You’re on a LAN with IP
10.0.10.20. You browse to a website athttps://test.website.com(10.0.20.5). Describe what happens.
This is a open question. There is no good nor bad answers, and multiple layers of understanding.
For the purpose of this article, I will introduce three levels of comprehension.
First layer
Web Server Processing
What “browsing to the website https://test.website.com” means in technical terms?
Your browser request to render the webpage hosted on test.website.com.
The webserver registred at this domain receives the HTTP request and processes it. It retrieves the requested resource, in this case the homepage.
Client Side Rendering
The homepage is downloaded on your browser. Most of the time, this html page has dependencies under the form of link and script.
Commons dependencies are stylesheets, scripts or images. At the rendering of the html file, theses dependencies are downloaded.
Answer n°1
Your type
https://test.website.comon your browser, thus sending a request to the web server. It receives the request and process it.It retrieves the requested resource, in this case, the homepage of test.website.com, and return it to your browser.
Your browser renders the webpage: it fetchs the homepage’s dependencies and display it on your screen.
Second layer
A more experienced candidate might include HTTP concepts in his reponse.
He also might notice that the protocol used is HTTPS.
TLS Handshake
The protocol used on that request is HTTPS. The TLS (Transport Layer Security) handshake is like a secure conversation that happens between your web browser and a website’s server when you connect to a secure website. Here’s a simplified explanation:
Hello Phase:
Your browser says “Hello” to the website’s server. The server responds with its own “Hello.” During this phase, they also exchange some information about the encryption methods they can use.Key Exchange Phase:
Your browser and the server agree on a method to securely exchange encryption keys. Think of encryption keys as secret codes that will be used to scramble and unscramble the information being sent between your browser and the server.Authentication Phase:
The server proves its identity to your browser, assuring that it is indeed the legitimate website you intend to visit. This is typically done using digital certificates, which are like online ID cards for websites.Ready to Communicate:
Your browser and the server now have everything they need to communicate securely. They agree on a common encryption method and have exchanged the necessary keys.Secure Data Transfer:
From this point on, any data exchanged between your browser and the server is encrypted using the agreed-upon keys. Even if someone were to intercept the data in transit, it would be extremely difficult to understand without the proper keys.
HTTP Request
Your navigator request the webpage by sending an HTTP Request. An HTTP request consists of several components, including:
- Request Method: This indicates the action to be performed, such as GET, POST, or HEAD. In this typical web page request, the method is usually GET.
- Resource Path: The specific resource on the server that you are requesting, like “/index.html” or simply “/” for the homepage.
- Headers: Additional metadata accompanying the request, such as information about the browser, accepted content types, and more.
- Body (for some methods): For methods like POST, the request may include data in the body of the request.
HTTP Response
Upon receiving the HTTP request, the web server processes it and generates an HTTP response. The HTTP response includes:
- Status Line: This line includes an HTTP status code (e.g., 200 OK for a successful request), indicating the outcome of the request.
- Headers: Similar to the request, response headers provide additional information about the server, the content type, and other details.
- Body: The actual content of the requested resource. For a web page, this is typically HTML, but it could also include other resources like images, stylesheets, or scripts.
- Cookies: The server might send cookies to your browser for session management or tracking purposes.
Answer n°2
An HTTPS connection is initalized with the webserver under the domain test.website.com: A TLS handshake takes place and an encrypted connection is opened on port 443.
Once the connection is established, your computer sends an HTTP GET request to the web server.
The web server receives the HTTP request and processes it. It retrieves the requested resource, in this case, the homepage of test.website.com, along with his dependencies.
The web server sends an HTTP response back to your computer. The response includes the requested web page content, status codes, and other relevant information.
Your browser receives the HTTP response and renders the web page, displaying it on your screen.
Third layer
DNS Resolution
When you browse to the website https://test.website.com, the first thing that will occur is the DNS (Domain Name Server) resolution. A client reach through HTTP with IP adresses. The action of resolving a domain with a Your computer is looking for the IP address associated with the domain of the website, test.website.com. It checks in his local DNS cache first. If not found, it send a DNS query to the configured DNS server.
TCP Connection
Establishing a TCP (Transmission Control Protocol) connection involves a series of steps between a client and a server. This is known as the “TCP three-way handshake”. Here are the simplified steps:
Client initiates connection:
The client sends a request to establish a connection to the server. This request consist of a SYN (synchronize) packet. The client sets the sequence number (SEQ) in the packet to an initial value.Server responds:
Upon receiving the SYN packet, the server acknowledges the request and responds with a SYN-ACK packet. The server also sets its own initial sequence number (SEQ) and acknowledges the client’s sequence number.Client acknowledges the response:
The client receives the SYN-ACK packet and sends an ACK (acknowledge) packet back to the server. The client also acknowledges the server’s sequence number.
At this point, both the client and server have exchanged the necessary information to establish a connection. The TCP connection is now established and data can be transmitted between them.
These steps ensure a reliable and ordered exchange of data between the client and server. The TCP protocol is designed to handle error recovery, flow control, and sequencing of data to ensure the reliable transmission of information across the network.
Answer n°3
Your computer checks its local DNS cache to see if it already has the IP address linked to test.webiste.com.
If not found, it sends a DNS query to your configured DNS server to resolve the domain name (test.webiste.com) to an IP address. The DNS server responds with the IP address (10.0.20.5) associated with test.webiste.com.Your computer initiates a TCP connection to the IP address 10.0.20.5 on the port 443, default port for HTTPS. A three-way handshake (SYN, SYN-ACK, ACK) occurs between your computer and the web server to establish an encrypted connection.
Once the connection is established, your computer sends an HTTP GET request to the web server, specifying the resource you want to retrieve (by default the homepage, which is commonely the index.html file).
The web server (at IP address 10.0.20.5) receives the HTTP request and processes it.It retrieves the homepage of test.webiste.com, and sends an HTTP response back to your computer. The response includes the requested web page content, status codes, and other relevant information.
Your browser receives the HTTP response and renders the web page, displaying it on your screen.