Computer Networks

Tutorial #5

1. This question is rather basic, but concerns a topic about which some people have indicated a worrying level of confusion. In this lecture, and at various other times, the concept of 8 bit data has been mentioned. The alternative to 8 bit data is usually (so called) printable ASCII text. What do these terms mean? You should ensure that you really do understand the answer to this one!

2. The method response from a HTTP 1.0 server is a MIME compatible document.
   1. What does this mean?
   2. Why is the "Content-length: " header required in HTTP 1.0?
   3. Why isn't the SMTP MIME "Content-encoding: " header required in HTTP 1.0?

3. A browser makes the following request: GET /Fig1.gif HTTP/1.0 What would the server return?

4. What is the HTTP 1.0 HEAD request method used for?

5. What is the MIME type for ordinary Web pages in HTTP 1.0?

6. A client can optionally include a GET request method header of the form If-Modified-Since:
   1. Why is this used?
   2. This header takes a date/time marker as a value. Is there an Internet standard format for this value? Hint: look in an RFC index, somewhere between RFC1200 and RFC1300.

7. The HTTP 1.0 specification permits a GET request method to include a "Referer: " header in the request. Why is this considered to be a potential breach of privacy?

8. (Tricky question) In HTTP 0.9, there was no way to specify the content type in objects returned from the server. How did the browser know whether it was receiving a Web page (in HTML), a GIF image, a sound sample or whatever?

9. (Research question) Give reasons why HTTP 1.0 is not a highly regarded protocol in the Internet technical community. How do you think HTTP 1.1 might address some of these problems?

10. Before coming to the tutorial, use your browser to "view source" for this tute sheet. Can you understand the HTML markups used? If you don't, ask for it to be explained in the tutorial.