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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Area C.E. Perkins 3 Internet-Draft Blue Meadow Networks 4 Intended status: Informational M. McBride 5 Expires: 29 January 2022 Futurewei 6 D. Stanley 7 HPE 8 W. Kumari 9 Google 10 JC. Zuniga 11 SIGFOX 12 28 July 2021 14 Multicast Considerations over IEEE 802 Wireless Media 15 draft-ietf-mboned-ieee802-mcast-problems-15 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 known limitations of 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 29 January 2022. 46 Copyright Notice 48 Copyright (c) 2021 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 (https://trustee.ietf.org/ 53 license-info) in effect on the date of publication of this document. 54 Please review these documents carefully, as they describe your rights 55 and restrictions with respect to this document. Code Components 56 extracted from this document must include Simplified BSD License text 57 as described in Section 4.e of the Trust Legal Provisions and are 58 provided without warranty as described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 63 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 64 3. Identified multicast issues . . . . . . . . . . . . . . . . . 5 65 3.1. Issues at Layer 2 and Below . . . . . . . . . . . . . . . 5 66 3.1.1. Multicast reliability . . . . . . . . . . . . . . . . 5 67 3.1.2. Lower and Variable Data Rate . . . . . . . . . . . . 6 68 3.1.3. Capacity and Impact on Interference . . . . . . . . . 7 69 3.1.4. Power-save Effects on Multicast . . . . . . . . . . . 7 70 3.2. Issues at Layer 3 and Above . . . . . . . . . . . . . . . 7 71 3.2.1. IPv4 issues . . . . . . . . . . . . . . . . . . . . . 8 72 3.2.2. IPv6 issues . . . . . . . . . . . . . . . . . . . . . 8 73 3.2.3. MLD issues . . . . . . . . . . . . . . . . . . . . . 9 74 3.2.4. Spurious Neighbor Discovery . . . . . . . . . . . . . 9 75 4. Multicast protocol optimizations . . . . . . . . . . . . . . 10 76 4.1. Proxy ARP in 802.11-2012 . . . . . . . . . . . . . . . . 10 77 4.2. IPv6 Address Registration and Proxy Neighbor Discovery . 11 78 4.3. Buffering to Improve Battery Life . . . . . . . . . . . . 12 79 4.4. Limiting multicast buffer hardware queue depth . . . . . 13 80 4.5. IPv6 support in 802.11-2012 . . . . . . . . . . . . . . . 13 81 4.6. Using Unicast Instead of Multicast . . . . . . . . . . . 14 82 4.6.1. Overview . . . . . . . . . . . . . . . . . . . . . . 14 83 4.6.2. Layer 2 Conversion to Unicast . . . . . . . . . . . . 14 84 4.6.3. Directed Multicast Service (DMS) . . . . . . . . . . 14 85 4.6.4. Automatic Multicast Tunneling (AMT) . . . . . . . . . 15 86 4.7. GroupCast with Retries (GCR) . . . . . . . . . . . . . . 15 87 5. Operational optimizations . . . . . . . . . . . . . . . . . . 16 88 5.1. Mitigating Problems from Spurious Neighbor Discovery . . 16 89 5.2. Mitigating Spurious Service Discovery Messages . . . . . 18 90 6. Multicast Considerations for Other Wireless Media . . . . . . 18 91 7. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 19 92 8. On-going Discussion Items . . . . . . . . . . . . . . . . . . 19 93 9. Security Considerations . . . . . . . . . . . . . . . . . . . 20 94 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 95 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21 96 12. Informative References . . . . . . . . . . . . . . . . . . . 21 97 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 99 1. Introduction 101 Well-known issues with multicast have prevented the deployment of 102 multicast in 802.11 [dot11] and other local-area wireless 103 environments, as described in [mc-props], [mc-prob-stmt]. 104 Performance issues have been observed when multicast packet 105 transmissions of IETF protocols are used over IEEE 802 wireless 106 media. Even though enhancements for multicast transmissions have 107 been designed at both IETF and IEEE 802, incompatibilities still 108 exist between specifications, implementations and configuration 109 choices. 111 Many IETF protocols depend on multicast/broadcast for delivery of 112 control messages to multiple receivers. Multicast allows sending 113 data to multiple interested recipients without the source needing to 114 send duplicate data to each recipient. With broadcast traffic, data 115 is sent to every device regardless of their expressed interest in the 116 data. Multicast is used for various purposes such as neighbor 117 discovery, network flooding, address resolution, as well minimizing 118 media occupancy for the transmission of data that is intended for 119 multiple receivers. In addition to protocol use of broadcast/ 120 multicast for control messages, more applications, such as push to 121 talk in hospitals, or video in enterprises, universities, and homes, 122 are sending multicast IP to end user devices, which are increasingly 123 using Wi-Fi for their connectivity. 125 IETF protocols typically rely on network protocol layering in order 126 to reduce or eliminate any dependence of higher level protocols on 127 the specific nature of the MAC layer protocols or the physical media. 128 In the case of multicast transmissions, higher level protocols have 129 traditionally been designed as if transmitting a packet to an IP 130 address had the same cost in interference and network media access, 131 regardless of whether the destination IP address is a unicast address 132 or a multicast or broadcast address. This model was reasonable for 133 networks where the physical medium was wired, like Ethernet. 134 Unfortunately, for many wireless media, the costs to access the 135 medium can be quite different. Multicast over Wi-Fi has often been 136 plagued by such poor performance that it is disallowed. Some 137 enhancements have been designed in IETF protocols that are assumed to 138 work primarily over wireless media. However, these enhancements are 139 usually implemented in limited deployments and not widespread on most 140 wireless networks. 142 IEEE 802 wireless protocols have been designed with certain features 143 to support multicast traffic. For instance, lower modulations are 144 used to transmit multicast frames, so that these can be received by 145 all stations in the cell, regardless of the distance or path 146 attenuation from the base station or access point. However, these 147 lower modulation transmissions occupy the medium longer; they hamper 148 efficient transmission of traffic using higher order modulations to 149 nearby stations. For these and other reasons, IEEE 802 working 150 groups such as 802.11 have designed features to improve the 151 performance of multicast transmissions at Layer 2 [ietf_802-11]. In 152 addition to protocol design features, certain operational and 153 configuration enhancements can ameliorate the network performance 154 issues created by multicast traffic, as described in Section 5. 156 There seems to be general agreement that these problems will not be 157 fixed anytime soon, primarily because it's expensive to do so and due 158 to multicast being unreliable. Compared to unicast over Wi-Fi, 159 multicast is often treated as somewhat of a second class citizen, 160 even though there are many protocols using multicast. Something 161 needs to be provided in order to make them more reliable. IPv6 162 neighbor discovery saturating the Wi-Fi link is only part of the 163 problem. Wi-Fi traffic classes may help. This document is intended 164 to help make the determination about what problems should be solved 165 by the IETF and what problems should be solved by the IEEE (see 166 Section 8). 168 This document details various problems caused by multicast 169 transmission over wireless networks, including high packet error 170 rates, no acknowledgements, and low data rate. It also explains some 171 enhancements that have been designed at the IETF and IEEE 802.11 to 172 ameliorate the effects of the radio medium on multicast traffic. 173 Recommendations are also provided to implementors about how to use 174 and combine these enhancements. Some advice about the operational 175 choices that can be taken is also included. It is likely that this 176 document will also be considered relevant to designers of future IEEE 177 wireless specifications. 179 2. Terminology 181 This document uses the following definitions: 183 ACK 184 The 802.11 layer 2 acknowledgement 186 AP 187 IEEE 802.11 Access Point 189 basic rate 190 The slowest rate of all the connected devices, at which multicast 191 and broadcast traffic is generally transmitted 193 DTIM 194 Delivery Traffic Indication Map (DTIM): An information element 195 that advertises whether or not any associated stations have 196 buffered multicast or broadcast frames 198 MCS 199 Modulation and Coding Scheme 201 NOC 202 Network Operations Center 204 PER 205 Packet Error Rate 207 STA 208 802.11 station (e.g. handheld device) 210 TIM 211 Traffic Indication Map (TIM): An information element that 212 advertises whether or not any associated stations have buffered 213 unicast frames 215 3. Identified multicast issues 217 3.1. Issues at Layer 2 and Below 219 In this section some of the issues related to the use of multicast 220 transmissions over IEEE 802 wireless technologies are described. 222 3.1.1. Multicast reliability 224 Multicast traffic is typically much less reliable than unicast 225 traffic. Since multicast makes point-to-multipoint communications, 226 multiple acknowledgements would be needed to guarantee reception at 227 all recipients. And since there are no ACKs for multicast packets, 228 it is not possible for the Access Point (AP) to know whether or not a 229 retransmission is needed. Even in the wired Internet, this 230 characteristic often causes undesirably high error rates. This has 231 contributed to the relatively slow uptake of multicast applications 232 even though the protocols have long been available. The situation 233 for wireless links is much worse, and is quite sensitive to the 234 presence of background traffic. Consequently, there can be a high 235 packet error rate (PER) due to lack of retransmission, and because 236 the sender never backs off. PER is the ratio, in percent, of the 237 number of packets not successfully received by the device. It is not 238 uncommon for there to be a packet loss rate of 5% or more, which is 239 particularly troublesome for video and other environments where high 240 data rates and high reliability are required. 242 3.1.2. Lower and Variable Data Rate 244 Multicast over wired differs from multicast over wireless because 245 transmission over wired links often occurs at a fixed rate. Wi-Fi, 246 on the other hand, has a transmission rate that varies depending upon 247 the STA's proximity to the AP. The throughput of video flows, and 248 the capacity of the broader Wi-Fi network, will change with device 249 movement. This impacts the ability for QoS solutions to effectively 250 reserve bandwidth and provide admission control. 252 For wireless stations authenticated and linked with an Access Point, 253 the power necessary for good reception can vary from station to 254 station. For unicast, the goal is to minimize power requirements 255 while maximizing the data rate to the destination. For multicast, 256 the goal is simply to maximize the number of receivers that will 257 correctly receive the multicast packet; generally the Access Point 258 has to use a much lower data rate at a power level high enough for 259 even the farthest station to receive the packet, for example as 260 briefly mentioned in section 2 of [RFC5757]. Consequently, the data 261 rate of a video stream, for instance, would be constrained by the 262 environmental considerations of the least reliable receiver 263 associated with the Access Point. 265 Because more robust modulation and coding schemes (MCSs) have longer 266 range but also lower data rate, multicast / broadcast traffic is 267 generally transmitted at the slowest rate of all the connected 268 devices. This is also known as the basic rate. The amount of 269 additional interference depends on the specific wireless technology. 270 In fact, backward compatibility and multi-stream implementations mean 271 that the maximum unicast rates are currently up to a few Gbps, so 272 there can be more than 3 orders of magnitude difference in the 273 transmission rate between multicast / broadcast versus optimal 274 unicast forwarding. Some techniques employed to increase spectral 275 efficiency, such as spatial multiplexing in MIMO systems, are not 276 available with more than one intended receiver; it is not the case 277 that backwards compatibility is the only factor responsible for lower 278 multicast transmission rates. 280 Wired multicast also affects wireless LANs when the AP extends the 281 wired segment; in that case, multicast / broadcast frames on the 282 wired LAN side are copied to the Wireless Local Area Network (WLAN). 283 Since broadcast messages are transmitted at the most robust MCS, many 284 large frames are sent at a slow rate over the air. 286 3.1.3. Capacity and Impact on Interference 288 Transmissions at a lower rate require longer occupancy of the 289 wireless medium and thus take away from the airtime of other 290 communications and degrade the overall capacity. Furthermore, 291 transmission at higher power, as is required to reach all multicast 292 STAs associated to the AP, proportionately increases the area of 293 interference with other consumers of the radio spectrum. 295 3.1.4. Power-save Effects on Multicast 297 One of the characteristics of multicast transmission over wifi is 298 that every station has to be configured to wake up to receive the 299 multicast frame, even though the received packet may ultimately be 300 discarded. This process can have a large effect on the power 301 consumption by the multicast receiver station. For this reason there 302 are workarounds, such as Directed Multicast Service (DMS) described 303 in Section 4, to prevent unnecessarily waking up stations. 305 Multicast (and unicast) can work poorly with the power-save 306 mechanisms defined in IEEE 802.11e, for the following reasons. 308 * Clients may be unable to stay in sleep mode due to multicast 309 control packets frequently waking them up. 310 * A unicast packet is delayed until an STA wakes up and requests it. 311 Unicast traffic may also be delayed to improve power save, 312 efficiency and increase probability of aggregation. 313 * Multicast traffic is delayed in a wireless network if any of the 314 STAs in that network are power savers. All STAs associated to the 315 AP have to be awake at a known time to receive multicast traffic. 316 * Packets can also be discarded due to buffer limitations in the AP 317 and non-AP STA. 319 3.2. Issues at Layer 3 and Above 321 This section identifies some representative IETF protocols, and 322 describes possible negative effects due to performance degradation 323 when using multicast transmissions for control messages. Common uses 324 of multicast include: 326 * Control plane signaling 327 * Neighbor Discovery 328 * Address Resolution 329 * Service Discovery 330 * Applications (video delivery, stock data, etc.) 331 * On-demand routing 332 * Backbone construction 333 * Other L3 protocols (non-IP) 335 User Datagram Protocol (UDP) is the most common transport layer 336 protocol for multicast applications. By itself, UDP is not reliable 337 -- messages may be lost or delivered out of order. 339 3.2.1. IPv4 issues 341 The following list contains some representative discovery protocols, 342 which utilize broadcast/multicast, that are used with IPv4. 344 * ARP [RFC0826] 345 * DHCP [RFC2131] 346 * mDNS [RFC6762] 347 * uPnP [RFC6970] 349 After initial configuration, ARP (described in more detail later), 350 DHCP and uPnP occur much less commonly, but service discovery can 351 occur at any time. Some widely-deployed service discovery protocols 352 (e.g., for finding a printer) utilize mDNS (i.e., multicast) which is 353 often dropped by operators. Even if multicast snooping [RFC4541] 354 (which provides the benefit of conserving bandwidth on those segments 355 of the network where no node has expressed interest in receiving 356 packets addressed to the group address) is utilized, many devices can 357 register at once and cause serious network degradation. 359 3.2.2. IPv6 issues 361 IPv6 makes extensive use of multicast, including the following: 363 * DHCPv6 [RFC8415] 364 * Protocol Independent Multicast (PIM) [RFC7761] 365 * IPv6 Neighbor Discovery Protocol (NDP) [RFC4861] 366 * multicast DNS (mDNS) [RFC6762] 367 * Router Discovery [RFC4286] 369 IPv6 NDP Neighbor Solicitation (NS) messages used in Duplicate 370 Address Detection (DAD) and Address Lookup make use of Link-Scope 371 multicast. In contrast to IPv4, an IPv6 node will typically use 372 multiple addresses, and may change them often for privacy reasons. 373 This intensifies the impact of multicast messages that are associated 374 to the mobility of a node. Router advertisement (RA) messages are 375 also periodically multicasted over the Link. 377 Neighbors may be considered lost if several consecutive Neighbor 378 Discovery packets fail. 380 3.2.3. MLD issues 382 Multicast Listener Discovery (MLD) [RFC4541] is used to identify 383 members of a multicast group that are connected to the ports of a 384 switch. Forwarding multicast frames into a Wi-Fi-enabled area can 385 use switch support for hardware forwarding state information. 386 However, since IPv6 makes heavy use of multicast, each STA with an 387 IPv6 address will require state on the switch for several and 388 possibly many multicast solicited-node addresses. A solicited-node 389 multicast address is an IPv6 multicast address used by NDP to verify 390 whether an IPv6 address is already used by the local-link. Multicast 391 addresses that do not have forwarding state installed (perhaps due to 392 hardware memory limitations on the switch) cause frames to be flooded 393 on all ports of the switch. Some switch vendors do not support MLD, 394 for link-scope multicast, due to the increase it can cause in state. 396 3.2.4. Spurious Neighbor Discovery 398 On the Internet there is a "background radiation" of scanning traffic 399 (people scanning for vulnerable machines) and backscatter (responses 400 from spoofed traffic, etc). This means that routers very often 401 receive packets destined for IPv4 addresses regardless of whether 402 those IP addresses are in use. In the cases where the IP is assigned 403 to a host, the router broadcasts an ARP request, gets back an ARP 404 reply, and caches it; then traffic can be delivered to the host. 405 When the IP address is not in use, the router broadcasts one (or 406 more) ARP requests, and never gets a reply. This means that it does 407 not populate the ARP cache, and the next time there is traffic for 408 that IP address the router will rebroadcast the ARP requests. 410 The rate of these ARP requests is proportional to the size of the 411 subnets, the rate of scanning and backscatter, and how long the 412 router keeps state on non-responding ARPs. As it turns out, this 413 rate is inversely proportional to how occupied the subnet is (valid 414 ARPs end up in a cache, stopping the broadcasting; unused IPs never 415 respond, and so cause more broadcasts). Depending on the address 416 space in use, the time of day, how occupied the subnet is, and other 417 unknown factors, thousands of broadcasts per second have been 418 observed. Around 2,000 broadcasts per second have been observed at 419 the IETF NOC during face-to-face meetings. 421 With Neighbor Discovery for IPv6 [RFC4861], nodes accomplish address 422 resolution by multicasting a Neighbor Solicitation that asks the 423 target node to return its link-layer address. Neighbor Solicitation 424 messages are multicast to the solicited-node multicast address of the 425 target address. The target returns its link-layer address in a 426 unicast Neighbor Advertisement message. A single request-response 427 pair of packets is sufficient for both the initiator and the target 428 to resolve each other's link-layer addresses; the initiator includes 429 its link-layer address in the Neighbor Solicitation. 431 On a wired network, there is not a huge difference between unicast, 432 multicast and broadcast traffic. Due to hardware filtering (see, 433 e.g., [Deri-2010]), inadvertently flooded traffic (or excessive 434 ethernet multicast) on wired networks can be quite a bit less costly, 435 compared to wireless cases where sleeping devices have to wake up to 436 process packets. Wired Ethernets tend to be switched networks, 437 further reducing interference from multicast. There is effectively 438 no collision / scheduling problem except at extremely high port 439 utilizations. 441 This is not true in the wireless realm; wireless equipment is often 442 unable to send high volumes of broadcast and multicast traffic, 443 causing numerous broadcast and multicast packets to be dropped. 444 Consequently, when a host connects it is often not able to complete 445 DHCP, and IPv6 RAs get dropped, leading to users being unable to use 446 the network. 448 4. Multicast protocol optimizations 450 This section lists some optimizations that have been specified in 451 IEEE 802 and IETF that are aimed at reducing or eliminating the 452 issues discussed in Section 3. 454 4.1. Proxy ARP in 802.11-2012 456 The AP knows the MAC address and IP address for all associated STAs. 457 In this way, the AP acts as the central "manager" for all the 802.11 458 STAs in its basic service set (BSS). Proxy ARP is easy to implement 459 at the AP, and offers the following advantages: 461 * Reduced broadcast traffic (transmitted at low MCS) on the wireless 462 medium 463 * STA benefits from extended power save in sleep mode, as ARP 464 requests for STA's IP address are handled instead by the AP. 465 * ARP frames are kept off the wireless medium. 466 * No changes are needed to STA implementation. 468 Here is the specification language as described in clause 10.23.13 of 469 [dot11-proxyarp]: 471 When the AP supports Proxy ARP "[...] the AP shall maintain a 472 Hardware Address to Internet Address mapping for each associated 473 station, and shall update the mapping when the Internet Address of 474 the associated station changes. When the IPv4 address being 475 resolved in the ARP request packet is used by a non-AP STA 476 currently associated to the BSS, the proxy ARP service shall 477 respond on behalf of the non-AP STA". 479 4.2. IPv6 Address Registration and Proxy Neighbor Discovery 481 As used in this section, a Low-Power Wireless Personal Area Network 482 (6LoWPAN) denotes a low power lossy network (LLN) that supports 483 6LoWPAN Header Compression (HC) [RFC6282]. A 6TiSCH network 484 [I-D.ietf-6tisch-architecture] is an example of a 6LowPAN. In order 485 to control the use of IPv6 multicast over 6LoWPANs, the 6LoWPAN 486 Neighbor Discovery (6LoWPAN ND) [RFC6775] standard defines an address 487 registration mechanism that relies on a central registry to assess 488 address uniqueness, as a substitute to the inefficient DAD mechanism 489 found in the mainstream IPv6 Neighbor Discovery Protocol (NDP) 490 [RFC4861][RFC4862]. 492 The 6lo Working Group has specified an update [RFC8505] to RFC6775. 493 Wireless devices can register their address to a Backbone Router 494 [I-D.ietf-6lo-backbone-router], which proxies for the registered 495 addresses with the IPv6 NDP running on a high speed aggregating 496 backbone. The update also enables a proxy registration mechanism on 497 behalf of the registered node, e.g. by a 6LoWPAN router to which the 498 mobile node is attached. 500 The general idea behind the backbone router concept is that broadcast 501 and multicast messaging should be tightly controlled in a variety of 502 WLANs and Wireless Personal Area Networks (WPANs). Connectivity to a 503 particular link that provides the subnet should be left to Layer-3. 504 The model for the Backbone Router operation is represented in 505 Figure 1. 507 | 508 +-----+ 509 | | Gateway (default) router 510 | | 511 +-----+ 512 | 513 | Backbone Link 514 +--------------------+------------------+ 515 | | | 516 +-----+ +-----+ +-----+ 517 | | Backbone | | Backbone | | Backbone 518 | | router 1 | | router 2 | | router 3 519 +-----+ +-----+ +-----+ 520 o o o o o o 521 o o o o o o o o o o o o o o 522 o 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 524 o o o o o o o 526 LLN 1 LLN 2 LLN 3 528 Figure 1: Backbone Link and Backbone Routers 530 LLN nodes can move freely from an LLN anchored at one IPv6 Backbone 531 Router to an LLN anchored at another Backbone Router on the same 532 backbone, keeping any of the IPv6 addresses they have configured. 533 The Backbone Routers maintain a Binding Table of their Registered 534 Nodes, which serves as a distributed database of all the LLN Nodes. 535 An extension to the Neighbor Discovery Protocol is introduced to 536 exchange Binding Table information across the Backbone Link as needed 537 for the operation of IPv6 Neighbor Discovery. 539 RFC6775 and follow-on work [RFC8505] address the needs of LLNs, and 540 similar techniques are likely to be valuable on any type of link 541 where sleeping devices are attached, or where the use of broadcast 542 and multicast operations should be limited. 544 4.3. Buffering to Improve Battery Life 546 Methods have been developed to help save battery life; for example, a 547 device might not wake up when the AP receives a multicast packet. 548 The AP acts on behalf of STAs in various ways. To enable use of the 549 power-saving feature for STAs in its BSS, the AP buffers frames for 550 delivery to the STA at the time when the STA is scheduled for 551 reception. If an AP, for instance, expresses a DTIM (Delivery 552 Traffic Indication Message) of 3 then the AP will send a multicast 553 packet every 3 packets. In fact, when any single wireless STA 554 associated with an access point has 802.11 power-save mode enabled, 555 the access point buffers all multicast frames and sends them only 556 after the next DTIM beacon. 558 In practice, most AP's will send a multicast every 30 packets. For 559 unicast the AP could send a TIM (Traffic Indication Message), but for 560 multicast the AP sends a broadcast to everyone. DTIM does power 561 management but STAs can choose whether or not to wake up and whether 562 or not to drop the packet. Unfortunately, without proper 563 administrative control, such STAs may be unable to determine why 564 their multicast operations do not work. 566 4.4. Limiting multicast buffer hardware queue depth 568 The CAB (Content after Beacon) queue is used for beacon-triggered 569 transmission of buffered multicast frames. If lots of multicast 570 frames were buffered, and this queue fills up, it drowns out all 571 regular traffic. To limit the damage that buffered traffic can do, 572 some drivers limit the amount of queued multicast data to a fraction 573 of the beacon_interval. An example of this is [CAB]. 575 4.5. IPv6 support in 802.11-2012 577 IPv6 uses NDP instead of ARP. Every IPv6 node subscribes to a 578 special multicast address for this purpose. 580 Here is the specification language from clause 10.23.13 of 581 [dot11-proxyarp]: 583 "When an IPv6 address is being resolved, the Proxy Neighbor 584 Discovery service shall respond with a Neighbor Advertisement 585 message [...] on behalf of an associated STA to an [ICMPv6] 586 Neighbor Solicitation message [...]. When MAC address mappings 587 change, the AP may send unsolicited Neighbor Advertisement 588 Messages on behalf of a STA." 590 NDP may be used to request additional information 592 * Maximum Transmission Unit 593 * Router Solicitation 594 * Router Advertisement, etc. 596 NDP messages are sent as group addressed (broadcast) frames in 597 802.11. Using the proxy operation helps to keep NDP messages off the 598 wireless medium. 600 4.6. Using Unicast Instead of Multicast 602 It is often possible to transmit multicast control and data messages 603 by using unicast transmissions to each station individually. 605 4.6.1. Overview 607 In many situations, it's a good choice to use unicast instead of 608 multicast over the Wi-Fi link. This avoids most of the problems 609 specific to multicast over Wi-Fi, since the individual frames are 610 then acknowledged and buffered for power save clients, in the way 611 that unicast traffic normally operates. 613 This approach comes with the tradeoff of sometimes sending the same 614 packet multiple times over the Wi-Fi link. However, in many cases, 615 such as video into a residential home network, this can be a good 616 tradeoff, since the Wi-Fi link may have enough capacity for the 617 unicast traffic to be transmitted to each subscribed STA, even though 618 multicast addressing may have been necessary for the upstream access 619 network. 621 Several technologies exist that can be used to arrange unicast 622 transport over the Wi-Fi link, outlined in the subsections below. 624 4.6.2. Layer 2 Conversion to Unicast 626 It is often possible to transmit multicast control and data messages 627 by using unicast transmissions to each station individually. 629 Although there is not yet a standardized method of conversion, at 630 least one widely available implementation exists in the Linux 631 bridging code [bridge-mc-2-uc]. Other proprietary implementations 632 are available from various vendors. In general, these 633 implementations perform a straightforward mapping for groups or 634 channels, discovered by IGMP or MLD snooping, to the corresponding 635 unicast MAC addresses. 637 4.6.3. Directed Multicast Service (DMS) 639 There are situations where more is needed than simply converting 640 multicast to unicast. For these purposes, DMS enables an STA to 641 request that the AP transmit multicast group addressed frames 642 destined to the requesting STAs as individually addressed frames 643 [i.e., convert multicast to unicast]. Here are some characteristics 644 of DMS: 646 * Requires 802.11n A-MSDUs 647 * Individually addressed frames are acknowledged and are buffered 648 for power save STAs 649 * The requesting STA may specify traffic characteristics for DMS 650 traffic 651 * DMS was defined in IEEE Std 802.11v-2011 652 * DMS requires changes to both AP and STA implementation. 654 DMS is not currently implemented in products. See [Tramarin2017] and 655 [Oliva2013] for more information. 657 4.6.4. Automatic Multicast Tunneling (AMT) 659 AMT[RFC7450] provides a method to tunnel multicast IP packets inside 660 unicast IP packets over network links that only support unicast. 661 When an operating system or application running on an STA has an AMT 662 gateway capability integrated, it's possible to use unicast to 663 traverse the Wi-Fi link by deploying an AMT relay in the non-Wi-Fi 664 portion of the network connected to the AP. 666 It is recommended that multicast-enabled networks deploying AMT 667 relays for this purpose make the relays locally discoverable with the 668 following methods, as described in 669 [I-D.ietf-mboned-driad-amt-discovery]: 671 * DNS-SD [RFC6763] 672 * the well-known IP addresses from Section 7 of [RFC7450] 674 An AMT gateway that implements multiple standard discovery methods is 675 more likely to discover the local multicast-capable network, instead 676 of forming a connection to a non-local AMT relay further upstream. 678 4.7. GroupCast with Retries (GCR) 680 GCR (defined in [dot11aa]) provides greater reliability by using 681 either unsolicited retries or a block acknowledgement mechanism. GCR 682 increases probability of broadcast frame reception success, but still 683 does not guarantee success. 685 For the block acknowledgement mechanism, the AP transmits each group 686 addressed frame as conventional group addressed transmission. 687 Retransmissions are group addressed, but hidden from non-11aa STAs. 688 A directed block acknowledgement scheme is used to harvest reception 689 status from receivers; retransmissions are based upon these 690 responses. 692 GCR is suitable for all group sizes including medium to large groups. 693 As the number of devices in the group increases, GCR can send block 694 acknowledgement requests to only a small subset of the group. GCR 695 does require changes to both AP and STA implementations. 697 GCR may introduce unacceptable latency. After sending a group of 698 data frames to the group, the AP has to do the following: 700 * unicast a Block Ack Request (BAR) to a subset of members. 701 * wait for the corresponding Block Ack (BA). 702 * retransmit any missed frames. 703 * resume other operations that may have been delayed. 705 This latency may not be acceptable for some traffic. 707 There are ongoing extensions in 802.11 to improve GCR performance. 709 * BAR is sent using downlink MU-MIMO (note that downlink MU-MIMO is 710 already specified in 802.11-REVmc 4.3). 711 * BA is sent using uplink MU-MIMO (which is a .11ax feature). 712 * Additional 802.11ax extensions are under consideration; see 713 [mc-ack-mux] 714 * Latency may also be reduced by simultaneously receiving BA 715 information from multiple STAs. 717 5. Operational optimizations 719 This section lists some operational optimizations that can be 720 implemented when deploying wireless IEEE 802 networks to mitigate 721 some of the issues discussed in Section 3. 723 5.1. Mitigating Problems from Spurious Neighbor Discovery 725 ARP Sponges 726 An ARP Sponge sits on a network and learns which IP addresses 727 are actually in use. It also listens for ARP requests, and, if 728 it sees an ARP for an IP address that it believes is not used, 729 it will reply with its own MAC address. This means that the 730 router now has an IP to MAC mapping, which it caches. If that 731 IP is later assigned to a machine (e.g using DHCP), the ARP 732 sponge will see this, and will stop replying for that address. 733 Gratuitous ARPs (or the machine ARPing for its gateway) will 734 replace the sponged address in the router ARP table. This 735 technique is quite effective; but, unfortunately, the ARP 736 sponge daemons were not really designed for this use (one of 737 the most widely deployed arp sponges [arpsponge], was designed 738 to deal with the disappearance of participants from an IXP) and 739 so are not optimized for this purpose. One daemon is needed 740 per subnet, the tuning is tricky (the scanning rate versus the 741 population rate versus retires, etc.) and sometimes daemons 742 just stop, requiring a restart of the daemon which causes 743 disruption. 744 Router mitigations 745 Some routers (often those based on Linux) implement a "negative 746 ARP cache" daemon. If the router does not see a reply to an 747 ARP it can be configured to cache this information for some 748 interval. Unfortunately, the core routers in use often do not 749 support this. Instead, when a host connects to a network and 750 gets an IP address, it will ARP for its default gateway (the 751 router). The router will update its cache with the IP to host 752 MAC mapping learned from the request (passive ARP learning). 753 Firewall unused space 754 The distribution of users on wireless networks / subnets may 755 change in various use cases, such as conference venues (e.g 756 SSIDs are renamed, some SSIDs lose favor, etc). This makes 757 utilization for particular SSIDs difficult to predict ahead of 758 time, but usage can be monitored as attendees use the different 759 networks. Configuring multiple DHCP pools per subnet, and 760 enabling them sequentially, can create a large subnet, from 761 which only addresses in the lower portions are assigned. 762 Therefore input IP access lists can be applied, which deny 763 traffic to the upper, unused portions. Then the router does 764 not attempt to forward packets to the unused portions of the 765 subnets, and so does not ARP for it. This method has proven to 766 be very effective, but is somewhat of a blunt axe, is fairly 767 labor intensive, and requires coordination. 768 Disabling/filtering ARP requests 769 In general, the router does not need to ARP for hosts; when a 770 host connects, the router can learn the IP to MAC mapping from 771 the ARP request sent by that host. Consequently it should be 772 possible to disable and / or filter ARP requests from the 773 router. Unfortunately, ARP is a very low level / fundamental 774 part of the IP stack, and is often offloaded from the normal 775 control plane. While many routers can filter layer-2 traffic, 776 this is usually implemented as an input filter and / or has 777 limited ability to filter output broadcast traffic. This means 778 that the simple "just disable ARP or filter it outbound" seems 779 like a really simple (and obvious) solution, but 780 implementations / architectural issues make this difficult or 781 awkward in practice. 782 NAT 783 Broadcasts can often be caused by outside wifi scanning / 784 backscatter traffic. In order to reduce the impact of 785 broadcasts, NAT can be used on the entire (or a large portion) 786 of a network. This would eliminate NAT translation entries for 787 unused addresses, and the router would never ARP for them. 788 There are, however, many reasons to avoid using NAT in such a 789 blanket fashion. 790 Stateful firewalls 791 Another obvious solution would be to put a stateful firewall 792 between the wireless network and the Internet. This firewall 793 would block incoming traffic not associated with an outbound 794 request. But this conflicts with the need and desire of some 795 organizations to have the network as open as possible and to 796 honor the end-to-end principle. An attendee on a meeting 797 network should be an Internet host, and should be able to 798 receive unsolicited requests. Unfortunately, keeping the 799 network working and stable is the first priority and a stateful 800 firewall may be required in order to achieve this. 802 5.2. Mitigating Spurious Service Discovery Messages 804 In networks that must support hundreds of STAs, operators have 805 observed network degradation due to many devices simultaneously 806 registering with mDNS. In a network with many clients, it is 807 recommended to ensure that mDNS packets designed to discover services 808 in smaller home networks be constrained to avoid disrupting other 809 traffic. 811 6. Multicast Considerations for Other Wireless Media 813 Many of the causes of performance degradation described in earlier 814 sections are also observable for wireless media other than 802.11. 816 For instance, problems with power save, excess media occupancy, and 817 poor reliability will also affect 802.15.3 and 802.15.4. 818 Unfortunately, 802.15 media specifications do not yet include 819 mechanisms similar to those developed for 802.11. In fact, the 820 design philosophy for 802.15 is oriented towards minimality, with the 821 result that many such functions are relegated to operation within 822 higher layer protocols. This leads to a patchwork of non- 823 interoperable and vendor-specific solutions. See [uli] for some 824 additional discussion, and a proposal for a task group to resolve 825 similar issues, in which the multicast problems might be considered 826 for mitigation. 828 Similar considerations hold for most other wireless media. A brief 829 introduction is provided in [RFC5757] for the following: 831 * 802.16 WIMAX 832 * 3GPP/3GPP2 833 * DVB-H / DVB-IPDC 834 * TV Broadcast and Satellite Networks 836 7. Recommendations 838 This section provides some recommendations about the usage and 839 combinations of some of the multicast enhancements described in 840 Section 4 and Section 5. 842 Future protocol documents utilizing multicast signaling should be 843 carefully scrutinized if the protocol is likely to be used over 844 wireless media. 846 The use of proxy methods should be encouraged to conserve network 847 bandwidth and power utilization by low-power devices. The device can 848 use a unicast message to its proxy, and then the proxy can take care 849 of any needed multicast operations. 851 Multicast signaling for wireless devices should be done in a way 852 compatible with low duty-cycle operation. 854 8. On-going Discussion Items 856 This section suggests two discussion items for further resolution. 858 First, standards (and private) organizations should develop 859 guidelines to help clarify when multicast packets would be better 860 served by being sent wired rather than wireless. For example, 861 802.1ak (https://www.ieee802.org/1/pages/802.1ak.html) works on both 862 ethernet and Wi-Fi and organizations could help with deployment 863 decision making by developing guidelines for multicast over Wi-Fi 864 including options for when traffic should be sent wired. 866 Second, reliable registration to Layer-2 multicast groups, and a 867 reliable multicast operation at Layer-2, might provide a good 868 multicast over wifi solution. There shouldn't be a need to support 869 2^24 groups to get solicited node multicast working: it is possible 870 to simply select a number of bits that make sense for a given network 871 size to limit the number of unwanted deliveries to reasonable levels. 872 IEEE 802.1, 802.11, and 802.15 should be encouraged to revisit L2 873 multicast issues and provide workable solutions. 875 9. Security Considerations 877 This document does not introduce or modify any security mechanisms. 878 Multicast deployed on wired or wireless networks as discussed in this 879 document can be made more secure in a variety of ways. [RFC4601], 880 for instance, specifies the use of IPsec to ensure authentication of 881 the link-local messages in the Protocol Independent Multicast - 882 Sparse Mode (PIM-SM) routing protocol. [RFC5796]specifies mechanisms 883 to authenticate the PIM-SM link-local messages using the IP security 884 (IPsec) Encapsulating Security Payload (ESP) or (optionally) the 885 Authentication Header (AH). 887 When using mechanisms that convert multicast traffic to unicast 888 traffic for traversing radio links, the AP (or other entity) is 889 forced to explicitly track which subscribers care about certain 890 multicast traffic. This is generally a reasonable tradeoff, but does 891 result in another entity that is tracking what entities subscribe to 892 which multicast traffic. While such information is already (by 893 necessity) tracked elsewhere, this does present an expansion of the 894 attack surface for that potentially privacy-sensitive information. 896 As noted in [group_key], the unreliable nature of multicast 897 transmission over wireless media can cause subtle problems with 898 multicast group key management and updates. When WPA (TKIP) or WPA2 899 (AES-CCMP) encryption is in use, AP to client (From DS) multicasts 900 have to be encrypted with a separate encryption key that is known to 901 all of the clients (this is called the Group Key). Quoting further 902 from that website, "... most clients are able to get connected and 903 surf the web, check email, etc. even when From DS multicasts are 904 broken. So a lot of people don't realize they have multicast 905 problems on their network..." 907 This document encourages the use of proxy methods to conserve network 908 bandwidth and power utilization by low-power devices. Such proxy 909 methods in general have security considerations that require the 910 proxy to be trusted to not misbehave. One such proxy method listed 911 is an Arp Sponge which listens for ARP requests, and, if it sees an 912 ARP for an IP address that it believes is not used, it will reply 913 with its own MAC address. ARP poisoning and false advertising could 914 potentially undermine (e.g. DoS) this, and other, proxy approaches. 916 10. IANA Considerations 918 This document does not request any IANA actions. 920 11. Acknowledgements 922 This document has benefitted from discussions with the following 923 people, in alphabetical order: Mikael Abrahamsson, Bill Atwood, 924 Stuart Cheshire, Donald Eastlake, Toerless Eckert, Jake Holland, Joel 925 Jaeggli, Jan Komissar, David Lamparter, Morten Pedersen, Pascal 926 Thubert, Jeffrey (Zhaohui) Zhang 928 12. Informative References 930 [arpsponge] 931 Wessel, M. and N. Sijm, "Effects of IPv4 and IPv6 address 932 resolution on AMS-IX and the ARP Sponge", July 2009, 933 . 936 [bridge-mc-2-uc] 937 Fietkau, F., "bridge: multicast to unicast", January 2017, 938 . 941 [CAB] Fietkau, F., "Limit multicast buffer hardware queue 942 depth", 2013, 943 . 945 [Deri-2010] 946 Deri, L. and J. Gasparakis, "10 Gbit Hardware Packet 947 Filtering Using Commodity Network Adapters", RIPE 61, 948 2010, . 951 [dot11] "IEEE 802 Wireless", "802.11-2016 - IEEE Standard for 952 Information technology--Telecommunications and information 953 exchange between systems Local and metropolitan area 954 networks--Specific requirements - Part 11: Wireless LAN 955 Medium Access Control (MAC) and Physical Layer (PHY) 956 Specification (includes 802.11v amendment)", March 2016, 957 . 960 [dot11-proxyarp] 961 Hiertz, G. R., Mestanov, F., and B. Hart, "Proxy ARP in 962 802.11ax", September 2015, 963 . 966 [dot11aa] "IEEE 802 Wireless", "Part 11: Wireless LAN Medium Access 967 Control (MAC) and Physical Layer (PHY) Specifications 968 Amendment 2: MAC Enhancements for Robust Audio Video 969 Streaming", March 2012, 970 . 972 [group_key] 973 Spiff, "Why do some WiFi routers block multicast packets 974 going from wired to wireless?", January 2017, 975 . 979 [I-D.ietf-6lo-backbone-router] 980 Thubert, P., Perkins, C. E., and E. Levy-Abegnoli, "IPv6 981 Backbone Router", Work in Progress, Internet-Draft, draft- 982 ietf-6lo-backbone-router-20, 23 March 2020, 983 . 986 [I-D.ietf-6tisch-architecture] 987 Thubert, P., "An Architecture for IPv6 over the Time- 988 Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)", 989 Work in Progress, Internet-Draft, draft-ietf-6tisch- 990 architecture-30, 26 November 2020, 991 . 994 [I-D.ietf-mboned-driad-amt-discovery] 995 Holland, J., "DNS Reverse IP Automatic Multicast Tunneling 996 (AMT) Discovery", Work in Progress, Internet-Draft, draft- 997 ietf-mboned-driad-amt-discovery-13, 20 December 2019, 998 . 1001 [ietf_802-11] 1002 Stanley, D., "IEEE 802.11 multicast capabilities", 1003 November 2015, . 1007 [mc-ack-mux] 1008 Tanaka, Y., Sakai, E., Morioka, Y., Mori, M., Hiertz, G., 1009 and S. Coffey, "Multiplexing of Acknowledgements for 1010 Multicast Transmission", July 2015, 1011 . 1015 [mc-prob-stmt] 1016 Abrahamsson, M. and A. Stephens, "Multicast on 802.11", 1017 March 2015, . 1020 [mc-props] 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 [RFC0826] Plummer, D., "An Ethernet Address Resolution Protocol: Or 1033 Converting Network Protocol Addresses to 48.bit Ethernet 1034 Address for Transmission on Ethernet Hardware", STD 37, 1035 RFC 826, DOI 10.17487/RFC0826, November 1982, 1036 . 1038 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 1039 RFC 2131, DOI 10.17487/RFC2131, March 1997, 1040 . 1042 [RFC4286] Haberman, B. and J. Martin, "Multicast Router Discovery", 1043 RFC 4286, DOI 10.17487/RFC4286, December 2005, 1044 . 1046 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, 1047 "Considerations for Internet Group Management Protocol 1048 (IGMP) and Multicast Listener Discovery (MLD) Snooping 1049 Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, 1050 . 1052 [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, 1053 "Protocol Independent Multicast - Sparse Mode (PIM-SM): 1054 Protocol Specification (Revised)", RFC 4601, 1055 DOI 10.17487/RFC4601, August 2006, 1056 . 1058 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1059 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1060 DOI 10.17487/RFC4861, September 2007, 1061 . 1063 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1064 Address Autoconfiguration", RFC 4862, 1065 DOI 10.17487/RFC4862, September 2007, 1066 . 1068 [RFC5424] Gerhards, R., "The Syslog Protocol", RFC 5424, 1069 DOI 10.17487/RFC5424, March 2009, 1070 . 1072 [RFC5757] Schmidt, T., Waehlisch, M., and G. Fairhurst, "Multicast 1073 Mobility in Mobile IP Version 6 (MIPv6): Problem Statement 1074 and Brief Survey", RFC 5757, DOI 10.17487/RFC5757, 1075 February 2010, . 1077 [RFC5796] Atwood, W., Islam, S., and M. Siami, "Authentication and 1078 Confidentiality in Protocol Independent Multicast Sparse 1079 Mode (PIM-SM) Link-Local Messages", RFC 5796, 1080 DOI 10.17487/RFC5796, March 2010, 1081 . 1083 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 1084 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 1085 DOI 10.17487/RFC6282, September 2011, 1086 . 1088 [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, 1089 DOI 10.17487/RFC6762, February 2013, 1090 . 1092 [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service 1093 Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013, 1094 . 1096 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 1097 Bormann, "Neighbor Discovery Optimization for IPv6 over 1098 Low-Power Wireless Personal Area Networks (6LoWPANs)", 1099 RFC 6775, DOI 10.17487/RFC6775, November 2012, 1100 . 1102 [RFC6970] Boucadair, M., Penno, R., and D. Wing, "Universal Plug and 1103 Play (UPnP) Internet Gateway Device - Port Control 1104 Protocol Interworking Function (IGD-PCP IWF)", RFC 6970, 1105 DOI 10.17487/RFC6970, July 2013, 1106 . 1108 [RFC7450] Bumgardner, G., "Automatic Multicast Tunneling", RFC 7450, 1109 DOI 10.17487/RFC7450, February 2015, 1110 . 1112 [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I., 1113 Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent 1114 Multicast - Sparse Mode (PIM-SM): Protocol Specification 1115 (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March 1116 2016, . 1118 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 1119 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 1120 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 1121 RFC 8415, DOI 10.17487/RFC8415, November 2018, 1122 . 1124 [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. 1125 Perkins, "Registration Extensions for IPv6 over Low-Power 1126 Wireless Personal Area Network (6LoWPAN) Neighbor 1127 Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, 1128 . 1130 [Tramarin2017] 1131 Tramarin, F., Vitturi, S., and M. Luvisotto, "IEEE 802.11n 1132 for Distributed Measurement Systems", 2017 IEEE 1133 International Instrumentation and Measurement Technology 1134 Conference (I2MTC) pp. 1-6, May 2017. 1136 [uli] Kinney, P., "LLC Proposal for 802.15.4", November 2015, 1137 . 1140 Authors' Addresses 1142 Charles E. Perkins 1143 Blue Meadow Networks 1145 Phone: +1-408-330-4586 1146 Email: charliep@computer.org 1148 Mike McBride 1149 Futurewei Technologies Inc. 1150 2330 Central Expressway 1151 Santa Clara, CA 95055 1152 United States of America 1154 Email: michael.mcbride@futurewei.com 1155 Dorothy Stanley 1156 Hewlett Packard Enterprise 1157 2000 North Naperville Rd. 1158 Naperville, IL 60566 1159 United States of America 1161 Phone: +1 630 979 1572 1162 Email: dstanley1389@gmail.com 1164 Warren Kumari 1165 Google 1166 1600 Amphitheatre Parkway 1167 Mountain View, CA 94043 1168 United States of America 1170 Email: warren@kumari.net 1172 Juan Carlos Zuniga 1173 SIGFOX 1174 425 rue Jean Rostand 1175 31670 Labege 1176 France 1178 Email: j.c.zuniga@ieee.org