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Richardson 3 Internet-Draft Sandelman Software Works 4 Intended status: Informational March 19, 2020 5 Expires: September 20, 2020 7 Enabling secure network enrollment in RPL networks 8 draft-ietf-roll-enrollment-priority-01 10 Abstract 12 [I-D.ietf-6tisch-enrollment-enhanced-beacon] defines a method by 13 which a potential [I-D.ietf-6tisch-minimal-security] join proxy can 14 announce itself as a available for new Pledges to Join a network. 15 The announcement includes a priority for join. This document 16 provides a mechanism by which a RPL DODAG root can disable join 17 announcements, or adjust the base priority for join operation. 19 Status of This Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at https://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on September 20, 2020. 36 Copyright Notice 38 Copyright (c) 2020 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (https://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 54 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 55 2. Protocol Definition . . . . . . . . . . . . . . . . . . . . . 3 56 3. Security Considerations . . . . . . . . . . . . . . . . . . . 4 57 4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 4 58 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 59 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 60 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 61 7.1. Normative References . . . . . . . . . . . . . . . . . . 4 62 7.2. Informative References . . . . . . . . . . . . . . . . . 5 63 Appendix A. Change history . . . . . . . . . . . . . . . . . . . 6 64 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 66 1. Introduction 68 [RFC7554] describes the use of the time-slotted channel hopping 69 (TSCH) mode of [ieee802154]. [I-D.ietf-6tisch-minimal-security] and 70 [I-D.ietf-6tisch-dtsecurity-secure-join] describe mechanisms by which 71 a new node (the "pledge)" can use a friendly router as a Join Proxy. 72 [I-D.ietf-6tisch-enrollment-enhanced-beacon] describes an extension 73 to the 802.15.4 Enhanced Beacon that is used by a Join Proxy to 74 announce its existence such that Pledges can find them. 76 It has become clear that not every routing member of the mesh ought 77 to announce itself as a Join Proxy. There are a variety of local 78 reasons by which a 6LR might not want to provide the Join Proxy 79 function. They include available battery power, already committed 80 network bandwidth, and also total available memory available for Join 81 proxy neighbor cache slots. 83 There are other situations where the operator of the network would 84 like to selective enable or disable the join process in a particular 85 DODAG. 87 As the join process involves permitting unencrypted traffic into the 88 best effort part of a (TSCH) network, it would be better to have the 89 join process off when no new nodes are expected. 91 A network operator might also be able to recognize when certain parts 92 of the network are overloaded and can not accomodate additional join 93 traffic, and it would like to adjust the join priority among all 94 nodes in the subtree of a congested link. 96 This document describes an RPL DIO option that can be used to 97 announce a minimum join priority. Each potential Join Proxy would 98 this value as a base on which to add (decreasing likely hood of 99 attracting traffic) values relating to local conditions. 101 A network operator can set this value to the maximum value allowed, 102 effectively disable all new join traffic. 104 1.1. Terminology 106 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 107 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 108 "OPTIONAL" in this document are to be interpreted as described in 109 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 110 capitals, as shown here. 112 2. Protocol Definition 114 The following option is defined to transmission in the DIO issued by 115 the DODAG root. It may also be added by a router on part of the sub- 116 tree as a result of some (out of scope for this document) management 117 function. 119 6LRs that see this DIO Option SHOULD increment the minimum priority 120 if they observe congestion on the channel used for join traffic. 121 (TODO: how much? Do we need to standardize this?) 123 A 6LR which would otherwise be willing to act as a Join Proxy, will 124 examine the minimum priority field, and to that number, add any 125 additional local consideration (such as upstream congestion). The 126 resulting priority, if less than 0x7f should enable the Join Proxy 127 function. 129 0 1 2 130 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 131 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 132 | Type = TBD01|Opt Length = 1|R| min. priority | 133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 135 min.priority a 7 bit field which provides a base value for the 136 Enhanced Beacon Join priority. A value of 0x7f (127) disables the 137 Join Proxy function entirely. 139 R a reserved bit that SHOULD be set to 0 by senders, and MUST be 140 ignored by receivers. The reserved bit SHOULD be copied to 141 options created. 143 3. Security Considerations 145 As per [RFC7416], RPL control frames either run over a secured layer 146 2, or use the [RFC6550] Secure DIO methods. This option can be 147 placed into either a "clear" (layer-2 secured) DIO, or a layer-3 148 Secure DIO. As such this option will have both integrity and 149 confidentiality mechanisms applied to it. 151 A malicious node (that was part of the RPL control plane) could see 152 these options and could, based upon the observed minimal join 153 priority signal a confederate that it was a good time to send 154 malicious join traffic. 156 A malicious node (that was part of the RPL control plane) could also 157 send DIOs with a different minimal join priority which would cause 158 downstream mesh routers to change their Join Proxy behaviour. Lower 159 minimal priorities would cause downstream nodes to accept more 160 pledges than the network was expecting, and higher minimal priorities 161 cause the join process to stall. 163 The use of layer-2 or layer-3 security for RPL control messages 164 prevents the above two attacks. 166 4. Privacy Considerations 168 There are no new privacy issues caused by this extension. 170 5. IANA Considerations 172 Allocate a new number TBD01 from Registry RPL Control Message 173 Options. This entry should be called Minimum Join Priority. 175 6. Acknowledgements 177 This has been reviewed by Pascal Thubert and Thomas Wattenye. 179 7. References 181 7.1. Normative References 183 [I-D.ietf-6tisch-enrollment-enhanced-beacon] 184 Dujovne, D. and M. Richardson, "IEEE 802.15.4 Information 185 Element encapsulation of 6TiSCH Join and Enrollment 186 Information", draft-ietf-6tisch-enrollment-enhanced- 187 beacon-14 (work in progress), February 2020. 189 [I-D.ietf-6tisch-minimal-security] 190 Vucinic, M., Simon, J., Pister, K., and M. Richardson, 191 "Constrained Join Protocol (CoJP) for 6TiSCH", draft-ietf- 192 6tisch-minimal-security-15 (work in progress), December 193 2019. 195 [ieee802154] 196 IEEE standard for Information Technology, ., "IEEE Std. 197 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC) 198 and Physical Layer (PHY) Specifications for Low-Rate 199 Wireless Personal Area Networks", n.d., 200 . 203 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 204 Requirement Levels", BCP 14, RFC 2119, 205 DOI 10.17487/RFC2119, March 1997, 206 . 208 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 209 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 210 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 211 Low-Power and Lossy Networks", RFC 6550, 212 DOI 10.17487/RFC6550, March 2012, 213 . 215 [RFC7416] Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A., 216 and M. Richardson, Ed., "A Security Threat Analysis for 217 the Routing Protocol for Low-Power and Lossy Networks 218 (RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015, 219 . 221 [RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using 222 IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the 223 Internet of Things (IoT): Problem Statement", RFC 7554, 224 DOI 10.17487/RFC7554, May 2015, 225 . 227 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 228 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 229 May 2017, . 231 7.2. Informative References 233 [I-D.ietf-6tisch-architecture] 234 Thubert, P., "An Architecture for IPv6 over the TSCH mode 235 of IEEE 802.15.4", draft-ietf-6tisch-architecture-28 (work 236 in progress), October 2019. 238 [I-D.ietf-6tisch-dtsecurity-secure-join] 239 Richardson, M., "6tisch Secure Join protocol", draft-ietf- 240 6tisch-dtsecurity-secure-join-01 (work in progress), 241 February 2017. 243 [I-D.ietf-6tisch-terminology] 244 Palattella, M., Thubert, P., Watteyne, T., and Q. Wang, 245 "Terms Used in IPv6 over the TSCH mode of IEEE 802.15.4e", 246 draft-ietf-6tisch-terminology-10 (work in progress), March 247 2018. 249 [RFC8137] Kivinen, T. and P. Kinney, "IEEE 802.15.4 Information 250 Element for the IETF", RFC 8137, DOI 10.17487/RFC8137, May 251 2017, . 253 [RFC8366] Watsen, K., Richardson, M., Pritikin, M., and T. Eckert, 254 "A Voucher Artifact for Bootstrapping Protocols", 255 RFC 8366, DOI 10.17487/RFC8366, May 2018, 256 . 258 Appendix A. Change history 260 version 00. 262 Author's Address 264 Michael Richardson 265 Sandelman Software Works 267 Email: mcr+ietf@sandelman.ca