CSc 361程序设计代做、代写c++，Java程序、Python编程代写

日期：2021-03-26 10:05

1 CSc 361: Computer Communications and Networks

2 (Spring 2021)

3 Assignment 3: Analysis of IP Protocol

4 Spec Out: March 5, 2021

5 Due: 11:55 pm April 2, 2021

6 1 Goal

7 The purpose of this assignment is to learn about the IP protocol. You are required to write a

8 python program to analyze a trace of IP datagrams.

9 2 Introduction

10 In this assignment, we will investigate the IP protocol, focusing on the IP datagram. Well do so

11 by analyzing a trace of IP datagrams sent and received by an execution of the traceroute program.

12 We will investigate the various fields in the IP datagram, and study IP fragmentation in detail.

13 A background of the traceroute program is summarized as follows. The traceroute program

14 operates by first sending one or more datagrams with the time-to-live (TTL) field in the IP header

15 set to 1; it then sends a series of one or more datagrams towards the same destination with a TTL

16 value of 2; it then sends a series of datagrams towards the same destination with a TTL value of 3;

17 and so on. Recall that a router must decrement the TTL in each received datagram by 1 (actually,

18 RFC 791 says that the router must decrement the TTL by at least one). If the TTL reaches 0, the

19 router returns an ICMP message (type 11 TTL-exceeded) to the sending host. As a result of this

20 behavior, a datagram with a TTL of 1 (sent by the host executing traceroute) will cause the router

21 one hop away from the sender to send an ICMP TTL-exceeded message back to the sender; the

22 datagram sent with a TTL of 2 will cause the router two hops away to send an ICMP message back

23 to the sender; the datagram sent with a TTL of 3 will cause the router three hops away to send an

24 ICMP message back to the sender; and so on. In this manner, the host executing traceroute can

25 learn the identities of the routers between itself and a chosen destination by looking at the source

26 IP addresses in the datagrams containing the ICMP TTL-exceeded messages. You will be provided

27 with a trace file created by traceroute.

28 Of course, you can create a trace file by yourself. Note that when you create the trace file,

29 you need to use different datagram sizes (e.g., 2500 bytes) so that the captured trace file includes

30 information on fragmentation.

31 3 Requirements

32 There are two requirements for this assignment:

1

33 3.1 Requirement 1 (R1)

34 You are required to write a python program to analyze the trace of IP datagrams created by

35 traceroute. To make terminologies consistent, in this assignment we call the source node as the

36 computer that executes traceroute. The ultimate destination node refers to the host that is the

37 ultimate destination defined when running traceroute. For example, the ultimate destination node

38 is “mit.edu” when you run

39 %traceroute mit.edu 2000

40 In addition, an intermediate destination node refers to the router that is not the ultimate destination

41 node but sends back a ICMP message to the source node.

42 As another example, you can set “don’t fragment”’ bit and set the number of probes per “ttl”

43 to 5 queries using the following command:

44 %traceroute -F -q 5 mit.edu 200

45 Your program needs to output the following information:

46 ? List the IP address of the source node, the IP address of ultimate destination node, the IP

47 address(es) of the intermediate destination node(s). If multiple intermediate destination nodes

48 exist, they should be ordered by their hop count to the source node in the increasing order.

49 ? Check the IP header of all datagrams in the trace file, and list the set of values in the protocol

50 field of the IP headers. Note that only different values should be listed in a set.

51 ? How many fragments were created from the original datagram? Note that 0 means no frag-

52 mentation. Print out the offset (in terms of bytes) of the last fragment of the fragmented IP

53 datagram. Note that if the datagram is not fragmented, the offset is 0.

54 ? Calculate the average and standard deviation of round trip time (RTT) between the source

55 node and the intermediate destination node (s) and the average round trip time between

56 the source node and the ultimate destination node. The average and standard deviation are

57 calculated over all fragments sent/received between the source nodes and the (intermediate/

58 ultimate) destination node.

59 The output format is as follows: (Note that the values do not correspond to any trace file).

60 The IP address of the source node: 192.168.1.12

61 The IP address of ultimate destination node: 12.216.216.2

62 The IP addresses of the intermediate destination nodes:

63 router 1: 24.218.01.102,

64 router 2: 24.221.10.103,

65 router 3: 12.216.118.1.

66

67 The values in the protocol field of IP headers:

68 1: ICMP

69 17: UDP

70

71

72 The number of fragments created from the original datagram is: 3

2

73 The offset of the last fragment is: 3680

74

75 The avg RTT between 192.168.1.12 and 24.218.01.102 is: 50 ms, the s.d. is: 5 ms

76 The avg RTT between 192.168.1.12 and 24.221.10.103 is: 100 ms, the s.d. is: 6 ms

77 The avg RTT between 192.168.1.12 and 12.216.118.1 is: 150 ms, the s.d. is: 5 ms

78 The avg RTT between 192.168.1.12 and 12.216.216.2 is: 200 ms, the s.d. is: 15 ms

79

80 3.2 Requirement 2 (R2)

81 Note: You can finish this part either with a python program or by manually col-

82 lecting/analyzing data. In other words, coding is optional for the tasks listed in this

83 section.

84 From a given set of five traceroute trace files, all with the same destination address,

85 ? determine the number of probes per “ttl” used in each trace file,

86 ? determine whether or not the sequence of intermediate routers is the same in different trace

87 files,

88 ? if the sequence of intermediate routers is different in the five trace files, list the difference and

89 explain why,

90 ? if the sequence of intermediate routers is the same in the five trace files, draw a table as shown

91 below (warning: the values in the table do not correspond to any trace files) to compare

92 the RTTs of different traceroute attempts. From the result, which hop is likely to incur the

93 maximum delay? Explain your conclusion.

TTL Average RTT Average RTT Average RTT Average RTT Average RTT

in trace 1 in trace 2 in trace 3 in trace 4 in trace 5

1 0.5 0.7 0.8 0.7 0.9

2 0.9 1 1.2 1.2 1.3

3 1.5 1.5 1.5 1.5 2.5

4 2.5 2 2 2.5 3

5 3 2.5 3 3.5 3.5

6 5 4 5 4.5 4

94

95 4 Miscellaneous

96 Important! Please read!

97 ? Same as in Assignment 2, you are not allowed in this assignment to use python packages that

98 can automatically extract each packet from the pcap files. That means, you can re-use your

99 code in Assignment 2 to extract packets.

100 ? Some intermediate router may only send back one “ICMP TTL exceeded” message for multiple

101 fragments of the same datagram. In this case, please use this ICMP message to calculate RTT

102 for all fragments. For example, Assume that the source sends Frag 1, Frag2, Frag 3 (of the

103 same datagram, ID: 3000). The timestamps for Frag1, Frag2, Frag3 are t1, t2, t3, respectively.

3

104 Later, the source receives one “ICMP TTL exceeded” message (ID: 3000). The timestamp is

105 T. Then the RTTs are calculated as: T ? t1, T ? t2, T ? t3.

106 ? More explanation about the output format

107 The number of fragments created from the original datagram is:

108

109 The offset of the last fragment is:

110 If there are multiple fragmented datagrams, you need to output the above information for

111 each datagram. For example, assume that the source sends two datagrams: D1, D2, where

112 D1 and D2 are the identification of the two datagrams. Assume that D1 has three fragments

113 and D2 has two fragments. Then output should be:

114 The number of fragments created from the original datagram D1 is: 3

115

116 The offset of the last fragment is: xxx.

117

118

119 The number of fragments created from the original datagram D2 is: 2

120

121 The offset of the last fragment is: yyy.

122

123 where xxx and yyy denote the actual number calculated by your program.

124 ? If the tracefile is captured in Linux, the source port number included in the original UDP

125 can be used to match against the ICMP error message. This is due to the special traceroute

126 implementation in linux, which uses UDP and ICMP. If the tracefile is captured in Windows,

127 we should use the sequence number in the returned ICMP error message to match the sequence

128 number in the ICMP echo (ping) message from the source node. Note that this ICMP error

129 message (type 11) includes the content of the ICMP echo message (type 8) from the source.

130 This is due to the special traceroute implementation in Windows, which uses ICMP only

131 (mainly message type 8 and message type 11). It is also possible that traceroute may be

132 implemented in another different way. For instance, we have found that some traceroute

133 implementation allows users to select protocol among ICMP, TCP, UDP and GRE. To avoid

134 the unnecessary complexity of your program, you only need to handle the two scenarios

135 in finding a match between the original datagram and the returned ICMP error

136 message: either (1) use the source port number in the original UDP, or (2) use the

137 sequence number in the original ICMP echo message. You code should automatically

138 find out the right case for matching datagrams in the trace file. We will not test your code

139 with a trace file not falling in the above cases.

140 5 Deliverables and Marking Scheme

141 For your final submission of your assignment, you are required to submit your source code to

142 brightspace. You should include a readme file to tell TA how to compile and run your code. In

4

143 addition, you are required to submit a pdf file for your solution of R2. Use %tar -czvf command in

144 linux.csc.uvic.ca to generate a .tar file and submit the .tar file. Make sure that you use %tar -xzvf

145 command to double-check if you have included all the files before submitting the tar file. Note that

146 your code will be tested over linux.csc.uvic.ca.

147 The marking scheme is as follows:

Components Weight

The IP address of the source node (R1) 5

The IP address of ultimate destination node (R1) 5

The IP addresses of the intermediate destination nodes (R1) 10

The correct order of the intermediate destination nodes (R1) 5

The values in the protocol field of IP headers (R1) 5

The number of fragments created from the original datagram (R1) 15

The offset of the last fragment (R1) 10

The avg RTTs (R1) 10

The standard deviations (R1) 5

The number of probes per ttl (R2) 10

Right answer to the second question (R2) 5

Right answer to the third/or fourth question (R2) 10

Readme.txt 5

Total Weight 100

148

149 6 Plagiarism

150 This assignment is to be done individually. You are encouraged to discuss the design of your solution

151 with your classmates, but each person must implement their own assignment.

152 The End

5