Network trouble shooting

HTTP is a Stateless protocol
Hyper Text transfer protocol

Backbone of the internet.
HTTP and the basics

Foundation of how to understand Internet

1) HTTP follows the standard client server model
Request Response model
We are a person eating at a kitchen
Server responding to us ( Fb, google, Amazon and such )

2) HTTP is a Stateless protocol
HTTP is independent and not related to any other transactions ( So its stateless )
So if HTTP is a stateless protocol, a lot of web applications track your state.
How do they do this ?
They use cookies + sessions
Sessions+cookies = stateful management of how web applications work.
Even though HTTP is stateless, we still get the functionality of STATE using other mechanisms

3) HTTP is an application layer protocol and sits on top of Transport layer protocol
99.9 % of cases, HTTP uses TCP as its Transport Layer protocol
If the Transport layer is here, the Application layer is a little above it in the Stack of Names.
TCP defines how the data is transmitted, and HTTP uses it.

HTTP never cares about all the details that TCP handles.
HTTP just requests the data, and gets the data back.
TCP is right below HTTP

4) When ever the client requests something, there is an action associated with it.
Method
GET , PUT, POST , DELETE, HEAD

GET - Getting a request
POST - Creating something new - Create a new object
DELETE - Delete
PUT - Updates the existing stuff

5) HTTP Server Finds Response Codes back to the client
Finds response status codes, that the servers make back to the clients.
100 's
200 's
300 's
400 's
500 's

Its up to the programmers to return the proper status code

Most of the time, the app doesnt return the correct response codes.

6) HEADERS:

HTTP Supports HEADERS
The header is the tiny bit of custom information that is sent along with the request and responses

The main purpose of the HEADERS is to tweak the operation of the request.

One header that we can include in the request side is the
content-type of the data that is returned.

I want the data, but i actually want to choose, what type of data i want to get back from the server.
So, we send a special header, i want it as a text file.
When they request stuff from the server.

The server is going to recognize and respond

When the server comes back with the data, it also includes custom headers.

CACHE-CONTROL:

Response-HEADER - Cache-Control

It actually depends on how all these are using them.

Its a really cool optimization of the technique.

These are two quick examples of headers.

IMP:
Headers are included both in the request side and in the Response Side.
There is no standard rule book.

There is no rule book for HEADERS, there are some application specific headers.
Developers can use their own SPECIFIC headers.

Cache control, is a really cool optimization technique of the internet, that determines how often these resources are cached by all the different clients that are using them.

Understanding this protocol is very important.

Source of the above Notes:
https://www.youtube.com/watch?v=SzSXHv8RKdM