Network Working Group M. Richardson Internet-Draft Sandelman Software Works Intended status: Standards Track W. Pan Expires: 28 December 2022 Huawei Technologies 26 June 2022 Inter-Gateway Discovery and Communications in Building Automation Systems draft-richardson-snac-building-use-case-00 Abstract This document describes a use case where gateways need to discover each other in order to maintain building safety systems 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 28 December 2022. Copyright Notice Copyright (c) 2022 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 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. Richardson & Pan Expires 28 December 2022 [Page 1] Internet-Draft building-gateway June 2022 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Building Network Topology . . . . . . . . . . . . . . . . 2 1.2. Scope of problem . . . . . . . . . . . . . . . . . . . . 3 2. Privacy Considerations . . . . . . . . . . . . . . . . . . . 4 3. Security Considerations . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 6. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 4 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 7.1. Normative References . . . . . . . . . . . . . . . . . . 4 7.2. Informative References . . . . . . . . . . . . . . . . . 4 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction XXX - Intra-Gateway or Inter-Gateway? This document describes a scenario where gateway to gateway discovery is needed in order to maintain a series of building safety systems. New Buildings are being built with digitally controlled automation, and existing buildings are being retrofitted with new automation systems. While some buildings can and do leverage legacy wiring systems such as BACnet, and able to deploy technology like [RFC8163] to turn existing twisted pair control systems into IPv6 networks, other buildings are using various combinations of 802.15.4, Powerline ethernet, etc. as an alternative to explicit wiring. Whether wired or wireless passing of a signal through re-inforced concrete floors presents a challenge, particularly in the retrofit situation. 1.1. Building Network Topology The sheer height of many buildings means that even per-floor gateways may be more than 100m away (copper ethernet distance) from the control room. The distance issue then requires that fiber be used to connect the building, or that sub-control rooms be established at regular intervals. Richardson & Pan Expires 28 December 2022 [Page 2] Internet-Draft building-gateway June 2022 As an alternative to this resulting star topology, with many critical points, a daisy-chain topology can be established, where the gateways on adjacent floors (or areas) are directly connected. To provide redundancy an additional cable can connect alternating floors, ideally via a different conduit. A routing protocol such as [RFC6550] can be used, or a metro-ethernet topology can be used to connect the gateways. This deals with the Layer 1 and Layer 2 resiliency in face of destruction of the control room, or the conduits leading to the control room. But what about the resiliency at layer 4 and at the application layer? Regulations often say that when a smoke detector is tripped in one area that some or all adjacent areas need also to signal for occupants to leave. Emergency doors and stairwells need to be unlocked, emergency lighting and communications systems activated. 1.2. Scope of problem Many industrial settings can assume a competent operator to plan and manage the network. On the other hand, the HOMENET problem description assumes that there is no such operator [RFC7368]. In the building case there is a hybrid situation. For most of the regular, boring operation of the building there is a central point of control, a human operator is reachable, and maintenance people or processes can be deployed. It is during an emergency that the problems arise. The central point of control and the humans involved may become unavailable due to network partition, or because there are other things occupying their attention. This document presents the problem of having (network) adjacent gateways being able discover each other and interoperate with each other's sensor network from a just powered on situation. The criteria of just powered on does not imply a factory default situation. This criteria is to acknowledge that the power situation might be unstable: batteries and backup generators might not come on immediately, but there could be some short duration when power is unstable. As a result, any kind of configuration or network convergence that depends upon connectivity that would exist during regular operation can not be assumed. A key point about the just powered-on situation is that it assumes that any mesh network (whether [RFC6550] or Metro-Ring) may not have formed yet, and may never form. Richardson & Pan Expires 28 December 2022 [Page 3] Internet-Draft building-gateway June 2022 A network forming with [RFC6550] would normally do address assignment from the PIOs contained in the DODAGs. For stability, resiliency, and ease of deployment, the Gateway devices would likely number their sensors using either a ULA locally generated, or via an IPv6 prefix allocated via DHCPv6-PD using an extremely long (essentially infinite) lifetime. The Gateways could advertise their prefixes into a [RFC6550] mesh using DAO messages. (On a network built using a metro-ring protocol, then the entire gateway network is a single L2 domain, and a single OSPF area could be created) Note that [RFC6550] includes support for non-Grounded DODAGs (no DODAG root) which would permit adjacent nodes to communicate and form a DAG, it is unclear yet if that mechanism can be used for this. 2. Privacy Considerations To be considered. 3. Security Considerations Something about building networks and physical security. 4. IANA Considerations None. 5. Acknowledgements Hello. 6. Changelog 7. References 7.1. Normative References [BCP14] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 7.2. Informative References [diehard] McTiernan, J., McTiernan, J., and Twentieth Century Fox, "Die Hard", 1988. Richardson & Pan Expires 28 December 2022 [Page 4] Internet-Draft building-gateway June 2022 [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, . [RFC7368] Chown, T., Ed., Arkko, J., Brandt, A., Troan, O., and J. Weil, "IPv6 Home Networking Architecture Principles", RFC 7368, DOI 10.17487/RFC7368, October 2014, . [RFC8163] Lynn, K., Ed., Martocci, J., Neilson, C., and S. Donaldson, "Transmission of IPv6 over Master-Slave/Token- Passing (MS/TP) Networks", RFC 8163, DOI 10.17487/RFC8163, May 2017, . Authors' Addresses Michael Richardson Sandelman Software Works Email: mcr+ietf@sandelman.ca Wei Pan Huawei Technologies Email: william.panwei@huawei.com Richardson & Pan Expires 28 December 2022 [Page 5]