6. Communications and Networking Flashcards
What does LAN stand for?
Local Area Network
What is a LAN?
A collection of computers and peripheral devices connected together on a single site.
Give an example of a LAN.
A school is likely to have a LAN.
What are the advantages of networking stand-alone computers into a LAN?
- Sharing resources - Files, peripheral devices, Internet connection
- Communication - Email, Messaging systems, File transfer
- Centralised management - Profile and security management, Software distribution, Users can access their files on any PC, Centralised back-up
How does connecting stand-alone computers into a LAN allow sharing of resources?
- Sharing folders and files
- Sharing peripheral devices
- Sharing an Internet connection
How does connecting stand-alone computers into a LAN allow communication?
- Chat systems
- File transfer between computers
How does connecting stand-alone computers into a LAN allow centralised management?
- User profiles and security can be managed centrally
- Software can be distributed across the network instead of installing on each individual computer
- Users can use any PC but still see their own files
- Centralised backup of all files
What are the main network topologies?
- Ring
- Bus
- Star
What is a topology?
A description of how devices are connected together in a network.
Describe a bus network.
- Computers connected to a single backbone (called the bus), ended by terminators
- Only one computer can transmit at any one time
What are the advantages and disadvantages of a bus network?
ADV
• Easy and inexpensive to install -> Less cabling
• Easy to add new computers
DIS
• If main cable fails, then whole network goes down
• Cable failures are hard to isolate because all of the computers in the network are affected
• Performance slows down as the traffic increases
Describe a ring network.
- Computers connected to adjacent computers in a ring
- Computers take turns to transmit, controlled by passing a token around. Computers can only transmit when they have the token.
- Transmission all in one direction
What are the advantages and disadvantages of a ring network?
ADV
• Not dependent on central computer (like a star network is)
• Token passing is simple and reliable
• Consistent performance, even with a lot of traffic
DIS
• Single node or link failure disrupts the entire network
Describe a star network.
- All computers have their own cable connecting them to central computer
- The central computer controls the network and is usually a switch or server
What are the advantages and disadvantages of a star network?
ADV
• If one cable fails, only one station is affected
• Consistent performance, even with heavy use
• Easy to add new computers
• More secure -> Messages from computer go directly to centre
DIS
• Expensive due to cabling
• If the central computer fails, the whole network goes down
What can be found at the centre of a star topology?
A switch or server (or a hub)
Describe how computers in a school might be connected in a LAN.
- Computers in a classroom connected by a star topology to a hub or switch (wired or wirelessly)
- Different classroom topologies linked by a star or bus topology
How does the size of a LAN determine what is at the centre of a star topology?
- Small network -> Server
* In a room which is part of a larger LAN -> Switch
What does NIC stand for?
Network Interface Card
What is a Network Interface Card (NIC)?
- The card that plugs into a computer to provide a connection to a LAN.
- Can be wireless or cabled.
- Holds the MAC address.
What allows a computer to connect to a LAN?
The Network Interface Card (NIC).
What is a server?
A computer designed to process requests and deliver data to other client computers over a local network or the internet.
What is a stand-alone computer?
One not connected to any other.
What is a network?
The term for two or more computers connected together.
What is peer-to-peer network?
A method of organising a network where:
• Devices are all of equal status rather than having specialised roles
• Each computer can access resources on another computer
• Each computer can act as a client or server at times
What is a client-server network?
A method of organising a network where:
• Some computers act as servers
• The computers (clients) make requests to these servers
• Management of the server is centralised at the server
Why might a peer-to-peer network be used instead of a client-server network?
If the office or network is small, the it is not cost-effective to run a client-server network.
Can any computer access files from any other computer on a peer-to-peer network?
Yes, as long as access rights have been granted.
What are the advantages of a peer-to-peer and client-server network?
PEER-TO-PEER • Easy to set up and maintain • No dependency on server CLIENT-SERVER • Centralised security and management • Back-up can be done from central server
What does WAN stand for?
Wide Area Network
What is a WAN?
A collection of computers and networks connected together over a geographically remote area (several sites).
Give an example of a WAN and explain why this is a WAN.
The Internet - it is a network of interconnected networks.
What does PAN stand for?
Personal Area Network
What is a PAN?
Usually a temporary wireless connection using a protocol like Bluetooth.
Give an example of a PAN.
The Bluetooth connection between two phones.
Do networks connected by a WAN need to be miles apart?
- No, it is not about distance. It is more about what is inbetween the two sites.
- For example, a highway that splits a campus will mean that the two LANs on either side will have to be connected by a WAN.
How can LANs be connected to make a WAN?
The school or business which owns them has to use hired infrastructure, which they have to rent from a network service provider.
What is a protocol?
A set of rules that defines how devices communicate.
Give some examples of protocol.
IP, HTTP, HTTPS
What things will a protocol cover?
- How the transmission will start (getting attention of the other computer)
- The transmission speed
- The significance of bits being transmitted
- How the bits will be delivered
- Error-checking procedures
What does IP stand for?
Internet Protocol
What is IP?
- The protocol used on the Internet, by which all computers, servers and routers communicate.
- It is used to find a route for messages through a network.
What holds the MAC address?
The Network Interface Card (NIC)
What is the MAC address?
- A unique hardware number allocated to every NIC.
* It allows messages to be transmitted between devices in a LAN (it works like an address on a letter does)
Can the MAC address on a NIC be changed?
No, it is hard-coded into the NIC.
How long is a MAC address?
48 bits, which is written as 12 hex digits.
What is a message?
A communication between devices, which is split into packets for sending across the network and put back together on the other end.
What is a packet?
A fixed sized part of a message which is sent across a network.
What are the parts of a packet being sent over LAN?
- Header with MAC address of receiver
* Payload (the actual content)
What is the Internet?
A public worldwide network of computers and networks, interconnected by a verity of communication links.
What is an interface?
A way of connecting two devices.
Does a Network Interface Card allow transmission wirelessly or through wires?
Both
What wires are usually used in LAN networks?
- UTP (Universal Twisted Pair) cables
* Fibre optic cables
What does a repeater do?
Regenerates and re-sends a weak signal.
What does a hub do?
It connects together computers and servers on a network. It sends signals from a computer to all the others by repeating the signal.
What does a switch do?
It connects together computers and servers on a network. It sends signals from a computer to a specific one by repeating the signal. It is able to direct the signal to the correct receivers.
What is the difference between a hub and a switch?
They are very similar in that they send signals along a network. However, a switch is able to direct the signal to the correct receiver, while a hub just repeats the signal to all of the receivers.
How does a switch work?
- It stores the MAC addresses of devices on the network
* It filters data packets to see which devices have asked for them
What is a wireless access point?
- The device to which a computer connects wirelessly.
* It can be a wireless hub or wireless switch.
Which device is required to connect a network to the Internet?
- Modem
* Router
What is the Internet actually made up of?
- Routers - these are much bigger and higher performance than those at school or at home.
- They form the backbone and IP is the protocol used between them.
What unique labels are used to differentiate between individual devices in a LAN and on the Internet?
- LAN -> MAC address
* Internet -> IP address
What is an IP address?
A method of labelling any device connected to the network with a unique numerical value.
Describe what an IP address looks like.
- 4 numbers separated by dots
* Each number is between 0 and 255
What is the range of each number in an IP address and why?
Between 0 and 255 because each one represents a byte.
What will a packet being sent over the Internet contain?
- Sequence number
- IP address of receiver
- IP address of sender
- Payload (the actual content)