Chapter 2 Computer science

Data packets

small chunks of data that is broken down to transmit data through the internet use by the TCP (Transmission Control Protocol) 📦

Routing

Involves in finding the optimal path over the network 📍

Header

Destination IP, Originated IP, Packet number 📑

Payload

Actual data 💾

Trailer

Additional form of security or checks e.g Cyclic redundancy checks for error e.g checksum, Notification for end of the packet 🏁

Packet Switching

-> Method of sending and receiving data across the network. Data is broken down to packets

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Each packet is assigned a Packet Number

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Each packets have it's own route

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Router controls the route data packets taken

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Packets arrived and reordered by it's packet number 🔄

Packet Switching ADV

+ Less prone to interference and corruption

+ Saves time and bandwidth

+ Harder to hack the data

+ Easy to expand packet usage

+ No need a single line of communication ✅

Packet Switching DISADV

+ Packets can be lost and need to be resent -> Takes along time and cause corruption in data

+ Does not work for real time streaming -> Delay in the destination as packets need to be reordered ⚠️

Serial data transmission

Data are sent one bit at a time down a single line/wire/channel

+ This means less risks of interference as used only one line

+ More reliable over long distances

+ Transmit bits will not be skewed (not synchronised)

+ Used if the amount of data sent is small and only need low transmission rate/speed

+ Less expensive less requirements for hardware 🧵

Parallel data transmission

Several bits of data are sent down several channels at the same time-> each wire transmit each bit

+ Faster rate of transmission over short distances e.g internal computer components

+ Data can be skewed not synchronised when being transmitted

+ Data can also experienced a cross talk, an event of a bit flip can happen

+ Used when data sent is in large amounts

+ Requires alot of hardware 🚥

Simplex

data travel in one direction only e.g sending data to printer ➡️

Half-duplex

Data is sent in either direction but not at the same time e.g a walkie talkie 📶

Full-Duplex

Sent in both directions at the same time 🔄

Universal Serial Bus (USB)

type of Serial data transmission, an industry standard 🔌

USB ADV

+ Device are automatically detected and device drivers will be automatically uploaded

+ An industry standard with wide use + support different transmission rates

+ No need external power supplies

+ easy to add more USB ports with USB hubs

+ Backward compatible with previous versions + No need screw like VGA or other type of old cables ✨

USB DISADV

+Only supports 5m cable length over that error will occur + Veryold USB version will not be able to bu supported + Data transfer slow in comparison to the ethernet or other types of transmission methods ⏳

USB-C

Newer version of the USB with a round appearance and no orientation, much smaller and thinner than USB A that offers charging to laptops and phones, can carry data at a whopping 10Gbps of speed and not to mention it is backwards compatible too ⚡

Parity check

Method of error detection where the computer adds an extra parity bit to check for it's standard of use wether the data has experienced a bit flip which have two situation an ODD or an EVEN 🔢

Parity blocks

An upgraded version of parity bit where they add a new vertical columns to check in a two dimensional board to check for ODD or EVEN 📊

Check Sum

+ A Calculation is performed by the sending computer and attached at the trailer of the data packet using the agreed checksum algorithm

+ The data is then sent along the routes

+ The computer then checks the check sum at the trailer attached by the sending computer with their own calculation

+ An differences of colculatiosn mean the data have an error 🧮

Echo check

+ WHen the received computer received the data it made a copy of the data + The copied data is the sent abc by the sender + A comparison is performed between two data the original and the one sent back + The difference indicate an error -> It is entirely unclear where the data is corrupted at 🗣️

ARQ (Automate Repeat Request)

+ The receiving device gets the data block + Is no error detected a positive ack is sent back + If an error is detected the receiving device send a negative ack and request resent + If the sending device experienced a time out the data will be transmitted anagin and again until ackgnowledments are made or after a number of transmission 🔁

Check digit

A single digit is input to verify data integrity during transmission and input -> Error input could be +Incorrect digit entered + Transposition of digits +omitted or extra digits + Phonetics error of digits 🔍

Encryption

Makes the data unreadable so no body could read it, Used to prevent interception of data from hackers and eavesdropper 🔐

Plaintext

Original data 📄

Ciphertext

data which are encrypted 🔏

Symmetric encryption

+ Uses a single encryption key The same key is used to both encrypt and decrypt the data + The key is then used by the sender and sended to the receiver for decryption 🔑

Asymmetric encryption

+ Uses two keys Public and Private key -> Matching pairs of key is generated by the encryption algorithm + The receiver will send the public key to encrypt the data for the dender the sender then send the data to the sender who haves the private key to decrypt it. 🗝️