1.3 Computer networks, connections and protocols Flashcards
Local Area Network (LAN)
- Covers small geographical areas at single sites
- Hardware is usually owned by the organisation using it
- Can be wired on wireless
What can users on a LAN do?
- Access and share files on the network
- Share hardware
- Share an internet connection
- Log in from any device on the network
- Roll out security and software updates to all computers at once
Wide Area Network (WAN)
- Connect LANs in different geographical locations
- Organisations hire infrastructure (e.g. fibre optic lines or satellite links) from telecommunications companies who own and manage the WAN
- More expensive to set up than LANs
5 factors affecting network performance
- Bandwidth
- Number of users
- Transmission media
- Error rate
- Latency
Bandwidth
The amount of data that can be sent and received successfully in a specified period of time
Number of users
Too many users or devices on the same network can cause it to slow down if there is insufficient bandwidth available
Transmission media
- Either wired or wireless
- The type of cable used to transfer data, e.g. Fibre optic cable offers higher bandwidth than copper cables
Error rate
- When the transmission of data fails and it has to be sent again until it arrives correctly
- Quality of signal may depend on the distance if it is wireless, or the quality of the material used
Latency
- Delay between sending and receiving data
- Affected by the number of devices on the network and the type of connection device
Five pieces of network hardware
- Network Interface Controller (NIC)
- Switch
- Transmission media
- Wireless Access Point (WAP)
- Router
Network interface controller (NIC)
Allows devices to connect to a network -> usually built into the motherboard
Switch
Receives and transmits data between devices on a LAN using MAC addresses
Transmission media
Wires or wireless radio waves that allow data transmission between devices
Wireless Access Point (WAP)
Allows devices to connect to a network wirelessly. Similar to a switch
Router
Transmits data between networks by directing data as ‘packets’ to their destination
Wired networks
Tend to be faster and more reliable than wireless networks. Three cables to connect devices on an Ethernet (wired) network:
- Unshielded twisted pair (UTP)
- Coaxial
- Fibre optic
Unshielded Twisted Pair (UTP)
Copper wires twisted together in pairs to reduce internal interference
Coaxial
A single copper wire surrounded by plastic insulation and metallic mesh to shield from outside interference
Fibre optic
Transmits data as light. Can send data over long distances with little interference. High performance but expensive
Wireless Networks
Radio waves transmit data between devices on wireless networks. They tend to be cheaper and more convenient than wire networks.
Two common wireless technologies:
- Bluetooth
- Wi-Fi
Bluetooth
- Direct connection between two devices to share data
- Low bandwidth
- Max range -> 10 metres
Wi-Fi
- Can connect multiple devices to a LAN at once
- High bandwidth
- Max range -> 40-100 metres
Client-Server Networks
Files, software, user profiles and passwords are all stored centrally on the server.
Client sends a request to the server. Server processes the request and responds
Pros of Client-Server Networks
- Easy file tracking -> all stored centrally
- Back up files and update software easily
- Servers are reliable and always on
- Security -> Servers can request passwords or access levels before fulfilling requests
Cons of Client-Server Networks
- Expensive to set up and maintain
- If the server goes down, all clients lose access
- Servers can get overloaded with too many requests
Peer-to-Peer Networks
Devices connect directly -> no server
Files are stored on individual devices and shared with others
Pros of Peer-to-Peer Networks
- Easy to maintain without expertise
- No dependence on a server
Cons of Peer-to-Peer Networks
- Updates and backups are complicated
- Hard to track files -> copying between devices creates duplicate
- Data could be lost if one device fails
Star Topology
All devices connect to a central switch or server that controls the network
Pros of Star Topology
- Network unaffected if a device fails
- Easy to add more devices
- High performance
Cons of Star Topology
- Expensive for wire networks
- Switch is a single point of failure
Mesh Topology
No switch -> data sent along fastest route from one device to another
Partial Mesh Topology
Only some devices are connected to each other
Full Mesh Topology
All devices are connected to each other
Pros of Mesh Topology
- No single point of failure
- Add devices without affecting performance
Cons of Mesh Topology
- Expensive for wired networks
- Hard to maintain lots of connections
IP Addresses
Unique 32 or 128-bit identifiers given to devices when they access a network
Mac Addresses
Unique 48 or 64-bit identifiers given to network devices by the manufacturer
Network standard
A set of agreed requirements for hardware and software that allows different manufacturers to make compatible products
Network communication protocol
Rules for how devices communicate, and how data is organised and transmitted across a network
What are the 8 network protocols
- Transmission Control Protocol (TCP)
- Internet Protocol (IP)
- Hyper Text Transfer Protocol (HTTP)
- HTTP Secure (HTTPS)
- File Transfer Protocol (FTP)
- Simple Mail Transfer Protocol (SMTP)
- Post Office Protocol (POP)
- Instant Messaging Access Protocol (IMAP)
Transmission Control Protocol (TCP)
Rules for how devices connect to a network. Splits and reassembles data packets. Checks they’re sent and delivered
Internet Protocol (IP)
Directs packets to their destination across a network
Hyper Text Transfer Protocol (HTTP)
Web browsers use it to access websites and web servers
HTTP Secure (HTTPS)
Encrypts website information sent and received for security
File Transfer Protocol (FTP)
Accesses, edits and moves files between devices on a network
Simples Mail Transfer Protocol (SMTP)
Sends and transfers emails between servers
Post Office Protocol (POP)
Retrieves email from a server. Server deletes the email after you download it
Instant Messaging Access Protocol (IMAP)
Retrieves emails from a server. Server holds it until you delete it
Network Layers
Network communication is divided by functionality into layers. Each layer is self-contained. It serves the layer above it and depends on all the layers below it.
Pros of Network Layers
- Developers can each focus on one area of the network
- Layers can be changed without affecting others
- Standards develop ensuring compatibility between different pieces of hardware and software
Internet
A worldwide collection of computer networks
World Wide Web
A collection of websites hosted on web servers. Accessed through the HTTP protocol
URLs
Addresses used to access web servers and resources on them, e.g:
https:// - protocol
www.brainscape.com - domain name
/landing - Path to a file or page
Domain Name Service (DNS)
A service made of many domain name servers that store domain names and matching IP addresses
How does DNS work?
- Browser sends URL to DNS
- DNS finds matching IP address and sends it back to browser
- Browser requests web page from the web server at the IP address
- Web server processes the request and sends the web page back
Hosting
When a business uses its servers to store files for another organisation e.g. hosting websites on web servers or files on file servers
The Cloud
Servers accessed over the Internet that offer a range of services
What does the cloud do?
- Store and access data and files -> users need less storage space on their own computer
- Running cloud applications -> users can access software without needing it on their own computer
- Providing increased processing power -> users don’t need to have expensive hardware in their computer
Pros of the cloud
- Access files from any devices
- Easy to increase storage space
- No need for expensive hardware and the staff to manage it
- Host provides security and backups
- Automatic updates
Cons of the cloud
- Requires Internet connection
- Relies on host for security and backups
- Stored data can be vulnerable to hackers
- Unclear who has ownership of data
- Expensive subscription fees