Qin, you are pointing out that the bandwidth must be already provided if one wants to use the Frame Pending setting. This is what we have discussed in the past and is the state of the art in 6tisch.
Michele is proposing to use the Frame Pending jointly with a temporary cell reservation in the ACK. I guess this is not in the scope of OTF, but, in case, in that of 6top-to-6top. Why? Currently 6top-to-6top could be used for allocating cells through a negotiation: 1. mote A sends a reservation request to mote B in a cell, and that signaling packet is unicast, so acknowledged in the same cell by B 2. mote B answers A with a reservation response in a following cell, which is also a unicast packet acnowledged in that same cell Michel is saying: 1. mote A sends a Frame Pending to B in a cell, and B sends the ack to A in the same cell answering with a temporary allocation So, Michel's proposal uses 1 cell to perform the negotiation that 6top does (in the current version) by using 2 cells. I guess this is the reason for defining this approach reactive. At the same time, the current 6top negotiation allows to exchange more information for reserving a common available cell. In Michel's approach I figure out many cases of failures: what happens if the temporary cell given by B to A was already busy in A (it was already part of the A's schedule, but with another neighbor, say C)? I guess A will not be able to free its memory, so leading to congestion. Right? Nicola 2015-07-01 10:09 GMT-07:00 Michel Veillette < [email protected]>: > Hi Qin > > > > Yes, the Frame Pending flag is defined as follow: > > > > IEEE 802.15.4-2006 section 7.2.1.1.3 > > “Frame Pending subfield is 1 bit in length and shall be set to one if the > device sending the frame has more data for the recipient. This subfield > shall be set to zero otherwise” > > > > This feature can be especially useful for the upstream traffic in a RPL > DODAG. In a scenario where a DAG parent have dozens of children, dedicated > timeslot will be infrequent and share timeslots suffer from contention. If > a subset of these children have ongoing traffic, the parent can use the > Frame Pending flag information to schedule temporary soft cells and avoid > contention or speedup transfer. > > > > > > [image: cid:[email protected]] > > Michel Veillette > System Architecture Director > > Trilliant Inc. > Tel: 450-375-0556 ext. 237 > [email protected] > > www.trilliantinc.com > > > > > > *From:* Qin Wang [mailto:[email protected]] > *Sent:* 1 juillet 2015 11:28 > *To:* Nicola Accettura; Michel Veillette > *Cc:* [email protected]; [email protected] > *Subject:* Re: [6tisch] draft-dujovne-6tisch-on-the-fly-05 > > > > Hi Michel and Nicola, > > > > I think Michel's idea is interesting. But, according to my understanding, > the Frame Pending setting just means there is frame following, does not > mean that the current bandwidth provided by TSCH schedule, including hard > cells and soft cells, is not enough to convey those frames, and then needs > more bandwidth (e.g. additional soft cells) . Right? Do I miss something? > > > > Thanks > > Qin > > > > > > On Wednesday, July 1, 2015 4:03 AM, Nicola Accettura < > [email protected]> wrote: > > > > Hi Michel, > > your proposal is very interesting. > > However, OTF does not allocate cells directly: it just computes the > estimated number of cells to add or delete into the schedule, and then > sends this information to 6top. 6top is then in charge of negotiating cells > among neighbors, and meybe perform the scheme you are proposing. > > So, your proposal seems fitting more the 6top-to-6top communication. > > Am I missing something? What others think about? > > Sincerely > > Nicola > > > > 2015-06-30 8:13 GMT-07:00 Michel Veillette < > [email protected]>: > > Hi Diego > > > > It’s my first reading of the “6TiSCH On-the-Fly Scheduling” (and I’m not > completely done yet) and I wandering if the concept of on the fly, in a > single exchange, temporary allocation of a soft cell have already been > discussed. For example, a node can use the Frame Pending subfield (IEEE > 802.15.4-2006 section 7.2.1.1.3) to indicate the presence of packets ready > to be transmitted. Based on that knowledge, the target may add an IE in an > enhanced acknowledgment to allocate a temporary soft cell (e.g. single > cell). Each subsequent transmission may further re-allocate a temporary > soft cell. It’s important to note that the default delay for a TSCH > Acknowledgment is 1ms (macTsTxAckDelay) which seem sufficient for the > processing of this new IE. > > > > > > > > This scheme is very reactive and may help dealing with non-predictable > communication patterns. > > What do you things? > > > > Michel Veillette > System Architecture Director > > Trilliant Inc. > Tel: 450-375-0556 ext. 237 > [email protected] > > www.trilliantinc.com > > > > > > > _______________________________________________ > 6tisch mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/6tisch > > > > > > _______________________________________________ > 6tisch mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/6tisch > > >
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