ITC242 Introduction to Data Communications

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ITC242 Introduction to Data Communications
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Contact Details

• Dr Xiaodi Huang
• Building 760 Room 105
• Phone [phone]
• Email xhuang_at_csu.edu.au
• Consultation Times
• Mondays 10am 1pm
• Thursdays 10am 1pm

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Housekeeping

• Assignments
• 1st Assignment Due 22st August
• 2nd Assignment Due 17th October
• Assessment
• 1st Assignment 20
• 2nd Assignment 20
• Exam 60
• In order to pass this subject you must achieve
  50 or greater in the exam, and 50 or greater as
  a combined assignment total.

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Housekeeping

• Textbook
• Stallings, W 2005, Business data communications,
  5th edn, Pearson Prentice Hall, Upper Saddle
  River, NJ.
• Web Resources
• http//csusap.csu.edu.au/xhuang/ITC242/
• Textbook Web Site
• http//WilliamStallings.com/BDC/BDC5e.html
• http//WilliamStallings.com/StudentSupport.html

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Aims and objectives of the subject

• Upon completion of this subject students should
  be able to
• Outline the basics components of a computer
  network using both the OSI model and the TCP/IP
  reference model
• Describe the nature of business information
  requirements and the impact on data
  communications
• Outline the modes of distributed data processing

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Aims and objectives of the subject

• Enumerate the various transmission media commonly
  used in carrier systems
• Recognize and discuss the basics of data
  communications
• Enumerate the differences between wireless
  telephone systems
• Describe how to identify a satellite system and
  define its characteristics and use

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Aims and objectives of the subject

• Document the characteristics of local area
  networks
• Identify the basics and compare and contrast
  characteristics of WAN technologies
• Describe the operation and components of the
  internet and internet based applications and
• Identify and describe the current data
  communication standards available.

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Topic 1

• Learning Objectives
• understand the business requirements for data
  communications and the broad factors influencing
  trends in data communications
• describe the nature of business information
  requirements and
• describe at a simple level, the different types
  of networks.

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Topic 1

• Activities
• Read all of Chapter 1 from the text.
• Attempt to answer Review questions 1.1, 1.2 and
  1.4 from the text.

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Communications Technology

• List the communications technology you have used
• This week ?
• What are the applications you have used on the
  Internet?

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Data Communication System
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Basic Components

• Medium
• The data communication medium is the physical
  path along which data travels to its destination.
  It can be a guided medium such as twisted-pair
  cable, coaxial cable, and fiber-optic cable. Or
  the medium can be unguided, for example laser,
  radio waves, and satellite microwaves.
• Message
• The message is the information that needs to be
  communicated. It can be audio, text, or visual
  information, or any combination of these.
• Protocol
• The protocol is a set of rules that provides
  agreement between communicating devices so that
  they can understand one another. As with grammar
  in human languages, having standard rules aids
  communication between participants who know them.
  
• Receiver
• The receiver can be any network device to which
  data is sent. For example, a receiver could be a
  computer, a telephone, a router, or a television.
  
• Sender
• The sender can be any network device that sends a
  data message. For example, a sender could be a
  computer, a telephone, or a router.

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Core network components

• A network consists of two or more computers
  connected together which share resources such as
  data, printers, and an Internet connection.The
  term "networking" refers to the sharing of
  resources on a network.

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• A network consists of the following three primary
  components.
• Server
• Workstation
• Host

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Server

• A server is a powerful computer that provides
  resources to other computers on the network.
  Servers are often dedicated, meaning that they
  perform no other tasks besides their server
  tasks.

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Workstation

• A workstation is any computer on a network that
  can request resources and is used to do work. A
  workstation may have multiple CPUs, making it
  faster and more capable than a personal
  computer.Workstations and clients are
  different. A client is any device on a network
  that can request resources.

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Host

• A host is any network device that has a
  Transmission Control Protocol/Internet Protocol
  (TCP/IP) address. Workstations and servers that
  have TCP/IP addresses can be considered hosts.
  Each host has a unique IP address.

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• Networks can consist of a small group of
  computers localized to a building or they can
  extend over large geographic areas, as follows.
• local area network (LAN)
• wide area network (WAN)

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local area network (LAN)

• A LAN is a network that is confined to a small
  geographic area for example, within a building.
  Each individual computer can access data and
  devices anywhere on the LAN.

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wide area network (WAN)

• A WAN is a computer network that spans a
  relatively wide area. A WAN consists of a system
  of interconnected LANs. The Internet is an
  example of a global WAN.

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WANs and LANs

• WANs differ from LANs in a number of ways
• they cover greater distances than LANs
• WAN speeds are slower
• LANs primarily use private network transports
  while WANs can use public or private network
  transports

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• WANs require several core devices to function.
• Routers
• Routers are used to direct traffic on a network
  to its correct destination. A router is connected
  to at least two networks, and it is located where
  the networks connect.
• WAN switches
• WAN switches are used to logically connect
  routers on the WAN using virtual circuits.
• Modems
• Modems provide remote access to networks by
  converting digital signals to analog ones so that
  the data can be transmitted over analog
  communication facilities such as telephone lines.
  

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Metropolitan area networks (MANs)

• A metropolitan area network, or MAN, is a network
  that covers a metropolitan area such as a city or
  suburban area. MANs are larger than LANs but
  smaller than WANs.
• A MAN is usually created when two or more LANs
  are connected together, offering high-speed
  connections.

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Intranets and extranets

• An intranet is a private network that exists
  within a business. It can consist of many
  interlinked LANs. Only people within the company
  or organization can access the intranet.The
  main purpose of an intranet is to share company
  information and resources between employees. An
  intranet looks like a private version of the
  Internet.

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• When part of a company's intranet becomes
  available to customers, suppliers, or anyone
  outside the company, the network is known as an
  extranet. Extranets use Internet Protocol (IP)
  and a public communication system to share part
  of an organization's information and resources
  with its customers, suppliers, or other
  businesses. A firewall is used to ensure security
  on the network.

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Chapter 2 Business Information

• Business Data Communications, 5e

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Analog Data

• An analog signal is an electromagnetic wave that
  varies in frequency over time to transmit
  information. It is usually represented in the
  form of a sine wave.
• Continuous signal
• Expressed as an oscillation (sine wave format) of
  frequency
• Information rate and channel capacity are
  measured in hertz (Hz) of bandwidth (1 Hz 1
  cycle per second).

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Basic Analog Terms

• Wave frequency Number of times a cycle occurs in
  given time period
• Wave amplitude Height of a wave cycle
• Hertz (Hz) The number of times a wave cycle
  occurs in one second (commonly used measure of
  frequency)

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Bandwidth

• Bandwidth is the amount of data that can be
  transmitted by a medium in a specified time. It
  is usually measured in bits per second (bps).
• The bandwidth is fixed when you use a narrowband
  transmission medium - copper wires - to transmit
  data.
• For a broadband medium such as coaxial cable, the
  bandwidth available can be allocated to different
  data transmissions. For example, if the total
  bandwidth of a broadband medium is 1000 bps, this
  could be divided between data, voice, video, and
  television transmissions, allocating 250 bps to
  each.

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Types of Information

• Audio
• Data
• Image
• Video

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Understanding Audio

• What makes sound? Vibration of air
• How can we record that vibration?
• How can we convert that to an electrical signal?

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Digital Audio

• For good representation, must sample amplitude at
  a rate of at least twice the maximum frequency
• Measured in samples per second, or smp/sec
• Telephone quality 8000smp/sec, each sample using
  8 bits
• 8 bits 8000smp/sec 64kbps to transmit
• CD audio quality 44000smp/sec, each sample using
  16 bits
• 16 bits 44000smp/sec 1.41mbps to transmit
  clearly

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Networking Implications for Voice Communication

• Requires powerful, flexible intralocation
  facility, and access to outside services (e.g.
  telcos)
• In-house alternatives
• PBX
• Centrex

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Digital Data

• Represented as a sequence of discrete symbols
  from a finite alphabet of text and/or digits
• Rate and capacity of a digital channel measured
  in bits per second (bps)
• Digital data is binary uses 1s and 0s to
  represent everything
• Data encoded in strings
• ASCII, IRA, UTF, etc
• Data is often redundant

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• The discrete nature of the digital signal and its
  binary format transmission means that digital
  signals are not as vulnerable to the
  interference, signal loss, and noise of analog
  signals. As long as the stream of bits gets to
  its destination, it can be reconstructed into a
  perfect replica of the original source.

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Data Networking Implications

• Vary significantly based on application and data
  types
• Response time often a key component

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Understanding Images

• Vector graphics
• Collection of straight and curved line segments
• Image described as collection of segments
• Raster graphics
• Two-dimensional array of spots (pixels)
• Also called bitmap image

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Networking Implications for Image Data

• More pixelsbetter qualitylarger size
• More compressionreduced qualityincreased speed
• Lossy gives from 101 to 201 compression
• Lossless gives less than 51
• Format (vector vs bitmapped/raster) affects size
  and therefore bandwidth requirements
• Choices in imaging technology, conversion, and
  communication all affect end-users satisfaction

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Video Communication

• Sequences of images over time
• Same concept as image, but with the dimension of
  time added
• Significantly higher bandwidth requirements in
  order to send images (frames) quickly enough
• Similarity of adjacent frames allows for high
  compression rates

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Response Time

• User response time
• System response time
• Network transfer time (throughput)

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Bandwidth Requirements

• Review Figure 2.7
• What happens when bandwidth is insufficient?
• How long does it take to become impatient?
• Is data communication ever fast enough?