Re: [6tsch] On the fly scheduling
Guillaume Gaillard <guillaume.gaillard.maze@gmail.com> Fri, 04 October 2013 15:07 UTC
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Date: Fri, 04 Oct 2013 17:03:41 +0200
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From: Guillaume Gaillard <guillaume.gaillard.maze@gmail.com>
To: Qin Wang <qinwang@berkeley.edu>
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Cc: 6TSCH <6tsch@ietf.org>
Subject: Re: [6tsch] On the fly scheduling
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Hi Qin, It makes sense for me, Guillaume 2013/10/4 Qin Wang <qinwang@berkeley.edu> > Hi Guillaume, > > I would like to keep the algorithm (4) open, something like Objective > Function in RPL. Make sense? > > Qin > > > On Fri, Oct 4, 2013 at 10:54 PM, Guillaume Gaillard < > guillaume.gaillard.maze@gmail.com> wrote: > >> Hi Qin and all, >> >> I agree with your separation into two tools (pre-allocation vs >> post-allocation). When one wants to meet a new QoS requirement, it is >> possible: >> - (1) to over-provision cells in the schedule in order to be "sure" to >> meet the requirement (pre-allocation); >> - (2) to adapt the cell allocation to the variations of the network >> parameters (post-allocation); >> - (3) to do both things. >> >> When solution (2) is adopted, one should tolerate a time of degraded QoS, >> before the requirement is restored. >> >> I agree on your list of mechanisms a solution requires. Is the algorithm >> (4) (matching number of cell with QoS requirements) implementation-specific >> ? >> >> Regards, >> >> Guillaume Gaillard >> >> Orange Labs Meylan/CITI INRIA-INSA Lyon >> PhD student "SLA pour Réseaux de Capteurs Multi-Services" >> Advisors D. Barthel, F. Valois, F. Theoleyre >> >> >> >> 2013/10/4 Qin Wang <qinwang@berkeley.edu> >> >>> Hi Pascal and all, >>> >>> It is a interesting approach. I would like to put different approaches >>> above together. >>> >>> Objective: meet some QoS requirement. >>> Tool 1: pre-allocation, like what Pascal suggested, assign number of >>> cells to a bundle, and on/off them on demand. >>> Tool 2: post-allocation, like discussed in other emails in this thread, >>> adjust the number of cells in a bundle according to statistics information. >>> >>> In reality, I think a mote may use the combination of tool 1 and tool 2, >>> e.g. at the beginning, mote allocates some cells for a bundle, and use them >>> in the mode of on/off on demand; when statistics information show 2 more >>> cells needed, then mote is triggered to allocates 3 more cells for the >>> bundle, and then also use them in the mode of on/off on demand. >>> >>> If it is the case, a solution should include the the following parts: >>> (1) mechanism to create/delete softcells >>> (2) mechanism to provide statistics information >>> (3) mechanism to on/off cell on demand >>> (4) algorithm to determine how many cells needed for a QoS requirement >>> like (dataflow/burst-feature, delay-tolerance, {statistics info}, ...) >>> >>> What do you think? >>> >>> Qin >>> >>> >>> >>> >>> On Fri, Oct 4, 2013 at 5:30 PM, Pascal Thubert (pthubert) < >>> pthubert@cisco.com> wrote: >>> >>>> Dear all:**** >>>> >>>> ** ** >>>> >>>> Statistics and hysteresis can be costly in terms of memory and CPU, may >>>> not be the best strategy to address bursts of traffic in a stochastic IP >>>> network, and the strategy to derive the allocation from the past >>>> observation may be hard to determine in a particular case and even harder >>>> to generalize.**** >>>> >>>> ** ** >>>> >>>> The needs of bandwidth may be very dynamic for instance in the case of >>>> alarms/alerts, or in the case of a brutal variation of monitored data. >>>> Changes in the network topology impacting the rank of a node within the DAG >>>> may also impact brutally its needs of bandwidth. So we cannot only rely on >>>> past observations and but also need to maintain some capabilities that rely >>>> on current needs that operate efficiently in terms of control and yet very >>>> dynamically to accept both brutal bursts of traffic and longer term >>>> variations.**** >>>> >>>> ** ** >>>> >>>> Considering that we have ample room in a SlotFrame, a simple strategy, >>>> derived from traditional memory management, could be to augment the number >>>> of cells in a bundle each time it is saturated. As an image, GNU’s obstack >>>> seem to grow linearly one chunk at a time, but I know of chunk >>>> implementations that double the size of a dynamic chunk each time it is >>>> saturated and a geometrical growth may a better approach for us. **** >>>> >>>> ** ** >>>> >>>> In a bundle, a portion of the cells is always on. The rest can stay >>>> idle (no wake to send or listen) unless a previous cell indicates that >>>> there is more to come. If we agree on a strategy like this then we can >>>> start working out the details, in particular how handle lazy release or >>>> one-shot override, how we observe unallocated slots to make them candidate >>>> for allocation, etc...**** >>>> >>>> ** ** >>>> >>>> As you see, even implementing such a simple strategy can already be >>>> quite some work in a constrained device. **** >>>> >>>> ** ** >>>> >>>> Cheers,**** >>>> >>>> ** ** >>>> >>>> Pascal**** >>>> >>>> ** ** >>>> >>>> *From:* 6tsch-bounces@ietf.org [mailto:6tsch-bounces@ietf.org] *On >>>> Behalf Of *Maria Rita PALATTELLA >>>> *Sent:* vendredi 4 octobre 2013 09:19 >>>> *To:* Thomas Watteyne; 6TSCH >>>> >>>> *Subject:* Re: [6tsch] On the fly scheduling**** >>>> >>>> ** ** >>>> >>>> +1 for me too.**** >>>> >>>> ** ** >>>> >>>> For sure, according to the specific requirements of the applications, >>>> different algorithms may be used for building the schedule. But the >>>> functionalities offers by 6top (i.e., collect statist. Info, send commands >>>> for scheduling cells) will be still the same (no matter which algorithm is >>>> used). **** >>>> >>>> ** ** >>>> >>>> The statistics needed could change because different algorithms may use >>>> different input as parameters. So, we will have to include a set of >>>> statistic information, or anyway, make sure it is possible to extend them. >>>> **** >>>> >>>> ** ** >>>> >>>> Maria Rita**** >>>> >>>> ** ** >>>> >>>> ** ** >>>> >>>> ** ** >>>> >>>> *From:* 6tsch-bounces@ietf.org [mailto:6tsch-bounces@ietf.org<6tsch-bounces@ietf.org>] >>>> *On Behalf Of *Thomas Watteyne >>>> *Sent:* Thursday, October 03, 2013 10:11 PM >>>> *To:* 6TSCH >>>> *Subject:* Re: [6tsch] On the fly scheduling**** >>>> >>>> ** ** >>>> >>>> That would indeed be clean.**** >>>> >>>> ** ** >>>> >>>> On Thu, Oct 3, 2013 at 12:33 PM, Qin Wang <qinwang@berkeley.edu> wrote: >>>> **** >>>> >>>> Hi all,**** >>>> >>>> ** ** >>>> >>>> +1 for the proposal. **** >>>> >>>> ** ** >>>> >>>> Regarding to how to approach, I agree with Thomas. There is an entity >>>> running on top of 6top, which reads queue information and other statistics >>>> information from 6top, sends instruction like create/delete softcells to >>>> 6top. I think we can use the design methodology of Objective Function in >>>> RPL, i.e. define the statistics information and the interface to/from 6top, >>>> and leave the specific algorithm open.**** >>>> >>>> ** ** >>>> >>>> What do you think?**** >>>> >>>> ** ** >>>> >>>> Qin **** >>>> >>>> ** ** >>>> >>>> ** ** >>>> >>>> ** ** >>>> >>>> On Fri, Oct 4, 2013 at 12:45 AM, Thomas Watteyne < >>>> watteyne@eecs.berkeley.edu> wrote:**** >>>> >>>> +1 for the proposal.**** >>>> >>>> ** ** >>>> >>>> I believe it could be a very simple and powerful approach. Diego, would >>>> you agree that this can be considered a distributed mechanism sitting on >>>> top of 6top?**** >>>> >>>> ** ** >>>> >>>> That is, 6top provides:**** >>>> >>>> - commands to modify the number of soft cells in a bundle**** >>>> - commands to retrieve usage statistics of the cells/bundles**** >>>> >>>> The way I see it, your proposal consists of an algorithm which feeds >>>> from the usage statistics and triggers changes in the number of soft cells >>>> in a bundle. Correct?**** >>>> >>>> ** ** >>>> >>>> The questions to answer for now is whether 6top provides the right >>>> statistics.**** >>>> >>>> ** ** >>>> >>>> Maria Rita, one big difference with TASA is that OTF scheduling is >>>> distributed.**** >>>> >>>> ** ** >>>> >>>> Thomas**** >>>> >>>> ** ** >>>> >>>> On Thu, Oct 3, 2013 at 9:11 AM, Maria Rita PALATTELLA < >>>> maria-rita.palattella@uni.lu> wrote:**** >>>> >>>> Diego,( all) >>>> >>>> what you are suggesting (i.e., reserve cells based on queue size, >>>> delay) is actually the main idea behind TASA (Traffic Aware Scheduling >>>> Algorithm). >>>> >>>> TASA builds the schedule based on the local (number of pkt generated by >>>> the node) and global queue level ( i.e., local + pkt to be forwarded, >>>> generated by children). It gives priority to nodes with longer queues and >>>> it aims to reduce the latency for delivering the pkt. At the same time >>>> while building the schedule it minimizes the number of scheduled cells in >>>> order to reduce the network duty cycle. >>>> TASA is centralized and thus it assumes that the PCE has all the info >>>> needed for setting up the schedule. in other words, it knows the traffic >>>> generated by each nodes, and the paths followed by each pkt. >>>> With a "on the fly solution", we will not need to know all this info a >>>> priori. but we will use 6top monitoring functions and the control flows >>>> message for scheduling the cells. >>>> >>>> Btw, I agree with all the points raised up by Xavi. We will have to >>>> address his questions. >>>> >>>> And I support Pascal's suggestions about how to deal with bundle. >>>> >>>> Maria Rita**** >>>> ------------------------------ >>>> >>>> *From:* 6tsch-bounces@ietf.org [6tsch-bounces@ietf.org] on behalf of >>>> Pascal Thubert (pthubert) [pthubert@cisco.com] >>>> *Sent:* Thursday, October 03, 2013 4:09 PM >>>> *To:* xvilajosana@eecs.berkeley.edu; Prof. Diego Dujovne**** >>>> >>>> >>>> *Cc:* 6TSCH >>>> *Subject:* Re: [6tsch] On the fly scheduling**** >>>> >>>> ** ** >>>> >>>> +1 too.**** >>>> >>>> **** >>>> >>>> I think that the queue size matters at enqueue but the latency is >>>> really what we care for at dequeue, that is how long did this device keep >>>> this message in queue (even if we are far from **** >>>> >>>> buffer bloat conditions in such a device). If one of the 2 conditions >>>> (size at enqueue, latency at dequeue) is reached then the bundle should be >>>> increased. **** >>>> >>>> **** >>>> >>>> I agree with Xavi that we want to avoid changing the bundle size all >>>> the time. We discussed that with Qin and others earlier on the ML. One way >>>> of increasing the bundle dynamically at a very low cost (not even a >>>> hysteresis) is to have it large amount of cells from the start but used >>>> like 10% by default (xmit/listen happens only once in 10 time slots). A bit >>>> in the frame indicates whether the next (normally unused) slot will indeed >>>> be used. The bit can be present in the data and acked in the ack. This can >>>> also implicitly be triggered for retries.**** >>>> >>>> **** >>>> >>>> Please keep us tuned!**** >>>> >>>> **** >>>> >>>> Cheers,**** >>>> >>>> **** >>>> >>>> PS Note that Cisco has IPR on chaining time slots and flagging whether >>>> the next is used or not. We already declared our IPR against the >>>> architecture draft and provided terms.**** >>>> >>>> **** >>>> >>>> Pascal**** >>>> >>>> **** >>>> >>>> *From:* 6tsch-bounces@ietf.org [mailto:6tsch-bounces@ietf.org] *On >>>> Behalf Of *Xavier Vilajosana Guillen >>>> *Sent:* jeudi 3 octobre 2013 15:46 >>>> *To:* Prof. Diego Dujovne >>>> *Cc:* 6TSCH >>>> *Subject:* Re: [6tsch] On the fly scheduling**** >>>> >>>> **** >>>> >>>> Diego, >>>> >>>> +1**** >>>> >>>> it seems to a me a very interesting idea to explore. Maybe we can start >>>> putting some rules of this mechanism on the table and prepare a simulation. >>>> I am completely in with that idea.**** >>>> >>>> Some questions arise:**** >>>> >>>> 1-how fast do you react to changes on the queue size to avoid >>>> hysteresis -- i.e how do you maintain certain stability in the schedule (so >>>> you don't start installing and removing links very often)**** >>>> >>>> 2-how you map queue size (only one or if more than one queue) to actual >>>> link requirements**** >>>> >>>> 3-how you recover from link collisions in case of multiple nodes >>>> schedule the same cells.**** >>>> >>>> 4-how to decide to who (what neighbor) install more links according to >>>> queue size?**** >>>> >>>> **** >>>> >>>> cheers! >>>> Xavi**** >>>> >>>> **** >>>> >>>> **** >>>> >>>> On Thu, Oct 3, 2013 at 3:23 AM, Prof. Diego Dujovne < >>>> diego.dujovne@mail.udp.cl> wrote:**** >>>> >>>> Dear all, >>>> I've been looking into the idea of "on the fly scheduling", >>>> presented on the Sept 27th webex call as "on-the-fly decentralized >>>> reservation". >>>> The basic mechanism would be based on analysing the queue size >>>> on a node and dynamically adapt the number of reserved >>>> cells to satisfy queue size, delay and/or power >>>> consumption thresholds. >>>> This mechanism would work inside 6top, between pairs of >>>> nodes. >>>> As a first approach, it would be based on the minimal draft. >>>> What do you think on this starting point? >>>> I (gladly) receive comments to add or modify this proposal. >>>> >>>> Diego >>>> >>>> >>>> >>>> >>>> -- >>>> DIEGO DUJOVNE >>>> Académico Escuela de Ingeniería en Informática y Telecomunicaciones >>>> Facultad de Ingeniería UDP >>>> www.ingenieria.udp.cl >>>> (56 2) 676 8125 >>>> _______________________________________________ >>>> 6tsch mailing list >>>> 6tsch@ietf.org >>>> https://www.ietf.org/mailman/listinfo/6tsch**** >>>> >>>> **** >>>> >>>> >>>> _______________________________________________ >>>> 6tsch mailing list >>>> 6tsch@ietf.org >>>> https://www.ietf.org/mailman/listinfo/6tsch**** >>>> >>>> ** ** >>>> >>>> >>>> _______________________________________________ >>>> 6tsch mailing list >>>> 6tsch@ietf.org >>>> https://www.ietf.org/mailman/listinfo/6tsch**** >>>> >>>> ** ** >>>> >>>> ** ** >>>> >>>> _______________________________________________ >>>> 6tsch mailing list >>>> 6tsch@ietf.org >>>> https://www.ietf.org/mailman/listinfo/6tsch >>>> >>>> >>> >>> _______________________________________________ >>> 6tsch mailing list >>> 6tsch@ietf.org >>> https://www.ietf.org/mailman/listinfo/6tsch >>> >>> >> >
- [6tsch] On the fly scheduling Prof. Diego Dujovne
- Re: [6tsch] On the fly scheduling Xavier Vilajosana Guillen
- Re: [6tsch] On the fly scheduling Pascal Thubert (pthubert)
- Re: [6tsch] On the fly scheduling Maria Rita PALATTELLA
- Re: [6tsch] On the fly scheduling Thomas Watteyne
- Re: [6tsch] On the fly scheduling Maria Rita PALATTELLA
- Re: [6tsch] On the fly scheduling Qin Wang
- Re: [6tsch] On the fly scheduling Thomas Watteyne
- Re: [6tsch] On the fly scheduling Maria Rita PALATTELLA
- Re: [6tsch] On the fly scheduling Pascal Thubert (pthubert)
- Re: [6tsch] On the fly scheduling Qin Wang
- Re: [6tsch] On the fly scheduling Kris Pister
- Re: [6tsch] On the fly scheduling Guillaume Gaillard
- Re: [6tsch] On the fly scheduling Qin Wang
- Re: [6tsch] On the fly scheduling Guillaume Gaillard