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Question of the Day
If you were to design a network, what attributes or properties would you want the network to exhibit? How would you accomplish these?
Assigned Reading
Chapter 10
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The syntax of a network protocol is the structure used in communicating information, such as the formatting of data and control information. Consider the transport control protocol or a.k.a. TCP as an example:
<tcp header image>
Lexicon
The lexicon of a network protocol is the collection of valid entries within the structure of the syntax. The lexicon is in other words, the vocabulary of the protocol. Continuing our TCP example, the TCP lexicon dictates that of the possible TCP flags, xor(RST, SYN, FIN) should be in a TCP header.
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Note that some protocols also use a trailer at the end of the payload, such as Ethernet, which includes a trailing checksum.
f
When a network protocol belonging to a higher layer is implemented and placed within the data or payload of a lower layer network protocol, the higher layer protocol is said to be encapsulated within the lower layer. As such, a network protocol, if encapsulated is both a payload and a header + data. It is the payload of the layer below it and it is itself a network protocol with separate header and data.
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