PDF How the Internet Works

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Contents

  1. National Curriculums
  2. How the Internet Works Course
  3. Introduction
  4. How does the Internet work?

Another thing to note is that special software must be installed on the server to create a dynamic website. Whereas normal static HTML files are saved with a file extension of. PHP files for example usually have a. While the server for a dynamic website may be processing special dynamic code, it is still sending HTML to the client.

The client does not need plugins for these special file extensions because the client is still getting what looks like an HTML file. NET and Coldfusion. In the end, all of these technologies have pretty much the same capabilities, like talking to databases, validating information entered into forms, etc. It all boils down to what suits you best. We will not be covering dynamic languages any further in this course, but I have provided a list of resources here in case you want to go and read up on them:.

That is it for the behind-the-scenes tour of how the Internet works. This article really just scratches the surface of a lot of the topics covered, but it is useful as it puts them all in perspective, showing how they all relate and work together. This site is now available on github. How does the Internet work? Summary Every so often, you get offered a behind-the-scenes look at the cogs and fan belts behind the action. How do computers communicate via the Internet? Now, one thing you may not know is that web browsers actually do not use URLs to request websites from servers; they use Internet Protocol or IP addresses which function like phone numbers or postal addresses, but identify servers, rather than phones or addresses.

This is because people are better at remembering words than long strings of numbers. The system that makes this work is called DNS, which is a comprehensive automatic directory of all of the machines connected to the Internet. There are a literally millions of machines connected to the Internet, and not every DNS server has a listing for every machine online, so there is a system in place where your request will be referred on to another name server to fulfill your request, if the first one does not have the right information.

So the DNS system looks up the Apple website, finds that it is located at Your machine then sends a request to the machine at the IP address specified and waits to get a response back. If all goes well, the server sends a short message back to the client with a message saying that everything is okay see Figure 1, followed by the web page itself.

National Curriculums

This type of message is contained in an HTTP header. The page does not exist, so you will get a error returned. Try it with a few different fake page addresses and you will see a variety of different pages returned.

This is because some web developers have just left the web server to return their default error pages, and others have coded custom error pages to appear when a non-existent page is returned. This is an advanced technique that will not be covered in this course, but Stuart Colville provides a good article on it at Adding meaning to your HTTP error pages!

How the Internet Works Course

You are always accessing actual files, but sometimes the web developer has set up the web server to not display the file names in the URL — this often makes for neater, easier to remember URLs, which leads to a better experience for the user of your website. Plain text In the really early days of the Internet, before any web standards or plugins came along, the Internet was mainly just images and plain text — files with an extension of.

For example, in the screenshot below, we traced the route to howtogeek. A router contacts another router and communicates the data in the packet. The packet is just a signal on the wire. There are lots of little topics that are important to the internet we all use, and which you can read about in more detail.

For example, every device on a network has a unique, numerical IP address on that network. Data is sent to these addresses. There are both older IPv4 addresses and newer IPv6 addresses. These are the addresses that devices on the network use and speak. People use human-readable domain names like howtogeek. However, when you use domain names like these, your computer contacts its domain name system DNS server and asks for the numerical IP address for that domain.


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Think of it like a large, public address book for phone numbers. Companies and individuals who want domain names have to pay to register them. The digital side of a modem is usually connected to a serial port on a terminal server. A typical terminal server will have up to a few dozen modems connected to it.

Active Learning

The terminal server converts the data received from the modem into the format required for the rest of the IAP infrastructure. Only the network-specific portion of the data is changed; no access to the content of the data is performed. The terminal server controls the physical activity of the modem, acting as an "onramp" or Internet access point, for the IAP, collecting and submitting authentication information ID and password to a server elsewhere in the IAP complex. When data leaves the terminal server via the local network "LAN" connection, data from the active modems are interleaved as needed in the data stream and sent to the LAN.

The IP router shuttles packets from one of its input ports to one of its output ports. The ports can be the entry way to LANs, high speed dedicated circuits, or other networks facilities. Routers are "stateless," which means they route each block of data individually and do not remember how they routed previous blocks.

Routing decisions are made based on header information never on content data and controlled by a combination of configuration information and dynamic routing protocol information. The routing decisions are facilitated by packet switching. Packet switching is a technique used in data networking to lower the cost of dedicated circuits and to avoid congestion at various network nodes.

This technique involves breaking data into packets, each with its own individual address. An apt analogy is to think of a group of co-workers traveling to a meeting. All leave a common address — the office — for a common destination — the meeting. Each worker, however, can take any number of routes throughout the city to reach their destination.


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  • At any one point in time during travel, it would be nearly impossible for the boss to know the location of all the travelers. The packet also contains the information necessary to properly sequence data once it arrives at the address site. The packets can be analogized to traditional mail. The packet headers act as envelops, providing all relevant addressing information.

    At the same time, the payload content remains shielded from the details of delivery.

    Introduction

    IAPs will usually offer two or more physically diverse paths between any two points to promote reliability. In the event of the failure of a single telecommunications link, the other links can continue to carry the packets. A router can tell when a link has failed or is degraded. In such a case, or when otherwise configured to do so, a router will favor one link over another when routing packets.


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    In general, however, physically diverse paths that connect to the same distant point will be considered equivalent. Packets have an equal chance of being routed over any of the equivalent links. In fact, two consecutive packets from the same source to the same destination will often be routed over different links. Since there are many routers and many links between typical sources and destinations, the packets from a data stream can individually travel widely different paths.

    Internet providers use a variety of techniques to improve the speed and reliability of data delivery to the end user. Packet switching, as described above, is such a technique, having the possibility to improved both the speed and reliability of data delivery.

    How does the Internet work?

    Caching is another tool employed by Internet providers to improve network performance. Caching involves storing often-accessed data on special high-speed servers or on local machines for quick access. By reducing the travel distance on the Internet and thus, network traffic on the Internet, caching greatly improves access speed and the speed of data delivery to the end user.

    These services might involve electronic mail servers, usenet news servers, "chat" conference servers, DNS domain name system servers, web servers, file storage areas on FTP file transfer protocol servers, or HTTP hypertext transfer protocol proxy servers. These services will be operated on one or more general purpose computers within the IAP's complex.