What is the Internet? What about the Internet?

TCP/IP, Packets, and Routers

The Internet is a collection of networks that presently use the TCP/IP protocol suite and operate as one cooperative, virtual network. It has recently grown rapidly across much of the world and is presently found in almost every country.

For the purpose of this example, let's assume that you want to send a file to a friend who lives on the opposite side of the country. You select the file that your friend wants and you send it. Transmission Control Protocol / Internet Protocol (TCP/IP) prepares the data to be sent and received. TCP/IP ensures that a Macintosh network can exchange data with a Windows, or a Unix network, and vice-versa. The file that you are sending does not travel to your friend's computer directly, or even in a single continuous stream. The file you are sending gets broken up into separate data packets. The Internet Protocol side of TCP/IP labels each packet with the unique Internet address, or IP address of your friend's computer. Since these packets will travel separate routes, some arriving sooner than others, the Transmission Control Protocol side of TCP/IP assigns a sequence number to each of packets. These sequence numbers will tell the TCP/IP in your friend's computer how to reassemble the packets once he receives them. Amazingly, the complicated process of TCP/IP takes place in a matter of milliseconds.

The packets travel from one "router" to the next. Each router reads the destination IP address of the packet and decides which path will be the fastest. Since the traffic on these paths is constantly changing, each packet may be sent a different way. Each point on the internet that the router uses to send data (step by step in a connect-the-dots fashion) has a variable amount of traffic and variable connection speed, limited primarily by the hardware in place and the sheer volume of packets traveling through that particular location. Once these packets arrive at the destination, they are then reassembled in the proper sequence to allow the file to arrive in its original form. This happens every time you visit an internet Web page: data is transferred to your system via TCP/IP, with varying degrees of performance.

IPs, Domain Names, and Name Servers

Every single location (machine, router, name server, hosting account, etc.) on the Internet has at least one unique IP address, which is most commonly represented as four numbers joined by periods (.), like 199.227.124.197. These function just like street addresses for the internet. There are literally thousands of different possible IP addresses. These addresses represent the exact location of a particular site on the internet, and serve to guide any other user to that location. Each location on the internet might also have one or more domain names that refer to the IP address.

For example, the domain name TCPIPHost.com refers to our location on the internet, which is currently 216.191.22.143. Since it would be impossible for anyone to remember which domain names were matched up to each IP address, the internet has large computers, called name servers, that serve as translators. These name servers can look up any domain name and resolve it into the IP address to which it refers. Whenever a user refers to TCPIPHost.com, or any other domain name, that information is sent to a name server (normally at the Internet Service Provider of the user), and the name server returns the matching IP address so that the site can be visited. All of this happens behind the scenes.

IP addresses and domain names aren't assigned arbitrarily - that would lead to unbelievable confusion. An application must be filed with the InterNIC for each domain name needed, and each domain name must have a matching IP address somewhere on the internet.

The Process of Surfing

So the basic process of "surfing the web" is as follows: you connect to an Internet Service Provider (ISP) using the TCP/IP protocol. The ISP has one or more name servers available to you for domain information. You type a domain name (such as TCPIPHost.com) into your Web browser, or click on a hyperlink from another Web page, and that request is sent at the speed of your modem (normally quite slow, even with the fastest of today's modems) over to your ISP's name servers. Assuming the domain name is properly registered with InterNIC, the domain is resolved into an IP address that specifies your true destination on the internet. The request travels through many routers at varying speeds and pathways, until the request arrives at the destination server. If the Web server is up and running correctly, then the destination begins to send information back to your computer in the same manner, until the page is visible on your Web browser. This complex process is normally transparent to you, if all goes well.

Just as the slowest man in a convoy limits the speed of the entire group, so does the slowest link between two internet locations. You will only be able to transfer data at the speed of the slowest link on the internet. This is why modems continue to get faster and faster. But even so, a user with a fast T1 connection can still suffer from internet slowdowns, or lags, due to the fact that one of the links between the two locations on the internet is running at a very slow connection speed. This is why everyone, no matter how fast their connection, can still suffer from the unpredictable and often frustrating ups and downs all over the internet.

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