SFD

SFD is an acronym used in several different domains, and its meaning depends on the context. The term does not have a single universal definition, but one well-established usage appears in networking and telecommunications.

In Ethernet networking, SFD stands for Start Frame Delimiter. It is a specific field in Ethernet frames that follows the preamble. In IEEE 802.3 framing, a sequence begins with seven bytes of 0x55 (the preamble) and is followed by a Start Frame Delimiter byte of 0xD5, after which the frame payload begins. The SFD helps receivers synchronize to the incoming signal and delineate the start of the frame, supporting correct timing interpretation and error detection during data transmission.

Outside of networking, SFD is used as an acronym in various other contexts, often as organization- or domain-specific shorthand. Because there is no universal standard for these usages, the intended meaning of SFD must be inferred from the surrounding material, source, and field. In practice, readers should rely on contextual clues such as the subject area, technical documentation, or accompanying terminology to determine which phrase the acronym represents in a given case.

Overall, SFD most reliably refers to the Start Frame Delimiter in Ethernet terminology, while other meanings exist in different professional or community contexts.