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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Area C. Perkins 3 Internet-Draft 4 Intended status: Informational M. McBride 5 Expires: May 7, 2020 Futurewei 6 D. Stanley 7 HPE 8 W. Kumari 9 Google 10 JC. Zuniga 11 SIGFOX 12 November 4, 2019 14 Multicast Considerations over IEEE 802 Wireless Media 15 draft-ietf-mboned-ieee802-mcast-problems-10 17 Abstract 19 Well-known issues with multicast have prevented the deployment of 20 multicast in 802.11 and other local-area wireless environments. This 21 document offers guidance on known limitations and problems with 22 wireless (primarily 802.11) Layer-2 multicast. Also described are 23 certain multicast enhancement features that have been specified by 24 the IETF and by IEEE 802 for wireless media, as well as some 25 operational choices that can be taken to improve the performance of 26 the network. Finally, some recommendations are provided about the 27 usage and combination of these features and operational choices. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at https://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on May 7, 2020. 46 Copyright Notice 48 Copyright (c) 2019 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (https://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 65 3. Identified multicast issues . . . . . . . . . . . . . . . . . 5 66 3.1. Issues at Layer 2 and Below . . . . . . . . . . . . . . . 5 67 3.1.1. Multicast reliability . . . . . . . . . . . . . . . . 5 68 3.1.2. Lower and Variable Data Rate . . . . . . . . . . . . 6 69 3.1.3. Capacity and Impact on Interference . . . . . . . . . 7 70 3.1.4. Power-save Effects on Multicast . . . . . . . . . . . 7 71 3.2. Issues at Layer 3 and Above . . . . . . . . . . . . . . . 7 72 3.2.1. IPv4 issues . . . . . . . . . . . . . . . . . . . . . 8 73 3.2.2. IPv6 issues . . . . . . . . . . . . . . . . . . . . . 8 74 3.2.3. MLD issues . . . . . . . . . . . . . . . . . . . . . 9 75 3.2.4. Spurious Neighbor Discovery . . . . . . . . . . . . . 9 76 4. Multicast protocol optimizations . . . . . . . . . . . . . . 10 77 4.1. Proxy ARP in 802.11-2012 . . . . . . . . . . . . . . . . 10 78 4.2. IPv6 Address Registration and Proxy Neighbor Discovery . 11 79 4.3. Buffering to Improve Battery Life . . . . . . . . . . . . 12 80 4.4. Limiting multicast buffer hardware queue depth . . . . . 13 81 4.5. IPv6 support in 802.11-2012 . . . . . . . . . . . . . . . 13 82 4.6. Using Unicast Instead of Multicast . . . . . . . . . . . 14 83 4.6.1. Overview . . . . . . . . . . . . . . . . . . . . . . 14 84 4.6.2. Layer 2 Conversion to Unicast . . . . . . . . . . . . 14 85 4.6.3. Directed Multicast Service (DMS) . . . . . . . . . . 14 86 4.6.4. Automatic Multicast Tunneling (AMT) . . . . . . . . . 15 87 4.7. GroupCast with Retries (GCR) . . . . . . . . . . . . . . 15 88 5. Operational optimizations . . . . . . . . . . . . . . . . . . 16 89 5.1. Mitigating Problems from Spurious Neighbor Discovery . . 16 90 5.2. Mitigating Spurious Service Discovery Messages . . . . . 18 91 6. Multicast Considerations for Other Wireless Media . . . . . . 18 92 7. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 19 93 8. Discussion Items . . . . . . . . . . . . . . . . . . . . . . 19 94 9. Security Considerations . . . . . . . . . . . . . . . . . . . 20 95 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 96 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 97 12. Informative References . . . . . . . . . . . . . . . . . . . 20 98 Appendix A. Changes in this draft between revisions 06 versus 07 24 99 Appendix B. Changes in this draft between revisions 05 versus 06 24 100 Appendix C. Changes in this draft between revisions 04 versus 05 25 101 Appendix D. Changes in this draft between revisions 03 versus 04 25 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 104 1. Introduction 106 Well-known issues with multicast have prevented the deployment of 107 multicast in 802.11 [dot11] and other local-area wireless 108 environments, as described in [mc-props], [mc-prob-stmt]. 109 Performance issues have been observed when multicast packet 110 transmissions of IETF protocols are used over IEEE 802 wireless 111 media. Even though enhancements for multicast transmissions have 112 been designed at both IETF and IEEE 802, incompatibilities still 113 exist between specifications, implementations and configuration 114 choices. 116 Many IETF protocols depend on multicast/broadcast for delivery of 117 control messages to multiple receivers. Multicast allows sending 118 data to multiple interested recipients without the source needing to 119 send duplicate data to each recipient. With broadcast traffic, data 120 is sent to every device regardless of their interest in the data. 121 Multicast is used for various purposes such as neighbor discovery, 122 network flooding, address resolution, as well minimizing media 123 occupancy for the transmission of data that is intended for multiple 124 receivers. In addition to protocol use of broadcast/multicast for 125 control messages, more applications, such as push to talk in 126 hospitals, or video in enterprises, universities, and homes, are 127 sending multicast IP to end user devices, which are increasingly 128 using Wi-Fi for their connectivity. 130 IETF protocols typically rely on network protocol layering in order 131 to reduce or eliminate any dependence of higher level protocols on 132 the specific nature of the MAC layer protocols or the physical media. 133 In the case of multicast transmissions, higher level protocols have 134 traditionally been designed as if transmitting a packet to an IP 135 address had the same cost in interference and network media access, 136 regardless of whether the destination IP address is a unicast address 137 or a multicast or broadcast address. This model was reasonable for 138 networks where the physical medium was wired, like Ethernet. 139 Unfortunately, for many wireless media, the costs to access the 140 medium can be quite different. Multicast over Wi-Fi has often been 141 plagued by such poor performance that it is disallowed. Some 142 enhancements have been designed in IETF protocols that are assumed to 143 work primarily over wireless media. However, these enhancements are 144 usually implemented in limited deployments and not widespread on most 145 wireless networks. 147 IEEE 802 wireless protocols have been designed with certain features 148 to support multicast traffic. For instance, lower modulations are 149 used to transmit multicast frames, so that these can be received by 150 all stations in the cell, regardless of the distance or path 151 attenuation from the base station or access point. However, these 152 lower modulation transmissions occupy the medium longer; they hamper 153 efficient transmission of traffic using higher order modulations to 154 nearby stations. For these and other reasons, IEEE 802 working 155 groups such as 802.11 have designed features to improve the 156 performance of multicast transmissions at Layer 2 [ietf_802-11]. In 157 addition to protocol design features, certain operational and 158 configuration enhancements can ameliorate the network performance 159 issues created by multicast traffic, as described in Section 5. 161 There seems to be general agreement that these problems will not be 162 fixed anytime soon, primarily because it's expensive to do so and due 163 to multicast being unreliable. Compared to unicast over Wi-Fi, 164 multicast is often treated as somewhat of a second class citizen, 165 even though there are many protocols using multicast. Something 166 needs to be provided in order to make them more reliable. IPv6 167 neighbor discovery saturating the Wi-Fi link is only part of the 168 problem. Wi-Fi traffic classes may help. This document is intended 169 to help make the determination about what problems should be solved 170 by the IETF and what problems should be solved by the IEEE (see 171 Section 8). 173 This document details various problems caused by multicast 174 transmission over wireless networks, including high packet error 175 rates, no acknowledgements, and low data rate. It also explains some 176 enhancements that have been designed at the IETF and IEEE 802.11 to 177 ameliorate the effects of multicast traffic. Recommendations are 178 also provided to implementors about how to use and combine these 179 enhancements. Some advice about the operational choices that can be 180 taken is also included. It is likely that this document will also be 181 considered relevant to designers of future IEEE wireless 182 specifications. 184 2. Terminology 186 This document uses the following definitions: 188 ACK 189 The 802.11 layer 2 acknowledgement 191 AP 192 IEEE 802.11 Access Point 194 basic rate 195 The slowest rate of all the connected devices, at which multicast 196 and broadcast traffic is generally transmitted 198 DTIM 199 Delivery Traffic Indication Map (DTIM): An information element 200 that advertises whether or not any associated stations have 201 buffered multicast or broadcast frames 203 MCS 204 Modulation and Coding Scheme 206 NOC 207 Network Operations Center 209 PER 210 Packet Error Rate 212 STA 213 802.11 station (e.g. handheld device) 215 TIM 216 Traffic Indication Map (TIM): An information element that 217 advertises whether or not any associated stations have buffered 218 unicast frames 220 3. Identified multicast issues 222 3.1. Issues at Layer 2 and Below 224 In this section some of the issues related to the use of multicast 225 transmissions over IEEE 802 wireless technologies are described. 227 3.1.1. Multicast reliability 229 Multicast traffic is typically much less reliable than unicast 230 traffic. Since multicast makes point-to-multipoint communications, 231 multiple acknowledgements would be needed to guarantee reception at 232 all recipients. Since there are no ACKs for multicast packets, it is 233 not possible for the Access Point (AP) to know whether or not a 234 retransmission is needed. Even in the wired Internet, this 235 characteristic often causes undesirably high error rates. This has 236 contributed to the relatively slow uptake of multicast applications 237 even though the protocols have long been available. The situation 238 for wireless links is much worse, and is quite sensitive to the 239 presence of background traffic. Consequently, there can be a high 240 packet error rate (PER) due to lack of retransmission, and because 241 the sender never backs off. It is not uncommon for there to be a 242 packet loss rate of 5% or more, which is particularly troublesome for 243 video and other environments where high data rates and high 244 reliability are required. 246 3.1.2. Lower and Variable Data Rate 248 Multicast over wired differs from multicast over wireless because 249 transmission over wired links often occurs at a fixed rate. Wi-Fi, 250 on the other hand, has a transmission rate that varies depending upon 251 the STA's proximity to the AP. The throughput of video flows, and 252 the capacity of the broader Wi-Fi network, will change and will 253 impact the ability for QoS solutions to effectively reserve bandwidth 254 and provide admission control. 256 For wireless stations associated with an Access Point, the power 257 necessary for good reception can vary from station to station. For 258 unicast, the goal is to minimize power requirements while maximizing 259 the data rate to the destination. For multicast, the goal is simply 260 to maximize the number of receivers that will correctly receive the 261 multicast packet; generally the Access Point has to use a much lower 262 data rate at a power level high enough for even the farthest station 263 to receive the packet, for example as briefly mentioned in section 2 264 of [RFC5757]. Consequently, the data rate of a video stream, for 265 instance, would be constrained by the environmental considerations of 266 the least reliable receiver associated with the Access Point. 268 Because more robust modulation and coding schemes (MCSs) have longer 269 range but also lower data rate, multicast / broadcast traffic is 270 generally transmitted at the slowest rate of all the connected 271 devices. This is also known as the basic rate. The amount of 272 additional interference depends on the specific wireless technology. 273 In fact, backward compatibility and multi-stream implementations mean 274 that the maximum unicast rates are currently up to a few Gbps, so 275 there can be more than 3 orders of magnitude difference in the 276 transmission rate between multicast / broadcast versus optimal 277 unicast forwarding. Some techiques employed to increase spectral 278 efficiency, such as spatial multiplexing in MIMO systems, are not 279 available with more than one intended receiver; it is not the case 280 that backwards compatibility is the only factor responsible for lower 281 multicast transmission rates. 283 Wired multicast also affects wireless LANs when the AP extends the 284 wired segment; in that case, multicast / broadcast frames on the 285 wired LAN side are copied to the Wireless Local Area Network (WLAN). 287 Since broadcast messages are transmitted at the most robust MCS, many 288 large frames are sent at a slow rate over the air. 290 3.1.3. Capacity and Impact on Interference 292 Transmissions at a lower rate require longer occupancy of the 293 wireless medium and thus take away from the airtime of other 294 communications and degrade the overall capacity. Furthermore, 295 transmission at higher power, as is required to reach all multicast 296 STAs associated to the AP, proportionately increases the area of 297 interference. 299 3.1.4. Power-save Effects on Multicast 301 One of the characteristics of multicast transmission is that every 302 station has to be configured to wake up to receive the multicast, 303 even though the received packet may ultimately be discarded. This 304 process can have a large effect on the power consumption by the 305 multicast receiver station. 307 Multicast can work poorly with the power-save mechanisms defined in 308 IEEE 802.11e, for the following reasons. 310 o Clients may be unable to stay in sleep mode due to multicast 311 control packets frequently waking them up. 312 o Both unicast and multicast traffic can be delayed by power-saving 313 mechanisms. 314 o A unicast packet is delayed until an STA wakes up and requests it. 315 Unicast traffic may also be delayed to improve power save, 316 efficiency and increase probability of aggregation. 317 o Multicast traffic is delayed in a wireless network if any of the 318 STAs in that network are power savers. All STAs associated to the 319 AP have to be awake at a known time to receive multicast traffic. 320 o Packets can also be discarded due to buffer limitations in the AP 321 and non-AP STA. 323 3.2. Issues at Layer 3 and Above 325 This section identifies some representative IETF protocols, and 326 describes possible negative effects due to performance degradation 327 when using multicast transmissions for control messages. Common uses 328 of multicast include: 330 o Control plane signaling 331 o Neighbor Discovery 332 o Address Resolution 333 o Service Discovery 334 o Applications (video delivery, stock data, etc.) 335 o On-demand routing 336 o Backbone construction 337 o Other L3 protocols (non-IP) 339 User Datagram Protocol (UDP) is the most common transport layer 340 protocol for multicast applications. By itself, UDP is not reliable 341 -- messages may be lost or delivered out of order. 343 3.2.1. IPv4 issues 345 The following list contains some representative discovery protocols 346 that are used with IPv4. 348 o ARP 349 o DHCP 350 o mDNS [RFC6762] 351 o uPnP [RFC6970] 353 After initial configuration, ARP and DHCP occur much less commonly, 354 but service discovery can occur at any time. Some widely-deployed 355 service discovery protocols (e.g., for finding a printer) utilize 356 mDNS (i.e., multicast). It's often the first service that operators 357 drop. Even if multicast snooping is utilized, many devices can 358 register at once and cause serious network degradation. 360 3.2.2. IPv6 issues 362 IPv6 makes extensive use of multicast, including the following: 364 o DHCPv6 365 o Protocol Independent Multicast (PIM) 366 o IPv6 Neighbor Discovery Protocol (NDP) [RFC4861] 367 o multicast DNS (mDNS) 368 o Route Discovery 369 o Decentralized Address Assignment 370 o Geographic routing 372 IPv6 NDP Neighbor Solicitation (NS) messages used in Duplicate 373 Address Detection (DAD) and Address Lookup make use of Link-Scope 374 multicast. In contrast to IPv4, an IPv6 node will typically use 375 multiple addresses, and may change them often for privacy reasons. 376 This intensifies the impact of multicast messages that are associated 377 to the mobility of a node. Router advertisement (RA) messages are 378 also periodically multicasted over the Link. 380 Neighbors may be considered lost if several consecutive Neighbor 381 Discovery packets fail. 383 3.2.3. MLD issues 385 Multicast Listener Discovery (MLD) [RFC4541] is used to identify 386 members of a multicast group that are connected to the ports of a 387 switch. Forwarding multicast frames into a Wi-Fi-enabled area can 388 use such switch support for hardware forwarding state information. 389 However, since IPv6 makes heavy use of multicast, each STA with an 390 IPv6 address will require state on the switch for several and 391 possibly many multicast solicited-node addresses. Multicast 392 addresses that do not have forwarding state installed (perhaps due to 393 hardware memory limitations on the switch) cause frames to be flooded 394 on all ports of the switch. Some switch vendors do not support MLD, 395 for link-scope multicast, due to the increase it can cause in state. 397 3.2.4. Spurious Neighbor Discovery 399 On the Internet there is a "background radiation" of scanning traffic 400 (people scanning for vulnerable machines) and backscatter (responses 401 from spoofed traffic, etc). This means that routers very often 402 receive packets destined for IP addresses regardless of whether those 403 IP addresses are in use. In the cases where the IP is assigned to a 404 host, the router broadcasts an ARP request, gets back an ARP reply, 405 and caches it; then traffic can be delivered to the host. When the 406 IP address is not in use, the router broadcasts one (or more) ARP 407 requests, and never gets a reply. This means that it does not 408 populate the ARP cache, and the next time there is traffic for that 409 IP address the router will rebroadcast the ARP requests. 411 The rate of these ARP requests is proportional to the size of the 412 subnets, the rate of scanning and backscatter, and how long the 413 router keeps state on non-responding ARPs. As it turns out, this 414 rate is inversely proportional to how occupied the subnet is (valid 415 ARPs end up in a cache, stopping the broadcasting; unused IPs never 416 respond, and so cause more broadcasts). Depending on the address 417 space in use, the time of day, how occupied the subnet is, and other 418 unknown factors, thousands of broadcasts per second have been 419 observed. Around 2,000 broadcasts per second have been observed at 420 the IETF NOC during face-to-face meetings. 422 With Neighbor Discovery for IPv6 [RFC2461], nodes accomplish address 423 resolution by multicasting a Neighbor Solicitation that asks the 424 target node to return its link-layer address. Neighbor Solicitation 425 messages are multicast to the solicited-node multicast address of the 426 target address. The target returns its link-layer address in a 427 unicast Neighbor Advertisement message. A single request-response 428 pair of packets is sufficient for both the initiator and the target 429 to resolve each other's link-layer addresses; the initiator includes 430 its link-layer address in the Neighbor Solicitation. 432 On a wired network, there is not a huge difference between unicast, 433 multicast and broadcast traffic. Due to hardware filtering (see, 434 e.g., [Deri-2010]), inadvertently flooded traffic (or excessive 435 ethernet multicast) on wired networks can be quite a bit less costly, 436 compared to wireless cases where sleeping devices have to wake up to 437 process packets. Wired Ethernets tend to be switched networks, 438 further reducing interference from multicast. There is effectively 439 no collision / scheduling problem except at extremely high port 440 utilizations. 442 This is not true in the wireless realm; wireless equipment is often 443 unable to send high volumes of broadcast and multicast traffic, 444 causing numerous broadcast and multicast packets to be dropped. 445 Consequently, when a host connects it is often not able to complete 446 DHCP, and IPv6 RAs get dropped, leading to users being unable to use 447 the network. 449 4. Multicast protocol optimizations 451 This section lists some optimizations that have been specified in 452 IEEE 802 and IETF that are aimed at reducing or eliminating the 453 issues discussed in Section 3. 455 4.1. Proxy ARP in 802.11-2012 457 The AP knows the MAC address and IP address for all associated STAs. 458 In this way, the AP acts as the central "manager" for all the 802.11 459 STAs in its basic service set (BSS). Proxy ARP is easy to implement 460 at the AP, and offers the following advantages: 462 o Reduced broadcast traffic (transmitted at low MCS) on the wireless 463 medium 464 o STA benefits from extended power save in sleep mode, as ARP 465 requests for STA's IP address are handled instead by the AP. 466 o ARP frames are kept off the wireless medium. 467 o No changes are needed to STA implementation. 469 Here is the specification language as described in clause 10.23.13 of 470 [dot11-proxyarp]: 472 When the AP supports Proxy ARP "[...] the AP shall maintain a 473 Hardware Address to Internet Address mapping for each associated 474 station, and shall update the mapping when the Internet Address of 475 the associated station changes. When the IPv4 address being 476 resolved in the ARP request packet is used by a non-AP STA 477 currently associated to the BSS, the proxy ARP service shall 478 respond on behalf of the non-AP STA". 480 4.2. IPv6 Address Registration and Proxy Neighbor Discovery 482 As used in this section, a Low-Power Wireless Personal Area Network 483 (6LoWPAN) denotes a low power lossy network (LLN) that supports 484 6LoWPAN Header Compression (HC) [RFC6282]. A 6TiSCH network 485 [I-D.ietf-6tisch-architecture] is an example of a 6LowPAN. In order 486 to control the use of IPv6 multicast over 6LoWPANs, the 6LoWPAN 487 Neighbor Discovery (6LoWPAN ND) [RFC6775] standard defines an address 488 registration mechanism that relies on a central registry to assess 489 address uniqueness, as a substitute to the inefficient DAD mechanism 490 found in the mainstream IPv6 Neighbor Discovery Protocol (NDP) 491 [RFC4861][RFC4862]. 493 The 6lo Working Group has specified an update [RFC8505] to RFC6775. 494 Wireless devices can register their address to a Backbone Router 495 [I-D.ietf-6lo-backbone-router], which proxies for the registered 496 addresses with the IPv6 NDP running on a high speed aggregating 497 backbone. The update also enables a proxy registration mechanism on 498 behalf of the registered node, e.g. by a 6LoWPAN router to which the 499 mobile node is attached. 501 The general idea behind the backbone router concept is that broadcast 502 and multicast messaging should be tightly controlled in a variety of 503 WLANs and Wireless Personal Area Networks (WPANs). Connectivity to a 504 particular link that provides the subnet should be left to Layer-3. 505 The model for the Backbone Router operation is represented in 506 Figure 1. 508 | 509 +-----+ 510 | | Gateway (default) router 511 | | 512 +-----+ 513 | 514 | Backbone Link 515 +--------------------+------------------+ 516 | | | 517 +-----+ +-----+ +-----+ 518 | | Backbone | | Backbone | | Backbone 519 | | router 1 | | router 2 | | router 3 520 +-----+ +-----+ +-----+ 521 o o o o o o 522 o o o o o o o o o o o o o o 523 o o o o o o o o o o o o o o o 524 o o o o o o o o o o 525 o o o o o o o 527 LLN 1 LLN 2 LLN 3 529 Figure 1: Backbone Link and Backbone Routers 531 LLN nodes can move freely from an LLN anchored at one IPv6 Backbone 532 Router to an LLN anchored at another Backbone Router on the same 533 backbone, keeping any of the IPv6 addresses they have configured. 534 The Backbone Routers maintain a Binding Table of their Registered 535 Nodes, which serves as a distributed database of all the LLN Nodes. 536 An extension to the Neighbor Discovery Protocol is introduced to 537 exchange Binding Table information across the Backbone Link as needed 538 for the operation of IPv6 Neighbor Discovery. 540 RFC6775 and follow-on work [RFC8505] address the needs of LLNs, and 541 similar techniques are likely to be valuable on any type of link 542 where sleeping devices are attached, or where the use of broadcast 543 and multicast operations should be limited. 545 4.3. Buffering to Improve Battery Life 547 Methods have been developed to help save battery life; for example, a 548 device might not wake up when the AP receives a multicast packet. 549 The AP acts on behalf of STAs in various ways. To enable use of the 550 power-saving feature for STAs in its BSS, the AP buffers frames for 551 delivery to the STA at the time when the STA is scheduled for 552 reception. If an AP, for instance, expresses a DTIM (Delivery 553 Traffic Indication Message) of 3 then the AP will send a multicast 554 packet every 3 packets. In fact, when any single wireless STA 555 associated with an access point has 802.11 power-save mode enabled, 556 the access point buffers all multicast frames and sends them only 557 after the next DTIM beacon. 559 In practice, most AP's will send a multicast every 30 packets. For 560 unicast the AP could send a TIM (Traffic Indication Message), but for 561 multicast the AP sends a broadcast to everyone. DTIM does power 562 management but STAs can choose whether or not to wake up and whether 563 or not to drop the packet. Unfortunately, without proper 564 administrative control, such STAs may be unable to determine why 565 their multicast operations do not work. 567 4.4. Limiting multicast buffer hardware queue depth 569 The CAB (Content after Beacon) queue is used for beacon-triggered 570 transmission of buffered multicast frames. If lots of multicast 571 frames were buffered, and this queue fills up, it drowns out all 572 regular traffic. To limit the damage that buffered traffic can do, 573 some drivers limit the amount of queued multicast data to a fraction 574 of the beacon_interval. An example of this is [CAB]. 576 4.5. IPv6 support in 802.11-2012 578 IPv6 uses NDP instead of ARP. Every IPv6 node subscribes to a 579 special multicast address for this purpose. 581 Here is the specification language from clause 10.23.13 of 582 [dot11-proxyarp]: 584 "When an IPv6 address is being resolved, the Proxy Neighbor 585 Discovery service shall respond with a Neighbor Advertisement 586 message [...] on behalf of an associated STA to an [ICMPv6] 587 Neighbor Solicitation message [...]. When MAC address mappings 588 change, the AP may send unsolicited Neighbor Advertisement 589 Messages on behalf of a STA." 591 NDP may be used to request additional information 593 o Maximum Transmission Unit 594 o Router Solicitation 595 o Router Advertisement, etc. 597 NDP messages are sent as group addressed (broadcast) frames in 598 802.11. Using the proxy operation helps to keep NDP messages off the 599 wireless medium. 601 4.6. Using Unicast Instead of Multicast 603 It is often possible to transmit multicast control and data messages 604 by using unicast transmissions to each station individually. 606 4.6.1. Overview 608 In many situations, it's a good choice to use unicast instead of 609 multicast over the Wi-Fi link. This avoids most of the problems 610 specific to multicast over Wi-Fi, since the individual frames are 611 then acknowledged and buffered for power save clients, in the way 612 that unicast traffic normally operates. 614 This approach comes with the tradeoff of sometimes sending the same 615 packet multiple times over the Wi-Fi link. However, in many cases, 616 such as video into a residential home network, this can be a good 617 tradeoff, since the Wi-Fi link may have enough capacity for the 618 unicast traffic to be transmitted to each subscribed STA, even though 619 multicast addressing may have been necessary for the upstream access 620 network. 622 Several technologies exist that can be used to arrange unicast 623 transport over the Wi-Fi link, outlined in the subsections below. 625 4.6.2. Layer 2 Conversion to Unicast 627 It is often possible to transmit multicast control and data messages 628 by using unicast transmissions to each station individually. 630 Although there is not yet a standardized method of conversion, at 631 least one widely available implementation exists in the Linux 632 bridging code [bridge-mc-2-uc]. Other proprietary implementations 633 are available from various vendors. In general, these 634 implementations perform a straightforward mapping for groups or 635 channels, discovered by IGMP or MLD snooping, to the corresponding 636 unicast MAC addresses. 638 4.6.3. Directed Multicast Service (DMS) 640 There are situations where more is needed than simply converting 641 multicast to unicast. For these purposes, DMS enables an STA to 642 request that the AP transmit multicast group addressed frames 643 destined to the requesting STAs as individually addressed frames 644 [i.e., convert multicast to unicast]. Here are some characteristics 645 of DMS: 647 o Requires 802.11n A-MSDUs 648 o Individually addressed frames are acknowledged and are buffered 649 for power save STAs 650 o The requesting STA may specify traffic characteristics for DMS 651 traffic 652 o DMS was defined in IEEE Std 802.11v-2011 653 o DMS requires changes to both AP and STA implementation. 655 DMS is not currently implemented in products. See [Tramarin2017] and 656 [Oliva2013] for more information. 658 4.6.4. Automatic Multicast Tunneling (AMT) 660 AMT[RFC7450] provides a method to tunnel multicast IP packets inside 661 unicast IP packets over network links that only support unicast. 662 When an operating system or application running on an STA has an AMT 663 gateway capability integrated, it's possible to use unicast to 664 traverse the Wi-Fi link by deploying an AMT relay in the non-Wi-Fi 665 portion of the network connected to the AP. 667 It is recommended that multicast-enabled networks deploying AMT 668 relays for this purpose make the relays locally discoverable with the 669 following methods, as described in 670 [I-D.ietf-mboned-driad-amt-discovery]: 672 o DNS-SD [RFC6763] 673 o the well-known IP addresses from Section 7 of [RFC7450] 675 An AMT gateway that implements multiple standard discovery methods is 676 more likely to discover the local multicast-capable network, instead 677 of forming a connection to a non-local AMT relay further upstream. 679 4.7. GroupCast with Retries (GCR) 681 GCR (defined in [dot11aa]) provides greater reliability by using 682 either unsolicited retries or a block acknowledgement mechanism. GCR 683 increases probability of broadcast frame reception success, but still 684 does not guarantee success. 686 For the block acknowledgement mechanism, the AP transmits each group 687 addressed frame as conventional group addressed transmission. 688 Retransmissions are group addressed, but hidden from non-11aa STAs. 689 A directed block acknowledgement scheme is used to harvest reception 690 status from receivers; retransmissions are based upon these 691 responses. 693 GCR is suitable for all group sizes including medium to large groups. 694 As the number of devices in the group increases, GCR can send block 695 acknowledgement requests to only a small subset of the group. GCR 696 does require changes to both AP and STA implementations. 698 GCR may introduce unacceptable latency. After sending a group of 699 data frames to the group, the AP has do the following: 701 o unicast a Block Ack Request (BAR) to a subset of members. 702 o wait for the corresponding Block Ack (BA). 703 o retransmit any missed frames. 704 o resume other operations that may have been delayed. 706 This latency may not be acceptable for some traffic. 708 There are ongoing extensions in 802.11 to improve GCR performance. 710 o BAR is sent using downlink MU-MIMO (note that downlink MU-MIMO is 711 already specified in 802.11-REVmc 4.3). 712 o BA is sent using uplink MU-MIMO (which is a .11ax feature). 713 o Additional 802.11ax extensions are under consideration; see 714 [mc-ack-mux] 715 o Latency may also be reduced by simultaneously receiving BA 716 information from multiple STAs. 718 5. Operational optimizations 720 This section lists some operational optimizations that can be 721 implemented when deploying wireless IEEE 802 networks to mitigate the 722 issues discussed in Section 3. 724 5.1. Mitigating Problems from Spurious Neighbor Discovery 726 ARP Sponges 728 An ARP Sponge sits on a network and learn which IP addresses 729 are actually in use. It also listen for ARP requests, and, if 730 it sees an ARP for an IP address that it believes is not used, 731 it will reply with its own MAC address. This means that the 732 router now has an IP to MAC mapping, which it caches. If that 733 IP is later assigned to an machine (e.g using DHCP), the ARP 734 sponge will see this, and will stop replying for that address. 735 Gratuitous ARPs (or the machine ARPing for its gateway) will 736 replace the sponged address in the router ARP table. This 737 technique is quite effective; but, unfortunately, the ARP 738 sponge daemons were not really designed for this use (one of 739 the most widely deployed arp sponges [arpsponge], was designed 740 to deal with the disappearance of participants from an IXP) and 741 so are not optimized for this purpose. One daemon is needed 742 per subnet, the tuning is tricky (the scanning rate versus the 743 population rate versus retires, etc.) and sometimes the daemons 744 just seem to stop, requiring a restart of the daemon and 745 causing disruption. 747 Router mitigations 749 Some routers (often those based on Linux) implement a "negative 750 ARP cache" daemon. Simply put, if the router does not see a 751 reply to an ARP it can be configured to cache this information 752 for some interval. Unfortunately, the core routers in use 753 often do not support this. When a host connects to a network 754 and gets an IP address, it will ARP for its default gateway 755 (the router). The router will update its cache with the IP to 756 host MAC mapping learned from the request (passive ARP 757 learning). 759 Firewall unused space 761 The distribution of users on wireless networks / subnets 762 changes from one IETF meeting to the next (e.g SSIDs are 763 renamed, some SSIDs lose favor, etc). This makes utilization 764 for particular SSIDs difficult to predict ahead of time, but 765 usage can be monitored as attendees use the different networks. 766 Configuring multiple DHCP pools per subnet, and enabling them 767 sequentially, can create a large subnet, from which only 768 addresses in the lower portions are assigned. Therefore input 769 IP access lists can be applied, which deny traffic to the 770 upper, unused portions. Then the router does not attempt to 771 forward packets to the unused portions of the subnets, and so 772 does not ARP for it. This method has proven to be very 773 effective, but is somewhat of a blunt axe, is fairly labor 774 intensive, and requires coordination. 776 Disabling/filtering ARP requests 778 In general, the router does not need to ARP for hosts; when a 779 host connects, the router can learn the IP to MAC mapping from 780 the ARP request sent by that host. Consequently it should be 781 possible to disable and / or filter ARP requests from the 782 router. Unfortunately, ARP is a very low level / fundamental 783 part of the IP stack, and is often offloaded from the normal 784 control plane. While many routers can filter layer-2 traffic, 785 this is usually implemented as an input filter and / or has 786 limited ability to filter output broadcast traffic. This means 787 that the simple "just disable ARP or filter it outbound" seems 788 like a really simple (and obvious) solution, but 789 implementations / architectural issues make this difficult or 790 awkward in practice. 792 NAT 794 The broadcasts are overwhelmingly being caused by outside 795 scanning / backscatter traffic. To NAT the entire (or a large 796 portion) of the attendee networks would eliminate NAT 797 translation entries for unused addresses, and so the router 798 would never ARP for them. However, there are many reasons to 799 avoid using NAT in such a blanket fashion. 801 Stateful firewalls 803 Another obvious solution would be to put a stateful firewall 804 between the wireless network and the Internet. This firewall 805 would block incoming traffic not associated with an outbound 806 request. But this conflicts with the need and desire of the 807 IETF and other organizations to have the network as open as 808 possible and to honor the end-to-end principle. An attendee on 809 the meeting network should be an Internet host, and should be 810 able to receive unsolicited requests. Unfortunately, keeping 811 the network working and stable is the first priority and a 812 stateful firewall may be required in order to achieve this. 814 5.2. Mitigating Spurious Service Discovery Messages 816 In networks that must support hundreds of STAs, operators have 817 observed network degradation due to many devices simultaneously 818 registering with mDNS. In a network with many clients, it is 819 recommended to ensure that mDNS packets designed to discover 820 services in smaller home networks be constrained to avoid 821 disrupting other traffic. 823 6. Multicast Considerations for Other Wireless Media 825 Many of the causes of performance degradation described in earlier 826 sections are also observable for wireless media other than 802.11. 828 For instance, problems with power save, excess media occupancy, and 829 poor reliability will also affect 802.15.3 and 802.15.4. 830 Unfortunately, 802.15 media specifications do not yet include 831 mechanisms similar to those developed for 802.11. In fact, the 832 design philosophy for 802.15 is oriented towards minimality, with the 833 result that many such functions are relegated to operation within 834 higher layer protocols. This leads to a patchwork of non- 835 interoperable and vendor-specific solutions. See [uli] for some 836 additional discussion, and a proposal for a task group to resolve 837 similar issues, in which the multicast problems might be considered 838 for mitigation. 840 Similar considerations hold for most other wireless media. A brief 841 introduction is provided in [RFC5757] for the following: 843 o 802.16 WIMAX 844 o 3GPP/3GPP2 845 o DVB-H / DVB-IPDC 846 o TV Broadcast and Satellite Networks 848 7. Recommendations 850 This section provides some recommendations about the usage and 851 combinations of the multicast enhancements described in Section 4 and 852 Section 5. 854 Future protocol documents utilizing multicast signaling should be 855 carefully scrutinized if the protocol is likely to be used over 856 wireless media. 858 Proxy methods should be encouraged to conserve network bandwidth and 859 power utilization by low-power devices. The device can use a unicast 860 message to its proxy, and then the proxy can take care of any needed 861 multicast operations. 863 Multicast signaling for wireless devices should be done in a way 864 compatible with low duty-cycle operation. 866 8. Discussion Items 868 This section suggests two discussion items for further resolution. 870 The IETF should determine guidelines by which it may be decided that 871 multicast packets are to be sent wired. For example, 802.1ak works 872 on ethernet and Wi-Fi. 802.1ak has been pulled into 802.1Q as of 873 802.1Q-2011. If a generic solution is not found, guidelines for 874 multicast over Wi-Fi should be established. 876 Reliable registration to Layer-2 multicast groups and a reliable 877 multicast operation at Layer-2 might provide a generic solution. 878 There is no need to support 2^24 groups to get solicited node 879 multicast working: it is possible to simply select a number of 880 trailing bits that make sense for a given network size to limit the 881 number of unwanted deliveries to reasonable levels. IEEE 802.1, 882 802.11, and 802.15 should be encouraged to revisit L2 multicast 883 issues. In reality, Wi-Fi provides a broadcast service, not a 884 multicast service. On the physical medium, all frames are broadcast 885 except in very unusual cases in which special beamforming 886 transmitters are used. Unicast offers the advantage of being much 887 faster (2 orders of magnitude) and much more reliable (L2 ARQ). 889 9. Security Considerations 891 This document does not introduce or modify any security mechanisms. 892 Multicast is made more secure in a variety of ways. [RFC4601], for 893 instance, mandates the use of IPsec to ensure authentication of the 894 link-local messages in the Protocol Independent Multicast - Sparse 895 Mode (PIM-SM) routing protocol. [RFC5796]specifies mechanisms to 896 authenticate the PIM-SM link-local messages using the IP security 897 (IPsec) Encapsulating Security Payload (ESP) or (optionally) the 898 Authentication Header (AH). 900 As noted in [group_key], the unreliable nature of multicast 901 transmission over wireless media can cause subtle problems with 902 multicast group key management and updates. When WPA (TKIP) or WPA2 903 (AES-CCMP) encryption is in use, AP to client (From DS) multicasts 904 have to be encrypted with a separate encryption key that is known to 905 all of the clients (this is called the Group Key). Quoting further 906 from that website, "... most clients are able to get connected and 907 surf the web, check email, etc. even when From DS multicasts are 908 broken. So a lot of people don't realize they have multicast 909 problems on their network..." 911 10. IANA Considerations 913 This document does not request any IANA actions. 915 11. Acknowledgements 917 This document has benefitted from discussions with the following 918 people, in alphabetical order: Mikael Abrahamsson, Bill Atwood, 919 Stuart Cheshire, Donald Eastlake, Toerless Eckert, Jake Holland, Joel 920 Jaeggli, Jan Komissar, David Lamparter, Morten Pedersen, Pascal 921 Thubert, Jeffrey (Zhaohui) Zhang 923 12. Informative References 925 [arpsponge] 926 Wessel, M. and N. Sijm, "Effects of IPv4 and IPv6 address 927 resolution on AMS-IX and the ARP Sponge", July 2009, 928 . 931 [bridge-mc-2-uc] 932 Fietkau, F., "bridge: multicast to unicast", Jan 2017, 933 . 936 [CAB] Fietkau, F., "Limit multicast buffer hardware queue 937 depth", 2013, 938 . 940 [Deri-2010] 941 Deri, L. and J. Gasparakis, "10 Gbit Hardware Packet 942 Filtering Using Commodity Network Adapters", RIPE 61, 943 2010, . 946 [dot11] "IEEE 802 Wireless", "802.11-2016 - IEEE Standard for 947 Information technology--Telecommunications and information 948 exchange between systems Local and metropolitan area 949 networks--Specific requirements - Part 11: Wireless LAN 950 Medium Access Control (MAC) and Physical Layer (PHY) 951 Specification (includes 802.11v amendment)", March 2016, 952 . 955 [dot11-proxyarp] 956 Hiertz, G., Mestanov, F., and B. Hart, "Proxy ARP in 957 802.11ax", September 2015, 958 . 961 [dot11aa] "IEEE 802 Wireless", "Part 11: Wireless LAN Medium Access 962 Control (MAC) and Physical Layer (PHY) Specifications 963 Amendment 2: MAC Enhancements for Robust Audio Video 964 Streaming", March 2012, 965 . 967 [group_key] 968 Spiff, "Why do some WiFi routers block multicast packets 969 going from wired to wireless?", Jan 2017, 970 . 974 [I-D.ietf-6lo-backbone-router] 975 Thubert, P., Perkins, C., and E. Levy-Abegnoli, "IPv6 976 Backbone Router", draft-ietf-6lo-backbone-router-13 (work 977 in progress), September 2019. 979 [I-D.ietf-6tisch-architecture] 980 Thubert, P., "An Architecture for IPv6 over the TSCH mode 981 of IEEE 802.15.4", draft-ietf-6tisch-architecture-28 (work 982 in progress), October 2019. 984 [I-D.ietf-mboned-driad-amt-discovery] 985 Holland, J., "DNS Reverse IP AMT Discovery", draft-ietf- 986 mboned-driad-amt-discovery-09 (work in progress), October 987 2019. 989 [ietf_802-11] 990 Stanley, D., "IEEE 802.11 multicast capabilities", Nov 991 2015, . 995 [mc-ack-mux] 996 Tanaka, Y., Sakai, E., Morioka, Y., Mori, M., Hiertz, G., 997 and S. Coffey, "Multiplexing of Acknowledgements for 998 Multicast Transmission", July 2015, 999 . 1003 [mc-prob-stmt] 1004 Abrahamsson, M. and A. Stephens, "Multicast on 802.11", 1005 March 2015, . 1008 [mc-props] 1009 Stephens, A., "IEEE 802.11 multicast properties", March 1010 2015, . 1014 [Oliva2013] 1015 de la Oliva, A., Serrano, P., Salvador, P., and A. Banchs, 1016 "Performance evaluation of the IEEE 802.11aa multicast 1017 mechanisms for video streaming", 2013 IEEE 14th 1018 International Symposium on "A World of Wireless, Mobile 1019 and Multimedia Networks" (WoWMoM) pp. 1-9, June 2013. 1021 [RFC2461] Narten, T., Nordmark, E., and W. Simpson, "Neighbor 1022 Discovery for IP Version 6 (IPv6)", RFC 2461, 1023 DOI 10.17487/RFC2461, December 1998, 1024 . 1026 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 1027 "Considerations for Internet Group Management Protocol 1028 (IGMP) and Multicast Listener Discovery (MLD) Snooping 1029 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 1030 . 1032 [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, 1033 "Protocol Independent Multicast - Sparse Mode (PIM-SM): 1034 Protocol Specification (Revised)", RFC 4601, 1035 DOI 10.17487/RFC4601, August 2006, 1036 . 1038 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1039 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1040 DOI 10.17487/RFC4861, September 2007, 1041 . 1043 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1044 Address Autoconfiguration", RFC 4862, 1045 DOI 10.17487/RFC4862, September 2007, 1046 . 1048 [RFC5757] Schmidt, T., Waehlisch, M., and G. Fairhurst, "Multicast 1049 Mobility in Mobile IP Version 6 (MIPv6): Problem Statement 1050 and Brief Survey", RFC 5757, DOI 10.17487/RFC5757, 1051 February 2010, . 1053 [RFC5796] Atwood, W., Islam, S., and M. Siami, "Authentication and 1054 Confidentiality in Protocol Independent Multicast Sparse 1055 Mode (PIM-SM) Link-Local Messages", RFC 5796, 1056 DOI 10.17487/RFC5796, March 2010, 1057 . 1059 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 1060 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 1061 DOI 10.17487/RFC6282, September 2011, 1062 . 1064 [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, 1065 DOI 10.17487/RFC6762, February 2013, 1066 . 1068 [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service 1069 Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013, 1070 . 1072 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 1073 Bormann, "Neighbor Discovery Optimization for IPv6 over 1074 Low-Power Wireless Personal Area Networks (6LoWPANs)", 1075 RFC 6775, DOI 10.17487/RFC6775, November 2012, 1076 . 1078 [RFC6970] Boucadair, M., Penno, R., and D. Wing, "Universal Plug and 1079 Play (UPnP) Internet Gateway Device - Port Control 1080 Protocol Interworking Function (IGD-PCP IWF)", RFC 6970, 1081 DOI 10.17487/RFC6970, July 2013, 1082 . 1084 [RFC7450] Bumgardner, G., "Automatic Multicast Tunneling", RFC 7450, 1085 DOI 10.17487/RFC7450, February 2015, 1086 . 1088 [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. 1089 Perkins, "Registration Extensions for IPv6 over Low-Power 1090 Wireless Personal Area Network (6LoWPAN) Neighbor 1091 Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, 1092 . 1094 [Tramarin2017] 1095 Tramarin, F., Vitturi, S., and M. Luvisotto, "IEEE 802.11n 1096 for Distributed Measurement Systems", 2017 IEEE 1097 International Instrumentation and Measurement Technology 1098 Conference (I2MTC) pp. 1-6, May 2017. 1100 [uli] Kinney, P., "LLC Proposal for 802.15.4", Nov 2015, 1101 . 1104 Appendix A. Changes in this draft between revisions 06 versus 07 1106 This section lists the changes between revisions ...-06.txt and 1107 ...-07.txt of draft-ietf-mboned-ieee802-mcast-problems. 1109 o Improved wording in section describing ARPsponge. 1110 o Removed DRIAD as a discovery mechanism for multicast relays. 1111 o Updated bibliographic citations, repaired broken URLs as needed. 1112 o More editorial improvements and grammatical corrections. 1114 Appendix B. Changes in this draft between revisions 05 versus 06 1116 This section lists the changes between revisions ...-05.txt and 1117 ...-06.txt of draft-ietf-mboned-ieee802-mcast-problems. 1119 o Included new text in Security Considerations to alert about 1120 problems regarding Group Key management caused by multicast 1121 unreliability and implementation bugs. 1122 o Included DRIAD as a discovery mechanism for multicast relays. 1123 o Corrected occurrences of "which" versus "that" and "amount" versus 1124 "number". 1125 o Updated bibliographic citations, included URLs as needed. 1127 o More editorial improvements and grammatical corrections. 1129 Appendix C. Changes in this draft between revisions 04 versus 05 1131 This section lists the changes between revisions ...-04.txt and 1132 ...-05.txt of draft-ietf-mboned-ieee802-mcast-problems. 1134 o Incorporated text from Jake Holland for a new section about 1135 conversion of multicast to unicast and included AMT as an existing 1136 solution. 1137 o Included some text about likely future multicast applications that 1138 will emphasize the need for attention to the technical matters 1139 collected in this document. 1140 o Further modified text to be more generic instead of referring 1141 specifically to IETF conference situations. 1142 o Modified text to be more generic instead of referring specifically 1143 to Bonjour. 1144 o Added uPnP as a representative multicast protocol in IP networks. 1145 o Referred to Linux bridging code for multicast to unicast. 1146 o Updated bibliographic citations, included URLs as needed. 1147 o More editorial improvements and grammatical corrections. 1149 Appendix D. Changes in this draft between revisions 03 versus 04 1151 This section lists the changes between revisions ...-03.txt and 1152 ...-04.txt of draft-ietf-mboned-ieee802-mcast-problems. 1154 o Replaced "client" by "STA". 1155 o Used terminology "Wi-Fi" throughout. 1156 o Many editorial improvements and grammatical corrections. 1157 o Modified text to be more generic instead of referring specifically 1158 to IETF conference situations. 1159 o Cited [RFC5757] for introduction to other wireless media. 1160 o Updated bibliographic citations. 1162 Authors' Addresses 1164 Charles E. Perkins 1166 Phone: +1-408-330-4586 1167 Email: charliep@computer.org 1168 Mike McBride 1169 Futurewei Inc. 1170 2330 Central Expressway 1171 Santa Clara, CA 95055 1172 USA 1174 Email: michael.mcbride@futurewei.com 1176 Dorothy Stanley 1177 Hewlett Packard Enterprise 1178 2000 North Naperville Rd. 1179 Naperville, IL 60566 1180 USA 1182 Phone: +1 630 979 1572 1183 Email: dstanley@arubanetworks.com 1185 Warren Kumari 1186 Google 1187 1600 Amphitheatre Parkway 1188 Mountain View, CA 94043 1189 USA 1191 Email: warren@kumari.net 1193 Juan Carlos Zuniga 1194 SIGFOX 1195 425 rue Jean Rostand 1196 Labege 31670 1197 France 1199 Email: j.c.zuniga@ieee.org