What is the purpose of the preamble in an Ethernet frame?
Synchronization, Bit-stuffing removal, Wake-up signal
The preamble in an Ethernet frame serves three main purposes:
1. Synchronization: The preamble acts as a synchronization signal to alert the receiving device that a frame is about to be transmitted. It consists of a pattern of alternating 1s and 0s (101010…), which allows the receiving device to synchronize its clock with the sender’s clock.
2. Bit-stuffing removal: The Ethernet standard allows for bit-stuffing, which is the process of adding an extra 0 bit after every sequence of 5 consecutive 1 bits in the data. The preamble provides a known pattern (101010…) that helps the receiver locate the start of the frame and remove any bit-stuffing that may have been added during transmission.
3. Wake-up signal: In some cases, the preamble can also serve as a wake-up signal to activate a network interface. For example, in power-saving modes, network devices may temporarily disable their network interface to conserve power. When a device receives a preamble, it can use that as a trigger to activate its network interface and start receiving the frame.
In summary, the preamble in an Ethernet frame provides synchronization, assists with bit-stuffing removal, and can act as a wake-up signal for network devices.
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