1.12 Last Two Bits
Type-Length-Value:
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This concept is used in headers of protocol headers as well as the body of a packet, and by different layers of a networking the source and the other for the destination. |
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First, for each receiving end to interpret properly, the source and the destination address must be listed in the same order in the header. |
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Second, such information has a well-defined structure: it is of a certain type (IP address, in this case), it is of certain length (32 bits in this case), and it contains a value (the actual IP address). |
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In many instances, the length may vary, or the type is preferred to be left open for future extensions of a protocol. |
Network Protocol Analyzer:
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Packet formats for networking protocols are described in standards documents by respective standards bodies. |
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Many details about what a protocol can do lie in the header of a packet. Just by looking at a packet format and reading a standards document, it is still difficult to grasp. |
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Network protocol analyzers are used to capture packets from live networks. By studying headers captured through such analyzers, it is often easier to understand a packet header, and more important, a protocol. |
