Xavi; As I understand slotted-aloha, TSCH is really Time Division Multiple Access (TDMA), not slotted-aloha. Slotted-aloha access to the medium is used in the 802.15.4 CSMA algorithms for some modes but not TSCH.
Pat On 11, Dec2015, at 11:24, Xavier Vilajosana <[email protected]> wrote: Dear all, I wrapped up the proposed changes and integrated them to the version in bitbucket. https://bitbucket.org/6tisch/draft-ietf-6tisch-minimal/commits/28cb63fde078a0aec8307d416e82cdf482c0608a <https://bitbucket.org/6tisch/draft-ietf-6tisch-minimal/commits/28cb63fde078a0aec8307d416e82cdf482c0608a> For simplicity, see here a summary of the changes. Abstract: [OLD] This document describes the minimal set of rules to operate an IEEE 802.15.4 Timeslotted Channel Hopping (TSCH) network. This minimal mode of operation can be used during network bootstrap, as a fall- back mode of operation when no dynamic scheduling solution is available or functioning, or during early interoperability testing and development. [NEW] This document describes a minimal mode of operation for a 6TiSCH Network, to provide IPv6 connectivity over a Non-Broadcast Multi- Access (NBMA) mesh that is formed of IEEE 802.15.4 Timeslotted Channel Hopping (TSCH) links. This minimal mode leverages 6LoWPAN and RPL to enable slotted-aloha operations over a static TSCH schedule. Introduction: [OLD] The nodes in a IEEE 802.15.4 TSCH network follow a communication schedule. The entity (centralized or decentralized) responsible for building and maintaining that schedule has precise control over the trade-off between the network's latency, bandwidth, reliability and power consumption. During early interoperability testing and development, however, simplicity is more important than efficiency. One goal of this document is to define the simplest set of rules for building a TSCH-compliant network, at the necessary price of lesser efficiency. Yet, this minimal mode of operation MAY also be used during network bootstrap before any schedule is installed into the network so nodes can self-organize and the management and configuration information be distributed. In addition, the minimal configuration MAY be used as a fall-back mode of operation, ensuring connectivity of nodes in case that dynamic scheduling mechanisms fail or are not available. The IEEE 802.15.4 specification provides a mechanism whereby the details of slotframe length, timeslot timing, and channel hopping pattern are communicated when a node time synchronizes to the network [IEEE802154]. This document describes specific settings for these parameters. [NEW] A 6TiSCH Network provides IPv6 connectivity over a Non-Broadcast Multi-Access (NBMA) mesh that is formed of IEEE 802.15.4 Timeslotted Channel Hopping (TSCH) links. The 6TiSCH [I-D.ietf-6tisch-architecture] architecture requires the use of both RPL and the 6LoWPAN adaptation layer framework ([RFC4944], [RFC6282]) as defined over IEEE 802.14.5. 6LoWPAN Neighbor Discovery [RFC6775] (ND) is also required to exchange Compression Contexts, form IPv6 addresses and register them for the purpose of Duplicate Address Detection, Address Resolution and Neighbor Unreachability detection over one TSCH link. In order to reduce the header overhead of the RPL artifacts in data packets, the Routing header [RFC6554], the RPL Option [RFC6553] and the related IP in IP encapsulation MUST be encoded as prescribed in [I-D.ietf-6lo-routing-dispatch] Nodes in a IEEE 802.15.4 TSCH network follow a communication schedule. A network using the simple mode of operation uses a static schedule. This specification defines a Minimal Configuration to build a 6TiSCH Network, using the Routing Protocol for LLNs (RPL) and a static TSCH Schedule. The 802.15.4 TSCH mode, RPL [RFC6550], and its Objective Function 0 (OF0) [RFC6552], are used unmodified, but parameters and particular operations are specified to guarantee interoperability between nodes in a 6TiSCH Network. More advanced work is expected in the future to complement the Minimal Configuration with dynamic operations that can adapt the Schedule to the needs of the traffic in run time. Section 11.2 [OLD] In addition to the Objective Function (OF), nodes in a multihop network using RPL MUST indicate the preferred mode of operation using the MOP field in DIO. Nodes not being able to operate in the specified mode of operation MUST only join as leaf nodes. RPL information and hop-by-hop extension headers MUST follow [RFC6553] and [RFC6554] specification. In the case that the packets formed at the LLN need to cross through intermediate routers, these MUST follow the IP in IP encapsulation requirement specified by the [RFC6282] and [RFC2460]. RPI and RH3 extension headers and inner IP headers MUST be compressed according to [RFC6282]. [NEW] In addition to the Objective Function (OF), nodes in a multihop network using RPL MUST indicate the preferred mode of operation using the MOP field in DIO. Nodes not being able to operate in the specified mode of operation MUST only join as leaf nodes. RPL information and hop-by-hop extension headers MUST follow [RFC6553] and [RFC6554] specification. In the case that the packets formed at the LLN need to cross through intermediate routers, these MUST follow the IP in IP encapsulation requirement specified by the [RFC6282] and [RFC2460]. RPI and RH3 extension headers and inner IP headers MUST be compressed according to [RFC6282] and [I-D.ietf-6lo-routing-dispatch]. have a nice weekend, Xavi 2015-12-11 17:49 GMT+01:00 Kris Pister <[email protected] <mailto:[email protected]>>: Ralph - to my knowledge no one has deployed the specific time-parent selection scheme described in 802.15.4-*. The basic scheme will likely work, but the devil will be in the real-world details. We've had about 8 years of successful deployments of industrial tsch mesh networks using a time-parent selection scheme similar to what is proposed in minimal. 6TiSCH present a rich design space at many levels. The goal of minimal was to do something simple, based as closely as possible on things that are known to work in deployed networks. The hope and belief is that new and better ideas will emerge, but it is certain that many of the proposed "good ideas" will fail. By defining minimal we provide a reliable interoperable platform on which papers like "Comparing time-parent selection in 15.4-* and foo" can be written. ksjp On 12/10/2015 5:43 AM, Ralph Droms (rdroms) wrote: Is there an analysis published somewhere that demonstrates how time synchronization in 802.15.4-* is inadequate for 6TiSCH? _______________________________________________ 6tisch mailing list [email protected] <mailto:[email protected]> https://www.ietf.org/mailman/listinfo/6tisch <https://www.ietf.org/mailman/listinfo/6tisch> _______________________________________________ 6tisch mailing list [email protected] https://www.ietf.org/mailman/listinfo/6tisch
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