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The frame format specified by IEEE 802.3 standard contains following fields
- Preamble: It is seven bytes (56 bits) that provides bit synchronization. It consists of alternating Os and 1s. The purpose is to provide alert and timing pulse.
- Start Frame Delimiter (SFD): It is one byte field with unique pattern: 10 10 1011. It marks the beginning of frame.
- Destination Address (DA): It is six byte field that contains physical address of packet’s destination.
- Source Address (SA): It is also a six byte field and contains the physical address of source or last device to forward the packet (most recent router to receiver).
- Length: This two byte field specifies the length or number of bytes in data field.
- Data: It can be of 46 to 1500 bytes, depending upon the type of frame and the length of theinformation field.
- Frame Check Sequence (FCS): This for byte field contains CRC for error detection.
CSMA/CD Procedure:
Fig. Shows a flow chart for the CSMA/CD protocol.
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