Recent questions and answers in Computer Networks

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Computer Networking
What is the use of MAC broadcast address in ARP?

asked 15 hours ago in Computer Networks by Somdatta Sen (49 points) | 3 views

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Andrew S. Tanenbaum Edition 5th Exercise 8 Question 17 (Page No. 873)
Using the RSA public key cryptosystem, with a = 1, b = 2 . . . y = 25, z = 26. (a) If p = 5 and q = 13, list five legal values for d. (b) If p = 5, q = 31, and d = 37, find e. (c) Using p = 3, q = 11, and d = 9, find e and encrypt ‘‘hello’’.

answered 1 day ago in Computer Networks by abhishekmehta4u Boss (29k points) | 4 views

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Andrew S. Tanenbaum Edition 5th Exercise 8 Question 22 (Page No. 873)
A math class has 25 students. Assuming that all of the students were born in the first half of the year—between January 1st and June 30th— what is the probability that at least two students have the same birthday? Assume that nobody was born on leap day, so there are 181 possible birthdays.

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 3 views

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Andrew S. Tanenbaum Edition 5th Exercise 8 Question 33 (Page No. 874)
33. Two users can establish a shared secret key using the Diffie-Hellman algorithm, even if they have never met, share no secrets, and have no certificates (a) Explain how this algorithm is susceptible to a man-in-the-middle attack. (b) How would this susceptibility change if n or g were secret?

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 1 view

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Andrew S. Tanenbaum Edition 5th Exercise 8 Question 32 (Page No. 874)
The Diffie-Hellman key exchange is being used to establish a secret key between Alice and Bob. Alice sends Bob (227, 5, 82). Bob responds with (125). Alice’s secret number, x, is 12, and Bob’s secret number, y, is 3. Show how Alice and Bob compute the secret key.

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 2 views

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Andrew S. Tanenbaum Edition 5th Exercise 8 Question 25 (Page No. 873)
Alice wants to communicate with Bob, using public-key cryptography. She establishes a connection to someone she hopes is Bob. She asks him for his public key and he sends it to her in plaintext along with an X.509 certificate signed ... that Bob does not care who he is talking to (e.g., Bob is some kind of public service).

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 3 views

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Andrew S. Tanenbaum Edition 5th Exercise 8 Question 18 (Page No. 873)
Alice and Bob use RSA public key encryption in order to communicate between them. Trudy finds out that Alice and Bob shared one of the primes used to determine the number n of their public key pairs. In other words, Trudy found out that na = pa × q and nb = pb × q. How can Trudy use this information to break Alice’s code?

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 1 view

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 32 (Page No. 761)
Write a program in JavaScript that accepts an integer greater than 2 and tells whether it is a prime number. Note that JavaScript has if and while statements with the same syntax as C and Java. The modulo operator is %. If you need the square root of x, use Math.sqrt (x).

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 3 views

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9

Andrew S. Tanenbaum Edition 5th Exercise 7 Question 46 (Page No. 762)
Some cybersquatters have registered domain names that are misspellings of common corporate sites, for example, www.microsfot.com. Make a list of at least five such domains.

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 1 view

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 47 (Page No. 762)
Numerous people have registered DNS names that consist of www.word.com, where word is a common word. For each of the following categories, list five such Web sites and briefly summarize what it is (e.g., www.stomach. ... , foods, household objects, and body parts. For the last category, please stick to body parts above the waist.

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 3 views

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 48 (Page No. 762)
Rewrite the server of Fig. 6-6 as a true Web server using the GET command for HTTP 1.1. It should also accept the Host message. The server should maintain a cache of files recently fetched from the disk and serve requests from the cache when possible.

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 2 views

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 23 (Page No. 759)
Imagine that someone in the math department at Stanford has just written a new document including a proof that he wants to distribute by FTP for his colleagues to review. He puts the program in the FTP directory ftp/pub/forReview/newProof.pdf. What is the URL for this program likely to be?

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 2 views

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 23 (Page No. 759)
Although it was not mentioned in the text, an alternative form for a URL is to use the IP address instead of its DNS name. Use this information to explain why a DNS name cannot end with a digit.

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 1 view

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 20 (Page No. 759)
Does Webmail use POP3, IMAP, or neither? If one of these, why was that one chosen? If neither, which one is it closer to in spirit?

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 3 views

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 15 (Page No. 759)
In any standard, such as RFC 5322, a precise grammar of what is allowed is needed so that different implementations can interwork. Even simple items have to be defined carefully. The SMTP headers allow white space between the tokens. Give two plausible alternative definitions of white space between tokens.

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 6 views

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 14 (Page No. 759)
Suppose that John just set up an auto-forwarding mechanism on his work email address, which receives all of his business-related emails, to forward them to his personal email address, which he shares with his wife. John' ... vacation daemon on his work machine. What happens when an email is received at John's work email address?

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 7 views

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 10 (Page No. 759)
A large law firm, which has many employees, provides a single email address for each employee. Each employee's email address is <login>@lawfirm.com. However, the firm did not explicitly define the format of the login. ... for the email addresses of all its employees. How can this be done without rocking the boat too much?

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 2 views

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 9 (Page No. 759)
Electronic mail systems need directories so people’s email addresses can be looked up. To build such directories, names should be broken up into standard components (e.g., first name, last name) to make searching possible. Discuss some problems that must be solved for a worldwide standard to be acceptable.

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 1 view

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 8 (Page No. 759)
Some email systems support a Content Return: header field. It specifies whether the body of a message is to be returned in the event of nondelivery. Does this field belong to the envelope or to the header?

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 2 views

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 7 (Page No. 759)
The number of companies with a Web site has grown explosively in recent years. As a result, thousands of companies are registered in the com domain, causing a heavy load on the top-level server for this domain. ... introducing new top-level domain names). It is permitted that your solution requires changes to the client code.

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 1 view

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 3 (Page No. 759)
The number of companies with a Web site has grown explosively in recent years. As a result, thousands of companies are registered in the com domain, causing a heavy load on the top-level server for this domain. ... introducing new top-level domain names). It is permitted that your solution requires changes to the client code.

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 1 view

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 6 (Page No. 759)
Can a machine with a single DNS name have multiple IP addresses? How could this occur?

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 2 views

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 4 (Page No. 759)
John wants to have an original domain name and uses a randomized program to generate a secondary domain name for him. He wants to register this domain name in the com generic domain. The domain name that was generated is 253 characters long. Will the com registrar allow this domain name to be registered?

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 1 view

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Andrew S. Tanenbaum Edition 5th Exercise 7 Question 4 (Page No. 759)
DNS uses UDP instead of TCP. If a DNS packet is lost, there is no automatic recovery. Does this cause a problem, and if so, how is it solved?

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 2 views

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25

Andrew S. Tanenbaum Edition 5th Exercise 7 Question 3 (Page No. 759)
Consider a situation in which a cyberterrorist makes all the DNS servers in the world crash simultaneously. How does this change one’s ability to use the Internet?

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 2 views

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26

Andrew S. Tanenbaum Edition 5th Exercise 7 Question 1 (Page No. 759)
Many business Computers have three distinct world wide unique identifiers. what are they?

asked 1 day ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 2 views

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27

Andrew S. Tanenbaum Edition 5th Exercise 6 Question 43 (Page No. 610)
What is the bandwidth-delay product for a 50-Mbps channel on a geostationary satellite? If the packets are all 1500 bytes (including overhead), how big should the window be in packets?

answered 2 days ago in Computer Networks by Debdeep1998 Junior (547 points) | 8 views

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28

Andrew S. Tanenbaum Edition 5th Exercise 6 Question 46 (Page No. 610)
Design and implement a chat system that allows multiple groups of users to chat. A chat coordinator resides at a well-known network address, uses UDP for communication with chat clients, sets up chat servers for each chat ... to start, join, and leave a chat session. Design and implement the coordinator, server, and client code.

asked 2 days ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 3 views

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29

Andrew S. Tanenbaum Edition 5th Exercise 6 Question 39 (Page No. 609)
To get around the problem of sequence numbers wrapping around while old packets still exist, one could use 64-bit sequence numbers. However, theoretically, an optical fiber can run at 75 Tbps. What maximum packet lifetime is ... even with 64-bit sequence numbers? Assume that each byte has its own sequence number, as TCP does.

asked 2 days ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 3 views

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30

Andrew S. Tanenbaum Edition 5th Exercise 6 Question 37 (Page No. 609)
A CPU executes instructions at the rate of 1000 MIPS. Data can be copied 64 bits at a time, with each word copied costing 10 instructions. If an coming packet has to be copied four times, can this system handle a ... , assume that all instructions, even those instructions that read or write memory, run at the full 1000-MIPS rate.

asked 2 days ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 4 views

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31

Andrew S. Tanenbaum Edition 5th Exercise 6 Question 37 (Page No. 609)
Suppose that you are measuring the time to receive a segment. When an interrupt occurs, you read out the system clock in milliseconds. When the segment is fully processed, you read out the clock again. You measure 0 msec 270,000 times and 1 msec 730,000 times. How long does it take to receive a segment?

asked 2 days ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 3 views

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32

Andrew S. Tanenbaum Edition 5th Exercise 6 Question 36 (Page No. 609)
In a network whose max segment is 128 bytes, max segment lifetime is 30 sec, and has 8-bit sequence numbers, what is the maximum data rate per connection?

asked 2 days ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 2 views

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33

Andrew S. Tanenbaum Edition 5th Exercise 6 Question 35 (Page No. 609)
To address the limitations of IP version 4, a major effort had to be undertaken via IETF that resulted in the design of IP version 6 and there are still is significant reluctance in the adoption of this new version. However, no such major effort is needed to address the limitations of TCP. Explain why this is the case.

asked 2 days ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 6 views

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34

Andrew S. Tanenbaum Edition 5th Exercise 6 Question 34 (Page No. 609)
What is the fastest line speed at which a host can blast out 1500-byte TCP payloads with a 120-sec maximum packet lifetime without having the sequence numbers wrap around? Take TCP, IP, and Ethernet overhead into consideration. Assume that Ethernet frames may be sent continuously.

asked 2 days ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 1 view

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35

Andrew S. Tanenbaum Edition 5th Exercise 6 Question 33 (Page No. 609)
A TCP machine is sending full windows of 65,535 bytes over a 1-Gbps channel that has a 10-msec one-way delay. What is the maximum throughput achievable? What is the line efficiency?

asked 2 days ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 4 views

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36

Andrew S. Tanenbaum Edition 5th Exercise 6 Question 32 (Page No. 609)
If the TCP round-trip time, RTT, is currently 30 msec and the following acknowledgements come in after 26, 32, and 24 msec, respectively, what is the new RTT estimate using the Jacobson algorithm? Use α = 0.9.

asked 2 days ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 2 views

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37

Andrew S. Tanenbaum Edition 5th Exercise 6 Question 31 (Page No. 609)
Suppose that the TCP congestion window is set to 18 KB and a timeout occurs. How big will the window be if the next four transmission bursts are all successful? Assume that the maximum segment size is 1 KB.

asked 2 days ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 8 views

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38

Andrew S. Tanenbaum Edition 5th Exercise 6 Question 30 (Page No. 609)
Consider the effect of using slow start on a line with a 10-msec round-trip time and no congestion. The receive window is 24 KB and the maximum segment size is 2 KB. How long does it take before the first full window can be sent?

asked 2 days ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 2 views

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39

Andrew S. Tanenbaum Edition 5th Exercise 6 Question 29 (Page No. 609)
Describe two ways to get into the SYN RCVD state of Figure.

asked 2 days ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 3 views

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40

Andrew S. Tanenbaum Edition 5th Exercise 6 Question 28 (Page No. 608)
The maximum payload of a TCP segment is 65,495 bytes. Why was such a strange number chosen?

asked 2 days ago in Computer Networks by ajaysoni1924 Loyal (6.4k points) | 5 views

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