COMP 361, Fall 2000

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COMP 361, Fall 2000

• Computer Communication Networks I
• Dr. Mounir Hamdi
• hamdi_at_cs.ust.hk

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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
• 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
• 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
• 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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Ill 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

• Have the drive to learn and work hard
• Be present and attentive
• Dont 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 900 - 1020 LTE
• Labs 1A - Wed 9 - 950 Lab 4214 1B - Wed
  10 - 1050 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 hamdi_at_cs.ust.hk
• Office Hours
• Mondays 1000 - 1200 p.m.
• Wednesdays 1100 - 1200 p.m.
• ...and by appointment

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How to Contact Us

• Lab TA Pun Kong Hong - konghong_at_cs.ust.hk
• Course TA Zhang Lei - zhanglei_at_cs.ust.hk
• 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
• 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
• Youre 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
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 bit-sequences,
  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-and-Forward 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
  back-to-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 packet-switching
  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