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Technical Security : Packets
Before diving into the details of the Internet and networks in general, we need to cover a few bona fide propeller-head concepts. Today, it's packets. Future posts will cover headers, ports, and MAC addresses.
Packets
Just as a drop is the basic unit of a rain shower, or a car is the basic unit of a traffic jam, a packet is the basic unit of Internet (actually, any network) traffic.
When anything is sent over the Internet—be it an email message urging you to complete your overdue action item or the contents of a web page promising to teach you the real estate investment secrets of the rich and famous—that “thing” is broken into manageable chunks called “packets.” As the information is tidied up and readied for transmission, it undergoes a series of steps which prepare it for the journey. It is encrypted, if necessary. The source and destination addresses are added. Ultimately it is broken down into electrical pulses which are sent across a wire, or into photons sent across a fiber. Of course this isn’t the full story. I’ve left out a few details so you wouldn’t run screaming into the street and throw this book into the nearest sewer. But, in actuality, these are just a few of the many steps which take place behind the scenes. At each stage, information specific to that step is added to a header portion of the packet. Think of this header as being akin to a shipping manifesto for a big hunk of cargo being sent from New Jersey to Zambia. The “shipper,” as it is called, contains information about the sender, the receiver, any special details (e.g. “hazardous materials,” “toxic waste,” or “radioactive”) and the quantity of items scheduled for transport.
Having said “packet” half a dozen times, note that technically speaking, the term “packet” may or may not be accurate. Based on where it is in the process, the chunk actually could be properly called a “stream” or “message” or “segment” or “datagram” or “frame.” But it is common to use the word “packet” to refer to the package of information which is built up via these step-by-step or, to use the proper term, layer-by-layer additions to the header—a process called encapsulation—and then sent over a network.
Packets
Just as a drop is the basic unit of a rain shower, or a car is the basic unit of a traffic jam, a packet is the basic unit of Internet (actually, any network) traffic.
When anything is sent over the Internet—be it an email message urging you to complete your overdue action item or the contents of a web page promising to teach you the real estate investment secrets of the rich and famous—that “thing” is broken into manageable chunks called “packets.” As the information is tidied up and readied for transmission, it undergoes a series of steps which prepare it for the journey. It is encrypted, if necessary. The source and destination addresses are added. Ultimately it is broken down into electrical pulses which are sent across a wire, or into photons sent across a fiber. Of course this isn’t the full story. I’ve left out a few details so you wouldn’t run screaming into the street and throw this book into the nearest sewer. But, in actuality, these are just a few of the many steps which take place behind the scenes. At each stage, information specific to that step is added to a header portion of the packet. Think of this header as being akin to a shipping manifesto for a big hunk of cargo being sent from New Jersey to Zambia. The “shipper,” as it is called, contains information about the sender, the receiver, any special details (e.g. “hazardous materials,” “toxic waste,” or “radioactive”) and the quantity of items scheduled for transport.
Having said “packet” half a dozen times, note that technically speaking, the term “packet” may or may not be accurate. Based on where it is in the process, the chunk actually could be properly called a “stream” or “message” or “segment” or “datagram” or “frame.” But it is common to use the word “packet” to refer to the package of information which is built up via these step-by-step or, to use the proper term, layer-by-layer additions to the header—a process called encapsulation—and then sent over a network.
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