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Web Development Topics
It is estimated that there approximately 400 million real websites (excluding things like placeholders for websites that have not yet been constructed), and billions of individual web pages on the Internet. That raises an important issue — how do you find anything?
A similar problem exists in the real world. There are approximately 7 billion people in the world, and if the average household size is somewhere around 4, that would imply that there are somewhere around 2 billion possible postal addresses.
That last word, addresses, is the key to locating something in a vast universe like this. Basically, everything on the Internet has an address through which it can be located. More or less.
The reason for the ‘more or less’ part is that there is a little bit of sleight of hand that goes on in the world of Internet addressing, for a variety of practical reasons. We’ll deal with some of those later.
The addressing used on the Internet today consists of 4 numbers separated by dots, such as 188.8.131.52 or 254.225.132.124. This is referred to as the ‘IP address’, where IP stands for ‘Internet Protocol’.
Each of the four parts of the address is a number between 0 and 255 (256 possible values) yielding a theoretical total of just over 4 billion possible addresses, although the actual number is a little less because some of these addresses are reserved for special purposes. If you know someone’s address (actually, the address of their computer), you can use it to find them. There is a bit more to it in the real world, but that’s the core concept.
If you use the Internet at all (and you must, if you’re reading this), you know that people who are not techies almost never refer to the IP address when they access a website or send e-mail. That’s because a system was created to use more people friendly names instead of the IP address. These names, such as google.com or webbusconnect.com, are called ‘domain names’.
The way domain names are translated into IP addresses is through the use of ‘Domain Name Servers’, affectionately known as ‘DNS’. A Domain Name Server is simply a program running on a computer connected to the Internet, and it translates the domain name to the actual (IP) address you need to reach.
DNS is a distributed system, meaning that multiple computers in different locations on the Internet are involved in making it work. Your ‘registrar’ (the company you bought your domain name from, such as Network Solutions or Godaddy) maintains information on which DNS server is ‘authoritative’ for your domain. It can be a DNS server that the registrar operates, or one run by your hosting company, or anyone else for that matter. The DNS server that is authoritative for your account maintains records that lead to your actual web server or mail server. So when you type a domain name into your web browser, the DNS will help silently route your request to the right place.
Everything we’ve discussed so far assumes that you have the web address (domain or e-mail address) of whomever you are trying to reach. If you don’t know the company, person or website you’re looking for (such as when you need a plumber after your pipes explode), that presents an entirely different problem.
That’s where search services, such as Google, Yahoo and Bing (Microsoft) come in, as well as on-line directories such as Manta, dexKnows, Superpages.com and Yelp. These services allow you to find websites that you may not be familiar with either by doing searches based on keywords you enter, or by looking something up by topic. These subjects are covered in separate articles:
We mentioned earlier that there is a little further complication in Internet addressing. We are not going to explore all of those details in depth, but we will touch on a few highlights.
Today, many websites are on shared servers, which sometimes host hundreds of sites. While a single server can actually support a different IP address for each website, most don’t, because the number of available IP addresses is limited. In the case of a shared IP, the server will use a combination of IP address and domain name to route your request to the correct website.
The final topic we’ll consider is the difference between public and private IP addresses. You are typically assigned a small number of IP addresses on the public Internet by your Internet Service Provider, whereas you may have hundreds of IP’s on an internal network. The IP’s on the internal network are not visible outside your local network, eliminating conflicts with others who may use the same addresses internally. Your router (the device that connects your network to the Internet) translates the public (outside) addresses of machines on your local network to the addresses those machines use on the internal network, and prohibits access to machines that should not be available from the outside.