[Fundamental] Networking

Question 1

What does TCP stand for and how does it open a connection

Answer 1

Transmission control protocol, it’s a connection-based protocol

It guarantees packet receival and order by establishing a three-way handshake

Question 2

Explain the TCP 3-way handshake

Answer 2

Consists of SYN, SYN-ACK, ACK. Sent with seq. number.

1 2 to establish client to server
2 3 to establish server to client

Syn is asking to open a connection

Ack is an acknowledgement, agreeing to open a connection

Question 3

UDP

Answer 3

User Datagram Protocol

• lightweight
• no ordering
• no handshake
• deliverance is not guaranteed
• used in multiplayer games, media, DNS lookup

Question 4

HTTP Method

Answer 4

• GET: reads a resource
• POST: creates a resource or triggers a process
• PUT: Creates or replace a resource (updates as a whole)
• PATCH: Partially updates
• DELETE: Deletes a resource

Question 5

Why is HTTP stateless

Answer 5

• each request is executed independently
• there is no link between two requests being successively carried out on the same connection

HTTP sessions allow users to save states between pages

• HTTP cookies
• server-side sessions
• JWT Token

Question 6

Persistent HTTP connection

Answer 6

HTTP keep-alive s the idea of using a single TCP connection to send and receive multiple HTTP requests/responses, as opposed to opening a new connection for every single request/response pair

HTTP/2 protocol uses the same idea and takes it further to allow multiple concurrent requests/responses to be multiplexed over a single connection

Question 7

JWT Token

Answer 7

Replace saving tokens in DB, a JWT consists of 3 parts:

• the encoded algorithm
• the encoded payload
• hashed header+payload+secret, to verify signature

the server just needs to verify if JWT Token is valid, if. yes user can access a resource

Question 8

cookies vs local storage

Answer 8

Everything in cookies are sent for every request

In local storage you can pick which info you wanted to send

Question 9

Explain HTTPS request

Answer 9

Extension of http, for secure comms over the internet

Flow:
- client: give me sample.com
- server: here’s my certificate and public key
- client: I trust this CA, I’ll verify
- client: I’ll create secret key and encrypt with your public key and share it to you
- all message are encrypted with secret now

Question 10

Explain HTTPS certification creation

Question 11

Why DNS uses UDP, explain DNS lookup

Answer 11

UDP is faster, requests are small, and fit well within udp segments