Lab3-DNS: Spring 2022 COSC 370-001 COMPUTER NETWORKS

	Attempt	Time	Score
KEPT	Attempt 2	2 minutes	42 out of 42
LATEST	Attempt 2	2 minutes	42 out of 42
	Attempt 1	9 minutes	40 out of 42

DNS-1 Lab: Q01 Introduction and taking nslookup out for a spin

You must read Wireshark DNS lab manual before answering these questions.

The answers to the questions are based on packets in the trace files with names of the form dns-wireshark-trace*-1 (pay careful attention to the '-1' in the filename) that are posted under MyClass/Modules, so make sure you have these specific trace files open in Wireshark when you answer these questions!

Questions Q01 through Q02 can be answered directly from Figure 4 in the DNS Wireshark lab v8 write up.

DNS-1 Lab: Q01. Using nslookup to lookup a Type=A record. Given the nslookup output in Figure 4 in the WiresharkLab v8.1 writeup, what is the IP address of www.iitb.ac.in?

Enter the IP address in dotted decimal notation (include each dot, omit any leading zeros for any byte that is non-zero, and enter a 0 if one of the address bytes has a zero value, e.g., 10.0.216.54):

Nice! This answer is correct.

DNS-1 Lab: Q02 nslookup: which server provides an answer?. Given the nslookup output in Figure 4 in the WiresharkLab v8.1 writeup, what is the IP address of the DNS server that provided the answer to the nslookup command in question Q01 above?

Enter the IP address in dotted decimal notation (include each dot, omit any leading zeros for any byte that is non-zero, and enter a 0 if one of the address bytes has a zero value, e.g., 10.0.216.54):

Nice! This answer is correct.

DNS-1 Lab: Q05.1 resolving gaia.cs.umass.edu (a).

To answer questions 5-11, use trace file dns-wireshark-trace1-1. This trace file contains packets sent and received in involved in retrieving the webpage http://gaia.cs.umass.edu/kurose_ross/, which will require resolving the name gaia.cs.umass.edu.

Locate the first DNS query message resolving the name gaia.cs.umass.edu. What is the packet number[1] in the trace for the DNS query message?

[1] Remember that this “packet number” is assigned by Wireshark for listing purposes only; it is NOT a packet number contained in any real packet header.

15

17

22

30

Nice! This answer is correct.

DNS-1 Lab: Q05.2 resolving gaia.cs.umass.edu (b). Locate the initial DNS query message resolving the name gaia.cs.umass.edu. Is this query message sent over UDP or TCP?

UDP

TCP

Nice! This answer is correct.

DNS-1 Lab: Q06.1 resolving gaia.cs.umass.edu (c). Now locate the corresponding DNS response to the initial DNS query. What is the packet number in the trace for the DNS response message?

15

17

22

Nice! This answer is correct.

DNS-1 Lab: Q06.2 resolving gaia.cs.umass.edu (d). Locate the DNS response message in reply to initial DNS query message resolving the name gaia.cs.umass.edu. Is this response message sent over UDP or TCP?

UDP

TCP

Nice! This answer is correct.

DNS-1 Lab: Q07.1 resolving gaia.cs.umass.edu (e). What is the destination port for the initial DNS query message?

53

54

23

59742

Nice! This answer is correct.

DNS-1 Lab: Q07.2 resolving gaia.cs.umass.edu (f). What is the source port that the initial DNS query message was sent from?

58350

54

23

59742

Nice! This answer is correct.

DNS-1 Lab: Q08 resolving gaia.cs.umass.edu (g). To what IP address is the initial DNS query message sent?

Enter the IP address in dotted decimal notation (include each dot, omit any leading zeros for any byte that is non-zero, and enter a 0 if one of the address bytes has a zero value, e.g., 10.0.216.54):

Nice! This answer is correct.

DNS-1 Lab: Q10.1 resolving gaia.cs.umass.edu (j). Examine the DNS response message to the initial query message. How many “questions” does this DNS response message contain?

0

1

3

Can't tell from Wireshark's parsing of the DNS message header.

Nice! This answer is correct.

DNS-1 Lab: Q10.2 resolving gaia.cs.umass.edu (k). Examine the DNS response message to the initial query message.How many “answers” does this DNS response message contain?

0

1

3

Can't tell from Wireshark's parsing of the DNS message header.

Nice! This answer is correct.

DNS-1 Lab: Q11 resolving gaia.cs.umass.edu a second time. The web page for the base file http://gaia.cs.umass.edu/kurose_ross/ references the image object http://gaia.cs.umass.edu/kurose_ross/header_graphic_book_8E_2.jpg , which, like the base web page, is on gaia.cs.umass.edu. Suppose that a user enters the URL for the base page to be displayed, and suppose that the HTTP and DNS caches are empty.

In the matching below, indicate the packet number in the trace that matches with the HTTP request/reply or DNS request/reply noted.

What is the packet number in the trace for the initial HTTP GET request for the base file http://gaia.cs.umass.edu/kurose_ross/?
What are the packet numbers in the trace of the DNS query and the DNS response messages sent/received to resolve gaia.cs.umass.edu so that this initial HTTP request can be sent to the gaia.cs.umass.edu IP address?
What is the packet number in the trace for the HTTP GET request for the image object http://gaia.cs.umass.edu/kurose_ross/header_graphic_book_8E2.jpg?
What is the packet number of the DNS query message sent to resolve gaia.cs.umass.edu so that the HTTP request for http://gaia.cs.umass.edu/kurose_ross/header_graphic_book_8E_2.jpg can be sent to the IP address for gaia.cs.umass.edu?

HTTP request for base file http://gaia.cs.umass.edu/kurose_ross/

DNS query message sent to resolve gaia.cs.umass.edu so that the HTTP request for base file http://gaia.cs.umass.edu/kurose_ross/ can be sent to the IP address for gaia.cs.umass.edu

DNS response message received to resolve gaia.cs.umass.edu so that the HTTP request for base file http://gaia.cs.umass.edu/kurose_ross/ can be sent to the IP address for gaia.cs.umass.edu

HTTP request for image object http://gaia.cs.umass.edu/kurose_ross/header_graphic_book_8E_2.jpg

DNS-1 Lab: Q12.1 resolving www.cs.umass.edu via nslookup (a). To answer questions 12-15, use trace file dns-wireshark-trace2-1. This trace file contains packets sent and received in involved in performing the nslookup described in the DNS Wireshark Lab v8.1 writeup.

What is the destination port for the initial DNS query message generated by nslookup?

53

54

23

59742

Nice! This answer is correct.

DNS-1 Lab: DNS-1 Lab: Q12.2 resolving www.cs.umass.edu via nslookup (b). What is the source port that the initial DNS query message was sent from?

57837

54

23

59742

Nice! This answer is correct.

DNS-1 Lab: Q13.1 resolving www.cs.umass.edu via nslookup (c). To what IP address is the initial DNS query message sent?

Enter the IP address in dotted decimal notation (include each dot, omit any leading zeros for any byte that is non-zero, and enter a 0 if one of the address bytes has a zero value, e.g., 10.0.216.54):

Nice! This answer is correct.

DNS-1 Lab: Q13.2 resolving www.cs.umass.edu via nslookup (d). Is this the address of the local DNS server for the computer on which the nslookup was issued, or the authoritative name server for www.cs.umass.edu?

The local DNS server for the computer on which the nslookup was issued.

The authoritative name server for www.cs.umass.edu.

Nice! This answer is correct.

DNS-1 Lab: Q14.1 resolving www.cs.umass.edu (e). How many “questions” does this DNS message contain?

0

1

3

Can't tell from Wireshark's parsing of the DNS message header.

Nice! This answer is correct.

DNS-1 Lab: Q14.2 resolving www.cs.umass.edu (f). Examine the initial DNS query message. How many “answers” does this DNS message contain?

0

1

3

Can't tell from Wireshark's parsing of the DNS message header.

Nice! This answer is correct.

DNS-1 Lab: Q15.1 resolving www.cs.umass.edu (g). Examine the DNS response message to the initial query message. How many “questions” does this DNS response message contain?

0

1

3

Can't tell from Wireshark's parsing of the DNS message header.

Nice! This answer is correct.

DNS-1 Lab: Q15.2 resolving www.cs.umass.edu (h). Examine the DNS response message to the initial query message. How many “answers” does this DNS response message contain?

0

1

3

Can't tell from Wireshark's parsing of the DNS message header.

Nice! This answer is correct.