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
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.
R eferences:
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
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.
