[kurose@MacBook-Pro-6 ~ % nslookup www.iitb.ac.in Server: 75.75.75.75 Address: 75.75.75.75#53 Non-authoritative answer: Name: www.iitb.ac.in Address: 103.21.124.10 [kurose@MacBook-Pro-6 ~ % nslookup -type=NS iitb.ac.in Server: 75.75.75.75 Address: 75.75.75.75#53 Non-authoritative answer: iitb.ac.in nameserver = dns1.iitb.ac.in. iitb.ac.in nameserver = dns2.iitb.ac.in. iitb.ac.in nameserver = dns3.iitb.ac.in. Figure 4: using nslookup to find the IP address of www.iitb.ac.in and the names of the authoritative name servers for the iitb.ac.in domain
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iitb.ac.in in Figure 4. The IP address provided in the output is the answer. The IP address of www.iitb.ac.in is 103.21.124.10. Show more…
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Richard has just been given a 8-question multiple-choice quiz in his history class. Each question has five answers, of which only one is correct. Since Richard has not attended class recently, he doesn't know any of the answers. Assuming that Richard guesses on all eight questions, find the indicated probabilities. (Round your answers to three decimal places.) (a) What is the probability that he will answer all questions correctly? (b) What is the probability that he will answer all questions incorrectly? (c) What is the probability that he will answer at least one of the questions correctly? Compute this probability two ways. First, use the rule for mutually exclusive events and the probabilities shown in the binomial probability distribution table. Then use the fact that P(r ≥ 1) = 1 - P(r = 0). Compare the two results. Should they be equal? Are they equal? If not, how do you account for the difference? They should be equal, but may differ slightly due to rounding error. They should not be equal, but are equal. They should be equal, but differ substantially. They should be equal, but may not be due to table error. (d) What is the probability that Richard will answer at least half the questions correctly?
Sri K.
See Exercise 53 for some background. When information is transmitted, there may be some errors in the communication. We present a method of adding extra information to messages so that most errors that occur during transmission can be detected and corrected. Such methods are referred to as error-correcting codes. (Compare these with codes whose purpose is to conceal information.) The pictures of man's first landing on the Moon (in 1969 ) were televised just as they had been received and were not very clear, since they contained many errors induced during transmission. On later missions, much clearer error-corrected pictures were obtained. In computers, information is stored and processed in the form of strings of binary digits, 0 and $1 .$ This stream of binary digits is often broken up into "blocks" of eight binary digits (bytes). For the sake of simplicity, we will work with blocks of only four binary digits (i.e., with vectors in $\mathbb{F}^{4}$ ), for example, $$\cdot\cdot\cdot | 1011 | 1001 | 1010 | 1011 | 1000 | \cdot\cdot\cdot$$ Suppose these vectors in $\mathbb{F}^{4}$ have to be transmitted from one computer to another, say, from a satellite to ground control in Kourou, French Guiana (the station of the European Space Agency). A vector $\vec{u}$ in $\mathbb{F}^{4}$ is first transformed into a vector $\vec{v}=M \vec{u}$ in $\mathbb{F}^{7}$, where $M$ is the matrix you found in Exercise $53 .$ The last four entries of $\vec{v}$ are just the entries of $\vec{u}$; the first three entries of $\vec{v}$ are added to detect errors. The vector $\vec{v}$ is now transmitted to Kourou. We assume that at most one error will occur during transmission; that is, the vector $\vec{w}$ received in Kourou will be either $\vec{v}$ (if no error has occurred) or $\vec{w}=\vec{v}+\vec{e}_{i}$ (if there is an error in the $i$ th component of the vector). a. Let $H$ be the Hamming matrix introduced in Exercise $53 .$ How can the computer in Kourou use $H \vec{w}$ to determine whether there was an error in the transmission? If there was no error, what is $H \vec{w} ?$ If there was an error, how can the computer determine in which component the error was made? b. Suppose the vector \[ \vec{w}=\left[\begin{array}{l} 1 \\ 0 \\ 1 \\ 0 \\ 1 \\ 0 \\ 0 \end{array}\right] \] is received in Kourou. Determine whether an error was made in the transmission and, if so, correct it. (That is, find $\vec{v}$ and $\vec{u}$.)
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Image and Kernel of a Linear Transformation
Your boss at work gave you three PCAP files to investigate and extract information from them. All three PCAP files represent traffic. The three PCAP files present their own cases. The first one is investigating network traffic to see if there is any misuse or changes to this network (Dump 0 and 1 PCAP). The second PCAP file was gathered after a breach in a system happened. Your mission, if you decide to accept it or not, is to solve both cases based on the following: Case 1: Downloading Dump0.pcap and Dump1.pcap files attached to this assignment and answering the following questions: 1. What type of protocols are used in Dump0 and Dump1? 2. List as much as you can types of devices in Dump1 and Dump0. And show their frames. Is there changes in the connectivity? 3. Who is the internet service provider in Dump1 and Dump0? 4. What is the router IP address, Mac Address, and brand? Show the frame and explain. 5. Identify computers in Dump1 and their OS. Can you identify the processor if possible? 6. Is there a Windows OS? And if so, what version? Show in what frame in Dump0 and Dump1. 7. How many browsers are used in Dump0 and Dump1? 8. What's happening in Frame 1070 of Dump1? 9. Find a Frame with CS0 and explain it in detail with examples in Dump1. 10. List as much as you can running applications and indicate their frames in Dump0 and Dump1. 11. Is there a Google Cast in Dump1 and can you identify the type of device? 12. List at least two websites and show them in Dump0 and Dump1. 13. Is there any application running on any of the devices in Dump0 and if so, show the application, frame, and device if possible. 14. Explain in detail what is happening from Frame 30386 to 30389 in Dump1. 15. What kind of information can you extract from Frame 24890? Explain in detail. 16. You got information that there might be calendar information in Dump0. Show it and give an example. Case 2: Downloading Dump2.pcap file attached to this assignment and answering the following questions: 1. What kind of protocols were used in Dump2? 2. Are there any servers? And what is their type? 3. Is there a link to any web browser? 4. Extract the username and password.
Akash M.
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