Institutionen för Data och Systemvetenskap, Stockholms Universitet och KTH

*:96 Internet appliction protocols and standards

Exam 1996-09-20

With correct answers

The following documents can be used during the exam:

(a) All documents whose name begin with "RFC".

(b) All documents whose designation includes "draft-ietf-".

(b) Internet Port Numbers.

(d) Ordinary language wordbooks.

(e) Any other document, which in the list of documents for the course are marked exam.

No. Question Max score

1. World Wide Web and Usenet News differ in their method of storing and replicating data. Describe the differences, and the pros and cons of the methods used.
Reply: The main principle of Usenet News is to replicate each document to each server, and the user gets his articles from the local server. In the WWW, documents are primarily stored on one master server, even if caching can be used.
Advantage with WWW: Less storage cost, controlled master copy, long time availability, less censorship.
Advantage with Usenet News: Fast response times, better availability, less network load.
9

2. The HTTP protocol is built on short connections, transfer of data, and immediate disconnections. This gives problems if you wish to design an application where the computer needs to know what a certain user has done earlier. Describe different hetmods of handling this problem. Also discuss the pros- and cons of the methods you describe.
Reply:

Put transaction identifier in a custom URL
Put transaction identifier in a hidden field in a form
Put all session knowledge in hidden or public fields in a form
Put transaction identifier in a magic cookie
Use persistent connection facility of HTTP/1.1
Log the IP address of the client in the server

Advantage with full session knowledge: No session need be kept in the server. Disadvantage: Much information can slow down response time.
Disadvantage with magic cookie and persistent connections: Not supported by all web browsers.
Disadvantage with IP address logging: Insecure, more than one user might access from the same IP address.
8

3. A client program wishes to download a document with URL:
HTTP: //dsv.su.se/jpalme/courses.html
Specify which commands to and through the net which are performed from the initial connection to the final disconnection. Also specify the parameters to the command. You can use either HTTP version 1.0 or version 1.1 in your reply.
Reply:
C: <establish connection to www.dsv.su.se on port 80>
C: GET /~jpalme/courses.html HTTP/1.0
S: HTTP/1.0 200 OK
S: ... transfer of HTML text ...
S: <closes the connection to the client>
7

4. You want to send a collection of e-mail messages in one single e-mail message. Which media types would be suitable for this.
Reply: Use a multipart/digest, which consists of parts, each of which is in the message/rfc822 format.
4

Questions can be answered in Swedish or English

No.	Question	Max score

1.	World Wide Web and Usenet News differ in their method of storing and replicating data. Describe the differences, and the pros and cons of the methods used. Reply: The main principle of Usenet News is to replicate each document to each server, and the user gets his articles from the local server. In the WWW, documents are primarily stored on one master server, even if caching can be used. Advantage with WWW: Less storage cost, controlled master copy, long time availability, less censorship. Advantage with Usenet News: Fast response times, better availability, less network load.	9
2.	The HTTP protocol is built on short connections, transfer of data, and immediate disconnections. This gives problems if you wish to design an application where the computer needs to know what a certain user has done earlier. Describe different hetmods of handling this problem. Also discuss the pros- and cons of the methods you describe. Reply: Put transaction identifier in a custom URL Put transaction identifier in a hidden field in a form Put all session knowledge in hidden or public fields in a form Put transaction identifier in a magic cookie Use persistent connection facility of HTTP/1.1 Log the IP address of the client in the server Advantage with full session knowledge: No session need be kept in the server. Disadvantage: Much information can slow down response time. Disadvantage with magic cookie and persistent connections: Not supported by all web browsers. Disadvantage with IP address logging: Insecure, more than one user might access from the same IP address.	8
3.	A client program wishes to download a document with URL: HTTP: //dsv.su.se/jpalme/courses.html Specify which commands to and through the net which are performed from the initial connection to the final disconnection. Also specify the parameters to the command. You can use either HTTP version 1.0 or version 1.1 in your reply. Reply: C: <establish connection to www.dsv.su.se on port 80> C: GET /~jpalme/courses.html HTTP/1.0 S: HTTP/1.0 200 OK S: ... transfer of HTML text ... S: <closes the connection to the client>	7
4.	You want to send a collection of e-mail messages in one single e-mail message. Which media types would be suitable for this. Reply: Use a multipart/digest, which consists of parts, each of which is in the message/rfc822 format.	4