A data preamble or preamble is a signal that is placed in front of messages transmitted in a computer network. Depending on the network protocol , the preamble serves different purposes: In some it is used to synchronize the communicating parties and to synchronize the clock (see Ethernet ), in others it announces the following message (see Wise Media Access Control ).
In contrast to the header of a data packet , the preamble is not part of the data itself, but is used to coordinate the conversation partners in the network. In the case of message announcement, the preamble consists of a constant signal; in the case of synchronization, it consists of a firmly agreed sequence of bits . In the case of serial transmission, the preamble or its end is often followed by a specific bit sequence that announces the start of the actual data and enables synchronization to the word boundary (e.g. start of frame with Ethernet).
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- Preamble (accessed July 21, 2017)