Description
Subtract the fixed eight-byte header from udpLength, which must be an integer from 8 through 65535.
A UDP checksum word and the UDP length field serve different purposes: one detects corruption, while the other counts header plus payload bytes. IP version affects checksum policy.
Subtract the fixed eight-byte header from udpLength, which must be an integer from 8 through 65535.
When to use this tool
Use Network: UDP Length Payload Crosswalk when you need to inspect a supplied UDP length or checksum convention.
How to use the tool and how it works
- Enter udpLength. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read result. Expand result to inspect the returned fields.
Subtract the fixed eight-byte header from udpLength, which must be an integer from 8 through 65535. Return payloadBytes.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| udpLength | Udp Length | Required. Safe integer. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| result | Result | Required. Object. |
| result.payloadBytes | Payload Bytes | Calculated result member: number. |
{
"input": {
"udpLength": 12
},
"output": {
"result": {
"payloadBytes": 4
}
}
}Limitations and assumptions
- This ordinary length-field calculation does not handle IPv6 jumbogram conventions or inspect a datagram.
- Outputs are nested inside result. Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use packet capture and a complete datagram checksum verifier for end-to-end validation.
References
Similar or alternative tools
- UDP Checksum Negative Zero Transmit Word
Accept a computed 16-bit checksum and replace zero with 65535; return every other word unchanged.
- Network: UDP Zero Checksum Version Policy
Check IP version 4 or 6 and a 16-bit checksum.