Problem Solving Report 3

SIT202 Computer Networks Trimester 2, 2018
Problem Solving Report 3 (due 11:59 pm September 23rd 2018)
Total Marks =30
This will be converted to 10% of total marks
Questions:
1. A) The World Wide Web was originally designed as a stateless entity. However, over time it was identified that a stateful relationship between a web client and a web server can benefit in many ways including e-commerce, collecting web behaviour of web users etc. The cookie mechanism was introduced for this purpose. In your lecture slides (week-8 to week-9), the following diagram demonstrates the use of a cookie. Explain each of the six steps indicated in the following diagram for using the cookie in online shopping.
Marking Guideline:
Overall Explanations (9.0 marks):
o 9.0 marks: Explained clearly all six steps (server/client activity, cookie, contents in the request/response)
o 8.0 Explained but missing two components or have two errors in one of the step/steps from six steps (server/client activity, cookie, contents in the request/response)
o 7.0 Explained but missing 4 components or have 4 errors in one of the step/steps from six steps (server/client activity, cookie, contents in the request/response)
o 6.0 Explained but missing 6 components or have 6 errors in one of the step/steps from six steps (server/client activity, cookie, contents in the request/response)
o 5.0 Explained but missing 8 components or have 8 errors in one of the step/steps from six
steps (server/client activity, cookie, contents in the request/response)
o 4.0 Explained but missing 10 components or have 10 errors in one of the step/steps from six
steps (server/client activity, cookie, contents in the request/response)
o 3.0 Explained but missing 12 components or have 12 errors in one of the step/steps from six
steps (server/client activity, cookie, contents in the request/response)
o 2.0 Explained but missing 14 components or have 14 errors in one of the step/steps from six
steps (server/client activity, cookie, contents in the request/response)
o 1.0 Explained but missing 16 components or have 16 errors in one of the step/steps from six
steps (server/client activity, cookie, contents in the request/response)
o 0.0 Explained but missing 18 components or have 18 errors in one of the step/steps from six
steps (server/client activity, cookie, contents in the request/response), all incorrect or did
not attempt.

1. B) Consider a scenario where an advertising company pays fees to Deakin
University for including banner ads in Deakin’s web site, i.e., an image presenting an
advertisement of a product from a manufacturer which is linked to the manufacturer’s
web server. Deakin receives payment from the advertising company based on the
number of visits by its users to the manufacturer’s web site. The advertising company
gets payment from the manufacturer based on the number of times the advertisement
is displayed. Prepare a diagram illustrating how the cookie is used when retrieving a
Deakin web page containing an advertisement and then tracking the users of Deakin’s
web site visiting the manufacturer’s web site by clicking on an advertisement.
Explain the steps in your diagram.


Overall Explanations and diagram (8.0 marks):

o 8.0 marks: Explained clearly all four steps (source and destination of each step form
different server/client, contents in the request/response) and presented in the diagram
o 7.0 Explained but missing two components or have two errors from (source and
destination of each step form different server/client, contents in the request/response) in
one of the step/steps from four steps and presented in the diagram.
o 6.0 Explained but missing 4 components or have 4 errors from (source and destination of
each step form different server/client, contents in the request/response) in one of the
step/steps from four steps and presented in the diagram.
o 5.0 Explained but missing 6 components or have 6 errors from (source and destination of
each step form different server/client, contents in the request/response) in one of the
step/steps from four steps and presented in the diagram.
o 4.0 Explained but missing 8 components or have 8 errors from (source and destination of
each step form different server/client, contents in the request/response) in one of the
step/steps from four steps and presented in the diagram.
o 3.0 Explained but missing 10 components or have 10 errors from (source and destination
of each step form different server/client, contents in the request/response) in one of the
step/steps from four steps and presented in the diagram.
o 2.0 Explained but missing 12 components or have 12 errors from (source and destination
of each step form different server/client, contents in the request/response) in one of the
step/steps from four steps and presented in the diagram.
o 1.0 Explained but missing 14 components or have 14 errors from (source and destination
of each step form different server/client, contents in the request/response) in one of the
step/steps from four steps and presented in the diagram.
o 0.0 Explained but all incorrect or did not attempt.


2. In the following diagram, a web client is communicating with a web server which opens a TCP
connection at client’s end. The client is using an initial sequence number (ISN) 2048 with a port of
51000 and receiving window size of 2000. In response, server also opens a TCP connection with ISN
21732 and receiving window size of 4000, port 80. After connection establishment, client sends two
data segments each of size 500 bytes. Then server responds in a single segment with 1000 bytes. Then
client closes the connection, in response server also closes the connection.
Show all TCP segments during connection establishment, data transfer and connection termination
between client and server (no segments are corrupted/dropped in the exchange). For each segment,
write header information which should include port number, sequence number, acknowledgement
number, values of all bits in the control field, window sizes and ranges of data bytes in the data section
(as appropriate for the segment type). Each segment needs to be placed in a separate table. First row
in the table should mention the label of segment based on their type and direction clearly client to
server or vice versa. All tables should have a number at the beginning (on top of the table) which
indicates the order they are sent by either the client or the server.
Marking guide line: Total =13 Marks
Marks for each segment-1.44, then each component marks=segment mark/number of component in the segment
1. Connection establishment (11 component + 13 component + 13 component)
2. Data transfer ( 15 component + 15 component + 15 component)
3. Connection termination ( 13 component + 13 component + 13 component)