6TiSCH On-the-Fly Scheduling
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|Authors||Diego Roberto Dujovne , Luigi Alfredo Grieco , Maria Rita Palattella , Nicola Accettura|
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6TiSCH D. Dujovne, Ed. Internet-Draft Universidad Diego Portales Intended status: Informational LA. Grieco Expires: June 8, 2014 Politecnico di Bari MR. Palattella University of Luxembourg N. Accettura Politecnico di Bari December 5, 2013 6TiSCH On-the-Fly Scheduling draft-dujovne-6tisch-on-the-fly-00 Abstract This document describes the environment, problem statement, and goals of the On-The-Fly (OTF) scheduling for the IEEE802.15.4e TSCH MAC protocol in the context of LLNs. The purpose of OTF is to dynamically adapt the number of reserved cells between neighbor nodes to satisfy different type of constraints, based on the specific application. The cell reservation with OTF is distributed: neighbor nodes negotiate the cell(s) to be (re)allocated/deleted among them, without the intervention of a centralized entity. This document aims to define a module which uses the functionalities provided by the 6top sublayer to extract statistics and to reserve/delete cells in the schedule, leaving the reservation/deletion algorithm, and the number and type of statistics to be used in the algorithm itself, open. OTF allows to reserve/delete either a single cell between a couple of nodes, or a set of them (i.e., a bundle) in the TSCH schedule. Also, OTF allows to negotiate the aggregate bandwidth of a link without explicitly dealing with a reservation of a specific subset of cells. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." Dujovne, et al. Expires June 8, 2014 [Page 1] Internet-Draft 6tisch-on-the-fly December 2013 This Internet-Draft will expire on June 8, 2014. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Allocation policy . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Allocation methods . . . . . . . . . . . . . . . . . . . 3 3. Input parameters: statistics and instant values . . . . . . . 4 4. Bundle usage management in OTF . . . . . . . . . . . . . . . 4 4.1. Cell Reservation/Deletion . . . . . . . . . . . . . . . . 4 4.2. Bundle Size Increase/Decrease . . . . . . . . . . . . . . 4 5. Schedule storage on OTF . . . . . . . . . . . . . . . . . . . 5 6. Algorithm selection . . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 8.1. Informative References . . . . . . . . . . . . . . . . . 5 8.2. External Informative References . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction The IEEE802.15.4e standard [IEEE802154e] was published in 2012 as an amendment to the Medium Access Control (MAC) protocol defined by the IEEE802.15.4-2011 [IEEE802154] standard. The Timeslotted Channel Hopping (TSCH) mode of IEEE802.15.4e is the object of this document. On-The-Fly (OTF) scheduling is a distributed protocol intended to enable a node to define a common schedule with its neighbors without the intervention of a centralized entity. In particular, this document describes the methods, flows and packets involved in this process by using the functionalities offered by the 6top sublayer, as defined in [I-D.wang-6tisch-6top]. In order to be extendible, and thus, applicable in different scenario, OTF has not been designed for Dujovne, et al. Expires June 8, 2014 [Page 2] Internet-Draft 6tisch-on-the-fly December 2013 working with a specific scheduling algorithm nor with a well-defined set of statistics. It provides a general framework and a set of methods that can be used by different algorithms. This document follows the terminology defined in [I-D.palattella-6tisch-terminology] and the mechanisms described on [I-D.watteyne-6tisch-tsch] 2. Allocation policy OTF Cell allocation is distributed. All the allocation requests are sent to 6top, which will be in charge of granting the requested Softcells or Bundles. Since the requests are satisfied on a peer to peer basis, without the participation of a PCE, this may generate Softcell reservation collisions between different pairs of nodes. Although distributed reservation reduces the latency, this can be done at the cost of increasing the Softcell allocation collision probability There are 3 types of allocation policies supported by OTF, namely Post-allocation, Pre-allocation and Hybrid allocation. On the Post-allocation policy, according to the current algorithm decision, OTF sends allocation requests to 6top for individual softcells. After the softcells are granted, OTF keeps track of the number of cells allocated for each of the neighbours. If the algorithm decides to free cells to any neighbour, a deallocation request is issued to 6top. When the deallocation is confirmed, OTF updates the internal cell allocation tables. On the Pre-allocation policy, given a decision from the algorithm, OTF requests to 6top the allocation of a block of Softcells, called a Bundle. When the allocation is granted, the algorithm decides which of the allocated cells inside the Bundle will be used for communication. The remaining cells inside the Bundle will remain allocated but not used. OTF keeps track of the allocated Bundles, and the number of used cells inside the Bundle. Used cells inside a Bundle are consecutive starting from the first cell in the Bundle. When the algorihtm decides to enlarge or reduce the Bundle size, OTF forwards this request to 6top. On the Hybrid allocation policy, when the algorithm issues an allocation request for new cells, OTF must decide between allocating individual softcells, incrementing the number of used cells within a Bundle, or request to 6top to enlarge the Bundle if there were no free cells inside. OTF keps track of the individual softcells, the allocated Bundles and the number of allocated cells inside the Bundle. 2.1. Allocation methods Dujovne, et al. Expires June 8, 2014 [Page 3] Internet-Draft 6tisch-on-the-fly December 2013 OTF uses two allocation methods: Bundle and Softcell. The Bundle allocation method requests to 6top a group of cells called a Bundle. OTF manages internally the allocation of individual cells within the Bundle. The goal of this allocation method is to provide a low-delay response after a surge in bandwidth usage, at the expense of energy consumption. Once the Bundle is allocated, OTF may ask for sizing/re-sizing BW of a bundle, which implies softcells will be reserved. For this purpose, OTF only calculates required Bandwidth, and 6top maps the BW to the number of soft cells according to some QoS setting, e.g. over-provision ratio, and then allocates and maintains them. The Softcell allocation method calculates the required Bandwidth and requests individual softcells to 6top. The 6top layer allocates and maintains the individual softcells. This method reduces energy consumption by allocating only the required bandwidth, to the expense of increasing cell allocation latency. 3. Input parameters: statistics and instant values Short summary of a potential set of statistics and instant values that could be used as input parameters. List of parameters available from 6top: mainly statistics related to queues Method to configure 6top to provide historical values for each requested parameter Method to ask 6top for instant values for each requested parameter Method for asking list of parameters from 6top and thus, for checking if a parameter is avaialble or not 4. Bundle usage management in OTF Methods that trigger the request of increasing/decreasing the bundle, and thus, adding/deleting cells 4.1. Cell Reservation/Deletion The commands to reserve/delete Softcells. interaction with 6top 4.2. Bundle Size Increase/Decrease The commands to increase/decrease the Bundle size. interaction with 6top Dujovne, et al. Expires June 8, 2014 [Page 4] Internet-Draft 6tisch-on-the-fly December 2013 5. Schedule storage on OTF The description and access to the schedule storage on OTF The commands to retrieve bundle usage values and statistics from OTF (based on previous values obtained by 6top?) The commands to retrieve cell usage values and statistics from OTF (based on previous values obtained by 6top?) 6. Algorithm selection There may be multiple algorithms stored within OTF. Here we describe how to select one of the stored algorithms. 7. Acknowledgements Special thanks to for his review and valuable comments. Thanks to the Fondecyt 1121475 Project, to INRIA Chile "Network Design" group and to the IoT6 European Project (STREP) of the 7th Framework Program (Grant 288445). 8. References 8.1. Informative References [I-D.palattella-6tisch-terminology] Palattella, M., Thubert, P., Watteyne, T., and Q. Wang, "Terminology in IPv6 over the TSCH mode of IEEE 802.15.4e", draft-palattella-6tisch-terminology-00 (work in progress), October 2013. [I-D.wang-6tisch-6top] Wang, Q., Vilajosana, X., and T. Watteyne, "6TiSCH Operation Sublayer (6top)", draft-wang-6tisch-6top-00 (work in progress), October 2013. [I-D.watteyne-6tisch-tsch] Watteyne, T., Palattella, M., and L. Grieco, "Using IEEE802.15.4e TSCH in an LLN context: Overview, Problem Statement and Goals", draft-watteyne-6tisch-tsch-00 (work in progress), October 2013. Dujovne, et al. Expires June 8, 2014 [Page 5] Internet-Draft 6tisch-on-the-fly December 2013 8.2. External Informative References [IEEE802154e] IEEE standard for Information Technology, "IEEE std. 802.15.4e, Part. 15.4: Low-Rate Wireless Personal Area Networks (LR-WPANs) Amendament 1: MAC sublayer", April 2012. [IEEE802154] IEEE standard for Information Technology, "IEEE std. 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Low-Rate Wireless Personal Area Networks", June 2011. [TASA-PIMRC] Palattella, MR., Accettura, N., Dohler, M., Grieco, LA., and G. Boggia, "Traffic Aware Scheduling Algorithm for Multi-Hop IEEE 802.15.4e Networks", IEEE PIMRC 2012, Sept. 2012, < http://www.cttc.es/resources/doc/120531-submitted- tasa-25511.pdf>. [DeTAS] Accettura, N., Palattella, , Boggia, G., Grieco, LA., and M. Dohler, "DeTAS: a Decentralized Traffic Aware Scheduling technique enabling IoT-compliant Multi-hop Low- power and Lossy Networks", IEEE WoWMoM on the Internet of Things 2013, June 2013, < http://www.gtti.it/GTTI13/papers /Accettura_et_al_GTTI2013.pdf>. Authors' Addresses Diego Dujovne (editor) Universidad Diego Portales Escuela de Informatica y Telecomunicaciones Av. Ejercito 441 Santiago, Region Metropolitana Chile Phone: +56 (2) 676-8121 Email: email@example.com Dujovne, et al. Expires June 8, 2014 [Page 6] Internet-Draft 6tisch-on-the-fly December 2013 Luigi Alfredo Grieco Politecnico di Bari Department of Electrical and Information Engineering Via Orabona 4 Bari 70125 Italy Phone: 00390805963911 Email: firstname.lastname@example.org Maria Rita Palattella University of Luxembourg Interdisciplinary Centre for Security, Reliability and Trust 4, rue Alphonse Weicker Luxembourg L-2721 LUXEMBOURG Phone: (+352) 46 66 44 5841 Email: email@example.com Nicola Accettura Politecnico di Bari Electrical and Electronics Department Via Orabona 4 Bari 70125 Italy Phone: +39 080 5963301 Email: firstname.lastname@example.org Dujovne, et al. Expires June 8, 2014 [Page 7]