IB Computer Science Topic.3 - Weebly€¦ · 2010-03-01 · IB Computer Science Topic 3 - Overview...

IB Computer ScienceTopic.3:

Designed by: Professor. A. Lawson

Sources: Online Materials, thanks for all

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IB Computer ScienceTopic 3 - Overview

Network fundamentals 3.1.1 Identify different types of networks 3.1.2 Outline the importance of standards in the construction of networks 3.1.3 Describe how communication over networks is broken down into different layers 3.1.4 Identify the technologies required to provide a VPN 3.1.5 Evaluate the use of a VPN Data transmission 3.1.6 Define the terms: protocol, data packet 3.1.7 Explain why protocols are necessary 3.1.8 Explain why the speed of data transmission across a network can vary3.1.9 Explain why compression of data is often necessary when transmitting across a network 3.1.10 Outline the characteristics of different transmission media 3.1.11 Explain how data is transmitted by packet switching Wireless networking 3.1.12 Outline the advantages and disadvantages of wireless networks 3.1.13 Describe the hardware and software components of a wireless network 3.1.14 Describe the characteristics of wireless networks 3.1.15 Describe the different methods of network security 3.1.16 Evaluate the advantages and disadvantages of each method of network security

IB Computer ScienceTopic 3.1.1

Identify different types of networks

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Topology = physical layout of a networkBasic Topologies

STAR RING BUS

These are called NODES

Types of Networks:

• LAN • WAN • GAN • (W)PAN • WLAN • SAN • VPN • VLAN •

Internet/Extranet/Intranet

LAN• Local Area Network • A network in which the nodes are close together. For example, in the same building, on the same site (school). – Small geographic area – Tend to use private connections as opposed to leased communication lines. 3

WAN• Wide Area Network • A network in which the nodes are spread out over a larger geographic area. For example, national and international retailers are connected. – Large geographic area – Uses leased communication lines.


GAN• Global Area Network • A network where the nodes are spread out globally. For example, the internet.

Computing Sin

The Internet != World Wide WebTypes of Network • LAN • WAN • GAN • (W)PAN • P2P • WLAN • SAN • VPN • VLAN •Internet/Extranet/Intranet

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(W)PAN• (Wireless) Personal Area Network • A network which consists of computers, mobile phones, iPod, headphones etc.


Bluetooth typically travels 10m in any direction.

P2P• Peer-to-Peer • P2P networking is a distributed architecture that partitions tasks or work loads between peers. Peers are equally privileged, equipotent (of the same power) participants in the application. • They are said to form a peer-to-peer network of nodes

WLAN• Wireless Local Area Network • A network in which the nodes are close together. For example, in the same building, on the same site (school)… BUT WITH NO WIRES!

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SAN• Storage Area Network • A network which provides dedicated access to storage. Typically, they have their own storage devices not accessible through the wider network; instead the SAN appears as a device to the OS.

Internet• The internet is a network of networks. • Since 2013, spans beyond our solar system. • Only 4% of WWW content is visible.

Internet VS Extranet

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VLAN• Virtual Local Area Network (This one is a logical concept not physical!)

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Outline the importance of standards in the construction of networks

Standards are important!

• Standards play an important role in networking. • Without standards, manufacturers of networking products have no common ground on which to build their systems. • Interconnecting products from various vendors would be difficult, if not impossible. • Without agreed standards, communication would be difficult (if not impossible)


Describe how communication over networks is broken down into different layers

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Simplified Model (Sending data)


Identify the technologiesrequired to

provide a VPN

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VPNA secure network that uses primarily public, telecommunication infrastructures, such as the Internet, to extend a private network.

Two types Client - Server

VPN-C VPN-STends to be

software installed upon the client’s

computer

The server that provides “the

service”. Normally located in the

office or wherever the client connects

too.

Basic checklist for VPNALAN that is connected to the internet. One computer outside of the LAN that is also connected to the internet. VPN client and server running on the lone machine and the original LAN Internet connection

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Evaluate the use of a VPN

Summary• Through a VPN, it is possible to connect to a LAN that is protected from outside access through the internet. • Therefore, it is possible for workers to connect to a company's internal network from almost anywhere in the world. • This gave rise to home offices, as many office jobs do not require consultation and hence can be completed from home. • This remote working is also called telecommuting.

A perspective on telecommuting

https://www.youtube.com/watch?v=R2whPdnCGrM

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Define the terms: protocol & data packet

data packetDefinition: Protocol

Set of rules for data communication

OR

A protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.

Definition: Data Packet

Data - Anything in a form suitable for use with acomputer… such as binary. Typically data is meaningless.

Packet - A small unit of data used in network communication.

Make up of a data packet

Packet Switching

https://www.youtube.com/watch?v=ewrBalT_eBM&feature=iv&src_vid=WwyJGzZmBe8&annot

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Explain why protocols are necessary

Summary• Protocols are the set of rules computers follow when communicating across a network. • Without them, no information can be transmitted as computers don't know how to interpret the signals coming through the network.

Establishment

• Ensure data integrity • Manage flow control • Prevent deadlock • Manage congestion • Perform error checking

Language / Format

Essential functions of protocols

Data integrity

Flow Control

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Congestion Control

Error Checking

Error Handling

Termination


Explain why the speed of data transmission across a network can vary

Connection speed averages

• Dedicated LAN connections – UTP Copper cable (100Mbps) – Fibre optic cable (5-100Gbps) – WiFi (10-150Mbps)

• Broadband (WAN) connections – DSL (2-16Mbps) – Fibre optic (20-100Mbps) – 3G (± 1 Mbps) – 4G (± 20 Mbps)

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Speeds vary (provider)

Speeds vary (time of day)

Speeds vary (distance)

Speeds vary (cable quality)

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Explain why compression of data is often necessary when transmitting across a network

Definition: Compression

Data compression involves encoding information using fewer bits than the original representation.

That’s why we bother…

Media file transfer over the web

File TransferEncryption/Protection

Backups/Archiving

Lossy vs Lossless Compression

Common compression file types

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Audio Example: WAV vs MP3 ImagesLow res images become pixelated

when zoomed in


Outline the characteristics of different transmission media

Characteristics of media

Types of media

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UTP – Unshielded Twisted Pair

Co-axial (metal)

Ties in with:

Fibre-optic (glass)


Explain how data is transmitted by

packet switching

Definitions

• Packet: A packet is the unit of data that is routed between an origin and a destination on the Internet or any other packet-switched network.

• Packet switching: Packet-switching describes the type of network in which relatively small units of data called packets are routed through a network based on the destination address contained within each packet.

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How it works Video: Packet

Switching

Video: Undersea

Cables


Outline the advantages and disadvantages of wireless networks

• Uses unlicensed radio spectrum – Doesn't cost anything • LANs can be set up without cabling – Doesn't take space or time to lay the cables. No extra cost on cables • WiFi can support roaming between access points – People can switch from router to router automatically depending in which connection is best • Global standards (eg. 802.11n) • Prices are cheap – Many types are available on the market and they are affordable

Advantages

• Interference – as the 2.4GHz spectrum is often crowded with other devices • Limited Range • WEP – this encryption is not difficult to hack and WPA2 has solved this problem • Access Points – these can be used to steal data • Health Concerns

Disadvantages

https://www.youtube.com/watch?v=ewrBalT_eBM&feature=iv&src_vid=WwyJGzZmBe8&annotation_id=annotation_667002

https://www.youtube.com/watch?v=IlAJJI-qG2k

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In an exam be prepared to EVALUATE

• What’s good about it? • What’s bad about it? • When is it most appropriate?


Describe the hardware and software components of a wireless network

Hardware components

• Node: PC, Laptop, Tablet, Printer • Wireless network interface card • Radio waves (Bluetooth/WiFi) • Connection point: Wireless AP / Router

Software components

• Network Operating System (with drivers) • Protocol stack (TCP/IP) • Applications (Browser/File explorer)


Describe the characteristics of wireless networks

Types of wireless networks

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• Also called Wireless LAN (WLAN) • Used in laptops/mobile devices to connect wirelessly to home network • Most preferred network type to implement a home network • Allows relatively slow to fast data transmissions (depending on the version) • Backwards compatible with most older WiFi standards (a/b/g/n) • Small transmitting radius makes it suited for homes, usually <20m

WiFi (Wireless Fidelity)

WiMAX

• WiMAX = Worldwide Interoperability for Microwave Access • Designed for large distance high speed internet access • Relatively cheap method of providing internet over a large area - suited for poorer countries • Rivalled by Long Term Evolution (LTE) standard • Can be used as a form of wireless variant of DSL phone transmission lines

3G (Third Generation)

• The primary way mobile phones access the internet today • Allows the tunnelling of phone lines (mobiles don't have to switch back to phone network when receiving a call • Relatively fast

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Describe the different methods of network security

Making sure systems don’t get hacked? Security breaches can happen without being hacked…Making sure data is not stolen or leaked? But what about systems where data is public?

Its much easier to think of these three factors when talking about security.

1. Confidentiality 2. Integrity

• Maintaining accuracy of data 3. Availability • DoS attacks

Security properties

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Why is securing systems so hard?

• Cannot plan for every eventuality • The “arms race” • Systems can unravel from a weak point • Users!

Is someone who they claim to be?• One factor authentication • Two factor authentication • Three factor authentication

Something you know.

One factor

• Hardware or Software (or hybrid of both). • Controls incoming and outgoing network traffic. • Analyse data packets based on pre-determined set of rules.

Authentication

Something you have.

Two factor

Something you are.

Three factor

• Media Access Control address. • Hard-coded into devices by manufacturers • Managed by the IEEE (institute of Electrical and Electronics Engineers).• Are used to identify specific pieces of hardware.

MAC Address

• Locked doors? • Security personnel? • Cages / sealed units? • Reinforced/secure rooms? • Walls with barbed wire? • Ravenous guard dogs?

People? Natural Disasters?

Firewalls

Physical security

Only focusing on encryption over wireless networks

• UserID (and passwords) • PSK (pre-shared key) • WEP (dead) • WPA / WPA2

Encryption

Wireless Equivalent PrivacyVery simple algorithm… …

that was very quickly broken!

• Superseded by WPA in 2003 • Deprecated in 2004.

WEP• Wi-Fi Protected Access (I or II)

WPA/WPA2

WPA WPA2

2004-2006 2006 onwards

Intrusion can be made from outside the network.

Intrusion can only come from since who already has access to the network.

• Advantages: – Access rights to the network can be set for each user – User groups can be created to manage user rights in batches • Disadvantages: – A userID can be stolen – system can be bypassed – Does not protect against intercepting messages in the network

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Evaluate the advantagesand disadvantages of each method of network security

UserID

• Advantages: – A strong encryption is very hard to break – Computer are fast enough to encrypt data on-the-fly • Disadvantages: – Often, users are lazy and take a password that is easy to guess – The password needs to be transmitted over the network to receiver to allow them to read the message – Some encryptions are designed to have backdoors built in

Encryption security

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IB Computer Science Topic.3 - Weebly€¦ · 2010-03-01 · IB Computer Science Topic 3 - Overview...

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