1.3 Computer Networks, Connections & Protocols Flashcards
Local Area Network (LAN)
A network that covers a small geographical area.
All hardware for a LAN is owned by the organisation using it. E.g. School
LANs can be wired (UTP cables, fibre optic) or wireless (Wi-Fi).
Wide Area Network (WAN)
A network that covers a large geographical area, connecting LANs together.
The Internet is a WAN, some infrastructure is owned by someone else e.g. telecommunication companies, ISPs.
WANs are connected with telephone lines, fibre optic cables or satellite links.
Client-Server Network
Every device is either a client or server.
A client establishes a connection with the server over the network.
Servers can backup and store data centrally, however can be expensive and difficult to run.
Peer-to-Peer Network
This network configuration has no central server.
Each computer is equal in responsibility and each has the ability to work as both a client and a server.
Bandwidth
The maximum amount of data that can be sent and received successfully in a given time.
Latency
The delay from transmitting data to receiving it.
Transmission media
Wired connections, particularly fibre optic, have a higher bandwidth than wireless connections.
The number of users
Too many users or devices on the same network can cause the network to slow down if there is insufficient bandwidth for the data.
Error rate
A greater number of errors that occur when data is transferred, means the data has to be resent until it arrives correctly.
Network Interface Controller/Card (NIC)
Connects a device to a wired or wireless network. All have a hardcode unique identifier called a MAC address.
Wireless Access Point (WAP)
Allows wireless enabled devices to connect to a network without cables.
Switch
Forwards packets between devices in other segments of a LAN. Uses MAC Addresses.
Router
Forwards packets between networks. Needed to connect a LAN to a WAN. It uses an IP address to route traffic.
Transmission Media - Copper Cables (UTP)
Data is transmitted through these using electrical signals, with insulation to reduce interference.
Copper cable is cheap and easy to install.
Transmission Media – Fibre Optic Cables
Data is transmitted through light.
Low latency and cover long distances – Expensive.
DNS (Domain Name Server)
Converts a website address (URL e.g. www.google.co.uk) into an IP address (e.g. 172.217.14.195) for routers.
Hosting
The storing of websites on domain name servers.
The World Wide Web (WWW) is the collection of web pages hosted on these servers. A hosting company will provide 24/7 access, high bandwidth connections and security.
The Cloud – Remote Service Provision
Servers that store data and programs remotely that can be accessed and used over the Internet are referred to as cloud servers.
Advantages/Disadvantages of the Internet
Access any time & anywhere.
Flexible storage capacity.
Automatic backup.
Do not need to purchase & maintain expensive hardware.
Environmentally friendly.
Need for a reliable Internet connections.
No direct control over the security of your data.
Legal implications: Data Protection Act 2018
Star Network Topology
All devices connect into the central switch.
Mesh Network Topology
Every device is connected to every other device.
Advantages/Disadvantages to Star Topology
A failure of one device does not affect any other devices.
New devices can be added easily to the network.
The whole network fails if the switch fails.
Advantages/Disadvantages to Mesh Topology
Messages can be received more quickly.
Messages should always get through as they have many possible routes (backups).
Expensive.
Difficult to set up & establish connections.
Requires a lot of maintenance.
Difficult to expand the network.
Wired – Ethernet
The main standard for wired connections is Ethernet.
Wireless – Wi-Fi & Bluetooth
Both common standards for wireless networks.
Wi-Fi and Bluetooth both use radio waves.
Advantages/Disadvantages to Wired Connection
Usually faster.
More secure than wireless as a hacker would need physical access.
Need to manually set up the cabling.
Hard to add new devices as each will require additional cabling.
Expensive.
Advantages/Disadvantages to Wireless Connection
Cheap.
Easy to connect new devices without new hardware.
Better for the environment.
Can be interference, particularly through walls.
Slower and less stable.
More security risks.
(Media Access Control) MAC address
A unique hexadecimal identification number assigned to every Network Interface card (NIC) used in network devices.
IP Address
Uniquely identifies a device’s connection on a network, and defines where it is located geographically.
IPv4 Address
Uses 32 bits to specify an address.
For readability, they are expressed in dotted decimal notation. Example: 69.89.31.212
Each decimal number (between 0 and 255) corresponds to a byte.
IPv6 Address
Uses 128 bits to specify an address.
Dotted decimal is too long, so they are expressed in colon hex notation.
8 groups of 16 bits (4 hex digits), separated by colons. Example: 2001:02b8:85a3:0000:8a2e:0370:7334
Protocol
A set of rules that govern communication on a network.
TCP/IP – Transmission Control Protocol/Internet Protocol
TCP provides an error free transmission between 2 routers.
IP routes packets across a wide area network (WAN).
Together they make up the TCP/IP protocol stack which is the foundation of communication over the Internet.
HTTP/HTTPS – Hypertext Transfer Protocol Secure
HTTP is a client-server method of requesting and delivering HTML web pages. It is the fundamental protocol of the World Wide Web (WWW).
HTTPS is the same as a HTTP except it adds in encryption and authentication. Used when a website needs to deal with sensitive information e.g. passwords or bank account details.
FTP – File Transfer Protocol
Used for sending files between computers, usually on a wide area network (WAN).
POP – Post Office Protocol, IMAP – Internet Message Access Protocol, SMTP – Simple Mail Transfer Protocol
POP retrieves emails from a mail server. It will remove it from server and transfer to your device.
IMAP is used by mail clients to manage remote mail boxes and retrieved email from a mail server.
SMTP sends emails to an email server.
