1.3 Computer Networks, Connections and Protocols Flashcards
Network
Formed when 2 or more computers are linked together in order to communicate + share resources
LAN full form
Local Area Network
LAN
A network covering a small geographical area on a single site
Computers are connected to each other
Who is hardware owned by in a LAN?
By the organisation
Are LANs wired or wireless?
Wired (e.g. using ethernet cables) or Wireless (e.g. using Wi-Fi)
WAN full form
Wide Area Network
WAN
Connects LANs that are in different geographical locations
Example use of a WAN
businesses with offices abroad
Who is hardware owned by in a WAN?
Hire infrastructure
Are WANs wired or wireless?
Wired
What medium do WANs use?
Fibre - Optic
Copper telephone lines
Satellite links
Radio links
What is the biggest WAN?
The Internet
Factors that affect Network Performance
Bandwidth available
Transmission media
Number of users
Network Topology
Choice of hardware
NIC full form
Network Interface Controller
NIC
allow a device to connect to a network. Each one has a unique MAC address
Switches
Connect devices on a LAN. Receives data in frames from one device and transmits the data to the device with the correct MAC address
Routers
Transmits data between networks. Directs data in packets to their destination
Recieves data between networks
Forwards data to their destination
Where are Routers used?
Homes / offices to connect a LAN to the internet
3 types of Transmission Media
Fibre Optic Cables
Coaxial Cables
Ethernet
Fibre Optic Cables
- Transmit data as light
- High performance/no interference =
expensive - Can transmit data over long distances
Coaxial Cables
Single copper wire with plastic insulation and metal mesh (shielding from outside interference)
Ethernet
Most common: CAT 5e, CAT 6
4 pairs of twisted cables -> to reduce interference
Bluetooth
Direct connection between 2 devices
Bluetooth connection range
10m
Bluetooth Bandwidth
Low
Bluetooth uses
Mobile/wearable devices
Wi-FI
For multiple devices to connect to a LAN at the same time
Wi-Fi connection range
40-100m
Wi-Fi Bandwidth
High
Wi-Fi uses
Home
Client - Server
Managed by a server
Files + software are stored centrally
Client - Server Relationship
Clients send requests to the server to access data
What does a client - server server store
Files
Passwords
Example of a client-server relationship
Websites are hosted on web – servers. Web browsers (clients) sent requests to the web – servers to access data
Advantages of a Client - Server
Easy to keep track of files
Easy to perform backups
Easy to install + update software
Disadvantages of a Client - Server
Expensive to setup
Server dependence - if the server is down then all clients lose their work
Server may become overloaded – too many clients access it at once
Peer to Peer
All devices are equal –> connect directly to each other
Where are files stored on a peer to peer
On individual devices
Uses of Peer to Peer
Home to share files between devices/share hardware
Advantages of Peer-to-Peer
Easy to maintain – no expensive hardware
No dependence on server – if one device fails the whole network isn’t lost
Disadvantages of Peer-to-Peer
No centralised management -> backups + software updates are more complicated
Copying files between devices creates duplicate files which can easily be lost track of
Topology
The layout of a network
How the devices are connected together
Examples of Network Topologies
Star
Mesh
Partial Mesh
Bus
Ring
Star Topology
All the devices are connected to a central switch/server
Wired or wireless
What is the central switch for in a star topology
Allows many devices to access the server at the same time
Advantages of a Star Topology
If a device fails/cable disconnects, the rest of the network is unaffected
Easier to add devices to the network
Very few data collisions
Disadvantages of a Star Topology
In a wired star network, every device needs a cable -> expensive
Centralised -> If the switch is not working, the whole network is affected
Mesh Topology
Decentralised – all devices are connected to each other
Send data on the fastest route from one device to another
Advantage of Mesh Topology
No single point likely to fail -> if a device fails, data can be sent on another route
Disadvantage of Mesh Topology
Wired mesh networks are expensive to set up
Partial Mesh Topology
All the devices are not fully – connected to each other
Bus Topology
All devices are arranged in a line, connected to a single backbone cable -> lots of data collisions
Ring Topology
All data moves in one direction to prevent collisions.
Only one device can send data at a time, and has to pass through many devices before reaching its destination
Network Standard
a set of agreed requirements for hardware and software
What is the point of network standards?
Allows manufacturers to create products/programs that will be compatible with other products/programs or will work on other systems
Network Protocol
A set of rules for how devices communicate + how data is transmitted on a network
Communication Protocols
specify how communication between 2 devices must start and end (how data must be organised, what to do if data goes missing)
MAC addresses full form
Media Access Control address
MAC address
For communication on the same network
Used by ethernet protocols or LANs
IP address
For communication between different networks
What does every NIC have?
A MAC address
When are MAC addresses assigned
On manufacture -> unique, cannot be changed
Form of MAC address
48 or 64 bit
Converted to six groups of two hexadecimal -> for ease
What do LAN switches use MAC addresses for?
to direct data to the right device on a network
What are IP addresses assigned to?
Every device connecting to the internet is assigned an IP address so that it can be identified/located
Types of IP address
IPv4
IPv6
IPv4
32-bit, 2*32 possibilities
Split into 8–bit chunks, and each chunk is given a denary number
IPv6
128 bits, 2*128 possibilities
Split into 16-bit chunks, and each chunk is given a hexadecimal number
Why was IPv6 created?
Created due to increasing number of devices needing unique IP addresses
HTTP full form
Hyper Text Transfer Protocol
HTTP use
Used by web browsers to access websites + communicate with web servers
HTTPS full form
Hyper Text Transfer Protocol Secure
HTTPS use
More secure version of HTTP. Encrypts all information sent and received
FTP full form
File Transfer Protocol
FTP use
Used to access, edit and move files between devices on a network
POP3 full form
Post Office Protocol version 3
POP3 use
Used to retrieve emails from a server. The email is deleted from the server after the client has downloaded it
IMAP full form
Internet Message Access Protocol
IMAP use
Used to retrieve emails from a server. The email is remains on the server after the client has downloaded it (the client only downloads a copy)
SMTP full form
Simple Mail Transfer Protocol
SMTP use
Used to send emails + transfer emails between servers
TCP/IP
a group of protocols dictating how data should be transmitted between networks
TCP full form
Transmission Control Protocol
TCP use
How devices should connect to a network
Splits data into packets + reassembles them once they have reached their destination
Check if data is correctly sent + delivered
IP full form
Internet Protocol
IP use
Directs data to their destination across a network
Layer
a division of network functionality
a group of protocols which have similar functions
Characteristics of a layer
Self - contained
Data can only be passed between adjacent layers
Advantages of Layers
Self - contained -> they can be changed without affecting the other layers
Different people can work on different layers
Easier to identify + correct errors
Forces companies to make compatible/universal hardware + software -> that will work together
Internet
a worldwide collection of networks linked together as a WAN. Based around TCP/IP
World Wide Web (WWW)
a collection of websites that are hosted on web servers
URLs
addresses used to access web servers and resources on them
URL full form
Uniform Resource Locator
DNS
translates domain names (URLS) into IP addresses. The IP addresses are stored on Domain Name Servers
DNS full form
Domain Name Service
Hosting
when businesses use its servers to store files of another organisation
Cloud computing (‘the cloud’)
acts as an extension of a client – server network, where user files are stored centrally on a network server
Advantages of the Cloud
Users can access files + applications from any device
Easy to increase available storage
No expensive hardware
Disadvantages of the Cloud
Needs internet connection to access
Dependent on host’s security -> vulnerable to hackers
Subscription fee
Connection may be slow
How does a device open a website
- The website is hosted on webservers
- The website had an IP address
- The web browser sends URL to the DNS
- The DNS finds the matching IP
- If IP is not found, browser sends request to higher DNS
- IP is sent back to the web browser
- The web browser sends a request to the webserver
- The webserver processes the request for the website
- The webserver sends the website to the user
