Chapter 3: Networks and Communications Flashcards
What is the intranet?
The internet used within an organisation, over LAN or VPN.
The intranet uses the internet protocol. What is it?
Protocol used for communicating data across the internet. IP delivers packets from the source host to the destination host based on their addresses
What is the extranet?
Private network that sits on top of the internet e.g moodle
Uses VPN for security
What is LAN and a WAN?
LAN - Local Area Network
- Connected by cables owned by user
- Close proximity
- Shares servers and local peripherals
WAN - Wider Area Network
- Large distance between computers
- Connected by third parties such as satellites
What is a peer-to-peer network?
Were all computers connected to the network act as client and server so they are all of equal status
What is a client-server network?
The computer called the server controls peripherals e.g printers, backup, and is connected to less powerful computers
Give 2 advantages and disadvantages to client-server?
Advantages
- Backup, security and antivirus centralised so individuals don’t have to worry
- Network processing done centrally, so clients not interrupted
Disadvantages
- Server is expensive
- Network manager is required which costs money
What is a switch?
Switch
- Network component that has a number of ports
- Data is examined to see the final destination and then sent to that port the device is connected to
What does a network interface card do?
Allows a device to be physically connected to the network to allow communication to pass to and from a computer
What is a wireless access point do (WAP)?
Sends and receives wireless signals when connected into the physical network by a cable
What does a router do?
Routes information between networks.
Connects a LAN to a WAN
What does a repeater do?
Used in a network to strengthen a signal
What does a bridge do?
Connects and passes packets between two network segments.
Allows data to be broadcast in one direction.
Name 3 types of server and what they do?
- File server - stores documents for access to user
- Proxy server - verifies and routes requests, bans those not permitted
- Print server - controls printing
Give 2 advantages and disadvantages of fibre optic cables?
Advantages
- Not much interference
- High bit rate
Disadvantages
- Expensive
- Only economical when bandwidth is fully utilised
Give 2 advantages and disadvantages of lasers?
Advantages
- Data transfer quick
- Used when laying cables not an option
Disadvantages
- Line of sight required
- Can be blocked by fog/mist
Give 2 advantages and disadvantages of infrared?
Advantages
- No cables
- Unlicensed
Disadvantages
- Line of sight needed
- Interference from other light sources
What is bandwidth?
The maximum amount of data that can be transferred along a communications channels at one time, measuring the volume of data per second over time
What is communications media?
The physical means used to transfer data
Give 2 advantages and disadvantages of Bluetooth?
Advantages
- Secure as you can enter a passcode
- Don’t need to have a line of sight
Disadvantages
- Limit on distance between devices
- Can only connect to one device at a time
Give 2 advantages and disadvantages of FAX?
Advantages
- Gives receipt of delivery
- Ability to hold address books
Disadvantages
- Received document can’t be directly edited
- No guarantee of where you are sending the FAX to
Give 2 advantages and disadvantages of teleconferencing?
Advantages
- Equipment cheap (webcam)
- Can be played back at a later date
Disadvantages
- Image quality is poor
- Power cut
What does ADSL stand for?
Asymmetric Digital Subscriber Line
What does ADSL run on and why?
Runs on copper cables on frequencies not used for telephone calls, so the telephone can be used for speech and data traffic
Give 2 advantages of ADSL?
- High speed connection
2. Can use the phone line while connected
State 2 disadvantages of ADSL?
- Not available everywhere
2. Distance is limited
Describe broadband using Cable?
The use of fibre-optic cables provided by television companies to deliver an internet connection
Give 2 advantages of Cable?
- High speed connection
2. Get telephone, television and internet in one service
Give 2 disadvantages of Cable?
- Physical cable needs to be installed
2. Speed advertised are not always guaranteed
Describe Wireless broadband?
Use of 2G/3G technology on mobile networks to allow internet access
Give 2 advantages of Wireless broadband?
- Connection is not limited to home location
2. Technology is always improving e.g 4G!
Give 2 disadvantages of Wireless broadband?
- Coverage depends on location
2. Expensive
What is a Leased Line?
A symmetric line connecting two locations
Give 1 advantage and 1 disadvantage of Leased Line broadband?
Advantage
1. Bandwidth is always guaranteed
Disadvantage
1. Costs a lot for the line to be installed
Describe the two types of Satellite used for broadband?
- One-way satellite broadband uses a satellite for downloading and a telephone line for uploading
- Two-way satellite broadband uses satellite for both uploading and downloading
Give 2 advantages and 2 disadvantages of Satellite broadband?
Advantage
- No need for fixed lines
- Mobile
Disadvantage
- Limited bandwidth
- Cost of technology
What does IMEI stand for?
International Mobile Equipment Identity
In 3 steps, describe what happens when a mobile phone call is placed over a cellular network?
- Phone places a call, sending a CALL INITIATION request to nearest base station containing IMEI
- Base station sends request to MOBILE SWITCHING CENTRE
- MSC asks if there’s enough credit and checks call bars. If allowed, connection is made via PUBLIC SWITCHED TELEPHONE NETWORK
Give two advantages of cellular network for mobile phones?
- Coverage is almost complete so phones can be used anywhere
- Use of data network means text and picture messages can be sent and web access is available
Give two disadvantages of cellular network on mobile phones?
- Loss of signal, battery and credit
2. Phones can be distracting for example when driving
What does a Satellite phone do?
Satellite phone connects with satellites within its line of sight. It relays the signal to the base station and then to telephone network
What are the two types of satellites?
- Low Earth Orbit
2. Geosynchronous Earth Orbit
Give 2 advantages of satellite phones?
- Can be used anywhere as long as it is in the line of sight
- Greater security as its harder to monitor calls
Give 2 disadvantages of satellite phones?
- Needs to be a line of sight
2. Bandwidth is low and costs a lot compared to cellular
What does GPS stand for and what is it used for?
Global Positioning System is used to locate the users position on the ground
Give 1 advantage and 1 disadvantage to GPS?
Advantage
1. High degree of accuracy
Disadvantage
1. Need a line of sight to the satellite
Give two advantageous ways in which satellites can be used in regards to the weather?
- Weather predictions can be made such as warnings for hurricanes or storms
- Impacts of natural and man made disasters can be viewed
Give two disadvantages for satellites being used for weather?
- Images taken need to be analysed/interpreted
2. Only a certain number of photos can be received with a polar orbit
Satellites can be used to transfer data such as banking information. Give 2 advantages and 2 disadvantages?
Advantage
- Secure connection
- Doesn’t need complex infrastructure
Disadvantage
- High cost
- Reliant on technology working
What does satellite television do and what does it need to work?
Gives the customer more channels than available through radio waves by using a decoder, which is usually a set-top box that separates free channels from encoded ones
What is a protocol?
A set of communication rules and the method of implementing a standard
Name 3 things that a standard governs?
- The format of the message
- The type of error checking to be used
- How the sending and receiving device indicates that the message has finished sending and receiving
What is a virtual network/VPN ?
A network that runs on top of a larger network as a subset. It is secured and acts as a private network so computers can be far away, but act as if they have local access
Give 2 benefits and 2 disadvantages of a peer-to-peer network?
Advantages
- No need for expensive server
- No knowledge needed as setup is done by wizards
Disadvantages
- Data stored on any computer so no organisation
- No responsibility for security, antivirus or backup
What are the 3 optical communication methods and give 2 situations where each of them are used?
- Fibre optic - lighting and aircraft communications
- Infrared - Mouse and car locks
- Laser - Mapping ocean floor and data transmission
What does laser stand for and how does it work?
Light Amplification by Stimulated Emission of Radiation
It outputs a electromagnetic energy field were all waves are at the same frequency and aligned
What is infrared and how does it work?
A focused ray of light in the infrared frequency spectrum.
It is sent from a transmitter to a receiver over short distances
What is infrared measured in?
Terahertz, or trillions of hertz (cycles per second)
Give 3 cables used as communication media?
- Fibre-optic
- Co-axial
- Copper
What is a copper cable also known as and what form does it come in?
Ethernet cable
Comes in twisted pairs called UTP and STP, which must be in the correct order to work
Give 2 benefits and 2 disadvantages of using copper cables?
Advantage
- Easy and quick to manufacture
- Standardised so work with most things
Disadvantages
- Uses electrical signals so there may be interference
- Water and damp underground may lead to corrosion
What is a co-axial cable also known as and describe what it looks like?
Also known as Coax
It has an signal wire in the middle, surrounded by an insulating layer, surrounded by a conducting copper braid, all covered in a outer plastic sheath
Give 1 benefit and disadvantage of using co-axial?
Advantage
1. Cheap to make
Disadvantage
1. Inference from other signals
Give 2 benefits and disadvantages of using wireless to use radio technology?
Advantages
- No physical connection required
- Worldwide standard allowing many devices to connect
Disadvantages
- Security issues if its not set up correctly
- Bandwidth is linked to the number of devices connected
Give 3 features of emails?
- Allows you to send messages to many people at the same time using lists and by sending carbon copies
- Add digital signatures and encrypt the message for security
- Pictures and text can be sent and edited with software on the recipients computer
What is IRC?
Internet Relay Chat, which is a text version of teleconferencing.
You can send real time messages, videos and pictures to groups of people
Give 3 features of bulletin boards?
- Forum where users post and read messages
- Accessed anywhere in the world through the internet with many people online
- Sets up threads of conversations to ensure posts on the same subject are kept together and users can be notified of a new posting
What does teleconferencing do?
Enables communication to take place between groups of people who are geographically remote using video and sound
Define broadband?
A fast, permanent connection across a wide band of frequencies
Who is satellite broadband regularly used by?
News companies to transmit their stories for television
What is the PSTN?
Public Switched Telephone Network, which is the standard telephone network
Give 2 advantages and 2 disadvantages of satellite television?
Advantages
- Free and encrypted channels can be broadcast, enabling companies to charge for services
- Remote areas that have problems receiving radio waves can get satellite
Disadvantages
- High initial set up cost
- Can be affected by weather conditions
What happens with weather satellites?
They observe and take normal or thermal pictures to analyse weather systems, such as predicting weather patterns or looking at the effects of pollution or natural disasters.
Define mobile technology?
Devices which are portable and allow you to communicate
Name 3 implications of mobile technology?
- Social
- Technological
- Financial
Give 2 advantages and disadvantage of mobile technology?
Advantages
- Call for help if you’re in trouble or let friends/family know where you are
- For business, you can connect to work location, and receive emails and up to date information
Disadvantages
- Cost of communication for the hardware and calls and messages
- Little chance to have a break from work as someone can always contact you
What can mobile technology also connect to and what will this give access to?
PDA or laptop for access to social networking, emails, news and weather
What is a network?
Two or more computers connected together so they can communicate and share data
What is full duplex?
Both uploading and downloading can be done at the same time
What is half duplex?
Either uploading or downloading can only be done one at a time
Give 3 protocols?
- SMTP
- IP
- FTP
What is SMTP and what is it used for?
Standard Mail Transfer Protocol
For transferring electronic mail
What is the IP and what is it used for?
Internet protocol
Used for connecting and transferring data across the internet
What is FTP?
File transfer protocol
Used for uploading website files onto the internet
What is bandwidth measured in?
Measures the rate of transmission in bps (bits per second)
Rank cable, infrared and wireless in terms of bandwidth, from lowest to highest?
- Infrared
- Wireless
- Cable
Describe 1 characteristic of wireless communications media?
There’s no physical connection as data is transmitted by electro-magnetic waves
What is a hub?
- Concentrator that connects lots of computers to the network through a single link
- Signals received sent to all other ports
