how-internet-works.md

How the internet works

---

Bandwidth

• transmission capacity, measured by bitrate

Bitrate

• the number of bits per second a system can transmit
• byte = 8bit

Latency

• time it take for one bit to travel from sender to receiver

• download 3MB song in 3second

• 8 million bits = 1 megabyte

• bitrate = 8 Mbps

Send

	Pro	Con
Electric	cheap	Signal loss
Light (fiber optic cable)	Fast, No signal loss	Expensive
Radio	Wireless	Signal loss

---

IP address and DNS

• ISP (Internet service provider)
• Wifi - ISP - Connect all

Protocol

• All the different devices on the Internet have unique address just a number

IP (Internet Protocol)

• 174.129.14.120

• 1010110 10000001 00001110 01111000

• country/network.region/network/subnetwork.device

• IPv4

• IPv6

• DNS(Domain Name System)

• DNS Spoofing

---

Packet

• Packet of information
• Many kinds of digital information can be sent with IP Packets
• to many bits for one packet
• Packet ( from:12.123.123.41, to: 12.312.412.23 )
  • Where it came from
  • Where it's going
• Routers act like traffic managers to keep packets moving through the network smoothly
• Cheapest : time
• often the best route for data to travel isn't the most direct

Fault Tolerant, Reliability

TCP (Transmission Control Protocol)

• TCP+Router system scalable
• Connect, Communicate, Collaborate

---

HTTP and HTML

• Web Browser - url (uniform resource, locator) - server - http -

• HTTP (HyperText Transfer Protocol)

---

• GET /login -> HTML CODE

• HTML (HyperText Markup Language)

• Browser request several http GET request

• POST

• COOKIES - Web Browser, remember who I am

• Safe websites prevent snooping and tampering

• SSL : Secure Sockets Layer

• TLS : Transport Layer Security

• HTTPS : HTTP Secure

• Certificate Authorities

---

• HTTP & DNS manage the sending and receiving of web files (HTML, videos,...)
• TCP/IP and Routing break down and transport packets.
• Wires, Cables and Wifi, Binary sequences of 1's and 0's are sent physically through electric wires, fiber optic cables, and wireless networks.

---

Encryption, Decryption

• Today's secure communications are encrypted using 256 bit keys.
• Symmetric encryption
• Asymmetric encription
• Public key cryptography is the foundation of all secure message,

SSL & TLS

• https public key encription

---

Cybersecurity

• Viruses
• DDoS (Distributed Denial Of Service)
• PHISHING

Protocol A standard procedure for defining and regulating communicatin

• TCP (Connection based protocol) three way hand sake
• UDP (Connectionless protocol)