day b4 panic

application

protocol to be used is decided based on application (send)

adds encryption (send)

passes on to transport layer (send)

gets data from transport layer (receive)

unpacks message ready for display by removing headers (receive)

decrypts message (receive)

transport

creates a connection between 2 devices

agrees communication settings

add error correction data

agrees on packet size

splits data into packets

adds packet number and total number of packets

adds the port number packets should use

internet

assigns IP addresses to identify source and destination devices (send)

determines best path for data to travel across networks (send)

breaks large packets into smaller ones for transmission (send)

packets extracted (receive)

IP addresses used to ensure it reaches the right device (receive)

link/network

receives layered data from internet layer (send)

MAC addresses are added to packet (send)

passes and receives data across wireless network

passes data back to internet layer (receive)

layers of tcp/ip

application

transport

internet

network/link

importance of protocols

ensures data can be exchanged reliably/successfully between different devices

allows standardization as different devices have different os/hardware

protocols allow data to be exchanged in a predictable way

router

connects networks together

assigns IP to devices

examines data packets and forwards them

wap

allows wireless devices to communicate with each other

sends and receives radio waves

examines data packets and forwards them

nic

gives each device a MAC address

allows a computer system to interface with a network

modem

changes a signal from digital to analogue

advantages of a LAN

share hardware

share files

share internet connection

centralized security

log on/access files from any machine on LAN

central maintenance

central backup/storage

central installation/update of programs

can monitor user activity

can control access levels

more secure

organisation owns all hardware/connections

why protocol layering

to apply protocols in order/one after the other

to provide independence of layers (self contained)

hides details from previous or next layer

each layer is well defined

breaks task down into manageable units

improved troubleshooting

each layer only communicates with adjacent layers which simplifies interfacing

hardware/software can be manufactured to fit one specific layer

allows for standards for individual tasks or layers to be developed

why packet is better than circuit switching

computer networks could involve multiple connections happening concurrently, in packet switching hardware can handle multiple connections simultaneously

computers pass vast amounts of data which may encounter transmission errors, packet switching means only individual packets have to be resent rather than the whole data stream

computers may be transmitting business critical data, packet switching means any network hardware failures can be mitigated by routing around it

transmission is safer from interception because it is impossible to intercept all the packets as they use different routes

very efficient use of network as each channel is only used for a short time

advantages of p2p

little admin needed

adding machine is simple

no single point of failure

cost efficient

advantages of client-server

only 1 point of failure

easier to manage users/access

easier to backup

easier to keep data secure

centrally administrated in one location

disadvantages of p2p

file duplication

no central maintenance can lead to security issues and vulnerabilities

disadvantages of client server

single point of failure

expensive to set up and maintain

what is meant by tcp/ip stack

stands for transmission control protocol/internet protocol

define protocol

each protocol belongs to a different layer

list layers

describe layers briefly

switch

connects multiple wired devices to the network

receives data and forwards it to the intended recipient

examines data packets and forwards them

routes based on MAC addresses to specific computer device

server

client computers connect to a server

server provides access to a resource or service

how dns plays a role in websites being loaded

dns is used to resolve ip corresponding to url

request sent to dns resolver

resolver checks its cache and if it doesnt hold url, it passes to tld name server which checks its cache and returns to answer or passes on to the authoritative name server

ip address is returned back up to the requesting client

or error if no resolution can be found

how dns plays a role when a domain name is typed into browser

user types domain name, sent to dns servers

dns servers map this domain to an ip address

if dns can’t resove, it passes request recursively to another dns server

dns server sends ip to browser so it can retrieve the website from the server on which it is hosted

ip address

a numerical address made of 4 numbers each between 0-255 / 32 hex digits

uniquely identifies a device on a network

logical identifier

why use ip address in a company

can help identify a user so company can potentially track users attempting to gain unauthorised access

ipv4

byte.byte.byte.byte

185.107.80.231 to binary form ywim, each digit between 0-255

ipv6

4hex:4hex:4hex:4hex:4hex:4hex:4hex:4hex

AB10:DB00:012B:69FC:0000:0000:0000:0000

why high bit rate could be important for videos over internet

video streaming requires a large amount of data in a short amount of time

time sensitive or else there are interruptions in video

how is a check sum used to check data transmissions for errors

bytes added together, any overflow is ignored, sent with data

same sum is done at the receiving end and results compared

serial data transmission

individual data bits sent one after the other along communication medium as a single stream

full duplex

communication can be done in both directions at the same time

bridge

connects different network segments

gateway

connects different types of network

translates protocols from one network to another

repeater

receives a signal and re transmits it

hub

receives data from a device and broadcasts it to all devices connected to it

cable/ethernet

carries digital data from one device/nic to the next

connects wired devices to the network

client side processing

carrying out code/processing tasks on users device usually in web browser

allows users to have interactive & dynamic experiences without constantly requesting data from server

done using javascript usually (and html, css also i think)

advantages of client side

enhanced user experiences

server load is reduced as processing tasks are offloaded to client, resulting in improved scalability & resource utilisation

user input can be instantly validated and feedback provided in real time

web applications can operate without active internet connection by using client side technologies to provide offline functionality

disadvantages of client side

potential security risk and puts intellectual property at risk as code can be seen by users (quick modification)

compatibility of devices and browsers may vary which can lead to issues with client side code

can slow page load time especially with large or complex operations

heavily dependent on javascript (if browser doesnt support, can cause problems)

server side

running code and carrying out operations on server

uses php, python, ruby, java

advantages of server side

improved security, control measures, ensuring secure management of sensitive data

uses resources of server to perform advanced calculations, manipulate data and interact with databases

ensures consistent behaviour across different devices & browsers as logic is centralised on server

disadvantages of server side

complex processing tasks can consume server resources and cause a decrease in overall server performance (increased server load)

may cause latency as it involves communication with server which could lead to slower response times

relies on availability & reliability of server infrastructure

limited real time interactivity

complex development

methods for exchanging data

csv

json

xml

sql

api

edi

rss

soap

problems that could arise with a flat file if a customer wanted to alter >1 record at a time

only one customer entry allowed because of key field so would not be able to add second entry

customer data already present/would be repeated resulting in redundant data and inconsistencies (if changes are made)

how could a flat file be altered to allow each customer to alter >1 record at each time

add in second table

primary key of customer is used as a field in second table as a foreign key

entity relationship

immediate addressing

operand is actual value which instruction is performed

direct addressing

operand gives the address which holds the value upon which instruction is to be performed

indirect addressing

operand gives address of a register which holds another address where data is located

indexed addressing

index register is used which stores a certain value, the address of the operand is determined by adding the operand to index register