GSCE computer studdies (edexel) - unit 4 (networks)

Computer Network

Computers connected together for the purpose of sharing information and resources

why are computers connected in a network

enable communication for every business, entertainment, and research purpose

examples of computer networks

The internet, online search, email, audio and video sharing, online commerce, live-streaming, and social networks

LAN network

Local Access network, 2 or more linked computers in a small area

WAN Network

Wide area network covers a large geographical area, such as a country or the world, and typically consists of several smaller networks; the Internet is the world's largest WAN

structure of internet

a global network of interconnencted networks that communicate using a common set of standards and protocols.

IP Address (Internet Protocol Address)

A unique number identifying every computer on the Internet (like 197.123.22.240)

Routers

special purpose devices that are designed to read the source and destination address fields in IP packet headers to decide where to send (route) the packet next

Wired Connected Network

Network which has a stable connection and faster traffic speed. Therefore has good signal.

wireless connection

Uses radio signals, infrared technology, or satellite transmissions. no wires

what are network speeds measured in

bits

calculating file transfer time

transfer time = file size / bandwith

Ethernet

a system for connecting a number of computer systems to form a local area network(LAN), with protocols to control the passing of information and to avoid simultaneous transmission by two or more systems.

Wi-Fi

Wireless local area network that uses radio signals to transmit data

HTTP

HyperText Transfer Protocol - the protocol used for transmitting web pages over the Internet

Email Protocols

POP3, IMAP, SMTP

4 layer TCP/IP model

Application Layer (where network applications operate)

Transport Layer (set up data transfer between two hosts)

Network Layer (packages data for transmission, routes packets across network)

Data Link Layer (network hardware operate here - physical layer)

Bus Topology

A network layout in which there is one main trunk, or backbone, that all the various computers and network devices are connected to.

Mesh Topology

every computer connects to every other computer; no central connecting device is needed

Star Topology

A topology with one central node that has each computer or network device attached to the central node. All data first goes into the central node and then is sent out to its destination. (Think of it like a bicycle wheel with spokes.)

Network Security

A subset of communications security; the protection of voice and data networking components, connections, and content.

ethical hackers (white hats)

use expertise to shore up computer system defenses

data theft

Removing data from a computer without authorization.

Virus

A piece of code that is capable of copying itself and typically has a detrimental effect, such as corrupting the system or destroying data

IP spoofing

when an intruder uses another site's IP address to masquerade as that other site

Symmetric Encryption

the same key is used to encode and decode

asymmetric encryption

two keys are used; one key encodes the message, and the other key decodes the message

Penetration Testing

A test by an outsider to actually exploit any weaknesses in systems that are vulnerable.

Access Control

A security measure that defines who can access a computer, device, or network, when they can access it, and what actions they can take while accessing it.

Firewalls

software to prevent unauthorized users