Changes

Whether you are accessing the Internet from your home computer or from a mobile phone on a moving train, the principle remains the same: your device connects to the local ISP > connects to the national provider > connects to the Internet exchange (backbone). Should you be visiting a website or sending an email to a server located in a different country (quite likely) then this progression through the network hierarachy hierarchy is repeated on the other end side of the communications channel too.

[[File:InternetConnections.jpg|900px|InternetConnections]]

'' '''Note:''' The Internet is a packet-switching network. This means that your email, for example, is broken down into small individual packets which are then sent independently of each other along the many possible routes on the network that connect you to your friend's computer. These packets are then reassembled at the receiver's end to re-create your email. Important! You do not control how data travels through the Internet once you hit the send button.''

1. #View your computer's IP by visiting http://hostip.info You can also view the IP addresses associated with your favourite websites through this system.  2. #Next, go to http://whois.net/ to find out who that particular IP address is registered to.

Even though all computers connected to the Internet are assigned an IP address, we usually do not know these addresses nor do we use them when opening a website. Numbers are quite difficult to remember (how many phone numbers do you know by heart?) and for this reason we assign names as addresses for our websites (also known as a Universal Resource Locator – URL). These names and their associated IP addresses are recorded in the Domain Name System (DNS). This is akin to the Internet's telephone directory and is another critical component of Internet routing and operations. DNS is hierarchical, meaning that your computer can have its list of URLs and corresponding IPs, your ISP will have a list, the national provider will have a list and so on, right up to the root DNS servers (of which there are 13). Should your computer not have an entry for www.livejournal.com it will ask the next list up in line – the ISP's and so on. Whether browsing websites or sending email, DNS always plays a part. Below is a diagram describing how DNS is utilised utilized when you search for the LiveJournal website.

* Not knowing the LiveJournal address, you open Google naturally. Your computer doesn't know where www.google.com is and so asks the DNS server for Google's IP.* Using Google's IP you locate the search engine and punch in 'LiveJournal'. The search returns www.livejournal.com which you promptly click.* Once again, your computer has no idea where to locate www.livejournal.com and returns to the DNS server to get its IP.* Finally, using the correct IP you can access LiveJournal's website.

'''Media:''' A brief explanation how websites are located using the DNS.

Another video that discusses the regulative and technical framework behind DNS and why this is important.

The last part of the Internet's infrastructure concerns the applications we use to send and receive content on the Internet. These include your browser, email program, chat client and every other software on your computer that utilises utilizes or help you interact on the Internet. Every application has its particular language and protocols and these often affect how information is transmitted between two computers on the Internet. This usually involves a type of technical language (protocol) by which it communicates or the channel (port) it selects for communication. For example, some applications send data in a clear-text format and every computer/router that stands in-between the communicating parties can access and understand the transmitted information. Other applications take special care to ensure privacy for the communicating parties. For example, when you connect to http://google.com your browser is using the 'http' protocol on port 80. However when the website's address is preceded by the letters 'https' (https://mail.google.com) your browser begins to use the Secure Sockets Layer (SSL) protocol on port 443. The majority of this course is explaining and exploring the different ways that applications interact on the Internet, directly impacting upon your privacy, anonymity and authentication of the transmitted message.