Hi Nicola and Diego,
Since we agree Timeout is needed no matter what schemes we will choose, let's
make calculation about the Timeout in different schemes. Assume:t1: Node A 6top
prepares ADD Requestt2: Node A 6top sends out ADD Request, ending with MAC-ACK
successt3: Node B 6top processes ADD Requestt4: Node B SF0 processes ADD
Requestt5: Node B 6top prepares ADD Responset6: Node B 6top sends out ADD
Response, ending with MAC-ACK successt7: Node A 6top processes ADD Response.t8:
Node A 6top sends out 6P ACK, ending with MAC-ACK successt9: Node B 6top
processes 6P ACK
According to my understanding, the most unpredictable time is t2, t6 and t8,
because they are associated with Retry and the length of slotframe. Assume slot
duration is 10ms and slotframe length is 101, maxRetry is 3, then, t2 and t6
could be 3 seconds, and t8 could be 3 seconds also if Shared cell is used.
(1) Current scheme. Timeout starts when SF0 on node A issues command to 6top to
ask ADD cells. Then the value of Timeout is function of (t1,..t7)
(2) Diego's scheme. Timeout starts when SF0 on node A gets MAC-ACK success from
6top. Then the value of Timeout is function of (t3,..t7)(3) Nicola's scheme.
(I'm not sure the formula to calculate the value of Timeout. But my feeling is
each Timeout has to include at least one long and unpredictable Time, i.e. t2,
or t6, Nicola: would you please add it?)
Comparing (1) and (2), I agree that (2) is much better than (1), because (2)
does not take t2 into account in (2), reducing almost half of uncertainty.
I haven't figured out the advantage of (3) over (2). Nicola, would you please
give me your explanation?
ThanksQin
On Monday, October 31, 2016 2:18 PM, Nicola Accettura
<nick.accett...@gmail.com> wrote:
Hi Diego,
thank you for your answer too.
However there are two points I would like to point out.
First, the mac-layer ack is in fact the TSCH ack, that travels on the air
during the same timeslot of the data packet. It is sent if the data packet is
unicast, either on shared or on dedicated cells. The 6P ACK I'm proposing is
NOT a TSCH ack, it is a data packet sent from A to B and it requires its own
TSCH ack from B to A.
Second, I'm totally not aligned on "...dedicated cells are for data and shared
cells for any kind of signalling and/or negotiation." and I believe this is not
the distinction between those types of cells.
Shared or dedicated cells can be used either for signaling and/or data.
'Minimal'. as an example, has got a single shared cell. One can run minimal
without any other more sophisticated scheduling technique just using that
shared cell for both signaling and data. The same is possible if someone uses a
dynamic schedule and uses also dedicated cells. I don't see any reason for
forbidding dedicated cells to vehiculate both signaling and data. The
difference is that in shared cells there's contention.
I would add that it could be possible to piggyback 6P signaling with data from
upper layers, if there is space in the MTU. It is the encapsulation that makes
the distinction between data and 6P signaling. Data go encapsulated within the
IEEE802.15.4e packet payload, while 6P goes into the payload IEs, and these two
payloads can coexist in the same IEEE802.15.4e frame.
Thoughts?
Nicola
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