Open a web browser and connect to www.google.com.

42 | Lesson 2 3. Now, try the following commands:

a. netstat the original command; shows basic connections

b. netstat –a shows in depth TCP and UDP connections

c. netstat –an shows TCP and UDP connections numerically

DEFINE THE SESSION LAYER GET READY. Every time you connect to a Web site, a mail server, or any other computer on your network or another network, your computer is starting a session with that remote com- puter. Each time you log on or log off of a network, the session layer is involved. Let’s explore this further by carrying out the following actions:

1. Make several connections to other computers. For example:

a. Connect to www.microsoft.com.

b. Connect to a mail account that you have with Gmail, Yahoo, or another such

service.

c. Connect to a network share if available.

d. Connect to an FTP server if available.

2. Go back to the command prompt and run the netstat –a command; then, in a second

command prompt, run the netstat –an command. Analyze the various sessions that you have created. Compare the results of both commands. See whether you can catch the names in one command prompt and their corresponding IP addresses in the other command prompt. Note the “State” of the connections or sessions: Established, Close_wait, and so on.

3. Now, log on to and off of several networks:

a. Log off or on to your Microsoft network if you are connected to one.

b. Log on to a Web site like Amazon or another site that you have membership

with. All of these steps are completed as part of the session layer. The session layer is also in charge of the termination of sessions. You will notice that after a certain period of no activity, web sessions change their state from Established to either Time wait, or closed, or something similar. Log off all of your sessions now, and close any connections to any Web sites or other computers you have connected to. Finally, log off the computer and log back on. DEFINE THE PRESENTATION LAYER GET READY. The presentation layer will change how data is presented. This could include code conversion from one computer system to another that both run TCPIP, or it could be encryption or compression. This layer also comes into play when you connect to a mapped network drive known as a redirector. Carry out the following actions to see several examples of how information is modified before being sent across the network:

1. Access Windows Explorer on a Windows client computer.

2. Create a simple text file with some basic text, and save it to a test folder.

3. Right-click the text file and select Properties.

4. In the Properties window, click the Advanced button.

5. Select the Encrypt contents to secure data checkbox.

6. Click OK. The file should now be displayed in blue. From now on, if the file is sent

across the network, the presentation layer will come into effect due to the encryption.

7. Open a web browser and connect to https:www.paypal.com. Note the https at the

beginning of PayPal’s address, which is short for HyperText Transfer Protocol Secure.