-7:
Local Area Networks
• Midterm Exam
• Week 8-10:
Network Layer
• Week 11:
Transport Layer
• Week 12:
Application Layer
• Week 13-14:
State-of-the-art in Networking
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Tentative Schedule - Lab
• Week 1:
No lab
• Week 2:
General Introduction
• Week 3:
Introduction to Network Application
Programming Interface (API)
• Week 4:
Introduction to Socket Programming
• Week 5-6:
Example Application of Socket programming
• Week 7:
Advanced Concepts of Socket Programming
• Week 8-12:
More Advanced Concepts of Socket
Programming and the start of a more
advanced network programming project
• Week 13:
Presentation/Demonstration of Projects
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Lecture/Lab Time/Venue
• Lecture: T-Th: 9:00 - 10:20 LTE
• Labs:
1A - Wed: 9 - 9:50 Lab: 4214
1B - Wed: 10 - 10:50 Lab: 4214
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FAQ for this Class
• Grade depends on the rest of the class (there is a
curve)
• Late homework must be pre-approved
• No copying on homework/labs please
• Midterm/final sample exam will be available one week
prior
• Watch course home page for latest material and
announcement
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How to Contact Us
• Instructor: Mounir Hamdi
[email protected]
• Office Hours
– Mondays 10:00 - 12:00 p.m.
– Wednesdays: 11:00 - 12:00 p.m.
– ...and by appointment
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How to Contact Us
• Lab TA: Pun Kong Hong [email protected]
• Course TA: Zhang Lei [email protected]
• Office Hours
– To be given later
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Textbook
• Andrew Tanenbaum, “Computer Networks” Prentice
Hall, 1996, ISBN: 0-13-349945-6
• W. R. Stevens, UNIX Network Programming Vol. 1, 2nd
ed., Prentice-Hall, 1998.
• See course home page for other recommended texts
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Computer Networks - Peterson and Davie
Computer Networks and Internets - Comer
An Engineering Approach to Computer Networks - Keshav
TCP/IP Illustrated - Stevens
Interconnections - Perlman
Internetworking with TCP/IP - Comer
Data and Computer Communications - Stallings
Routing in the Internet - Huitema
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Who Am I?
• Associate Prof. Of Computer Science
and Co-Director of Computer Engineering
– Have been at HKUST since 1991
– Spent last year at Stanford University
• Current interests: High-Speed Switching
and Routing, Optical Networks, Network
Management, Quality-of-Nervice
Networking, Network Application (VoIP
and Video Conferencing)
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Who Are You?
• Computer Engineers/Scientist
– You’re very familiar with computers and the
Internet
– Very interested in networking
– Eager to learn new things
• What else?
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Introduction
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Communication Networks
• Problem: Given a set of devices that want to exchange
information. (Device = telephone, computer, terminals,
etc.)
• Simple Solution: Connect each pair of devices by a
dedicated point-to-point link
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Communication Networks
• The simple solution is sufficient if the number of
devices is small.
• With large number of devices it is not practical to
connect each pair of devices.
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Communication Networks
• A communication network provides a general solution
to the problem of connecting many devices:
– Connect each device to a network node
– Network nodes exchange information and carry the
information from a source device to a destination
device
– Note: Network nodes do not generate information
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Communication Networks
• A generic communication network:
Other names for Device: station, host, terminal
Other names for Node: switch, router, gateway
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HKUST Campus Network
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Classification of Communications
• Communication networks can be classified based on the
way in which the nodes exchange information:
• Communication Network
– Switched Communication Network
• Circuit-Switched Communication Network
• Packet-Switched Communication Network
– Datagram Network
– Virtual Circuit Network
– Broadcast Communication Network
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Broadcast Communication Networks
• Broadcast Communication Networks
do not have intermediate switching
nodes:
– Each station has a transmitter/receiver
that communicates over a medium shared
by other stations
– Transmission from any station is
received by all other stations
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Broadcast Network Examples
Packet Radio
Network
Satellite
Network
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Bus Local
Network
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Switched Communication Network
• A switched communication network consists of an
interconnected collection of nodes. Data are
transmitted from source to destination by being
routed through the nodes
• The switching method describes how data are
processed and routed in the network
• The basic switching methods are:
– Circuit Switching
– Packet Switching
• Datagram Packet Switching
• Virtual-Circuit Packet Switching
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Circuit Switching
• In a circuit-switched network, a dedicated
communication path is established between two
stations through the nodes of the network
• The dedicated path is called a circuit-switched
connection or circuit
• A circuit occupies a fixed capacity of each link for the
entire lifetime of the connection. Capacity unused by
the circuit cannot be used by other circuits
• Data is not delayed at the switches Circuit Switching
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Circuit Switching
• Circuit-switched communication involves three phases:
– 1. Circuit Establishment
– 2. Data Transfer
– 3. Circuit Termination
• Busy Signal if capacity for a circuit not available.
• Most important circuit-switching networks:
– Telephone networks
– ISDN (Integrated Services Digital Networks)
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Circuit Switching
• A node in a circuit-switching network:
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Circuit Switching
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Timing in Circuit Switching
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Packet Switching
• Data are sent as formatted bitsequences, so-called packets.
• Packets have the following structure:
Header and Trailer carry control information
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Packet Switching
• Each packet is passed through the
network from node to node along some
path (Routing)
• At each node the entire packet is
received, stored briefly, and then
forwarded to the next node (Store-andForward Networks)
• No capacity is allocated for packets
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Packet Switching
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Datagram Packet Switching
• Packets are called datagrams
• The network nodes process each packet
independently: If Host A sends two packets backto-back to Host B over a datagram packet network,
the network cannot tell that the packets belong
together. In fact, the two packets can take
different routes.
• Implications of processing packets
independently:
– A sequence of packets can be received in a different
order than it was sent
– Each packet header must contain the full address of the
destination
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Exercise: Datagram Packet
• Exercise: Most network applications (think of
email and file transfer) require that data is
received in sequence. For such applications a
datagram network appears to be inappropriate,
since packets may need to get reordered.
• Question: What are advantages of datagram
networks?
• The main example of a datagram packetswitching network is the Internet
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Datagram Packet Switching
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Timing of Datagram Packet Switching
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Virtual-Circuit Packet Switching
As the name suggests:
• Virtual-circuit packet switching is a hybrid of
circuit switching and packet switching
• All data is transmitted as packets
• All packets from one packet stream are sent
along a pre-established path (=virtual circuit)
• Guarantees in-sequence delivery of packets
• However: Packets from different virtual
circuits may be interleaved
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Virtual-Circuit Packet Switching
• Communication with virtual circuits (VC)
takes place in three phases:
– 1. VC Establishment
– 2. Data Transfer
– 3. VC Disconnect
• Note: Packet headers don't need to
contain the full destination address of
the packet
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Examples
• X.25
– X.25 networks have been around since the 1970s
– It is used in many public packet switching networks
• ATM (Asynchronous Transfer Mode)
– Developed in the 1980s
– For transmission of voice, video, and data in a single
network
• Others
– SNA (Systems Network Architecture) by IBM
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Virtual-Circuit Packet Switching
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Timing of Virt. Circ. Packet Switching
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Comparison
Circuit Switching
Datagram Packet Switching
VC Packet Switching
Dedicated transmission path
Continuous transmission
Path stays fixed for entire
connection
Call setup delay
Negligible transmission delay
No queueing delay
Busy signal overloaded
network
Fixed bandwidth for each
circuit
No overhead after call setup
No dedicated transmission
path
Transmission of packets
Route of each packet is
independent
No setup delay
Transmission delay for each
packet
Queueing delays at switches
Delays increase in overloaded
networks
Bandwidth is shared by all
packets
Overhead in each packet
No dedicated transmission
path
Transmission of packets
Path stays fixed for entire
connection
Call setup delay
Transmission delay for each
packet
Queueing delays at switches
Delays increase in overloaded
networks
Bandwidth is shared by all
packets
Overhead in each packet
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