Internet and It's Applications

Most people know the Internet through its applications:

the World Wide Web,email,social media, streaming music or movies, videoconferencing, instant messaging, file sharing to name just a few examples.

That is to say, we interact with the internet as users of the network.

Network Applications:

The World Wide Web is the internet application that catapulted the internet from a somewhat obscure tool used mostly by scientist and engineers to the mainstream phenomenon that it is today.

The Web itself has become such a powerful platform that many people confuse it with Internet, and it's a bit of a stretch to say that the Web is a single application.

In its basic form, the Web presents an intuitively simple interface. Users view pages full of textual and graphical objects and click on objects that they want to learn more about, and a corresponding new page appears. Most people are also aware that just under the covers each selectable object on a page is bound to an identifier for the next page or object to be viewed.

This identifier, called a Uniform Resource Locator (URL), provides a way of identifying all the possible objects can be viewed from your web browser.

https://www.<sitename>.domain/<sitepage>/edit

Is the URL for a page providing information about one of this book’s authors:

the string http indicates that the Hypertext Transfer Protocol (HTTP) should be used to download the page, www.canva.com is the name of the machine that serves the page and /shashnkjain/note.html uniquely identifies home page at this site.

What web users are not aware of, however, is that by clicking on just one such URL over a dozen messages may be exchanged over the Internet, and many more than that if the web page is complicated with lot of embedded objects. This message exchange includes up to six messages to translate the server name (www.canva.com) into its internet protocol (IP) address (162.255.79.68), three messages to set up a transmission control Protocol (TCP) connection between your browser and this server,Four messages to tear down the TCP connection.

Another widespread application class of the internet is the delivery of “streaming” audio and video. Services such as video on demand and Internet radio use this technology. While we frequently start at a website to initiate a streaming session, the delivery of audio and video has some important differences from fetching a simple web page of text and images. For example you often don’t want to download an entire video file---a process that might take few minutes---before watching the first scene. Streaming audio and video implies a more timely transfer of messages from sender to receiver, and the receiver displays the video or plays the audio pretty much as it arrives.

Note that the difference between streaming applications and the more traditional delivery of text, graphics and images is that humans consume audio and video stream in a continuous manner, and discontinuity --- in the form of skipped sounds or stalled video ---is not acceptable. By contrast, a regular (non-streaming) page can be delivered and read in bits and pieces. This difference affects how the network supports these different classes of application

Although they are just two examples, downloading pages from the web and participating in a video conference demonstrate the diversity of applications that can be built on top of the internet and hint at the complexity of the internet design.