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Chapter 1: Problem 4

The Unix utility whois can be used to find the domain name corresponding to an organization, or vice versa. Read the man page documentation for whois and experiment with it. Try whois princeton.edu and whois princeton, for starters.

Short Answer

Expert verified
Use `whois domain` for domain info and `whois organization` for organization-related domains.

Step by step solution

01

Open Terminal

Open the terminal application on your computer. This is where commands will be entered.
02

Read Documentation

Type `man whois` and press Enter. This will display the manual page for the whois command, which provides detailed information on how to use it.
03

Run whois Command for Domain

Type `whois princeton.edu` and press Enter. This command will query the whois database and return information about the domain princeton.edu.
04

Run whois Command for Organization

Type `whois princeton` and press Enter. This command will query the whois database for information related to the organization 'Princeton' and may return multiple results.
05

Review Output

Examine the output provided by the whois commands. The output for `whois princeton.edu` will include details such as the domain name, registrar, registrant, and contact information. The output for `whois princeton` may include various related domains and registrations.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Unix utilities
Unix utilities are essential tools for performing a wide range of tasks in Unix-based operating systems. These tools are usually accessed via the command-line interface, providing a powerful way to interact with the system through typed commands.
Some key Unix utilities include:
  • file management tools (e.g., `cp`, `mv`, `rm`)
  • text processing tools (e.g., `grep`, `awk`, `sed`)
  • system monitoring tools (e.g., `top`, `ps`, `df`)
  • networking tools (e.g., `ping`, `netstat`, `ifconfig`)
Each utility typically has a man page (short for manual page) that provides detailed information about its usage, options, and examples. You can access a utility's man page by typing `man ` in the terminal.
domain name resolution
Domain name resolution is the process of translating a human-readable domain name (like example.com) into a machine-readable IP address that computers use to identify each other on the network.
This process is primarily handled by the Domain Name System (DNS). DNS acts like a phonebook for the internet, mapping domain names to IP addresses.
When you run the `whois` command, you're querying a database that contains registration information about domain names. This information can include:
  • The domain's registrar
  • The domain owner (registrant)
  • Contact information for the registrant
  • Key dates (registration, expiration)
The `whois` command helps network administrators, security researchers, and others gather important information about domains.
command-line tools
Command-line tools are programs that can be run from a command-line interface (CLI) rather than a graphical user interface (GUI). They are often preferred by power users and system administrators for their flexibility and scripting capabilities.
Key aspects of command-line tools include:
  • Efficiency: They can perform complex tasks quickly.
  • Automation: Command-line tools can be used in scripts to automate repetitive tasks.
  • Precision: They provide fine-grained control over the system.
The `whois` utility is a command-line tool specifically designed for querying domain registration information. By typing commands into the terminal, you can retrieve data about domains and organizations in just a few seconds.
networking basics
Networking basics involve understanding how computers communicate with each other over a network. This includes concepts such as IP addresses, DNS, and protocols like TCP/IP.
Here are some fundamental networking concepts:
  • IP Address: A unique identifier for a device on a network.
  • DNS: Converts domain names to IP addresses.
  • TCP/IP: A set of protocols governing how data is transmitted over the internet.
  • Subnetting: Dividing a network into smaller, manageable pieces.
Understanding these basics helps in using tools like `whois`, as it allows you to comprehend the information returned by the tool and how it fits into the larger picture of internet infrastructure.
system administration
System administration involves managing and maintaining computer systems and networks. This role encompasses a wide range of tasks, from setting up servers to ensuring security and troubleshooting issues.
Core responsibilities include:
  • User account management
  • System monitoring and performance tuning
  • Security management
  • Backup and recovery
  • Network configuration and management
Using tools like `whois` is part of network management tasks. By obtaining accurate domain registration information, system administrators can manage domain-related issues, improve security, and ensure proper communication within the network. The ability to efficiently utilize these tools is a critical skill for any system administrator.

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Most popular questions from this chapter

Suppose a 100-Mbps point-to-point link is being set up between Earth and a new lunar colony. The distance from the moon to Earth is approximately \(385,000 \mathrm{~km}\), and data travels over the link at the speed of light-3 \(\times 10^{8} \mathrm{~m} / \mathrm{s}\). (a) Calculate the minimum RTT for the link. (b) Using the RTT as the delay, calculate the delay \(\times\) bandwidth product for the link. (c) What is the significance of the delay \(\times\) bandwidth product computed in (b)? (d) A camera on the lunar base takes pictures of Earth and saves them in digital format to disk. Suppose Mission Control on Earth wishes to download the most current image, which is \(25 \mathrm{MB}\). What is the minimum amount of time that will elapse between when the request for the data goes out and the transfer is finished?

Consider a simple protocol for transferring files over a link. After some initial negotiation, A sends data packets of size \(1 \mathrm{~KB}\) to B; B then replies with an acknowledgment. A always waits for each ACK before sending the next data packet; this is known as stop-and-wait. Packets that are overdue are presumed lost and are retransmitted. (a) In the absence of any packet losses or duplications, explain why it is not necessary to include any "sequence number" data in the packet headers. (b) Suppose that the link can lose occasional packets, but that packets that do arrive always arrive in the order sent. Is a 2-bit sequence number (that is, \(N\) mod 4) enough for \(\mathrm{A}\) and \(\mathrm{B}\) to detect and resend any lost packets? Is a 1-bit sequence number enough? (c) Now suppose that the link can deliver out of order, and that sometimes a packet can be delivered as much as 1 minute after subsequent packets. How does this change the sequence number requirements?

Calculate the latency (from first bit sent to last bit received) for the following: (a) 10-Mbps Ethernet with a single store-and-forward switch in the path, and a packet size of 5000 bits. Assume that each link introduces a propagation delay of \(10 \mu \mathrm{s}\) and that the switch begins retransmitting immediately after it has finished receiving the packet. (b) Same as (a) but with three switches. (c) Same as (a) but assume the switch implements "cut-through" switching: It is able to begin retransmitting the packet after the first 200 bits have been received.

How long does it take to transmit \(x\) KB over a \(y\)-Mbps link? Give your answer as a ratio of \(x\) and \(y\).

Suppose that a certain communications protocol involves a per-packet overhead of 100 bytes for headers and framing. We send 1 million bytes of data using this protocol; however, one data byte is corrupted and the entire packet containing it is thus lost. Give the total number of overhead + loss bytes for packet data sizes of \(1000,5000,10,000\), and 20,000 bytes. Which size is optimal?
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