Week1-Lab-Wireshark-Intro-v8.0 wireshark使用
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2023-12-22
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Wireshark Lab:
Getting Started v8.0
Supplement to Computer Networking: A Top-Down
Approach, 8
th
ed., J.F. Kurose and K.W. Ross
“Tell me and I forget. Show me and I remember. Involve me
and I understand.” Chinese proverb
© 2005-2020, J.F Kurose and K.W. Ross, All Rights Reserved
One’s understanding of network protocols can often be greatly deepened by “seeing
protocols in action” and by “playing around with protocols” – observing the sequence of
messages exchanged between two protocol entities, delving down into the details of
protocol operation, and causing protocols to perform certain actions and then observing
these actions and their consequences. This can be done in simulated scenarios or in a
“real” network environment such as the Internet. In the Wireshark labs you’ll be doing in
this course, you’ll be running various network applications in different scenarios using
your own computer. You’ll observe the network protocols in your computer “in action,”
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.
In this first Wireshark lab, you’ll get acquainted with Wireshark, and make some simple
packet captures and observations.
The basic tool for observing the messages exchanged between executing protocol entities
is called a packet sniffer. As the name suggests, a packet sniffer captures (“sniffs”)
messages being sent/received from/by your computer; it will also typically store and/or
display the contents of the various protocol fields in these captured messages. A packet
sniffer itself is passive. It observes messages being sent and received by applications and
protocols running on your computer, but never sends packets itself. Similarly, received
packets are never explicitly addressed to the packet sniffer. Instead, a packet sniffer
receives a copy of packets that are sent/received from/by application and protocols
executing on your machine.
Figure 1 shows the structure of a packet sniffer. At the right of Figure 1 are the protocols
(in this case, Internet protocols) and applications (such as a web browser or email client)
that normally run on your computer. The packet sniffer, shown within the dashed
rectangle in Figure 1 is an addition to the usual software in your computer, and consists
of two parts. The packet capture library receives a copy of every link-layer frame that
is sent from or received by your computer over a given interface (link layer, such as
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