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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 6Lo Working Group P. Mariager 3 Internet-Draft J. Petersen, Ed. 4 Intended status: Standards Track RTX A/S 5 Expires: April 27, 2017 Z. Shelby 6 ARM 7 M. Van de Logt 8 Gigaset Communications GmbH 9 D. Barthel 10 Orange Labs 11 October 24, 2016 13 Transmission of IPv6 Packets over DECT Ultra Low Energy 14 draft-ietf-6lo-dect-ule-07 16 Abstract 18 DECT Ultra Low Energy is a low power air interface technology that is 19 defined by the DECT Forum and specified by ETSI. 21 The DECT air interface technology has been used world-wide in 22 communication devices for more than 20 years, primarily carrying 23 voice for cordless telephony but has also been deployed for data 24 centric services. 26 The DECT Ultra Low Energy is a recent addition to the DECT interface 27 primarily intended for low-bandwidth, low-power applications such as 28 sensor devices, smart meters, home automation etc. As the DECT Ultra 29 Low Energy interface inherits many of the capabilities from DECT, it 30 benefits from long range, interference free operation, world wide 31 reserved frequency band, low silicon prices and maturity. There is 32 an added value in the ability to communicate with IPv6 over DECT ULE 33 such as for Internet of Things applications. 35 This document describes how IPv6 is transported over DECT ULE using 36 6LoWPAN techniques. 38 Status of This Memo 40 This Internet-Draft is submitted in full conformance with the 41 provisions of BCP 78 and BCP 79. 43 Internet-Drafts are working documents of the Internet Engineering 44 Task Force (IETF). Note that other groups may also distribute 45 working documents as Internet-Drafts. The list of current Internet- 46 Drafts is at http://datatracker.ietf.org/drafts/current/. 48 Internet-Drafts are draft documents valid for a maximum of six months 49 and may be updated, replaced, or obsoleted by other documents at any 50 time. It is inappropriate to use Internet-Drafts as reference 51 material or to cite them other than as "work in progress." 53 This Internet-Draft will expire on April 27, 2017. 55 Copyright Notice 57 Copyright (c) 2016 IETF Trust and the persons identified as the 58 document authors. All rights reserved. 60 This document is subject to BCP 78 and the IETF Trust's Legal 61 Provisions Relating to IETF Documents 62 (http://trustee.ietf.org/license-info) in effect on the date of 63 publication of this document. Please review these documents 64 carefully, as they describe your rights and restrictions with respect 65 to this document. Code Components extracted from this document must 66 include Simplified BSD License text as described in Section 4.e of 67 the Trust Legal Provisions and are provided without warranty as 68 described in the Simplified BSD License. 70 Table of Contents 72 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 73 1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 3 74 1.2. Terms Used . . . . . . . . . . . . . . . . . . . . . . . 4 75 2. DECT Ultra Low Energy . . . . . . . . . . . . . . . . . . . . 5 76 2.1. The DECT ULE Protocol Stack . . . . . . . . . . . . . . . 5 77 2.2. Link Layer Roles and Topology . . . . . . . . . . . . . . 6 78 2.3. Addressing Model . . . . . . . . . . . . . . . . . . . . 7 79 2.4. MTU Considerations . . . . . . . . . . . . . . . . . . . 8 80 2.5. Additional Considerations . . . . . . . . . . . . . . . . 8 81 3. Specification of IPv6 over DECT ULE . . . . . . . . . . . . . 8 82 3.1. Protocol Stack . . . . . . . . . . . . . . . . . . . . . 9 83 3.2. Link Model . . . . . . . . . . . . . . . . . . . . . . . 10 84 3.3. Subnets and Internet Connectivity Scenarios . . . . . . . 14 85 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 86 5. Security Considerations . . . . . . . . . . . . . . . . . . . 16 87 6. ETSI Considerations . . . . . . . . . . . . . . . . . . . . . 17 88 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 89 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 90 8.1. Normative References . . . . . . . . . . . . . . . . . . 17 91 8.2. Informative References . . . . . . . . . . . . . . . . . 19 92 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 94 1. Introduction 96 DECT (Digital Enhanced Cordless Telecommunications) is a standard 97 series [EN300.175-part1-7] specified by ETSI and CAT-iq (Cordless 98 Advanced Technology - internet and quality) is a set of product 99 certification and interoperability profiles [CAT-iq] defined by DECT 100 Forum. DECT Ultra Low Energy (DECT ULE or just ULE) is an air 101 interface technology building on the key fundamentals of traditional 102 DECT / CAT-iq but with specific changes to significantly reduce the 103 power consumption at the expense of data throughput. DECT ULE 104 devices with requirements on power consumption as specified by ETSI 105 in [TS102.939-1] and [TS102.939-2], will operate on special power 106 optimized silicon, but can connect to a DECT Gateway supporting 107 traditional DECT / CAT-iq for cordless telephony and data as well as 108 the ULE extensions. DECT terminology operates with two major role 109 definitions: The Portable Part (PP) is the power constrained device, 110 while the Fixed Part (FP) is the Gateway or base station. This FP 111 may be connected to the Internet. An example of a use case for DECT 112 ULE is a home security sensor transmitting small amounts of data (few 113 bytes) at periodic intervals through the FP, but is able to wake up 114 upon an external event (burglar) and communicate with the FP. 115 Another example incorporating both DECT ULE as well as traditional 116 CAT-iq telephony is an elderly pendant (broche) which can transmit 117 periodic status messages to a care provider using very little 118 battery, but in the event of urgency, the elderly person can 119 establish a voice connection through the pendant to an alarm service. 120 It is expected that DECT ULE will be integrated into many residential 121 gateways, as many of these already implements DECT CAT-iq for 122 cordless telephony. DECT ULE can be added as a software option for 123 the FP. It is desirable to consider IPv6 for DECT ULE devices due to 124 the large address space and well-known infrastructure. This document 125 describes how IPv6 is used on DECT ULE links to optimize power while 126 maintaining the many benefits of IPv6 transmission. [RFC4944], 127 [RFC6282] and [RFC6775] specify the transmission of IPv6 over IEEE 128 802.15.4. DECT ULE has many characteristics similar to those of IEEE 129 802.15.4, but also differences. A subset of mechanisms defined for 130 transmission of IPv6 over IEEE 802.15.4 can be applied to the 131 transmission of IPv6 on DECT ULE links. 133 This document specifies how to map IPv6 over DECT ULE inspired by 134 [RFC4944], [RFC6282], [RFC6775] and [RFC7668]. 136 1.1. Requirements Notation 138 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 139 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 140 document are to be interpreted as described in [RFC2119]. 142 1.2. Terms Used 144 6CO: 6LoWPAN Context Option [RFC6775] 145 6BBR: 6loWPAN Backbone Router 146 6LBR: 6LoWPAN Border Router as defined in [RFC6775]. The DECT Fixed 147 Part is having this role 148 6LN: 6LoWPAN Node as defined in [RFC6775]. The DECT Portable part 149 is having this role 150 6LoWPAN: IPv6 over Low-Power Wireless Personal Area Network 151 AES128: Advanced Encryption Standard with key size of 128 bits 152 API: Application Programming Interface 153 ARO: Address Registration Option [RFC6775] 154 CAT-iq: Cordless Advanced Technology - internet and quality 155 CID: Context Identifier [RFC6775] 156 DAC: Destination Address Compression 157 DAD: Duplicate Address Detection [RFC4862] 158 DAM: Destination Address Mode 159 DHCPv6: Dynamic Host Configuration Protocol for IPv6 [RFC3315] 160 DLC: Data Link Control 161 DSAA2: DECT Standard Authentication Algorithm #2 162 DSC: DECT Standard Cipher 163 DSC2: DECT Standard Cipher #2 164 FDMA: Frequency Division Multiplex 165 FP: DECT Fixed Part, the gateway 166 GAP: Generic Access Profile 167 IID: Interface Identifier 168 IPEI: International Portable Equipment Identity; (DECT identity) 169 MAC-48: 48 bit global unique MAC address managed by IEEE 170 MAC: Media Access Control 171 MTU: Maximum Transmission Unit 172 NBMA: Non-broadcast multi-access 173 ND: Neighbor Discovery [RFC4861] [RFC6775] 174 PDU: Protocol Data Unit 175 PHY: Physical Layer 176 PMID: Portable MAC Identity; (DECT identity) 177 PP: DECT Portable Part, typically the sensor node (6LN) 178 PVC: Permanent Virtual Circuit 179 RFPI: Radio Fixed Part Identity; (DECT identity) 180 SAC: Source Address Compression 181 SAM: Source Address Mode 182 TDD: Time Division Duplex 183 TDMA: Time Division Multiplex 184 TPUI: Temporary Portable User Identity; (DECT identity) 185 UAK: User Authentication Key, DECT master security key 186 ULA: Unique Local Address [RFC4193] 188 2. DECT Ultra Low Energy 190 DECT ULE is a low power air interface technology that is designed to 191 support both circuit switched for service, such as voice 192 communication, and for packet mode data services at modest data rate. 193 This draft is only addressing the packet mode data service of DECT 194 ULE. 196 2.1. The DECT ULE Protocol Stack 198 The DECT ULE protocol stack consists of the PHY layer operating at 199 frequencies in the 1880 - 1920 MHz frequency band depending on the 200 region and uses a symbol rate of 1.152 Mbps. Radio bearers are 201 allocated by use of FDMA/TDMA/TDD techniques. 203 In its generic network topology, DECT is defined as a cellular 204 network technology. However, the most common configuration is a star 205 network with a single FP defining the network with a number of PP 206 attached. The MAC layer supports both traditional DECT circuit mode 207 operation as this is used for services like discovery, pairing, 208 security features etc, and it supports new ULE packet mode operation. 209 The circuit mode features have been reused from DECT. 211 The DECT ULE device can switch to the ULE mode of operation, 212 utilizing the new ULE MAC layer features. The DECT ULE Data Link 213 Control (DLC) provides multiplexing as well as segmentation and re- 214 assembly for larger packets from layers above. The DECT ULE layer 215 also implements per-message authentication and encryption. The DLC 216 layer ensures packet integrity and preserves packet order, but 217 delivery is based on best effort. 219 The current DECT ULE MAC layer standard supports low bandwidth data 220 broadcast. However, this document is not considering usage of the 221 DECT ULE MAC layer broadcast service for IPv6 over DECT ULE. 223 In general, communication sessions can be initiated from both FP and 224 PP side. Depending on power down modes employed in the PP, latency 225 may occur when initiating sessions from FP side. MAC layer 226 communication can take place using either connection oriented packet 227 transfer with low overhead for short sessions or take place using 228 connection oriented bearers including media reservation. The MAC 229 layer autonomously selects the radio spectrum positions that are 230 available within the band and can rearrange these to avoid 231 interference. The MAC layer has built-in retransmission procedures 232 in order to improve transmission reliability. 234 The DECT ULE device will typically incorporate an Application 235 Programmers Interface (API) as well as common elements known as 236 Generic Access Profile (GAP) for enrolling into the network. The 237 DECT ULE stack establishes a permanent virtual circuit (PVC) for the 238 application layers and provides support for a range of different 239 application protocols. The used application protocol is negotiated 240 between the PP and FP when the PVC communication service is 241 established. This draft defines 6LoWPAN as one of the possible 242 protocols to negotiate. 244 +----------------------------------------+ 245 | Application Layers | 246 +----------------------------------------+ 247 | Generic Access | ULE Profile | 248 | Profile | | 249 +----------------------------------------+ 250 | DECT/Service API | ULE Data API | 251 +--------------------+-------------------+ 252 | LLME | NWK (MM,CC)| | 253 +--------------------+-------------------+ 254 | DECT DLC | DECT ULE DLC | 255 +--------------------+-------------------+ 256 | MAC Layer | 257 +--------------------+-------------------+ 258 | PHY Layer | 259 +--------------------+-------------------+ 260 (C-plane) (U-plane) 262 Figure 1: DECT ULE Protocol Stack 264 Figure 1 above shows the DECT ULE Stack divided into the Control- 265 plane and User-data path, to left and to the right, respectively. 266 The shown entities in the Stack are the (PHY) Physical Layer, (MAC) 267 Media Access Control Layer, (DLC) Data Link Control Layer, (NWK) 268 Network Layer with subcomponents: (LLME) Lower Layer Management 269 Entity, (MM) Mobility Management and (CC) Call Control. Above there 270 are the typically (API) Application Programmers Interface and 271 application profile specific layers. 273 2.2. Link Layer Roles and Topology 275 A FP is assumed to be less constrained than a PP. Hence, in the 276 primary scenario FP and PP will act as 6LBR and a 6LN, respectively. 277 This document only addresses this primary scenario and all other 278 scenarios are out of scope. 280 In DECT ULE, at link layer the communication only takes place between 281 a FP and a PP. A FP is able to handle multiple simultaneous 282 connections with a number of PP. Hence, in a DECT ULE network using 283 IPv6, a radio hop is equivalent to an IPv6 link and vice versa (see 284 Section 3.3). 286 [DECT ULE PP]-----\ /-----[DECT ULE PP] 287 \ / 288 [DECT ULE PP]-------+[DECT ULE FP]+-------[DECT ULE PP] 289 / \ 290 [DECT ULE PP]-----/ \-----[DECT ULE PP] 292 Figure 2: DECT ULE star topology 294 A significant difference between IEEE 802.15.4 and DECT ULE is that 295 the former supports both star and mesh topology (and requires a 296 routing protocol), whereas DECT ULE in it's primary configuration 297 does not support the formation of multihop networks at the link 298 layer. In consequence, the mesh header defined in [RFC4944] for mesh 299 under routing are not used in DECT ULE networks. 301 DECT ULE repeaters are considered to operate in the DECT protocol 302 domain and are outside the scope of this document. 304 2.3. Addressing Model 306 Each DECT PP is assigned an IPEI during manufacturing. This identity 307 has the size of 40 bits and is globally unique within DECT addressing 308 space and can be used to constitute the MAC address used to derive 309 the IID for link-local address. 311 During a DECT location registration procedure, the FP assigns a 20 312 bit TPUI to a PP. The FP creates a unique mapping between the 313 assigned TPUI and the IPEI of each PP. This TPUI is used for 314 addressing (layer 2) in messages between FP and PP. Although the 315 TPUI is temporary by definition, the same value is usually repeatedly 316 assigned to any given PP, hence it seems not suitable for 317 construction of IID, see [I-D.ietf-6lo-privacy-considerations]. 319 Each DECT FP is assigned a RFPI during manufacturing. This identity 320 has the size of 40 bits and is globally unique within DECT addressing 321 space and can be used to constitute the MAC address used to derive 322 the IID for link-local address. 324 Optionally each DECT PP and DECT FP can be assigned a unique (IEEE) 325 MAC-48 address additionally to the DECT identities to be used by the 326 6LoWPAN. During the address registration of non-link-local addresses 327 as specified by this document, the FP and PP can use such MAC-48 to 328 construct the IID. However, as these addresses are considered as 329 being permanent, such scheme is not recommended as per [I-D.ietf-6lo- 330 privacy-considerations]. 332 2.4. MTU Considerations 334 Ideally the DECT ULE FP and PP may generate data that fits into a 335 single MAC Layer packets (38 octets) for periodically transferred 336 information, depending on application. However, IP packets may be 337 much larger. The DECT ULE DLC procedures natively support 338 segmentation and reassembly and provide any MTU size below 65536 339 octets. The default MTU size defined in DECT ULE [TS102.939-1] is 340 500 octets. In order to support complete IPv6 packets, the DLC layer 341 of DECT ULE shall per this specification be configured with a MTU 342 size of 1280 octets, hence [RFC4944] fragmentation/reassembly is not 343 required. 345 It is expected that the LOWPAN_IPHC packet will fulfil all the 346 requirements for header compression without spending unnecessary 347 overhead for mesh addressing. 349 It is important to realize that the usage of larger packets will be 350 at the expense of battery life, as a large packet inside the DECT ULE 351 stack will be fragmented into several or many MAC layer packets, each 352 consuming power to transmit / receive. The increased MTU size does 353 not change the MAC layer packet and PDU size. 355 2.5. Additional Considerations 357 The DECT ULE standard allows PP to be DECT-registered (bind) to 358 multiple FP and roaming between them. These FP and their 6LBR 359 functionalities can either operate individual or connected through a 360 Backbone Router as per [I-D.ietf-6lo-backbone-router]. 362 3. Specification of IPv6 over DECT ULE 364 Before any IP-layer communications can take place over DECT ULE, DECT 365 ULE enabled nodes such as 6LNs and 6LBRs have to find each other and 366 establish a suitable link-layer connection. The obtain-access-rights 367 registration and location registration procedures are documented by 368 ETSI in the specifications [EN300.175-part1-7], [TS102.939-1] and 369 [TS102.939-2]. 371 DECT ULE technology sets strict requirements for low power 372 consumption and thus limits the allowed protocol overhead. 6LoWPAN 373 standards [RFC4944], [RFC6775], and [RFC6282] provide useful 374 functionality for reducing overhead which can be applied to DECT ULE. 375 This functionality comprises link-local IPv6 addresses and stateless 376 IPv6 address autoconfiguration, Neighbor Discovery and header 377 compression. 379 The ULE 6LoWPAN adaptation layer can run directly on this U-plane DLC 380 layer. Figure 3 illustrates IPv6 over DECT ULE stack. 382 As consequence of DECT ULE in it's primary configuration does not 383 support the formation of multihop networks at the link layer, the 384 mesh header defined in [RFC4944] for mesh under routing MUST NOT be 385 used. In addition, a DECT ULE PP node MUST NOT play the role of a 386 6LoWPAN Router (6LR). 388 3.1. Protocol Stack 390 In order to enable data transmission over DECT ULE, a Permanent 391 Virtual Circuit (PVC) has to be configured and opened between FP and 392 PP. This is done by setting up a DECT service call from PP to FP. 393 In DECT protocol domain the PP SHALL specify the <> 394 in a service-change (other) message before sending a service-change 395 (resume) message as defined in [TS102.939-1]. The <> 396 SHALL define the ULE Application Protocol Identifier to 0x06 and the 397 MTU size to 1280 octets or larger. The FP sends a service-change- 398 accept (resume) that MUST contain a valid paging descriptor. The PP 399 MUST be pageable. Following this, transmission of IPv6 packets can 400 start. 402 +-------------------+ 403 | UDP/TCP/other | 404 +-------------------+ 405 | IPv6 | 406 +-------------------+ 407 |6LoWPAN adapted to | 408 | DECT ULE | 409 +-------------------+ 410 | DECT ULE DLC | 411 +-------------------+ 412 | DECT ULE MAC | 413 +-------------------+ 414 | DECT ULE PHY | 415 +-------------------+ 417 Figure 3: IPv6 over DECT ULE Stack 419 3.2. Link Model 421 The general model is that IPv6 is layer 3 and DECT ULE MAC+DLC is 422 layer 2. The DECT ULE implements already fragmentation and 423 reassembly functionality, hence [RFC4944] fragmentation and 424 reassembly function MUST NOT be used. 426 After the FP and PPs have connected at the DECT ULE level, the link 427 can be considered up and IPv6 address configuration and transmission 428 can begin. The 6LBR ensures address collisions do not occur. 430 Per this specification, the IPv6 header compression format specified 431 in [RFC6282] MUST be used. The IPv6 payload length can be derived 432 from the ULE DLC packet length and the possibly elided IPv6 address 433 can be reconstructed from the link-layer address, used at the time of 434 DECT ULE connection establishment, from the ULE MAC packet address, 435 compression context if any, and from address registration information 436 (see Section 3.2.2). 438 Due to the DECT ULE star topology (see Section 2.2), PP each have a 439 separate link to the FP, and thus the PPs cannot directly hear one 440 another and cannot talk to one another. As discussed in [RFC4903], 441 conventional usage of IPv6 anticipates IPv6 subnets spanning a single 442 link at the link layer. In order avoid the complexity of 443 implementing separate subnet for each DECT ULE link, a Multi-Link 444 Subnet model has been chosen, specifically Non-broadcast multi-access 445 (NBMA) at layer 2. Because of this, link-local multicast 446 communications can happen only within a single DECT ULE connection; 447 thus, 6LN-to-6LN communications using link-local addresses are not 448 possible. 6LNs connected to the same 6LBR have to communicate with 449 each other by using the shared prefix used on the subnet. The 6LBR 450 forwards packets sent by one 6LN to another. 452 3.2.1. Stateless Address Autoconfiguration 454 At network interface initialization, both 6LN and 6LBR SHALL generate 455 and assign to the DECT ULE network interface IPv6 link-local 456 addresses [RFC4862] based on the DECT device addresses (see 457 Section 2.3) that were used for establishing the underlying DECT ULE 458 connection. 460 The DECT device addresses IPEI and RFPI MUST be used to derive the 461 IPv6 link-local 64 bit Interface Identifiers (IID) for 6LN and 6LBR, 462 respectively. 464 The rule for deriving IID from DECT device addresses is as follows: 465 The DECT device addresses that are consisting of 40 bits each, MUST 466 be expanded with leading zero bits to form 48 bit intermediate 467 addresses. Most significant bit in this newly formed 48-bit 468 intermediate address is set to one for addresses derived from the 469 RFPI and set to zero for addresses derived from the IPEI. From these 470 intermediate 48 bit addresses are derived 64 bit IIDs similar to the 471 guidance of [RFC4291]. However, because DECT and IEEE address spaces 472 are different, this intermediate address cannot be considered as 473 unique within IEEE address space. In the derived IIDs the U/L bit 474 (7th bit) will be zero, indicating that derived IID's are not 475 globally unique, see [RFC7136]. For example from RFPI=11.22.33.44.55 476 the derived IID is 80:11:22:ff:fe:33:44:55 and from 477 IPEI=01.23.45.67.89 the derived IID is 00:01:23:ff:fe:45:67:89. 479 Globally uniqueness of IID in link-local addresses are not required 480 as they should never be leaked outside the subnet domain. 482 As defined in [RFC4291], the IPv6 link-local address is formed by 483 appending the IID, to the prefix FE80::/64, as shown in Figure 4. 485 10 bits 54 bits 64 bits 486 +----------+-----------------+----------------------+ 487 |1111111010| zeros | Interface Identifier | 488 +----------+-----------------+----------------------+ 490 Figure 4: IPv6 link-local address in DECT ULE 492 A 6LN MUST join the all-nodes multicast address. 494 After link-local address configuration, 6LN sends Router Solicitation 495 messages as described in [RFC4861] Section 6.3.7 and [RFC6775] 496 Section 5.3. 498 For non-link-local addresses, 6LNs SHOULD NOT be configured to use 499 IIDs derived from a MAC-48 device address or DECT device addresses. 500 Alternative schemes such as Cryptographically Generated Addresses 501 (CGAs) [RFC3972], privacy extensions [RFC4941], Hash-Based Addresses 502 (HBAs) [RFC5535], DHCPv6 [RFC3315], or static, semantically opaque 503 addresses [RFC7217] SHOULD be used by default. See also [I-D.ietf- 504 6lo-privacy-considerations] for guidance of needed entropy in IIDs. 505 When generated IID's are not globally unique, Duplicate Address 506 Detection (DAD) [RFC4862] MUST be used. In situations where the 507 devices address embedded in the IID are required to support 508 deployment constraints, 6LN MAY form a 64-bit IID by utilizing the 509 MAC-48 device address or DECT device addresses. The non-link-local 510 addresses that a 6LN generates MUST be registered with 6LBR as 511 described in Section 3.2.2. 513 The means for a 6LBR to obtain an IPv6 prefix for numbering the DECT 514 ULE network is out of scope of this document, but can be, for 515 example, accomplished via DHCPv6 Prefix Delegation [RFC3633] or by 516 using Unique Local IPv6 Unicast Addresses (ULA) [RFC4193]. Due to 517 the link model of the DECT ULE the 6LBR MUST set the "on-link" flag 518 (L) to zero in the Prefix Information Option [RFC4861]. This will 519 cause 6LNs to always send packets to the 6LBR, including the case 520 when the destination is another 6LN using the same prefix. 522 3.2.2. Neighbor Discovery 524 'Neighbor Discovery Optimization for IPv6 over Low-Power Wireless 525 Personal Area Networks (6LoWPANs)' [RFC6775] describes the neighbor 526 discovery approach as adapted for use in several 6LoWPAN topologies, 527 including the mesh topology. As DECT ULE is considered not to 528 support mesh networks, hence only those aspects that apply to a star 529 topology are considered. 531 The following aspects of the Neighbor Discovery optimizations 532 [RFC6775] are applicable to DECT ULE 6LNs: 534 1. For sending Router Solicitations and processing Router 535 Advertisements the DECT ULE 6LNs MUST, respectively, follow Sections 536 5.3 and 5.4 of the [RFC6775]. 538 2. A DECT ULE 6LN MUST NOT register its link-local address. Because 539 the IIDs used in link-local addresses are derived from DECT 540 addresses, there will always exist a unique mapping between link- 541 local and layer-2 addresses. 543 3. A DECT ULE 6LN MUST register its non-link-local addresses with 544 the 6LBR by sending a Neighbor Solicitation (NS) message with the 545 Address Registration Option (ARO) and process the Neighbor 546 Advertisement (NA) accordingly. The NS with the ARO option MUST be 547 sent irrespective of the method used to generate the IID. 549 3.2.3. Unicast and Multicast Address Mapping 551 The DECT MAC layer broadcast service is considered inadequate for IP 552 multicast. 554 Hence traffic is always unicast between two DECT ULE nodes. Even in 555 the case where a 6LBR is attached to multiple 6LNs, the 6LBR cannot 556 do a multicast to all the connected 6LNs. If the 6LBR needs to send 557 a multicast packet to all its 6LNs, it has to replicate the packet 558 and unicast it on each link. However, this may not be energy- 559 efficient and particular care should be taken if the FP is battery- 560 powered. To further conserve power, the 6LBR MUST keep track of 561 multicast listeners at DECT-ULE link level granularity and it MUST 562 NOT forward multicast packets to 6LNs that have not registered for 563 multicast groups the packets belong to. In the opposite direction, a 564 6LN can only transmit data to or through the 6LBR. Hence, when a 6LN 565 needs to transmit an IPv6 multicast packet, the 6LN will unicast the 566 corresponding DECT ULE packet to the 6LBR. The 6LBR will then 567 forward the multicast packet to other 6LNs. 569 3.2.4. Header Compression 571 Header compression as defined in [RFC6282], which specifies the 572 compression format for IPv6 datagrams on top of IEEE 802.15.4, is 573 REQUIRED in this document as the basis for IPv6 header compression on 574 top of DECT ULE. All headers MUST be compressed according to 575 [RFC6282] encoding formats. The DECT ULE's star topology structure, 576 ARO and 6CO can be exploited in order to provide a mechanism for 577 address compression. The following text describes the principles of 578 IPv6 address compression on top of DECT ULE. 580 3.2.4.1. Link-local Header Compression 582 In a link-local communication terminated at 6LN and 6LBR, both the 583 IPv6 source and destination addresses MUST be elided, since the used 584 IIDs map uniquely into the DECT link end point addresses. A 6LN or 585 6LBR that receives a PDU containing an IPv6 packet can infer the 586 corresponding IPv6 source address. For the unicast type of 587 communication considered in this paragraph, the following settings 588 MUST be used in the IPv6 compressed header: CID=0, SAC=0, SAM=11, 589 DAC=0, DAM=11. 591 3.2.4.2. Non-link-local Header Compression 593 To enable efficient header compression, the 6LBR MUST include 6LoWPAN 594 Context Option (6CO) [RFC6775] for all prefixes the 6LBR advertises 595 in Router Advertisements for use in stateless address 596 autoconfiguration. 598 When a 6LN transmits an IPv6 packet to a destination using global 599 Unicast IPv6 addresses, if a context is defined for the prefix of the 600 6LNs global IPv6 address, the 6LN MUST indicate this context in the 601 corresponding source fields of the compressed IPv6 header as per 602 Section 3.1 of [RFC6282], and MUST fully elide the latest registered 603 IPv6 source address. For this, the 6LN MUST use the following 604 settings in the IPv6 compressed header: CID=1, SAC=1, SAM=11. In 605 this case, the 6LBR can infer the elided IPv6 source address since 1) 606 the 6LBR has previously assigned the prefix to the 6LNs; and 2) the 607 6LBR maintains a Neighbor Cache that relates the Device Address and 608 the IID of the corresponding PP. If a context is defined for the 609 IPv6 destination address, the 6LN MUST also indicate this context in 610 the corresponding destination fields of the compressed IPv6 header, 611 and MUST elide the prefix of the destination IPv6 address. For this, 612 the 6LN MUST set the DAM field of the compressed IPv6 header as 613 CID=1, DAC=1 and DAM=01 or DAM=11. Note that when a context is 614 defined for the IPv6 destination address, the 6LBR can infer the 615 elided destination prefix by using the context. 617 When a 6LBR receives a IPv6 packet having a global Unicast IPv6 618 address, and the destination of the packet is a 6LN, if a context is 619 defined for the prefix of the 6LN's global IPv6 address, the 6LBR 620 MUST indicate this context in the corresponding destination fields of 621 the compressed IPv6 header, and MUST fully elide the IPv6 destination 622 address of the packet if the destination address is the latest 623 registered by the 6LN for the indicated context. For this, the 6LBR 624 MUST set the DAM field of the IPv6 compressed header as DAM=11. CID 625 and DAC MUST be set to CID=1 and DAC=1. If a context is defined for 626 the prefix of the IPv6 source address, the 6LBR MUST indicate this 627 context in the source fields of the compressed IPv6 header, and MUST 628 elide that prefix as well. For this, the 6LBR MUST set the SAM field 629 of the IPv6 compressed header as CID=1, SAC=1 and SAM=01 or SAM=11. 631 3.3. Subnets and Internet Connectivity Scenarios 633 In the DECT ULE star topology (see Section 2.2), PP each have a 634 separate link to the FP and the FP acts as an IPv6 router rather than 635 a link-layer switch. A Multi-Link Subnet model [RFC4903] has been 636 chosen, specifically Non-broadcast multi-access (NBMA) at layer 2 as 637 further illustrated in Figure 5. The 6LBR forwards packets sent by 638 one 6LN to another. In a typical scenario, the DECT ULE network is 639 connected to the Internet as shown in the Figure 5. In this 640 scenario, the DECT ULE network is deployed as one subnet, using one 641 /64 IPv6 prefix. The 6LBR is acting as router and forwarding packets 642 between 6LNs and to and from Internet. 644 6LN 645 \ ____________ 646 \ / \ 647 6LN ---- 6LBR ------ | Internet | 648 / \____________/ 649 / 650 6LN 652 <-- One subnet --> 653 <-- DECT ULE --> 655 Figure 5: DECT ULE network connected to the Internet 657 In some scenarios, the DECT ULE network may transiently or 658 permanently be an isolated network as shown in the Figure 6. In this 659 case the whole DECT ULE network consists of a single subnet with 660 multiple links, where 6LBR is routing packets between 6LNs. 662 6LN 6LN 663 \ / 664 \ / 665 6LN --- 6LBR --- 6LN 666 / \ 667 / \ 668 6LN 6LN 670 <---- One subnet ----> 671 <------ DECT ULE -----> 673 Figure 6: Isolated DECT ULE network 675 In the isolated network scenario, communications between 6LN and 6LBR 676 can use IPv6 link-local methodology, but for communications between 677 different PP, the FP has to act as 6LBR, number the network with ULA 678 prefix [RFC4193], and route packets between PP. 680 In other more advanced systems scenarios with multiple FP and 6LBR, 681 each DECT ULE FP constitutes a wireless cell. The network can be 682 configured as a Multi-Link Subnet, in which the can 6LN operate 683 within the same /64 subnet prefix in multiple cells as shown in the 684 Figure 7. The FPs operation role in such scenario are rather like 685 Backbone Routers (6BBR) than 6LBR, as per [I-D.ietf-6lo-backbone- 686 router]. 688 ____________ 689 / \ 690 | Internet | 691 \____________/ 692 | 693 | 694 | 695 | 696 6BBR/ | 6BBR/ 697 6LN ---- 6LBR -------+------- 6LBR ---- 6LN 698 / \ / \ 699 / \ / \ 700 6LN 6LN 6LN 6LN 702 <------------------One subnet ------------------> 703 <-- DECT ULE Cell --> <-- DECT ULE Cell --> 705 Figure 7: Multiple DECT ULE cells in a single Multi-Link subnet 707 4. IANA Considerations 709 There are no IANA considerations related to this document. 711 5. Security Considerations 713 The secure transmission of speech over DECT will be based on the 714 DSAA2 and DSC/DSC2 specification developed by ETSI TC DECT and the 715 ETSI SAGE Security expert group. 717 DECT ULE communications are secured at the link-layer (DLC) by 718 encryption and per-message authentication through CCM mode (Counter 719 with CBC-MAC) similar to [RFC3610]. The underlying algorithm for 720 providing encryption and authentication is AES128. 722 The DECT ULE pairing procedure generates a master authentication key 723 (UAK). During location registration procedure or when the permanent 724 virtual circuit are established, the session security keys are 725 generated. Session security keys may be renewed regularly. The 726 generated security keys (UAK and session security keys) are 727 individual for each FP-PP binding, hence all PP in a system have 728 different security keys. DECT ULE PPs do not use any shared 729 encryption key. 731 From privacy point of view, the IPv6 link-local address configuration 732 described in Section 3.2.1 only reveals information about the 6LN to 733 the 6LBR that the 6LBR already knows from the link-layer connection. 734 For non-link-local IPv6 addresses, by default a 6LN SHOULD use a 735 randomly generated IID, for example, as discussed in [I-D.ietf-6man- 736 default-iids], or use alternative schemes such as Cryptographically 737 Generated Addresses (CGA) [RFC3972], privacy extensions [RFC4941], 738 Hash-Based Addresses (HBA, [RFC5535]), or static, semantically opaque 739 addresses [RFC7217]. 741 6. ETSI Considerations 743 ETSI is standardizing a list of known application layer protocols 744 that can use the DECT ULE permanent virtual circuit packet data 745 service. Each protocol is identified by a unique known identifier, 746 which is exchanged in the service-change procedure as defined in 747 [TS102.939-1]. The IPv6/6LoWPAN as described in this document is 748 considered as an application layer protocol on top of DECT ULE. In 749 order to provide interoperability between 6LoWPAN / DECT ULE devices 750 a common protocol identifier for 6LoWPAN is standardized by ETSI. 752 The ETSI DECT ULE Application Protocol Identifier is specified to 753 0x06 for 6LoWPAN [TS102.939-1]. 755 7. Acknowledgements 757 We are grateful to the members of the IETF 6lo working group; this 758 document borrows liberally from their work. 760 Ralph Droms, Samita Chakrabarti, Kerry Lynn, Suresh Krishnan, Pascal 761 Thubert and Tatuya Jinmei have provided valuable feedback for this 762 draft. 764 8. References 766 8.1. Normative References 768 [EN300.175-part1-7] 769 ETSI, "Digital Enhanced Cordless Telecommunications 770 (DECT); Common Interface (CI);", March 2015, 771 . 775 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 776 Requirement Levels", BCP 14, RFC 2119, 777 DOI 10.17487/RFC2119, March 1997, 778 . 780 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 781 Host Configuration Protocol (DHCP) version 6", RFC 3633, 782 DOI 10.17487/RFC3633, December 2003, 783 . 785 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 786 Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, 787 . 789 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 790 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 791 2006, . 793 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 794 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 795 DOI 10.17487/RFC4861, September 2007, 796 . 798 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 799 Address Autoconfiguration", RFC 4862, 800 DOI 10.17487/RFC4862, September 2007, 801 . 803 [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy 804 Extensions for Stateless Address Autoconfiguration in 805 IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007, 806 . 808 [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, 809 "Transmission of IPv6 Packets over IEEE 802.15.4 810 Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007, 811 . 813 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 814 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 815 DOI 10.17487/RFC6282, September 2011, 816 . 818 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 819 Bormann, "Neighbor Discovery Optimization for IPv6 over 820 Low-Power Wireless Personal Area Networks (6LoWPANs)", 821 RFC 6775, DOI 10.17487/RFC6775, November 2012, 822 . 824 [RFC7136] Carpenter, B. and S. Jiang, "Significance of IPv6 825 Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136, 826 February 2014, . 828 [TS102.939-1] 829 ETSI, "Digital Enhanced Cordless Telecommunications 830 (DECT); Ultra Low Energy (ULE); Machine to Machine 831 Communications; Part 1: Home Automation Network (phase 832 1)", March 2015, . 836 [TS102.939-2] 837 ETSI, "Digital Enhanced Cordless Telecommunications 838 (DECT); Ultra Low Energy (ULE); Machine to Machine 839 Communications; Part 2: Home Automation Network (phase 840 2)", March 2015, . 844 8.2. Informative References 846 [CAT-iq] DECT Forum, "Cordless Advanced Technology - internet and 847 quality", January 2016, 848 . 851 [I-D.ietf-6lo-backbone-router] 852 Thubert, P., "IPv6 Backbone Router", draft-ietf-6lo- 853 backbone-router-02 (work in progress), September 2016. 855 [I-D.ietf-6lo-privacy-considerations] 856 Thaler, D., "Privacy Considerations for IPv6 over Networks 857 of Resource-Constrained Nodes", draft-ietf-6lo-privacy- 858 considerations-03 (work in progress), September 2016. 860 [I-D.ietf-6man-default-iids] 861 Gont, F., Cooper, A., Thaler, D., and S. LIU, 862 "Recommendation on Stable IPv6 Interface Identifiers", 863 draft-ietf-6man-default-iids-16 (work in progress), 864 September 2016. 866 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 867 C., and M. Carney, "Dynamic Host Configuration Protocol 868 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 869 2003, . 871 [RFC3610] Whiting, D., Housley, R., and N. Ferguson, "Counter with 872 CBC-MAC (CCM)", RFC 3610, DOI 10.17487/RFC3610, September 873 2003, . 875 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 876 RFC 3972, DOI 10.17487/RFC3972, March 2005, 877 . 879 [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903, 880 DOI 10.17487/RFC4903, June 2007, 881 . 883 [RFC5535] Bagnulo, M., "Hash-Based Addresses (HBA)", RFC 5535, 884 DOI 10.17487/RFC5535, June 2009, 885 . 887 [RFC7217] Gont, F., "A Method for Generating Semantically Opaque 888 Interface Identifiers with IPv6 Stateless Address 889 Autoconfiguration (SLAAC)", RFC 7217, 890 DOI 10.17487/RFC7217, April 2014, 891 . 893 [RFC7668] Nieminen, J., Savolainen, T., Isomaki, M., Patil, B., 894 Shelby, Z., and C. Gomez, "IPv6 over BLUETOOTH(R) Low 895 Energy", RFC 7668, DOI 10.17487/RFC7668, October 2015, 896 . 898 Authors' Addresses 900 Peter B. Mariager 901 RTX A/S 902 Stroemmen 6 903 DK-9400 Noerresundby 904 Denmark 906 Email: pm@rtx.dk 908 Jens Toftgaard Petersen (editor) 909 RTX A/S 910 Stroemmen 6 911 DK-9400 Noerresundby 912 Denmark 914 Email: jtp@rtx.dk 915 Zach Shelby 916 ARM 917 150 Rose Orchard 918 San Jose, CA 95134 919 USA 921 Email: zach.shelby@arm.com 923 Marco van de Logt 924 Gigaset Communications GmbH 925 Frankenstrasse 2 926 D-46395 Bocholt 927 Germany 929 Email: marco.van-de-logt@gigaset.com 931 Dominique Barthel 932 Orange Labs 933 28 chemin du Vieux Chene 934 38243 Meylan 935 France 937 Email: dominique.barthel@orange.com