Systems Development – System Design

 Systems Development – System Design
 

Learning Outcomes:

• Describe the functions of each part of a computer-based system and the related issues.
• This covers the hardware platform, software, inputs, outputs, user interfaces, database structures, data processing, data control, data security and system security.
• Design and appraise an effective interface between the user and the system.
• Different types of human-machine interfaces are compared.
• Know system flowcharts, structure charts, data flow diagrams and data dictionaries to design and document a proposed system.
• Use Gantt Charts for project management.

 

User interfaces

 

• Graphical user interface (GUI)
• Advantages: easy to use, customized interface possible
• Input methods: keyboard, mouse, touch screen
• Screen components: mouse pointer/cursor, icon, menu, button, graphics
• Users: novice

•  Command line interface (CLI)
• Advantages: faster than GUI, keyboard only, in plain text and file format
• Users: experienced user

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  2017 1d.

AL CS2(2003-2012): 2006 10b. 2009 9ac. 2011 10b.

 

System flowcharts

Symbols to be memorized:

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  -

AL CS2(2003-2012): 2008 9e. 2009 9e. 2010 8e. 2012 8f.

 

Structure charts

It gives an overview of the system with its modules and their interaction.

Control information: e.g. Boolean data indicating the validity of the input data

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  SP 4c. 2012 2b.

AL CS2(2003-2012): 2006 3a.

 

Data flow diagrams

 

The purpose of data flow diagram is to map out the data flow of the system.

Tips: classify the given information into data, entity, process and database.

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  2013 3c. 2015 4a.

AL CS2(2003-2012): 2004 13c. 2005 13e. 2007 8ab. 2008 9d. 2009 9d. 2010 8ab. 2011 10a. 2012 8c.

 

Gantt Charts

Arrows: to show the dependent relationship i.e. Task 3 depends on the results of Task 1 and Task 2

Critical path: the minimum time to complete the project. In this case: Task 1 à Task 3.

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  PP 2ci. 2013 3a. 2015 2a. 2017 1a.

AL CS2(2003-2012): -

Learn more (Critical path): AL CS2: 2003 3. 2004 3a. 2005 4. 2006 13a. 2007 2. 2009 1. 2012 3.

  

References:

https://www.geeksforgeeks.org/difference-between-cli-and-gui/

https://www.smartdraw.com/flowchart/flowchart-symbols.htm

https://www.geeksforgeeks.org/software-engineering-structure-charts/

https://www.smartsheet.com/content/gantt-chart-critical-path

 Systems Development -  System Analysis

 

Learning Outcomes:

• Identify the major task involved in solving a problem.
• List some common methods and activities to gather information for analyzing problems and documenting users’ requirements.
• The common methods and activities are interviews, surveys, questionnaires, observations and document review.
• Know the need for a feasibility study for a proposed solution.
• Examine the pros and cons of alternative proposals.
• Write requirement specifications.

 

Methods to collect user requirements

• Interviews
• Questionnaires
• Observations

 

Feasibility Study

• To find out if the proposed solution should be undertaken or not by analyzing various factors such as practicability, cost etc.

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  2012 3d. 2015 2bi.

AL CS2(2003-2012): 2008 9abc. 2011 3a.

 

References:

https://www.tutorialspoint.com/software_engineering/software_requirements.htm

 Systems Development – Basic concepts

 

Learning Outcomes:

• Describe the phases involved in systems development using the Waterfall Model.
• By using suitable case studies, students should experience the processes and activities involved in various phases of systems development.
• Explore the limitations and shortcomings of the Waterfall Model.
• Recognise the benefits and limitations of other approaches.
• Other approaches include Prototyping and Rapid Application Development (RAD).

 

Waterfall Model

 

Steps:

1. System requirement Analysis: Compile user requirements. Document: Requirement documentation.
2. System Design: Establish software and hardware requirements.
3. Implementation: implement the design. Program coding is written.
4. Testing and Integration: Look for any errors in the coding. All units are integrated.
5. Deployment: Deployed to users.
6. Maintenance: Further updates if issues arise.

Each phase is completed before going to the next one.

Documentation is integrated into all the phases.

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  SP 4a. 2013 3b. 2016 1ai-iii.

AL CS2(2003-2012): 2007 1a. 2008 3. 2010 3a,bii,c. 2012 2, 8a.

Learn more: AL CS2 2004 13ab.

  

Limitations and shortcomings of the Waterfall Model

 

The model goes forward only and does not support going backward for revision or improvement.

Requirements defined in the initial phases. Cannot accommodate requirement changes.

Development time is usually longer than other approaches. (no overlapping of different phases)

 

Prototyping

 

After knowing the basic requirement, a prototype of the system is built. Users can try the system and provide feedback to refine the system requirements.

 

Rapid Application Development (RAD)

 

Uses prototyping approach.

Aim at quick development while reducing cost and maintaining quality.

 

Drawback:

• require active user involvement
• RAD not applicable if the system cannot be modularized
• need highly skilled developers for modelling

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  SP 4b. 2014 1aiv. 2016 1aiv.

AL CS2(2003-2012): 2007 1b. 2010 8f. 2012 8b.

 

References:

https://www.tutorialspoint.com/sdlc/sdlc_waterfall_model.htm

http://tryqa.com/what-is-prototype-model-advantages-disadvantages-and-when-to-use-it/

http://cisaexamstudy.com/prototype-rapid-application-development-rad-point-remember/

https://marutitech.com/rapid-application-development/#Disadvantages_Of_Rapid_Application_Development

 

Elective B - Compulsory topics that appear in the elective part

 Elective B - Compulsory topics that appear in the elective part

 

Transfer speed calculation

 

MB/s ≠ Mbps

 

• Mbps = megabits per second
• MB/s = megabytes per second

• 1 GB = 1024 MB
• 1 MB = 1024 KB
• 1 KB = 1024 B
• 1 B = 8 bits ***

 

You are usually provided with

• Data size e.g. 20 MB
• Transfer speed e.g. 10 Mbps

Calculate the transfer time

 

Steps:

1. Convert the data size to bits.
   20 MB = 20 x 1024 KB = 20 x 1024 x 1024 B = 20 x 1024 x 1024 x 8 bits
   
   
2. Convert the transfer speed to bits.
   Actually it is already in bits! Mega- here stands for 1000000. i.e. 10 Mb = 10 x 1000000 bits
   
   
3. Data size/transfer speed is the answer.
   20 x 1024 x 1024 x 8 / (10 x 1000000) = 16.78 seconds.

 

Other calculations: 

• Calculate data size from transfer time and speed. 
• Calculate the number of users the devices can support using transfer speed (calculate using individual device’s speed instead of the total speed).

 

Relevant past paper:

DSE ICT Elect B(SP-2017): 2015 2b. 2016 3bi. 2017 2a, 3c.

CE CIT Elec C(2005-2011): 2006 1g. 2007 4di. 2008 3b. 2009 3dii. 2010 3ai.

 

Methods for Internet access

• Wireless network: e.g. Satellite, mobile phone network, 2G – 5G network
• Leased line (compared with broadband): fixed bandwidth (not shared with others), secure, stable and expensive

 

Relevant past paper:

DSE ICT Elect B(SP-2017): SP 3d.

CE CIT Elec C(2005-2011): 2010 2bii.

AS CA(2000-2013): 2006 10d.

 

References:

https://www.rfwireless-world.com/Terminology/wired-network-vs-wireless-network.html

https://www.actcorp.in/blog/what-is-leased-line-and-how-it-works

Network Security

 

Learning Outcomes:

• Describe the potential risks caused by the common network security threats.
• The threats include virus, worm and Trojan programs, spyware, unauthorised access, interception, and Denial of Service (DoS) attack, etc.
• Propose effective measures to improve network security for both wired and wireless networks.
• The measures include anti-virus software, authentication, access and user right control, packet filtering, firewall, public and private key encryption, Wired Equivalent Privacy (WEP), and IPsec used in Virtual Private Network (VPN), etc.
• Encryption mechanisms to guarantee a message is both authentic and private should be known. Detailed implementation algorithms of public and private key encryption are not required. Technical details on how a VPN is constructed are not required.

 

Network security threats

 

Virus: malicious program that injects malicious code into existing applications in order to spread.

Worm: malicious program that can self-replicate and infect other computers. This affects system performance and consumes network bandwidth.

Trojan programs: malware that disguises as legitimate software.

Spyware: malware that tries to keep itself hidden and steals sensitive information.

Adware: malware that hijacks your system and displays advertisements in your computer.

Denial of Service (DoS) attack: prevent users from accessing resources by overloading the network/system with fake communication requests. E.g. ping flood – overwhelm the victim with huge number of ping requests.

 

Relevant past paper:

DSE ICT Elect B(SP-2017): SP 4g. 2015 2cii. 2016 4d.

CE CIT Elec C(2005-2011): 2006 4g. 2008 1h. 

Network security measures

 

Antivirus

• Mechanism e.g. signature analysis: identify the specific code/pattern that the virus carries.
• Therefore, it is important to keep it up-to-date and active.

 

Authentication

• Password recommendations:
• Minimum 8-character length
• Multi-factor authentication
• Avoid common passwords or using personal information as password
• (regularly changing password and mixing uppercase/lowercase/non-alphanumeric characters are not recommended now)

 

Access and user right control

• Software control: block different ports e.g. USB port. Block certain IP addresses. User rights of operating system.
• Hardware control: MAC filtering (feasible if MAC addresses of devices known and infrequent update needed)

 

Firewall

• Mechanism: Packet filtering based on access control list. (Control inbound and outbound communications)
• Block packets based on criteria such as source IP addresses and port number.
• In terms of security, proxy server helps to hide the internal network IP addresses and restrict access to certain websites, while firewall filters unwanted packets.

 

Public and private key encryption (Asymmetric key encryption)

 

Sender A	Receiver B	Result
Use B’s public key for encryption	Use own private key for decryption	Only B can read the message
Use own private key for encryption	Use A’s public key for decryption	Message is really from A. (Digital signature)

Encrypt twice with both methods can serve both purposes. But it is also more time consuming.

 

Wired Equivalent Privacy(WEP)

See wireless network

 

IPsec used in Virtual Private Network (VPN)

• IPsec is used to set up encrypted connections between devices. IPsec is also implemented in IPv6.
• Virtual Private Network (VPN) establishes communication channel between you and the VPN server with the data encrypted.
• Disadvantages: complicated in configuration and connection speed can be slow.

 

Protocols with encryption

• HyperText Transfer Protocol Secure (HTTPS). Encrypted using TLS.
• Secure Sockets Layer (SSL). The newer one is Transport Layer Security (TLS).
• Secure Shell (SSH). For communication between computers.

 

Relevant past paper:

DSE ICT Elect B(SP-2017): SP 3b,ci, 4f. PP 2a(P1), 3ai,b,c, 4c. 2012 1bii. 2013 1bii,ci. 2014 3abii,c, 4aiii,ci. 2015 1bii, 2ci, 3c. 2016 2ci. 2017 1bii,c, 2cii.

CE CIT Elec C(2005-2011): 2005 4efg. 2006 3g, 4f. 2007 4f. 2008 2e, 4de. 2009 1bd. 2010 3e, 4bvi.

AS CA(2000-2013): 2003 10dii. 2004 9ci. 2006 4b, 10ceg. 2007 7, 9e. 2009 1a, 9f. 2010 9fii. 2011 8dg. 2013 10f.

For interest only: AS CA: 2003 10abcdi. 2005 2.

 

References:

https://securitytrails.com/blog/top-10-common-network-security-threats-explained

https://www.usnews.com/360-reviews/antivirus/how-does-antivirus-software-work

https://docs.microsoft.com/en-us/microsoft-365/admin/misc/password-policy-recommendations?view=o365-worldwide

https://www.tutorialspoint.com/network_security/network_security_firewalls.htm

https://www.preveil.com/blog/public-and-private-key/

https://www.gov.hk/en/residents/communication/infosec/digitalcert.htm

https://www.cloudflare.com/learning/network-layer/what-is-ipsec/

https://www.usnews.com/360-reviews/vpn/what-is-a-vpn

https://blog.robertelder.org/what-is-ssh/

 Network Management

 

Learning Outcomes:

• Develop the basic skills of monitoring and fine-tuning the performance of a simple network.
• Students should be able to use some simple network monitoring software to interrogate devices to determine their status and to obtain statistics about the networks for monitoring and fine-tuning purposes.
• Develop the basic skills of analyzing problems of a networked environment and performing troubleshooting for it.
• The problems may involve cabling, Network Interface Card (NIC), driver, Network Operating System (NOS), and configuration of a network, etc.
• Be aware of the importance of backup in disaster planning and recovery measures.
• Know the common hardware and software components of a network backup solution.
• Students should be introduced to the different components/technologies of a network backup solution including network backup servers, network backup and recovery software, Uninterruptible Power Supply (UPS), and Redundant Array of Independent Disks (RAID), etc.

 

Network performance

• Proxy server can improve network performance by caching a copy after a website being visited.
• This does not happen if
• First time visit (no local copy)
• Connection via HTTPS (no cache for HTTPS connection unless special configuration made)
• Live streaming

 

• Wireless network speed can be affected by
• Hardware – e.g. old standard WiFi router, access point location
• Interference – from channels with significant overlap
• Number of connected devices – sharing of bandwidth
• Network configuration – maximum speed is set

 

• Network speed can be affected by
• Cable vs wireless network
• Hardware – older devices/routers
• The service provided by ISP
• Computer processing power – both the client and the server
• Network traffic

 

Relevant past paper:

DSE ICT Elect B(SP-2017): 2013 2ci. 2014 3biii. 2017 2b.

CE CIT Elec C(2005-2011): 2007 2diii, 4dii. 2008 3c, 4b. 2010 3aii.

 

Network troubleshooting

 What to check

• Hardwares e.g. network interface card, cable, router
• Command tools
• Ipconfig: check the values of current default gateway and IP address
• Ping: check connectivity. Whether it can reach certain IP address.
• Tracert: show the details about the path that a packets take from the computer to destination.
• Nslookup: look for any DNS server issue. (or visit different websites)
• Other issues
• Port number related: e.g. Visit websites with different port number e.g. HTTPS, HTTP
• Device configuration: e.g. firewall setting
• Website related: e.g. web server issues, DNS server errors
• Network congestion

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  SP 4c. PP 2bc. 2016 4c.

CE CIT Elec C(2005-2011): 2008 3fii. 2009 2e.

AS CA(2000-2013): 2011 8f.

 

Network backup solution

 

• Uninterruptible Power Supply (UPS)
• Functions: 
• Protect against power failure by providing temporary power supply
• Protect against voltage drop by providing stable power supply
• During power interruption, UPS allows time for 
• backup creation
• the computer/server can shut down properly.

 

• Redundant Array of Independent Disks (RAID)
• Two or more drives working in parallel
• RAID 1 – mirroring: both drives have the same set of data. Requires at least 2 drives.
• RAID 5 – striping with parity: the data are striped across the drives together with parity data.  Requires at least 3 drives
• RAID 10 – combining RAID 1 and RAID 0 (mirroring + striping). Requires at least 4 drives
• These RAID configurations can protect against single drive failure. (but not RAID 0)

 

• Backup medium
• Magnetic Tape: Large amount of data with low cost
• Second Hard drive for RAID 1: see above
• External Hard drive: portability
• Network attached storage: storage with network capability. Essentially a drive within your network. Additional features may include access control, RAID and UPS.
• Cloud storage: Storage managed by third party and accessible through the internet.
• Advantages: Maintenance also by third party. Choose storage size according to need.
• Disadvantages: Security concern. Requires internet access.

 

• Backup
• How?
• Full backup: all data are copied.
• Advantages: easy to recover the data when needed.
• Disadvantages: slow backup time.
• Incremental backup: record the changes since last backup.
• Advantages: fast backup time.
• Disadvantages: slow recovery time. To restore data, need to have full backup copy + all incremental backup copies.
• When?
• Usually overnight, when the server/computer usage is low.

 

Relevant past paper:

DSE ICT Elect B(SP-2017): PP 2a. 2012 4c. 2013 4d. 2014 1f. 2015 2d, 4b. 2016 2abcii,iii. 2017 1e.

CE CIT Elec C(2005-2011): 2007 3d.

AS CA(2000-2013): 2003 10e. 2007 9c. 2008 10f. 2010 9a. 2013 4.

 

References:

https://network-data-cabling.co.uk/blog/Wi-Fi-17-factors/

https://www.techguide.com.au/news/10-things-affecting-internet-speed/

https://www.dnsstuff.com/network-troubleshooting-steps

https://www.ia.omron.com/support/guide/572/introduction.html

https://www.prepressure.com/library/technology/raid

https://www.aomeitech.com/nas/what-is-nas-storage-and-how-it-works-1234.html

http://www.nssit.com/how-to-choose-a-data-backup-medium/

https://www.business.org/it/cloud-computing/cloud-vs-network-attached-storage-pros-cons/

https://phoenixnap.com/kb/full-vs-incremental-vs-differential-backup

https://cloudpockets.com/best-time-to-backup/

 

 Network Design and Implementation

 

Learning Outcomes:

• Conduct a simple needs analysis on a proposed network and translate the needs identified into requirements and specifications.
• Design a network to meet the requirements generated in the needs analysis and represent it in a diagram.
• Justify their designs based on technical, cost effectiveness and other considerations.
• Set up simple Ethernet and wireless networks.
• Students should know the use of a subnet and know which subnet an IP address belongs to from a simple subnet mask.
• Share various resources among the networked computers/stations.
• The resources include files, printers and Internet connection, etc
• Set folder/ file sharing permissions, including read, write and execute rights, etc.
• Design a simple test plan based on the requirements and specifications to validate a network system.
• Document the user requirements, a schematic diagram for the network and specifications of the network.
• Documentation of industry standards is not required.
• Be aware of the importance of adequate end user support and training for the attainment of the benefits sought.
• Appreciate and value the use of various networking technologies in meeting different user requirements.

 

Network Diagram

 

Correct arrangement of the network devices.

Beware of the maximum number of ports.

 

Relevant past paper:

DSE ICT Elect B(SP-2017): 2017 4d.

CE CIT Elec C(2005-2011): 2005 4c. 2007 3cii. 2009 3ci. 2010 3b.

AS CA(2000-2013): 2005 10c. 2008 10a. 2009 9diii. 2012 7a.

 

Design Justification

 

• Connect device to switch or router?
• Considerations:
• Loading on the switch (number of connected devices)
• Router allows centralized management and security management
• Connecting to a switch allows easier access to the network within the switch (access not controlled by router)

•  Proxy server in front of or behind the router?
• In front of the router: hide IP address of the router for better security
• Behind the router: filter incoming data therefore reduce the loading on the server

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  2014 4ai,ii. 2016 3bii. 2017 2di.

 

Setup Network

 

• General considerations for setting up network
• User requirement
• Cost
• Network type
•  Default gateway = local IP address of the router

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  PP 1dii. 2013 1aii. 2014 2a. 2015 3dii. 2016 3cii,4bii.

CE CIT Elec C(2005-2011): 2010 1a. 2011 3c.

AS CA(2000-2013): 2010 4c.

 

Resource Sharing

 

Printer without intrinsic network capability:

• Connect to a host in a network. This host can make the printer sharable and manage the printing queue.
• Other hosts in the network can use the printer after installing the printer driver.

 

Network printer:

• It has a Ethernet port. Therefore, it can directly connect to a network or connect to a host.

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  PP 1e. 2015 1c.

CE CIT Elec C(2005-2011): 2007 4cii,iii. 2008 3e,g. 2011 1eii.

AS CA(2000-2013): 2009 7.

 

File Permission

 

Correct assignment of read, write and execute rights. (Access rights)

Device configuration e.g. firewall setting, OS setting.

 

Relevant past paper:

DSE ICT Elect B(SP-2017): 2014 2b. 2015 4d. 

AS CA(2000-2013): 2007 9giii. 2010 4d.

 

 

Test Plan

 

Design a test plan that is able to achieve the objective of the network. A test plan shall consist of test cases and test items.

Test cases E.g. stress test with higher than expected maximum load, performance test to check the response time.

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  2013 3ai. 2015 4ci.

CE CIT Elec C(2005-2011): 2007 3e. 2011 2div,4c.

 

Documentation

 

• user requirements
• schematic diagram for the network
• specifications of the network e.g. IP configuration

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  2015 4cii.

CE CIT Elec C(2005-2011): 2007 3f. 2009 4a. 2011 2diii.

AS CA(2000-2013): 2011 8a.

 

Other questions: Feasibility study, user training, survey, stages, system administrator manual

Relevant past paper:

CE CIT Elec C(2005-2011): 2010 1b. 2011 2di,ii,v.

AS CA(2000-2013): 2012 10c. 2013 1.

 

References:

https://www.toolbox.com/tech/enterprise-software/blogs/creating-a-network-test-plan-040508/

https://www.tutorialspoint.com/software_testing_dictionary/test_plan.htm