Network
Performance
The performance can be easily improved if the compression of the filed trasfered haven't been done. Here the list of commands to check the following:
- Nothing
- Gzip
- Brotli
Without compression:
curl -I http://website/main.js
WIth gzip compression:
curl -I http://website/main.js -H "Accept-Encoding: gzip"
With Brotli
curl -I http://website/main.js -H "Accept-Encoding: br"
What happen when you type in a URL in browser
DNS
Here how to find the DNS of a website
dig google.com
IP Addresses
Layer 3
ifconfig
Addresses:
- IPv4
inet - IPv6
inet6
They are used by layer 3
IPv4 is 4 bytes (32 bits), for example 1.1.1.1 4 * 8 bits = 32 bits
| bytes | 1 | 1 | 1 | 1 | 1 |
|---|---|---|---|---|---|
| bits | 00000001 | 00000001 | 00000001 | 00000001 | 00000001 |
IPv6 goal is to have more IP available as IPv4 doesn't have enough unique IP for everyone. NAT allow IPv4 to be still in used. NAT stand for Network Address Translation.
Packet
tcpdump -nnXSs 0 'port 80'
sudo tcpdump host www.google.com -n
And connect to google.com
HTTP Request
nc www.google.com 80
GET / HTTP/1.1
Then press enter twice
DNS (Domain Name Service)
nslookup www.google.com
dig +trace www.example.com
┌─────────────┐ ┌─────────────┐
│ ├────────▶ │ │ ┌─────────────┐
│ │ │ │─────────▶ │ │
│ │ │ │ │ │
│ │ │ │ │ │
│ │ │ │ │ Root │
│ │ │ │ │ Servers │
│ │ │ │ │ │
│ │ │ │ │ │
│ │ │ │ ◀─────────│ │
│ │ │ │ └─────────────┘
│ │ │ │
│ │ │ │ ┌─────────────┐
│ │ │ │─────────▶ │ │
│ │ │ │ │ │
│ │ │ │ │ Top │
│ DNS Client │ │ Recursive │ │ Level │
│ │ │ Resolver │ │ Domain │
│ │ │ │ │ Servers │
│ │ │ │ │ │
│ │ │ │ ◀─────────│ │
│ │ │ │ └─────────────┘
│ │ │ │
│ │ │ │ ┌─────────────┐
│ │ │ │─────────▶ │ │
│ │ │ │ │ │
│ │ │ │ │ │
│ │ │ │ │Authoritative│
│ │ │ │ │ Servers │
│ │ │ │ │ │
│ │ │ │ │ │
│ │ │ │◀───────── │ │
│ │◀───────── │ │ └─────────────┘
└─────────────┘ └─────────────┘
MAC Addresses (physical address)
Layer 2 Switches communicate over the MAC Address. Anything that's using a network interface is going to have a MAC
Everything that has a network
TCP, UDP and the Three-Way Handshake
Common Ports and Protocols
The OSI Model
Subnetting
HTTP Protocol
Goog resource to read: An overview of HTTP