DDSIRTP23 — Incorrect definition of SequenceNumberSet

Section 9.4.2.6 (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.

*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.