What happens when you type holbertonschool.com in your browser and press Enter?
What happens when a web page is opened?
Millions of people visit many web sites every day, whether to consult information, search for products, enjoy social networks to be in contact with friends and family, play games, watch movies, listen to music or any other type of entertainment. For anyone, accessing a web page consists of just typing an address in the search bar, but the truth of the matter is that you stop there is a complex procedure that ends in the visualization of the browser page, in just a few seconds Without even noticing it, the browser comes into contact with web servers spread all over the world, consults stored data and from this data, a web page is displayed on the screen of a device connected to the internet. Let’s see in detail what happens behind the scenes.
- URL
It all begins when we enter an address in the browser’s search bar, this is technically called Uniform Resource Locator (URL), this identifies all web pages and allows them to be located on the internet. The URL is composed of several elements, each one of them has a specific function.
the representation of URLs in letters is intended solely for human compression, since computers work with combinations of numbers called IP addresses. That is why for a browser to display a web page, the URLn must be converted to an IP address, for this to be the case, the help of DNS servers is needed, responsible for the management of the domain name system or DNS. (Domain Name Server).
2. DNS
DNS is used to indicate to the user who types a domain to which server he should go to pick up the web page he wishes to consult.
Indeed the web pages are actually hosted under an IP address, for example our website holbertonschool.com actually responds to the IP 13.227.26.3 but this system is able to convert these numbers into the domain name holbertonschool.com. Remembering the IPs of each web page would be too hard work, that is why the domain name system was created, to allow creating terms and names that are easier to record
To avoid making constant queries to the DNS server, the browser will save this information temporarily, so that the web can be served without making this prior query. That is why on many occasions they ask us to update the query with the F5 key, so that the domain goes to the most current IP address.
3.Firewall
A firewall is a hardware or software device that allows us to manage and filter all the incoming and outgoing traffic between 2 networks or computers on the same network.
If the incoming or outgoing traffic complies with a series of Rules that we can specify, then the traffic will be able to access or leave our network or computer without any restriction. In case of not complying with the rules, incoming or outgoing traffic will be blocked.
Therefore, from the definition we can ensure that with a well configured firewall we can avoid unwanted intrusions in our network and computer as well as block certain types of outgoing traffic from our computer or our network.
4.SSL
SSL (Secure Sockets Layer) is a global security standard that allows encrypted data transfer between a browser and a web server. It is used by millions1 of businesses and individuals online to reduce the risk of theft and manipulation of confidential information (such as credit card numbers, user names, passwords, emails, etc.) by hackers and thieves. identities. Basically, the SSL layer allows two parties to have a private “conversation”
5.LoadBalancer
Load Balancing or Load Balancing is the distribution of internet traffic or applications among several servers. And for this it is necessary to have balancers or load balancers, devices that distribute that traffic through multiple servers using different methods to improve the general response capacity of the applications and increase their availability. This reduces the load on an individual server and also reduces the possibility that it may fail.
It is located between the client and the server farm that accepts incoming traffic from the network and applications. In this way, as application demand increases, new servers can be added to the resource pool to which the load balancer will send traffic immediately. This is why it is the most direct method of scaling the infrastructure of an application server.
When an application server is unavailable, the load balancer directs all new application requests to other available servers in the pool.
6. Web Server
A server is a computer (with its programs) that is at the service of other computers, electronic devices (printers, mobiles, etc.) and people to whom it supplies information.
All these subjects that receive the information from a server are known as clients.
It is known as the client-server model: the client asks and the server supplies it with the resources it needs. Therefore, the information can be in text, video, audio, images, emails, applications, etc.
A server is a more powerful computer than normal and is always on, since if it is turned off or gives an error, it will not be able to fulfill its function.
The web server is a server that stores the documents that make up a web page (HTML, CSS, PHP…) and provides it to the user so that she can view it in its entirety in her Internet browser.
A web server is a very powerful computer that remains connected to the Internet 24 hours a day and that provides all the necessary content for a website to be displayed to a user through their browser.
7. App server
Is a computer specially designed with high-performance architecture, in which a server operating system is installed and programs that automatically process the information received through the network, such as database management applications, accounting processes, contact center telephony, applications developed internally by the company, etc .; so that several terminals can connect to the service simultaneously and use the functionalities through different network connections (LAN, VLAN, WAN-Internet, VPN, WLAN, Wi-Fi, etc.)
8.Database
Many web applications use a combination of MySQL as the database, PHP as the programming language, Apache as the web server, and Linux as the operating system. This combination of technologies is called LAMP (Linux, Apache, MySQL and, usually, PHP) and is one of the most used in web servers.
In a web application, such as a content manager or an online store or any other website that makes use of databases.
Conclusion
Process of a LAMP Petition
The steps performed by the client and the server of a LAMP architecture will be detailed below.
Web Client: Request to convert the name of a machine to the DNS Server. For example: www.google.es
DNS server: Reception and treatment of the request. Once the request is received, it makes the necessary queries to resolve and obtain the IP address.
DNS Server: Returns the IP address that corresponds to the Web Server to the Web browser.
Web client: Make the request for information using a URL (GET method) or a form (POST method). This request includes: the IP address of the web server, the port of the web server, URL and POST parameters (this only in the case of forms normally).
Web Server: Access Control, Analysis of the request and location of the resource.
Web server: Selection of the PHP module to interpret the chosen PHP file.
PHP module: Execution of the chosen PHP program.
PHP application: Processing of GET or POST parameters.
PHP application: Making SQL calls to the DBMS Server.
DBMS: Collection and processing of the SQL request.
SGBD: Return of the requested data.
PHP application: Processing of the data returned by the DBMS and Generation of the resulting HTML.
PHP module: Passing the resulting HTML to Apache.
Apache: Returns the HTML to the Web client.
Web Client: Presentation of the resulting HTML, CSS and related elements and execution of Javascript.
