[6tisch] Thomas' review of draft-richardson-6tisch-roll-enrollment-priority-00
Thomas Watteyne <thomas.watteyne@inria.fr> Sun, 04 March 2018 17:14 UTC
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From: Thomas Watteyne <thomas.watteyne@inria.fr>
Date: Sun, 04 Mar 2018 18:14:05 +0100
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Subject: [6tisch] Thomas' review of draft-richardson-6tisch-roll-enrollment-priority-00
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[co-chair hat off] This review is linked to the one I did for draft-richardson-6tisch-enrollment-enhanced-beacon-00 (https://www.ietf.org/mail-archive/web/6tisch/current/msg05767.html) as the drafts are linked. The draft is short (great), and easy to read. My comments about draft-richardson-6tisch-enrollment-enhanced-beacon-00 apply here as well, i.e. the former document should much better describe what it is trying to achieve, and why. draft-richardson-6tisch-roll-enrollment-priority-00 is almost a technical annex ("and here is how to propagate the configuration using RPL"), and IMO should be kept as short as possible, referring to draft-richardson-6tisch-enrollment-enhanced-beacon-00 for any type of discussion. There seems to be a mismatch between the two drafts, however. draft-richardson-6tisch-enrollment-enhanced-beacon-00 defines 3 priority fields (pan priority, proxy priority, rank priority), carried in a new IE in the EB. draft-richardson-6tisch-roll-enrollment-priority-00 starts by saying it defines a way to set those priorities using RPL, but in Section 2 it turns out that it defines a way to propagate something that becomes the value of the "join priority" field in the EB base header. Of course, this discrepancy needs to be resolved, but these are just editorial mechanics. The much more important discussion we need to have is regarding the policy that these two drafts allow: how are those 4 prioritie supposed to be used, and why is that needed? Only when we have come to a consensus that it is importnat to solve should be talk about the editorial work on the drafts. Below, my detailed inline comments. Thomas === 6lo Working Group M. Richardson TW> 6lo or 6tisch? Internet-Draft Sandelman Software Works Intended status: Informational February 02, 2018 Expires: August 6, 2018 Enabling secure network enrollment in RPL networks draft-richardson-6tisch-roll-enrollment-priority-00 Abstract [I-D.richardson-6tisch-join-enhanced-beacon] TW> replace by draft-richardson-6tisch-enrollment-enhanced-beacon TW> (repeat throughout this draft) defines a method by which a potential [I-D.ietf-6tisch-minimal-security] TW> word missing? "node"? can announce itself as a TW> remove "a" available for new Pledges to Join a network. The announcement includes a priority for join TW> please rephrase, which priority do you mean exactly? One of the 3? all? . This document provides a mechanism by which a RPL DODAG root can disable join announcements, TW> what is a join announcement? sending EBs? or adjust the base priority for join operation. 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 August 6, 2018. 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 to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of Richardson Expires August 6, 2018 [Page 1] Internet-Draft J-Pref DIO February 2018 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 . . . . . . . . . . . . . . . . . . . . . . . 3 2. Protocol Definition . . . . . . . . . . . . . . . . . . . . . 3 3. Security Considerations . . . . . . . . . . . . . . . . . . . 4 4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 7.1. Normative References . . . . . . . . . . . . . . . . . . 4 7.2. Informative References . . . . . . . . . . . . . . . . . 5 Appendix A. Change history . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction [RFC7554] describes the use of the time-slotted channel hopping (TSCH) mode of [ieee802154]. [I-D.ietf-6tisch-minimal-security] and [I-D.ietf-6tisch-dtsecurity-secure-join] describe mechanisms by which a new node (the "pledge)" TW> " at the wrong place can use a friendly router as a Join Proxy. [I-D.richardson-6tisch-join-enhanced-beacon] describes an extension to the 802.15.4 Enhanced Beacon TW> not really, it defines a new IE that is used by a Join Proxy to announce its existence such that Pledges can find them. It has become clear that not every routing member of the mesh ought to announce itself as a Join Proxy. There are a variety of local reasons by which a TW> an 6LR might not want to provide the Join Proxy function. They include available battery power, already committed network bandwidth, and also total available memory available for Join proxy neighbor cache slots. There are other situations where the operator of the network would like to selective enable or disable the join process in a particular DODAG. As the join process involves permitting unencrypted traffic into the best effort part of a (TSCH) network, it would be better to have the join process off when no new nodes are expected. A network operator might also be able to recognize when certain parts of the network are overloaded and can not accomodate TW> accommodate additional join traffic, and it would like to adjust the join priority among all nodes in the subtree of a congested link. Richardson Expires August 6, 2018 [Page 2] Internet-Draft J-Pref DIO February 2018 This document describes an RPL DIO option that can be used to announce a minimum join priority. TW> I'm confused about the term "join priority". There are now 4 TW> called priority: TW> - the "join priority" in the EB TW> - the "pan priority" in richardson-6tisch-join-enhanced-beacon TW> - the "proxy priority" in richardson-6tisch-join-enhanced-beacon TW> - the "rank priority" in richardson-6tisch-join-enhanced-beacon TW> which one are you concerned with? In general, I would recommend TW> to be as specific as possible, right from the abstract/intro of TW draft. This makes shorter, to the point, easier to read docs. 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. In addition, the terminology of [I-D.ietf-6tisch-terminology] and from [I-D.ietf-anima-voucher] are used. TW> why "in addition"? I would drop that statement. 2. Protocol Definition The following option is defined to transmission TW> to be transmitted? in the DIO issued by the DODAG root. It may also be added by a router TW> add "to the DIOs it generates" on part of the sub- tree TW> The concept of sub-tree introduces confusion at this point IMO. TW> I would just talk aobut a node adding the option to its DIOs. as a result of some (out of scope for this document) management function. 6LRs that see this DIO Option TW> option (casing) SHOULD increment the minimum priority if they observe congestion on the channel used for join traffic. (TODO: how much? Do we need to standardize this?) TW> at this point in the text, the "minimum priority" isn't defined. TW> move this paragraph lower, i.e. start by introducing the format, TW> then discuss how it is used? A 6LR which would otherwise be willing to act as a Join Proxy, will examine the minimum priority field, and to that number, add any additional local consideration (such as upstream congestion). The resulting priority, if less than 0x7f should enable the Join Proxy function. 0 1 2 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = TBD01|Opt Length = 1|R| min. priority | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ min.priority a 7 bit field which provides a base value for the Enhanced Beacon Join priority. A value of 0x7f (127) disables the Join Proxy function entirely. TW> hmm, OK. So now you're saying this is used for the join priority in TW> the EB. But that has nothing to do with \ TW> draft-richardson-6tisch-enrollment-enhanced-beacon R a reserved bit that SHOULD be set to 0 by senders, and MUST be ignored by receivers. The reserved bit SHOULD be copied to options created. Richardson Expires August 6, 2018 [Page 3] Internet-Draft J-Pref DIO February 2018 3. Security Considerations As per [RFC7416], RPL control frames either run over a secured layer 2, or use the [RFC6550] Secure DIO methods. This option can be placed into either a "clear" (layer-2 secured) DIO, or a layer-3 Secure DIO. As such this option will have both integrity and confidentiality mechanisms applied to it. A malicious node (that was part of the RPL control plane) could see these options and could, based upon the observed minimal join priority signal a confederate that it was a good time to send malicious join traffic. A malicious node (that was part of the RPL control plane) could also send DIOs with a different minimal join priority which would cause downstream mesh routers to change their Join Proxy behaviour. Lower minimal priorities would cause downstream nodes to accept more pledges than the network was expecting, and higher minimal priorities cause the join process to stall. The use of layer-2 or layer-3 security for RPL control messages prevents the above two attacks. 4. Privacy Considerations There are no new privacy issues caused by this extension. 5. IANA Considerations Allocate a new number TBD01 from Registry RPL Control Message Options. This entry should be called Minimum Join Priority. 6. Acknowledgements TW> Acknowledgments none so far. TW> I would replace by "TODO" 7. References 7.1. Normative References [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-04 (work in progress), October 2017. Richardson Expires August 6, 2018 [Page 4] Internet-Draft J-Pref DIO February 2018 [I-D.richardson-6tisch-join-enhanced-beacon] Dujovne, D. and M. Richardson, "IEEE802.15.4 Informational Element encapsulation of 6tisch Join Information", draft- richardson-6tisch-join-enhanced-beacon-03 (work in progress), January 2018. [ieee802154] IEEE Standard, ., "802.15.4-2015 - IEEE Standard for Low- Rate Wireless Personal Area Networks (WPANs)", 2015, <http://standards.ieee.org/findstds/ standard/802.15.4-2015.html>. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>. [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, JP., and R. Alexander, "RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks", RFC 6550, DOI 10.17487/RFC6550, March 2012, <https://www.rfc-editor.org/info/rfc6550>. [RFC7416] Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A., and M. Richardson, Ed., "A Security Threat Analysis for the Routing Protocol for Low-Power and Lossy Networks (RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015, <https://www.rfc-editor.org/info/rfc7416>. [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, <https://www.rfc-editor.org/info/rfc7554>. 7.2. Informative 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-13 (work in progress), November 2017. [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. Richardson Expires August 6, 2018 [Page 5] Internet-Draft J-Pref DIO February 2018 [I-D.ietf-6tisch-terminology] Palattella, M., Thubert, P., Watteyne, T., and Q. Wang, "Terminology in IPv6 over the TSCH mode of IEEE 802.15.4e", draft-ietf-6tisch-terminology-09 (work in progress), June 2017. [I-D.ietf-anima-voucher] Watsen, K., Richardson, M., Pritikin, M., and T. Eckert, "Voucher Profile for Bootstrapping Protocols", draft-ietf- anima-voucher-07 (work in progress), January 2018. [RFC8137] Kivinen, T. and P. Kinney, "IEEE 802.15.4 Information Element for the IETF", RFC 8137, DOI 10.17487/RFC8137, May 2017, <https://www.rfc-editor.org/info/rfc8137>. Appendix A. Change history TW> add a marker (e.g. "[TEMPORARY]") which makes it clear this section TW> will go version 00. Author's Address Michael Richardson Sandelman Software Works Email: mcr+ietf@sandelman.ca Richardson Expires August 6, 2018 [Page 6] -- ________________________________________ Thomas Watteyne, PhD Research Scientist & Innovator, Inria Sr Networking Design Eng, Analog Devices Founder & co-lead, UC Berkeley OpenWSN Co-chair, IETF 6TiSCH www.thomaswatteyne.com ________________________________________
- [6tisch] Thomas' review of draft-richardson-6tisc… Thomas Watteyne