4.9 Communication and networking Flashcards
What is the Internet?
The worldwide collection of networks that use the Internet Protocol Suite (TCP/IP)
What is a router?
A device that receives packets on a network and forwards them to correct destinations based on an IP address
What is a gateway?
- A device that receives packets on a network and forwards them to correct destinations based on an IP address
- A gateway is able to deal with packets travelling between networks using different protocols, by stripping off all of the header data and adding a new header in the format needed for the destination network
What is a domain name server?
A server that contains databases of IP addresses and their corresponding FQDNs.
What is an IP address?
An IP address uniquely identifies a device on a network, and defines where it is located geographically.
What is the link between a Domain Name and an IP address?
A domain name is a string that corresponds to an IP address.
What is a packet and what are the main components of a packet?
- A packet is what data being transported across a network is split into.
- A packet is made up of the header and the payload.
What is an NIC?
- A hardware component that connects to the motherboard and is hardwired with a unique MAC address
- It allows a computer to connect to a network
What are the steps in packet switching?
- Data is split into packets.
- Header is added to packet
- Packets are sent along the network, not necessarily along the same route
- Once packets arrived, they are re-ordered using their sequence number
- Acknowledgements sent from recipient to sender for each packet
- Transmission of a packet happens again if no acknowledgement is received
What does TCP/IP stand for?
Transmission Control Protocol / Internet Protocol
What are the four layers of the TCP/IP protocol stack?
- Application Layer
- Transport Layer
- Network Layer
- Link layer
What does the application layer do?
- It uses an appropriate protocol relating to whatever application is being used to transmit data
- It also interacts with the user via appropriate application software or the users system
What is the transport layer responsible for?
- establishing the โend-to-endโ connection
- splitting the data into packets once the connection is made
- sends and receives acknowledgments
What does transport layer add to each packet?
- The sequence number
- The total number of packets
- The port number the packet should use
What protocol does network layer use?
IP (Internet Protocol)
What protocol does transport layer use?
TCP (Transmission Control Protocol)
What does network layer add to each packet?
- Source IP address
- Destination IP address
What is a MAC address?
A unique 12-digit hexadecimal address hardcoded on each NIC for use as an address in network communications to uniquely identify any device.
What does the link layer do?
- Adds the MAC addresses of the source and destination device
- The MAC addresses are changed at each hop on the route
What is a socket?
A socket is the IP address (provided by the IP protocol) combined with the port (provided by the TCP protocol)
What is a port?
The port determines what application on the device needs the packet
How does SSH work?
SSH uses for port 22. It uses public key encryption to authenticate the user and prevent unauthorised access.
- ๐ The client initiates the TCP connection by contacting the server
- ๐ The server sends a public key to the client
- ๐ค The server and client agree communication rules and open a secure channel
- ๐ The user can now login to the remote server host operating system and can issue application layer commands such as GET for HTTP, and SMTP and POP3 commands for sending and retrieving emails
How does SMTP work?
SMTP sends the email from the client device to the linked mail server or forwards the email to the recipientโs mail server.
How does POP3 work?
- Retrieves email from a mail server
- Removes it from the server
- Transfers it to your device