DDSIRTP2 — Clarify implementing Count submessage element

Source:
Real-Time Innovations, Inc. (Ken Brophy, ken@rti.com)
Summary:
The use of the count submessage element is not fully explained.

For heartbeats, the Count element differentiates logical heartbeats, so heartbeats with the same count as a previously received heartbeat can be ignored to prevent triggering duplicate repair sessions. Also, old heartbeats with count less than previously received counts should also be ignored. So, same logical heartbeats must not have the same count, and new heartbeats must have greater counts than older heartbeats.

The same logic applies to counts of ACKNACKs.

Resolution:
Explain proper usage of the count element of Heartbeats and ACKNACKs.

Revised Text:
Add new section:

8.4.14.6 Setting Count of Heartbeats and ACKNACKs
The count element of Heartbeats differentiates logical heartbeats. A received heartbeat with the same count as a previously received heartbeat can be ignored to prevent triggering a duplicate repair seesion. So, an implementation should ensure same logical heartbeats are tagged with the same count.

Also, new heartbeats should have counts greater than all older heartbeats. Then, received heartbeats with counts less than or equal to any previously received can be ignored.

The same logic applies for counts of ACKNACKs: each logical ACKNACK

see above