Description
Calculate the first SACK block's modular span and the backward distance from its right edge to the cumulative acknowledgment.
TCP sequence and timestamp fields wrap in a 32-bit space. A modular distance gives a local displacement; ordering near half the space and multiple wraps requires additional context.
Calculate the first SACK block's modular span and the backward distance from its right edge to the cumulative acknowledgment.
When to use this tool
Use TCP Sack Duplicate Block Order Classifier when you need a bounded sequence-space distance or interval relationship.
How to use the tool and how it works
- Enter firstLeft, firstRight, cumulativeAck. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read belowAck, validBlock. Inspect belowAck, validBlock before interpreting the associated values.
Calculate the first SACK block's modular span and the backward distance from its right edge to the cumulative acknowledgment. A block is valid only for a span in (0, 2^31); belowAck additionally requires both backward and combined distances below 2^31.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| firstLeft | First Left | Required. Safe integer. |
| firstRight | First Right | Required. Safe integer. |
| cumulativeAck | Cumulative Ack | Required. Safe integer. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| belowAck | Below Ack | Required. Boolean. |
| validBlock | Valid Block | Required. Boolean. |
{
"input": {
"firstLeft": 100,
"firstRight": 120,
"cumulativeAck": 150
},
"output": {
"belowAck": true,
"validBlock": true
}
}Limitations and assumptions
- Only the supplied first block is classified; a full duplicate-SACK or option-order analysis requires additional context.
- 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
Combine sequence arithmetic with connection state, packet chronology, and explicit wrap epochs where available.
References
Similar or alternative tools
- TCP Sack Block Relative Span
Compute (right - left) modulo 2^32 and require a strictly positive span below 2^31.
- TCP Retransmission Sequence Overlap
Place secondStart within a signed half-space of firstStart, reject the exact half-space tie, and intersect the resulting half-open intervals.