What happens when you type https://www.holbertonschool.com in your browser and press 'Enter'
Computers and other devices communicate using IP addresses to identify each other on the internet (10.0.0.1, 192.168.1.0, 8.8.8.8). But humans can’t remember IP addresses, so they use words. The domain name system (DNS) brings the two together and gets you to your destination.
What is DNS?
DNS stands for “Domain Name System”. It’s a system that lets you connect to websites by matching human-readable domain names (like holbertonschool.com) with the unique ID of the server where a website is stored.
Think of the DNS system as the internet’s phonebook. It lists domain names with their corresponding identifiers called IP addresses, instead of listing people’s names with their phone numbers. When a user enters a domain name like holbertonschool.com on their device, it looks up the IP address and connects them to the physical location where that website is stored.
How Does DNS Work?
The DNS directory that matches name to numbers isn’t located all in one place in some dark corner of the internet. With more than 332 million domain names listed at the end of 2017, a single directory would be very large indeed. Like the internet itself, the directory is distributed around the world, stored on domain name servers (generally referred to as DNS servers for short) that all communicate with each other on a very regular basis to provide updates and redundancies.
DNS Server
A server is a device or program dedicated to providing services to other programs, referred to as ‘clients’. DNS clients, which are built into most modern desktop and mobile operating systems, enable web browsers to interact with DNS servers. For more, see The Client-Server Model.
DNS servers and IP addresses
Each domain can correspond to more than one IP address. In fact, some sites have hundreds or more IP addresses that correspond with a single domain name. For example, the server your computer reaches for www.holbertonschool.com is likely completely different from the server that someone in another country would reach by typing the same site name into their browser.
Another reason for the distributed nature of the directory is the amount of time it would take for you to get a response when you were looking for a site if there was only one location for the directory, shared among the millions, probably billions, of people also looking for information at the same time. That’s one long line to use the phone book.
The Client-Server Model.
The Client-server model is a distributed application structure that partitions task or workload between the providers of a resource or service, called servers, and service requesters called clients. In the client-server architecture, when the client computer sends a request for data to the server through the internet, the server accepts the requested process and deliver the data packets requested back to the client. Clients do not share any of their resources. Examples of Client-Server Model are Email, World Wide Web, etc.
How the Client-Server Model works ?
In this article we are going to take a dive into the Client-Server model and have a look at how the Internet works via, web browsers. This article will help us in having a solid foundation of the WEB and help in working with WEB technologies with ease.
- Client: When we talk the word Client, it mean to talk of a person or an organization using a particular service. Similarly in the digital world a Client is a computer (Host) i.e. capable of receiving information or using a particular service from the service providers (Servers).
- Servers: Similarly, when we talk the word Servers, It mean a person or medium that serves something. Similarly in this digital world a Server is a remote computer which provides information (data) or access to particular services.
What is Firewall
A firewall is a network security device that monitors incoming and outgoing network traffic and decides whether to allow or block specific traffic based on a defined set of security rules.
Firewalls have been a first line of defense in network security for over 25 years. They establish a barrier between secured and controlled internal networks that can be trusted and untrusted outside networks, such as the Internet.
A firewall can be hardware, software, or both.
Load Balancer
Load balancing refers to efficiently distributing incoming network traffic across a group of backend servers, also known as a server farm or server pool.
Modern high‑traffic websites must serve hundreds of thousands, if not millions, of concurrent requests from users or clients and return the correct text, images, video, or application data, all in a fast and reliable manner. To cost‑effectively scale to meet these high volumes, modern computing best practice generally requires adding more servers.
A load balancer acts as the “traffic cop” sitting in front of your servers and routing client requests across all servers capable of fulfilling those requests in a manner that maximizes speed and capacity utilization and ensures that no one server is overworked, which could degrade performance. If a single server goes down, the load balancer redirects traffic to the remaining online servers. When a new server is added to the server group, the load balancer automatically starts to send requests to it.
In this manner, a load balancer performs the following functions:
- Distributes client requests or network load efficiently across multiple servers
- Ensures high availability and reliability by sending requests only to servers that are online
- Provides the flexibility to add or subtract servers as demand dictates
Web Server
A web server‘s fundamental job is to accept and fulfill requests from clients for static content from a website (HTML pages, files, images, video, and so on). The client is almost always a browser or mobile application and the request takes the form of a Hypertext Transfer Protocol (HTTP) message, as does the web server’s response.
Application Server
An application server’s fundamental job is to provide its clients with access to what is commonly called business logic, which generates dynamic content; that is, it’s code that transforms data to provide the specialized functionality offered by a business, service, or application. An application server’s clients are often applications themselves, and can include web servers and other application servers. Communication between the application server and its clients might take the form of HTTP messages, but that is not required as it is for communication between web servers and their clients. Many other protocols are popular, including the variants of CGI.
How Do Application Servers and Web Servers Work Together?
In a typical deployment, a website that provides both static and dynamically generated content runs web servers for the static content and application servers to generate content dynamically. A reverse proxy and load balancer sit in front of one or more web servers and one or more web application servers to route traffic to the appropriate server, first based on the type of content requested and then based on the configured load-balancing algorithm. Most load balancer programs are also reverse proxy servers, which simplifies web application server architecture.
Database Server
Database servers are high-powered computers that store and manage data stored on a server for a network of users and devices. The terms database servers, database management systems (DBMS), and relational DBMS (RDBMS) get used interchangeably, but RDMBS is the most often implemented type of database management. Collectively, database server solutions offer central data management, security, controls for access and permissions, and an interactive repository for a network of users.
Conclusion
A web stack has many layers, and we touched just the surface of it. When we type a URL in a browser, it takes only microseconds for all the agents we talked about to form a response and serve it to the client. Even knowing what is happening behind the curtain, it is still pretty magical to see it happening before our eyes.