Types of Network 1

Learning Outcomes:

• Describe the characteristics of the different types of network, including the LAN, WAN and Personal Area Network (PAN).
• Describe the characteristics of basic network topology such as bus, ring and star.
• Describe the characteristics of a client-server network and a peer-to-peer network, and explain the factors that need to be considered in choosing between them as a network solution.
• The factors include the network services required, set-up and maintenance costs, and the workload of the network administrators, etc.

LAN, WAN, PAN

	WAN	LAN	PAN
Characteristics	Wide Area Network Not limited by locations e.g. a large company network with multiple LANs in different locations (interconnected by public network provided by internet service provider) e.g. internet Connect LANs together	Local Area Network Used in local area e.g. within a floor or building Connect local devices together: share resources and communicate with others	Personal Area Network Connect personal devices together e.g. Bluetooth headphone e.g. home office
Advantages	Large coverage	Faster than WAN Less complex than LAN Less expensive than LAN	Flexible and adhoc connection Easy to set up and use Low cost

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  SP 1ai. 2013 4eii. 2017 4ai.

CE CIT Elec C(2005-2011): 2005 2cde. 2007 3a.

 

Basic Network Topology

Bus topology:

• Advantages: fewer cables needed, simple setup, lower cost (fewer cables, no active communication devices)
• Disadvantages: all nodes receive and examine signals, backbone failure causes failure of entire network

 

Ring topology:

• Advantages: only one station can send data at a time thus avoid collisions
• Disadvantages: failure of any nodes or cables causes failure of the entire network, longer data transmission time

 

Star topology:

• Advantages: centralized network management, easy to expand the network
• Disadvantages: central connecting device failure causes failure of the entire network, more expensive to setup

 

Tree topology:

• Advantages: easy to expand the network
• Disadvantages: delay in receiving data of the child node

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  SP 4b. PP 1a. 2012 3e.

CE CIT Elec C(2005-2011): 2005 1def, 4a. 2006 3ab, 4b. 2007 3bc. 2008 1a. 2009 1a. 2010 1cii, iii. 2011 1ei.

AS CA(2000-2013): 2009 9ciii.

 

Client-server Network and Peer-to-peer (P2P) Network

	Client-server network	Peer-to-peer network
Characteristics	A server grade computer acts as the server to provide resources for its clients	No central server Each node can act as client or server i.e. request for or provide services Each node can control its own resource sharing
Advantages	Centralized management Easier to manage security	Less expensive and easier to setup No single point of failure
Considerations in choosing client-server / P2P network	Large number of users Centralized security management Centralized data management and backup Applications that require high processing power of the server	Small number of users Centralised security management not required Lower cost

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  SP 2a, di. 2014 2c. 2015 2a.

CE CIT Elec C(2005-2011): 2007 4ci. 2010 1ci. 2011 4a.

AS CA(2000-2013): 2007 9gi,ii. 2008 10c.

 

References:

https://network-support.com/what-is-the-difference-between-a-lan-and-wan-network/#:~:text=As%20opposed%20to%20a%20LAN,or%20accessible%20to%20the%20public.

https://www.geeksforgeeks.org/overview-of-personal-area-network-pan/

https://www.dnsstuff.com/what-is-network-topology

https://techdifferences.com/difference-between-client-server-and-peer-to-peer-network.html

https://sourcedaddy.com/networking/selecting-network-type-client-server-or-peer-to-peer.html

Data Communications Basics 2 - Data transmission

Learning Outcomes:

• Identify and describe the three communication models: simplex, half-duplex and duplex.
• Compare asynchronous and synchronous transmission in terms of timing and overhead.
• Know the simple concept of multiplexing and its function in sharing the capacity of data transmission media.
• Explain briefly the mechanism used to co-ordinate data transmission in Ethernet and wireless networks.
• Knowledge of both Carrier Sense Multiple Access with Collision Detection (CSMA/CD) and Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) is required.
• Understand the simple concepts of circuit switching and packet switching.
• The basic function of each component of a packet including header, data and trailer should be known.

Communication models:

• Simplex: communication is unidirectional. One of the devices sends data only, while another one receives data only. E.g. Radio. Advantage: simple and easier setup.
• Half-duplex: Both devices can send and receive data, but not simultaneously. E.g. Walkie-talkie.
• Duplex: Both devices can send and receive data simultaneously. E.g. Telephone, interactive TV programmes.

Relevant past paper:

DSE ICT Elect B(SP-2017):  2012 3c. 2013 2bi, cii. 2015 1ei. 2017 3ai.

CE CIT Elec C(2005-2011): 2005 2b. 2007 2e. 2010 2ai,iii.

 

Asynchronous and synchronous transmission

• Synchronous transmission: Transmitter and receiver are synchronized with timing signals. Data transfer with continuous stream of data. Therefore, it is suitable for large amount of data.
• Advantage: faster transmission time c.f. asynchronous transmission
• Disadvantages: costly
• Asynchronous transmission: sender sends 1 character each time. Time gap exists between data.
• Advantage: economical (cheaper hardware) c.f. synchronous transmission
• Disadvantages: slower transmission, larger overhead (larger amount of control bits) 

Relevant past paper:

DSE ICT Elect B(SP-2017): 2013 2bii. 2017 3aii.

 

Multiplexing

• When multiple data signals use a single line of transmission medium, a device called multiplexor combines the data signals into a 1 single signal for transmission through the transmission medium. At the other end of the transmission medium, a demultiplexor will break down the single signal into the original multiple data signals.

 

Relevant past paper:

DSE ICT Elect B(SP-2017): 2012 3b.

Carrier Sense Multiple Access with Collision Detection (CSMA/CD) and Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)

• CSMA/CD:
• Used in shared medium of a Ethernet
• The sender senses whether the transmission medium is in use or not. In case of a collision, the sender defers data transmission for a random period of time before retransmission.
• CSMA/CA:
• Mainly used in wireless medium as collision detection is not possible
• Aim at preventing collision
• The sender checks if the channel is in use or not. If the channel is in use, the sender waits for random time before resending checking signal.

Relevant past paper:

DSE ICT Elect B(SP-2017):  PP 1ci. 2012 1d. 2015 1eii. 2016 1d.

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

 

Circuit switching and packet switching

• Circuit switching:
• A dedicated connection is established. E.g. telephone system.
• Packet switching:
• A dedicated connection between two parties is not required.
• The data is divided into small parts known as packets. The packets are sent out and go through any network pathway that is readily available. The packets may then arrive at the receiving end in any possible orders.
• The receiving end will reassemble the packets in correct order and perform error checking.

 Relevant past paper:

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

AS CA(2000-2013): 2010 1ab.

 

Packet

• A data packet typically has 3 parts: Header, Body and Trailer.
• Examples of contents of each part:
• Header: packet length, source address, destination address, Header checksum
• Body: the actual data
• Trailer: bits that signify end of the packet

 Relevant past paper:

DSE ICT Elect B(SP-2017):  2015 1di. 2017 3aiii.

AS CA(2000-2013): 2011 4a.

 

References:

https://www.geeksforgeeks.org/transmission-modes-computer-networks/

https://www.guru99.com/difference-between-synchronous-and-asynchronous-transmission.html

https://www.tutorialspoint.com/difference-between-csma-ca-and-csma-cd

https://www.tutorialspoint.com/circuit-switching

https://www.tutorialspoint.com/packet-switching

https://computer.howstuffworks.com/question525.htm

Data Communication Basics 1 - Communications model and data encoding

Data Communication Basics 1 - Communications model and data encoding

Learning Outcomes:

Communications model and data encoding

1. Understand the simple model of communications.
• Components of the model include agent, input device, transmitter, transmission medium, receiver, and output device.
2. Know the basic concepts of data encoding.
• Distinction between data and signals should be known.
• Students should know that either form of digital and analog data can be coded into either form of digital and analog signal.
3. Understand some error detection methods.
• The error detection methods include parity check, checksum and cyclic redundancy check (CRC). Implementation arithmetic for parity check and checksum should be known.

Simple model of communications, Data encoding

Data vs Signal:

In simple term, data is the information that is in the form you can use or store.

When you want to transfer the data to another party over a network, the data will be converted into signal in order for it to be transferred over a transmission medium.

Analog vs Digital:

Analog data/signal: continuous in nature that varies with time. E.g. Sound wave, electromagnetic wave

Digital data/signal: a set of discrete values. E.g. data representation in computers – 1s and 0s

Transmitter: 

Convert data into signal for transmission. Depending on your data and transmission medium used, an appropriate transmitter is used. E.g. sending a file over an optical fibre means converting a digital data into digital signal for transmission. Broadcasting a CD with analog radio waves means converting digital data into analog signal. Details of the conversion are out of the exam scope.

Putting these into a simple communication model: 

An agent wants to send out something(data) which is stored or input into an input device. A transmitter will convert the data into appropriate signal (could be analog or digital depending on transmission medium) for transmission. The receiving end uses a receiver to convert the signal back into data. The output device can then use or store the data.

Relevant past paper:

DSE ICT Elect B(SP-2017):  2012 3a. 2013 2a.

Error detection methods:

Major source of error: interference or noise in the communication channel.

Parity check:

• Extra bit called parity bit is appended to each unit of data.
  10101010 1
• Odd parity check: the total number of 1s is odd number, as in above.
  Even parity check: the total number of 1s is even number. E.g. 10101010 0

Checksum:

• HKID and ISBN-10 use checksum.
• Example:
• ISBN number: 019852663-6 the last digit is check digit such that the weighted sum is divisible by 11.
• 0 x10 + 1 x9 + 9 x8 + 8 x7 + 5 x6 + 2 x5 + 6 x4 + 6 x3 + 3 x2 + 6 x1 = 231

Cyclic redundancy check:

                Details not required.

Comparison:

• Parity check: simple, but only able to detect odd number of error bits.
• Checksum: ease of computation, small overhead(single check digit attached to original data)
• CRC: able to detect burst error, which is more likely to happen. Easy to implement using hardware.

Relevant past paper:

DSE ICT Elect B(SP-2017):  2012 2c.

Reference:

https://isbn-information.com/the-10-digit-isbn.html

https://www.tutorialspoint.com/data_communication_computer_network/error_detection_and_correction.htm

https://freeitnetwoking.blogspot.com/2017/02/types-of-errors-in-data-transmission.html

 TCP/IP protocol suites 2
 

Learning Outcomes:

• Know the basic concepts of IP addressing including the scheme and classes of IP addresses.
• Compare TCP/IP protocol suites such as Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6) from an evolutionary perspective.
• Different versions of TCP/IP protocol suites are compared in terms of address size and their support for audio and video.

Internet Protocol (IP):

Features: Similar to UDP, it is unreliable and connectionless

Functions: IP addressing, encapsulation, routing and ultimately delivery of the IP packets to correct destination

 

IPv4 vs IPv6:

IPv4 address is 32-bit long. The number cannot cope with the huge demand from the expanding network. Thus, IPv6 is developed with its address which is 128-bit long. Additional features are also available.

Features of IPv6:

128-bit long addresses

Efficient packet handling: e.g. simplified header, traffic class, flow label

Improved performance: multicast – sending datagrams to multiple receivers in a single transmission

Improved security: e.g. IPsec fully integrated

Relevant past paper:

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

CE CIT(2005-2011): 2009 2c.

 

IPv4

Address classes:

Binary notation 11000000.10101000.00000000.00000001

Decimal notation 192.168.0.1

The IP address is separated by dots into 4 parts. Each part is called an octet. The leading bits determine the class.

Network address is for identifying the network while the host address is for identifying the devices in that network.

Class	leading bits	1st octet	Network address portion	Host address portion
A	0-------	0-127	1st octet	2nd-4th octet
B	10------	128-191	1st-2nd octet	3rd-4th octet
C	110-----	192-223	1st-3rd octet	4th octet
D	1110----	224-239
E	1111----	240-255

Class D and E are not important for the exam purpose.

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  SP 4e. PP 1di. 2012 4ai.

CE CIT(2005-2011): 2006 4e. 2007 2b. 2008 1f. 2011 3f.

 

Local(private) vs global(public) IP address:

Some IP addresses are reserved for private use (use in a LAN). i.e. it cannot be used to identify a network/host through the internet.

A router is in a special location where it is between 2 different networks, usually a LAN and the internet. The ISP assigns a public IP address for the router to use so that others can identify and reach the router through the internet. The router also has a private/local IP address so that devices in the LAN can reach the router. 192.168.0.1 is used by many routers as the default (local) IP address.

Relevant past paper:

DSE ICT Elect B(SP-2017):  2017 2ci.

CE CIT(2005-2011): 2009 2f. 2010 4bvii.

AS CA(2000-2013): 2009 9ei.

 

Network address translation (NAT):

The translation of local IP address into global IP address and vice versa. This allows the hosts in a LAN to communicate with the outside world.

A special form of NAT called NAT overload allows multiple hosts in a LAN to communicate with the outside world using 1 public address only. This helps to reduce the demand of the limited number of IP addresses. Port number is used to identify different hosts in the LAN.

NAT table:

Local IP address and source port	Port number used in NAT
192.168.0.3:10100	20000

 

When data is sent out from an application of a host, the router received the information 192.168.0.3:10100. This information is saved in the NAT table in the router and mapped to a new port number. Suppose the public IP address of the network is 11.100.100.100. The outgoing data will now have a source IP address and port number as 11.100.100.100:20000.

When returning data targeting 11.100.100.100:20000 reaches the router, it maps the port number 20000 to the local IP address and port 192.168.0.3:10100. The data will therefore be directed to the relevant host and application.

Relevant past paper:

DSE ICT Elect B(SP-2017):  PP 1div.

CE CIT(2005-2011): 2009 4c. 2010 4biv.

AS CA(2000-2013): 2007 2c.

 

Subnetting:

Reason for subnetting:

Usual IP address can be divided into network and host number based on its class as mentioned before. This represents 1 network with certain number of hosts. To facilitate network management, for example a large company, we want to divide the single network into a number of networks.

Use binary notation for understanding

Without subnet:

IP address                      192.168.123.132         11000000.10101000.01111011. | 10000100

(Default) subnet mask   255.255.255.0               11111111.11111111.11111111. | 00000000

                                                                                       Network address             Host address

The subnet mask determines which point to divide the IP address into network address and host address.

The default subnet masks for class A, B and C addresses are 255.0.0.0, 255.255.0.0 and 255.255.2552.0, respectively.

 

Subnetting a private network:

To divide a network into 4 networks, we use subnet mask 255.255.255.192 for a class C address.

IP address           192.168.123.0                11000000.10101000.01111011.00 | 000000

Subnet mask      255.255.255.192                11111111.11111111.11111111.11 | 000000

                                                                                    Network address             Host address

So, the four networks are:

11000000.10101000.01111011.00(000000)          192.168.123.0                     host addresses: 1-62

11000000.10101000.01111011.01(000000)          192.168.123.64                  host addresses: 65-126

11000000.10101000.01111011.10(000000)          192.168.123.128                host addresses: 129-190

11000000.10101000.01111011.11(000000)           192.168.123.192                host addresses: 193-254

For a class C network:

No of subnets	Subnet mask 255.255.255.x x =	In binary notation x =	Number of subnets	Number of host addresses in each subnet	Number of hosts in each subnet *
2	128	10000000	21	27=128	128-2
4	192	11000000	22	26=64	64-2
8	224	11100000	23	25=32	32-2
16	240	11110000	24	24=16	16-2
32	248	11111000	25	23=8	8-2
64	252	11111100	26	22=4	4-2

* The first and last address of a subnet cannot be assigned to a host.

 

Advantages of subnetting:

• Access control
• Data traffic management

Disadvantages of subnetting:

• Increased hardware cost
• Network management work more complicated

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  PP 1dii. 2012 4aii. 2013 1aii. 2014 1c, 2a. 2015 3di. 2016 4a, bi. 2017 4c.

CE CIT(2005-2011): 2009 4d.

AS CA(2000-2013): 2008 3ab. 2009 9cii, di, ii. 2012 7bc, 10dii. 2013 10 bi.   

References:

https://www.plixer.com/blog/network-layers-explained/

https://www.tutorialspoint.com/data_communication_computer_network/transmission_control_protocol.htm

http://www.internet-computer-security.com/Firewall/Protocols/Ports-Protocols-IP-Addresses.html

https://www.tutorialspoint.com/what-is-network-port

https://www.tutorialspoint.com/internet_technologies/internet_protocols.htm

https://www.tutorialspoint.com/ipv6/ipv6_features.htm

https://www.geeksforgeeks.org/network-address-translation-nat/

http://cactus.io/tutorials/ethernet/what-is-a-mac-address

 TCP/IP protocol suites 1

 

Learning Outcomes:

• Know the simple concept of layering in a Transmission Control Protocol/Internet Protocol (TCP/IP) reference model.
• The basic concept of data encapsulation across layers should be introduced.
• Explain the functions of TCP/IP.
  
  

TCP/IP protocol suite

TCP/IP protocol suite is a reference model with sets of protocols used in the internet/computer networks.

Layers	Purposes	Examples of protocols	Address schemes
Application layer	Provide user services	DNS, FTP, HTTP	-
Transport layer	Host-to-host connectivity	TCP, UDP	Port numbers
Internet layer	Host addressing, packet routing	IPv4, IPv6, IPsec	IP addresses
Host-to-network layer	Related to hardware connecting to the network e.g. topology, physical medium	MAC	MAC addresses

 Major function: connect host to internet and transmit data over networks.

Communication protocols: exchange rules in an agreed-upon format.

Encapsulation: When data segment goes through each layer(from higher to lower), additional information are included in the data segment as header +/- trailer. (Details will be covered in data packets later)

Decapsulation: When the data packet arrives its destination, it goes from the lower layer to higher. The additional information(header/trailer) will be used and removed by the relevant layer, then the decapsulated packet will be directed to the higher layer.

Relevant past paper:

DSE ICT Elect B(SP-2017):  SP 2b, diii. 2012 2a.

CE CIT(2005-2011): 2005 2a, 3d.

AS CA(2000-2013): 2008 10b.

 

TCP and UDP

Transmission Control Protocol (TCP) features:

• Reliable: the sender is notified whether the delivery of data packets is successful or not.
• Connection oriented: Establish connection before sending data.
• Reorder the received data packets into correct order.
• Error checking mechanism.

Key point: when completeness of data packet is important.

User Datagram Protocol (UDP) features:

• Unreliable: No acknowledgement of successful/unsuccessful data packet. It uses internet protocol which provides best effort delivery (but not guaranteed). (i.e. both UDP and IP are unreliable)
• Connectionless: No connection establishment
• No error checking.
• All of the above reduces overhead.

Key point: when timely transmission is important and few data packet loss is not important.

Programs using UDP: DHCP, DNS, VoIP (Voice over IP) service

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  2012 2b. 2013 2d.

 

Port number:

Port numbers are used by TCP or UDP to direct the incoming network traffic to corresponding protocols or applications. E.g. port number 80 is used by HTTP.

Three categories of port number:

• 0-1023: well-known ports
• 1024-49151: registered ports
• 49152-65535: dynamic ports

Port number is “borrowed” by Network Address Translation (NAT) for IP addressing. (see next section)

 

Relevant past paper:

DSE ICT Elect B(SP-2017):  2013 1ai.

CE CIT(2005-2011): 2008 2f. 2009 4c.

MAC addresses:

MAC stands for Media Access Control. MAC address, also known as physical address, is a unique number assigned, usually by manufacturer, to a network interface. It is used as an identifier.

Relevant past paper:

AS CA(2000-2013):  2010 9ci.

Network components

Network components

Learning Outcomes:

• Describe the function of network adapters.
• Compare different data transmission media.
• The transmission media include copper wires, glass fibers, radio, microwave, and infrared, etc. They are compared in terms of types of signal transmitted, levels of resistance to transmission impairments caused by attenuation and noise, capacity, transfer distance, cost, and security considerations.
• Compare the functions of the various network connecting devices.
• The network connecting devices include hub, switch, router, and access point, etc.

Network adaptors

A network adaptor/network interface card is the hardware that allows a computer to connect to a network.

Relevant pastpaper:

DSE ICT Elec B(SP-2017):  SP 1aii.

CE CIT Elec C(2005-2011): 2011 4bi.

Data transmission media

Cable: optical fiber, UTP/STP, coaxial

Optical fiber:

• Advantages: long distance, not affected by electromagnetic(EM) interference, high throughput*
• Disadvantages: expensive

Coaxial cable:

• Commonly used in Broadband* network and cable television network.
• Advantages: longer travelling distance compared with twisted pair cable.
• Disadvantages: lower capacity compared with twisted pair cable. (10Mbps)

Twisted pair cable: Unshielded twisted pair (UTP) and shielded twisted pair (STP)

• Commonly used in Ethernet network
• Reason for twisting: reduce EM interference (external EM interference and crosstalk from adjacent wires within the cable)
• Cross over cable vs straight through cable: due to different arrangement of the wires in the connector. In general, a cross over cable is used when connecting devices of same type. E.g. a computer to a computer or a switch to a switch.
• E.g of UTP cable: Cat 5e cable
• Advantages: faster than coaxial cable. (1Gbps for Cat 5e)
• Disadvantages: shorter travelling distance.

Wireless: radio wave, microwave, infrared

Radio wave:

• Common uses: AM radio, FM radio, TV broadcast, wireless technologies (e.g. Wi-Fi, Bluetooth)

Micro wave:

• Common uses: cellular phone, satellite networks, wireless LANs
• Advantages: long distance
• Disadvantages: affected by weather

Infrared:

• Common uses: remote controller, Infrared Data Association(IrDA) interfaces
• Disadvantages: short distance, must be in line of sight

Relevant pastpaper:

DSE ICT Elec B(SP-2017): 2012 3di. 2013 4ei. 2014 1a. 2017 1a.

CE CIT Elec C(2005-2011): 2005 1bc,2h. 2006 1d. 2007 1ab. 2008 3d. 2009 3e. 2010 2aii.

AS CA(2000-2013): 2007 9b. 2009 9a,bii. 2010 4a,9g. 2011 8b.

Network connecting devices

Router

• Major use: connect a network to another network (usually the internet)
• Mechanism: forward data packet via the best path according to the routing table
• Other functions, if applicable: Assign IP addresses to local workstations (DHCP function), firewall
• Ports: LAN ports for local network and WAN port for outside network, usually the internet
• IP addresses: local/private IP address (e.g. 192.168.0.1) and external IP address provided by ISP
• Disadvantages: more complicated in setup, expensive

Switch

• Major use: connects devices together in a network
• Mechanism: forward data packet to destination device via the connected port according to filter table/MAC table. Packet does not travel through unrelated ports.
• Ports: each switch port forms a “collision domain”. Collision does not occur across different switch ports as the traffic is managed by the switch. The devices within the same collision domain can still have collision as the devices can send packets at the same time.
• Advantages (compared with hubs): less collision à increase network throughput, devices less likely to receive irrelevant packets à less overhead impact on devices

Hub

• Major use: connects devices together in a network
• Mechanism: Forward data packet to all ports (affects network throughput)
• Advantages: cheap
• Disadvantages (compared with switch): collision more likely to occur when more and more devices are connected to the hub

Relevant pastpaper:

DSE ICT Elec B(SP-2017):  SP 1aiii,3a,3cii. PP 1b. 2012 1a,3dii,4dii. 2015 1a,4a. 2017 1bi,4aii.

CE CIT Elec C(2005-2011): 2005 4b. 2006 3cdef. 2007 1c,2a. 2008 1bcdg. 2009 1bg,2ab. 2010 1efg,4biii. 2011 3d.

AS CA(2000-2013): 2004 3a. 2005 10a. 2006 10bii. 2007 2a,9a. 2008 2ai. 2009 5,9bi,9ci. 2011 1a, 4d. 2013 10ai.

Learn more:

• Throughput: rate of successful message delivery (e.g. collision affects it)
• Bandwidth: maximum rate of data transfer
• Broadband: speed of internet access faster than dial-up internet access i.e. faster than 56 kbps.
• Other devices:
• Repeater
• Major use: Amplify weakened signals due to long travelling distance
• Bridge
• Major use: similar to switch
• Difference: usually only have 2-4 ports, slower than switch
• https://geek-university.com/ccna/differences-between-a-switch-and-a-bridge/
• Gateway (protocol converter)
• Major use: connecting networks which are using different network protocols
• Router is one type of gateways.
• Modem (comes from “modulator-demodulator”)
• Major use: converts data into signals suitable for transmission and vice versa.

References:

https://www.geeksforgeeks.org/types-transmission-media/

https://www.omnisecu.com/basic-networking/common-network-cable-types.php

https://www.typesnuses.com/different-types-wireless-communication-technologies/

http://datacombyfloyd.blogspot.com/2010/07/wireless-communication-and.html

https://itstillworks.com/functions-router-internet-6039986.html

Elective C Past Paper and References (Web Site Development only)

Elective C Past Paper and References (Web Site Development only)

Past paper:

CE CIT Elective D (2005-2011):

2005 1a-e,g 2 3

2006 1 3

2007 1 3

2008 1a-c 3

2009 1 2

2010 1 3

2011 1 3

DSE ICT Elective C (SP-2017):

SP 1 2

PP 2a-c,g 4

2012 1 2c,d 4

2013 1a 2b,c 3a-c

2014 1c,f 2a-d 4b,c

2015 1eiii 2 3b-e 4

2016 1a 2 3 4b,diii,e

2017 2d,e 3 4

Official References:

Reference Books

Niederst, J. (2012). Learning web design: A beginner's guide to HTML, CSS, JavaScript, and web graphics (Forth edition). USA: O’Reilly and Associates, Inc.

Pascarello, E. (2004). JavaScript: Your visual blueprint for building dynamic web pages (Secondedition). USA: Wiley Publishing, Inc.

Websites

Refsnes Data. (2015). HTML tutorial. w3schools. http://www.w3schools.com/html/default.asp.