Computer Science
Define a 'network'
A group of devices connected together to communicate with each other and share sources
Define a domain name
A user friendly name to save us from remembering IP addresses
Define a topology
An arrangement of computing devices that form a network
What is a switch
A device that connects devices to a & uses packet switching to recieve, process and forward data to the destination device
Define a cable
A physical path for data/info to be transmitted to
Define a NIC
A card( built in or inserted to the motherboard) required to connect a device to a network
Define a WAP
A device that enables a device to connect to a network
Define a hub
A device that allows multiple devices to connect to a network
What is a standard
A set of hardware and software specifications that allow manufacturers to create products and services which are compatible with each other
What is a protocol
A set of rules of the format of digital transmission
What are the three protocols used for emails
SMTP
IMAP
POP3
What does POP3 do?
downloads emails stored on a remote server to a local client (Removed after the download)
What does IMAP do
Manages emails on a server so many clients can access the same email account in synchronisity
What does SMTP do
Sends emails and forwards them to their destinations
Define 'Packet Switching'
A network communication method that breaks down data into smaller packets which are sent separately along different routes and reassembled at their destination.
Define 'Circuit Switching'
Where a communication path is made between two devices (for the duration of their conversation) and all packets are sent along the same route
What does FTP do
Transfers files across a network
What does HTTP do
It's the primary protocol for transferring web content(text, images and videos)
What does HTTPS do
The same as HTTP however web content is encrypted
Name the 4 layers in the TCP/IP stack
Application
Transport
Internet
Link
How does the 'Application layer' work
-Network applications operate at this layer(e.g. web browsers)
-It prepares data for transmission over the network by converting it into a format that can be sent and received over a network
How the 'Transport layer' work
- Sets up communication between 2 hosts
- Breaks down data into packets. Each packet is given a port number(so the data can be reassembled in the correct order). They're also labelled with a header containing information about the packet
How does the 'Internet layer' work
It adds a header to each packet including the sender's and receiver's IP address. It then routes the packets across the network using the IP addresses in the headers
How does the 'Link layer' work
Adds the MAC address of the source & receiving device. When transmitting data across a WAN, the MAC address is changed at each hop, until it reaches its final destination.
Define 'Encapsulation'
Wrapping data with necessary protocol information before it is transferred.
What is a router
A device used to connect two or more networks together
Explain the process of typing URL into a web browser
- User enters URL of website into web browser
- The computer checks its local cache to see if it is already has the IP address from the URL
- If not, the web browser sends a query to the DNS server (provided by your ISP/ Google DNS)
- The DNS resolver checks its own cache, if it doesn't have the IP address, it queries other DNS servers
- The resolver queries the DNS root server, which directs it to the appropriate TLD server
- The TLD then givrs the resolver the IP address of the domains authorotative DNS server
- The resolver queries the authoratative DNS server for the IP of the specific domain
- The authorotative DNS server sends the IP address of the requstes domain
Why are protocols important?
They allow different devices to communicate with each other. The data sent is understood by both the sender and receiver
Why do we use layers in networking
- Layers allow interopability, meaning they can work together effectively
- It simplifies tasks by breaking them down into more manageable parts
What is the TCP/IP stack?
TCP/IP stack is a set of protocols that allow devices to communicate across the internet.
What does the DNS do when seacrhing for a website
- User requests a URL via a browser (e.g. www.google.co.uk)
- The browser sends the domain name to a DNS
- The DNS maps the domain nme to an IP address & returns it to a browser
- A GET request for the web page is sent to the web server using the IP address
- The requested web page is then returned to the clients web browser