* Question
What constitutes the structure of a short frame?
* Answer
The structure of a short frame depends on the communication protocol being used. However, in general, a short frame consists of a minimal set of essential fields necessary for effective data transmission. Below is a typical structure of a short frame in networking and telecommunications:
1. Preamble
- A sequence of bits (often 7 to 8 bytes) used for synchronization between sender and receiver.
- Ensures that the receiving device can detect and lock onto the transmission.
2. Start of Frame Delimiter (SFD)
- 1 bytethat marks the beginning of the actual frame.
- Helps the receiver identify where the frame starts.
3. Addressing Fields
- Source Address: Identifies the sender.
- Destination Address: Identifies the intended recipient.
- Length of address fields varies by protocol (e.g., MAC addresses in Ethernet are 6 bytes each).
4. Control Field
- Contains protocol-specific control information.
- Used for error detection, flow control, or priority settings.
- The length can vary (typically 1-2 bytes).
5. Payload (Data Field)
- The actual data being transmitted.
- In a short frame, this field is small(could be just a few bytes).
6. Frame Check Sequence (FCS) or Cyclic Redundancy Check (CRC)
- Error-detectionfield to check for corrupted data.
- Typically 2 to 4 bytes.
Example of Short Frame (Ethernet)
In IEEE 802.3 Ethernet, a short frame must be at least 64 bytes (including all headers and FCS). If data is too small, padding bytes are added to meet this minimum size.
Common Examples of Short Frames
IEEE 802.15.4 (ZigBee, IoT) Short Frame:
- Preamble (2 bytes)
- Frame Control (2 bytes)
- Addressing (varies)
- Payload (short)
- CRC (2 bytes)
HDLC Short Frame:
- Flag (1 byte)
- Address (1 byte)
- Control (1 byte)
- Payload (short)
- FCS (2 bytes)
- Flag (1 byte)
A short frame typically has a limited payload and is used for control messages, acknowledgments, or minimal data exchange in constrained environments.
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