---
tags: Computer Network
---

# NCCUCS NET22 Lab01

## 1-1
**List 3 different protocols that appear in the protocol column in the unfiltered packet-listing window in step 7 above.**

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TCP, UDP, HTTP, SSDP etc.
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## 1-2
**How long did it take from when the HTTP GET message was sent until the HTTP OK reply was received?**

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17.843535 - 17.646637 = 0.196898 (s)
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## 1-3
**What is the Internet address of gaia.cs.umass.edu?
What is the Internet address of your computer?**

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Internet address of gaia.cs.umass.edu: 128.119.245.12 (destination IP)
Internet address of my computer: 192.168.0.235 (source IP)
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## 1-4
**Screenshot the two HTTP messages (GET and OK) referred to in question 2 above.**

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HTTP GET:


HTTP 200 OK:


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## 2-1
**Is your browser running HTTP version 1.0 or 1.1? What version of HTTP is the server running?**

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Both running HTTP version 1.1
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## 2-2

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

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zh-TW for Traditional Chinese and zh for Chinese.
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## 2-3
**What is the IP address of your computer?
What is the IP address of gaia.cs.umass.edu server?**

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IP address of my computer: 192.168.0.235 (source IP)
IP address of gaia.cs.umass.edu: 128.119.245.12 (destination IP)
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## 2-4

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

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Status Code: 200
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## 2-5
**When was the HTML file that you are retrieving last modified at the server?**

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Last Modified at 2022/11/12 06:59:01
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## 2-6

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

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Content Length = 81 bytes
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## 2-7

**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.**

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No, the raw data appears to match up exactly with what is shown in the packet-listing window.
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## 2-8

**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?**

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No, there's no “IF-MODIFIED-SINCE”” header in the first GET.
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## 2-9

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

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Yes, we can see the contents in the “Line-based text data” field.
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## 2-10

**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?**

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Yes, there's a “IF-MODIFIED-SINCE”” header in the second GET.

The information followed is: Sat, 12 Nov 2022 06:59:01 GMT\r\n
which is the date of the last modification of the file from the previous get request.
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## 2-11

**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.**

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The status code and phrase returned from the server is "304 Not Modified".

The server didn’t return the contents of the file since the browser loaded it
from its cache.
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## 2-12

**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?**

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There is 1 HTTP GET request message sent by my browser and the packet number is 1408.
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## 2-13

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

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Packet number: 1417
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## 2-14

**What is the status code and phrase in the response?**

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Status Code: 200
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## 2-15

**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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3 data-containing TCP segments were needed.
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## 2-16

**How many HTTP GET request messages did your browser send? To which Internet addresses are these GET requests sent?**

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3 HTTP GET request messages. Their Internet addresses are 128.119.245.12, 128.119.245.12 and 178.79.137.164.
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## 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.**

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The 2 images were downloaded serially.
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## 2-18

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

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Status code: 401, Phrase: Unauthorization
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## 2-19

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

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New Field: Authorization.
(Authorization: Basic d2lyZXNoYXJrLXNOdWRlbnRz0m5ldHdvcms=\r\n)
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## 3-1

**Run nslookup to obtain the IP address of a Web server in Asia. What is the IP address of that server?**

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IP address: 140.119.166.199
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## 3-2

**Run nslookup to determine the authoritative DNS servers for a university in Europe.**

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authoritative DNS server: primary.dns.cam.ac.uk
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## 3-3

**Run nslookup so that one of the DNS servers obtained in Question 3-2 is queried for the mail servers for Yahoo mail. What is its IP address?**

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No servers can be reached.
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## 3-4

**Locate the DNS query and response messages. Are they sent over UDP or TCP?**

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They are sent over UDP.
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## 3-5

**What is the destination port for the DNS query message?
What is the source port of DNS response message?**

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DNS Query:


DNS Response:


Destination port for the DNS query and source port of DNS response are both 53.
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## 3-6

**To what IP address is the DNS query message sent? Use ipconfig to determine the IP address of your local DNS server. Are these two IP addresses the same?**

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Console:


DNS Response Message:


It's send to 192.168.0.235, and the two IP addresses are the same.
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## 3-7

**Examine the DNS query message. What “Type” of DNS query is it? Does the query message contain any “answers”?**

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Type A. The query message does not contain any "answers".
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## 3-8

**Examine the DNS response message. How many “answers” are provided? What do each of these answers contain?**

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According to the "Answer RRs" field, we can know that there are 3 answers, which are:

1. www.ietf.org: type CNAME, class IN, cname www.ietf.org.cdn.cloudflare.net
2. www.ietf.org.cdn.cloudflare.net: type A, class IN, addr 104.16.44.99
3. www.ietf.org.cdn.cloudflare, net: type A, class IN, addr 104.16.45.99

The answers contain information about the name of the host, the type of address, class, the TTL and the data length.
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## 3-9

**Consider the subsequent TCP SYN packet sent by your host. Does the destination IP address of the SYN packet correspond to any of the IP addresses provided in the DNS response message?**

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The first SYN packet was sent to 104.16.44.99 which corresponds to the first IP address provided in the DNS response message.
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## 3-10

**This web page contains images. Before retrieving each image, does your host issue new DNS queries?**

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No, there are no new DNS queries issued.
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## 3-11

**What is the destination port for the DNS query message?
What is the source port of DNS response message?**

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DNS Query:


DNS Response:


Destination port for the DNS query and source port of DNS response are both 53.
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## 3-12

**To what IP address is the DNS query message sent? Is this the IP address of your default local DNS server?**

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IP: 192.168.0.235, which is the same IP address of my default local DNS server.
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## 3-13

**Examine the DNS query message. What “Type” of DNS query is it? Does the query message contain any “answers”?**

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Type A. The query message does not contain any "answers".
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## 3-14

**Examine the DNS response message. How many “answers” are provided? What do each of these answers contain?**

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According to the "Answer RRs" field, we can know that there are 3 answers.

The answers contain information about the name of the host, the type of address, class, the TTL and the data length.
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## 3-15

**To what IP address is the DNS query message sent? Is this the IP address of your default local DNS server?**

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IP: 192.168.0.235, which is the same IP address of my default local DNS server.
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## 3-16

**Examine the DNS query message. What “Type” of DNS query is it? Does the query message contain any “answers”?**

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Type NS. The query message does not contain any "answers".
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## 3-17

**Examine the DNS response message.
What MIT nameservers does the response message provide?
Does this response message also provide the IP addresses of the MIT name servers?**

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No, this response message does not provide the IP addresses of the MIT name servers.

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