Web Servers

A web server is one that provides client access using HTTP or its secure version (HTTPS).

Websites and web applications are perhaps the most useful and ubiquitous of network services
can be deployed for a huge range of functions and applications, in no way limited to the static pages of information that characterized the first websites

How it Works

HTTP is usually used to serve HTML web pages
- plain text files with coded tags describing how the document should be formatted
web browser can interpret the tags and display the text and other resources associated with the page (such as pictures or sound files)
has ability to provide hyperlinks to other related documents
features mechanisms (POST) whereby a user can submit data from the client to the server
functionality of HTTP servers is often extended by support for scripting and programmable features (web applications)

most organizations have an online presence represented by a website
- in order to run a website:
  - it must be hosted on an HTTP server connected to the Internet
Typically, an organization will lease a web server or space on a server from an ISP
- common hosting packages:
  - dedicated server
    - the ISP allocates your own private server computer
    - usually unmanaged (or comes at additional cost)
  - virtual private server (VPS)
    - ISP allocates you a virtual machine (VM) on a physical server
    - isolated from other customer instances by the hypervisor
  - cloud hosting
    - your website is run on a cloud over several hardware computers
    - allows more scalability if demand patterns change
  - shared hosting
    - your website is hosted within a private directory on a shared server
    - performance can be severely affected by other sites hosted on the server
      - because all sites are competing for the same resources
larger organizations with Internet-connected datacenters may host websites themselves
Web servers are not only used on the public Internet
- Private networks using web technologies are described as:
  - intranets (if they permit only local access)
  - or extranets (if they permit remote access)
web server platforms:
- Apache
- Microsoft Internet Information Services (IIS)
- NGINX