yǐ tài wǎng / zhēn / de / zhēn shǒu dìng jiè fú / yòng yú / zhǐ shì / zhēn / de / kāi shǐ / wèi zhì以太网帧的帧首定界符用于指示帧的开始位置。The start frame delimiter in an Ethernet frame indicates the beginning of the frame.