IEEE 802.3 Frame Format

IEEE 802.3 Frame Format

Preamble SFD DA SA LEN LLC PAD FCS

7 1 2, 6 2, 6 2 4 位元組

I/G

I/G

U/L

15-位元地址

46-位元地址

I/G = 0 Individual Address （個別地址）

I/G = 1 Group Address （群體地址）

U/L = 0 Globally Administered Address （整體性地址）

U/L = 1 Locally Administered Address （區域性地址）

• Preamble: (101010...1010) for Synchronization
• SFD: Start Frame Delimiter (10101011)
• DA: Destination Address
• SA: Source Address
• Length: Length of LLC-Frame
• LLC-Frame: Up to 1500 bytes
• PAD: Padding when LLC-Frame < 46 bytes
• FCS: Frame Check Sequence (CRC-32)
• MAC-frame size -- from DA to FCS
  • Min 64 bytes to distinguish from collision
  • Max 1518 bytes to prevent dominating bandwidth

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