ROLL P. Thubert, Ed. Internet-Draft Cisco Systems Updates: 6550 (if approved) D. Barthel Intended status: Standards Track Orange Labs Expires: 17 April 2020 R.A. Jadhav Huawei Tech 15 October 2019 Eliding and Querying RPL Information draft-thubert-roll-eliding-dio-information-00 Abstract This document presents a method to elide a group of global RPL options by synchonizing the state associated with each of these options between parent and child using a new sequence counter in DIO messages. A child that missed a DIO message with an update of any of those protected options detects it by the change of sequence counter and queries the update with a DIS Message. 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 17 April 2020. Copyright Notice Copyright (c) 2019 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 Thubert, et al. Expires 17 April 2020 [Page 1] Internet-Draft Eliding RPL Info October 2019 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 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. References . . . . . . . . . . . . . . . . . . . . . . . 3 2.3. Glossary . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Updating RFC 6550 . . . . . . . . . . . . . . . . . . . . . . 4 4. New RPL Configuration State Sequence . . . . . . . . . . . . 4 5. Protected Options . . . . . . . . . . . . . . . . . . . . . . 5 6. Child Operation . . . . . . . . . . . . . . . . . . . . . . . 6 7. Pulling Options . . . . . . . . . . . . . . . . . . . . . . . 7 8. Security Considerations . . . . . . . . . . . . . . . . . . . 7 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 10. Security Considerations . . . . . . . . . . . . . . . . . . . 7 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 12. Normative References . . . . . . . . . . . . . . . . . . . . 7 13. Informative References . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 1. Introduction Classical Link State protocol synchronize their Link State Database (LSDB) by sequencing every change. Each interested node maintains the last sequence of the LSDB it is synchronizing with. If a last known sequence is older than the current, the node needs to learn one by one all the state changes between the last known and the current state. [RPL] does not operate that way. With RPL, the routing information is repeated over and over in DODAG Information Object (DIO) and Destination Advertisement Object (DAO) messages. There is no concept of synchronization. The most recent information overrides a previous one and a stale state eventually times out. The RPL way was designed to enable routing from most nodes to most nodes most of the time in a Low-Power Lossy Network (LLN) where the quality of the links and the cost of communications does not permit to maintain a permanent synchronization. This principle was applied to both the routing information and non-routing state such as configuration settings, prefix information, and node capabilities. This non-routing state may be needed to decide whether a node can join a network as a leaf or as a router, and may affect the parent Thubert, et al. Expires 17 April 2020 [Page 2] Internet-Draft Eliding RPL Info October 2019 selection. [RPL] allows a parent to elide that information in the DIO it sends repeatedly, but if it does so, a newcomer child may have missed the early DIOs that contained the configuration option and live with only partial information. If it is pessimistic, it may query all possible information even when it is not needed. Conversely, a node that slept may have missed a DIO message with a change in some critical information and not be aware of it, so it may fail to query for the update and operate on deprecated parameters. This document uses a new sequence counter to synchronize the state in a child node with that of its parent, and recursively with that of the network. 2. Terminology 2.1. BCP 14 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119][RFC8174] when, and only when, they appear in all capitals, as shown here. 2.2. References The Terminology used in this document is consistent with and incorporates that described in Terms Used in Routing for Low-Power and Lossy Networks (LLNs). [RFC7102]. Other terms in use in LLNs are found in Terminology for Constrained-Node Networks [RFC7228]. A glossary of classical RPL acronyms is given in Section 2.3. The term "byte" is used in its now customary sense as a synonym for "octet". "RPL", "RPL Packet Information" (RPI) and "RPL Instance", DIO, DAO and DIS messages are defined in the "RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks" [RPL] specification. This document uses the terms RPL-Unaware Leaf (RUL) and RPL Aware Leaf (RAL) consistently with [USE_OF_RPL_INFO]. The term RPL-Unaware Leaf (RUL) is used to refer to a node that uses a RPL router (without necessarily knowing it) as 6LR and depends on that router to obtain reachability for its addresses inside the RPL domain. On the contrary, the term RPL-Aware Node (RAN) is used to Thubert, et al. Expires 17 April 2020 [Page 3] Internet-Draft Eliding RPL Info October 2019 refer to a RAL or a RPL router that participates to RPL and advertises its addresses of prefixes by itself. 2.3. Glossary This document often uses the following acronyms: DODAG Destination-Oriented Directed Acyclic Graph LLN Low-Power and Lossy Network RPI RPL Packet Information (an Option in the Hop-By_Hop Header) RAL RPL-Aware Leaf RAN RPL-Aware Node, a RPL router or a RPL-Aware Leaf RS Router Solicitation RPL IPv6 Routing Protocol for LLNs (pronounced ripple) RUL RPL-Unaware Leaf 3. Updating RFC 6550 This document adds a sequence counter called RPL Configuration State Sequence (RCSS) to the DIO message. The RCSS is set by the root and operated as specified in Section 7 of [RPL], more in Section 4. This document introduces a new RPL Control Message Options called the Abbreviated Option Option (AOO). The AOO is an empty replacement of an existing option that indicates the RCSS of the last change of that option. This document modifies the Solicited Information Option to enable the individual query of the protected options by a node that missed a change, more in Section 7. 4. New RPL Configuration State Sequence The format of the DIO Base Object is defined in section 6.3.1 of [RPL]. This specification uses a 8th octet that was previously reserved to transport the RCSS. Thubert, et al. Expires 17 April 2020 [Page 4] Internet-Draft Eliding RPL Info October 2019 0 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RPLInstanceID |Version Number | Rank | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |G|0| MOP | Prf | DTSN | Flags | RCSS | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + DODAGID + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option(s)... +-+-+-+-+-+-+-+-+ Figure 1: MOdified DIO Base Object Updated fields: RCSS One Byte, the RPL Configuration State Sequence The RCSS protects network-wide options that are set by the root and that are propagated without a change down the DODAG. The RCSS MUST be incremented when the root sends a DIO where at least one of the protected options is modified. It MUST propagated down without a change together with the options that it protects. During the straight part of the lollipop, a second reboot of the root might not be recognized and a same value of the RCSS may appear with new values in the protected options. For that reason the protected options MUST be present in the DIOs during the straight part of the lollipop and the root SHOULD move rapidly away from the straight part once the network has settled by resetting the RCSS to 0, which places the RCSS in the circular region of the lollipop. 5. Protected Options The protected options are: 1. The Route Information Option (RIO) defined in section 6.7.5 of [RPL] 2. The DODAG Configuration Option (DCO) defined in section 6.7.6 of [RPL] Thubert, et al. Expires 17 April 2020 [Page 5] Internet-Draft Eliding RPL Info October 2019 3. The Prefix Information Option (PIO) defined in section 6.7.10 of [RPL] 4. The Extended MOP Option (MOPex) defined in [MOPEX-CAP] 5. The Global Capabilities Option (GCO) defined in [MOPEX-CAP] When a protected option is unchanged from the previous DIOs, the root MAY replace it with its abbreviated version. The abbreviated version of an option is transported in a 4-bytes long Abbreviated Option Option (AOO). The AOO indicates the RCSS at which the protected option was last changed. 0 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 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option Type | Option Length | Abbrev. opt. | Last Mod RCSS | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Abbreviated Option Option Format Option fields: Option Type One byte indicating "Abbreviated Option", see Table 1 Option Length MUST be set to 2 indicating Option data of 2 bytes Abbreviated Option The Option Type of the option being abreviated Last Modification RCSS The RCSS at which the option was last modified 6. Child Operation When a field is modified in one of the protected options in a fashion that may affect the routing or forwarding decision inside the DODAG, the root MUST send a DIO with the protected options. Unchanged options may be abreviated as discussed in Section 5. The freshness of the protected options is asserted based on the RCSS. RCSS values are compared as described in section 7.2 of [RPL]. When a parent exposes a new RCSS, the child node SHOULD refrain from using that parent until it has resynchronized all the protected fields to the latest. When it is resynchronized, the child SHOULD refrain from using other parents that expose an older RCSS. Thubert, et al. Expires 17 April 2020 [Page 6] Internet-Draft Eliding RPL Info October 2019 A child MUST store the content of all the protected options and keep track of the RCSS of the DIO where each of these option was last seen in a non-abbreviated version. If that RCSS is fresher than the Last Modification RCSS in the abbreviated version of the option then the child is up-to-date for that option. If a protected option elided in a DIO and not abbreviated, and the child has a stored RCSS value for that option that is lower than the RCSS in the DIO, then the child MUST query that option from the parent to ensure that is has the latest. This is done with a DIS message as indicated in Section 7. 7. Pulling Options 8. Security Considerations TBD 9. IANA Considerations A new entries is required for the new option of type "Abbreviated Option", from the "RPL Control Message Options" space defined for [RPL]. +----------+--------------------+-----------+ | Value | Meaning | Reference | +==========+====================+===========+ | TBD IANA | Abbreviated Option | THIS RFC | +----------+--------------------+-----------+ Table 1: New Option Type 10. Security Considerations TBD 11. Acknowledgments 12. Normative References [MOPEX-CAP] Jadhav, R. and P. Thubert, "Mode of Operation extension and Capabilities", Internet-Draft, draft-ietf-roll-mopex- cap-00, 9 August 2019, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, Thubert, et al. Expires 17 April 2020 [Page 7] Internet-Draft Eliding RPL Info October 2019 DOI 10.17487/RFC2119, March 1997, . [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January 2014, . [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for Constrained-Node Networks", RFC 7228, DOI 10.17487/RFC7228, May 2014, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RPL] 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, . [USE_OF_RPL_INFO] Robles, I., Richardson, M., and P. Thubert, "Using RPL Option Type, Routing Header for Source Routes and IPv6-in- IPv6 encapsulation in the RPL Data Plane", Internet-Draft, draft-ietf-roll-useofrplinfo-31, 7 August 2019, . 13. Informative References Authors' Addresses Pascal Thubert (editor) Cisco Systems, Inc Building D, 45 Allee des Ormes - BP1200 06254 Mougins - Sophia Antipolis France Phone: +33 497 23 26 34 Email: pthubert@cisco.com Dominique Barthel Orange Labs 28 chemin du Vieux Chêne Thubert, et al. Expires 17 April 2020 [Page 8] Internet-Draft Eliding RPL Info October 2019 38243 Meylan France Email: dominique.barthel@orange.com Rahul Arvind Jadhav Huawei Tech Kundalahalli Village, Whitefield, Bangalore 560037 Karnataka India Phone: +91-080-49160700 Email: rahul.ietf@gmail.com Thubert, et al. Expires 17 April 2020 [Page 9]