DDSI-RTPS 2.3 RTF Avatar
  1. OMG Issue

DDSIRTP23 — Incorrect definition of SequenceNumberSet

  • Key: DDSIRTP23-37
  • Status: closed  
  • Source: Real-Time Innovations ( Dr. Gerardo Pardo-Castellote, Ph.D.)
  • Summary:

    Section (SequenceNumberSet)

    Specifies that

    A valid SequenceNumberSet must satisfy the following conditions:
    • bitmapBase >= 1
    • 0 < numBits <= 256
    • there are M=(numBits+31)/32 longs containing the pertinent bits

    This is seems like an error in how the spec is worded.
    What it was trying to say is that for the bitset to represent a set f bits then it must be that 0 < numBits <= 256

    However the case with numBits=0 is still valid. It represents an empty set, but the bitmapBase still carries information since. This is use by the ACKNAK sub-message to acknowledges al sequence numbers less or equal to bitmapBase without Nacking anything.

  • Reported: DDSI-RTPS 2.2 — Wed, 30 Mar 2016 20:21 GMT
  • Disposition: Resolved — DDSI-RTPS 2.3
  • Disposition Summary:

    *Update SequenceNumberSet definition to explicitly allow 0-bits *

    The current definition of the SequenceNumberSet requires at least 1 bit in the bitset but there are use cases where 0 bits are needed so the definition will be updated.

  • Updated: Wed, 19 Dec 2018 16:38 GMT