1.3- Computer Networks, Connections and Protocols Flashcards
Packet
A small block of data which is transported from one computer to another.
Header
The part of the packet which contains the sender and destination addresses, the protocol being used and a packet number.
Payload
The part of the packet which contains the actual data which is being sent.
Source address
The address of the device where the initial message has been sent from.
Destination address
The address of the device where the message is going to.
Handshake
An agreement which must be made between two devices, before communicating over the internet.
Application
The protocols in this layer determine how the data will be transferred in applications. Web browsers, email clients and file transfer protocols operate here.
Data link
The layer where the network hardware is located such as the network interface card and cabling. Ethernet and Wi-Fi run here.
Internet layer
This layer routes the packets across the network using the IP protocol
Transport
Sets up the communication between the two devices communicating data and breaks the data in to the agreed packet size. TCP and IP run here.
IP address
A numerical address assigned to a device communicating data across the internet. This address changes. IPv4 format is 4 bytes, IPv6 uses 16 bytes for more addresses.
Error detection
When the receiving device detects that an error has occurred during the transmission of data. The data is then requested again.
Packet switching
A data network technology. A message is broken in to packets and then sent across a network using the most suitable routes between the source and destination
HTTP
An insecure protocol used between a browser and web server. Hypertext Transfer Protocol transmits HTML web pages from web server to client
HTTPS
Secure version of HTTP, the traffic is encrypted between the browser and the web server for security. Now fairly standard
TCP
Transmission Control Protocol - this sets up and maintains a reliable connection between two computers, e.g. client’s browser and web server
IP
This protocol describes how to route packets of data around networks. Short for Internet Protocol, it’s used by routers and switches to direct packets
IMAP
Alternative email protocol to POP, the client can read emails but they stay on the server, short for Internet Mail Access Protocol
FTP
Protocol for transferring files to and from a file server. File Transfer Protocol
SMTP
Rules for sending emails from client to server, and then server to server. Simple Mail Transfer Protocol
POP
Used by client to download emails from mail server. Post Office Protocol is older and less useful than IMAP
Wi-fi
Wireless connection standards are known by this 4-letter acronym, this describes how wireless devices connect
Ethernet
The protocols used at the lowest layer of a network, describing the rules for connecting hardware and cables
Protocol
A set of agreed rules which allow two devices to communicate. SMTP, HTTPS and TCP are all examples
Bluetooth
Wireless PAN technology that transmits signals over short distances between smartphones, computers and other devices e.g. headsets and fitness trackers
Encryption
Converting readable data into unreadable characters to prevent unauthorized access. Authorised recipients can reverse the process with the key. HTTPS uses it
IPv4
A version of the IP protocol that uses 32-bit (4-byte) addresses such as 104.16.15.221. There are only around 4 billion possible IPv4 addresses and we are running out, so IPv6 is now preferred
IPv6
The latest version of the IP protocol, it uses 128 bits (16 bytes) for every address so they will never run out. Addresses are shown as 4 pairs of hex bytes like this: a490::65d8:4282:7f30
Number of bits in an IPv6 address?
128
Number of bits in an IPv4 address?
32
Approximate number of IPv4 addresses, because IPv4 is limited to 32 bits giving 2^32 possible values?
4 billion
Standard
Published document that says how hardware or software must behave or interact, e.g. the Wi-Fi rules 802.11, the HTML structure and the cable types Cat 5e and Cat 6.
Layer
A level in the protocol stack. Protocols in each of these perform related services, and each must talk to the one above and below.
TCP/IP
The 4-layer “protocol stack” that makes the internet work. Includes Ethernet, IP, TCP and HTTP which all have a role to play in delivering a services over the web
Network
A collection of computers or devices connected via cables or Wi-Fi to share data, peripherals or an internet connection
Node
Any single machine connected to a network
Topology
The physical arrangement of connected devices on a network, the shape of a network (mesh, star)
Personal area network
Small network for data transmission over short distance. For personal use such as headphones, often uses Bluetooth