#394 Statistics of missed PD packets when publisher restarts

[Kari Keinanen]

numMissed counter of statistics is "unusable" if publisher restarts.

Use case:

• missed frames = 0, everything is OK
• publisher sends sequence counter=1
• subscriber receives sequence counter=1
• publisher restarts
• publisher sends sequence counter=0
• subscriber expects sequence counter=2, but gets 0
• (TCNOpen 2.1.0.0) trdp_pdcom.c:902 numMissed += UINT32_MAX - curSeqCnt + newSeqCnt;
• this means numMissed is increased with 4294967294

Proposal:

• if received frame has sequence counter < current sequence counter, current sequence counter could be set to 0 before comparing values
• this is not bullet-proof and does not handle all corner cases exactly right way (which in practice might be challenging), but provides better value for application

Any comments ?

Best regards, Kari

[Kari Keinanen]

Could we just remove following code lines (900-903) from trdp_pdcom.c ?

900 else if (pExistingElement->curSeqCnt > newSeqCnt)
901 {
902 pExistingElement->numMissed += UINT32_MAX - pExistingElement->curSeqCnt + newSeqCnt;
903 }

And expect that receiving sequence counter value less than previous one means that publisher has restarted.

[Chris Wetzler]

At revision: 2350