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How the Internet actually works

Author: admin

To most people, the Internet is the place to which everyone plugs in their computer and views webpages and sends email. Thats a very humancentric viewpoint, but if were to truly understand the Internet, we need to be more exact:

The Internet is THE large global computer network that people connect to bydefault, by virtue of the fact that its the largest. And, like any computer network, there are conventions that allow it to work.
This is all it is really a very big computer network. However, this article will go beyond explaining just the Internet, as it will also explain the World Wide Web. Most people dont know the difference between the Internet and Web, but really its quite simple: the Internet is a computer network, and the Web is a system of publishing (of websites) for it.
Computer networks
And, whats a computer network? A computer network is just two or more of computers connected together such that they may send messages between each other. On larger networks computers are connected together in complex arrangements, where some intermediary computers have more than one connection to other computers, such that every computer can reach any other computer in the network via paths through some of those intermediary computers.
Computers arent the only things that use networks the road and rail networks are very similar to computer networks, just those networks transport people instead of information.
Trains on a rail network operate on a certain kind of track such a convention is needed, because otherwise the network could not effectively work. ikewise, roads are designed to suit vehicles that match a kind of pattern robust vehicles of a certain size range that travel within a certain reasonable speed range. Computers in a network have conventions too, and we usually call these conventions protocols.
There are many kinds of popular computer network today. The most conventional by far is the socalled Ethernet network that physically connects computers together in homes, schools and offices. However, WiFi is becoming increasingly popular for connecting together devices so that cables arent required at all.
Connecting to the Internet
When you connect to the Internet, youre using networking technology, but things are usually a lot muddier. Theres an apt phrase, "Rome wasnt built in a day" because neither was the Internet. The only reason the Internet could spring up so quickly and cheaply for people was because another kind of network already existed throughout the world the phone network!
The preexistence of the phone network provided a medium for ordinary computers in ordinary peoples homes to be connected onto the great hightech military and research network that had been developed in years before. It just required some technological mastery in the form of modems. Modems allow phone lines to be turned into a mininetwork connection between a home and a special company (an ISP) that already is connected up to the Internet. Its like a bridge joining up the road networks on an island and the mainland the road networks become one, due to a special kind of connection between them.
Fast Internet connections that are done via (A)DS and Cable are no different to phone line connections really theres still a joining process of some kind going on behind the scenes. As Arthur C. Clarke once said, any sufficiently advanced technology is indistinguishable from magic.
The Internet
The really amazing about the Internet isnt the technology. Weve actually had big Internetlike computer networks before, and The Internet existed long before normal people knew the term. The amazing thing is that such a massive computer network could exist without being built or governed in any kind of seriously organised way. The only organisation that really has a grip on the core computer network of the Internet is a USgovernmentbacked nonprofit company called ICANN, but nobody could claim they controlled the Internet, as their mandate and activities are extremely limited.
The Internet is a testament both simultaneously due to the way technologists cooperated and by the way entrepreneurs took up the task, unmanaged, to use the conventions of the technologists to hook up regular people and businesses. The Internet didnt develop on the Microsoft Windows operating system Internet technology was built around much older technical operating systems; nevertheless, the technology could be applied to ordinary computers by simply building support for the necessary networking conventions on top of Windows. It was never planned, but good foundations and a lack of bottlenecks (such as controlling bodies) often lead to unforeseen great rises like the telephone network before, or even the worldwide spread of human population and society.
What I have described so far is probably not the Internet as you or most would see it. Its unlikely you see the Internet as a democratic and uniform computer network, and to an extent, it isnt. The reason for this is that I have only explained the foundations of the system so far, and this foundation operates below the level youd normally be aware of. On the lowest level you would be aware of, the Internet is actually more like a situation between a getter and a giver theres something you want from the Internet, so you connect up and get it. Even when you send an email, youre getting the service of email delivery.
Being a computer network, the Internet consists of computers however, not all computers on the Internet are created equal. Some computers are there to provide services, and some are there to consume those services. We call the providing computers servers and the consuming computers clients. At the theoretical level, the computers have equal status on the network, but servers are much better connected than clients and are generally put in place by companies providing some kind of commercial service. You dont pay to view a web site, but somebody pays for the server the website is located on usually the owner of the web site pays a web host (a commercial company who owns the server).
Making contact
Ive established how the Internet is a computer network: now I will explain how two computers that could be on other sides of the world can send messages to each other.
Imagine you were writing a letter and needed to send it to someone. If you just wrote a name on the front, it would never arrive, unless perhaps you lived in a small village. A name is rarely specific enough. Therefore, as we all know, we use addresses to contact someone, often using: the name, the house number, the road name, the town name, the county name, and sometimes, the country name. This allows sending of messages on another kind of network the postal network. When you send a letter, typically it will be passed between postal sorting offices starting from the sorting office nearest to the origin, then up to increasingly large sorting offices until its handled by a sorting office covering regions for both the origin and the destination, then down to increasingly small sorting offices until its at the sorting office nearest the destination and then its delivered.
In our postal situation, there are two key factors at work a form of addressing that homes in on the destination location, and a form of message delivery that broadens out then narrows in. Computers are more organised, but they actually effectively do exactly the same thing.
Each computer on the Internet is given an address (IP address), and this homes in on their location. The homing in isnt done strictly geographically, rather in terms of the connectionrelationship between the smaller computer networks within the Internet. For the real world, being a neighbour is geographical, but on a computer network, being a neighbour is having a direct network connection.
ike the postal network with its sorting offices, computer networks usually have connections to a few other computer networks. A computer network will send the message to a larger network (a network that is more likely to recognise at least some part of the address). This process of broadening out continues until the message is being handled by a network that is over the destination, and then the narrowing in process will occur.
An example IP address is 69.60.115.116. They are just series of digit groups where the digit groups towards the right are increasingly local. Each digit group is a number between 0 and 255. This is just an approximation, but you could think of this address meaning:
  • A computer 116
  • in a small neighbourhood 115
  • in a larger neighbourhood 60
  • controlled by an ISP 69
  • (on the Internet)
The small neighbourhood, the larger neighbourhood, the ISP, and the Internet, could all be consider computer networks in their own right. Therefore, for a message to the same larger neighbourhood, the message would be passed up towards one of those intermediary computers in the larger neighbourhood and then back down to the correct smaller neighbourhood, and then to the correct computer.
Getting the message across
Now that we are able to deliver messages the hard part is over. All we need to do is to put stuff in our messages in a certain way such that it makes sense at the other end.
etters we send in the real world always have stuff in common they are written on paper and in a language understood by both sender and receiver. Ive discussed before how conventions are important for networks to operate, and this important concept remains true for our messages.
All parts of the Internet transfer messages written in things called Packets, and the layout and contents of those packets are done according to the Internet Protocol (IP). You dont need to know these terms, but you do need to know that these simple messages are error prone and simplistic.
You can think of packets as the Internet equivalence of a sentence for an ongoing conversation, there would be many of them sent in both directions of communication.
Getting the true message across
All those whove played Chinese whispers will know how messed up (corrupted) messages can get when they are sent between many agents to get from their origin to their destination. Computer networks arent as bad as that, but things do go wrong, and its necessary to be able to automatically detect and correct problems when they do.
Imagine youre trying to correct spelling errors in a letter. Its usually easy to do because there are far fewer words than there are possible wordlength combinations of letters. You can see when letter combinations dont spell out words (errors), and then easily guess what the correct word should have been.
It reely does worke.
Errors in messages on the Internet are corrected in a very similar way. The messages that are sent are simply made longer than they need to be, and the extra space is used to "sum up" the message so to speak if the "summing up" doesnt match the message an error has been found and the message will need to be resent.
In actual fact, it is often possible to logically estimate with reasonable accuracy what was wrong with a message without requiring resending.
Error detection and correction can never be perfect, as the message and "summing up" part could be coincidently messedup so that they falsely indicate nothing went wrong. The theory is based off storing a big enough "summing up" part so that this unfortunate possibility is so unlikely that it can be safely ignored.
Reliable message transfer on the Internet is done via TCP. You may have heard the term TCP/IP: this is just the normal combination of IP and TCP, and is used for almost all Internet communication. IP is fundamental to the Internet, but TCP is not there are in fact other protocols that may be used that I wont be covering.
Names, not numbers
When most people think of an Internet Address they think of something like www.ocportal.com rather than 69.60.115.116. People relate to names with greater ease than numbers, so special computers that humans need to access are typically assigned names (domain names) using a system known as DNS (the domain name system).
All Internet communication is still done using IP addresses (recall 69.60.115.116 is an IP address). The domain names are therefore translated to IP addresses behind the scenes, before the main communication starts.
At the core, the process of looking up a domain name is quite simple its a process of homing in by moving leftwards through the name, following an interrogation path. This is best shown by example www.ocportal.com would be looked up as follows:
  • Every computer on the Internet knows how to contact the computers (the root DNS servers) responsible for things like com, org, net and uk. There are a few such computers and one is contacted at random. The DNS server computer is asked if they know www.ocportal.com and will respond saying they know which server computer is responsible for com.
  • The com server computer is asked it knows www.ocportal.com and will respond saying they know which server computer is responsible for ocportal.com.
  • The ocportal.com server computer is asked if it knows www.ocportal.com and will respond saying that it knows the corresponding server computer to be 69.60.115.116.
Note that there is a difference between a server computer being responsible for a domain name and the domain name actually corresponding to that computer. For example, the ocportal.com responsible DNS server might not necessarily be the same server as ocportal.com itself.
As certain domain names, or parts of domain names, are very commonly used, computers will remember results to avoid doing a full interrogation for every name they need to lookup. In fact, I have simplified the process considerably in my example because the lookingup computer does not actually perform the full search itself. If all computers on the Internet did full searches it would overload the root DNS servers, as well as the DNS servers responsible for names like com. Instead, the looking up computer would ask its own special local DNS server, which might remember a result of a partial result, or might solicit help (full, or partial) from its own local DNS server, and so on until, in a worst case scenario, the process has to be completed in full.
Domain names are allocated by the person wanting them registering the domain name with an agent (a registrar) of the organisation responsible for the furthest righthand part of the domain name. At the time of writing a company named VeriSign (of which Network Solutions is a subsidiary) is responsible for things like com and net. There are an uncountable number of registrars operating for VeriSign, and most domain purchasers are likely not aware of the chain of responsibility present instead, they just get the domains they want from the agent, and deal solely with that agent and their web host (who are often the same company). Domains are never purchased, but rather rented and exclusively renewable for a period a bit longer than the rental period.
Meaningful dialogue
Ive fully covered the essence of how messages are delivered over the Internet, but so far these messages are completely raw and meaningless. Before meaningful communication can occur we need to layer on yet another protocol (recall IP and TCP protocols are already layered over our physical network).
There are many protocols that work on the communications already established, including:
  • HTTP for web pages, typically read in web browser software
  • POP3 for reading email in email software, with it stored on a users own computer
  • IMAP4 for reading email in email software, with it archived on the receiving server
  • SMTP for sending email from email software
  • FTP for uploading and downloading files (sometimes via a web browser, although using special FTP software is better)
  • ICMP for pinging, amongst other things (a ping is the Internet equivalent to shouting out a are you there)
  • MSN Messenger this is just one example of many protocols that arent really standard and shared conventions, but rather ones designed by a single software manufacturer wholly for the purposes of their own software
Im not going to go into the details of any of these protocols because its not really relevant unless you actually need to know it.
The information transferred via a protocol is usually a request for something, or a response for something requested. For example, with HTTP, a client computer requests a certain web page from a server via HTTP and then the web server, basically, responds with the file embedded within HTTP.
Each of these protocols operates on more or more socalled ports, and it is these ports that allow the computers to know which protocol to use. For example, a web server (special computer software running on a server computer that serves out web pages) uses a port of number 80, and hence when the server receives messages on that port it passes them to the web server software which naturally knows that theyll be written in HTTP.
For a client computer its simpler it knows that a response to a message it sent will be in the same protocol it initially used. When the messages are sent back and forth the server computer and client computer typically set up a socalled stream (a marked conversation) between them. They are then able to associate messages to the stream according to their origin address and port number.
The World Wide Web
Ive explained how the Internet works, but not yet how the World Wide Web (the web) works. The web is the publishing system that most people dont realise is distinguishable from the Internet itself.
The Internet uses IP addresses (often found via domain names) to identify resources, but the web has to have something more sophisticated as it would be silly if every single page on the Internet had to have its own domain name. The web uses URs (uniform resource locators), and Im sure you know about these as nowadays they are printed all over the place in the real world (albeit, usually only in shorthand).
A typical UR looks like this:
:///
For example:
http://www.ocportal.com/index.php
That said thats not really a full UR, because occasionally URs can be much more complex. For example:
://:@:/
You can ignore the more complex example, because its not really relevant for the purposes of this article.
HTTP is the core protocol for the web. This is why URs usually start http://. Web browsers almost always also support FTP, which is why some URs may start ftp://.
Typically the resource identifier is simply a file on the server computer. For example, mywebsite/index.html would be a file on the server computer of the same path, stored underneath a special directory. On Windows the "" symbol is used to write out directory names, but as the web wasnt invented for Windows, the convention of the older operating systems is used.
We now have three kinds of Internet Address, in order of increasing sophistication:
  • IP addresses
  • Domain names
  • URs
If a UR were put into web browser software by a prospective reader then the web browser would send out an appropriate request (usually, with the HTTP protocol being appropriate) to the server computer identified by the UR. The server computer would then respond and typically the web browser would end up with a file. The web browser would then interpret the file for display, much like any software running on a computer would interpret the files it understands. For the HTTP protocol, the web browser knows what to interpret the file as because the HTTP protocol uses something called a MIME type to identify each kind of resource the server can send out. If the web server computer is just sending out an ondisk file then the web server computer works out the MIME type from the file extension (such as .html) of the file.
An HTM file is the kind of file that defines a web page. Its written in plain text, and basically mixes information showing show to display a document along with the document itself. If youre curious, try using the "View page source" function of your web browser when viewing a web page, and youll see a mix of portions of normal human text and short text between < and > symbols. The former is the document contents and the latter are the display instructions.
In newer versions of HTM theres a split between structuring a document and displaying a structure in this case, another special technology named CSS is added to the mix.
Ive explained how typical web pages are just files on the disk of a server computer. Increasingly, things are slightly less direct. When you visit something like eBay, your webmail, or an ocPortalpowered website, you arent just reading files. Youre actually interacting with computer software, and the web pages you receive are generated anew by that software every time a request is made. These kinds of systems are known as web applications and are increasingly replacing the need to install software on your own computer (because its so much easier just to use a web browser to access a web application on a server computer).


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