https://i.pcmag.com/imagery/articles/07CSW87UwsoIIArA9sMZXft-6..1569491760.jpg

Plan

  • DNS Main architecture
  • DNS Requests
  • DNS Zone file records
  • DNS Security
  • Useful commands / tool

DNS Main architecture


This post is a personal “pot-pourri” of some researches I have made on main memory (RAM) and OS initialization steps …

Plan

  • CPU real mode
  • CPU protected mode
  • Paging
  • Kernel memory management
  • Process memory management
  • ELF extension
  • Linux booting steps (for main memory)

CPU real mode

Most CPUs (Intel) start in “real mode”.
This mode…


https://images.bit-tech.net/content_images/2009/11/memory-and-multi-core-programming/4.jpg

This blog post follows the previous one on the Central Processing Unit (CPU).

“CPU, cores, tasks, hyperthreading, multithreading, user threads, multi-cores”
A lot of vocabulary exists when it comes to parallelism in CPUs / OS.
Moreover, we don’t know exactly what is responsible for what:
Hardware ? CPU ? Assembly ? OS…


https://images.frandroid.com/wp-content/uploads/2020/12/processeur-cpu.jpg

Plan

  • What is a CPU ?
  • CPU main components
  • CPU interrupts
  • AMD, Intel, ARM

What is a CPU ?

The Central Processing Unit (CPU) is the brain / heart of a computer as it executes instructions.
Instructions are coded in a language called “assembly” which is the only one spoken by the CPU.
Each CPU manufacturer has its…


‘VPN’ has become a catch-all term nowadays.
What does VPN mean ?
→ A software used to insure privacy on the internet ?
→ A way to connect 2 distant private networks together ?
→ An encryption mechanism ?
→ A tunneling protocol ?
→ A type of router / firewall ?
→ A layer 2…


This blog post aims to create a big picture of cryptography in the IT world.

Plan

  • Vocabulary
  • Symmetric Ciphers
  • Asymmetric ciphers
  • Diffie-Hellman key exchange
  • Hash
  • HMAC — Keyed-hash message authentication code
  • Digital Signature
  • Certificates

Vocabulary


In the last blog post, we studied the Internet Protocol and how computers can transmit packets between them.

Now let’s understand two most commonly used upper-layer protocols: UDP and TCP.

Plan

  • UDP
  • TCP
  • Socket abstraction

UDP (User Datagram Protocol)

UDP is very close to the lower protocol (IP) as it doesn’t add much features /…


This blog post aims to create a big picture of the Internet protocol (IP) and the internetwork infrastructure allowing the transmission of IP packets.

Plan

  • Main IP transmission principle
  • IP packet anatomy
  • Routers
  • How are IP addresses attributed to LIRs (Local Internet Registries)?
  • Routing inside a LIR?
  • Routing between LIRs: BGP…


Studying network programming, I understood how to use Linux sockets in order to communicate with other systems/computers. I also studied a lot of higher level technologies built on top of sockets such as http, ssh, ftp.

I wrote this blog post while improving my understanding of Linux kernel networking features…


Images are at the source of nearly every media. Therefore, I think it is interesting to get a glimpse of how images are stored on a computer. I have decided to get a tour of the most famous image format : jpg (or “jpeg”, as you may prefer).

Overview

  1. The basics

Grégoire Monet

I write my own computer science “cheatsheets” and “big pictures” as posts here. I mainly do it for myself but it may benefit others

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