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AL Information Technology > Network Components > Flashcards

Network Components Flashcards

1
Q

Hub

A

Use in Star Network
Allows multiple computer or device to connect to it
Layer 1 (Physical) in OSI layers
Data is repeated to every connected device

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2
Q

Switch

A

Similar to Hub
Layer 2 (Data Link) in OSI layers
Inspect the MAC address of data frame, and only forward the data frame to destination (note how different from hub)

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3
Q

Router

A

Layer 3 (Network) in OSI layers
Inspect the IP address of data packet,
Choose the best “route” for the packet to move to the destination
Packet switching

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4
Q

OSI Layers

A

There are 7 layers in OSI Model

  • Application * (HTTP, FTP)
  • Presentation
  • Session
  • Transport * (TCP)
  • Network * (IP)
  • Data Link (MAC)
  • Physical (wire, fiber, wifi)
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5
Q

Wireless AP

A

Connects Wireless (usually WiFi) to ethernet (cable) network

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6
Q

Network Interface Card (NIC)

A

The part of computer hardware that connects to physical network
a computer can have multiple NIC, e.g. a laptop computer usually has an interface for WiFi, another for bluetooth, maybe one for Ethernet as well

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7
Q

Repeaters

A

Repeat (extend) signal of a LAN
usually needed to extend the range of ethernet cable since ethernet cable can only travel about 100 meter

There’s also wireless repeater that extend the range of WiFi signal

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8
Q

Gateway

A

A device that act as a “portal” for LAN to WAN

All device within the LAN must go through gateway to connect to outside (Internet for example)

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9
Q

Bridge

A

Connects two LANs together and form one single LAN

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10
Q

Firewall

A

Can be hardware and software
Hardware firewall usually is also the Gateway of a typical LAN
Uses rules to filter incoming and outgoing traffic

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11
Q

Bandwidth

A

Maximum amount of data that can be transmitted in a media.
Usually measured in bits per second (bps)
Cat 6 Ethernet cable has about 1Gbps bandwidth
School WiFi is about 300Mbps (not internet, but from device to AP, also this number is shared amount all devices)

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12
Q

Bit Rate

A

Measured in bit per second
Bit rate usually relates to the quality of streaming media, where obviously higher bit rate results in higher quality but likely slower
e.g. Internet movie may stream at about 1Mbps or MP3 audio in about 100kbps

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13
Q

Bit streaming

A

A bit stream is a continuous flow of bits over a communication path.
Realtime bitstream - for example live video
On demand bitstream - think of Netflix

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14
Q

Packet Switching

A

Data splitted into small chunks call packet. Packet may take different route across the network to transmit to destination
May out of order, need to reorder after receiving all packets
Better utilise of the communication channel
No dedicated channel needed, channels are shared

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15
Q

Circuit switching

A

Before start communication, a dedicated channel is setup.
e.g. Landline telephone, after you dial and the other party pickup, a channel is established
Channel is not shared until it is released
Could be faster than packet switching (since the channel is exclusive use)

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16
Q

Message switching

A

Whole set of data send from source to destination, no predefined route
the set of data send to a node, and store until there’s chance to send to another node until it reaches destination

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17
Q

Optical Fiber

A

Very long distance (e.g. across the ocean) without the use of repeater
Very low latency (speed of light)
High bandwidth, very unlikely to have interference

18
Q

Laser (data transmission)

A

Laser is basically light beam, usually use Infra-red in data transmission
Infrared is not visible light, but widely use in similar application e.g. Remote control
So Laser requires sender and receiver are in “Line of Sight” – nothing blocked in between them

Laser transmission has high bandwidth
Quite easy to get interference: by objects blocking the devices or even sometimes the ambient light (direct sunlight for example)

19
Q

Bluetooth

A 
Low power consumption (great for device with very small batteries, e.g. tracking device, wristband)
Low bandwidth (compare to WiFi)
Short range
20
Q

WiFi

A

Relatively large range (about 50-100m)

Able to penetrate walls (about 2 concrete walls)

21
Q

Radio

A

In theory, bluetooth and WiFi are both radio waves (of 2.4GHz to 6GHz)
Those earlier wireless mouse/keyboard required to use a “dongle” to connect to computer, these are “radio” transmission, which is not using standards like bluetooth or WiFi
In general, radio is:
Higher Frequency => Less able to penetrate wall, shorter distance, higher bandwidth

22
Q

Protocol

A

Set of rules use in communication

23
Q

TCP/IP

A

Transmission Control Protocol (OSI layer 4)
Internet Protocol (OSI layer 3)
IP defines IP Address, and routing of data packet
TCP checks if message is complete and ask for resend if packet is lost, also reassemble the data packets in order

24
Q

FTP

A

File transfer protocol, for uploading and downloading file in server

25
Q

POP

A

Post Office Protocol

For Email client to retrieve emails, email will not keep in server after retrieval

26
Q

IMAP

A

Internet message access protocol

For Email client to retrieve emails, email will be kept in server

27
Q

HTTP

A

Hypertext transfer protocol

28
Q

Bit-torrent

A

A Peer-to-peer protocol for file sharing
File data is not stored on server, but on bit-torrent users’ computer

If someone want to share a file:

  • create a torrent file that contains trackers information
  • Trackers is a server that coordinates clients for upload and download data
  • share the torrent file

If someone wants to download file:

  • He need to get the torrent file (from the sharer)
  • Connects to tracker with a bittorrent software
  • Tracker will direct the software to some particular client that owns the part of the data he needed
  • Software will request and download from those peer and at the same time, share the bits with other people
29
Q

Hacking

A

Gaining unauthorized access to a computer system

30
Q

Malware

A

Malicious software

Incl. Virus, spyware, torjan horses etc.

31
Q

Denial of service attack

A

Attackers send a large amount of request to the server, to overload the server.
DoS is very hard to detect since attack request is no difference from normal request.

32
Q

Distributed DoS

A

Similar to DoS but the attack is from multiple networked computer.
Usually hackers install malware into computers on Internet, such that they can control those computers (called botNet) to launch DoS attack at the same time.

33
Q

Access Right

A

A user is granted certain access right on a computer network. This usually includes (CRUD):

  • Create
  • Read
  • Update
  • Delete
34
Q

Two factor authentication

A

Adding another type of verification on user identity on top of username-password.

It can include: phone SMS, email or even biometric

35
Q

Biometric Authentication

A

Biometric is using human characteristic to authenticate user.
By Biometric it replaces the need to username (telling the system who you are) and password (verifying you are who you claim to be)
Usually biometric is fast and more secure than username and password

36
Q

Backup

A

Make more than one copy of the original data, preferably in different storage device + multiple copies in different locations

37
Q

Encryption

A

Encoding data in a format that is unreadable to attackers, mainly in storing data and transmitting data.

38
Q

Data protection act

A

DPA used to protect people and their data.
UK DPA states that data must be:

  • Used fairly and lawfully
  • Used for limited and specific purpose that the user is aware of
  • Used in a way that is adequate, relevant and not excessive to what the user connected to
  • accurate
  • keep no longer than it is necessary
  • keep safe and secure
  • handled according to people’s data protection right
39
Q

Satellite communication

A

Satellite have mainly 3 types:
LEO - Low earth orbit <1500km
MEO - Medium earth orbit < 12500 km
GEO - Geostationary Earth orbit = 35800km, which spins the same speed as earth (i.e. station above a certain area on earth)

Usually further from earth, more coverage => less satellite needed to cover the whole earth
But further means higher latency => not suitable for realtime communication

40
Q

Global Positioning System

A

GPS use 24 LEO satellite
Constantly sending signal of current time
Receiver determines the distance from some (at least 4, in line of sight) satellites by calculating the time offset from the received signal

thus, GPS may not be very reliable in crowded city (building blocks line of sight) or some poor weather condition

AL Information Technology (4 decks)

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