3.5 Networks Flashcards
What is required for a computer network?
Two or more computers
How is the network formed?
Either wirelessly or through cables
What is the purpose of a network?
To Exchange information and data between other devices and to share recources
What is a network?
A computer network is created when two or more computers are connected through a connection either physically or wirelessly
What is the internet?
It is a connection of networks, no one person or organisation owns the internet - this is know as collective or distributed ownership.
What is the world wide web?
A service which is offered on the internet
Networks: Benefits
Data sharing, collaboration
Security
Communication
Remote access
Roaming (same computer no matter where you log in)
Centralised management
Files are saved to a network server
Networks: Risks
Or disadvantages
Data breaches
Viruses
Malware
Expensive
Network speed could slow down
Hacking
Reliant on hardware
PAN
Personal Area Network - connects electronic devices within a user’s immediate area, it only ranges a few meters (an example would be Bluetooth)
A PAN is anywhere in the world as long as you are there.
LAN
Local Area Network - a computer network within a limited area
A LAN operates across a small geographical area such as a school, hotel using their own cabling using their own cabling or wireless
A LAN is owned and controlled/managed by a single person or organisation
A WLAN includes a router that allows devices to connect wirelessly
WAN
Wide Area Network - the technology that connects your computers, data centres, cloud applications, and clouds storage together.
Operate over a wide geographical location in which the computers communicate using resources supplied by a ‘third party carrier’ such as BT
The largest WAN is the world
Standalone
A computer that is not connected to any other computer via a network
What is a Data Packet?
- A small unit of information transmitted over a network, such as the internet, from one device to another
- Each communication is split into smaller pieces called packets
- Each packet will contain the same number of bytes
In addition to holding the payload, each packet is marked with the packet number so that the packets can be put together by the receiver
IP address
- Internet Protocol - the unique identifying number assigned to every device connected to the internet
- Like every front door in the world, every computer in the world has an IP
- IP addresses are four 8-bit numbers (0-255) separated by dots - 32 bits in total
- It is set in software and can therefore be changed
- It is hierarchical* - this means that it includes network, subnet, and host components - similar to a house address
- IP addresses are used by routers to determine the best path to the destination
*contains lots of different bits of information
Circuit switching
When you make a telephone call, a dedicated connection is set up between you and the person you are calling for the duration of the call
- This is called ‘circuit switching’
It works fine for phone calls, but there could never be enough lines for all the billions of people sending data across the internet
Packet switching solves this problem
Packet switching
Each packet is 512 bytes
Each packet is given a header containing:
- The IP address it is going to
- The IP address it is coming from
- The sequence number on the packet
- The number of packets in the whole communication
Error checking data
Router
Routers are a piece of hardware capable of routing packets from one place to another based on the IP address.
They make up the ‘backbone’ of the internet
Your home router, routes packets to the different devices on your home network
Internet routers route packets around the world like a mail sorting office
Network Interface Card (NIC)
It may be wireless with an antenna or wired with a network cable socket
It is built into networked device
Most modern computers and phones incorporate the NIC into the motherboard
MAC address
Media Access Control (MAC) is assigned to each Network Interface card by the manufacturer
Your computer may have more than one MAC address if it has both ethernet and WiFi connection
A smartphone will have two different MAC addresses, one for WiFi, one for Bluetooth
Switch
- Switches connect each node (computer) in a network
- They know the MAC address of all connected computers and devices
- When a packet of data arrives, they can send it directly to the correct computer
Hub
- Hubs also connect each node in a network but do not look at the MAC address.
- They send the data to all connected computers
What is a Star Topology?
Computers and other devices (known as nodes) all connect to the central switch/hub