Computer Networks

Tutorial #21

1. What is a shopping cart application?

2. What is meant by state maintenance in the context of a shopping cart application? What are the two technologies which can be ued to implement state maintenance?

3. Typically, what information do you think would be contained within a hidden field or cookie?

4. What are some of the advantages of cookies over hidden fields? What disadvantages do they have?

5. Some time ago, my copy of Netscape presented me with the following message:

   The certificate that the site 'www.unitedmedia.com' has presented does not contain the correct site name. It is possible, though unlikely, that someone may be trying to intercept your communication with this site. If you suspect the certificate shown below does not belong to the site you are connecting with, please cancel the connection and notify the site administrator.

   Here is the Certificate that is being presented:

   Certificate for:	United Media
   Signed by:	RSA Data Security, Inc.
   Encryption:	Export Grade (RC4-Export with 40-bit secret key)

   What's going on here? How could it happen?

6. (Discussion question) There's obviously lots of potential for using Java to build a shopping cart application which runs on the client (browser) instead of using FORMS and CGIs. Is this a good idea?

Practical exercises:

• Visit some commercial Web sites, pretend you're going to buy something (maybe actually buy something!) and discover whether they're using hidden fields or cookies to maintain state.

• Turn on the "Notify Me About Cookies" option (or whatever it is in your particular browser) and be amazed at the cookies that are being sent to you!

• Use the small segments of Perl code given in the lecture to set and read cookies.