Basic Concept of Web Technology

Web Server Definition

The server is a computer agent that is normally active 24 hours a day, 7 days a week (or simply 24/7), listening for queries from any client who make a request.

Domain Name Registration Process

1. Registrant searches for available domain, typically using web portal of Registrar or Reseller.
2. Registrar queries the relevant TLD Registry Operator to see if requested domain is available.
3. If domain is available, then Registrant will pay for the domain and provide the necessary WHOIS information, such as contact name, mailing address, and DNS server addresses.
4. Registrar pushes WHOIS information about new domain to TLD Registry Operator.
5. Registry operator adds WHOIS information for new domain to its authoritative list.
6. Registry operator will push DNS information for new domain out to its name servers for the TLD.

URL Example and Components

Example URL: https://www.example.com

• Protocol: HTTPS
• Domain: www.example.com
• Port: 443
• Path: None (root directory)

Benefits of DNS

DNS translates domain names to IP addresses, allowing users to access websites using easy-to-remember names instead of numerical IP addresses.

Domain Name Address Resolution Process

1. Client makes request for domain.
2. Client computer checks local DNS Cache for the IP addresses of the requested domain.
3. If requested domain is not in the local cache, the computer requests the IP address for the domain from its primary DNS server (typically provided by the ISP; a client computer might instead be configured to use an public DNS provided by companies such as Google).
4. If the primary DNS Server doesn’t have a record for the requested domain in its cache, it sends out the request to the Root Name Server.
5. The Root Name Server returns the address of the relevant Top-Level Domain (TLD) Server.
6. The DNS Server requests the DNS record information from the provided TLD Server.
7. The TLD Name Server returns with the IP addresses of the Authoritative DNS Servers for the requested domain.
8. The DNS Server requests the IP address for the originally requested domain from one of the site’s Authoritative DNS Servers. When it receives it, it will save it in its own DNS Cache.
9. The DNS Server returns the IP address of the requested domain.
10. The client computer can finally make its request of the domain.

HTTP Response Codes

• 200: OK
• 301: Moved Permanently
• 304: Not Modified
• 307: Temporary redirect
• 400: Bad Request
• 401: Unauthorized
• 404: Not Found
• 414: Request URI too long
• 500: Internal Server Error

Web Page Rendering Events

• Time to First Byte (TTFB)
• First Paint (FP)
• First Contentful Paint (FCP)
• First Meaningful Paint (FMP)
• Largest Contentful Paint (LCP)
• Time to Interactive (TTI)
• On Load
• Cumulative Layout Shift (CLS)

HTTP Request Methods

• GET - Requests data from a specified resource.
• POST - Submits data to be processed to a specified resource.
• PUT - Updates a specified resource.

Browser Caching

Once a webpage has been downloaded from the server, it’s possible that the user, a short time later, wants to see the same web page and refreshes the browser or re- requests the URL. Although some content might have changed (say a new blog post in the HTML), the majority of the referenced files are likely to be unchanged, so they needn’t be redownloaded.

Examples of Software

• Web Server Software: Apache HTTP Server, Nginx
• Database Software: MySQL, PostgreSQL
• Scripting Software: PHP, Python