Networks代写|Data Communication & Networks Assignment #3


II. Objectives

1. Learn application layer concepts.
2. Lear about various protocols such as HTTP, SMTP, P2P etc.
3. Experiment with Data Encoding and Transmission.
4. Program using sockets.

III. References

1. Slides and handouts posted on the course Web site
2. Textbook chapters 1 and 2

IV. Software Required

1. Microsoft Word
2. Win Zip as necessary

V. Assignment

1. Problem 1:

a. What transport layer protocol SMTP uses and why?

b. Research and describe the protocols used in WhatsApp and iMessage?

c. Briefly describe two different server placement approaches in CDN.

d. Explain the meaning of HTTP response codes:

1) 201
2) 404
3) 500

e. Describe the difference between download-and-delete mode vs. download-and
keep mode in POP3.

f. Name two benefits of P2P over client-server architecture.

g. Visit in your favorite browser. Which protocols are used in
application layer and transport layer? Provide proof via screenshot(s) using

Are the following statements true or false?

a. In order to communicate with a process in a host, one only needs the IP address
of the host.
b. SSL is a transport layer protocol.
c. Both UDP and TCP guarantee the delivery of the packet from source to
d. If an application uses UDP, that means that application does not need reliable
data transfer.

3. Problem 3:

If you download a HTML file which references to 8 images, how many RTTs are

a. Your browser uses non-persistent HTTP?
b. Your browser uses persistent HTTP?

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