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'EUI64' == Outdated reference: A later version (-11) exists of draft-ietf-ipv6-2461bis-03 ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) -- Possible downref: Non-RFC (?) normative reference: ref. 'ieee802.15.4' Summary: 4 errors (**), 0 flaws (~~), 7 warnings (==), 9 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group N. Kushalnagar 3 Internet-Draft Intel Corp 4 Expires: January 13, 2006 G. Montenegro 5 Microsoft Corporation 6 July 12, 2005 8 6LoWPAN: Overview, Assumptions, Problem Statement and Goals 9 draft-ietf-6lowpan-problem-00.txt 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that any 14 applicable patent or other IPR claims of which he or she is aware 15 have been or will be disclosed, and any of which he or she becomes 16 aware will be disclosed, in accordance with Section 6 of BCP 79. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on January 13, 2006. 36 Copyright Notice 38 Copyright (C) The Internet Society (2005). 40 Abstract 42 This document describes the assumptions, problem statement and goals 43 for transmitting IP over IEEE 802.15.4 networks. The set of goals 44 enumerated in this document form an initial set only. Additional 45 goals may be found necessary over time and may be added to this 46 document. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 51 1.1 Requirements notation . . . . . . . . . . . . . . . . . . 3 52 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 3. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 4 54 4. Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 55 4.1 IP Connectivity . . . . . . . . . . . . . . . . . . . . . 5 56 4.2 Topologies . . . . . . . . . . . . . . . . . . . . . . . . 5 57 4.3 Limited Packet Size . . . . . . . . . . . . . . . . . . . 6 58 4.4 Limited configuration and management . . . . . . . . . . . 6 59 4.5 Service discovery . . . . . . . . . . . . . . . . . . . . 6 60 4.6 Security . . . . . . . . . . . . . . . . . . . . . . . . . 7 61 5. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 62 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 63 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 64 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 65 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 66 9.1 Normative References . . . . . . . . . . . . . . . . . . . 9 67 9.2 Informative References . . . . . . . . . . . . . . . . . . 10 68 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 10 69 Intellectual Property and Copyright Statements . . . . . . . . 11 71 1. Introduction 73 Low-power wireless personal area networks (LoWPANs) comprise devices 74 that conform to the IEEE 802.15.4-2003 standard by the IEEE 75 [ieee802.15.4]. The IEEE 802.15.4 devices are characterized by short 76 range, low bit rate, low power and low cost. 78 This document gives an overview of LoWPANs and describes how they 79 benefit from IP and IPv6 networking. It describes the requirements 80 of LoWPANs with regards to IP layer and above. It spells out the 81 underlying assumptions of IP for LoWPANs. Finally, it describes 82 problems associated with enabling IP communication between devices in 83 LoWPAN, and defines goals to address these in a prioritized manner. 84 Admittedly, not all items on this list are necessarily appropriate 85 tasks for the IETF. Nevertheless, they are documented here to give a 86 general overview of the larger problem. This is useful both to 87 structure work within the IETF as well as to understand better how to 88 coordinate with external organizations. 90 1.1 Requirements notation 92 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 93 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 94 document are to be interpreted as described in [RFC2119]. 96 2. Overview 98 A LoWPAN is a simple low cost communication network that allows 99 wireless connectivity in applications with limited power and relaxed 100 throughput requirements. A LoWPAN typically includes devices that 101 work together to connect the physical environment to real-world 102 applications, e.g., wireless sensors. LoWPANs conform to the IEEE 103 802.15.4-2003 standard. [ieee802.15.4]. 105 Some of the characteristics of LoWPANs are: 107 1. Small packet size. Given that the maximum physical layer packet 108 is 127 bytes, the resulting maximum frame size at the media 109 access control layer is 102 octets. Link-layer security imposes 110 further overhead, which in the maximum case (21 octets of 111 overhead in the AES-CCM-128 case, versus 9 and 13 for AES-CCM-32 112 and AES-CCM-64, respectively) leaves 81 octets for data packets. 114 2. Support for both 16-bit short or IEEE 64-bit extended media 115 access control addresses. 117 3. Low bandwidth. Data rates of 250 kbps, 40 kbps and 20 kbps for 118 each of the currently defined physical layers (2.4 GHz, 915 MHz 119 and 868 MHz, respectively). 121 4. Topologies include star and mesh operation. 123 5. Low power, typically battery operated. 125 6. Relatively low cost, typically associated with sensors, switches, 126 etc. These drive some of the other characteristics such as low 127 processing, low memory, etc. Numerical values for "low" have not 128 been explicitly mentioned here as historically the costs tend to 129 change over time. 131 7. Large number of devices expected to be deployed during the life- 132 time of the technology. This number is expected to dwarf the 133 number of deployed personal computers, for example. 135 8. Location of the devices are typically not predefined, thus these 136 devices are deployed in an adhoc fashion. Furthermore, sometimes 137 the location of these devices may not be easily accessible. 139 9. Devices within LoWPANs have a higher possibility of being 140 unreliable due to variety of reasons: uncertain radio 141 connectivity, battery drain, device lockups, physical tampering, 142 etc. 144 The following sections take into account these characteristics in 145 describing the assumptions, problems statement and goals for 146 LoWPANs. 148 3. Assumptions 150 Given the small packet size of LoWPANs, this document presumes 151 applications typically send small amounts of data. However, the 152 protocols themselves do not restrict bulk data transfers. 154 LoWPANs as described in this document are based on IEEE 802.15.4- 155 2003. It is possible that the specification may undergo changes in 156 the future and may change some of the requirements mentioned above. 158 Some of these assumptions are based on the limited capabilities of 159 devices within LoWPANs. As devices become more powerful, and consume 160 less power, some of the requirements mentioned above may be somewhat 161 relaxed. 163 Nevertheless, not all devices in a LoWPAN are expected to be 164 extremely limited. This is true of so-called "Reduced Function 165 Devices" (RFDs), but not necessarily of "Full Function Devices" 166 (FFDs). These will also be present albeit in much smaller numbers, 167 and will typically have more resources and be mains powered. 168 Accordingly, FFDs will aid RFDs by providing functions such as 169 network coordination, packet forwarding, interfacing with other types 170 of networks, etc. 172 IP technology is assumed to provide the following benefits: 174 1. The pervasive nature of IP networks allows use of existing 175 infrastructure. 176 2. IP based technologies already exist, are well known and proven to 177 be working. 178 3. An admittedly non-technical but important consideration is that 179 intellectual property conditions for IP networking technology are 180 either more favorable or at least better understood than 181 proprietary and newer solutions. 183 4. Problems 185 Based on the characteristics defined in the overview section, the 186 following sections elaborate on the main problems with IP for LoWPANs 187 Note that a common underlying goal is to reduce packet overhead, 188 bandwidth consumption, and processing requirements. 190 4.1 IP Connectivity 192 The requirement for IP connectivity within a LoWPAN is driven by the 193 following: 195 1. The many devices in a LoWPAN make network autoconfiguration and 196 statelessness highly desirable. And for this, IPv6 has ready 197 solutions. 198 2. The large number of devices poses the need for a large address 199 space, well met by IPv6. 200 3. Given the limited packet size of LoWPANs, the IPv6 address format 201 allows subsuming of IEEE 802.15.4 addresses if so desired. 203 However, given the limited packet size, headers for IPv6 and above 204 layers must be compressed whenever possible. 206 4.2 Topologies 208 LoWPANs must support various topologies including mesh and star. 210 Mesh topologies imply multi-hop routing. to a desired destination. 211 In this case, intermediate devices act as packet forwarders at the 212 link layer (akin to routers at the network layer). Typically these 213 are "full function devices" that have more capabilities in terms of 214 power, computation, etc. The requirements that apply on the chosen 215 routing protocol are: 217 1. Given the minimal packet size of LoWPANs, the routing protocol 218 must impose low (or no) overhead on data packets, hopefully 219 independently of the number of hops. 220 2. The routing protocols should have low routing overhead (less 221 chatty) balanced with topology changes and power conservation. 222 3. The computation and memory requirements in the routing protocol 223 should be minimal to satisfy low cost and low power 224 characteristics. Thus storage and maintaining of large routing 225 tables may be detrimental. 227 As with mesh topologies, star topologies include provisioning a 228 subset of devices with packet forwarding functionality. If, in 229 addition to IEEE 802.15.4, these devices use other kinds of network 230 interfaces such as ethernet, IEEE 802.11, etc., the goal is to 231 seamlessly integrate the networks built over those different 232 technologies. This, or course, is a primary motivation to use IP to 233 begin with. 235 4.3 Limited Packet Size 237 Applications within LoWPANs are expected to originate small packets. 238 Adding all layers for IP connectivity should still allow transmission 239 in one frame without incurring excessive fragmentation and 240 reassembly. Furthermore, protocols must be designed or chosen so 241 that the individual "control/protocol packets" fit within a single 242 802.15.4 frame. 244 4.4 Limited configuration and management 246 As alluded to above, devices within LoWPANs are expected to be 247 deployed in exceedingly large numbers. Additionally, they are 248 expected to have limited display and input capabilities. 249 Furthermore, the location of some of these devices may be hard to 250 access. As such, protocols designed for LoWPANs should have minimal 251 configuration, preferably work "out of the box", provide easy 252 bootstrapping, and should be able to self heal given the inherent 253 unreliable characteristic of these devices. The network management 254 should have less overhead yet be powerful to control dense deployment 255 of devices. 257 4.5 Service discovery 259 LoWPANs require simple service discovery network protocols to 260 discover, control and maintain services provided by devices. In some 261 cases, especially in dense deployments, abstraction of several nodes 262 to provide a service may be beneficial. In order to enable such 263 features, new protocols may have to be designed. 265 4.6 Security 267 Although IEEE 802.15.4 provides AES link layer security, a complete 268 end-to-end security is needed. 270 5. Goals 272 Goals mentioned here may point at relevant work that can be done 273 within the IETF (e.g., specification required to transmit IP, profile 274 of best practices for transmitting IP packets, and associated upper 275 level protocols, etc). It may also point at work to be done in other 276 standards bodies that exist or may exist in the future (e.g., 277 desirable changes or profiles relevant to IEEE 802.15.4, W3C, etc). 278 When the goals fall under the IETF's purview, they serve to point out 279 what those efforts should strive to accomplish. Regardless of 280 whether they are pursued within one (or more) new (or existing) 281 working groups. When the goals do not fall under the purview of the 282 IETF, documenting them here serves as input to those other 283 organizations [liaison]. 285 The following are the goals according to priority for LoWPANs: 287 1. As mentioned in the overview, the protocol data units may be as 288 small 81 bytes. This is obviously far below the minimum IPv6 289 packet size of 1280 octets, and in keeping with section 5 of the 290 IPv6 specification [RFC2460], a fragmentation and reassembly 291 adaptation layer must be provided at the layer below IP. 293 2. Given that in the worst case the maximum size available for 294 transmitting IP packets over IEEE 802.15.4 frame is 81 octets, 295 and that the IPv6 header is 40 octets long, (without optional 296 headers), this leaves only 41 octets for upper-layer protocols, 297 like UDP and TCP. UDP uses 8 octets in the header and TCP uses 298 20 octets. This leaves 33 octets for data over UDP and 21 octets 299 for data over TCP. Additionally, as pointed above, there is also 300 a need for a fragmentation and reassembly layer, which will use 301 even more octets leaving very few octets for data. Thus if one 302 were to use the protocols as is, it would lead to excessive 303 fragmentation and reassembly even when data packets are just 10s 304 of octets long. This points at the need for header compression 305 As there is much published and in-progress standardization work 306 on header compression, this goal needs to investigate using 307 existing header compression techniques and if necessary specify 308 new ones. 310 3. [I-D.ietf-ipv6-rfc2462bis] specify methods for creating IPv6 311 stateless address autoconfiguration. Stateless auto 312 configuration has an advantage over stateful by having less 313 configuration overhead on the hosts suitable for LoWPANs. The 314 goal should specify a method to generate an "interface 315 identifier" from the EUI-64 [EUI64] assigned to the IEEE 802.15.4 316 device. 318 4. A routing protocol to support a multi-hop mesh network is 319 necessary. There is much published work on adhoc multi hop 320 routing for devices. Some examples include [RFC3561], [RFC3626], 321 [RFC3684], all experimental. Also, these protocols are designed 322 to use IP based addresses that have large overheads. For 323 example, the AODV [RFC3561] routing protocol uses 48 octets for a 324 route request based on IPv6 addressing. Given the packet size 325 constraints, transmitting this packet without fragmentation and 326 reassembly may be difficult. Thus care should be taken when 327 using existing protocols or designing new protocols for routing 328 so that the routing packets fit within a single IEEE 802.15.4 329 frame. 331 5. One of the points of transmitting IPv6 packets, is to reuse 332 existing protocols as much as possible. Network management 333 functionality is critical for LoWPANs. [RFC3411] specifies 334 SNMPv3 protocol operations. SNMP functionality may be translated 335 "as is" to LoWPANs. However, further investigation is required. 336 SNMPv3 may not be the best protocol for this task. Or it may be 337 only after adapting it appropriately. 339 6. It may be the case that transmitting IP over IEEE 802.15.4 would 340 become more beneficial if implemented in a "certain" way. 341 Accordingly, implementation considerations are to be documented. 343 7. As header compression becomes more prevalent, overall performance 344 will depend even more on efficiency of application protocols. 345 Heavyweight protocols based on XML such as SOAP [SOAP], may not 346 be suitable for LoWPANs. As such, more compact encodings (and 347 perhaps protocols) may become necessary. The goal here is to 348 specify or suggest modifications to existing protocols so that it 349 is suitable for LoWPANs. Furthermore, application level 350 interoperability specifications may also become necessary in the 351 future and may thus be specified. 353 8. Security threats at different layers must be clearly understood 354 and documented. Bootstrapping of devices into a secure network 355 could also be considered given the location, limited display, 356 high density and ad hoc deployment of devices. 358 6. IANA Considerations 360 This document contains no IANA considerations. 362 7. Security Considerations 364 TBD 366 8. Acknowledgements 368 Thanks to : 370 Geoff Mulligan 372 Soohong Daniel Park 374 Samita Chakrabarti 376 Brijesh Kumar 378 for their comments and help shaping this document. 380 9. References 382 9.1 Normative References 384 [EUI64] "GUIDELINES FOR 64-BIT GLOBAL IDENTIFIER (EUI-64) 385 REGISTRATION AUTHORITY", IEEE http://standards.ieee.org/ 386 regauth/oui/tutorials/EUI64.html. 388 [I-D.ietf-ipv6-2461bis] 389 Narten, T., "Neighbor Discovery for IP version 6 (IPv6)", 390 draft-ietf-ipv6-2461bis-03 (work in progress), May 2005. 392 [I-D.ietf-ipv6-rfc2462bis] 393 Thomson, S., "IPv6 Stateless Address Autoconfiguration", 394 draft-ietf-ipv6-rfc2462bis-08 (work in progress), 395 May 2005. 397 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 398 Requirement Levels", BCP 14, RFC 2119, March 1997. 400 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 401 (IPv6) Specification", RFC 2460, December 1998. 403 [ieee802.15.4] 404 IEEE Computer Society, "IEEE Std. 802.15.4-2003", 405 October 2003. 407 9.2 Informative References 409 [RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An 410 Architecture for Describing Simple Network Management 411 Protocol (SNMP) Management Frameworks", STD 62, RFC 3411, 412 December 2002. 414 [RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On- 415 Demand Distance Vector (AODV) Routing", RFC 3561, 416 July 2003. 418 [RFC3626] Clausen, T. and P. Jacquet, "Optimized Link State Routing 419 Protocol (OLSR)", RFC 3626, October 2003. 421 [RFC3684] Ogier, R., Templin, F., and M. Lewis, "Topology 422 Dissemination Based on Reverse-Path Forwarding (TBRPF)", 423 RFC 3684, February 2004. 425 [RFC3756] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor 426 Discovery (ND) Trust Models and Threats", RFC 3756, 427 May 2004. 429 [SOAP] "SOAP", W3C http://www.w3c.org/2000/xp/Group/. 431 [liaison] "LIASONS", 432 IETF http://www.ietf.org/liaisonActivities.html. 434 Authors' Addresses 436 Nandakishore Kushalnagar 437 Intel Corp 439 Email: nandakishore.kushalnagar@intel.com 441 Gabriel Montenegro 442 Microsoft Corporation 444 Email: gabriel_montenegro_2000@yahoo.com 446 Intellectual Property Statement 448 The IETF takes no position regarding the validity or scope of any 449 Intellectual Property Rights or other rights that might be claimed to 450 pertain to the implementation or use of the technology described in 451 this document or the extent to which any license under such rights 452 might or might not be available; nor does it represent that it has 453 made any independent effort to identify any such rights. Information 454 on the procedures with respect to rights in RFC documents can be 455 found in BCP 78 and BCP 79. 457 Copies of IPR disclosures made to the IETF Secretariat and any 458 assurances of licenses to be made available, or the result of an 459 attempt made to obtain a general license or permission for the use of 460 such proprietary rights by implementers or users of this 461 specification can be obtained from the IETF on-line IPR repository at 462 http://www.ietf.org/ipr. 464 The IETF invites any interested party to bring to its attention any 465 copyrights, patents or patent applications, or other proprietary 466 rights that may cover technology that may be required to implement 467 this standard. Please address the information to the IETF at 468 ietf-ipr@ietf.org. 470 Disclaimer of Validity 472 This document and the information contained herein are provided on an 473 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 474 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET 475 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, 476 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE 477 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 478 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 480 Copyright Statement 482 Copyright (C) The Internet Society (2005). This document is subject 483 to the rights, licenses and restrictions contained in BCP 78, and 484 except as set forth therein, the authors retain all their rights. 486 Acknowledgment 488 Funding for the RFC Editor function is currently provided by the 489 Internet Society.