--- 1/draft-ietf-mboned-ieee802-mcast-problems-04.txt 2019-04-15 09:13:29.589613207 -0700 +++ 2/draft-ietf-mboned-ieee802-mcast-problems-05.txt 2019-04-15 09:13:29.641614555 -0700 @@ -1,113 +1,119 @@ Internet Area C. Perkins Internet-Draft M. McBride Intended status: Informational Futurewei -Expires: June 1, 2019 D. Stanley +Expires: October 17, 2019 D. Stanley HPE W. Kumari Google JC. Zuniga SIGFOX - November 28, 2018 + April 15, 2019 Multicast Considerations over IEEE 802 Wireless Media - draft-ietf-mboned-ieee802-mcast-problems-04 + draft-ietf-mboned-ieee802-mcast-problems-05 Abstract Well-known issues with multicast have prevented the deployment of - multicast in 802.11 [dot11], [mc-props], [mc-prob-stmt], and other - local-area wireless environments. This document offers guidance on - known limitations and problems with wireless multicast. Also - described are certain multicast enhancement features that have been - specified by the IETF and by IEEE 802 for wireless media, as well as - some operational choices that can be taken to improve the performace - of the network. Finally, some recommendations are provided about the - usage and combination of these features and operational choices. + multicast in 802.11 and other local-area wireless environments. This + document offers guidance on known limitations and problems with + wireless multicast. Also described are certain multicast enhancement + features that have been specified by the IETF and by IEEE 802 for + wireless media, as well as some operational choices that can be taken + to improve the performace of the network. Finally, some + recommendations are provided about the usage and combination of these + features and operational choices. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on June 1, 2019. + This Internet-Draft will expire on October 17, 2019. Copyright Notice - Copyright (c) 2018 IETF Trust and the persons identified as the + Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Identified multicast issues . . . . . . . . . . . . . . . . . 5 3.1. Issues at Layer 2 and Below . . . . . . . . . . . . . . . 5 3.1.1. Multicast reliability . . . . . . . . . . . . . . . . 5 - 3.1.2. Lower and Variable Data Rate . . . . . . . . . . . . 5 + 3.1.2. Lower and Variable Data Rate . . . . . . . . . . . . 6 3.1.3. High Interference . . . . . . . . . . . . . . . . . . 6 3.1.4. Power-save Effects on Multicast . . . . . . . . . . . 7 3.2. Issues at Layer 3 and Above . . . . . . . . . . . . . . . 7 3.2.1. IPv4 issues . . . . . . . . . . . . . . . . . . . . . 8 3.2.2. IPv6 issues . . . . . . . . . . . . . . . . . . . . . 8 3.2.3. MLD issues . . . . . . . . . . . . . . . . . . . . . 8 3.2.4. Spurious Neighbor Discovery . . . . . . . . . . . . . 9 4. Multicast protocol optimizations . . . . . . . . . . . . . . 10 4.1. Proxy ARP in 802.11-2012 . . . . . . . . . . . . . . . . 10 4.2. IPv6 Address Registration and Proxy Neighbor Discovery . 10 4.3. Buffering to Improve Battery Life . . . . . . . . . . . . 12 4.4. IPv6 support in 802.11-2012 . . . . . . . . . . . . . . . 12 - 4.5. Conversion of multicast to unicast . . . . . . . . . . . 13 - 4.6. Directed Multicast Service (DMS) . . . . . . . . . . . . 13 - 4.7. GroupCast with Retries (GCR) . . . . . . . . . . . . . . 13 - 5. Operational optimizations . . . . . . . . . . . . . . . . . . 14 - 5.1. Mitigating Problems from Spurious Neighbor Discovery . . 14 - 6. Multicast Considerations for Other Wireless Media . . . . . . 16 - 7. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 16 - 8. Discussion Items . . . . . . . . . . . . . . . . . . . . . . 17 - 9. Security Considerations . . . . . . . . . . . . . . . . . . . 17 - 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 - 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 - 12. Informative References . . . . . . . . . . . . . . . . . . . 18 - Appendix A. Changes between draft-ietf-mboned-ieee802-mcast- - problems revisions 03 versus 04 . . . . . . . . . . 20 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 + 4.5. Using Unicast Instead of Multicast . . . . . . . . . . . 13 + 4.5.1. Overview . . . . . . . . . . . . . . . . . . . . . . 13 + 4.5.2. Layer 2 Conversion to Unicast . . . . . . . . . . . . 13 + 4.5.3. Directed Multicast Service (DMS) . . . . . . . . . . 13 + 4.5.4. Automatic Multicast Tunneling (AMT) . . . . . . . . . 14 + 4.6. GroupCast with Retries (GCR) . . . . . . . . . . . . . . 14 + 5. Operational optimizations . . . . . . . . . . . . . . . . . . 15 + 5.1. Mitigating Problems from Spurious Neighbor Discovery . . 15 + 5.2. Mitigating Spurious Service Discovery Messages . . . . . 17 + 6. Multicast Considerations for Other Wireless Media . . . . . . 17 + 7. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 18 + 8. Discussion Items . . . . . . . . . . . . . . . . . . . . . . 18 + 9. Security Considerations . . . . . . . . . . . . . . . . . . . 19 + 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 + 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19 + 12. Informative References . . . . . . . . . . . . . . . . . . . 19 + Appendix A. Changes in this draft between revisions 04 versus 05 22 + Appendix B. Changes in this draft between revisions 03 versus 04 23 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 1. Introduction - Performance issues have been observed when multicast packet - transmissions of IETF protocols are used over IEEE 802 wireless - media. Even though enhancements for multicast transmissions have - been designed at both IETF and IEEE 802, incompatibilities still - exist between specifications, implementations and configuration - choices. + Well-known issues with multicast have prevented the deployment of + multicast in 802.11 [dot11], [mc-props], [mc-prob-stmt], and other + local-area wireless environments. Performance issues have been + observed when multicast packet transmissions of IETF protocols are + used over IEEE 802 wireless media. Even though enhancements for + multicast transmissions have been designed at both IETF and IEEE 802, + incompatibilities still exist between specifications, implementations + and configuration choices. Many IETF protocols depend on multicast/broadcast for delivery of control messages to multiple receivers. Multicast is used for various purposes such as neighbor discovery, network flooding, address resolution, as well minimizing media occupancy for the transmission of data that is intended for multiple receivers. In addition to protocol use of broadcast/multicast for control messages, more applications, such as push to talk in hospitals, or video in enterprises, universities, and homes, are sending multicast IP to end user devices, which are increasingly using wifi for their @@ -164,24 +170,24 @@ enhancements. Some advice about the operational choices that can be taken is also included. It is likely that this document will also be considered relevant to designers of future IEEE wireless specifications. 2. Terminology This document uses the following definitions: ACK - IEEE 802.11 Access Point + The 802.11 layer 2 acknowledgement AP - The 802.11 layer 2 acknowledgement + IEEE 802.11 Access Point basic rate The slowest rate of all the connected devices, at which multicast and broadcast traffic is generally transmitted DTIM Delivery Traffic Indication Map (DTIM): An information element that advertises whether or not any associated stations have buffered multicast or broadcast frames @@ -319,33 +325,34 @@ o On-demand routing o Backbone construction o Other L3 protocols (non-IP) User Datagram Protocol (UDP) is the most common transport layer protocol for multicast applications. By itself, UDP is not reliable -- messages may be lost or delivered out of order. 3.2.1. IPv4 issues - The following list contains a few representative IPv4 protocols using - multicast. + The following list contains some representative multicast protocols + that are used with IPv4. o ARP o DHCP - o mDNS + o mDNS [RFC6762] + o uPnP [RFC6970] After initial configuration, ARP and DHCP occur much less commonly, - but service discovery can occur at any time. Apple's Bonjour - protocol, for instance, provides service discovery (for printing) - that utilizes multicast. It's often the first service that operators + but service discovery can occur at any time. Some widely-deployed + service discovery protocols (e.g., for finding a printer) utilize + mDNS (i.e., multicast). It's often the first service that operators drop. Even if multicast snooping is utilized, many devices can - register at once using Bonjour, causing serious network degradation. + register at once and cause serious network degradation. 3.2.2. IPv6 issues IPv6 makes extensive use of multicast, including the following: o DHCPv6 o IPv6 Neighbor Discovery Protocol (NDP) o Duplicate Address Detection (DAD) o Address Resolution o Service Discovery @@ -441,21 +448,21 @@ Here is the specification language as described in clause 10.23.13 of [dot11-proxyarp]: When the AP supports Proxy ARP "[...] the AP shall maintain a Hardware Address to Internet Address mapping for each associated station, and shall update the mapping when the Internet Address of the associated station changes. When the IPv4 address being resolved in the ARP request packet is used by a non-AP STA currently associated to the BSS, the proxy ARP service shall - respond on behalf of the non-AP STA" + respond on behalf of the non-AP STA". 4.2. IPv6 Address Registration and Proxy Neighbor Discovery As used in this section, a Low-Power Wireless Personal Area Network (6LoWPAN) denotes a low power lossy network (LLN) that supports 6LoWPAN Header Compression (HC) [RFC6282]. A 6TiSCH network [I-D.ietf-6tisch-architecture] is an example of a 6LowPAN. In order to control the use of IPv6 multicast over 6LoWPANs, the 6LoWPAN Neighbor Discovery (6LoWPAN ND) [RFC6775] standard defines an address registration mechanism that relies on a central registry to assess @@ -555,46 +562,99 @@ NDP may be used to request additional information o Maximum Transmission Unit o Router Solicitation o Router Advertisement, etc. NDP messages are sent as group addressed (broadcast) frames in 802.11. Using the proxy operation helps to keep NDP messages off the wireless medium. -4.5. Conversion of multicast to unicast +4.5. Using Unicast Instead of Multicast It is often possible to transmit multicast control and data messages by using unicast transmissions to each station individually. -4.6. Directed Multicast Service (DMS) +4.5.1. Overview + + In many situations, it's a good choice to use unicast instead of + multicast over the Wi-Fi link. This avoids most of the problems + specific to multicast over Wi-Fi, since the individual frames are + then acknowledged and buffered for power save clients, in the way + that unicast traffic normally operates. + + This approach comes with the tradeoff of sometimes sending the same + packet multiple times over the Wi-Fi link. However, in many cases, + such as video into a residential home network, this can be a good + tradeoff, since the Wi-Fi link may have enough capacity for the + unicast traffic to be transmitted to each subscribed STA, even though + multicast addressing may have been necessary for the upstream access + network. + + Several technologies exist that can be used to arrange unicast + transport over the Wi-Fi link, outlined in the subsections below. + +4.5.2. Layer 2 Conversion to Unicast + + It is often possible to transmit multicast control and data messages + by using unicast transmissions to each station individually. + + Although there is not yet a standardized method of conversion, at + least one widely available implementation exists in the Linux + bridging code [bridge-mc-2-uc]. Other proprietary implementations + are available from various vendors. In general, these + implementations perform a straightforward mapping for groups or + channels, discovered by IGMP or MLD snooping, to the corresponding + unicast MAC addresses. + +4.5.3. Directed Multicast Service (DMS) There are situations where more is needed than simply converting multicast to unicast. For these purposes, DMS enables a STA to request that the AP transmit multicast group addressed frames destined to the requesting STAs as individually addressed frames [i.e., convert multicast to unicast]. Here are some characteristics of DMS: o Requires 802.11n A-MSDUs o Individually addressed frames are acknowledged and are buffered for power save STAs o The requesting STA may specify traffic characteristics for DMS traffic o DMS was defined in IEEE Std 802.11v-2011 o DMS requires changes to both AP and STA implementation. DMS is not currently implemented in products. See [Tramarin2017] and [Oliva2013] for more information. -4.7. GroupCast with Retries (GCR) +4.5.4. Automatic Multicast Tunneling (AMT) + + AMT[RFC7450] provides a method to tunnel multicast IP packets inside + unicast IP packets over network links that only support unicast. + When an operating system or application running on a STA has an AMT + gateway capability integrated, it's possible to use unicast to + traverse the Wi-Fi link by deploying an AMT relay in the non-Wi-Fi + portion of the network connected to the AP. + + It is RECOMMENDED that multicast-enabled networks deploying AMT + relays for this purpose make the relays discoverable with both of + these methods: + + o the well-known IP addresses from Section 7 of [RFC7450], and + o with DNS-SD [RFC6763] + + Providing the multiple standard discovery methods makes it more + likely that AMT gateway implementations will discover the local + multicast-capable network, rather than forming a connection to an AMT + relay further upstream. + +4.6. GroupCast with Retries (GCR) GCR (defined in [dot11aa]) provides greater reliability by using either unsolicited retries or a block acknowledgement mechanism. GCR increases probability of broadcast frame reception success, but still does not guarantee success. For the block acknowledgement mechanism, the AP transmits each group addressed frame as conventional group addressed transmission. Retransmissions are group addressed, but hidden from non-11aa STAs. A directed block acknowledgement scheme is used to harvest reception @@ -708,27 +768,36 @@ there would be no NAT translation entries for unused addresses, and so the router would never ARP for them. However, there are many reasons to avoid using NAT in such a blanket fashion. Stateful firewalls Another obvious solution would be to put a stateful firewall between the wireless network and the Internet. This firewall would block incoming traffic not associated with an outbound request. But this conflicts with the need and desire to have - the network as open as possible / honor the end-to-end + the network as open as possible and to honor the end-to-end principle. An attendee on the meeting network should be an Internet host, and should be able to receive unsolicited requests. Unfortunately, keeping the network working and stable is the first priority and a stateful firewall may be required in order to achieve this. +5.2. Mitigating Spurious Service Discovery Messages + + In networks that must support hundreds of STAs, operators have + observed network degradation due to many devices simultaneously + registering with mDNS. In a network with many clients, it is + recommended to ensure that mDNS packets designed to discover + services in smaller home networks be constrained to avoid + disrupting other traffic. + 6. Multicast Considerations for Other Wireless Media Many of the causes of performance degradation described in earlier sections are also observable for wireless media other than 802.11. For instance, problems with power save, excess media occupancy, and poor reliability will also affect 802.15.3 and 802.15.4. Unfortunately, 802.15 media specifications do not yet include mechanisms similar to those developed for 802.11. In fact, the design philosophy for 802.15 is oriented towards minimality, with the @@ -756,23 +825,21 @@ Future protocol documents utilizing multicast signaling should be carefully scrutinized if the protocol is likely to be used over wireless media. Proxy methods should be encouraged to conserve network bandwidth and power utilization by low-power devices. The device can use a unicast message to its proxy, and then the proxy can take care of any needed multicast operations. Multicast signaling for wireless devices should be done in a way - compatible with low-duty cycle operation. - - (FFS) + compatible with low duty-cycle operation. 8. Discussion Items This section suggests two discussion items for further resolution. The IETF should determine guidelines by which it may be decided that multicast packets are to be sent wired. For example, 802.1ak works on ethernet and Wi-Fi. 802.1ak has been pulled into 802.1Q as of 802.1Q-2011. 802.1Q-2014 can be found here: http://www.ieee802.org/1/pages/802.1Q-2014.html. If a generic @@ -787,85 +854,108 @@ amount of unwanted deliveries to reasonable levels. IEEE 802.1, 802.11, and 802.15 should be encouraged to revisit L2 multicast issues. In reality, Wi-Fi provides a broadcast service, not a multicast service. On the physical medium, all frames are broadcast except in very unusual cases in which special beamforming transmitters are used. Unicast offers the advantage of being much faster (2 orders of magnitude) and much more reliable (L2 ARQ). 9. Security Considerations - This document does not introduce any security mechanisms, and does - not have affect existing security mechanisms. + This document neither introduces nor modifies any security + mechanisms. 10. IANA Considerations This document does not request any IANA actions. 11. Acknowledgements This document has benefitted from discussions with the following people, in alphabetical order: Mikael Abrahamsson, Stuart Cheshire, - Donald Eastlake, Toerless Eckert, Jake Holland, Joel Jaeggli, Pascal - Thubert + Donald Eastlake, Toerless Eckert, Jake Holland, Joel Jaeggli, Jan + Komissar, David Lamparter, Pascal Thubert 12. Informative References [arpsponge] - Arien Vijn, Steven Bakker, "Arp Sponge", March 2015. + Vijn, A. and S. Bakker, "Arp Sponge", March 2015, + . + + [bridge-mc-2-uc] + Torvalds, L., "bridge: multicast to unicast", Jan 2017, + . [Deri-2010] Deri, L. and J. Gasparakis, "10 Gbit Hardware Packet Filtering Using Commodity Network Adapters", RIPE 61, 2010, . - [dot11] P802.11, "802.11-2016 - IEEE Standard for Information - technology--Telecommunications and information exchange - between systems Local and metropolitan area networks-- - Specific requirements - Part 11: Wireless LAN Medium - Access Control (MAC) and Physical Layer (PHY) - Specification", March 2016. + [dot11] "IEEE 802 Wireless", "802.11-2016 - IEEE Standard for + Information technology--Telecommunications and information + exchange between systems Local and metropolitan area + networks--Specific requirements - Part 11: Wireless LAN + Medium Access Control (MAC) and Physical Layer (PHY) + Specification", March 2016, + . [dot11-proxyarp] - P802.11, "Proxy ARP in 802.11ax", September 2015. + "IEEE 802 Wireless P802.11", "IEEE 802 Wireless P802.11", + and "IEEE 802 Wireless P802.11", "Proxy ARP in 802.11ax", + September 2015, . - [dot11aa] P802.11, "Part 11: Wireless LAN Medium Access Control - (MAC) and Physical Layer (PHY) Specifications Amendment 2: - MAC Enhancements for Robust Audio Video Streaming", March - 2012. + [dot11aa] "IEEE 802 Wireless", "Part 11: Wireless LAN Medium Access + Control (MAC) and Physical Layer (PHY) Specifications + Amendment 2: MAC Enhancements for Robust Audio Video + Streaming", March 2012, + . [I-D.ietf-6lo-backbone-router] - Thubert, P. and C. Perkins, "IPv6 Backbone Router", draft- - ietf-6lo-backbone-router-08 (work in progress), October - 2018. + Thubert, P., Perkins, C., and E. Levy-Abegnoli, "IPv6 + Backbone Router", draft-ietf-6lo-backbone-router-11 (work + in progress), February 2019. [I-D.ietf-6tisch-architecture] Thubert, P., "An Architecture for IPv6 over the TSCH mode - of IEEE 802.15.4", draft-ietf-6tisch-architecture-17 (work - in progress), November 2018. + of IEEE 802.15.4", draft-ietf-6tisch-architecture-20 (work + in progress), March 2019. [ietf_802-11] - Dorothy Stanley, "IEEE 802.11 multicast capabilities", Nov - 2015. + Stanley, D., "IEEE 802.11 multicast capabilities", Nov + 2015, . [mc-ack-mux] - Yusuke Tanaka et al., "Multiplexing of Acknowledgements - for Multicast Transmission", July 2015. + Tanaka, Y., Sakai, E., Morioka, Y., Mori, M., Hiertz, G., + and S. Coffey, "Multiplexing of Acknowledgements for + Multicast Transmission", July 2015, + . [mc-prob-stmt] - Mikael Abrahamsson and Adrian Stephens, "Multicast on - 802.11", March 2015. + Abrahamsson, M. and A. Stephens, "Multicast on 802.11", + March 2015, . [mc-props] - Adrian Stephens, "IEEE 802.11 multicast properties", March - 2015. + Stephens, A., "IEEE 802.11 multicast properties", March + 2015, . [Oliva2013] de la Oliva, A., Serrano, P., Salvador, P., and A. Banchs, "Performance evaluation of the IEEE 802.11aa multicast mechanisms for video streaming", 2013 IEEE 14th International Symposium on "A World of Wireless, Mobile and Multimedia Networks" (WoWMoM) pp. 1-9, June 2013. [RFC4541] Christensen, M., Kimball, K., and F. Solensky, "Considerations for Internet Group Management Protocol @@ -886,52 +976,91 @@ [RFC5757] Schmidt, T., Waehlisch, M., and G. Fairhurst, "Multicast Mobility in Mobile IP Version 6 (MIPv6): Problem Statement and Brief Survey", RFC 5757, DOI 10.17487/RFC5757, February 2010, . [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, DOI 10.17487/RFC6282, September 2011, . + [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, + DOI 10.17487/RFC6762, February 2013, + . + + [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service + Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013, + . + [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. Bormann, "Neighbor Discovery Optimization for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)", RFC 6775, DOI 10.17487/RFC6775, November 2012, . + [RFC6970] Boucadair, M., Penno, R., and D. Wing, "Universal Plug and + Play (UPnP) Internet Gateway Device - Port Control + Protocol Interworking Function (IGD-PCP IWF)", RFC 6970, + DOI 10.17487/RFC6970, July 2013, + . + + [RFC7450] Bumgardner, G., "Automatic Multicast Tunneling", RFC 7450, + DOI 10.17487/RFC7450, February 2015, + . + [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. Perkins, "Registration Extensions for IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Neighbor Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, . [Tramarin2017] Tramarin, F., Vitturi, S., and M. Luvisotto, "IEEE 802.11n for Distributed Measurement Systems", 2017 IEEE International Instrumentation and Measurement Technology Conference (I2MTC) pp. 1-6, May 2017. - [uli] Pat Kinney, "LLC Proposal for 802.15.4", Nov 2015. + [uli] Kinney, P., "LLC Proposal for 802.15.4", Nov 2015, + . -Appendix A. Changes between draft-ietf-mboned-ieee802-mcast-problems - revisions 03 versus 04 +Appendix A. Changes in this draft between revisions 04 versus 05 + + This section lists the changes between revisions ...-04.txt and + ...-05.txt of draft-ietf-mboned-ieee802-mcast-problems. + + o Incorporated text from Jake Holland for a new section about + conversion of multicast to unicast and included AMT as an existing + solution. + o Included some text about likely future multicast applications that + will emphasize the need for attention to the technical matters + collected in this document. + o Further modified text to be more generic instead of referring + specifically to IETF conference situations. + o Modified text to be more generic instead of referring specifically + to Bonjour. + o Added uPnP as a representative multicast protocol in IP networks. + o Referred to Linux bridging code for multicast to unicast. + o Updated bibliographic citations, included URLs as needed. + o More editorial improvements and grammatical corrections. + +Appendix B. Changes in this draft between revisions 03 versus 04 This section lists the changes between revisions ...-03.txt and ...-04.txt of draft-ietf-mboned-ieee802-mcast-problems. o Replaced "client" by "STA". o Used terminology "Wi-Fi" throughout. o Many editorial improvements and grammatical corrections. o Modified text to be more generic instead of referring specifically to IETF conference situations. - o Cited RFC 5757 [RFC5757] for introduction to other wireless media. + o Cited [RFC5757] for introduction to other wireless media. o Updated bibliographic citations. Authors' Addresses Charles E. Perkins Futurewei Inc. 2330 Central Expressway Santa Clara, CA 95050 USA