--- 1/draft-ietf-roll-rpl-observations-06.txt 2021-11-29 20:13:09.213929317 -0800 +++ 2/draft-ietf-roll-rpl-observations-07.txt 2021-11-29 20:13:09.241929672 -0800 @@ -1,21 +1,21 @@ -ROLL R. Jadhav, Ed. +ROLL R.A. Jadhav, Ed. Internet-Draft -Intended status: Standards Track R. Sahoo -Expires: December 5, 2021 Juniper +Intended status: Standards Track R.N. Sahoo +Expires: 2 June 2022 Juniper Y. Wu Huawei - June 3, 2021 + 29 November 2021 RPL Observations - draft-ietf-roll-rpl-observations-06 + draft-ietf-roll-rpl-observations-07 Abstract This document describes RPL protocol design issues, various observations and possible consequences of the design and implementation choices. Status of This Memo This Internet-Draft is submitted in full conformance with the @@ -24,89 +24,88 @@ 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 December 5, 2021. + This Internet-Draft will expire on 2 June 2022. Copyright Notice Copyright (c) 2021 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 - the Trust Legal Provisions and are provided without warranty as - described in the Simplified BSD License. + 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 Revised BSD License text as + described in Section 4.e of the Trust Legal Provisions and are + provided without warranty as described in the Revised BSD License. Table of Contents 1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Requirements Language and Terminology . . . . . . . . . . 3 3. DTSN increment in storing MOP . . . . . . . . . . . . . . . . 4 3.1. Deliberations . . . . . . . . . . . . . . . . . . . . . . 5 4. DAO retransmission and use of DAO-ACK in storing MOP . . . . 5 - 4.1. Significance of bidirectional Path establishment - indication and relevance of DAO-ACK . . . . . . . . . . . 6 + 4.1. Significance of bidirectional Path establishment indication + and relevance of DAO-ACK . . . . . . . . . . . . . . . . 6 4.2. Problems with hop-by-hop DAO-ACK . . . . . . . . . . . . 6 4.3. Problems with end-to-end DAO-ACK . . . . . . . . . . . . 6 4.4. Deliberations . . . . . . . . . . . . . . . . . . . . . . 6 4.5. Implementation Notes . . . . . . . . . . . . . . . . . . 7 5. Interpreting Trickle Timer . . . . . . . . . . . . . . . . . 7 6. Handling resource unavailability . . . . . . . . . . . . . . 8 6.1. Deliberations . . . . . . . . . . . . . . . . . . . . . . 8 7. Handling aggregated targets . . . . . . . . . . . . . . . . . 9 7.1. Deliberations . . . . . . . . . . . . . . . . . . . . . . 9 8. RPL Transit Information in DAO . . . . . . . . . . . . . . . 9 8.1. Deliberations . . . . . . . . . . . . . . . . . . . . . . 10 9. Upgrades or Extensions to RPL protocol . . . . . . . . . . . 10 10. Path Control bits handling . . . . . . . . . . . . . . . . . 10 11. Asymmetric Links and RPL . . . . . . . . . . . . . . . . . . 11 - 12. Adjacencies probing with RPL . . . . . . . . . . . . . . . . 11 + 12. Adjacencies probing with RPL . . . . . . . . . . . . . . . . 12 12.1. Deliberations . . . . . . . . . . . . . . . . . . . . . 12 13. Control Options eliding mechanism in RPL . . . . . . . . . . 12 14. Managing persistent variables across node reboots . . . . . . 12 - 14.1. Persistent storage and RPL state information . . . . . . 12 + 14.1. Persistent storage and RPL state information . . . . . . 13 14.2. Lollipop Counters . . . . . . . . . . . . . . . . . . . 13 14.3. RPL State variables . . . . . . . . . . . . . . . . . . 14 - 14.3.1. DODAG Version . . . . . . . . . . . . . . . . . . . 14 - 14.3.2. DTSN field in DIO . . . . . . . . . . . . . . . . . 14 + 14.3.1. DODAG Version . . . . . . . . . . . . . . . . . . . 15 + 14.3.2. DTSN field in DIO . . . . . . . . . . . . . . . . . 15 14.3.3. PathSequence . . . . . . . . . . . . . . . . . . . . 15 - 14.4. State variables update frequency . . . . . . . . . . . . 15 - 14.5. Deliberations . . . . . . . . . . . . . . . . . . . . . 15 + 14.4. State variables update frequency . . . . . . . . . . . . 16 + 14.5. Deliberations . . . . . . . . . . . . . . . . . . . . . 16 14.6. Implementation Notes . . . . . . . . . . . . . . . . . . 16 - 15. Capabilities and its role in RPL . . . . . . . . . . . . . . 16 - 15.1. Handshaking node capabilities . . . . . . . . . . . . . 16 + 15. Capabilities and its role in RPL . . . . . . . . . . . . . . 17 + 15.1. Handshaking node capabilities . . . . . . . . . . . . . 17 15.2. How do Capabilities differ from MOP and Configuration Option? . . . . . . . . . . . . . . . . . . . . . . . . 17 15.3. Deliberations . . . . . . . . . . . . . . . . . . . . . 17 - 16. Backward Compatibility issues with RPL Options . . . . . . . 17 - 17. RPL under-specification . . . . . . . . . . . . . . . . . . . 17 + 16. Backward Compatibility issues with RPL Options . . . . . . . 18 + 17. RPL under-specification . . . . . . . . . . . . . . . . . . . 18 18. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 - 19. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 - 20. Security Considerations . . . . . . . . . . . . . . . . . . . 18 - 21. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 - 21.1. Normative References . . . . . . . . . . . . . . . . . . 18 + 19. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 + 20. Security Considerations . . . . . . . . . . . . . . . . . . . 19 + 21. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 + 21.1. Normative References . . . . . . . . . . . . . . . . . . 19 21.2. Informative References . . . . . . . . . . . . . . . . . 19 - Appendix A. Additional Stuff . . . . . . . . . . . . . . . . . . 19 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 + Appendix A. Additional Stuff . . . . . . . . . . . . . . . . . . 20 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 1. Motivation The primary motivation for this draft is to enlist different issues with RPL operation and invoke a discussion within the working group. This draft by itself is not intended for RFC tracks but as a WG discussion track. This draft may in turn result in other work items taken up by the WG which may improvise on the issues mentioned herewith. @@ -604,38 +600,47 @@ this seqcnt and node B uses this seqcnt to determine whether the information node A sent in the packet is latest. Now lets assume, the counter value reaches 250 after some operations on Node A, and node B keeps receiving updated seqcnt from node A. Now consider that node A reboots, and since it reinitializes the seqcnt value to 240 and sends the information to node B (who has seqcnt of 250 stored on behalf of node A). As per section 7.2. of [RFC6550], when node B receives this packet it will consider the information to be old (since 240 < 250). - +-----+-----+----------+ + +=====+=====+==========+ | A | B | Output | - +-----+-----+----------+ + +=====+=====+==========+ | 240 | 240 | AB, new | + +-----+-----+----------+ | 240 | :: | A>B, new | + +-----+-----+----------+ | 240 | 127 | A>B, new | +-----+-----+----------+ + Table 1: Example + lollipop counter + operation + Default values for lollipop counters considered from [RFC6550] Section 7.2. - Table 1: Example lollipop counter operation - Based on this figure, there is dead zone (240 to 0) in which if A operates after reboot then the seqcnt will always be considered smaller. Thus node A needs to maintain the seqcnt in persistent storage and reuse this on reboot. 14.3. RPL State variables The impact of loss of RPL state information differs depending upon the node type (6LN/6LR/6LBR). Following sections explain different state variables and the impact in case this information is lost on @@ -678,32 +683,34 @@ Target option. A node whichs owns a target address can associate a PathSequence in the DAO message to denote freshness of the target information. This is especially useful when a node uses multiple paths or multiple parents to advertise its reachability. Loss of PathSequence information maintained on the target node can result in routing adjacencies been lost on 6LRs/6LBR/6BBR. 14.4. State variables update frequency - +--------------------+-------------------+------------------------+ + +====================+===================+========================+ | State variable | Update frequency | Impacts node type | - +--------------------+-------------------+------------------------+ + +====================+===================+========================+ | DODAGVersionNumber | Low | 6LBR, 6LR(local DODAG) | + +--------------------+-------------------+------------------------+ | DTSN | High(SM),Low(NSM) | 6LBR, 6LR | + +--------------------+-------------------+------------------------+ | PathSequence | High(SM),Low(NSM) | 6LR, 6LN | +--------------------+-------------------+------------------------+ - Low=<5 per day, High=>5 per day; SM=Storing MOP, NSM=Non-Storing MOP - Table 2: RPL State variables + Low=<5 per day, High=>5 per day; SM=Storing MOP, NSM=Non-Storing MOP + 14.5. Deliberations (1) Is it possible that RPL removes the use of persistent storage for maintaining state information? (2) In most cases, the node reboots will happen very rarely. Thus doing a persistent storage book-keeping for handling node reboot might not make sense. Is it possible to consider signaling (especially after the node reboots) so as to avoid maintaining this persistent state? Is it possible to use one-time on-reboot @@ -854,55 +861,65 @@ Bormann, "Neighbor Discovery Optimization for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)", RFC 6775, DOI 10.17487/RFC6775, November 2012, . 21.2. Informative References [I-D.clausen-lln-rpl-experiences] Clausen, T., Verdiere, A. C. D., Yi, J., Herberg, U., and Y. Igarashi, "Observations on RPL: IPv6 Routing Protocol - for Low power and Lossy Networks", draft-clausen-lln-rpl- - experiences-11 (work in progress), March 2018. + for Low power and Lossy Networks", Work in Progress, + Internet-Draft, draft-clausen-lln-rpl-experiences-11, 27 + March 2018, . [I-D.ietf-intarea-adhoc-wireless-com] Baccelli, E. and C. E. Perkins, "Multi-hop Ad Hoc Wireless - Communication", draft-ietf-intarea-adhoc-wireless-com-02 - (work in progress), July 2016. + Communication", Work in Progress, Internet-Draft, draft- + ietf-intarea-adhoc-wireless-com-02, 20 July 2016, + . [I-D.ietf-roll-aodv-rpl] - Anamalamudi, S., Zhang, M., Perkins, C. E., Anand, S., and - B. Liu, "Supporting Asymmetric Links in Low Power - Networks: AODV-RPL", draft-ietf-roll-aodv-rpl-10 (work in - progress), April 2021. + Anamalamudi, S., Perkins, C. E., Anand, S., and B. Liu, + "Supporting Asymmetric Links in Low Power Networks: AODV- + RPL", Work in Progress, Internet-Draft, draft-ietf-roll- + aodv-rpl-11, 16 September 2021, + . [Perlman83] Perlman, R., "Fault-Tolerant Broadcast of Routing Information", North-Holland Computer Networks, Vol.7, December 1983. Appendix A. Additional Stuff Authors' Addresses Rahul Arvind Jadhav (editor) Marathahalli - Bangalore, Karnataka 560037 + Bangalore 560037 + Karnataka India Email: rahul.ietf@gmail.com + Rabi Narayan Sahoo Juniper Whitefield - Bangalore, Karnataka 560037 + Bangalore 560037 + Karnataka India Email: rabinarayans0828@gmail.com Yuefeng Wu Huawei No.101, Software Avenue, Yuhuatai District, - Nanjing, Jiangsu 210012 + Nanjing + Jiangsu, 210012 China Phone: +86-15251896569 Email: wuyuefeng@huawei.com