WireShark Lab HTTP

1. The Basic HTTP GET/response interaction

Let’s begin our exploration of HTTP by downloading a very simple HTML file - one that is very short, and contains no embedded objects. Do the following:

1.      Start up your web browser.

2.      Start up the Wireshark packet sniffer, as described in the Introductory lab (but don’t yet begin packet capture). Enter “http” (just the letters, not the quotation marks) in the display-filter-specification window, so that only captured HTTP messages will be displayed later in the packet-listing window. (We’re only interested in the HTTP protocol here, and don’t want to see the clutter of all captured packets).

3.      Wait a bit more than one minute (we’ll see why shortly), and then begin Wireshark packet capture.

4.      Enter the following to your browser http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file1.html Your browser should display the very simple, one-line HTML file.

5.      Stop Wireshark packet capture.

Your Wireshark window should look similar to the window shown in Figure 1. If you are unable to run Wireshark on a live network connection, you can download a packet trace that was created when the steps above were followed.²

1.      Is your browser running HTTP version 1.0 or 1.1? What version of HTTP is the server running?

Jawab : Browser saya versi http adalah 1.1 , server juga versi http 1.1

2.      What languages (if any) does your browser indicate that it can accept to the server?

Jawab : language = en-us , en

3.      What is the IP address of your computer? Of the gaia.cs.umass.edu server?

Jawab :

Ip saya : 192.168.1.7

IP gaia.cs.umass.edu server : 128.119.245.12

4.      What is the status code returned from the server to your browser?

Jawab : Http /1.1 200 OK (text/html)

5.      When was the HTML file that you are retrieving last modified at the server?

Jawab : Last modified = sun, 21 jan 2018 06:59:01 GMT

6.      How many bytes of content are being returned to your browser?

Jawab : content-length = 128

7.      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? If so, name one.

Jawab : Tidak semua header bisa ditemukan dalam data raw

2. The HTTP CONDITIONAL GET/response interaction

Recall from Section 2.2.6 of the text, that most web browsers perform object caching and thus perform a conditional GET when retrieving an HTTP object. Before performing the steps below, make sure your browser’s cache is empty. (To do this under Firefox, select Tools->Clear Recent History and check the Cache box, or for Internet Explorer, select Tools->Internet Options->Delete File; these actions will remove cached files from your browser’s cache.) Now do the following:

•       Start up your web browser, and make sure your browser’s cache is cleared, as discussed above.

•       Start up the Wireshark packet sniffer

•       Enter the following URL into your browser http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file2.html Your browser should display a very simple five-line HTML file.

•       Quickly enter the same URL into your browser again (or simply select the refresh button on your browser)

•       Stop Wireshark packet capture, and enter “http” in the display-filter-specification window, so that only captured HTTP messages will be displayed later in the packet-listing window.

•       (Note: If you are unable to run Wireshark on a live network connection, you can use the http-ethereal-trace-2 packet trace to answer the questions below; see footnote 1. This trace file was gathered while performing the steps above on one of the author’s computers.)

Answer the following questions:

8.      Inspect the contents of the first HTTP GET request from your browser to the server. Do you see an “IF-MODIFIED-SINCE” line in the HTTP GET?

Jawab : Tidak

9.      Inspect the contents of the server response. Did the server explicitly return the contents of the file? How can you tell?

Jawab : Ya karena kita bisa melihat isinya di field Line-based text data

10.  Now inspect the contents of the second HTTP GET request from your browser to the server. Do you see an “IF-MODIFIED-SINCE:” line in the HTTP GET? If so, what information follows the “IF-MODIFIED-SINCE:” header?

Jawab : Ya , informasinya adalah sun, 21 jan 2018 06:59:01 GMT yang merupakan tanggal modifikasi terakhir file dari GET request sebelumnya

11.  What is the HTTP status code and phrase returned from the server in response to this second HTTP GET? Did the server explicitly return the contents of the file? Explain.

Jawab : status code = 304 dan phrase = Not Modified. Server tidak mengembalikan isi file karena browser memuatnya dari cache-nya

3. Retrieving Long Documents

In our examples thus far, the documents retrieved have been simple and short HTML files. Let’s next see what happens when we download a long HTML file. Do the following:

•       Start up your web browser, and make sure your browser’s cache is cleared, as discussed above.

•       Start up the Wireshark packet sniffer

•       Enter the following URL into your browser http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file3.html Your browser should display the rather lengthy US Bill of Rights.

•       Stop Wireshark packet capture, and enter “http” in the display-filter-specification window, so that only captured HTTP messages will be displayed.

•       (Note: If you are unable to run Wireshark on a live network connection, you can use the http-ethereal-trace-3 packet trace to answer the questions below; see footnote 1. This trace file was gathered while performing the steps above on one of the author’s computers.)

Answer the following questions:

12.  How many HTTP GET request messages did your browser send? Which packet number in the trace contains the GET message for the Bill or Rights?

Jawab : ada 1 HTTP GET

13.  Which packet number in the trace contains the status code and phrase associated with the response to the HTTP GET request?

Jawab : di trace saya paket nomor 15

14.  What is the status code and phrase in the response?

Jawab : Status code 200 ,phrase OK

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

Jawab : Ada 5 data TCP segment yaitu 1440 , 1440, 1440 dan 541 totalnya 4861

4.  HTML Documents with Embedded Objects

Now that we’ve seen how Wireshark displays the captured packet traffic for large HTML files, we can look at what happens when your browser downloads a file with embedded objects, i.e., a file that includes other objects (in the example below, image files) that are stored on another server(s).

Do the following:

•       Start up your web browser, and make sure your browser’s cache is cleared, as discussed above.

•       Start up the Wireshark packet sniffer

•       Enter the following URL into your browser http://gaia.cs.umass.edu/wireshark-labs/HTTP-wireshark-file4.html

Your browser should display a short HTML file with two images. These two images are referenced in the base HTML file. That is, the images themselves are not contained in the HTML; instead the URLs for the images are contained in the downloaded HTML file. As discussed in the textbook, your browser will have to retrieve these logos from the indicated web sites. Our publisher’s logo is retrieved from the www.aw-bc.com web site. The image of the cover for our 5^th edition (one of our favorite covers) is stored at the manic.cs.umass.edu server.

•       Stop Wireshark packet capture, and enter “http” in the display-filter-specification window, so that only captured HTTP messages will be displayed.

Answer the following questions:

16.  How many HTTP GET request messages did your browser send? To which Internet addresses were these GET requests sent?

Jawab : ada 4 , alamat ip yang menjadi Get request adalah 128.119.245.12 ada 2 dan 128.119.245.90 ada 2

17.  Can you tell whether your browser downloaded the two images serially, or whether they were downloaded from the two web sites in parallel? Explain.

Jawab : Dengan memeriksa port TCP kita dapat melihat apakah file kita diunduh secara serial atau paralel. Dalam kasus ini, 2 gambar dikirimkan melalui 2 koneksi TCP sehingga mereka diunduh secara serial.

5 HTTP Authentication

Finally, let’s try visiting a web site that is password-protected and examine the sequence of HTTP message exchanged for such a site. The URL http://gaia.cs.umass.edu/wireshark-labs/protected_pages/HTTP-wireshark-file5.html is password protected. The username is “wireshark-students” (without the quotes), and the password is “network” (again, without the quotes). So let’s access this “secure” password-protected site. Do the following:

•       Make sure your browser’s cache is cleared, as discussed above, and close down your browser. Then, start up your browser

•       Start up the Wireshark packet sniffer

•       Enter the following URL into your browser http://gaia.cs.umass.edu/wireshark-labs/protected_pages/HTTP-wireshark-file5.html

Type the requested user name and password into the pop up box.

•       Stop Wireshark packet capture, and enter “http” in the display-filter-specification window, so that only captured HTTP messages will be displayed later in the packet-listing window.

•       (Note: If you are unable to run Wireshark on a live network connection, you can use the http-ethereal-trace-5 packet trace to answer the questions below; see footnote 2. This trace file was gathered while performing the steps above on one of the author’s computers.)

Answer the following questions:

18.  What is the server’s response (status code and phrase) in response to the initial HTTP GET message from your browser?

Jawab : status code 401, phrase = Unauthorized

19.  When your browser’s sends the HTTP GET message for the second time, what new field is included in the HTTP GET message?

Jawab : field baru di pesan HTTP GET yang kedua adalah

Authorization: Basic d2lyZXNoYXJrLXN0dWRlbnRzOm5ldHdvcms=\r\n

Download Laporan WireShark Lab HTTP