Lab2-Http: Spring 2022 COSC 370-001 COMPUTER NETWORKS

	Attempt	Time	Score
KEPT	Attempt 2	2 minutes	48 out of 48
LATEST	Attempt 2	2 minutes	48 out of 48
	Attempt 1	24 minutes	47 out of 48

HTTP-1 Lab: Q01.1 Introduction and HTTP GET/response

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

The answers to the questions are based on packets in the trace files with names of the form http-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!

To answer questions Q01 through Q07, use the trace file http-wireshark-trace1-1.

Q01.1 Which version of HTTP? Which version of HTTP is your browser running?

1

1.1

2

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HTTP-1 Lab: Q02 Which languages? What languages (if any) does your browser indicate that it can accept from the server? Select all correct answers.

en

Java

da

French

None of these is accepted.

en-gb

HTML

en-us

Nice! These answers are correct.

HTTP-1 Lab: Q03.1 Client IP address. What is the IP address of your (the client, with a browser) computer?

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):

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HTTP-1 Lab: Q03.2 HTTP server IP address. What is the the HTTP server that replied to your HTTP GET request?

Enter the IP address in dotted decimal notation (include each dot, and omit any leading zeros for any byte, e.g., 10.1.216.54):

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HTTP-1 Lab: Q04.1 HTTP server response code? What is the status code returned from the server to your browser in response to the original HTTP GET?

200

404

305

318

505

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HTTP-1 Lab: Q05.1 Date Modified. At what date was the HTML file that you are retrieving last modified at the server?

Enter the date in MM/DD/YYYY format (including the slashes, "/" and any leading 0's needed):

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HTTP-1 Lab: Q05.2 Time File Last Modified. At what time was the HTML file that you are retrieving last modified at the server?

Enter the time in HH:MM:SS GMT format (including the colons, and any leading zeros needed):

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HTTP-1 Lab: Q06 How many bytes returned? How many bytes of content are being returned to your browser?

Enter the number of integer bytes (without any leading zeros):

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HTTP-1 Lab: Q07 Missing Fields? By inspecting the raw data in the packet content window, do you see any headers within the data that are not displayed in the packet-listing window?

No

Yes

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HTTP-1 Lab: Q08 The Conditional GET - client request (a)

Questions 8 and 11 explore the HTTP conditional GET and the If-Modified-Since field; these questions and answers are based on the Wireshark trace file http-wireshark-trace2-1.

Locate the first HTTP GET in this trace file (the first GET for the object http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file2.html) Do you see an “IF-MODIFIED-SINCE” line in this HTTP GET request?

No

Yes

There's not enough information in the trace to know.

Maybe

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HTTP-1 Lab: Q11 The Conditional GET - server reply (b). Locate the server reply to the second HTTP GET in this tracefile (the second GET for http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file2.html) (Links to an external site.) Did the server explicitly return the contents of the file? How could you tell?

Yes, the server returned the full contents of file. There are 371 bytes of lined-based text data in the body of the "200 OK" reply message.

No, the server did not return the full contents of file. There are zero bytes of lined-based text data in the body of the "200 OK" reply message.

No, the server did not return the full contents of file. There are zero bytes of lined-based text data in the body of the "304 Not Modified" reply message.

Yes, the server returned the full contents of file. This is evidenced by a "HTML file attached: TES" field in the "200 OK" reply message.

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HTTP-1 Lab: Q12.1 Retrieving a large file - client request

Questions 12 through 15 explore HTTP behavior when a large object is requested; these questions and answers are based on the Wireshark trace file http-wireshark-trace3-1.

How many HTTP GET request messages did your browser send in order to download the lengthy US Bill of Rights, located at http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file3.html ?:

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HTTP-1 Lab: Q12.2 Retrieving a large file - client request. Which packet number in the trace contains the GET message that your browser sent in order to download the lengthy US Bill of Rights, located at http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file3.html (Links to an external site.) ?:

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HTTP-1 Lab: Q13 Retrieving a large file - server reply. Which packet number in the trace contains the server reply to the client GET message that your browser sent in order to download the lengthy US Bill of Rights, located at http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file3.html (Links to an external site.)? :

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HTTP-1 Lab: Q14.1 Retrieving a large file - server reply. Locate the server reply to the client GET message that your browser sent in order to download the lengthy US Bill of Rights, located at http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file3.html (Links to an external site.)? What is the status code on the HTTP reply message?

100

200

304

206

404

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HTTP-1 Lab: Q14.2 Retrieving a large file - server reply. Locate the server reply to the client GET message that your browser sent in order to download the lengthy US Bill of Rights, located at http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file3.html (Links to an external site.)? What is the status phase on the HTTP reply message?

Continue

OK

Not Modified

Not Found

Partial Content

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HTTP-1 Lab: Q15.1 Retrieving a large file - server reply

Let's again look at the server reply to the client GET message that your browser sent in order to download the lengthy US Bill of Rights, located at http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file3.html

How many data-containing TCP segments were needed to carry the single HTTP response and the text of the Bill of Rights:

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HTTP-1 Lab: Q15.2 Retrieving a large file - server reply.

Let's again look at the server reply to the client GET message that your browser sent in order to download the lengthy US Bill of Rights, located at http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file3.html

What at the packet numbers (packet index) in the trace file of the multiple TCP segments that collectively carry the single HTTP response and the text of the Bill of Rights? [Hint: careful this may take some thought and digging.]

27

28

29

30

31

32

33

Nice! These answers are correct.

HTTP-1 Lab: Q16.1 Downloading HTML Documents with Embedded Objects - client side

Questions 16 through 17 explore HTTP behavior when an object containing embedded objects is requested; these questions and answers are based on the Wireshark trace file http-wireshark-trace4-1.

In total, how many HTTP GET request messages did your browser send in order to download the file and all of the objects embedded within the HTTP-wireshark-file4.html base file:

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HTTP-1 Lab: Q16.2 Downloading HTML Documents with Embedded Objects - client side.

To which server addresses were the multiple HTTP GET request messages sent in order for your browser to download the base file and all of the objects embedded within the base file, http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file4.html?

Exactly one HTTP GET request went to 128.119.245.12 (gaia.cs.umass.edu). There were no other HTTP GET requests.

Exactly two different HTTP GET requests went to 128.119.245.12 (gaia.cs.umass.edu). There were no other HTTP GET requests.

Exactly two different HTTP GET requests went to 128.119.245.12 (gaia.cs.umass.edu) - one for the base file, and one for an image object. One additional HTTP GET request went to 192.168.1.102. These three are all of the HTTP requests made.

Exactly two different HTTP GET requests went to 128.119.245.12 (gaia.cs.umass.edu) - one for the base file, and one for an image object. One additional HTTP GET request went to 178.79.137.164. These three are all of the HTTP requests made.

Exactly two different HTTP GET requests went to 128.119.245.12 (gaia.cs.umass.edu) - one for the base file, and one for an image object. One additional HTTP GET request went to 178.79.137.164, which return a 301 Object Moved code, and so a fourth GET request was made to 104.98.115.146. These four request are all of the HTTP requests made.

Exactly two different HTTP GET requests went to 128.119.245.12 (gaia.cs.umass.edu) - one for the base file, and one for an image object. One additional HTTP GET request went to 178.79.137.164, which return a 301 Object Moved code, and so a fourth GET request was made to re-request a different file from 178.79.137.164. These four request are all of the HTTP requests made.

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HTTP-1 Lab: Q17 Downloading HTML Documents with Embedded Objects - client side. Can you tell whether your browser downloaded the two image objects serially, or whether they were downloaded from the two web sites in parallel? Choose the statement below that best explains the answer to this question.

The two image object file were downloaded in parallel. This is evidenced by the fact that two GET request messages (for the image objects) are made before either of the image objects are received.

The two image object file were downloaded serially. This is evidenced by the fact that the second of the GET request messages (for the image objects) is not made until after the first image is received.

Based on the interleaving of the GET request messagess (for the image objects) and the server replies, it's not possible to know if they were downloaded serially or in parallel.

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HTTP-1 Lab: Q18.1 Simple (and insecure) HTTP Authentication.

Questions 18 and 19 explore the simple (and insecure) basic sequence of HTTP messages exchanged for a password-protected site for the case that HTTP is run directly over TCP. These questions and answers are based on the Wireshark trace file http-wireshark-trace5-1.

Enter the packet number (index of the packet in the trace file) of the packet containing the initial HTTP GET request that is sent to gaia.cs.umass.edu to retrieve the HTTP-wireshark-file5.html file:

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HTTP-1 Lab: Q18.2 Simple (and insecure) HTTP Authentication. What is the server’s response (status code and phrase) in response to the initial HTTP GET message (for the HTTP-wireshark-file5.html base file) from your browser? (Aside: all of the replies below are valid response codes and phrases).

401 Unauthorized

200 OK

203 Non-Authoritative Information

401 Authorization Required

511 Network Authentication Required

403 Forbidden

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HTTP-1 Lab: Q19 Simple (and insecure) HTTP Authentication.

When your browser sends the HTTP GET message for the second time (to re-request the HTTP-wireshark-file5.html base file), what new field is included in this second HTTP GET message?

Authorization:

Authenticate:

Password:

ETag

WWW-Authenticate

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