Objectives for this lecture

  • Understand the course structure
  • Be aware of the assessment methods
  • Be aware of the performance constraints to PASS this course
  • Be aware of the reading schedule and the consequences of falling behind
  • Be aware of your responsibilities in B227
  • Describe the simple components of a computer network
  • Define the difference between computer networks and distributed systems
  • Describe why computer networks are used both for business and personal use
  • Be able to generally discuss the social implications of the proliferation and widespread access and usage of computer networks.

B227 Administrative Bits

Unit Coordinator : Peter Cole

Location : ECL Building Room 2.058

Telephone : 9360 2918

Email :

Rockingham Campus Unit Coordinator : Danny Toohey

Rockingham Location : ACL 2/26

Rockingham Telephone : 9360 7026

Murdoch Location : ECL Building Room 4.028

Murdoch Telephone : 9360 2800

Email :

Prerequisites:B102 OR B105

Aims and Objectives:

On completion of this unit you will:

  • have gained an understanding of data communications - the hardware, software and communications services available to support distributed access to computing facilities;
  • understand the requirements for data communications - the need to provide services enabling businesses to utilise information;
  • understand the crucial importance of the role and nature of standards in the field of data communications
  • understand the manner in which data communications technology can be applied to satisfy business needs and processes;
  • demonstrate proficiency and confidence in the use of data communications hardware and software;
  • understand the implications of data communications in application systems design and management both at program level and at the architectural level.

Internal

The formal class contact is 5 hours per week, consisting of 1 three hour lecture and one 2 hour tutorial session. The first hour of the tutorial is supervised.

Lecture time:Tuesday 9.30am - 12.20amECL4

Tutorial times:Tutorials will begin in week 2. Attached to the rear of this study guide is a tutorial preference sheet. Please print your name and student number. Please fill in your first five (5) preferences and return it to the lecturer at the end of the lecture. The final tutorial allocations will be printed and posted on the notice board in the IT corridor and will also be posted on the B227 FTP site

ftp.it.murdoch.edu.au/pub/units/b227/tut_allocations .

If you are restricted to a specific tutorial (s) due to childcare, work commitments etc please fill in the reason in the Restricted Selection section on the bottom of the form then sign and date it..

Course Materials

Textbook:The following text are required for the unit:

Forouzan B. A. Data Communications and Networking , 2nd Ed, McGraw-Hill, 2001.

NB Much of the reading is complex. This is not a mathematics or engineering unit. Therefore, when you read the text and the supplied material you need to understand the material and not necessarily commit it all to memory. Use the topic objectives to focus your attention on that material which may be used for assessment.

Lecture notes will be available on the student network and the web

Reading Schedule Weeks 1-5

Below is the reading schedule for the first part of the unit. The amount of reading is quite large and I am taking this opportunity to give some advice how to handle the materials covered.

At this stage of the semester you have to quickly grasp a general understanding of the concepts and methods involved in data communications. When you are reading the text do not attempt to memorise the content, there is too much to remember. Try to understand the fundamentals described in the material.

You will be pleased to hear that the next group of reading will be much lighter than this.

Topic / Weeks / Topic Content / Reading
1 / 1 / Intro to Networks: hardware, software, OSI & TCP/IP reference models, Layers / Forouzan Ch. 1,2,3
Ch 24.1
2 / 2, / The Physical Layer: Data comm. Theory, Transmission Media, transmission providers, ISDN, ATM, bandwidth / Forouzan Ch. 4,5,7
3 / 3 / Data link Layer: design issues, error detection, data link protocols / Forouzan Ch. 9,10,11
4 / 4 / Medium Access Sub-layer: MA protocols Ethernet, CSMA/CD, / Forouzan Ch. 12
5 / 5 / The network layer: design issues, routing Algs. Congestion issues, internetworking, the IP protocol ATM network layer / Forouzan Ch. 21,
Ch 24.2-5 inc

Important

The theoretical component of the unit is divided into a number of topics, listed in the unit outline and required readings table above.. A good way to approach each topic is to read the material listed for each topic. Summarise the material in your own words, and make notes about the key points. Then complete the Practice set (review and multiple-choice questions and the exercises) at the end of each chapter.
Some of these questions will be part of the assignments and final exam questions therefore you are strongly advised to do each practice set after reading each chapter.

Types of Assessment

This unit will be assessed by assignments, quizzes and a final examination with the following weights:

Quizzes (3 * 5%)15%

Assignments (2 * 10%)20%

Project10%

Final Examination55%

In order to pass this unit, you must submit all the assignments and achieve satisfactory performance (at least 50%) in each section of the unit shown above.

Quizzes

Three quizzes will be held in weeks 4, 8 and 12 in the Tuesday lecture period.

Assignment Due Dates:

Assignment / Due Date / Time
1 / Friday of Week 5 : 23rd March 2001 / 5.00 PM
2 / Friday of Week 9 : 27th April 2001 / 5.00 PM
Group Project / Friday of Week 12 : 25th May 2000 / 5.00 PM

Assignments 1&2 are individual assignments where assignment 3 is a group project.

NOTES ON GROUP PROJECT

The Project is a LAN design exercise. It is intended that internal students should complete the project as a group project. Working as a group allows you to pool your ideas and be able to share the workload in an effective manner. Working as part of a team is also an important part of your preparation for becoming an IT professional.

However, the process of group work itself is not a major stated objective for this unit. Therefore, if you have a good reason for not being able to do the group assignment, you may do the individual assignment – please see the unit coordinator (Peter Cole) as soon as possible (and by 27 April by latest) to confirm this.

  • You can work in groups of 2 or 3 (that means not 4 or more). Groups of three are preferred. You are responsible for finding your own groups. Members of a group can belong to different tutorials, or have different tutors. All groups should notify me in writing (with signatures) of their membership by 27 April.

A note on cheating

Cheating, including plagiarism, unauthorised collaboration, examination misconduct and theft of other students work, is regarded very seriously by the University and if detected can result in a requirement to complete additional work, failure in a course, suspension, or in severe cases expulsion from the University.

If you are not sure about the difference between “working together” and cheating. There is a good description in the Unit outline.

What are we studying?

Data communication networks between computers

This normally entails :

  • two or more computers connected together somehow
  • some means of transmission medium
  • wire - optical fiber - radio waves etc.
  • serial streams of data (bits)
  • some means of error detection - why?
  • loss of signal integrity due to type of transmission mediums’ physical properties
  • Agreed communication standards (protocols)

Tanenbaum’s distinction

Computer Network

vs

Distributed System

Computer network :

  • the interconnection of autonomous computers
  • autonomous computer:
  • a computer which is not controlled by another computer (not a slave)

Distributed System :

  • the invisible (transparent) interconnection of autonomous computers
  • normally operating systems ie. software based
  • multi-processors (perceived)

“explicit nature of a computer network”

  • log on - log off
  • file transfer (FTP)

Who uses networks?

Business & Government :

  • fast
  • reliable (hopefully)
  • cheap (comparative message costs)
  • better communications - group support systems (GSS)
  • better utilisation of and access to resources
  • client-server model

People :

  • Personal communication
  • education ( information gathering)
  • entertainment, interactive or otherwise

Social implications of popular use of networks

  • changed perception toward way of life
  • READ “Computers as Tools and Social Systems: The Car Computer Analogy” in Kling R., Computerization and Controversy, 2nd Ed., Academic Press, 1996.

Your objectives

to be able to :

  • describe the basic hardware requirements of a -
  • LAN
  • MAN
  • WAN
  • internetwork

Describe the job of the components:

  • bridge
  • router
  • gateway

define and expound on :

  • point-to-point
  • broadcast
  • connection topologies
  • network classification

Hardware basics

In the last lecture we pointed out that computer networks rely on a combination of hardware and software used in combination to afford reliable and effective data communications.

In this lecture we look at the basic classification and topology of computer networks.

Transmission Technologies

Broadcast & Point-to-point networks

In Broadcast networks individual computers share a single communication channel.

Point-to-point networks have many connections between individual pairs of computers or routers.

Broadcast networks:

  • Packets of data
  • contains an address field Broadcast all 1’s
  • everyone hears or sees them
  • if it is of importance for them they act on it else ignore
  • if all machines are addressed - Broadcasting
  • if subset of machines - Multi-casting
  • normal for small area nets - LANs

PP:

  • Packets of data
  • contains an address field
  • routers see the packet
  • will direct the packet to which ever machine it is addressed too
  • larger areas - MANs & WANs

Network classification

LANs

Normally:

  • privately owned
  • contained in buildings or small areas (Campus)
  • Tanenbaum’s 3 characteristics of a LAN
  • size
  • bounded
  • worst case Transmission scenario known
  • simpler network management
  • transmission technology
  • single cable
  • 10Mbps - 100Mbps - 1Gbps
  • low error

topologies

  • Commonly the Bus topology run Ethernet (IEEE 802.3)
  • decentralised control mechanism
  • random repeat after collision
  • ends of bus terminated with a resistor
  • 10Base2 uses a 50 ohm resistor
  • sensitive to poor connections > resistance
  • Ring topology most well known IBM Token ring
  • packet propagates around the ring (bit by bit)
  • requires some mechanism to control WHO broadcast
  • static allocation - set time slot - round robin - wastes bandwidth
  • dynamic allocation - either central or decentralised control - more efficient use of transmission medium
  • requires arbitration or priority type algorithms to control
  • Token passed - only token holder can broadcast

STAR Topology

  • Our labs has a 100Mbps 100BaseT star
  • Still broadcast
  • we can still consider this as a virtual bus
  • Hubs can be cascaded

  • The distance between a hub and a machine about 100m maximum
  • Easier fault finding and rectification
  • becoming more popular than coax bus tecnologies
  • more on this subject this later on

MANs

Metropolitan Area Networks

  • Similar technology to a LAN but over a city area
  • both data and voice (telephone technology)
  • no switching elements (PP HAS)
  • new standard Distributed Queue Dual Bus (DQDB)

  • Head ends maintains the direction of the unidirectional lines

WANs

  • Large geographic area (Australia)
  • applications run on hosts (LAN)
  • Subnet connects hosts
  • requires routers on the subnet as subnet is PP
  • data switching - nodes, exchanges
  • often referred to as a packet-switching network (store-and-forward)
  • packet arrives
  • stored until the route is clear
  • forwarded toward destination hosts
  • PP across subnet then broadcast on hosts LAN

  • WANS often irregular topologies - cities not laid regularly - may have wireless transmission - ground to satellite links

Wireless Networks

  • useful for connecting mobile units back to hard LANs or WANs
  • Marconi - Morse Code - 1901
  • taxis
  • Useful - has yet to reach full potential
  • Laptops with built in telephone technology (digital)
  • Laptops with IEE 802.11b Wireless Ethernet

Internetworks

  • just a inter-connection of networks
  • not always compatible
  • need gateways to translate between the differing types of networks (protocols)
  • not the same as The Internet