Transcript Core network components - Charles Sturt University

ITC242 – Introduction to
Data Communications
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Contact Details
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Dr Xiaodi Huang
Building 760 Room 105
Phone 02 60519 652
Email [email protected]
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:
1. Outline the basics components of a computer
network using both the OSI model and the
TCP/IP reference model;
2. Describe the nature of business information
requirements and the impact on data
communications;
3. Outline the modes of distributed data
processing;
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Aims and objectives of the subject
4. Enumerate the various transmission media
commonly used in carrier systems;
5. Recognize and discuss the basics of data
communications;
6. Enumerate the differences between wireless
telephone systems;
7. Describe how to identify a satellite system and
define its characteristics and use;
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Aims and objectives of the subject
8. Document the characteristics of local area
networks;
9. Identify the basics and compare and contrast
characteristics of WAN technologies;
10. Describe the operation and components of the
internet and internet based applications; and
11. 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
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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.
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Message
– The message is the information that needs to be communicated. It can be audio,
text, or visual information, or any combination of these.
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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.
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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.
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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.
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WAN switches
– WAN switches are used to logically connect routers on the WAN using virtual
circuits.
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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
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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 pixels=better quality=larger size
• More compression=reduced quality=increased
speed
– “Lossy” gives from 10:1 to 20:1 compression
– “Lossless” gives less than 5:1
• Format (vector vs bitmapped/raster) affects size
and therefore bandwidth requirements
• Choices in imaging technology, conversion, and
communication all affect end-user’s 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”?
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