Description
Add offsetUnits × 8 to payloadBytes and reject an exclusive end beyond 65515.
A wire-format length may count headers, payload, padding, or only part of an enclosing message. Offsets and exclusive ends must use a clearly stated byte convention.
Add offsetUnits × 8 to payloadBytes and reject an exclusive end beyond 65515.
When to use this tool
Use IPv4 Fragment Last Payload Boundary when you need a field-level byte count or boundary check.
How to use the tool and how it works
- Enter offsetUnits, payloadBytes, moreFragments. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read endExclusive, lengthAligned. Inspect lengthAligned before interpreting the associated values.
Add offsetUnits × 8 to payloadBytes and reject an exclusive end beyond 65515. Set lengthAligned when this is the final fragment or the payload length is divisible by eight.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| offsetUnits | Offset Units | Required. Safe integer; minimum 0; maximum 8191. |
| payloadBytes | Payload Bytes | Required. Safe integer; minimum 0; maximum 65515. |
| moreFragments | More Fragments | Required. Boolean. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| endExclusive | End boundary excluded from the represented span. | Required. Safe integer. |
| lengthAligned | Length Aligned | Required. Boolean. |
{
"input": {
"offsetUnits": 3,
"payloadBytes": 10,
"moreFragments": false
},
"output": {
"endExclusive": 34,
"lengthAligned": true
}
}Limitations and assumptions
- A false alignment flag is a successful diagnostic result. This does not detect gaps, overlap, or inconsistent fragments.
- 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
Compare the computed span with the actual captured buffer and validate its contents separately.
References
Similar or alternative tools
- Network: IPv4 Fragment Offset Byte Position
Multiply fragmentOffset in 0-8191 by eight to obtain the byte offset within the original payload.
- Network: IPv4 Header Flags Df Mf Pair
Decode the three-bit flags field into reservedSet, dontFragment, and moreFragments.