Question 1
Alice aliceABCmail.com sends an email to Bob bobXYZmail.com, and Bob reads the email successfully. What application layer protocols isare used? Describe the activities involved by the protocols. 7 marks
Question 2
Consider the P2P session below. The upload and download rates are in terms of Mbps. Assume there is no delay in the network core, and all hosts participate in the entire session. Calculate the time required for all hosts to get the file of size n x 100 Mb, where n is the last digit of your student ID number. Set n to 10 if the last digit is 0. Show your steps. 5 marks
x
Question 3
n
100
Mb
In the TCP session below, suppose the starting sequence number is n, where n is the first 4 digits of your student ID number e.g. 1912. Determine the sequence numbers of all Data packets, and the acknowledgement numbers of all ACK packets. 6 marks
Data
1: 320 bytes
Data
2: 260
bytes
Data
3: 180
bytes
ACKa
X
ACKb
Timeout
Data
2
260
bytes
:
ACKc
Page 1 of 4
Question 4
The IP datagram with size 3000n x 100 bytes, including the header 20 bytes, arrives at a router. The MTU of the routers outgoing link is 1300 bytes. Suppose n is the last digit of your student ID number. State the value of length, fragment flag and fragment offset of all fragments created by the router. Show your steps. 10 marks
Question 5
Given the network topology below in Packet Tracer, and Router 1 is just booted with the default startup configuration. What commands should you use to configure Router 1 and setup OSPF
routing?
12 marks
f00
Question 6
f0
1
Consider that you are going to visit the web page http:www.secret.comexamtipsindex.html for the first time. The web page shows two pictures tips1.jpg and tips2.jpg on the screen, each with a hyperlink to download a document file. There was no cache in your PC and in the web cache of your network. The DNS hierarchy is given below:
s
3
0
0
Page 2 of 4
root
.edu .com
dns.secret.com
a Suppose there is no cached record in all DNS servers. Describe how your browser obtains the
IP address of the web server using iterated query. 6 marks b Suppose HTTP version 1.1 is used. Write the request line and Host field of the header of HTTP
request message for requesting the page index.html. 4 marks
c HTTP version 1.1 adopts persistent HTTP. By using a time diagram, illustrate the HTTP messages exchange between your browser and web server until the web page is displayed.
5 marks
Question 7
local DNS server
You
authoritative
The figure above demonstrates the change in congestion window size of a TCP Reno sender. The initial threshold is set to 16 segments.
a What are the TCP states in rounds 1 to 5, in rounds 5 to 9 and in round 10? 3 marks Page 3 of 4
b The window size was reduced after round 9 and after round 16. What was happened and how did TCP Reno handle such situation? 8 marks
c Suppose all segments in round 20 were transmitted successfully. What should be the window size in round 21? 1 mark
d How is TCP Reno different from TCP Tahoe? Indicate the round number that the operation will be different if TCP Tahoe is used. 3 marks Question 8
Consider the network topology below. There are four routers in the network, with the number next to a link indicating the cost of using that particular link.
A
4B2 2
15
C
D
a Routing algorithm can be classified into link state and distance vector. What are the differences between them? 4 marks
b Suppose distance vector algorithm is used. What is the initial distance vector maintained in eachrouter? 4marks
c Demonstrate the distance vector updates in the network until the algorithm converges.
7 marks
Question 9
Consider that you are in a classroom and connect to the college wireless LAN using WiFi. There are some mobile users in the same BSS with you. The college network is protected by intrusion detection system IDS.
a Describe the hiddenterminal problem and exposedterminal problem in a wireless network, and how CSMACA can handle these problems. 8 marks
b If you move to another classroom, you connect to another BSS, but you still remain in the college LAN with the same IP address. Why can this happen? 3 marks
c Explain how IDS protects the network and why it is better than firewall. 4 marks
End of Assignment
Page 4 of 4
Reviews
There are no reviews yet.