Ocr Computing 1.5

Front 1

Topology

Back 1

The physical arrangement/layout of the nodes and connection media of a network

Front 2

Star network

Back 2

All nodes are connected individually to a central connection point eg. switch/router/WAP/hub

Front 3

Mesh network

Back 3

All nodes are connected to every other node, many redundant connection lines. Every node not only sends signals but relays data from other nodes.

Can either be partial or full

Front 4

Hardware vs Software

Back 4

Client server/peer 2 peer = software

Star/mesh topolgies = hardware

Front 5

Star pro/cons

Back 5

Pros:

Add/remove devices easily

Less network traffic/collisions

If one node fails, all devices still work

Cons:

Dependent on central connection point

Expensive due to cabling

Front 6

Mesh pro/cons

Back 6

Pros:

Data transmitted simultaneously

If one route fails there is an alternative

It can manage high data traffic

Cons:

Very expensive due to more cabling+switches

Difficult to manage as continuous supervision is required

Front 7

Encryption

Back 7

Encryption means scrambling transmitted data so that it makes sense ONLY to the intended recipient.

Plain text is encrypted into CIPHER TEXT and then decrypted into PLAIN TEXT

You must also know:

WEP

WPA

WPA2 (CURRENT)

Front 8

WiFi

Back 8

WiFi is the standard for wireless networks.

It uses two radio frequency bands 2.4GHz and 5GHz.

WiFi performance is impacted by interference between networks using adjacent channels.

Front 9

2.4GHz vs 5GHz

Back 9

2.4GHz:

14 channels

Longer range

Slower

More common

Can go through dense material easily

5GHz:

50 channels

Shorter range

Faster

Struggles to travel through dense materials

Less common

More non over lapping channels so less interference

Front 10

Ethernet (very important)

Back 10

A set of network standards and protocols that controls how data is transmitted over a LAN

Hardware:

UTP cables (unshielded twisted pair)

Cable plugs/ connecters (RJ45)

Hub/switch

Software:

Protocols (TCP/IP stack)/Rules

Frames

Front 11

Ethernet Frame

Back 11

Data is packaged and sent between nodes using frames.

Destination MAC address

To

Source MAC address

To

Data/packet

To

Checks

Front 12

MAC

Back 12

Media access control

A unique identifier for a NIC (network interface card)

They are unique and can't be changed

They are made up of hexadecimal digits (6 octets long)

Hardware

(AB:20:30:19:FE:1B)

Front 13

IP

Back 13

Internet protocol

Addresses for nodes when sending/recieving information on TCP/IP networks

IPV4 (192.168.2.17)

IPV6 (hexadecimal)

Software

Static IP = can't change permanent/expensive

Dynamic IP = can change, be reused

Every device has an IP address and a MAC address

Front 14

Protocol

Back 14

Set of rules for how devices should communicate and how data must be transmitted

Front 15

TCP + IP

Back 15

TCP/IP (most common set of protocols)

TCP = Transmission control protocol = sets rules for how a device connects, how data is split into packets and checking that data was sent/recieved correctly

IP = Internet protocol = responsible for packet switching between nodes

Front 16

HTTP

Back 16

HyperText transfer protocol

(Make sure the T is capital and HyperText is one word)

Used by web browsers to access websites and communicate with web sources

Front 17

HTTPS

Back 17

A more secure version of HTTP that encrypts all info being sent and received.

HTTP + SSL

Front 18

FTP

Back 18

File transfer protocol

It is used to access, transfer, edit and make files

Front 19

POP3

Back 19

Post office protocol 3

Used to retrieve emails from an email server. Message is held on the server till you download it and then it is deleted.

Front 20

IMAP

Back 20

Internet message access protocol

Used to retrieve emails from the mail server, you download a copy, and the original stays on the server till you delete it.

Front 21

SMTP

Back 21

Simple mail transfer protocol

Used to send emails

Front 22

LAYERS

Back 22

Application layer:

Data

HTTP/HTTPS (browser)

IMAP/POP3/SMTP (mail client)

FTP (file manager)

data origin

Transport layer:

TCPUDP header

TCPUDD data

Uses TCP

Packetized

Network/Internet layer:

IP header

IP data

Uses IP

Each packet given address

Link layer:

Frame header

Frame data

Frame header link

Uses Ethernet

Converted into binary and sent

Front 23

Packet

Back 23

Packets are small equal sized units of data used to transfer files over networks.

Uses in network layer unlike frames which are used in the link layer.

Dest. IP + source IP + DATA = PACKET

Front 24

Packet switching

Back 24

A packet/string if packets travels from one node to another via different switches and connection medium and they rarely travel directly.