6lo Working Group D. Dujovne Internet-Draft Universidad Diego Portales Intended status: Informational M. Richardson Expires: January 18, 2019 Sandelman Software Works July 17, 2018 IEEE802.15.4 Informational Element encapsulation of 6tisch Join and Enrollment Information draft-ietf-6tisch-enrollment-enhanced-beacon-00 Abstract In TSCH mode of IEEE802.15.4, as described by [RFC8180], opportunities for broadcasts are limited to specific times and specific channels. Nodes in a TSCH network typically frequently send Enhanced Beacon (EB) frames to announce the presence of the network. This document provides a mechanism by which small details critical for new nodes (pledges) and long sleeping nodes may be carried within the Enhanced Beacon. 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 https://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." This Internet-Draft will expire on January 18, 2019. Copyright Notice Copyright (c) 2018 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 (https://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 Dujovne & Richardson Expires January 18, 2019 [Page 1] Internet-Draft IE for ICMPv6 July 2018 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 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 1.2. Layer-2 Synchronization . . . . . . . . . . . . . . . . . 3 1.3. Layer-3 synchronization IPv6 Router solicitations and advertisements . . . . . . . . . . . . . . . . . . . . . 3 2. Protocol Definition . . . . . . . . . . . . . . . . . . . . . 4 2.1. Protocol Example . . . . . . . . . . . . . . . . . . . . 5 3. Security Considerations . . . . . . . . . . . . . . . . . . . 5 4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. Normative References . . . . . . . . . . . . . . . . . . 6 7.2. Informative References . . . . . . . . . . . . . . . . . 7 Appendix A. Change history . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction [RFC7554] describes the use of the time-slotted channel hopping (TSCH) mode of [ieee802154]. As further details in [RFC8180], an Enhanced Beacon is transmitted during a slot designated a broadcast slot. EDNOTE: Explain why broadcasts are rare, and why we need them. What the Enhanced Beacon is, and what Information Elements are, and how the IETF has a subtype for that area. Explain what kind of things could be placed in Information Elements, how big they could be, and how they could be compressed. 1.1. Terminology In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119 [RFC2119] and indicate requirement levels for compliant STuPiD implementations. Dujovne & Richardson Expires January 18, 2019 [Page 2] Internet-Draft IE for ICMPv6 July 2018 1.2. Layer-2 Synchronization As explained in section 6 of [RFC8180], the Enhanced Beacon has a number of purposes: synchronization of ASN and Join Metric, timeslot template identifier, the channel hopping sequence identifier, TSCH SlotFrame and Link IE. The Enhanced Beacon (EB) is used by nodes already part of a TSCH network to annouce its existance. Receiving an EB allows a Joining Node (pledge) to learn about the network and synchronize to it. The EB may also be used as a means for a node already part of the network to re-synchronize [RFC7554]. There are a limited number of timeslots designated as a broadcast slot by each router. These slots are rare, and with 10ms slots, with a slot-frame length of 100, there may be only 1 slot/s for the beacon. 1.3. Layer-3 synchronization IPv6 Router solicitations and advertisements At layer 3, [RFC2461] defines a mechanism by which nodes learn about routers by listening for multicasted Router Advertisements (RA). If no RA is heard within a set time, then a Router Solicitation (RS) may be multicast, to which an RA will be received, usually unicast. Although [RFC6775] reduces the amount of multicast necessary to do address resolution via Neighbor Solicitation messages, it still requires multicast of either RAs or RS. This is an expensive operation for two reasons: there are few multicast timeslots for unsolicited RAs; if a pledge node does not hear an RA, and decides to send a RS (consuming a broadcast aloha slot with unencrypted traffic), many unicast RS may be sent in response. This is a particularly acute issue for the join process for the following reasons: 1. use of a multicast slot by even a non-malicious unauthenticated node for a Router Solicitation may overwhelm that time slot. 2. it may require many seconds of on-time before a new pledge hears a Router Soliciation that it can use. 3. a new pledge may listen to many Enhanced Beacons before it can pick an appropriate network and/or closest Join Assistant to attach to. If it must listen for a RS as well as find the Enhanced Beacon, then the process may take a very long time. Dujovne & Richardson Expires January 18, 2019 [Page 3] Internet-Draft IE for ICMPv6 July 2018 2. Protocol Definition [RFC8137] creates a registry for new IETF IE subtypes. This document allocates a new subtype TBD-XXX. This document documents a new IE subtype structure is as follows. As explained in [RFC8137] the length of the Sub-Type Content can be calculated from the container, so no length information is necessary. 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TBD-XXX |R| proxy prio. | rank priority | +-+-+-+-+-+-+-+-+-+-------------+-------------+-----------------+ | pan priority | | +---------------+ + | network ID | + + | | + + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+ proxy priority the proxy prority value contains a number from 0 to 0x7f. Lower numbers are considered to be a higher preference. A priority of 0x7f indicates that the announcer should never be considered as a viable enrollment proxy. Lower value indicates willing to act as a Join Proxy as described in [I-D.ietf-6tisch-minimal-security]. Only unenrolled pledges look at this value. pan priority the pan priority is a value set by the DODAG root to indicate the relative priority of this LLN compared to those with different PANIDs. This value may be used as part of the enrollment priority, but typically is used by devices which have already enrolled, and need to determine which PAN to pick. Unenrolled pledges MAY consider this value when selecting a PAN to join. Enrolled devices MAY consider this value when looking for an eligible parent device. rank priority the rank "priority" is set by the 6LR which sent the beacon and is an indication of how willing this 6LR is to serve as an RPL parent within a particular network ID. This is a local value to be determined in other work. It might be calculated from RPL rank, and it may include some modifications based upon current number of children, or number of neighbor cache entries available. Dujovne & Richardson Expires January 18, 2019 [Page 4] Internet-Draft IE for ICMPv6 July 2018 This value MUST be ignored by pledges, it is for enrolled devices only. R the Router Advertisement flag is set if the sending node will act as a Router for host-only nodes that need addressing via unicast Router Solicitation messages. network ID this is an opaque 16-byte identifier that uniquely identifies this network, potentially among many networks that are operating in the same frequencies in overlapping physical space. In a 6tisch network, where RPL is used as the mesh routing protocol, the network ID can be constructed from a SHA256 hash of the prefix (/64) of the network. That is just a suggestion for a default value. In some LLNs where multiple PANIDs may lead to the same management device (the JRC), then a common value that is the same across all PANs MUST be configured. 2.1. Protocol Example Here will be three examples of processing. 3. Security Considerations All of the contents of this Information Element are sent in the clear. The containing Enhanced Beacon is not encrypted. The Enhanced Beagon is authenticated at the layer-2 level using 802.15.4 mechanisms using the network-wide keying material. Nodes which are enrolled will have the network-wide keying material and can validate the beacon. Pledges which have not yet enrolled are unable to authenticate the beacons. 4. Privacy Considerations The use of a network ID may reveal information about the network. The use of a SHA256 hash of the DODAGID, rather than using the DODAGID directly provides some cover the addresses used within the network. The DODAGID is usually the IPv6 address of the root of the RPL mesh. An interloper with a radio sniffer would be able to use the network ID to map out the extend of the mesh network. Dujovne & Richardson Expires January 18, 2019 [Page 5] Internet-Draft IE for ICMPv6 July 2018 5. IANA Considerations Allocate a new number TBD-XXX from Registry IETF IE Sub-type ID. This entry should be called 6tisch-Join-Info. 6. Acknowledgements Thomas Watteyne provided extensive editorial comments on the document. 7. References 7.1. Normative References [I-D.ietf-6tisch-architecture] Thubert, P., "An Architecture for IPv6 over the TSCH mode of IEEE 802.15.4", draft-ietf-6tisch-architecture-14 (work in progress), April 2018. [I-D.ietf-6tisch-minimal-security] Vucinic, M., Simon, J., Pister, K., and M. Richardson, "Minimal Security Framework for 6TiSCH", draft-ietf- 6tisch-minimal-security-06 (work in progress), May 2018. [ieee802154] IEEE Standard, ., "802.15.4-2015 - IEEE Standard for Low- Rate Wireless Personal Area Networks (WPANs)", 2015, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2461] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, DOI 10.17487/RFC2461, December 1998, . [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. Bormann, "Neighbor Discovery Optimization for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)", RFC 6775, DOI 10.17487/RFC6775, November 2012, . Dujovne & Richardson Expires January 18, 2019 [Page 6] Internet-Draft IE for ICMPv6 July 2018 [RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the Internet of Things (IoT): Problem Statement", RFC 7554, DOI 10.17487/RFC7554, May 2015, . [RFC8137] Kivinen, T. and P. Kinney, "IEEE 802.15.4 Information Element for the IETF", RFC 8137, DOI 10.17487/RFC8137, May 2017, . 7.2. Informative References [I-D.ietf-6tisch-dtsecurity-secure-join] Richardson, M., "6tisch Secure Join protocol", draft-ietf- 6tisch-dtsecurity-secure-join-01 (work in progress), February 2017. [RFC8180] Vilajosana, X., Ed., Pister, K., and T. Watteyne, "Minimal IPv6 over the TSCH Mode of IEEE 802.15.4e (6TiSCH) Configuration", BCP 210, RFC 8180, DOI 10.17487/RFC8180, May 2017, . Appendix A. Change history The rank priority was expanded to 2 bytes. 00: The extension was originally for the use of Pledges only during the enrollment/join process. Additional information was desired for nodes which have already enrolled in order to aid in the joining (selecting of a parent) of an RPL DAG. The term "join" was realized to be ambiguous, meaning different things to different groups, and so the activity where the pledge finds a "Join Proxy" has been named "enrollment" -1: This is an evolution of an earlier proposal which provided for storing an entire IPv6 Router Adverisement in an Informational Element. It was deemed too general a solution, possibly subject to mis-use. This proposal restricts the use to just the key pieces of information required. Authors' Addresses Dujovne & Richardson Expires January 18, 2019 [Page 7] Internet-Draft IE for ICMPv6 July 2018 Diego Dujovne (editor) Universidad Diego Portales Escuela de Informatica y Telecomunicaciones, Av. Ejercito 441 Santiago, Region Metropolitana Chile Phone: +56 (2) 676-8121 Email: diego.dujovne@mail.udp.cl Michael Richardson Sandelman Software Works Email: mcr+ietf@sandelman.ca Dujovne & Richardson Expires January 18, 2019 [Page 8]