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Wireshark Lab

This page is a generated reference surface for selective reading. It exists to keep the learner apps guide-first while still preserving source access.

Learning objectives​

  • Explain the main ideas and vocabulary in Wireshark Lab.
  • Work through the source examples for Wireshark Lab without depending on raw chunk order.
  • Use Wireshark Lab as selective reference when learner modules point back to Computer Networking.

Prerequisites​

  • None curated yet.

Module targets​

  • module-05-network-protocols-sockets

AI companion modes​

  • Explain simply
  • Socratic tutor
  • Quiz me
  • Challenge my understanding
  • Diagnose my confusion
  • Generate extra practice
  • Revision mode
  • Connect forward / backward

Source-of-truth note​

This unit is anchored to Computer Networking and the source chapter "Wireshark Lab". Use external resources only to clarify, extend, or modernize details without replacing the chapter's conceptual spine.

External enrichment​

No chapter-specific enrichment resources are curated yet. Add them in the unit manifest when a source clearly improves learning.

Source provenance​

  • Primary source: Computer Networking
  • Source chapter: Wireshark Lab
  • Raw source file: 040-wireshark-lab.md

Merged source​

Wireshark Lab​

Wireshark Lab

"Tell me and I forget. Show me and I remember. Involve me and I understand."

Chinese proverb

One's understanding of network protocols can often be greatly deepened by seeing them in action and by playing around with them--observing the sequence of messages exchanged between two protocol entities, delving into the details of protocol operation, causing protocols to perform certain actions, and observing these actions and their consequences. This can be done in simulated scenarios or in a real network environment such as the Internet. The interactive animations at the textbook Web site take the first approach. In the Wireshark labs, we'll take the latter approach. You'll run network applications in various scenarios using a computer on your desk, at home, or in a lab. You'll observe the network protocols in your computer, interacting and exchanging messages with protocol entities executing elsewhere in the Internet. Thus, you and your computer will be an integral part of these live labs. You'll observe--and you'll learn--by doing.

The basic tool for observing the messages exchanged between executing protocol entities is called a packet sniffer. As the name suggests, a packet sniffer passively copies (sniffs) messages being sent from and received by your computer; it also displays the contents of the various protocol fields of these captured messages. A screenshot of the Wireshark packet sniffer is shown in Figure 1.28. Wireshark is a

Wireshark Lab 107

Command menus

Listing of captured packets

Details of selected packet header

Packet contents in hexadecimal and ASCII

Figure 1.28 ♦ A Wireshark screenshot (Wireshark screenshot reprinted by permission of the Wireshark Foundation.)

free packet sniffer that runs on Windows, Linux/Unix, and Mac computers. Throughout the textbook, you will find Wireshark labs that allow you to explore a number of the protocols studied in the chapter. In this first Wireshark lab, you'll obtain and install a copy of Wireshark, access a Web site, and capture and examine the protocol messages being exchanged between your Web browser and the Web server.

You can find full details about this first Wireshark lab (including instructions about how to obtain and install Wireshark) at the Web site www.pearsonglobaleditions.com.

Interview: Leonard Kleinrock​

Courtesy of Leonard Kleinrock Leonard Kleinrock is a professor of computer science at the University of California, Los Angeles. In 1969, his computer at UCLA became the first node of the Internet. His creation of the mathematical theory of packet-switching principles in 1961 became the technology behind the Internet. He received his B.E.E. from the City College of New York (CCNY) and his masters and PhD in electrical engineering from MIT.

What made you decide to specialize in networking/Internet technology? As a PhD student at MIT in 1959, I looked around and found that most of my classmates were doing research in the area of information theory and coding theory that had been established by the great researcher, Claude Shannon. I judged that he had solved most of the important problems already. The research problems that were left were hard and seemed to me to be of lesser consequence. So I decided to launch out in a new area that no one else had yet conceived of. Happily, at MIT I was surrounded by many computers, and it was clear to me that, sooner or later, these machines would need to communicate with each other. At the time, there was no effective way for them to do so and that the solution to this important problem would have impact. I had an approach to this problem and so, for my PhD research, I decided to create a mathematical theory to model, evaluate, design and optimize efficient and reliable data networks.

What was your first job in the computer industry? What did it entail? I went to the evening session at CCNY from 1951 to 1957 for my bachelor's degree in electrical engineering. During the day, I worked first as a technician and then as an electrical engineer at a small, industrial electronics firm called Photobell. While there, I introduced digital technology to their product line. Essentially, we were using photoelectric devices to detect the presence of certain items (boxes, people, etc.) and the use of a circuit known then as a bistable multivibrator was just what we needed to bring digital processing into this field of detection. These circuits happen to be the building blocks for computers, and have come to be known as flip-flops or switches in today's vernacular.

What was going through your mind when you sent the first host-to-host message (from UCLA to the Stanford Research Institute)? Frankly, we had no idea of the importance of that event. We had not prepared a special message of historic significance, as did so many inventors of the past (Samuel Morse with "What hath God wrought." or Alexander Graham Bell with "Watson, come here! I want you." or Neal Armstrong with "That's one small step for a man, one giant leap for mankind.") Those guys were smart! They understood media and public relations. All we wanted to do was to demonstrate our ability to remotely login to the SRI computer. So we typed the "L",

which was correctly received, we typed the "o" which was correctly received, and then we typed the "g" which caused the SRI host computer to crash! So, it turned out that our message was the shortest and perhaps the most prophetic message ever, namely "Lo!" as in "Lo and behold!"

Earlier that year, I was quoted in a UCLA press release saying that once the network was up and running, it would be possible to gain access to computer utilities from our homes and offices as easily as we gain access to electricity and telephone connectivity. So my vision at that time was that the Internet would be ubiquitous, always on, always available, anyone with any device could connect from any location, and it would be invisible. However, I never anticipated that my 99-year-old mother would use the Internet at the same time that my 5 year-old granddaughter was--and indeed she did!

What is your vision for the future of networking? The easy part of the vision is to predict the infrastructure itself. I anticipate that we will see considerable deployment of wireless and mobile devices in smart spaces to produce what I like to refer to as the Invisible Internet. This step will enable us to move out from the netherworld of cyberspace to the physical world of smart spaces. Our environments (desks, walls, vehicles, watches, belts, fingernails, bodies and so on) will come alive with technology, through actuators, sensors, logic, processing, storage, cameras, microphones, speakers, displays, and communication. This embedded technology will allow our environment to provide the IP services wherever and whenever we want. When I walk into a room, the room will know I entered. I will be able to communicate with my environment naturally, as in spoken English, haptics, gestures, and eventually through brain-Internet interfaces; my requests will generate replies that present Web pages to me from wall displays, through my eyeglasses, as speech, holograms, and so forth. Looking a bit further out, I see a networking future that includes the following additional key components. I see customized intelligent software agents deployed across the network whose function it is to mine data, act on that data, observe trends, and carry out tasks dynamically and adaptively. I see the deployment of blockchain technology that provides irrefutable, immutable distributed ledgers coupled with reputation systems that provide credibility to the contents and functionality. I see considerably more network traffic generated not so much by humans, but by the embedded devices, the intelligent software agents and the distributed ledgers. I see large collections of self-organizing systems controlling this vast, fast network. I see huge amounts of information flashing across this network instantaneously with this information undergoing enormous processing and filtering. The Invisible Internet will essentially be a pervasive global nervous system. I see all these things and more as we move headlong through the twenty-first century.

The harder part of the vision is to predict the applications and services, which have consistently surprised us in dramatic ways (e-mail, search technologies, the World Wide Web, blogs, peer-to-peer networks, social networks, user generated content, sharing of

music, photos, and videos, etc.). These applications have "come of the blue", sudden, unanticipated and explosive. What a wonderful world for the next generation to explore!

What people have inspired you professionally? By far, it was Claude Shannon from MIT, a brilliant researcher who had the ability to relate his mathematical ideas to the physical world in highly intuitive ways. He was a superb member of my PhD thesis committee.

Do you have any advice for students entering the networking/Internet field? The Internet and all that it enables is a vast new frontier, continuously full of amazing challenges. There is room for great innovation. Don't be constrained by today's technology. Reach out and imagine what could be and then make it happen.