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'ieee802154' ** Downref: Normative reference to an Informational RFC: RFC 8137 == Outdated reference: A later version (-30) exists of draft-ietf-6tisch-architecture-28 Summary: 1 error (**), 0 flaws (~~), 6 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 6lo Working Group D. Dujovne 3 Internet-Draft Universidad Diego Portales 4 Intended status: Standards Track M. Richardson 5 Expires: May 7, 2020 Sandelman Software Works 6 November 04, 2019 8 IEEE 802.15.4 Information Element encapsulation of 6TiSCH Join and 9 Enrollment Information 10 draft-ietf-6tisch-enrollment-enhanced-beacon-06 12 Abstract 14 In TSCH mode of IEEE STD 802.15.4, opportunities for broadcasts are 15 limited to specific times and specific channels. Nodes in a TSCH 16 network typically frequently send Enhanced Beacon (EB) frames to 17 announce the presence of the network. This document provides a 18 mechanism by which small details critical for new nodes (pledges) and 19 long sleeping nodes may be carried within the Enhanced Beacon. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at https://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on May 7, 2020. 38 Copyright Notice 40 Copyright (c) 2019 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (https://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 56 1.1. Use of BCP 14 Terminology . . . . . . . . . . . . . . . . 2 57 1.2. Layer-2 Synchronization . . . . . . . . . . . . . . . . . 2 58 1.3. Layer-3 synchronization: IPv6 Router Solicitations and 59 Advertisements . . . . . . . . . . . . . . . . . . . . . 3 60 2. Protocol Definition . . . . . . . . . . . . . . . . . . . . . 4 61 3. Security Considerations . . . . . . . . . . . . . . . . . . . 5 62 4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 6 63 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 64 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 65 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 66 7.1. Normative References . . . . . . . . . . . . . . . . . . 6 67 7.2. Informative References . . . . . . . . . . . . . . . . . 7 68 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 70 1. Introduction 72 [RFC7554] describes the use of the time-slotted channel hopping 73 (TSCH) mode of [ieee802154]. As further detailed in [RFC8180], an 74 Enhanced Beacon (EB) is transmitted during a slot designated a 75 broadcast slot. 77 1.1. Use of BCP 14 Terminology 79 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 80 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 81 "OPTIONAL" in this document are to be interpreted as described in 82 [BCP14] [RFC2119] when, and only when, they appear in all capitals, 83 as shown here. 85 Other terminology can be found in [I-D.ietf-6tisch-architecture] in 86 section 2.1. 88 1.2. Layer-2 Synchronization 90 As explained in section 6 of [RFC8180], the Enhanced Beacon (EB) has 91 a number of purposes: synchronization of ASN and Join Metric, 92 carrying timeslot template identifier, carrying the channel hopping 93 sequence identifier, and indicating the TSCH SlotFrame. 95 The EB is used by nodes already part of a TSCH network to annouce its 96 existence. Receiving an EB allows a Joining Node (pledge) to learn 97 about the network and synchronize to it. The EB may also be used as 98 a means for a node already part of the network to re-synchronize 99 [RFC7554]. 101 There is a limited number of timeslots designated as a broadcast slot 102 by each router in the network. These slots are rare, and with 10ms 103 slots, with a slot-frame length of 100, there may be only 1 slot/s 104 for the beacon. 106 1.3. Layer-3 synchronization: IPv6 Router Solicitations and 107 Advertisements 109 At layer 3, [RFC4861] defines a mechanism by which nodes learn about 110 routers by listening for multicasted Router Advertisements (RA). If 111 no RA is heard within a set time, then a Router Solicitation (RS) may 112 be multicast, to which an RA will be received, usually unicast. 114 Although [RFC6775] reduces the amount of multicast necessary to do 115 address resolution via Neighbor Solicitation (NS) messages, it still 116 requires multicast of either RAs or RS. This is an expensive 117 operation for two reasons: First, there are few multicast timeslots 118 for unsolicited RAs; and second, if a pledge node does not hear an 119 RA, and decides to send a RS, a broadcast aloha slot is consumed with 120 unencrypted traffic. In this case, a unicast RS may be sent in 121 response. 123 This is a particularly acute issue for the join process for the 124 following reasons: 126 1. use of a multicast slot by even a non-malicious unauthenticated 127 node for a Router Solicitation (RS) may overwhelm that time slot. 129 2. it may require many seconds of on-time before a new pledge hears 130 a Router Advertisement (RA) that it can use. 132 3. a new pledge may listen to many Enhanced Beacons (EB) before it 133 can pick an appropriate network and/or closest Join Assistant to 134 attach to. If it must listen for a RA as well as find the 135 Enhanced Beacon (EB), then the process may take a very long time. 137 This document defines a new IETF IE subtype to provide join and 138 enrollment information to prospective pledges in a more efficient 139 way. 141 2. Protocol Definition 143 [RFC8137] creates a registry for new IETF IE subtypes. This document 144 allocates a new subtype. 146 The new IE subtype structure is as follows. As explained in 147 [RFC8137] the length of the Sub-Type Content can be calculated from 148 the container, so no length information is necessary. 150 1 2 3 151 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 1 152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 153 | TBD-XXX |R|P| res | proxy prio | rank priority | 154 +-+-+-+-+-+-+-+-+-+-------------+-------------+-----------------+ 155 | pan priority | | 156 +---------------+ + 157 | Join Proxy lower-64 | 158 + (present if P=1) + 159 | | 160 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 161 | | | 162 +-+-+-+-+-+-+-+-+ + 163 | network ID | 164 + variable length, up to 16 bytes + 165 ~ ~ 166 + + 167 | | 168 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 169 | | 170 +-+-+-+-+-+-+-+-+ 172 Figure 1: IE subtype structure 174 R the Router Advertisement R-flag is set if the sending node will 175 act as a Router for host-only nodes that need addressing via 176 unicast Router Solicitation messages. 178 P if the Proxy Address P-flag is set, then the lower 64-bits of the 179 Join Proxy's link-local address follows the network ID. If the 180 Proxy Address bit is not set, then the Link Layer address of the 181 Join Proxy is identical to the Layer-2 8-byte address used to 182 originate this enhanced beacon. In either case, the destination 183 layer-2 address of this beacon may use the layer-2 address which 184 was used to originate the beacon. 186 proxy priority this field indicates the willingness fo the sender to 187 act as join proxy. Lower value indicates greater willingness to 188 act as a Join Proxy as described in 189 [I-D.ietf-6tisch-minimal-security]. Values range 0x00 (most 190 willing) to 0x7e (least willing). A priority of 0x7f indicates 191 that the announcer should never be considered as a viable 192 enrollment proxy. Only unenrolled pledges look at this value. 194 rank priority the rank "priority" is set by the 6LR which sent the 195 beacon and is an indication of how willing this 6LR is to serve as 196 an RPL parent within a particular network ID. This is a local 197 value to be determined in other work. It might be calculated from 198 RPL rank, and it may include some modifications based upon current 199 number of children, or number of neighbor cache entries available. 200 This value MUST be ignored by pledges, it is for enrolled devices 201 only. 203 pan priority the pan priority is a value set by the DODAG root to 204 indicate the relative priority of this LLN compared to those with 205 different PANIDs. This value may be used as part of the 206 enrollment priority, but typically is used by devices which have 207 already enrolled, and need to determine which PAN to pick. 208 Unenrolled pledges MAY consider this value when selecting a PAN to 209 join. Enrolled devices MAY consider this value when looking for 210 an eligible parent device. 212 Join Proxy lower-64 if the P bit is set, then 64 bits (8 bytes) of 213 address are present. This field provides the suffix of the Link- 214 Local address of the Join Proxy. The associated prefix is well- 215 known as fe80::/64. 217 network ID this is a variable length field, up to 16-bytes in size 218 that uniquely identifies this network, potentially among many 219 networks that are operating in the same frequencies in overlapping 220 physical space. The length of this field can be calculated as 221 being whatever is left in the Information Element. 223 In a 6tisch network, where RPL [RFC6550] is used as the mesh routing 224 protocol, the network ID can be constructed from a SHA256 hash of the 225 prefix (/64) of the network. That is just a suggestion for a default 226 value. In some LLNs where multiple PANIDs may lead to the same 227 management device (the JRC), then a common value that is the same 228 across all PANs MUST be configured. 230 3. Security Considerations 232 All of the contents of this Information Element are sent in the 233 clear. The containing Enhanced Beacon is not encrypted. 235 The Enhanced Beagon is authenticated at the layer-2 level using 236 802.15.4 mechanisms using the network-wide keying material. Nodes 237 which are enrolled will have the network-wide keying material and can 238 validate the beacon. 240 Pledges which have not yet enrolled are unable to authenticate the 241 beacons. 243 4. Privacy Considerations 245 The use of a network ID may reveal information about the network. 246 The use of a SHA256 hash of the DODAGID, rather than using the 247 DODAGID directly provides some cover the addresses used within the 248 network. The DODAGID is usually the IPv6 address of the root of the 249 RPL mesh. 251 An interloper with a radio sniffer would be able to use the network 252 ID to map out the extend of the mesh network. 254 5. IANA Considerations 256 Allocate a new number TBD-XXX from Registry IETF IE Sub-type ID, as 257 defined by [RFC8137]. This entry should be called 6tisch-Join-Info, 258 and should refer to this document. 260 6. Acknowledgements 262 Thomas Watteyne provided extensive editorial comments on the 263 document. Carles Gomez Montenegro generated a detailed review of the 264 document at WGLC. 266 7. References 268 7.1. Normative References 270 [BCP14] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 271 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 272 May 2017, . 274 [I-D.ietf-6tisch-minimal-security] 275 Vucinic, M., Simon, J., Pister, K., and M. Richardson, 276 "Minimal Security Framework for 6TiSCH", draft-ietf- 277 6tisch-minimal-security-13 (work in progress), October 278 2019. 280 [ieee802154] 281 IEEE standard for Information Technology, ., "IEEE Std. 282 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC) 283 and Physical Layer (PHY) Specifications for Low-Rate 284 Wireless Personal Area Networks", n.d., 285 . 288 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 289 Requirement Levels", BCP 14, RFC 2119, 290 DOI 10.17487/RFC2119, March 1997, 291 . 293 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 294 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 295 DOI 10.17487/RFC4861, September 2007, 296 . 298 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 299 Bormann, "Neighbor Discovery Optimization for IPv6 over 300 Low-Power Wireless Personal Area Networks (6LoWPANs)", 301 RFC 6775, DOI 10.17487/RFC6775, November 2012, 302 . 304 [RFC8137] Kivinen, T. and P. Kinney, "IEEE 802.15.4 Information 305 Element for the IETF", RFC 8137, DOI 10.17487/RFC8137, May 306 2017, . 308 7.2. Informative References 310 [I-D.ietf-6tisch-architecture] 311 Thubert, P., "An Architecture for IPv6 over the TSCH mode 312 of IEEE 802.15.4", draft-ietf-6tisch-architecture-28 (work 313 in progress), October 2019. 315 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 316 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 317 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 318 Low-Power and Lossy Networks", RFC 6550, 319 DOI 10.17487/RFC6550, March 2012, 320 . 322 [RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using 323 IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the 324 Internet of Things (IoT): Problem Statement", RFC 7554, 325 DOI 10.17487/RFC7554, May 2015, 326 . 328 [RFC8180] Vilajosana, X., Ed., Pister, K., and T. Watteyne, "Minimal 329 IPv6 over the TSCH Mode of IEEE 802.15.4e (6TiSCH) 330 Configuration", BCP 210, RFC 8180, DOI 10.17487/RFC8180, 331 May 2017, . 333 Authors' Addresses 335 Diego Dujovne (editor) 336 Universidad Diego Portales 337 Escuela de Informatica y Telecomunicaciones, Av. Ejercito 441 338 Santiago, Region Metropolitana 339 Chile 341 Phone: +56 (2) 676-8121 342 Email: diego.dujovne@mail.udp.cl 344 Michael Richardson 345 Sandelman Software Works 347 Email: mcr+ietf@sandelman.ca