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Cables - Internet - Services

 

I am often asked about the difference between the internet and the web.

The best analogy I have found is with the road system.

The cables = the roads

There are highways, motorways and country lanes.  Some can carry high volumes of traffic, others only little.  Different roads in different countries are constructed by different companies, but they are all connected.  You can drive from Gibraltar to Kamchatka. 

On the net, it is the same with the cables:  different companies lay telephone and other communications cables.  There are trunk lines and there is the "last km" of copper cable that brings the net to your home.  There are also "cables" that go over radio links (wireless connections, also known as WiFi, and indeed 802.x wireless is nothing else than an Ethernet via radio).

The Internet = the traffic rules

Having roads is not enough:  if traffic is to flow in an orderly manner, we need some agreements between all road users. For example, we need to agree to drive all on the right side of the road, to stop for traffic lights and many other rules.  For example, driving on the left is now restricted to a few islands (or semi-islands).  The same is true for the cables connecting the computers:  all machines need to make use of the cables in the same way.  This set of agreements is what constitutes the Internet.  The Internet is the traffic rules of the cable system.

Now we have an infrastructure that can be used:  roads (cables) and rules (internet).  On this infrastructure we can now run services.

Services

When the internet began to connect different existing networks in the mid 70s, these networks were almost exclusively academic (university) built.  They served the computing needs of scientific research by providing access to large computers from remote places.  The first need therefore was to control remote computers, and the first "service" was telnet.  However, telnet is now really restricted to remote computer maintenance and I will not go into it.  Once it was possible to use a machine remotely through the net, it was necessary to ship the data to that machine and get results back:  uploading the data and downloading the results.  The service that provided this facility and is still in widespread use is ftp: File Transfer Protocol.

You can think of it as trucks moving goods around on the roads.

As soon as this worked well, remote users wanted to communicate with the computer operators of the remote machine.  They wanted to tell them things and leave messages.  The next popular services, also still in widespread use, were e-mail and chat.

Things remained quiet for a long time, until in the 80s people began to use the computer for writing documents.  These documents needed to be consulted by many people but there was no "automatic library". You had to know on which computer a document was, log into that computer after getting a name and password from its owner, know how to operate that machine and then find the document.  The web was the answer to the problem of publishing documents without the need of any computing manipulation.

The web can be considered as a parcel delivery service on the internet.  Today there are many other services.  With more and more personal machines and personal storage on-line, there are now also peer-to-peer services, the equivalent of personal cars on the roads.

Three layers

Repeat:

  1. the cable system is like the roads, connecting machines;
  2. the internet is like the traffic rules, allowing orderly use;
  3. the web and other facilities are services on top of the infrastructure of cables and internet.

Conclusions

It follows from this that the internet has no content in itself.  Content is in web servers, e-mails, downloaded files and so on.

It also follows that there are other applications than web browsers that use the internet.  The most well-known are chat and instant messaging programs, and e-mail programs.

People who send their e-mail by opening a web browser and connecting to a web interface are not really using e-mail, they are just looking at a site that presents their e-mail to them on a web page.  Real use of e-mail is through programs like Eudora, Mail, Outlook, Thunderbird etc.

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next planned revision: 2009-01