idnits 2.17.1 draft-ietf-mboned-ieee802-mcast-problems-13.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (February 4, 2021) is 1171 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Missing Reference: 'ICMPv6' is mentioned on line 588, but not defined -- Looks like a reference, but probably isn't: '1' on line 1130 == Unused Reference: 'RFC5796' is defined on line 1065, but no explicit reference was found in the text Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Area C. Perkins 3 Internet-Draft Blue Meadow Networks 4 Intended status: Informational M. McBride 5 Expires: August 8, 2021 Futurewei 6 D. Stanley 7 HPE 8 W. Kumari 9 Google 10 JC. Zuniga 11 SIGFOX 12 February 4, 2021 14 Multicast Considerations over IEEE 802 Wireless Media 15 draft-ietf-mboned-ieee802-mcast-problems-13 17 Abstract 19 Well-known issues with multicast have prevented the deployment of 20 multicast in 802.11 (wifi) and other local-area wireless 21 environments. This document describes the problems of known 22 limitations with wireless (primarily 802.11) Layer-2 multicast. Also 23 described are certain multicast enhancement features that have been 24 specified by the IETF, and by IEEE 802, for wireless media, as well 25 as some operational choices that can be taken to improve the 26 performance of the network. Finally, some recommendations are 27 provided about the usage and combination of these features and 28 operational choices. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at https://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on August 8, 2021. 47 Copyright Notice 49 Copyright (c) 2021 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (https://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 65 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 66 3. Identified multicast issues . . . . . . . . . . . . . . . . . 5 67 3.1. Issues at Layer 2 and Below . . . . . . . . . . . . . . . 5 68 3.1.1. Multicast reliability . . . . . . . . . . . . . . . . 5 69 3.1.2. Lower and Variable Data Rate . . . . . . . . . . . . 6 70 3.1.3. Capacity and Impact on Interference . . . . . . . . . 7 71 3.1.4. Power-save Effects on Multicast . . . . . . . . . . . 7 72 3.2. Issues at Layer 3 and Above . . . . . . . . . . . . . . . 7 73 3.2.1. IPv4 issues . . . . . . . . . . . . . . . . . . . . . 8 74 3.2.2. IPv6 issues . . . . . . . . . . . . . . . . . . . . . 8 75 3.2.3. MLD issues . . . . . . . . . . . . . . . . . . . . . 9 76 3.2.4. Spurious Neighbor Discovery . . . . . . . . . . . . . 9 77 4. Multicast protocol optimizations . . . . . . . . . . . . . . 10 78 4.1. Proxy ARP in 802.11-2012 . . . . . . . . . . . . . . . . 10 79 4.2. IPv6 Address Registration and Proxy Neighbor Discovery . 11 80 4.3. Buffering to Improve Battery Life . . . . . . . . . . . . 12 81 4.4. Limiting multicast buffer hardware queue depth . . . . . 13 82 4.5. IPv6 support in 802.11-2012 . . . . . . . . . . . . . . . 13 83 4.6. Using Unicast Instead of Multicast . . . . . . . . . . . 14 84 4.6.1. Overview . . . . . . . . . . . . . . . . . . . . . . 14 85 4.6.2. Layer 2 Conversion to Unicast . . . . . . . . . . . . 14 86 4.6.3. Directed Multicast Service (DMS) . . . . . . . . . . 14 87 4.6.4. Automatic Multicast Tunneling (AMT) . . . . . . . . . 15 88 4.7. GroupCast with Retries (GCR) . . . . . . . . . . . . . . 15 89 5. Operational optimizations . . . . . . . . . . . . . . . . . . 16 90 5.1. Mitigating Problems from Spurious Neighbor Discovery . . 16 91 5.2. Mitigating Spurious Service Discovery Messages . . . . . 18 92 6. Multicast Considerations for Other Wireless Media . . . . . . 18 93 7. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 19 94 8. On-going Discussion Items . . . . . . . . . . . . . . . . . . 19 95 9. Security Considerations . . . . . . . . . . . . . . . . . . . 20 96 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 97 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 98 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 99 12.1. Informative References . . . . . . . . . . . . . . . . . 21 100 12.2. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 25 101 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 103 1. Introduction 105 Well-known issues with multicast have prevented the deployment of 106 multicast in 802.11 [dot11] and other local-area wireless 107 environments, as described in [mc-props], [mc-prob-stmt]. 108 Performance issues have been observed when multicast packet 109 transmissions of IETF protocols are used over IEEE 802 wireless 110 media. Even though enhancements for multicast transmissions have 111 been designed at both IETF and IEEE 802, incompatibilities still 112 exist between specifications, implementations and configuration 113 choices. 115 Many IETF protocols depend on multicast/broadcast for delivery of 116 control messages to multiple receivers. Multicast allows sending 117 data to multiple interested recipients without the source needing to 118 send duplicate data to each recipient. With broadcast traffic, data 119 is sent to every device regardless of their interest in the data. 120 Multicast is used for various purposes such as neighbor discovery, 121 network flooding, address resolution, as well minimizing media 122 occupancy for the transmission of data that is intended for multiple 123 receivers. In addition to protocol use of broadcast/multicast for 124 control messages, more applications, such as push to talk in 125 hospitals, or video in enterprises, universities, and homes, are 126 sending multicast IP to end user devices, which are increasingly 127 using Wi-Fi for their connectivity. 129 IETF protocols typically rely on network protocol layering in order 130 to reduce or eliminate any dependence of higher level protocols on 131 the specific nature of the MAC layer protocols or the physical media. 132 In the case of multicast transmissions, higher level protocols have 133 traditionally been designed as if transmitting a packet to an IP 134 address had the same cost in interference and network media access, 135 regardless of whether the destination IP address is a unicast address 136 or a multicast or broadcast address. This model was reasonable for 137 networks where the physical medium was wired, like Ethernet. 138 Unfortunately, for many wireless media, the costs to access the 139 medium can be quite different. Multicast over Wi-Fi has often been 140 plagued by such poor performance that it is disallowed. Some 141 enhancements have been designed in IETF protocols that are assumed to 142 work primarily over wireless media. However, these enhancements are 143 usually implemented in limited deployments and not widespread on most 144 wireless networks. 146 IEEE 802 wireless protocols have been designed with certain features 147 to support multicast traffic. For instance, lower modulations are 148 used to transmit multicast frames, so that these can be received by 149 all stations in the cell, regardless of the distance or path 150 attenuation from the base station or access point. However, these 151 lower modulation transmissions occupy the medium longer; they hamper 152 efficient transmission of traffic using higher order modulations to 153 nearby stations. For these and other reasons, IEEE 802 working 154 groups such as 802.11 have designed features to improve the 155 performance of multicast transmissions at Layer 2 [ietf_802-11]. In 156 addition to protocol design features, certain operational and 157 configuration enhancements can ameliorate the network performance 158 issues created by multicast traffic, as described in Section 5. 160 There seems to be general agreement that these problems will not be 161 fixed anytime soon, primarily because it's expensive to do so and due 162 to multicast being unreliable. Compared to unicast over Wi-Fi, 163 multicast is often treated as somewhat of a second class citizen, 164 even though there are many protocols using multicast. Something 165 needs to be provided in order to make them more reliable. IPv6 166 neighbor discovery saturating the Wi-Fi link is only part of the 167 problem. Wi-Fi traffic classes may help. This document is intended 168 to help make the determination about what problems should be solved 169 by the IETF and what problems should be solved by the IEEE (see 170 Section 8). 172 This document details various problems caused by multicast 173 transmission over wireless networks, including high packet error 174 rates, no acknowledgements, and low data rate. It also explains some 175 enhancements that have been designed at the IETF and IEEE 802.11 to 176 ameliorate the effects of multicast traffic. Recommendations are 177 also provided to implementors about how to use and combine these 178 enhancements. Some advice about the operational choices that can be 179 taken is also included. It is likely that this document will also be 180 considered relevant to designers of future IEEE wireless 181 specifications. 183 2. Terminology 185 This document uses the following definitions: 187 ACK 188 The 802.11 layer 2 acknowledgement 190 AP 191 IEEE 802.11 Access Point 193 basic rate 194 The slowest rate of all the connected devices, at which multicast 195 and broadcast traffic is generally transmitted 197 DTIM 198 Delivery Traffic Indication Map (DTIM): An information element 199 that advertises whether or not any associated stations have 200 buffered multicast or broadcast frames 202 MCS 203 Modulation and Coding Scheme 205 NOC 206 Network Operations Center 208 PER 209 Packet Error Rate 211 STA 212 802.11 station (e.g. handheld device) 214 TIM 215 Traffic Indication Map (TIM): An information element that 216 advertises whether or not any associated stations have buffered 217 unicast frames 219 3. Identified multicast issues 221 3.1. Issues at Layer 2 and Below 223 In this section some of the issues related to the use of multicast 224 transmissions over IEEE 802 wireless technologies are described. 226 3.1.1. Multicast reliability 228 Multicast traffic is typically much less reliable than unicast 229 traffic. Since multicast makes point-to-multipoint communications, 230 multiple acknowledgements would be needed to guarantee reception at 231 all recipients. Since there are no ACKs for multicast packets, it is 232 not possible for the Access Point (AP) to know whether or not a 233 retransmission is needed. Even in the wired Internet, this 234 characteristic often causes undesirably high error rates. This has 235 contributed to the relatively slow uptake of multicast applications 236 even though the protocols have long been available. The situation 237 for wireless links is much worse, and is quite sensitive to the 238 presence of background traffic. Consequently, there can be a high 239 packet error rate (PER) due to lack of retransmission, and because 240 the sender never backs off. It is not uncommon for there to be a 241 packet loss rate of 5% or more, which is particularly troublesome for 242 video and other environments where high data rates and high 243 reliability are required. 245 3.1.2. Lower and Variable Data Rate 247 Multicast over wired differs from multicast over wireless because 248 transmission over wired links often occurs at a fixed rate. Wi-Fi, 249 on the other hand, has a transmission rate that varies depending upon 250 the STA's proximity to the AP. The throughput of video flows, and 251 the capacity of the broader Wi-Fi network, will change and will 252 impact the ability for QoS solutions to effectively reserve bandwidth 253 and provide admission control. 255 For wireless stations associated with an Access Point, the power 256 necessary for good reception can vary from station to station. For 257 unicast, the goal is to minimize power requirements while maximizing 258 the data rate to the destination. For multicast, the goal is simply 259 to maximize the number of receivers that will correctly receive the 260 multicast packet; generally the Access Point has to use a much lower 261 data rate at a power level high enough for even the farthest station 262 to receive the packet, for example as briefly mentioned in section 2 263 of [RFC5757]. Consequently, the data rate of a video stream, for 264 instance, would be constrained by the environmental considerations of 265 the least reliable receiver associated with the Access Point. 267 Because more robust modulation and coding schemes (MCSs) have longer 268 range but also lower data rate, multicast / broadcast traffic is 269 generally transmitted at the slowest rate of all the connected 270 devices. This is also known as the basic rate. The amount of 271 additional interference depends on the specific wireless technology. 272 In fact, backward compatibility and multi-stream implementations mean 273 that the maximum unicast rates are currently up to a few Gbps, so 274 there can be more than 3 orders of magnitude difference in the 275 transmission rate between multicast / broadcast versus optimal 276 unicast forwarding. Some techniques employed to increase spectral 277 efficiency, such as spatial multiplexing in MIMO systems, are not 278 available with more than one intended receiver; it is not the case 279 that backwards compatibility is the only factor responsible for lower 280 multicast transmission rates. 282 Wired multicast also affects wireless LANs when the AP extends the 283 wired segment; in that case, multicast / broadcast frames on the 284 wired LAN side are copied to the Wireless Local Area Network (WLAN). 286 Since broadcast messages are transmitted at the most robust MCS, many 287 large frames are sent at a slow rate over the air. 289 3.1.3. Capacity and Impact on Interference 291 Transmissions at a lower rate require longer occupancy of the 292 wireless medium and thus take away from the airtime of other 293 communications and degrade the overall capacity. Furthermore, 294 transmission at higher power, as is required to reach all multicast 295 STAs associated to the AP, proportionately increases the area of 296 interference. 298 3.1.4. Power-save Effects on Multicast 300 One of the characteristics of multicast transmission is that every 301 station has to be configured to wake up to receive the multicast, 302 even though the received packet may ultimately be discarded. This 303 process can have a large effect on the power consumption by the 304 multicast receiver station. For this reason there are workarounds, 305 such as Directed Multicast Service (DMS) described in Section 4, to 306 prevent unnecessarily waking up stations. 308 Multicast can work poorly with the power-save mechanisms defined in 309 IEEE 802.11e, for the following reasons. 311 o Clients may be unable to stay in sleep mode due to multicast 312 control packets frequently waking them up. 313 o Both unicast and multicast traffic can be delayed by power-saving 314 mechanisms. 315 o A unicast packet is delayed until an STA wakes up and requests it. 316 Unicast traffic may also be delayed to improve power save, 317 efficiency and increase probability of aggregation. 318 o Multicast traffic is delayed in a wireless network if any of the 319 STAs in that network are power savers. All STAs associated to the 320 AP have to be awake at a known time to receive multicast traffic. 321 o Packets can also be discarded due to buffer limitations in the AP 322 and non-AP STA. 324 3.2. Issues at Layer 3 and Above 326 This section identifies some representative IETF protocols, and 327 describes possible negative effects due to performance degradation 328 when using multicast transmissions for control messages. Common uses 329 of multicast include: 331 o Control plane signaling 332 o Neighbor Discovery 333 o Address Resolution 334 o Service Discovery 335 o Applications (video delivery, stock data, etc.) 336 o On-demand routing 337 o Backbone construction 338 o Other L3 protocols (non-IP) 340 User Datagram Protocol (UDP) is the most common transport layer 341 protocol for multicast applications. By itself, UDP is not reliable 342 -- messages may be lost or delivered out of order. 344 3.2.1. IPv4 issues 346 The following list contains some representative discovery protocols, 347 which utilize broadcast/multicast, that are used with IPv4. 349 o ARP [RFC5424] 350 o DHCP [RFC2131] 351 o mDNS [RFC6762] 352 o uPnP [RFC6970] 354 After initial configuration, ARP (described in more detail later) and 355 DHCP occur much less commonly, but service discovery can occur at any 356 time. Some widely-deployed service discovery protocols (e.g., for 357 finding a printer) utilize mDNS (i.e., multicast) which is often the 358 first service that operators drop. Even if multicast snooping 359 [RFC4541] (which provides the benefit of conserving bandwidth on 360 those segments of the network where no node has expressed interest in 361 receiving packets addressed to the group address) is utilized, many 362 devices can register at once and cause serious network degradation. 364 3.2.2. IPv6 issues 366 IPv6 makes extensive use of multicast, including the following: 368 o DHCPv6 [RFC8415] 369 o Protocol Independent Multicast (PIM) [RFC7761] 370 o IPv6 Neighbor Discovery Protocol (NDP) [RFC4861] 371 o multicast DNS (mDNS) [RFC6762] 372 o Router Discovery [RFC4286] 374 IPv6 NDP Neighbor Solicitation (NS) messages used in Duplicate 375 Address Detection (DAD) and Address Lookup make use of Link-Scope 376 multicast. In contrast to IPv4, an IPv6 node will typically use 377 multiple addresses, and may change them often for privacy reasons. 378 This intensifies the impact of multicast messages that are associated 379 to the mobility of a node. Router advertisement (RA) messages are 380 also periodically multicasted over the Link. 382 Neighbors may be considered lost if several consecutive Neighbor 383 Discovery packets fail. 385 3.2.3. MLD issues 387 Multicast Listener Discovery (MLD) [RFC4541] is used to identify 388 members of a multicast group that are connected to the ports of a 389 switch. Forwarding multicast frames into a Wi-Fi-enabled area can 390 use such switch support for hardware forwarding state information. 391 However, since IPv6 makes heavy use of multicast, each STA with an 392 IPv6 address will require state on the switch for several and 393 possibly many multicast solicited-node addresses. Multicast 394 addresses that do not have forwarding state installed (perhaps due to 395 hardware memory limitations on the switch) cause frames to be flooded 396 on all ports of the switch. Some switch vendors do not support MLD, 397 for link-scope multicast, due to the increase it can cause in state. 399 3.2.4. Spurious Neighbor Discovery 401 On the Internet there is a "background radiation" of scanning traffic 402 (people scanning for vulnerable machines) and backscatter (responses 403 from spoofed traffic, etc). This means that routers very often 404 receive packets destined for IPv4 addresses regardless of whether 405 those IP addresses are in use. In the cases where the IP is assigned 406 to a host, the router broadcasts an ARP request, gets back an ARP 407 reply, and caches it; then traffic can be delivered to the host. 408 When the IP address is not in use, the router broadcasts one (or 409 more) ARP requests, and never gets a reply. This means that it does 410 not populate the ARP cache, and the next time there is traffic for 411 that IP address the router will rebroadcast the ARP requests. 413 The rate of these ARP requests is proportional to the size of the 414 subnets, the rate of scanning and backscatter, and how long the 415 router keeps state on non-responding ARPs. As it turns out, this 416 rate is inversely proportional to how occupied the subnet is (valid 417 ARPs end up in a cache, stopping the broadcasting; unused IPs never 418 respond, and so cause more broadcasts). Depending on the address 419 space in use, the time of day, how occupied the subnet is, and other 420 unknown factors, thousands of broadcasts per second have been 421 observed. Around 2,000 broadcasts per second have been observed at 422 the IETF NOC during face-to-face meetings. 424 With Neighbor Discovery for IPv6 [RFC4861], nodes accomplish address 425 resolution by multicasting a Neighbor Solicitation that asks the 426 target node to return its link-layer address. Neighbor Solicitation 427 messages are multicast to the solicited-node multicast address of the 428 target address. The target returns its link-layer address in a 429 unicast Neighbor Advertisement message. A single request-response 430 pair of packets is sufficient for both the initiator and the target 431 to resolve each other's link-layer addresses; the initiator includes 432 its link-layer address in the Neighbor Solicitation. 434 On a wired network, there is not a huge difference between unicast, 435 multicast and broadcast traffic. Due to hardware filtering (see, 436 e.g., [Deri-2010]), inadvertently flooded traffic (or excessive 437 ethernet multicast) on wired networks can be quite a bit less costly, 438 compared to wireless cases where sleeping devices have to wake up to 439 process packets. Wired Ethernets tend to be switched networks, 440 further reducing interference from multicast. There is effectively 441 no collision / scheduling problem except at extremely high port 442 utilizations. 444 This is not true in the wireless realm; wireless equipment is often 445 unable to send high volumes of broadcast and multicast traffic, 446 causing numerous broadcast and multicast packets to be dropped. 447 Consequently, when a host connects it is often not able to complete 448 DHCP, and IPv6 RAs get dropped, leading to users being unable to use 449 the network. 451 4. Multicast protocol optimizations 453 This section lists some optimizations that have been specified in 454 IEEE 802 and IETF that are aimed at reducing or eliminating the 455 issues discussed in Section 3. 457 4.1. Proxy ARP in 802.11-2012 459 The AP knows the MAC address and IP address for all associated STAs. 460 In this way, the AP acts as the central "manager" for all the 802.11 461 STAs in its basic service set (BSS). Proxy ARP is easy to implement 462 at the AP, and offers the following advantages: 464 o Reduced broadcast traffic (transmitted at low MCS) on the wireless 465 medium 466 o STA benefits from extended power save in sleep mode, as ARP 467 requests for STA's IP address are handled instead by the AP. 468 o ARP frames are kept off the wireless medium. 469 o No changes are needed to STA implementation. 471 Here is the specification language as described in clause 10.23.13 of 472 [dot11-proxyarp]: 474 When the AP supports Proxy ARP "[...] the AP shall maintain a 475 Hardware Address to Internet Address mapping for each associated 476 station, and shall update the mapping when the Internet Address of 477 the associated station changes. When the IPv4 address being 478 resolved in the ARP request packet is used by a non-AP STA 479 currently associated to the BSS, the proxy ARP service shall 480 respond on behalf of the non-AP STA". 482 4.2. IPv6 Address Registration and Proxy Neighbor Discovery 484 As used in this section, a Low-Power Wireless Personal Area Network 485 (6LoWPAN) denotes a low power lossy network (LLN) that supports 486 6LoWPAN Header Compression (HC) [RFC6282]. A 6TiSCH network 487 [I-D.ietf-6tisch-architecture] is an example of a 6LowPAN. In order 488 to control the use of IPv6 multicast over 6LoWPANs, the 6LoWPAN 489 Neighbor Discovery (6LoWPAN ND) [RFC6775] standard defines an address 490 registration mechanism that relies on a central registry to assess 491 address uniqueness, as a substitute to the inefficient DAD mechanism 492 found in the mainstream IPv6 Neighbor Discovery Protocol (NDP) 493 [RFC4861][RFC4862]. 495 The 6lo Working Group has specified an update [RFC8505] to RFC6775. 496 Wireless devices can register their address to a Backbone Router 497 [I-D.ietf-6lo-backbone-router], which proxies for the registered 498 addresses with the IPv6 NDP running on a high speed aggregating 499 backbone. The update also enables a proxy registration mechanism on 500 behalf of the registered node, e.g. by a 6LoWPAN router to which the 501 mobile node is attached. 503 The general idea behind the backbone router concept is that broadcast 504 and multicast messaging should be tightly controlled in a variety of 505 WLANs and Wireless Personal Area Networks (WPANs). Connectivity to a 506 particular link that provides the subnet should be left to Layer-3. 507 The model for the Backbone Router operation is represented in 508 Figure 1. 510 | 511 +-----+ 512 | | Gateway (default) router 513 | | 514 +-----+ 515 | 516 | Backbone Link 517 +--------------------+------------------+ 518 | | | 519 +-----+ +-----+ +-----+ 520 | | Backbone | | Backbone | | Backbone 521 | | router 1 | | router 2 | | router 3 522 +-----+ +-----+ +-----+ 523 o o o o o o 524 o o o o o o o o o o o o o o 525 o o o o o o o o o o o o o o o 526 o o o o o o o o o o 527 o o o o o o o 529 LLN 1 LLN 2 LLN 3 531 Figure 1: Backbone Link and Backbone Routers 533 LLN nodes can move freely from an LLN anchored at one IPv6 Backbone 534 Router to an LLN anchored at another Backbone Router on the same 535 backbone, keeping any of the IPv6 addresses they have configured. 536 The Backbone Routers maintain a Binding Table of their Registered 537 Nodes, which serves as a distributed database of all the LLN Nodes. 538 An extension to the Neighbor Discovery Protocol is introduced to 539 exchange Binding Table information across the Backbone Link as needed 540 for the operation of IPv6 Neighbor Discovery. 542 RFC6775 and follow-on work [RFC8505] address the needs of LLNs, and 543 similar techniques are likely to be valuable on any type of link 544 where sleeping devices are attached, or where the use of broadcast 545 and multicast operations should be limited. 547 4.3. Buffering to Improve Battery Life 549 Methods have been developed to help save battery life; for example, a 550 device might not wake up when the AP receives a multicast packet. 551 The AP acts on behalf of STAs in various ways. To enable use of the 552 power-saving feature for STAs in its BSS, the AP buffers frames for 553 delivery to the STA at the time when the STA is scheduled for 554 reception. If an AP, for instance, expresses a DTIM (Delivery 555 Traffic Indication Message) of 3 then the AP will send a multicast 556 packet every 3 packets. In fact, when any single wireless STA 557 associated with an access point has 802.11 power-save mode enabled, 558 the access point buffers all multicast frames and sends them only 559 after the next DTIM beacon. 561 In practice, most AP's will send a multicast every 30 packets. For 562 unicast the AP could send a TIM (Traffic Indication Message), but for 563 multicast the AP sends a broadcast to everyone. DTIM does power 564 management but STAs can choose whether or not to wake up and whether 565 or not to drop the packet. Unfortunately, without proper 566 administrative control, such STAs may be unable to determine why 567 their multicast operations do not work. 569 4.4. Limiting multicast buffer hardware queue depth 571 The CAB (Content after Beacon) queue is used for beacon-triggered 572 transmission of buffered multicast frames. If lots of multicast 573 frames were buffered, and this queue fills up, it drowns out all 574 regular traffic. To limit the damage that buffered traffic can do, 575 some drivers limit the amount of queued multicast data to a fraction 576 of the beacon_interval. An example of this is [CAB]. 578 4.5. IPv6 support in 802.11-2012 580 IPv6 uses NDP instead of ARP. Every IPv6 node subscribes to a 581 special multicast address for this purpose. 583 Here is the specification language from clause 10.23.13 of 584 [dot11-proxyarp]: 586 "When an IPv6 address is being resolved, the Proxy Neighbor 587 Discovery service shall respond with a Neighbor Advertisement 588 message [...] on behalf of an associated STA to an [ICMPv6] 589 Neighbor Solicitation message [...]. When MAC address mappings 590 change, the AP may send unsolicited Neighbor Advertisement 591 Messages on behalf of a STA." 593 NDP may be used to request additional information 595 o Maximum Transmission Unit 596 o Router Solicitation 597 o Router Advertisement, etc. 599 NDP messages are sent as group addressed (broadcast) frames in 600 802.11. Using the proxy operation helps to keep NDP messages off the 601 wireless medium. 603 4.6. Using Unicast Instead of Multicast 605 It is often possible to transmit multicast control and data messages 606 by using unicast transmissions to each station individually. 608 4.6.1. Overview 610 In many situations, it's a good choice to use unicast instead of 611 multicast over the Wi-Fi link. This avoids most of the problems 612 specific to multicast over Wi-Fi, since the individual frames are 613 then acknowledged and buffered for power save clients, in the way 614 that unicast traffic normally operates. 616 This approach comes with the tradeoff of sometimes sending the same 617 packet multiple times over the Wi-Fi link. However, in many cases, 618 such as video into a residential home network, this can be a good 619 tradeoff, since the Wi-Fi link may have enough capacity for the 620 unicast traffic to be transmitted to each subscribed STA, even though 621 multicast addressing may have been necessary for the upstream access 622 network. 624 Several technologies exist that can be used to arrange unicast 625 transport over the Wi-Fi link, outlined in the subsections below. 627 4.6.2. Layer 2 Conversion to Unicast 629 It is often possible to transmit multicast control and data messages 630 by using unicast transmissions to each station individually. 632 Although there is not yet a standardized method of conversion, at 633 least one widely available implementation exists in the Linux 634 bridging code [bridge-mc-2-uc]. Other proprietary implementations 635 are available from various vendors. In general, these 636 implementations perform a straightforward mapping for groups or 637 channels, discovered by IGMP or MLD snooping, to the corresponding 638 unicast MAC addresses. 640 4.6.3. Directed Multicast Service (DMS) 642 There are situations where more is needed than simply converting 643 multicast to unicast. For these purposes, DMS enables an STA to 644 request that the AP transmit multicast group addressed frames 645 destined to the requesting STAs as individually addressed frames 646 [i.e., convert multicast to unicast]. Here are some characteristics 647 of DMS: 649 o Requires 802.11n A-MSDUs 650 o Individually addressed frames are acknowledged and are buffered 651 for power save STAs 652 o The requesting STA may specify traffic characteristics for DMS 653 traffic 654 o DMS was defined in IEEE Std 802.11v-2011 655 o DMS requires changes to both AP and STA implementation. 657 DMS is not currently implemented in products. See [Tramarin2017] and 658 [Oliva2013] for more information. 660 4.6.4. Automatic Multicast Tunneling (AMT) 662 AMT[RFC7450] provides a method to tunnel multicast IP packets inside 663 unicast IP packets over network links that only support unicast. 664 When an operating system or application running on an STA has an AMT 665 gateway capability integrated, it's possible to use unicast to 666 traverse the Wi-Fi link by deploying an AMT relay in the non-Wi-Fi 667 portion of the network connected to the AP. 669 It is recommended that multicast-enabled networks deploying AMT 670 relays for this purpose make the relays locally discoverable with the 671 following methods, as described in 672 [I-D.ietf-mboned-driad-amt-discovery]: 674 o DNS-SD [RFC6763] 675 o the well-known IP addresses from Section 7 of [RFC7450] 677 An AMT gateway that implements multiple standard discovery methods is 678 more likely to discover the local multicast-capable network, instead 679 of forming a connection to a non-local AMT relay further upstream. 681 4.7. GroupCast with Retries (GCR) 683 GCR (defined in [dot11aa]) provides greater reliability by using 684 either unsolicited retries or a block acknowledgement mechanism. GCR 685 increases probability of broadcast frame reception success, but still 686 does not guarantee success. 688 For the block acknowledgement mechanism, the AP transmits each group 689 addressed frame as conventional group addressed transmission. 690 Retransmissions are group addressed, but hidden from non-11aa STAs. 691 A directed block acknowledgement scheme is used to harvest reception 692 status from receivers; retransmissions are based upon these 693 responses. 695 GCR is suitable for all group sizes including medium to large groups. 696 As the number of devices in the group increases, GCR can send block 697 acknowledgement requests to only a small subset of the group. GCR 698 does require changes to both AP and STA implementations. 700 GCR may introduce unacceptable latency. After sending a group of 701 data frames to the group, the AP has to do the following: 703 o unicast a Block Ack Request (BAR) to a subset of members. 704 o wait for the corresponding Block Ack (BA). 705 o retransmit any missed frames. 706 o resume other operations that may have been delayed. 708 This latency may not be acceptable for some traffic. 710 There are ongoing extensions in 802.11 to improve GCR performance. 712 o BAR is sent using downlink MU-MIMO (note that downlink MU-MIMO is 713 already specified in 802.11-REVmc 4.3). 714 o BA is sent using uplink MU-MIMO (which is a .11ax feature). 715 o Additional 802.11ax extensions are under consideration; see 716 [mc-ack-mux] 717 o Latency may also be reduced by simultaneously receiving BA 718 information from multiple STAs. 720 5. Operational optimizations 722 This section lists some operational optimizations that can be 723 implemented when deploying wireless IEEE 802 networks to mitigate 724 some of the issues discussed in Section 3. 726 5.1. Mitigating Problems from Spurious Neighbor Discovery 728 ARP Sponges 730 An ARP Sponge sits on a network and learns which IP addresses 731 are actually in use. It also listens for ARP requests, and, if 732 it sees an ARP for an IP address that it believes is not used, 733 it will reply with its own MAC address. This means that the 734 router now has an IP to MAC mapping, which it caches. If that 735 IP is later assigned to a machine (e.g using DHCP), the ARP 736 sponge will see this, and will stop replying for that address. 737 Gratuitous ARPs (or the machine ARPing for its gateway) will 738 replace the sponged address in the router ARP table. This 739 technique is quite effective; but, unfortunately, the ARP 740 sponge daemons were not really designed for this use (one of 741 the most widely deployed arp sponges [arpsponge], was designed 742 to deal with the disappearance of participants from an IXP) and 743 so are not optimized for this purpose. One daemon is needed 744 per subnet, the tuning is tricky (the scanning rate versus the 745 population rate versus retires, etc.) and sometimes daemons 746 just stop, requiring a restart of the daemon which causes 747 disruption. 749 Router mitigations 751 Some routers (often those based on Linux) implement a "negative 752 ARP cache" daemon. Simply put, if the router does not see a 753 reply to an ARP it can be configured to cache this information 754 for some interval. Unfortunately, the core routers in use 755 often do not support this. When a host connects to a network 756 and gets an IP address, it will ARP for its default gateway 757 (the router). The router will update its cache with the IP to 758 host MAC mapping learned from the request (passive ARP 759 learning). 761 Firewall unused space 763 The distribution of users on wireless networks / subnets may 764 change in various use cases, such as conference venues (e.g 765 SSIDs are renamed, some SSIDs lose favor, etc). This makes 766 utilization for particular SSIDs difficult to predict ahead of 767 time, but usage can be monitored as attendees use the different 768 networks. Configuring multiple DHCP pools per subnet, and 769 enabling them sequentially, can create a large subnet, from 770 which only addresses in the lower portions are assigned. 771 Therefore input IP access lists can be applied, which deny 772 traffic to the upper, unused portions. Then the router does 773 not attempt to forward packets to the unused portions of the 774 subnets, and so does not ARP for it. This method has proven to 775 be very effective, but is somewhat of a blunt axe, is fairly 776 labor intensive, and requires coordination. 778 Disabling/filtering ARP requests 780 In general, the router does not need to ARP for hosts; when a 781 host connects, the router can learn the IP to MAC mapping from 782 the ARP request sent by that host. Consequently it should be 783 possible to disable and / or filter ARP requests from the 784 router. Unfortunately, ARP is a very low level / fundamental 785 part of the IP stack, and is often offloaded from the normal 786 control plane. While many routers can filter layer-2 traffic, 787 this is usually implemented as an input filter and / or has 788 limited ability to filter output broadcast traffic. This means 789 that the simple "just disable ARP or filter it outbound" seems 790 like a really simple (and obvious) solution, but 791 implementations / architectural issues make this difficult or 792 awkward in practice. 794 NAT 796 Broadcasts can often be caused by outside wifi scanning / 797 backscatter traffic. In order to reduce the impact of 798 broadcasts, NAT can be used on the entire (or a large portion) 799 of a network. This would eliminate NAT translation entries for 800 unused addresses, and the router would never ARP for them. 801 There are, however, many reasons to avoid using NAT in such a 802 blanket fashion. 804 Stateful firewalls 806 Another obvious solution would be to put a stateful firewall 807 between the wireless network and the Internet. This firewall 808 would block incoming traffic not associated with an outbound 809 request. But this conflicts with the need and desire of some 810 organizations to have the network as open as possible and to 811 honor the end-to-end principle. An attendee on a meeting 812 network should be an Internet host, and should be able to 813 receive unsolicited requests. Unfortunately, keeping the 814 network working and stable is the first priority and a stateful 815 firewall may be required in order to achieve this. 817 5.2. Mitigating Spurious Service Discovery Messages 819 In networks that must support hundreds of STAs, operators have 820 observed network degradation due to many devices simultaneously 821 registering with mDNS. In a network with many clients, it is 822 recommended to ensure that mDNS packets designed to discover 823 services in smaller home networks be constrained to avoid 824 disrupting other traffic. 826 6. Multicast Considerations for Other Wireless Media 828 Many of the causes of performance degradation described in earlier 829 sections are also observable for wireless media other than 802.11. 831 For instance, problems with power save, excess media occupancy, and 832 poor reliability will also affect 802.15.3 and 802.15.4. 833 Unfortunately, 802.15 media specifications do not yet include 834 mechanisms similar to those developed for 802.11. In fact, the 835 design philosophy for 802.15 is oriented towards minimality, with the 836 result that many such functions are relegated to operation within 837 higher layer protocols. This leads to a patchwork of non- 838 interoperable and vendor-specific solutions. See [uli] for some 839 additional discussion, and a proposal for a task group to resolve 840 similar issues, in which the multicast problems might be considered 841 for mitigation. 843 Similar considerations hold for most other wireless media. A brief 844 introduction is provided in [RFC5757] for the following: 846 o 802.16 WIMAX 847 o 3GPP/3GPP2 848 o DVB-H / DVB-IPDC 849 o TV Broadcast and Satellite Networks 851 7. Recommendations 853 This section provides some recommendations about the usage and 854 combinations of some of the multicast enhancements described in 855 Section 4 and Section 5. 857 Future protocol documents utilizing multicast signaling should be 858 carefully scrutinized if the protocol is likely to be used over 859 wireless media. 861 Proxy methods should be encouraged to conserve network bandwidth and 862 power utilization by low-power devices. The device can use a unicast 863 message to its proxy, and then the proxy can take care of any needed 864 multicast operations. 866 Multicast signaling for wireless devices should be done in a way 867 compatible with low duty-cycle operation. 869 8. On-going Discussion Items 871 This section suggests two discussion items for further resolution. 873 First, standards (and private) organizations should develop 874 guidelines to help clarify when multicast packets should be sent 875 wired rather than wireless. For example, 802.1ak [1] works on both 876 ethernet and Wi-Fi and organizations could help decision making by 877 developing guidelines for multicast over Wi-Fi including options for 878 when traffic should be sent wired. 880 Second, reliable registration to Layer-2 multicast groups, and a 881 reliable multicast operation at Layer-2, might provide a good 882 multicast over wifi solution. There shouldn't be a need to support 883 2^24 groups to get solicited node multicast working: it is possible 884 to simply select a number of trailing bits that make sense for a 885 given network size to limit the number of unwanted deliveries to 886 reasonable levels. IEEE 802.1, 802.11, and 802.15 should be 887 encouraged to revisit L2 multicast issues and provide workable 888 solutions. 890 9. Security Considerations 892 This document does not introduce or modify any security mechanisms. 893 Multicast deployed on wired or wireless networks as discussed in this 894 document can be made more secure in a variety of ways. [RFC7761], 895 for instance, specifies the use of IPsec to ensure authentication of 896 the link-local messages in the Protocol Independent Multicast - 897 Sparse Mode (PIM-SM) routing protocol. [RFC5796]specifies mechanisms 898 to authenticate the PIM-SM link-local messages using the IP security 899 (IPsec) Encapsulating Security Payload (ESP) or (optionally) the 900 Authentication Header (AH). 902 As noted in [group_key], the unreliable nature of multicast 903 transmission over wireless media can cause subtle problems with 904 multicast group key management and updates. When WPA (TKIP) or WPA2 905 (AES-CCMP) encryption is in use, AP to client (From DS) multicasts 906 have to be encrypted with a separate encryption key that is known to 907 all of the clients (this is called the Group Key). Quoting further 908 from that website, "... most clients are able to get connected and 909 surf the web, check email, etc. even when From DS multicasts are 910 broken. So a lot of people don't realize they have multicast 911 problems on their network..." 913 This document encourages the use of proxy methods to conserve network 914 bandwidth and power utilization by low-power devices. One such proxy 915 method listed is an Arp Sponge which listens for ARP requests, and, 916 if it sees an ARP for an IP address that it believes is not used, it 917 will reply with its own MAC address. ARP poisoning and false 918 advertising could potentially undermine (e.g. DoS) this, and other, 919 proxy approaches. 921 10. IANA Considerations 923 This document does not request any IANA actions. 925 11. Acknowledgements 927 This document has benefitted from discussions with the following 928 people, in alphabetical order: Mikael Abrahamsson, Bill Atwood, 929 Stuart Cheshire, Donald Eastlake, Toerless Eckert, Jake Holland, Joel 930 Jaeggli, Jan Komissar, David Lamparter, Morten Pedersen, Pascal 931 Thubert, Jeffrey (Zhaohui) Zhang 933 12. References 934 12.1. Informative References 936 [arpsponge] 937 Wessel, M. and N. Sijm, "Effects of IPv4 and IPv6 address 938 resolution on AMS-IX and the ARP Sponge", July 2009, 939 . 942 [bridge-mc-2-uc] 943 Fietkau, F., "bridge: multicast to unicast", Jan 2017, 944 . 947 [CAB] Fietkau, F., "Limit multicast buffer hardware queue 948 depth", 2013, 949 . 951 [Deri-2010] 952 Deri, L. and J. Gasparakis, "10 Gbit Hardware Packet 953 Filtering Using Commodity Network Adapters", RIPE 61, 954 2010, . 957 [dot11] "IEEE 802 Wireless", "802.11-2016 - IEEE Standard for 958 Information technology--Telecommunications and information 959 exchange between systems Local and metropolitan area 960 networks--Specific requirements - Part 11: Wireless LAN 961 Medium Access Control (MAC) and Physical Layer (PHY) 962 Specification (includes 802.11v amendment)", March 2016, 963 . 966 [dot11-proxyarp] 967 Hiertz, G., Mestanov, F., and B. Hart, "Proxy ARP in 968 802.11ax", September 2015, 969 . 972 [dot11aa] "IEEE 802 Wireless", "Part 11: Wireless LAN Medium Access 973 Control (MAC) and Physical Layer (PHY) Specifications 974 Amendment 2: MAC Enhancements for Robust Audio Video 975 Streaming", March 2012, 976 . 978 [group_key] 979 Spiff, "Why do some WiFi routers block multicast packets 980 going from wired to wireless?", Jan 2017, 981 . 985 [I-D.ietf-6lo-backbone-router] 986 Thubert, P., Perkins, C., and E. Levy-Abegnoli, "IPv6 987 Backbone Router", draft-ietf-6lo-backbone-router-20 (work 988 in progress), March 2020. 990 [I-D.ietf-6tisch-architecture] 991 Thubert, P., "An Architecture for IPv6 over the TSCH mode 992 of IEEE 802.15.4", draft-ietf-6tisch-architecture-30 (work 993 in progress), November 2020. 995 [I-D.ietf-mboned-driad-amt-discovery] 996 Holland, J., "DNS Reverse IP AMT (Automatic Multicast 997 Tunneling) Discovery", draft-ietf-mboned-driad-amt- 998 discovery-13 (work in progress), December 2019. 1000 [ietf_802-11] 1001 Stanley, D., "IEEE 802.11 multicast capabilities", Nov 1002 2015, . 1006 [mc-ack-mux] 1007 Tanaka, Y., Sakai, E., Morioka, Y., Mori, M., Hiertz, G., 1008 and S. Coffey, "Multiplexing of Acknowledgements for 1009 Multicast Transmission", July 2015, 1010 . 1014 [mc-prob-stmt] 1015 Abrahamsson, M. and A. Stephens, "Multicast on 802.11", 1016 March 2015, . 1019 [mc-props] 1020 Stephens, A., "IEEE 802.11 multicast properties", March 1021 2015, . 1025 [Oliva2013] 1026 de la Oliva, A., Serrano, P., Salvador, P., and A. Banchs, 1027 "Performance evaluation of the IEEE 802.11aa multicast 1028 mechanisms for video streaming", 2013 IEEE 14th 1029 International Symposium on "A World of Wireless, Mobile 1030 and Multimedia Networks" (WoWMoM) pp. 1-9, June 2013. 1032 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 1033 RFC 2131, DOI 10.17487/RFC2131, March 1997, 1034 . 1036 [RFC4286] Haberman, B. and J. Martin, "Multicast Router Discovery", 1037 RFC 4286, DOI 10.17487/RFC4286, December 2005, 1038 . 1040 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 1041 "Considerations for Internet Group Management Protocol 1042 (IGMP) and Multicast Listener Discovery (MLD) Snooping 1043 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 1044 . 1046 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1047 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1048 DOI 10.17487/RFC4861, September 2007, 1049 . 1051 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1052 Address Autoconfiguration", RFC 4862, 1053 DOI 10.17487/RFC4862, September 2007, 1054 . 1056 [RFC5424] Gerhards, R., "The Syslog Protocol", RFC 5424, 1057 DOI 10.17487/RFC5424, March 2009, 1058 . 1060 [RFC5757] Schmidt, T., Waehlisch, M., and G. Fairhurst, "Multicast 1061 Mobility in Mobile IP Version 6 (MIPv6): Problem Statement 1062 and Brief Survey", RFC 5757, DOI 10.17487/RFC5757, 1063 February 2010, . 1065 [RFC5796] Atwood, W., Islam, S., and M. Siami, "Authentication and 1066 Confidentiality in Protocol Independent Multicast Sparse 1067 Mode (PIM-SM) Link-Local Messages", RFC 5796, 1068 DOI 10.17487/RFC5796, March 2010, 1069 . 1071 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 1072 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 1073 DOI 10.17487/RFC6282, September 2011, 1074 . 1076 [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, 1077 DOI 10.17487/RFC6762, February 2013, 1078 . 1080 [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service 1081 Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013, 1082 . 1084 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 1085 Bormann, "Neighbor Discovery Optimization for IPv6 over 1086 Low-Power Wireless Personal Area Networks (6LoWPANs)", 1087 RFC 6775, DOI 10.17487/RFC6775, November 2012, 1088 . 1090 [RFC6970] Boucadair, M., Penno, R., and D. Wing, "Universal Plug and 1091 Play (UPnP) Internet Gateway Device - Port Control 1092 Protocol Interworking Function (IGD-PCP IWF)", RFC 6970, 1093 DOI 10.17487/RFC6970, July 2013, 1094 . 1096 [RFC7450] Bumgardner, G., "Automatic Multicast Tunneling", RFC 7450, 1097 DOI 10.17487/RFC7450, February 2015, 1098 . 1100 [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I., 1101 Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent 1102 Multicast - Sparse Mode (PIM-SM): Protocol Specification 1103 (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March 1104 2016, . 1106 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 1107 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 1108 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 1109 RFC 8415, DOI 10.17487/RFC8415, November 2018, 1110 . 1112 [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. 1113 Perkins, "Registration Extensions for IPv6 over Low-Power 1114 Wireless Personal Area Network (6LoWPAN) Neighbor 1115 Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, 1116 . 1118 [Tramarin2017] 1119 Tramarin, F., Vitturi, S., and M. Luvisotto, "IEEE 802.11n 1120 for Distributed Measurement Systems", 2017 IEEE 1121 International Instrumentation and Measurement Technology 1122 Conference (I2MTC) pp. 1-6, May 2017. 1124 [uli] Kinney, P., "LLC Proposal for 802.15.4", Nov 2015, 1125 . 1128 12.2. URIs 1130 [1] https://www.ieee802.org/1/pages/802.1ak.html 1132 Authors' Addresses 1134 Charles E. Perkins 1135 Blue Meadow Networks 1137 Phone: +1-408-330-4586 1138 Email: charliep@computer.org 1140 Mike McBride 1141 Futurewei Technologies Inc. 1142 2330 Central Expressway 1143 Santa Clara, CA 95055 1144 USA 1146 Email: michael.mcbride@futurewei.com 1148 Dorothy Stanley 1149 Hewlett Packard Enterprise 1150 2000 North Naperville Rd. 1151 Naperville, IL 60566 1152 USA 1154 Phone: +1 630 979 1572 1155 Email: dstanley1389@gmail.com 1156 Warren Kumari 1157 Google 1158 1600 Amphitheatre Parkway 1159 Mountain View, CA 94043 1160 USA 1162 Email: warren@kumari.net 1164 Juan Carlos Zuniga 1165 SIGFOX 1166 425 rue Jean Rostand 1167 Labege 31670 1168 France 1170 Email: j.c.zuniga@ieee.org