Fundamentals of Communication and Networking

Serial Data Transmission

Data is sent one bit at a time over one communication cable

Parallel Data Transmission

uses numerous communication cables to send multiple bits between components in a computer simultaneously

Bit Rate

The number of bits that are transmitted over the medium per second

Baud Rate

The number of signals changes in the medium per second

Bandwidth

ranges of frequencies that a communication medium is capable of transmitting

Latency

the difference in time between an action being initiated and it effect being noticed

Parity

a technique that checks whether data has been lost or written over

Protocol

a set of rules relating to communication between devices

synchronised Transmission

When data is transmitted, a clock signal is used to time when signals are sent. The signals, which are sent at regular intervals, will be received in the same order that they were sent. Making them suitable for transmitting information in real-time systems.

Asynchronous Transmission

The requirement for a shared clock signal is done away with by using start and stop bits to indicate the duration of a transmission. The start bit can either be 0 or 1 and the stop bit is always the opposite. The sender and receiver must use the same Baud rate and need only synchronised clocks for the duration of data transmission.

Start Bit

synchronised receiver (clock) (to transmitter/data)

Stop Bit

Allows start bit to be recognised // allows receiver to process received bits

Star Topology

an arrangement where a central nodes or hub provides a common connection point for all other nodes

Bus Topology

an arrangement where nodes are connected in a daisy chain by a single central communications channel

WiFi

a protocol at the link layer allowing wireless communications

CSMA

a protocol to prevent collisions occurring over a wireless network

SSID

Identifies each network by a unique name

Router

routes traffic locally within the networks

Gateway

routes traffic to the internet

URL

specify the means of accessing a resource and its location across a network

FQDN

includes a host name, and the domain name

IP address

identifies a host computer or network node trying to communicate over IP on a network

DNS server

dedicated computers with an index of FQDN and their corresponding IP addresses

Internet Registry

responsible for allocating IP addresses to specific domain names

Proxy Server

makes a web request on behalf of your own computer, hiding the true request IP addresses from the recipient

Stateful inspection

examines the data contents of a packet before allowing access and remembers action s for future decisions

Symmetric encryption

use the same key to encrypt and then decrypt the data being transferred

Asymmetric encryption

Both communication parties have a pair of keys: Private key is only known to the individual (kept secret), Public key is known publicly

Digital signature

Sender: private, receiver: public, receiver: private, sender: public

Worm

exploit vulnerabilities in the destination systems and spread automatically

Trojan

malicious piece of software that masquerade as something seemingly innocuous or useful

Virus

self-replicating program which has malicious purpose

application layer

selects appropriate protocol for the communication

transport layer

establishes end to end communication

network layer

adds source and destination IP addresses

Link layer

adds source and destination MAC addresses

Socket

Combination of an IP address and a port

MAC address

uniquely identifies a physical device with a Network Interface Card (NIC)

Ports

used to alert a specific application to deal with data sent to a computer, used by protocols to specify what data is being sent

SSH

an encrypted protocol that allows secure communication between nodes across a network

Subnet Mask

used together with an IP address to identify the network identifier within the address

Routable IP

an address which can be accessed by another machine over the Internet

Non-routable IP

Devices are not directly connected to Internet

DHCP system

to automate the configuration of hosts connecting to a (TCP/IP) network

NAT

allows a single public IP address e.g. 12.65.42.1 to be shared by any number of hosts with private IP addresses

Websocket protocol

includes API for establishing a persistent TCP socket connection

Thin client

use low-powered processors in hosts specifically designed as network machines

Thick client

each host on the network would be a powerful computer in its own right