Data packet: Difference between revisions

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[[file:network.png|right|frame|Networks<ref>http://www.flaticon.com/</ref>]]
[[file:network.png|right|frame|Networks<ref>http://www.flaticon.com/</ref>]]


A computer network or data network is a telecommunications network which allows computers to exchange data. In computer networks, networked computing devices exchange data with each other using a data link. The connections between nodes are established using either cable media or wireless media. The best-known computer network is the Internet.
A packet is a basic unit of communication over a digital network. A packet is also called a datagram, a segment, a block, a cell or a frame, depending on the protocol used for the transmission of data. When data has to be transmitted, it is broken down into similar structures of data before transmission, called packets, which are reassembled to the original data chunk once they reach their destination.


Network computer devices that originate, route and terminate the data are called [[network nodes]]Nodes can include hosts such as personal computers, phones, servers as well as networking hardware. Two such devices can be said to be networked together when one device is able to exchange information with the other device, whether or not they have a direct connection to each other.
The structure of a packet depends on the type of packet it is and on the protocolNormally, a packet has a header and a payload.


Computer networks differ in the [[transmission medium]] used to carry their signals, the communications protocols to organize network traffic, the network's size, topology and organizational intent.
The header keeps overhead information about the packet, the service, and other transmission-related data. For example, data transfer over the Internet requires breaking down the data into IP packets, which is defined in IP (Internet Protocol), and an IP packet includes:


Computer networks support an enormous number of applications such as access to the World Wide Web, video, digital audio, shared use of application and storage servers, printers, and fax machines, and use of email and instant messaging applications as well as many others. In most cases, application-specific communications [[protocols]] are [[Network layers | layered]] (i.e. carried as payload) over other more general communications protocols.<ref>https://en.wikipedia.org/wiki/Computer_network</ref>
* The source IP address, which is the IP address of the machine sending the data. 
* The destination IP address, which is the machine or device to which the data is sent.
* The sequence number of the packets, a number that puts the packets in order such that they are reassembled in a way to get the original data back exactly as it was prior to transmission. 
* The type of service
* Flags
* And some other technical data
* The payload, which represents the bulk of the packet (all the above is considered as overhead), and is actually the data being carried.  


(Above used with gratitude from: https://www.lifewire.com/what-is-a-data-packet-3426310<ref>https://www.lifewire.com/what-is-a-data-packet-3426310</ref>)
== A diagram of a packet ==
[[File:Ip header.jpg]]


== Looking for a basic introduction to packets ?==
== Looking for a basic introduction to packets ?==


* https://www.youtube.com/watch?v=xIuBmOufbls
* https://www.youtube.com/watch?v=xIuBmOufbls
<html>
<iframe width="560" height="315" src="https://www.youtube.com/embed/ewrBalT_eBM" frameborder="0" allowfullscreen></iframe>
</html>
<br /><br />
<html>
<iframe width="560" height="315" src="https://www.youtube.com/embed/AEaKrq3SpW8" frameborder="0" allowfullscreen></iframe>
</html>
== Do I understand this? ==
<html>
<iframe src="https://assess.computersciencelearning.org/h5p/31/embed" width="846" height="426" frameborder="0" allowfullscreen="allowfullscreen"></iframe><script src="https://assess.computersciencelearning.org/modules/h5p/vendor/h5p/h5p-core/js/h5p-resizer.js" charset="UTF-8"></script>
</html>
== Skills ==
You should be aware how to capture and view packets. Diagnosing network problems via packet analysis is '''not within the scope of IB Computer Science''', but you should be able to view a network packet. The de-facto tool for this stuff is [https://www.wireshark.org/ wireshark]. It will take you many hours to learn how to use wireshark.


OS X : <syntaxhighlight inline lang="bash">nettop -m tcp</syntaxhighlight>


== What do you actually NEED to know? ==
OS X / Linux : <syntaxhighlight inline lang="bash">sudo tcpdump -nnSX port 443</syntaxhighlight>


*[[3.1.3 Describe how communication over networks is broken down into different layers. Level: 2]]
OS X / Linux: <syntaxhighlight inline lang="bash">sudo tcpdump -nnSX port 80</syntaxhighlight> (visit example.com after running this command).
*[[3.1.6 Define the terms: protocol, data packet. Level: 1]]
*[[3.1.11 Explain how data is transmitted by packet switching. Level: 3]]


tcpdump is a complex and powerful tool to view packets. There is a superb website to learn more about this, [https://danielmiessler.com/study/tcpdump/ you can request by clicking this link]


== Standards ==


* Define the terms: protocol, data packet


== References ==
== References ==

Revision as of 10:48, 6 January 2020

Networks[1]

A packet is a basic unit of communication over a digital network. A packet is also called a datagram, a segment, a block, a cell or a frame, depending on the protocol used for the transmission of data. When data has to be transmitted, it is broken down into similar structures of data before transmission, called packets, which are reassembled to the original data chunk once they reach their destination.

The structure of a packet depends on the type of packet it is and on the protocol. Normally, a packet has a header and a payload.

The header keeps overhead information about the packet, the service, and other transmission-related data. For example, data transfer over the Internet requires breaking down the data into IP packets, which is defined in IP (Internet Protocol), and an IP packet includes:

  • The source IP address, which is the IP address of the machine sending the data.
  • The destination IP address, which is the machine or device to which the data is sent.
  • The sequence number of the packets, a number that puts the packets in order such that they are reassembled in a way to get the original data back exactly as it was prior to transmission.
  • The type of service
  • Flags
  • And some other technical data
  • The payload, which represents the bulk of the packet (all the above is considered as overhead), and is actually the data being carried.

(Above used with gratitude from: https://www.lifewire.com/what-is-a-data-packet-3426310[2])

A diagram of a packet[edit]

Ip header.jpg

Looking for a basic introduction to packets ?[edit]



Do I understand this?[edit]


Skills[edit]

You should be aware how to capture and view packets. Diagnosing network problems via packet analysis is not within the scope of IB Computer Science, but you should be able to view a network packet. The de-facto tool for this stuff is wireshark. It will take you many hours to learn how to use wireshark.

OS X : nettop -m tcp

OS X / Linux : sudo tcpdump -nnSX port 443

OS X / Linux: sudo tcpdump -nnSX port 80 (visit example.com after running this command).

tcpdump is a complex and powerful tool to view packets. There is a superb website to learn more about this, you can request by clicking this link

Standards[edit]

  • Define the terms: protocol, data packet

References[edit]