Subject: [6tisch] Reuse MAC ack vs 6top ack when using block option

From: "Raghuram Sudhaakar (rsudhaak)" <[email-masked]>
Date: Fri, 9 May 2014 22:48:32 +0000

All,
In the meeting this morning we discussed the issue of reusing the MAC layer ack for the CoAP blocks (when using block option). The discussion centered around the efficiency of using the MAC layer ACK vs the separation/reliability of using an ack at the 6top layer.

The other pros/cons discussed were
1)MAC layer ack may not be available/lost in situations wherein the device may drop packets due to congestion/other errors.
2)There is a very short turnaround time between the reception of a packet and the transmission of the ACK at the mac layer (~192us). This may be very short time to process the CoAP message and respond as necessary.
3) Usage of extended may be a possibility
4) An ideal tradeoff may be to use a 6top ACK for the entire payload and use the MAC ack for the ARQ of individual blocks.

I request comments/opinions on this topic from the group that will help us reach the best tradeoff/solution.

-raghuram