The Internet and Cloud

A server provides services over a network. A client is a device or program that requests and uses those services. These names describe their roles in the communication: the client makes a request, and the server responds.

A web server stores website resources, including web page files. When you visit a website, your browser acts as a client: it requests the resources from the web server, receives them and displays the page. One server can respond to requests from many clients.

A file server provides a different service: storing files and allowing clients to retrieve them. For example, a school file server can let a pupil access their saved work from different school computers, provided they have permission. The work is stored on the server, not only on the particular computer they used to create it.

Hosting means storing websites, files or other content on a server so that clients can access them. Hosting a website therefore involves making its resources available through a web server. Reliable, secure servers matter because many users may depend on access to the hosted content.

DNS connects a memorable name to a numerical address

People find names easier to remember than numbers. A browser, however, needs the web server's IP address to contact it. A Domain Name Service (DNS) connects these two forms of address by looking up a domain name and returning its corresponding IP address.

DNS is not one computer containing the whole Internet's address book. It is made up of multiple Domain Name Servers, which together provide the lookup service.

A URL is the address of a resource. In the URL https://example.org/news, example.org is the domain name and /news identifies the requested resource. When describing DNS as converting a URL to an IP address, it is the domain-name part that is looked up, not the page's path.

A simplified sequence for opening a web page is:

1. The user types or selects a URL in their browser.
2. The client sends a lookup request to a Domain Name Server for the domain name.
3. DNS finds the corresponding IP address and returns it to the client.
4. The client uses that IP address to contact the web server and request the page's resources.
5. The web server sends the resources back, and the browser displays the page.

DNS provides the address; the web server provides the website resources. Keeping those jobs separate explains why knowing a website's name is enough to begin a request without memorising its IP address.

Cloud services run on remote servers

The Cloud is remote service provision using servers accessed over the Internet. The storage or processing takes place on the provider's servers rather than only on the user's own device. The word does not describe a place in the sky: cloud services depend on physical computers somewhere in the world.

Cloud services include:

• Storage: files are stored remotely and can be retrieved over the Internet. Google Drive, Microsoft OneDrive and Apple iCloud are examples.
• Software: users access applications provided remotely rather than relying entirely on software installed on their own device.
• Processing: remote servers carry out computing tasks and return the results to the client.

The client–server idea therefore connects directly to the Cloud: the user's device requests a service, and the provider's remote servers supply it.

Weighing the benefits and drawbacks of the Cloud

Cloud services can make work more flexible. Users can access their files from different devices and locations, provided they have Internet access. They can also share content and collaborate, rather than keeping separate copies on individual machines.

The provider maintains the service's server hardware and typically manages security and backups. This reduces the equipment and maintenance work required by the user or organisation. Cloud storage can also offer substantial capacity without the user buying their own storage server.

These benefits have trade-offs. Access to remote services depends on an Internet connection: without one, users may be unable to retrieve files or use the software they need. Subscription charges create ongoing costs, and paying for more capacity can become expensive across a business.

Storing data with another organisation also raises security and privacy concerns. A data leak could expose confidential information, and users need to consider where their data is stored and how the provider is allowed to use it. Moving responsibility for security to a provider does not remove the risk.

For a team working from several locations, shared access and collaboration may make a cloud service attractive. For an organisation with unreliable Internet access, dependence on that connection may be a serious disadvantage. A useful judgement weighs the benefits against the needs of the particular users, rather than treating the Cloud as always better or always worse.