6Lo Working Group J. Hou Internet-Draft Huawei Technologies Intended Status: Standards Track Y-G. Hong Expires: September 11, 2017 ETRI X. Tang SGEPRI March 10, 2017 Transmission of IPv6 Packets over PLC Networks draft-hou-6lo-plc-00 Abstract Power Line Communication (PLC), namely using the electric-power lines for indoor and outdoor communications, has been widely applied to support Advanced Metering Infrastructure (AMI), especially the smart meters for electricity. With the inherent advantage of existing electricity infrastructure, PLC is expanding deployments all over the world, indicating the potential demand of IPv6 for future applications. As part of this technology, Narrowband PLC (NBPLC) is focused on the low-bandwidth and low-power scenarios, including current standards such as IEEE 1901.2 and ITU-T G.9903. This document describes how IPv6 packets are transported over constrained PLC networks. Status of this Memo This Internet-Draft is submitted to IETF 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 http://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 September 11, 2017. Copyright Notice Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. Hou, et al [Page 1] INTERNET DRAFT IPv6 over PLC March 10, 2017 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements Notation and Terminology . . . . . . . . . . . . 3 3. Overview of PLC . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Protocol Stack . . . . . . . . . . . . . . . . . . . . . . 5 3.2. Addressing Modes . . . . . . . . . . . . . . . . . . . . . 5 3.3. Maximum Transmission Unit . . . . . . . . . . . . . . . . 6 4. Specification of IPv6 over Narrowband PLC . . . . . . . . . . 6 4.1. IEEE 1901.2 . . . . . . . . . . . . . . . . . . . . . . . 6 4.1.1. Stateless Address Autoconfiguration . . . . . . . . . 6 4.1.2. IPv6 Link Local Address . . . . . . . . . . . . . . . 7 4.1.3. Unicast and Multicast Address Mapping . . . . . . . . 7 4.1.4. Header Compression . . . . . . . . . . . . . . . . . . 8 4.1.5. Fragmentation and Reassembly . . . . . . . . . . . . . 9 4.2. ITU-T G.9903 . . . . . . . . . . . . . . . . . . . . . . . 9 4.2.1. Stateless Address Autoconfiguration . . . . . . . . . 9 4.2.2. IPv6 Link Local Address . . . . . . . . . . . . . . . 9 4.2.3. Unicast and Multicast Address Mapping . . . . . . . . 10 4.2.4. Header Compression . . . . . . . . . . . . . . . . . . 11 4.2.5. Fragmentation and Reassembly . . . . . . . . . . . . . 11 4.2.6. Extension at 6lo Adaptation Layer . . . . . . . . . . 12 5. Internet Connectivity Scenarios and Topologies . . . . . . . . 12 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 7. Security Consideration . . . . . . . . . . . . . . . . . . . . 14 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8.1. Normative References . . . . . . . . . . . . . . . . . . . 15 8.2. Informative References . . . . . . . . . . . . . . . . . . 15 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 1. Introduction The idea of using power line for both electricity supply and communication can be traced back to the beginning of the last century. With the obvious advantage of existing power grid, PLC is a good candidate for supporting various service scenarios such as in houses and offices, in trains and vehicles, in smart grid and Hou, et al [Page 2] INTERNET DRAFT IPv6 over PLC March 10, 2017 advanced metering infrastructure (AMI). Such applications cover the smart meters for electricity, gas and water that share the common features like fixed position, large quantity, low data rate, and long life time. Although PLC technology has an evolution history of several decades, the adaptation of PLC for IP based constrained networks is not fully developed. The 6lo related scenarios lie in the low voltage PLC networks with most applications in the area of Advanced Metering Infrastructure, Vehicle-to-Grid communications, in-home energy management and smart street lighting. It is of great importance to deploy IPv6 for PLC devices for its large address space and quick addressing. In addition, due to various existing PLC standards, a comparison among them is needed to facilitate the selection of the most applicable PLC standard in certain using scenarios. The following sections provide a brief overview of PLC, then describe transmission of IPv6 packets over PLC networks. The general approach is to adapt elements of the 6LoWPAN specifications [RFC4944], [RFC6282], and [RFC6775] to constrained PLC networks. Similar 6LoPLC adaptation layer was previously proposed in [draft-popa-6lo-6loplc], however, with the same purpose, this document provides more updated, structured and instructive information for the deployment of IPv6 over PLC networks. 2. Requirements Notation and Terminology 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 [RFC2119]. Below are the terms used in this document: 6LoWPAN: IPv6 over Low-Power Wireless Personal Area Network AMI: Advanced Metering Infrastructure BBPLC: Broadband Power Line Communication BR: Border Router HDPLC: High Definition Power Line Communication IID: Interface Identifier LAN: Local Area Network Hou, et al [Page 3] INTERNET DRAFT IPv6 over PLC March 10, 2017 LOADng: Lightweight On-demand Ad-hoc Distance-vector Routing Protocol Next Generation MSDU: MAC Service Data Unit MTU: Maximum Transmission Unit NBPLC: Narrowband Power Line Communication OFDM: Orthogonal Frequency Division Multiplexing PLC: Power Line Communication PSDU: PHY Service Data Unit RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks WAN: Wide Area Network 3. Overview of PLC PLC technology enables convenient two-way communications for home users and utility companies to monitor and control electric plugged devices such as electricity meters and street lights. Due to its large range of communication frequencies, PLC is generally classified into two categories: Narrowband PLC (NBPLC) for automation of sensors, and Broadband PLC (BBPLC) for home and industry networking applications. Various standards have been addressed on the MAC and PHY layers for this communication technology, e.g. IEEE 1901 and ITU- T G.hn for BBPLC (1.8-250 MHz), IEEE 1901.2, ITU-T G.9902 (G.hnem), ITU-T G.9903 (G3-PLC) and ITU-T G.9904 (PRIME) for NBPLC (3-500 kHz) and the recent proposal for the IEEE 1901.1 standard aiming at the frequency band of 2-12 MHz. Narrowband PLC is a very important branch of PLC technology due to its low frequency band and low power cost. So far the recent PLC standards, ITU-T G.9903 (G3-PLC) and IEEE 1901.2, are dominating as two of the most robust schemes available. Different networking methods exist in different NBPLC standards. The formation of a ITU-T G.9903 network is based on a MAC Layer routing protocol called LOADng (Lightweight On-demand Ad-hoc Distance-vector Routing Protocol Next Generation). Different from ITU-T G.9903, IEEE 1901.2 enables a variable structure of the MAC layer which can alternatively apply layer-2 or layer-3 mesh networking. IEEE 1901.2 enables a coexistence mode with ITU-T G.9903 using layer-2 LOADng protocol, and on the other hand it allows the adaptation of layer-3 RPL protocol (IPv6 Routing Protocol for Low-Power and Lossy Networks). Hou, et al [Page 4] INTERNET DRAFT IPv6 over PLC March 10, 2017 The IEEE 1901.1 WG is currently working on a new PLC standard, IEEE 1901.1, which focuses on the frequency band of 2-12 MHz [IEEE 1901.1]. This promising medium-frequency PLC standard, known as PLC- IOT, is suitable for 6lo applications thus mentioned in this document. Details on this standard is to be determined. 3.1. Protocol Stack The protocol stack for IPv6 over PLC is illustrated in Figure 1 that contains the following elements from bottom to top: PLC PHY Layer, PLC MAC Layer, Adaptation layer for IPv6 over PLC, IPv6 Layer, TCP/UDP Layer and Application Layer. The PLC MAC/PHY layer corresponds to a certain PLC standard such as IEEE 1901.2 or ITU-T G.9903. For the Broadband PLC cases, the adaptation layer for IPv6 over PLC MAY not be used unless in some certain specifications. The deployment of the 6lo adaptation layer are specified in section 4 according to different standards. Routing protocol like RPL on Network layer is optional according to the specified PLC standard, for example IEEE 1901.2 MAY use RPL protocol while ITU-T G.9903 MUST NOT. +----------------------------------------+ | Application Layer | +----------------------------------------+ | TCP/UDP | +----------------------------------------+ | | | IPv6 | | | |----------------------------------------| | Adaptation layer for IPv6 over PLC | +----------------------------------------+ | PLC MAC Layer | | (IEEE 1901.2 MAC/ITU-T G.9903 MAC) | +----------------------------------------+ | PLC PHY Layer | | (IEEE 1901.2 PHY/ITU-T G.9903 PHY) | +----------------------------------------+ Figure 1: PLC Protocol Stack 3.2. Addressing Modes Two addressing modes are enabled in PLC including the IEEE 64-bit extended address and the 16-bit short address which is unique within the PAN [IEEE 1901.2, ITU-T G.9903]. Physical addressing uses a globally unique 64-bit address to represent each node on the powerline. This is useful when initializing a system because the Hou, et al [Page 5] INTERNET DRAFT IPv6 over PLC March 10, 2017 nodes do not have unique logical addresses on power up. Logical addressing uses 16-bit short address to represent each node on the powerline with a much lower latency and higher throughput. Note that in ITU-T G.9930, though two addressing modes are enabled, only 16-bit addressing is supported in mesh routing. 3.3. Maximum Transmission Unit Maximum Transmission Unit (MTU) of MAC layer is an important parameter that determines the applicability of fragmentation and reassembly at the adaptation layer of IPv6 over PLC. IPv6 requires that every link in the Internet have an MTU of 1280 octets or greater, thus for a MAC layer with MTU lower than this limit, fragmentation and reassembly at the adaptation layer are required. As a wired communication technology, the MTU of PLC MAC layer is normally higher than wireless technology based on IEEE 802.15.4. The IEEE 1901.2 MAC layer supports the MTU of 1576 octets (the original value 1280 byte was updated in 2015 [IEEE 1901.2a]). The MTU for ITU-T G.9903 is 400 octets, insufficient for supporting complete IPv6 packets. For this concern, fragmentation/reassembly in [RFC 4944] MUST be enabled for the G.9903-based scenarios (details can be found in section 4.2.5). 4. Specification of IPv6 over Narrowband PLC Due to the narrow bandwidth and low data rate in NBPLC, a 6lo adaptation layer is needed to support the transmission of IPv6 packets. 6LoWPAN standards [RFC 4944], [RFC 6775], and [RFC 6282] provides useful functionality including link-local IPv6 addresses, stateless address auto-configuration, neighbor discovery and header compression. These standards are referred in the specifications of the 6lo adaptation layer which is illustrated in the following subsections. 4.1. IEEE 1901.2 4.1.1. Stateless Address Autoconfiguration An IEEE 1901.2 device performs stateless address autoconfiguration according to [RFC 4944] so as to obtain an IPv6 Interface Identifier (IID). In the 16-bit short addressing mode, the 64-bit IID SHALL be derived by insert 16-bit "FFEE" into a "pseudo 48-bit address" which is formed by the 16-bit PAN ID, 16-bit zero and the 16-bit short address as follows: 16_bit_PAN:00FF:FE00:16_bit_short_address Hou, et al [Page 6] INTERNET DRAFT IPv6 over PLC March 10, 2017 Considering that this derived IID is not globally unique, the "Universal/Local" (U/L) bit (7th bit) SHALL be set to zero. For the EUI-64 addressing mode, as per [RFC 2464], the Interface Identifier is then formed from by complementing the U/L bit, generally setting to 1, since an interface's built-in address is expected to be globally unique. 4.1.2. IPv6 Link Local Address The IPv6 link-local address [RFC4291] for an IEEE 1901.2 interface is formed by appending the Interface Identifier, as defined above, to the prefix FE80::/64 (see Figure 2). 10 bits 54 bits 64 bits +----------+-----------------------+----------------------------+ |1111111010| (zeros) | Interface Identifier | +----------+-----------------------+----------------------------+ Figure 2: IPv6 Link Local Address in IEEE 1901.2 4.1.3. Unicast and Multicast Address Mapping The address resolution procedure for mapping IPv6 unicast addresses into IEEE 1901.2 link-layer addresses follows the general description in section 7.2 of [RFC4861], unless otherwise specified. The Source/Target Link-layer Address option has the following forms when the link layer is IEEE 1901.2 and the addresses are EUI-64 or 16-bit short addresses, respectively. Hou, et al [Page 7] INTERNET DRAFT IPv6 over PLC March 10, 2017 0 1 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length=2 | | Type | Length=1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | 16-bit short Address | +- IEEE 1901.2 -+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | EUI-64 | | Padding | +- -+ +- -+ | | | (all zeros) | +- Address -+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +- Padding -+ | | +- (all zeros) -+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: Unicast Address Mapping in IEEE 1901.2 Option fields: Type: 1 for Source Link-layer address and 2 for Target Link-layer address. Length: This is the length of this option (including the type and length fields) in units of 8 octets. The value of this field is 2 if using EUI-64 addresses, or 1 if using 16-bit short addresses. IEEE 1901.2 Address: The 64-bit IEEE 1901.2 address, or the 16-bit short address. This is the address the interface currently responds to. This address may be different from the built-in address used to derive the Interface Identifier, because of privacy or security (e.g., of neighbor discovery) considerations. Multicast address mapping is not supported in IEEE 1901.2. A link- local multicast only reaches neighbors within direct physical connectivity. IEEE 1901.2 excludes the functionality of multicast either in [RFC 4944] or in coexistence modes with G3-PLC and PRIME. However, IEEE 1901.2 supports the required MTU by IPv6, eliminating the need of fragmentation and reassembly at the 6lo adaptation layer, so the multicast functionality in this case is applicable and is RECOMMENDED in this document. 4.1.4. Header Compression Hou, et al [Page 8] INTERNET DRAFT IPv6 over PLC March 10, 2017 The IEEE 1901.2 PHY layer supports a maximum PSDU (PHY Service Data Unit) of 512 octets while the allowed PHY payload is smaller and can change dynamically based on channel conditions. Due to the limited PHY payload, header compression at 6lo adaptation layer is of great importance and MUST be applied. The compression of IPv6 datagrams within IEEE 1901.2 frames refers to [RFC 6282], which updates [RFC 4944]. Header compression as defined in RFC6282 which specifies the fragmentation methods for IPv6 datagrams on top of IEEE 802.15.4, is REQUIRED in this document as the basis for IPv6 header compression in IEEE 1901.2. All headers MUST be compressed according to RFC6282 encoding formats. 4.1.5. Fragmentation and Reassembly To cope with the mismatch between the size of the PHY frame payload and the size of the MAC Service Data Unit (MSDU), IEEE 1901.2 MAC layer provides the functionality of segmentation and reassembly. A Segment Control Field is defined in the MAC frame header regardless of whether segmentation is required. This process segments a MAC layer datagram into multiple fragments and provides a reliable one- hop transfer of the resulting fragments. However, for the 6lo adaptation layer, since IEEE 1901.2 naturally supports a MAC payload of 1280 octets, the minimum MTU of IPv6, there is no need for fragmentation and reassembly for the IPv6 packet transmission. This document specifies that, in the IPv6 packet transmission over IEEE 1901.2, fragmentation and reassembly in [RFC 4944] MUST NOT be used. 4.2. ITU-T G.9903 4.2.1. Stateless Address Autoconfiguration The stateless address auto-configuration in ITU-T G.9903 also refers to [RFC 4944] with the following selections: The 64-bit interface identifier shall be derived from a "pseudo 48-bit address" formed with the PAN identifier and the short address as follows: 0xYYYY:00FF:FE00:XXXX where 0xYYYY is the PAN identifier and XXXX is the short address. Additional care shall be taken when choosing a PAN identifier so as not to interfere with I/G and U/L bits of the interface identifier. If the PAN identifiers are chosen randomly, then the U/L and I/G bits (7th and 8th bits) shall be set to zero [ITU-T G.9903]. 4.2.2. IPv6 Link Local Address In ITU-T G.9903, the formation of IPv6 link-local address follows the same process as IEEE 1901.2 (see section 4.1.2) by appending the Interface Identifier (IID) to the prefix FE80::/64. Hou, et al [Page 9] INTERNET DRAFT IPv6 over PLC March 10, 2017 4.2.3. Unicast and Multicast Address Mapping The address resolution procedure for mapping IPv6 unicast addresses into ITU-T G.9903 link-layer addresses follows the general description in section 7.2 of [RFC4861], unless otherwise specified. Source/Target link-layer address option field SHOULD contain the EUI- 64 address or the combined address with PAN ID and 16-bit short address of the source or target device as below. Note that the format of the Target Link-layer address in ITU-T G.9903 (see Figure 4) is specified according to the Annex E of [ITU-T G.9903]. 0 1 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length=2 | | Type | Length=1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | PAN ID | +- ITU-T G.9903 -+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | EUI-64 | | 16-bit short Address | +- -+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Address | | (all zeros) | +- -+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +- Padding -+ | | +- (all zeros) -+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Unicast Address Mapping in ITU-T G.9903 Option fields: Type: 1 for Source Link-layer address and 2 for Target Link-layer address. Length: This is the length of this option (including the type and length fields) in units of 8 octets. The value of this field is 2 if using EUI-64 addresses, or 1 if using 16-bit short addresses. ITU-T G.9903 Address: The 64-bit IEEE 1901.2 address, or the 16-bit short address. This is the address the interface currently responds to. This address may be different from the built-in address used to derive the Interface Identifier, because of privacy or security (e.g., of neighbor discovery) considerations. Hou, et al [Page 10] INTERNET DRAFT IPv6 over PLC March 10, 2017 The address resolution procedure for mapping IPv6 multicast addresses into ITU-T G.9903 link-layer addresses follows the general description in [RFC 4944] and MUST only be used in a mesh-enabled network. An IPv6 packet with a multicast destination address (DST), consisting of the sixteen octets DST[1] through DST[16], is transmitted to the following 802.15.4 16-bit multicast address (see Figure 5): 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1 0 0|DST[15]* | DST[16] | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: Multicast Address Mapping Here, DST[15]* refers to the last 5 bits in octet DST[15], that is, bits 3-7 within DST[15]. The initial 3-bit pattern of "100" follows the 16-bit address format for multicast addresses (see Section 12 of [RFC 4944]). 4.2.4. Header Compression Header compression as defined in [RFC6282], which specifies the compression format for IPv6 datagrams on top of IEEE 802.15.4, is REQUIRED in this document as the basis for IPv6 header compression in ITU-T G.9903. All headers MUST be compressed according to [RFC6282] encoding formats. 4.2.5. Fragmentation and Reassembly Similar to IEEE 1901.2, Segment Control Field is also defined in the ITU-T G.9903 MAC frame header, and the functionality of fragmentation and reassembly is also enabled at the G.9903 MAC layer. However, the maximum MAC payload size is fixed to 400 octets at the present ITU-T G.9903 recommendation, thus to cope with the required MTU of 1280 octets by IPv6, fragmentation and reassembly at 6lo adaptation layer MUST be provided referring to [RFC 4944]. To avoid the duplicate fragmentation at both 6lo adaptation layer and ITU-T G.9903 MAC layer, an optional way is to limit the MAC payload size so that the MSDU can fit the PHY payload without MAC layer fragmentation. However, the number of data bytes of the PHY payload can change dynamically based on channel conditions (see section 9.3 in [ITU-T G.9903]), so the best solution is incrementing the allowed MAC payload size above 1280 octets so as to avoid the use of fragmentation and reassembly at 6lo adaptation layer. Hou, et al [Page 11] INTERNET DRAFT IPv6 over PLC March 10, 2017 4.2.6. Extension at 6lo Adaptation Layer Apart from the 6Lo headers specified in [RFC 4944], an additional command frame header is defined for the mesh routing procedure which appears in the following order: Mesh addressing header, Broadcast header, Fragmentation header, Command frame header [ITU-T G.9903]. Figure 6 shows an example of the command frame: The ESC header type (01000000b) indicates an additional dispatch byte follows (see [RFC 4944] and [RFC 6282]). Then this 1-octet dispatch field is used as the Command frame header and filled with the Command ID. This header shall be in the last position if more than one header is present in the frame. The Command ID can be classified into 4 types: - LOADng message (0x01) - LoWPAN bootstrapping protocol message (0x02) - Reserved by ITU-T (0x03-0x0F) - CMSR protocol messages (0X10-0X1F) 0 1 2 Bits 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 +---------------+---------------+----------------- |ESC header type| | | | Command ID | Command Payload | 01 000000b | | +---------------+---------------+----------------- Figure 6: Command Frame Header Format of ITU-T G.9903 For the Mesh addressing type and header, it is worthy to note that the value of the HopsLeft field SHALL not exceed adpMaxHops. When the originator and final destination devices are neighbors (i.e., the next hop address equals the final destination address and the next hop address is present in the originator's neighbor table), the mesh header shall be omitted in the frame. 5. Internet Connectivity Scenarios and Topologies The network model can be simplified to two kinds of network devices: Border Router (BR) and Node. BR is the coordinator of the PLC subnet and can be seen as a master node while Nodes are typically PLC meters and sensors. The IPv6 over PLC networks SHOULD be built as tree, mesh or star according to the specified using scenarios. Every network requires at least one BR to communicate with each nodes. Hou, et al [Page 12] INTERNET DRAFT IPv6 over PLC March 10, 2017 One common topology in the current PLC scenarios is star. In this case, the communication at the link layer only takes place between a node and a BR. The BR collects data (e.g. smart meter reading) from different nodes, and then concentrates and uploads the data through Ethernet or LPWAN (see Figure 7). The collected data is transmitted by the smart meters through PLC, aggregated by a concentrator, sent to the utility and then to a Meter Data Management System for data storage, analysis and billing. Node Node \ / +--------- \ / / \ / + \ / | Node ------ BR =========== | Internet / \ | / \ + / \ \ / \ +--------- Node Node <----------------------> PLC subnet Figure 7: PLC Star Network connected to the Internet Tree topology is used when the distance between a node A and BR is beyond the PLC allowed limit while there is another node B in between able to communicate with both sides. Node B in this case acts both as a 6lo Node and a Proxy Coordinator (PCO). For this scenario, the link layer communications take place between node A and node B, and between node B and BR. An example of PLC tree network is depicted in Figure 8. This topology can be applied in the smart street lighting, where the lights adjust the brightness to reduce energy consumption while sensors are deployed on the street lights to give information such as wind speed, temperature, humidity. Data transmission distance in the street lighting scenario is normally above several kilometers thus the PLC tree network is required. A more sophisticated AMI network may also be constructed into the tree topology which as depicted in [RFC 8036]. Hou, et al [Page 13] INTERNET DRAFT IPv6 over PLC March 10, 2017 Node \ +--------- Node \ / \ \ + \ \ | Node --- Node ----- BR ========== | Internet / / | / / + Node --- Node / \ / +--------- Node --- Node <-------------------------> PLC subnet Figure 8: PLC Tree Network connected to the Internet Mesh networking in PLC is still under development but of great potential applications. By connecting all nodes with their neighbors in communication range (see Figure 9), mesh topology dramatically enhances the communication efficiency and thus expands the size of a PLC network. A simple use case is the smart home scenario where the ON/OFF state of air conditioning is controlled by the state of home lights (ON/OFF) and doors (OPEN/CLOSE). Node ----- Node / \ / \ +--------- / \ / \ / / \ / \ + / \ / \ | Node --- Node ---- Node ----- BR =========== | Internet \ / \ / | \ / \ / + \ / \ / \ \ / \ / +--------- Node ----- Node <---------------------------------> PLC subnet Figure 9: PLC Mesh Network connected to the Internet 6. IANA Considerations There are no IANA considerations related to this document. 7. Security Consideration Hou, et al [Page 14] INTERNET DRAFT IPv6 over PLC March 10, 2017 This document has no security consideration beyond those in [RFC 4944] and [RFC 6282]. 8. References 8.1. Normative References [IEEE 1901.2] IEEE-SA Standards Board, "IEEE Standard for Low- Frequency (less than 500 kHz) Narrowband Power Line Communications for Smart Grid Applications", IEEE 1901.2, October 2013, . [ITU-T G.9903] International Telecommunication Union, "Narrowband orthogonal frequency division multiplexing power line communication transceivers for G3-PLC networks", ITU-T G.9903, February 2014, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet Networks", RFC 2464, December 1998, . [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, September 2007, . [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, "Transmission of IPv6 Packets over IEEE 802.15.4 Networks", RFC 4944, September 2007, . [RFC6282] Hui, J. and P. Thubert, "Compression Format for IPv6 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, September 2011, . 8.2. Informative References [draft-popa-6lo-6loplc] Popa, D. and J.H. Hui, "6LoPLC: Transmission of IPv6 Packets over IEEE 1901.2 Narrowband Powerline Communication Networks", draft-popa-6lo-6loplc-ipv6-over- Hou, et al [Page 15] INTERNET DRAFT IPv6 over PLC March 10, 2017 ieee19012-networks-00, March 2014, . [IEEE 1901.1] IEEE-SA Standards Board, "Standard for Medium Frequency (less than 15 MHz) Power Line Communications for Smart Grid Applications", IEEE 1901.1, work in progress, . [IEEE 1901.2a] IEEE-SA Standards Board, "IEEE Standard for Low- Frequency (less than 500 kHz) Narrowband Power Line Communications for Smart Grid Applications - Amendment 1", IEEE 1901.2a, September 2015, . [ITU-T G.9960] International Telecommunication Union, "Unified high- speed wireline-based home networking transceivers - System architecture and physical layer specification", ITU-T G.9960, December 2011, . [ITU-T G.9961] International Telecommunication Union, "Unified high- speed wireline-based home networking transceivers - Data link layer specification", ITU-T G.9961, June 2010, . [RFC 8036] Cam-Winget, N., Hui, J. and D. Popa, "Applicability Statement for the Routing Protocol for Low-Power and Lossy Networks (RPL) in Advanced Metering Infrastructure (AMI) Networks", RFC 8036, January 2017, . 9. Acknowledgments Authors wish to thank Yizhou Li and Yuefeng Wu for their valuable comments and contributions. Authors' Addresses Jianqiang Hou Huawei Technologies 101 Software Avenue, Nanjing 210012 China Phone: +86 15852944235 Email: houjianqiang@huawei.com Hou, et al [Page 16] INTERNET DRAFT IPv6 over PLC March 10, 2017 Yong-Geun Hong Electronics and Telecommunications Research Institute 161 Gajeong-Dong Yuseung-Gu Daejeon 305-700 Korea Phone: +82 42 860 6557 Email: yghong@etri.re.kr Xiaojun Tang State Grid Electric Power Research Institute 19 Chengxin Avenue Nanjing 211106 China Phone: +86-25-81098508 Email: itc@sgepri.sgcc.com.cn Hou, et al [Page 17]