Lab 2: Networks and the Internet
The Naming
We are going to explore an interesting, yet not very known part of the Internet: The naming scheme.
In the Internet, all computers identify themselves with numbers. These numbers are called the IP numbers (IP stands for "Internet Protocol").
Let's consider an analogy. When you want to talk with one of your friends, you pick your phone and dial a phone number. In this case, you associate the phone number to your friend's name, let's say, Andrew Smith.
In the same way, all the computers that access the Internet in the world have a number that works pretty much like their phone number. These numbers are the IP numbers.
Below are some examples of IP numbers.
64.233.167.104
64.70.45.46
129.120.209.31
IP numbers always consist of four numbers, separated by dots, with one byte allocated to each number. As a result, the minimum value is 0 and the maximum is 255 in any of the segments.
Problem 1: By this rule, determine which of the following IP's are valid, and which are not:
1.1.1.1
0.265.1.2
31.2.33.98
123321.232
Although computers deal with numbers very easily, people remember names more easily. Modern cell phones, for example, allow you to store telephone numbers and associate them with the names of the people you know. In a similar fashion, the Internet uses a naming scheme that associates IP numbers with names that are easier to remember. The following are examples:
68.142.197.86 --> Yahoo www.yahoo.com
205.188.98.2 --> AOL www.aol.com
Problem 2: Determine the Domain name associated with the following IP's. HINT: Put the number directly on the web browser.
64.233.167.104
216.74.180.189
129.120.209.31
Let's continue with our telephone analogy and consider what can happen when several computers share an IP address. Say, for example, that several people live together and share a phone, as in a family house. When the phone rings, someone in the house has to answer it. If the call is not for that individual, generally the one who answered will have to call another person, or inform the caller that the other person is not there.
In the similar way, a group of computers on a local network can share the same IP number. This IP number, which is known to computers outside of the local network, is known as a public IP. Individual computers within the local network are addressed with private IP numbers specific to each computer, and which are known only within the local network.
Of all the computers in the local network, one will assume the role of the person who always answers the calls and communicates with the others. This computer is called the ProxY. The ProxY will use the private IP's to communicate internally with the other computers in the local network.
So that Private IP's can be easily recognized, they are always assigned values within the same range of numbers. These are listed below.
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
The most common private addresses are the ones that start with 192.168, so, for example, the following IP is private:
192.168.0.1
Problem 3 (a): Determine if your IP is Private or Public. Do this by running the command ``ipconfig'' in the command prompt. You'll see an IP associated with your network card. Does this IP belongs to the range defined above as Private? Copy the output of this command too.
After this, visit the following website:
This website is going to show your public IP number in the case that you have access to the Internet.
Problem 3 (b): Are this IP numbers the same (the one that you got at the website and the one you got in the command prompt)? Are they different? HINT: Note that your computer can have more than one IP.
URL's
Everyday we use Internet browsers, like Microsoft's Internet Explorer, Firefox, Safari, Netscape or others, to access the Internet and display web pages. When we use a browser, we put an address into the address line, after which we see the Web page appear in the browser. That address is called a URL: a "Uniform Resource Locator." It's also known as a "Web address."
Please type the following address into the address line of your browser, and we'll examine the different parts of the URL.
The first part of the URL, which occurs before the the sequence ``://'', defines the protocol that will be used to access that particular Internet site. The protocol basically tells the browser how to communicate with the server to get the content desired.
As an analogy, think about the protocols we use to define our own behavior. For example, we don’t conduct ourselves in classes at the university by yelling and screaming (well, maybe some of us do. :-)). Although that type of behavior would be acceptable at a football game, it would not be for a class. In a similar fashion, your browser needs to know what to do when communicating with the server.
The most commonly used protocol is "http'', which stands for “Hyper Text Transfer Protocol.†This protocol describes how your browser can get files, such as web pages (which are themselves files), images, sound, videos, etc. and display them on your computer. Every time we access and Internet site using this protocol, these files are downloaded to our computers. (Note in our example that we are using HTTP protocol to get this particular web page.)
Another common protocol is called "FTP", which stands for "File Transfer Protocol". This protocol allows your browser and the server to exchange files in both directions. The main difference, then, between FTP and HTTP is that FTP allows you to upload files, while HTTP doesn't.
Problem 4: Do some research to discover and write down two other protocols. (HINT: there is an email protocol, a local file browsing protocol, and a secure HTTP protocol, as examples. There are older protocols available too). You can get some examples using the keywords ``list Internet Protocols'' in a search engine like Google.
Domain Names
All the sites have a domain name which is composed of a name and one or more extensions. Here, the "extensions" are defined similarly to file extensions. They generally consist of a period (".") followed by three letters.
The more common extension is ".com", as in "google.com" or "microsoft.com".
Problem 5: Search in the Internet and list five other extensions and try to figure it out their associated meaning. (In the case of .com, the associate meaning is Commercial, and in the case of .name, the meaning is that this domain belongs to a person).
HINT: Generally, this list is available in some domain vendor's sites. You can try searching in Google for ``buy domain name'' for example.
Problem 6: List the extensions of some other countries: Germany, Japan, Italy and Bolivia.
HINT: Search in Google for a governmental web site of this countries. If you cannot find any, you can also try visiting the CIA's information page of this countries. The Internet code is generally listed there.
The computers read generally the Internet Addresses in the opposite direction as you do. So for example, when you input an Internet Address that ends in ``co.uk'' , like www.bbc.co.uk, to determine where to find the Server of this Web page, the computers read the address in the opposite direction: uk.co.bbc.www. Then, they refer first to a domain authoritative server for ``uk'' which should be in England, and this Server or group of Servers point where to go to get the next part, the ``co'', and so on. As you can see, the least important part is the ending ``www'' which is just an informative part, and most of the servers use it to show that this is a Web Site.
Problem 7: Visit the following group of web pages, and for each group, write down if the web page is the same or is different.
(a) http://www.unt.edu AND http://unt.edu NOTE: The main image is generated randomically, so, don't take that parameter into account to say if the web page is different or not.
(b) http://www.cs.unt.edu AND http://cs.unt.edu
(c) http://www.unete.com.bo AND http://unete.com.bo
Turn this homework by email or upload the homework as usual