draft-ietf-mboned-ieee802-mcast-problems-15.txt   rfc9119.txt 
Internet Area C.E. Perkins Internet Engineering Task Force (IETF) C. Perkins
Internet-Draft Blue Meadow Networks Request for Comments: 9119 Lupin Lodge
Intended status: Informational M. McBride Category: Informational M. McBride
Expires: 29 January 2022 Futurewei ISSN: 2070-1721 Futurewei
D. Stanley D. Stanley
HPE HPE
W. Kumari W. Kumari
Google Google
JC. Zuniga JC. Zúñiga
SIGFOX SIGFOX
28 July 2021 October 2021
Multicast Considerations over IEEE 802 Wireless Media Multicast Considerations over IEEE 802 Wireless Media
draft-ietf-mboned-ieee802-mcast-problems-15
Abstract Abstract
Well-known issues with multicast have prevented the deployment of Well-known issues with multicast have prevented the deployment of
multicast in 802.11 (wifi) and other local-area wireless multicast in 802.11 (Wi-Fi) and other local-area wireless
environments. This document describes the known limitations of environments. This document describes the known limitations of
wireless (primarily 802.11) Layer-2 multicast. Also described are wireless (primarily 802.11) Layer 2 multicast. Also described are
certain multicast enhancement features that have been specified by certain multicast enhancement features that have been specified by
the IETF, and by IEEE 802, for wireless media, as well as some the IETF and by IEEE 802 for wireless media, as well as some
operational choices that can be taken to improve the performance of operational choices that can be made to improve the performance of
the network. Finally, some recommendations are provided about the the network. Finally, some recommendations are provided about the
usage and combination of these features and operational choices. usage and combination of these features and operational choices.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This document is not an Internet Standards Track specification; it is
provisions of BCP 78 and BCP 79. published for informational purposes.
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 This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
This Internet-Draft will expire on 29 January 2022. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9119.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology
3. Identified multicast issues . . . . . . . . . . . . . . . . . 5 3. Identified Multicast Issues
3.1. Issues at Layer 2 and Below . . . . . . . . . . . . . . . 5 3.1. Issues at Layer 2 and Below
3.1.1. Multicast reliability . . . . . . . . . . . . . . . . 5 3.1.1. Multicast Reliability
3.1.2. Lower and Variable Data Rate . . . . . . . . . . . . 6 3.1.2. Lower and Variable Data Rate
3.1.3. Capacity and Impact on Interference . . . . . . . . . 7 3.1.3. Capacity and Impact on Interference
3.1.4. Power-save Effects on Multicast . . . . . . . . . . . 7 3.1.4. Power-Save Effects on Multicast
3.2. Issues at Layer 3 and Above . . . . . . . . . . . . . . . 7 3.2. Issues at Layer 3 and Above
3.2.1. IPv4 issues . . . . . . . . . . . . . . . . . . . . . 8 3.2.1. IPv4 Issues
3.2.2. IPv6 issues . . . . . . . . . . . . . . . . . . . . . 8 3.2.2. IPv6 Issues
3.2.3. MLD issues . . . . . . . . . . . . . . . . . . . . . 9 3.2.3. MLD Issues
3.2.4. Spurious Neighbor Discovery . . . . . . . . . . . . . 9 3.2.4. Spurious Neighbor Discovery
4. Multicast protocol optimizations . . . . . . . . . . . . . . 10 4. Multicast Protocol Optimizations
4.1. Proxy ARP in 802.11-2012 . . . . . . . . . . . . . . . . 10 4.1. Proxy ARP in 802.11-2012
4.2. IPv6 Address Registration and Proxy Neighbor Discovery . 11 4.2. IPv6 Address Registration and Proxy Neighbor Discovery
4.3. Buffering to Improve Battery Life . . . . . . . . . . . . 12 4.3. Buffering to Improve Battery Life
4.4. Limiting multicast buffer hardware queue depth . . . . . 13 4.4. Limiting Multicast Buffer Hardware Queue Depth
4.5. IPv6 support in 802.11-2012 . . . . . . . . . . . . . . . 13 4.5. IPv6 Support in 802.11-2012
4.6. Using Unicast Instead of Multicast . . . . . . . . . . . 14 4.6. Using Unicast Instead of Multicast
4.6.1. Overview . . . . . . . . . . . . . . . . . . . . . . 14 4.6.1. Overview
4.6.2. Layer 2 Conversion to Unicast . . . . . . . . . . . . 14 4.6.2. Layer 2 Conversion to Unicast
4.6.3. Directed Multicast Service (DMS) . . . . . . . . . . 14 4.6.3. Directed Multicast Service (DMS)
4.6.4. Automatic Multicast Tunneling (AMT) . . . . . . . . . 15 4.6.4. Automatic Multicast Tunneling (AMT)
4.7. GroupCast with Retries (GCR) . . . . . . . . . . . . . . 15 4.7. GroupCast with Retries (GCR)
5. Operational optimizations . . . . . . . . . . . . . . . . . . 16 5. Operational Optimizations
5.1. Mitigating Problems from Spurious Neighbor Discovery . . 16 5.1. Mitigating Problems from Spurious Neighbor Discovery
5.2. Mitigating Spurious Service Discovery Messages . . . . . 18 5.2. Mitigating Spurious Service Discovery Messages
6. Multicast Considerations for Other Wireless Media . . . . . . 18 6. Multicast Considerations for Other Wireless Media
7. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 19 7. Recommendations
8. On-going Discussion Items . . . . . . . . . . . . . . . . . . 19 8. Ongoing Discussion Items
9. Security Considerations . . . . . . . . . . . . . . . . . . . 20 9. Security Considerations
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 10. IANA Considerations
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21 11. Informative References
12. Informative References . . . . . . . . . . . . . . . . . . . 21 Acknowledgements
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 Authors' Addresses
1. Introduction 1. Introduction
Well-known issues with multicast have prevented the deployment of Well-known issues with multicast have prevented the deployment of
multicast in 802.11 [dot11] and other local-area wireless multicast in 802.11 [dot11] and other local-area wireless
environments, as described in [mc-props], [mc-prob-stmt]. environments, as described in [mc-props] and [mc-prob-stmt].
Performance issues have been observed when multicast packet Performance issues have been observed when multicast packet
transmissions of IETF protocols are used over IEEE 802 wireless transmissions of IETF protocols are used over IEEE 802 wireless
media. Even though enhancements for multicast transmissions have media. Even though enhancements for multicast transmissions have
been designed at both IETF and IEEE 802, incompatibilities still been designed at both IETF and IEEE 802, incompatibilities still
exist between specifications, implementations and configuration exist between specifications, implementations, and configuration
choices. choices.
Many IETF protocols depend on multicast/broadcast for delivery of Many IETF protocols depend on multicast/broadcast for delivery of
control messages to multiple receivers. Multicast allows sending control messages to multiple receivers. Multicast allows data to be
data to multiple interested recipients without the source needing to sent to multiple interested recipients without the source needing to
send duplicate data to each recipient. With broadcast traffic, data send duplicate data to each recipient. With broadcast traffic, data
is sent to every device regardless of their expressed interest in the is sent to every device regardless of their expressed interest in the
data. Multicast is used for various purposes such as neighbor data. Multicast is used for various purposes such as Neighbor
discovery, network flooding, address resolution, as well minimizing Discovery, network flooding, and address resolution, as well as
media occupancy for the transmission of data that is intended for minimizing media occupancy for the transmission of data that is
multiple receivers. In addition to protocol use of broadcast/ intended for multiple receivers. In addition to protocol use of
multicast for control messages, more applications, such as push to broadcast/multicast for control messages, more applications, such as
talk in hospitals, or video in enterprises, universities, and homes, Push To Talk in hospitals or video in enterprises, universities, and
are sending multicast IP to end user devices, which are increasingly homes, are sending multicast IP to end-user devices, which are
using Wi-Fi for their connectivity. increasingly using Wi-Fi for their connectivity.
IETF protocols typically rely on network protocol layering in order IETF protocols typically rely on network protocol layering in order
to reduce or eliminate any dependence of higher level protocols on to reduce or eliminate any dependence of higher-level protocols on
the specific nature of the MAC layer protocols or the physical media. the specific nature of the MAC-layer protocols or the physical media.
In the case of multicast transmissions, higher level protocols have In the case of multicast transmissions, higher-level protocols have
traditionally been designed as if transmitting a packet to an IP traditionally been designed as if transmitting a packet to an IP
address had the same cost in interference and network media access, address had the same cost in interference and network media access,
regardless of whether the destination IP address is a unicast address regardless of whether the destination IP address is a unicast address
or a multicast or broadcast address. This model was reasonable for or a multicast or broadcast address. This model was reasonable for
networks where the physical medium was wired, like Ethernet. networks where the physical medium was wired, like Ethernet.
Unfortunately, for many wireless media, the costs to access the Unfortunately, for many wireless media, the costs to access the
medium can be quite different. Multicast over Wi-Fi has often been medium can be quite different. Multicast over Wi-Fi has often been
plagued by such poor performance that it is disallowed. Some plagued by such poor performance that it is disallowed. Some
enhancements have been designed in IETF protocols that are assumed to enhancements have been designed in IETF protocols that are assumed to
work primarily over wireless media. However, these enhancements are work primarily over wireless media. However, these enhancements are
usually implemented in limited deployments and not widespread on most usually implemented in limited deployments and are not widespread on
wireless networks. most wireless networks.
IEEE 802 wireless protocols have been designed with certain features IEEE 802 wireless protocols have been designed with certain features
to support multicast traffic. For instance, lower modulations are to support multicast traffic. For instance, lower modulations are
used to transmit multicast frames, so that these can be received by used to transmit multicast frames so that these can be received by
all stations in the cell, regardless of the distance or path all stations in the cell, regardless of the distance or path
attenuation from the base station or access point. However, these attenuation from the base station or Access Point (AP). However,
lower modulation transmissions occupy the medium longer; they hamper these lower modulation transmissions occupy the medium longer; they
efficient transmission of traffic using higher order modulations to hamper efficient transmission of traffic using higher-order
nearby stations. For these and other reasons, IEEE 802 working modulations to nearby stations. For these and other reasons, IEEE
groups such as 802.11 have designed features to improve the 802 Working Groups such as 802.11 have designed features to improve
performance of multicast transmissions at Layer 2 [ietf_802-11]. In the performance of multicast transmissions at Layer 2 [ietf_802-11].
addition to protocol design features, certain operational and In addition to protocol design features, certain operational and
configuration enhancements can ameliorate the network performance configuration enhancements can ameliorate the network performance
issues created by multicast traffic, as described in Section 5. issues created by multicast traffic, as described in Section 5.
There seems to be general agreement that these problems will not be There seems to be general agreement that these problems will not be
fixed anytime soon, primarily because it's expensive to do so and due fixed anytime soon, primarily because it's expensive to do so and
to multicast being unreliable. Compared to unicast over Wi-Fi, because of the unreliability of multicast. Compared to unicast over
multicast is often treated as somewhat of a second class citizen, Wi-Fi, multicast is often treated as somewhat of a second-class
even though there are many protocols using multicast. Something citizen even though there are many protocols using multicast.
needs to be provided in order to make them more reliable. IPv6 Something needs to be provided in order to make them more reliable.
neighbor discovery saturating the Wi-Fi link is only part of the IPv6 Neighbor Discovery saturating the Wi-Fi link is only part of the
problem. Wi-Fi traffic classes may help. This document is intended problem. Wi-Fi traffic classes may help. This document is intended
to help make the determination about what problems should be solved to help make the determination about what problems should be solved
by the IETF and what problems should be solved by the IEEE (see by the IETF and what problems should be solved by the IEEE (see
Section 8). Section 8).
This document details various problems caused by multicast This document details various problems caused by multicast
transmission over wireless networks, including high packet error transmission over wireless networks, including high packet error
rates, no acknowledgements, and low data rate. It also explains some rates, no acknowledgements, and low data rate. It also explains some
enhancements that have been designed at the IETF and IEEE 802.11 to enhancements that have been designed at the IETF and IEEE 802.11 to
ameliorate the effects of the radio medium on multicast traffic. ameliorate the effects of the radio medium on multicast traffic.
Recommendations are also provided to implementors about how to use Recommendations are also provided to implementors about how to use
and combine these enhancements. Some advice about the operational and combine these enhancements. Some advice about the operational
choices that can be taken is also included. It is likely that this choices that can be made is also included. It is likely that this
document will also be considered relevant to designers of future IEEE document will also be considered relevant to designers of future IEEE
wireless specifications. wireless specifications.
2. Terminology 2. Terminology
This document uses the following definitions: This document uses the following definitions:
ACK ACK
The 802.11 layer 2 acknowledgement The 802.11 Layer 2 acknowledgement.
AES-CCMP
AES-Counter Mode CBC-MAC Protocol
AP AP
IEEE 802.11 Access Point IEEE 802.11 Access Point.
basic rate Basic rate
The slowest rate of all the connected devices, at which multicast The slowest rate of all the connected devices at which multicast
and broadcast traffic is generally transmitted and broadcast traffic is generally transmitted.
DVB-H
Digital Video Broadcasting - Handheld
DVB-IPDC
Digital Video Broadcasting - Internet Protocol Datacasting
DTIM DTIM
Delivery Traffic Indication Map (DTIM): An information element Delivery Traffic Indication Map; an information element that
that advertises whether or not any associated stations have advertises whether or not any associated stations have buffered
buffered multicast or broadcast frames multicast or broadcast frames.
MCS MCS
Modulation and Coding Scheme Modulation and Coding Scheme.
NOC NOC
Network Operations Center Network Operations Center.
PER PER
Packet Error Rate Packet Error Rate.
STA STA
802.11 station (e.g. handheld device) 802.11 station (e.g., handheld device).
TIM TIM
Traffic Indication Map (TIM): An information element that Traffic Indication Map; an information element that advertises
advertises whether or not any associated stations have buffered whether or not any associated stations have buffered unicast
unicast frames frames.
3. Identified multicast issues TKIP
Temporal Key Integrity Protocol
WiMAX
Worldwide Interoperability for Microwave Access
WPA
Wi-Fi Protected Access
3. Identified Multicast Issues
3.1. Issues at Layer 2 and Below 3.1. Issues at Layer 2 and Below
In this section some of the issues related to the use of multicast In this section, some of the issues related to the use of multicast
transmissions over IEEE 802 wireless technologies are described. transmissions over IEEE 802 wireless technologies are described.
3.1.1. Multicast reliability 3.1.1. Multicast Reliability
Multicast traffic is typically much less reliable than unicast Multicast traffic is typically much less reliable than unicast
traffic. Since multicast makes point-to-multipoint communications, traffic. Since multicast makes point-to-multipoint communications,
multiple acknowledgements would be needed to guarantee reception at multiple acknowledgements would be needed to guarantee reception at
all recipients. And since there are no ACKs for multicast packets, all recipients. However, since there are no ACKs for multicast
it is not possible for the Access Point (AP) to know whether or not a packets, it is not possible for the AP to know whether or not a
retransmission is needed. Even in the wired Internet, this retransmission is needed. Even in the wired Internet, this
characteristic often causes undesirably high error rates. This has characteristic often causes undesirably high error rates. This has
contributed to the relatively slow uptake of multicast applications contributed to the relatively slow uptake of multicast applications
even though the protocols have long been available. The situation even though the protocols have long been available. The situation
for wireless links is much worse, and is quite sensitive to the for wireless links is much worse and is quite sensitive to the
presence of background traffic. Consequently, there can be a high presence of background traffic. Consequently, there can be a high
packet error rate (PER) due to lack of retransmission, and because packet error rate (PER) due to lack of retransmission and because the
the sender never backs off. PER is the ratio, in percent, of the sender never backs off. PER is the ratio, in percent, of the number
number of packets not successfully received by the device. It is not of packets not successfully received by the device. It is not
uncommon for there to be a packet loss rate of 5% or more, which is uncommon for there to be a packet loss rate of 5% or more, which is
particularly troublesome for video and other environments where high particularly troublesome for video and other environments where high
data rates and high reliability are required. data rates and high reliability are required.
3.1.2. Lower and Variable Data Rate 3.1.2. Lower and Variable Data Rate
Multicast over wired differs from multicast over wireless because Multicast over wired differs from multicast over wireless because
transmission over wired links often occurs at a fixed rate. Wi-Fi, transmission over wired links often occurs at a fixed rate. Wi-Fi,
on the other hand, has a transmission rate that varies depending upon on the other hand, has a transmission rate that varies depending upon
the STA's proximity to the AP. The throughput of video flows, and the STA's proximity to the AP. The throughput of video flows and the
the capacity of the broader Wi-Fi network, will change with device capacity of the broader Wi-Fi network will change with device
movement. This impacts the ability for QoS solutions to effectively movement. This impacts the ability for QoS solutions to effectively
reserve bandwidth and provide admission control. reserve bandwidth and provide admission control.
For wireless stations authenticated and linked with an Access Point, For wireless stations authenticated and linked with an AP, the power
the power necessary for good reception can vary from station to necessary for good reception can vary from station to station. For
station. For unicast, the goal is to minimize power requirements unicast, the goal is to minimize power requirements while maximizing
while maximizing the data rate to the destination. For multicast, the data rate to the destination. For multicast, the goal is simply
the goal is simply to maximize the number of receivers that will to maximize the number of receivers that will correctly receive the
correctly receive the multicast packet; generally the Access Point multicast packet; generally, the AP has to use a much lower data rate
has to use a much lower data rate at a power level high enough for at a power level high enough for even the farthest station to receive
even the farthest station to receive the packet, for example as the packet, for example, as briefly mentioned in Section 4 of
briefly mentioned in section 2 of [RFC5757]. Consequently, the data [RFC5757]. Consequently, the data rate of a video stream, for
rate of a video stream, for instance, would be constrained by the instance, would be constrained by the environmental considerations of
environmental considerations of the least reliable receiver the least-reliable receiver associated with the AP.
associated with the Access Point.
Because more robust modulation and coding schemes (MCSs) have longer Because more robust modulation and coding schemes (MCSs) have a
range but also lower data rate, multicast / broadcast traffic is longer range but also a lower data rate, multicast/broadcast traffic
generally transmitted at the slowest rate of all the connected is generally transmitted at the slowest rate of all the connected
devices. This is also known as the basic rate. The amount of devices. This is also known as the basic rate. The amount of
additional interference depends on the specific wireless technology. additional interference depends on the specific wireless technology.
In fact, backward compatibility and multi-stream implementations mean In fact, backward compatibility and multi-stream implementations mean
that the maximum unicast rates are currently up to a few Gbps, so that the maximum unicast rates are currently up to a few Gbps, so
there can be more than 3 orders of magnitude difference in the there can be more than 3 orders of magnitude difference in the
transmission rate between multicast / broadcast versus optimal transmission rate between multicast/broadcast versus optimal unicast
unicast forwarding. Some techniques employed to increase spectral forwarding. Some techniques employed to increase spectral
efficiency, such as spatial multiplexing in MIMO systems, are not efficiency, such as spatial multiplexing in Multiple Input Multiple
available with more than one intended receiver; it is not the case Output (MIMO) systems, are not available with more than one intended
that backwards compatibility is the only factor responsible for lower receiver; it is not the case that backwards compatibility is the only
multicast transmission rates. factor responsible for lower multicast transmission rates.
Wired multicast also affects wireless LANs when the AP extends the Wired multicast also affects wireless LANs when the AP extends the
wired segment; in that case, multicast / broadcast frames on the wired segment; in that case, multicast/broadcast frames on the wired
wired LAN side are copied to the Wireless Local Area Network (WLAN). LAN side are copied to the Wireless Local Area Network (WLAN). Since
Since broadcast messages are transmitted at the most robust MCS, many broadcast messages are transmitted at the most robust MCS, many large
large frames are sent at a slow rate over the air. frames are sent at a slow rate over the air.
3.1.3. Capacity and Impact on Interference 3.1.3. Capacity and Impact on Interference
Transmissions at a lower rate require longer occupancy of the Transmissions at a lower rate require longer occupancy of the
wireless medium and thus take away from the airtime of other wireless medium and thus take away from the airtime of other
communications and degrade the overall capacity. Furthermore, communications and degrade the overall capacity. Furthermore,
transmission at higher power, as is required to reach all multicast transmission at higher power, as is required to reach all multicast
STAs associated to the AP, proportionately increases the area of STAs associated with the AP, proportionately increases the area of
interference with other consumers of the radio spectrum. interference with other consumers of the radio spectrum.
3.1.4. Power-save Effects on Multicast 3.1.4. Power-Save Effects on Multicast
One of the characteristics of multicast transmission over wifi is One of the characteristics of multicast transmission over Wi-Fi is
that every station has to be configured to wake up to receive the that every station has to be configured to wake up to receive the
multicast frame, even though the received packet may ultimately be multicast frame, even though the received packet may ultimately be
discarded. This process can have a large effect on the power discarded. This process can have a large effect on the power
consumption by the multicast receiver station. For this reason there consumption by the multicast receiver station. For this reason,
are workarounds, such as Directed Multicast Service (DMS) described there are workarounds, such as Directed Multicast Service (DMS)
in Section 4, to prevent unnecessarily waking up stations. described in Section 4, to prevent unnecessarily waking up stations.
Multicast (and unicast) can work poorly with the power-save Multicast (and unicast) can work poorly with the power-save
mechanisms defined in IEEE 802.11e, for the following reasons. mechanisms defined in IEEE 802.11e for the following reasons.
* Clients may be unable to stay in sleep mode due to multicast * Clients may be unable to stay in sleep mode due to multicast
control packets frequently waking them up. control packets frequently waking them up.
* A unicast packet is delayed until an STA wakes up and requests it. * A unicast packet is delayed until an STA wakes up and requests it.
Unicast traffic may also be delayed to improve power save, Unicast traffic may also be delayed to improve power save and
efficiency and increase probability of aggregation. efficiency and to increase the probability of aggregation.
* Multicast traffic is delayed in a wireless network if any of the * Multicast traffic is delayed in a wireless network if any of the
STAs in that network are power savers. All STAs associated to the STAs in that network are power savers. All STAs associated with
AP have to be awake at a known time to receive multicast traffic. the AP have to be awake at a known time to receive multicast
traffic.
* Packets can also be discarded due to buffer limitations in the AP * Packets can also be discarded due to buffer limitations in the AP
and non-AP STA. and non-AP STA.
3.2. Issues at Layer 3 and Above 3.2. Issues at Layer 3 and Above
This section identifies some representative IETF protocols, and This section identifies some representative IETF protocols and
describes possible negative effects due to performance degradation describes possible negative effects due to performance degradation
when using multicast transmissions for control messages. Common uses when using multicast transmissions for control messages. Common uses
of multicast include: of multicast include:
* Control plane signaling * Control plane signaling
* Neighbor Discovery * Neighbor Discovery
* Address Resolution
* Address resolution
* Service Discovery * Service Discovery
* Applications (video delivery, stock data, etc.) * Applications (video delivery, stock data, etc.)
* On-demand routing * On-demand routing
* Backbone construction * Backbone construction
* Other L3 protocols (non-IP)
User Datagram Protocol (UDP) is the most common transport layer * Other Layer 3 protocols (non-IP)
User Datagram Protocol (UDP) is the most common transport-layer
protocol for multicast applications. By itself, UDP is not reliable protocol for multicast applications. By itself, UDP is not reliable
-- messages may be lost or delivered out of order. -- messages may be lost or delivered out of order.
3.2.1. IPv4 issues 3.2.1. IPv4 Issues
The following list contains some representative discovery protocols, The following list contains some representative discovery protocols
which utilize broadcast/multicast, that are used with IPv4. that utilize broadcast/multicast and are used with IPv4.
* ARP [RFC0826] * ARP [RFC0826]
* DHCP [RFC2131] * DHCP [RFC2131]
* mDNS [RFC6762]
* uPnP [RFC6970] * Multicast DNS (mDNS) [RFC6762]
* Universal Plug and Play (uPnP) [RFC6970]
After initial configuration, ARP (described in more detail later), After initial configuration, ARP (described in more detail later),
DHCP and uPnP occur much less commonly, but service discovery can DHCP, and uPnP occur much less commonly, but service discovery can
occur at any time. Some widely-deployed service discovery protocols occur at any time. Some widely deployed service discovery protocols
(e.g., for finding a printer) utilize mDNS (i.e., multicast) which is (e.g., for finding a printer) utilize mDNS (i.e., multicast), which
often dropped by operators. Even if multicast snooping [RFC4541] is often dropped by operators. Even if multicast snooping [RFC4541]
(which provides the benefit of conserving bandwidth on those segments (which provides the benefit of conserving bandwidth on those segments
of the network where no node has expressed interest in receiving of the network where no node has expressed interest in receiving
packets addressed to the group address) is utilized, many devices can packets addressed to the group address) is utilized, many devices can
register at once and cause serious network degradation. register at once and cause serious network degradation.
3.2.2. IPv6 issues 3.2.2. IPv6 Issues
IPv6 makes extensive use of multicast, including the following: IPv6 makes extensive use of multicast, including the following:
* DHCPv6 [RFC8415] * DHCPv6 [RFC8415]
* Protocol Independent Multicast (PIM) [RFC7761] * Protocol Independent Multicast (PIM) [RFC7761]
* IPv6 Neighbor Discovery Protocol (NDP) [RFC4861] * IPv6 Neighbor Discovery Protocol (NDP) [RFC4861]
* multicast DNS (mDNS) [RFC6762]
* Multicast DNS (mDNS) [RFC6762]
* Router Discovery [RFC4286] * Router Discovery [RFC4286]
IPv6 NDP Neighbor Solicitation (NS) messages used in Duplicate IPv6 NDP Neighbor Solicitation (NS) messages used in Duplicate
Address Detection (DAD) and Address Lookup make use of Link-Scope Address Detection (DAD) and address lookup make use of link-scope
multicast. In contrast to IPv4, an IPv6 node will typically use multicast. In contrast to IPv4, an IPv6 node will typically use
multiple addresses, and may change them often for privacy reasons. multiple addresses and may change them often for privacy reasons.
This intensifies the impact of multicast messages that are associated This intensifies the impact of multicast messages that are associated
to the mobility of a node. Router advertisement (RA) messages are with the mobility of a node. Router advertisement (RA) messages are
also periodically multicasted over the Link. also periodically multicast over the link.
Neighbors may be considered lost if several consecutive Neighbor Neighbors may be considered lost if several consecutive Neighbor
Discovery packets fail. Discovery packets fail.
3.2.3. MLD issues 3.2.3. MLD Issues
Multicast Listener Discovery (MLD) [RFC4541] is used to identify Multicast Listener Discovery (MLD) [RFC4541] is used to identify
members of a multicast group that are connected to the ports of a members of a multicast group that are connected to the ports of a
switch. Forwarding multicast frames into a Wi-Fi-enabled area can switch. Forwarding multicast frames into a Wi-Fi-enabled area can
use switch support for hardware forwarding state information. use switch support for hardware forwarding state information.
However, since IPv6 makes heavy use of multicast, each STA with an However, since IPv6 makes heavy use of multicast, each STA with an
IPv6 address will require state on the switch for several and IPv6 address will require state on the switch for several and
possibly many multicast solicited-node addresses. A solicited-node possibly many solicited-node multicast addresses. A solicited-node
multicast address is an IPv6 multicast address used by NDP to verify multicast address is an IPv6 multicast address used by NDP to verify
whether an IPv6 address is already used by the local-link. Multicast whether an IPv6 address is already used by the local link. Multicast
addresses that do not have forwarding state installed (perhaps due to addresses that do not have forwarding state installed (perhaps due to
hardware memory limitations on the switch) cause frames to be flooded hardware memory limitations on the switch) cause frames to be flooded
on all ports of the switch. Some switch vendors do not support MLD, on all ports of the switch. Some switch vendors do not support MLD
for link-scope multicast, due to the increase it can cause in state. for link-scope multicast due to the increase it can cause in state.
3.2.4. Spurious Neighbor Discovery 3.2.4. Spurious Neighbor Discovery
On the Internet there is a "background radiation" of scanning traffic On the Internet, there is a "background radiation" of scanning
(people scanning for vulnerable machines) and backscatter (responses traffic (people scanning for vulnerable machines) and backscatter
from spoofed traffic, etc). This means that routers very often (responses from spoofed traffic, etc.). This means that routers very
receive packets destined for IPv4 addresses regardless of whether often receive packets destined for IPv4 addresses regardless of
those IP addresses are in use. In the cases where the IP is assigned whether those IP addresses are in use. In the cases where the IP is
to a host, the router broadcasts an ARP request, gets back an ARP assigned to a host, the router broadcasts an ARP request, receives an
reply, and caches it; then traffic can be delivered to the host. ARP reply, and caches it; then, traffic can be delivered to the host.
When the IP address is not in use, the router broadcasts one (or When the IP address is not in use, the router broadcasts one (or
more) ARP requests, and never gets a reply. This means that it does more) ARP requests and never gets a reply. This means that it does
not populate the ARP cache, and the next time there is traffic for not populate the ARP cache, and the next time there is traffic for
that IP address the router will rebroadcast the ARP requests. that IP address, the router will rebroadcast the ARP requests.
The rate of these ARP requests is proportional to the size of the The rate of these ARP requests is proportional to the size of the
subnets, the rate of scanning and backscatter, and how long the subnets, the rate of scanning and backscatter, and how long the
router keeps state on non-responding ARPs. As it turns out, this router keeps state on non-responding ARPs. As it turns out, this
rate is inversely proportional to how occupied the subnet is (valid rate is inversely proportional to how occupied the subnet is (valid
ARPs end up in a cache, stopping the broadcasting; unused IPs never ARPs end up in a cache, stopping the broadcasting; unused IPs never
respond, and so cause more broadcasts). Depending on the address respond, and so cause more broadcasts). Depending on the address
space in use, the time of day, how occupied the subnet is, and other space in use, the time of day, how occupied the subnet is, and other
unknown factors, thousands of broadcasts per second have been unknown factors, thousands of broadcasts per second have been
observed. Around 2,000 broadcasts per second have been observed at observed. Around 2,000 broadcasts per second have been observed at
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resolution by multicasting a Neighbor Solicitation that asks the resolution by multicasting a Neighbor Solicitation that asks the
target node to return its link-layer address. Neighbor Solicitation target node to return its link-layer address. Neighbor Solicitation
messages are multicast to the solicited-node multicast address of the messages are multicast to the solicited-node multicast address of the
target address. The target returns its link-layer address in a target address. The target returns its link-layer address in a
unicast Neighbor Advertisement message. A single request-response unicast Neighbor Advertisement message. A single request-response
pair of packets is sufficient for both the initiator and the target pair of packets is sufficient for both the initiator and the target
to resolve each other's link-layer addresses; the initiator includes to resolve each other's link-layer addresses; the initiator includes
its link-layer address in the Neighbor Solicitation. its link-layer address in the Neighbor Solicitation.
On a wired network, there is not a huge difference between unicast, On a wired network, there is not a huge difference between unicast,
multicast and broadcast traffic. Due to hardware filtering (see, multicast, and broadcast traffic. Due to hardware filtering (see,
e.g., [Deri-2010]), inadvertently flooded traffic (or excessive e.g., [Deri-2010]), inadvertently flooded traffic (or excessive
ethernet multicast) on wired networks can be quite a bit less costly, Ethernet multicast) on wired networks can be quite a bit less costly
compared to wireless cases where sleeping devices have to wake up to compared to wireless cases where sleeping devices have to wake up to
process packets. Wired Ethernets tend to be switched networks, process packets. Wired Ethernets tend to be switched networks,
further reducing interference from multicast. There is effectively further reducing interference from multicast. There is effectively
no collision / scheduling problem except at extremely high port no collision / scheduling problem except at extremely high port
utilizations. utilizations.
This is not true in the wireless realm; wireless equipment is often This is not true in the wireless realm; wireless equipment is often
unable to send high volumes of broadcast and multicast traffic, unable to send high volumes of broadcast and multicast traffic,
causing numerous broadcast and multicast packets to be dropped. causing numerous broadcast and multicast packets to be dropped.
Consequently, when a host connects it is often not able to complete Consequently, when a host connects, it is often not able to complete
DHCP, and IPv6 RAs get dropped, leading to users being unable to use DHCP, and IPv6 RAs get dropped, leading to users being unable to use
the network. the network.
4. Multicast protocol optimizations 4. Multicast Protocol Optimizations
This section lists some optimizations that have been specified in This section lists some optimizations that have been specified in
IEEE 802 and IETF that are aimed at reducing or eliminating the IEEE 802 and IETF that are aimed at reducing or eliminating the
issues discussed in Section 3. issues discussed in Section 3.
4.1. Proxy ARP in 802.11-2012 4.1. Proxy ARP in 802.11-2012
The AP knows the MAC address and IP address for all associated STAs. The AP knows the Medium Access Control (MAC) address and IP address
In this way, the AP acts as the central "manager" for all the 802.11 for all associated STAs. In this way, the AP acts as the central
STAs in its basic service set (BSS). Proxy ARP is easy to implement "manager" for all the 802.11 STAs in its Basic Service Set (BSS).
at the AP, and offers the following advantages: Proxy ARP is easy to implement at the AP and offers the following
advantages:
* Reduced broadcast traffic (transmitted at low MCS) on the wireless * Reduced broadcast traffic (transmitted at low MCS) on the wireless
medium medium.
* STA benefits from extended power save in sleep mode, as ARP * STA benefits from extended power save in sleep mode, as ARP
requests for STA's IP address are handled instead by the AP. requests for STA's IP address are handled instead by the AP.
* ARP frames are kept off the wireless medium. * ARP frames are kept off the wireless medium.
* No changes are needed to STA implementation. * No changes are needed to STA implementation.
Here is the specification language as described in clause 10.23.13 of Here is the specification language as described in clause 10.23.13 of
[dot11-proxyarp]: [dot11-proxyarp]:
When the AP supports Proxy ARP "[...] the AP shall maintain a | When the AP supports Proxy ARP "[...] the AP shall maintain a
Hardware Address to Internet Address mapping for each associated | Hardware Address to Internet Address mapping for each associated
station, and shall update the mapping when the Internet Address of | station, and shall update the mapping when the Internet Address of
the associated station changes. When the IPv4 address being | the associated station changes. When the IPv4 address being
resolved in the ARP request packet is used by a non-AP STA | resolved in the ARP request packet is used by a non-AP STA
currently associated to the BSS, the proxy ARP service shall | currently associated to the BSS, the proxy ARP service shall
respond on behalf of the non-AP STA". | respond on behalf of the STA to an ARP request or an ARP Probe.
4.2. IPv6 Address Registration and Proxy Neighbor Discovery 4.2. IPv6 Address Registration and Proxy Neighbor Discovery
As used in this section, a Low-Power Wireless Personal Area Network As used in this section, a Low-Power Wireless Personal Area Network
(6LoWPAN) denotes a low power lossy network (LLN) that supports (6LoWPAN) denotes a Low-Power and Lossy Network (LLN) that supports
6LoWPAN Header Compression (HC) [RFC6282]. A 6TiSCH network 6LoWPAN Header Compression (HC) [RFC6282]. A 6TiSCH network
[I-D.ietf-6tisch-architecture] is an example of a 6LowPAN. In order [RFC9030] is an example of a 6LoWPAN. In order to control the use of
to control the use of IPv6 multicast over 6LoWPANs, the 6LoWPAN IPv6 multicast over 6LoWPANs, the 6LoWPAN Neighbor Discovery (6LoWPAN
Neighbor Discovery (6LoWPAN ND) [RFC6775] standard defines an address ND) [RFC6775] standard defines an address registration mechanism that
registration mechanism that relies on a central registry to assess relies on a central registry to assess address uniqueness as a
address uniqueness, as a substitute to the inefficient DAD mechanism substitute to the inefficient DAD mechanism found in the mainstream
found in the mainstream IPv6 Neighbor Discovery Protocol (NDP) IPv6 Neighbor Discovery Protocol (NDP) [RFC4861] [RFC4862].
[RFC4861][RFC4862].
The 6lo Working Group has specified an update [RFC8505] to RFC6775. The 6lo Working Group has specified an update to [RFC6775]. Wireless
Wireless devices can register their address to a Backbone Router devices can register their address to a Backbone Router [RFC8929],
[I-D.ietf-6lo-backbone-router], which proxies for the registered which proxies for the registered addresses with the IPv6 NDP running
addresses with the IPv6 NDP running on a high speed aggregating on a high-speed aggregating backbone. The update also enables a
backbone. The update also enables a proxy registration mechanism on proxy registration mechanism on behalf of the Registered Node, e.g.,
behalf of the registered node, e.g. by a 6LoWPAN router to which the by a 6LoWPAN router to which the mobile node is attached.
mobile node is attached.
The general idea behind the backbone router concept is that broadcast The general idea behind the Backbone Router concept is that broadcast
and multicast messaging should be tightly controlled in a variety of and multicast messaging should be tightly controlled in a variety of
WLANs and Wireless Personal Area Networks (WPANs). Connectivity to a WLANs and Wireless Personal Area Networks (WPANs). Connectivity to a
particular link that provides the subnet should be left to Layer-3. particular link that provides the subnet should be left to Layer 3.
The model for the Backbone Router operation is represented in The model for the Backbone Router operation is represented in
Figure 1. Figure 1.
| |
+-----+ +-----+
| | Gateway (default) router | | Gateway (default) router
| | | |
+-----+ +-----+
| |
| Backbone Link | Backbone Link
skipping to change at page 12, line 32 skipping to change at line 570
o o o o o o o o o o o o o o
LLN 1 LLN 2 LLN 3 LLN 1 LLN 2 LLN 3
Figure 1: Backbone Link and Backbone Routers Figure 1: Backbone Link and Backbone Routers
LLN nodes can move freely from an LLN anchored at one IPv6 Backbone LLN nodes can move freely from an LLN anchored at one IPv6 Backbone
Router to an LLN anchored at another Backbone Router on the same Router to an LLN anchored at another Backbone Router on the same
backbone, keeping any of the IPv6 addresses they have configured. backbone, keeping any of the IPv6 addresses they have configured.
The Backbone Routers maintain a Binding Table of their Registered The Backbone Routers maintain a Binding Table of their Registered
Nodes, which serves as a distributed database of all the LLN Nodes. Nodes, which serves as a distributed database of all the LLN nodes.
An extension to the Neighbor Discovery Protocol is introduced to An extension to the Neighbor Discovery Protocol is introduced to
exchange Binding Table information across the Backbone Link as needed exchange Binding Table information across the Backbone Link as needed
for the operation of IPv6 Neighbor Discovery. for the operation of IPv6 Neighbor Discovery.
RFC6775 and follow-on work [RFC8505] address the needs of LLNs, and [RFC6775] and follow-on work [RFC8505] address the needs of LLNs, and
similar techniques are likely to be valuable on any type of link similar techniques are likely to be valuable on any type of link
where sleeping devices are attached, or where the use of broadcast where sleeping devices are attached or where the use of broadcast and
and multicast operations should be limited. multicast operations should be limited.
4.3. Buffering to Improve Battery Life 4.3. Buffering to Improve Battery Life
Methods have been developed to help save battery life; for example, a Methods have been developed to help save battery life; for example, a
device might not wake up when the AP receives a multicast packet. device might not wake up when the AP receives a multicast packet.
The AP acts on behalf of STAs in various ways. To enable use of the The AP acts on behalf of STAs in various ways. To enable use of the
power-saving feature for STAs in its BSS, the AP buffers frames for power-saving feature for STAs in its BSS, the AP buffers frames for
delivery to the STA at the time when the STA is scheduled for delivery to the STA at the time when the STA is scheduled for
reception. If an AP, for instance, expresses a DTIM (Delivery reception. If an AP, for instance, expresses a Delivery Traffic
Traffic Indication Message) of 3 then the AP will send a multicast Indication Message (DTIM) of 3, then the AP will send a multicast
packet every 3 packets. In fact, when any single wireless STA packet every 3 packets. In fact, when any single wireless STA
associated with an access point has 802.11 power-save mode enabled, associated with an AP has 802.11 power-save mode enabled, the AP
the access point buffers all multicast frames and sends them only buffers all multicast frames and sends them only after the next DTIM
after the next DTIM beacon. beacon.
In practice, most AP's will send a multicast every 30 packets. For In practice, most APs will send a multicast every 30 packets. For
unicast the AP could send a TIM (Traffic Indication Message), but for unicast, the AP could send a Traffic Indication Message (TIM), but,
multicast the AP sends a broadcast to everyone. DTIM does power for multicast, the AP sends a broadcast to everyone. DTIM does power
management but STAs can choose whether or not to wake up and whether management, but STAs can choose whether to wake up and whether to
or not to drop the packet. Unfortunately, without proper drop the packet. Unfortunately, without proper administrative
administrative control, such STAs may be unable to determine why control, such STAs may be unable to determine why their multicast
their multicast operations do not work. operations do not work.
4.4. Limiting multicast buffer hardware queue depth 4.4. Limiting Multicast Buffer Hardware Queue Depth
The CAB (Content after Beacon) queue is used for beacon-triggered The Content after Beacon (CAB) queue is used for beacon-triggered
transmission of buffered multicast frames. If lots of multicast transmission of buffered multicast frames. If lots of multicast
frames were buffered, and this queue fills up, it drowns out all frames were buffered and this queue fills up, it drowns out all
regular traffic. To limit the damage that buffered traffic can do, regular traffic. To limit the damage that buffered traffic can do,
some drivers limit the amount of queued multicast data to a fraction some drivers limit the amount of queued multicast data to a fraction
of the beacon_interval. An example of this is [CAB]. of the beacon_interval. An example of this is [CAB].
4.5. IPv6 support in 802.11-2012 4.5. IPv6 Support in 802.11-2012
IPv6 uses NDP instead of ARP. Every IPv6 node subscribes to a IPv6 uses NDP instead of ARP. Every IPv6 node subscribes to a
special multicast address for this purpose. special multicast address for this purpose.
Here is the specification language from clause 10.23.13 of Here is the specification language from clause 10.23.13 of
[dot11-proxyarp]: [dot11-proxyarp]:
"When an IPv6 address is being resolved, the Proxy Neighbor | When an IPv6 address is being resolved, the Proxy Neighbor
Discovery service shall respond with a Neighbor Advertisement | Discovery service shall respond with a Neighbor Advertisement
message [...] on behalf of an associated STA to an [ICMPv6] | message [...] on behalf of an associated STA to an [ICMPv6]
Neighbor Solicitation message [...]. When MAC address mappings | Neighbor Solicitation message [...]. When MAC address mappings
change, the AP may send unsolicited Neighbor Advertisement | change, the AP may send unsolicited Neighbor Advertisement
Messages on behalf of a STA." | Messages on behalf of a STA.
NDP may be used to request additional information NDP may be used to request additional information using the following
methods, among others:
* Maximum Transmission Unit * Maximum Transmission Unit
* Router Solicitation * Router Solicitation
* Router Advertisement, etc.
NDP messages are sent as group addressed (broadcast) frames in * Router Advertisement
NDP messages are sent as group-addressed (broadcast) frames in
802.11. Using the proxy operation helps to keep NDP messages off the 802.11. Using the proxy operation helps to keep NDP messages off the
wireless medium. wireless medium.
4.6. Using Unicast Instead of Multicast 4.6. Using Unicast Instead of Multicast
It is often possible to transmit multicast control and data messages It is often possible to transmit multicast control and data messages
by using unicast transmissions to each station individually. by using unicast transmissions to each station individually.
4.6.1. Overview 4.6.1. Overview
In many situations, it's a good choice to use unicast instead of 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 multicast over the Wi-Fi link. This avoids most of the problems
specific to multicast over Wi-Fi, since the individual frames are specific to multicast over Wi-Fi, since the individual frames are
then acknowledged and buffered for power save clients, in the way then acknowledged and buffered for power-save clients in the way that
that unicast traffic normally operates. unicast traffic normally operates.
This approach comes with the tradeoff of sometimes sending the same This approach comes with the trade-off of sometimes sending the same
packet multiple times over the Wi-Fi link. However, in many cases, 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 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 trade-off since the Wi-Fi link may have enough capacity for the
unicast traffic to be transmitted to each subscribed STA, even though unicast traffic to be transmitted to each subscribed STA, even though
multicast addressing may have been necessary for the upstream access multicast addressing may have been necessary for the upstream access
network. network.
Several technologies exist that can be used to arrange unicast Several technologies exist that can be used to arrange unicast
transport over the Wi-Fi link, outlined in the subsections below. transport over the Wi-Fi link, outlined in the subsections below.
4.6.2. Layer 2 Conversion to Unicast 4.6.2. Layer 2 Conversion to Unicast
It is often possible to transmit multicast control and data messages It is often possible to transmit multicast control and data messages
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Although there is not yet a standardized method of conversion, at Although there is not yet a standardized method of conversion, at
least one widely available implementation exists in the Linux least one widely available implementation exists in the Linux
bridging code [bridge-mc-2-uc]. Other proprietary implementations bridging code [bridge-mc-2-uc]. Other proprietary implementations
are available from various vendors. In general, these are available from various vendors. In general, these
implementations perform a straightforward mapping for groups or implementations perform a straightforward mapping for groups or
channels, discovered by IGMP or MLD snooping, to the corresponding channels, discovered by IGMP or MLD snooping, to the corresponding
unicast MAC addresses. unicast MAC addresses.
4.6.3. Directed Multicast Service (DMS) 4.6.3. Directed Multicast Service (DMS)
There are situations where more is needed than simply converting DMS enables an STA to request that the AP transmit multicast group-
multicast to unicast. For these purposes, DMS enables an STA to addressed frames destined to the requesting STAs as individually
request that the AP transmit multicast group addressed frames addressed frames (i.e., convert multicast to unicast). Here are some
destined to the requesting STAs as individually addressed frames characteristics of DMS:
[i.e., convert multicast to unicast]. Here are some characteristics
of DMS: * Requires 802.11n Aggregate MAC Service Data Units (A-MSDUs).
* Requires 802.11n A-MSDUs
* Individually addressed frames are acknowledged and are buffered * Individually addressed frames are acknowledged and are buffered
for power save STAs for power-save STAs.
* The requesting STA may specify traffic characteristics for DMS * The requesting STA may specify traffic characteristics for DMS
traffic traffic.
* DMS was defined in IEEE Std 802.11v-2011
* DMS was defined in IEEE Std 802.11v-2011 [v2011].
* DMS requires changes to both AP and STA implementation. * DMS requires changes to both AP and STA implementation.
DMS is not currently implemented in products. See [Tramarin2017] and DMS is not currently implemented in products. See [Tramarin2017] and
[Oliva2013] for more information. [Oliva2013] for more information.
4.6.4. Automatic Multicast Tunneling (AMT) 4.6.4. Automatic Multicast Tunneling (AMT)
AMT[RFC7450] provides a method to tunnel multicast IP packets inside AMT [RFC7450] provides a method to tunnel multicast IP packets inside
unicast IP packets over network links that only support unicast. unicast IP packets over network links that only support unicast.
When an operating system or application running on an STA has an AMT When an operating system or application running on an STA has an AMT
gateway capability integrated, it's possible to use unicast to 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 traverse the Wi-Fi link by deploying an AMT relay in the non-Wi-Fi
portion of the network connected to the AP. portion of the network connected to the AP.
It is recommended that multicast-enabled networks deploying AMT It is recommended that multicast-enabled networks deploying AMT
relays for this purpose make the relays locally discoverable with the relays for this purpose make the relays locally discoverable with the
following methods, as described in following methods, as described in [RFC8777]:
[I-D.ietf-mboned-driad-amt-discovery]:
* DNS-SD [RFC6763] * DNS-based Service Discovery (DNS-SD) [RFC6763]
* the well-known IP addresses from Section 7 of [RFC7450]
* The well-known IP addresses from Section 7 of [RFC7450]
An AMT gateway that implements multiple standard discovery methods is An AMT gateway that implements multiple standard discovery methods is
more likely to discover the local multicast-capable network, instead more likely to discover the local multicast-capable network instead
of forming a connection to a non-local AMT relay further upstream. of forming a connection to a nonlocal AMT relay further upstream.
4.7. GroupCast with Retries (GCR) 4.7. GroupCast with Retries (GCR)
GCR (defined in [dot11aa]) provides greater reliability by using GCR (defined in [dot11aa]) provides greater reliability by using
either unsolicited retries or a block acknowledgement mechanism. GCR either unsolicited retries or a block acknowledgement mechanism. GCR
increases probability of broadcast frame reception success, but still increases the probability of broadcast frame reception success but
does not guarantee success. still does not guarantee success.
For the block acknowledgement mechanism, the AP transmits each group For the block acknowledgement mechanism, the AP transmits each group-
addressed frame as conventional group addressed transmission. addressed frame as a conventional group-addressed transmission.
Retransmissions are group addressed, but hidden from non-11aa STAs. Retransmissions are group addressed but hidden from non-11aa STAs. A
A directed block acknowledgement scheme is used to harvest reception directed block acknowledgement scheme is used to harvest reception
status from receivers; retransmissions are based upon these status from receivers; retransmissions are based upon these
responses. responses.
GCR is suitable for all group sizes including medium to large groups. GCR is suitable for all group sizes including medium to large groups.
As the number of devices in the group increases, GCR can send block As the number of devices in the group increases, GCR can send block
acknowledgement requests to only a small subset of the group. GCR acknowledgement requests to only a small subset of the group. GCR
does require changes to both AP and STA implementations. does require changes to both AP and STA implementations.
GCR may introduce unacceptable latency. After sending a group of GCR may introduce unacceptable latency. After sending a group of
data frames to the group, the AP has to do the following: data frames to the group, the AP has to do the following:
* unicast a Block Ack Request (BAR) to a subset of members. * Unicast a Block Ack Request (BAR) to a subset of members.
* wait for the corresponding Block Ack (BA).
* retransmit any missed frames. * Wait for the corresponding Block Ack (BA).
* resume other operations that may have been delayed.
* Retransmit any missed frames.
* Resume other operations that may have been delayed.
This latency may not be acceptable for some traffic. This latency may not be acceptable for some traffic.
There are ongoing extensions in 802.11 to improve GCR performance. There are ongoing extensions in 802.11 to improve GCR performance.
* BAR is sent using downlink MU-MIMO (note that downlink MU-MIMO is * BAR is sent using downlink Multi-User MIMO.
already specified in 802.11-REVmc 4.3).
* BA is sent using uplink MU-MIMO (which is a .11ax feature). * BA is sent using uplink MU-MIMO (uplink MU-MIMO is an IEEE
* Additional 802.11ax extensions are under consideration; see 801.11ax-2021 feature).
[mc-ack-mux]
* Latency may also be reduced by simultaneously receiving BA * Latency may also be reduced by simultaneously receiving BA
information from multiple STAs. information from multiple STAs.
5. Operational optimizations 5. Operational Optimizations
This section lists some operational optimizations that can be This section lists some operational optimizations that can be
implemented when deploying wireless IEEE 802 networks to mitigate implemented when deploying wireless IEEE 802 networks to mitigate
some of the issues discussed in Section 3. some of the issues discussed in Section 3.
5.1. Mitigating Problems from Spurious Neighbor Discovery 5.1. Mitigating Problems from Spurious Neighbor Discovery
ARP Sponges ARP Sponges
An ARP Sponge sits on a network and learns which IP addresses An ARP Sponge sits on a network and learns which IP addresses
are actually in use. It also listens for ARP requests, and, if are actually in use. It also listens for ARP requests, and, if
it sees an ARP for an IP address that it believes is not used, it sees an ARP for an IP address that it believes is not used,
it will reply with its own MAC address. This means that the it will reply with its own MAC address. This means that the
router now has an IP to MAC mapping, which it caches. If that router now has an IP-to-MAC mapping, which it caches. If that
IP is later assigned to a machine (e.g using DHCP), the ARP IP is later assigned to a machine (e.g., using DHCP), the ARP
sponge will see this, and will stop replying for that address. Sponge will see this and will stop replying for that address.
Gratuitous ARPs (or the machine ARPing for its gateway) will Gratuitous ARPs (or the machine ARPing for its gateway) will
replace the sponged address in the router ARP table. This replace the sponged address in the router ARP table. This
technique is quite effective; but, unfortunately, the ARP technique is quite effective; unfortunately, the ARP Sponge
sponge daemons were not really designed for this use (one of daemons were not really designed for this use (one of the most
the most widely deployed arp sponges [arpsponge], was designed widely deployed ARP Sponges [arpsponge] was designed to deal
to deal with the disappearance of participants from an IXP) and with the disappearance of participants from an Internet
so are not optimized for this purpose. One daemon is needed Exchange Point (IXP)) and so are not optimized for this
per subnet, the tuning is tricky (the scanning rate versus the purpose. One daemon is needed per subnet; the tuning is tricky
population rate versus retires, etc.) and sometimes daemons (the scanning rate versus the population rate versus retries,
just stop, requiring a restart of the daemon which causes etc.), and sometimes daemons just stop, requiring a restart of
disruption. the daemon that causes disruption.
Router mitigations Router mitigations
Some routers (often those based on Linux) implement a "negative Some routers (often those based on Linux) implement a "negative
ARP cache" daemon. If the router does not see a reply to an ARP cache" daemon. If the router does not see a reply to an
ARP it can be configured to cache this information for some ARP, it can be configured to cache this information for some
interval. Unfortunately, the core routers in use often do not interval. Unfortunately, the core routers in use often do not
support this. Instead, when a host connects to a network and support this. Instead, when a host connects to a network and
gets an IP address, it will ARP for its default gateway (the gets an IP address, it will ARP for its default gateway (the
router). The router will update its cache with the IP to host router). The router will update its cache with the IP to host
MAC mapping learned from the request (passive ARP learning). MAC mapping learned from the request (passive ARP learning).
Firewall unused space Firewall unused space
The distribution of users on wireless networks / subnets may The distribution of users on wireless networks / subnets may
change in various use cases, such as conference venues (e.g change in various use cases, such as conference venues (e.g.,
SSIDs are renamed, some SSIDs lose favor, etc). This makes Service Set Identifiers (SSIDs) are renamed, some SSIDs lose
utilization for particular SSIDs difficult to predict ahead of favor, etc.). This makes utilization for particular SSIDs
time, but usage can be monitored as attendees use the different difficult to predict ahead of time, but usage can be monitored
networks. Configuring multiple DHCP pools per subnet, and as attendees use the different networks. Configuring multiple
enabling them sequentially, can create a large subnet, from DHCP pools per subnet and enabling them sequentially can create
which only addresses in the lower portions are assigned. a large subnet from which only addresses in the lower portions
Therefore input IP access lists can be applied, which deny are assigned. Therefore, input IP access lists can be applied,
traffic to the upper, unused portions. Then the router does which deny traffic to the upper, unused portions. Then the
not attempt to forward packets to the unused portions of the router does not attempt to forward packets to the unused
subnets, and so does not ARP for it. This method has proven to portions of the subnets and so does not ARP for it. This
be very effective, but is somewhat of a blunt axe, is fairly method has proven to be very effective but is somewhat of a
labor intensive, and requires coordination. blunt axe, is fairly labor intensive, and requires
Disabling/filtering ARP requests coordination.
Disabling/Filtering ARP requests
In general, the router does not need to ARP for hosts; when a In general, the router does not need to ARP for hosts; when a
host connects, the router can learn the IP to MAC mapping from host connects, the router can learn the IP-to-MAC mapping from
the ARP request sent by that host. Consequently it should be the ARP request sent by that host. Consequently, it should be
possible to disable and / or filter ARP requests from the possible to disable and/or filter ARP requests from the router.
router. Unfortunately, ARP is a very low level / fundamental Unfortunately, ARP is a very low-level/fundamental part of the
part of the IP stack, and is often offloaded from the normal IP stack and is often offloaded from the normal control plane.
control plane. While many routers can filter layer-2 traffic, While many routers can filter Layer 2 traffic, this is usually
this is usually implemented as an input filter and / or has implemented as an input filter and/or has limited ability to
limited ability to filter output broadcast traffic. This means filter output broadcast traffic. This means that the seemingly
that the simple "just disable ARP or filter it outbound" seems simple and obvious solution to "just disable ARP or filter it
like a really simple (and obvious) solution, but outbound" is made difficult or awkward in practice by
implementations / architectural issues make this difficult or implementations and/or architectural issues.
awkward in practice.
NAT NAT
Broadcasts can often be caused by outside wifi scanning / Broadcasts can often be caused by outside Wi-Fi scanning /
backscatter traffic. In order to reduce the impact of backscatter traffic. In order to reduce the impact of
broadcasts, NAT can be used on the entire (or a large portion) broadcasts, NAT can be used on the entire (or a large portion)
of a network. This would eliminate NAT translation entries for of a network. This would eliminate NAT translation entries for
unused addresses, and the router would never ARP for them. unused addresses, and the router would never ARP for them.
There are, however, many reasons to avoid using NAT in such a There are, however, many reasons to avoid using NAT in such a
blanket fashion. blanket fashion.
Stateful firewalls Stateful firewalls
Another obvious solution would be to put a stateful firewall Another obvious solution would be to put a stateful firewall
between the wireless network and the Internet. This firewall between the wireless network and the Internet. This firewall
would block incoming traffic not associated with an outbound would block incoming traffic not associated with an outbound
request. But this conflicts with the need and desire of some request. But this conflicts with the need and desire of some
organizations to have the network as open as possible and to organizations to have the network as open as possible and to
honor the end-to-end principle. An attendee on a meeting honor the end-to-end principle. An attendee on a meeting
network should be an Internet host, and should be able to network should be an Internet host and should be able to
receive unsolicited requests. Unfortunately, keeping the receive unsolicited requests. Unfortunately, keeping the
network working and stable is the first priority and a stateful network working and stable is the first priority, and a
firewall may be required in order to achieve this. stateful firewall may be required in order to achieve this.
5.2. Mitigating Spurious Service Discovery Messages 5.2. Mitigating Spurious Service Discovery Messages
In networks that must support hundreds of STAs, operators have In networks that must support hundreds of STAs, operators have
observed network degradation due to many devices simultaneously observed network degradation due to many devices simultaneously
registering with mDNS. In a network with many clients, it is registering with mDNS. In a network with many clients, it is
recommended to ensure that mDNS packets designed to discover services recommended to ensure that mDNS packets designed to discover services
in smaller home networks be constrained to avoid disrupting other in smaller home networks be constrained to avoid disrupting other
traffic. traffic.
skipping to change at page 18, line 43 skipping to change at line 871
Many of the causes of performance degradation described in earlier Many of the causes of performance degradation described in earlier
sections are also observable for wireless media other than 802.11. sections are also observable for wireless media other than 802.11.
For instance, problems with power save, excess media occupancy, and For instance, problems with power save, excess media occupancy, and
poor reliability will also affect 802.15.3 and 802.15.4. poor reliability will also affect 802.15.3 and 802.15.4.
Unfortunately, 802.15 media specifications do not yet include Unfortunately, 802.15 media specifications do not yet include
mechanisms similar to those developed for 802.11. In fact, the mechanisms similar to those developed for 802.11. In fact, the
design philosophy for 802.15 is oriented towards minimality, with the design philosophy for 802.15 is oriented towards minimality, with the
result that many such functions are relegated to operation within result that many such functions are relegated to operation within
higher layer protocols. This leads to a patchwork of non- higher-layer protocols. This leads to a patchwork of non-
interoperable and vendor-specific solutions. See [uli] for some interoperable and vendor-specific solutions. See [uli] for
additional discussion, and a proposal for a task group to resolve additional discussion and a proposal for a task group to resolve
similar issues, in which the multicast problems might be considered similar issues, in which the multicast problems might be considered
for mitigation. for mitigation.
Similar considerations hold for most other wireless media. A brief Similar considerations hold for most other wireless media. A brief
introduction is provided in [RFC5757] for the following: introduction is provided in [RFC5757] for the following:
* 802.16 WIMAX * 802.16 WiMAX
* 3GPP/3GPP2 * 3GPP/3GPP2
* DVB-H / DVB-IPDC
* DVB-H/DVB-IPDC
* TV Broadcast and Satellite Networks * TV Broadcast and Satellite Networks
7. Recommendations 7. Recommendations
This section provides some recommendations about the usage and This section provides some recommendations about the usage and
combinations of some of the multicast enhancements described in combinations of some of the multicast enhancements described in
Section 4 and Section 5. Sections 4 and 5.
Future protocol documents utilizing multicast signaling should be Future protocol documents utilizing multicast signaling should be
carefully scrutinized if the protocol is likely to be used over carefully scrutinized if the protocol is likely to be used over
wireless media. wireless media.
The use of proxy methods should be encouraged to conserve network The use of proxy methods should be encouraged to conserve network
bandwidth and power utilization by low-power devices. The device can 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 send a unicast message to its proxy, and then the proxy can take care
of any needed multicast operations. of any needed multicast operations.
Multicast signaling for wireless devices should be done in a way Multicast signaling for wireless devices should be done in a way that
compatible with low duty-cycle operation. is compatible with low duty-cycle operation.
8. On-going Discussion Items 8. Ongoing Discussion Items
This section suggests two discussion items for further resolution. This section suggests two discussion items for further resolution.
First, standards (and private) organizations should develop First, standards (and private) organizations should develop
guidelines to help clarify when multicast packets would be better guidelines to help clarify when multicast packets would be better
served by being sent wired rather than wireless. For example, served by being sent wired rather than wireless. For example,
802.1ak (https://www.ieee802.org/1/pages/802.1ak.html) works on both 802.1ak [IEEE802.1ak] works on both Ethernet and Wi-Fi, and
ethernet and Wi-Fi and organizations could help with deployment organizations could help with deployment decision making by
decision making by developing guidelines for multicast over Wi-Fi developing guidelines for multicast over Wi-Fi, including options for
including options for when traffic should be sent wired. when traffic should be sent wired.
Second, reliable registration to Layer-2 multicast groups, and a Second, reliable registration to Layer 2 multicast groups and a
reliable multicast operation at Layer-2, might provide a good reliable multicast operation at Layer 2 might provide a good
multicast over wifi solution. There shouldn't be a need to support multicast over Wi-Fi solution. There shouldn't be a need to support
2^24 groups to get solicited node multicast working: it is possible 2^24 groups to get solicited node multicast working: it is possible
to simply select a number of bits that make sense for a given network to simply select a number of bits that make sense for a given network
size to limit the number of unwanted deliveries to reasonable levels. size to limit the number of unwanted deliveries to reasonable levels.
IEEE 802.1, 802.11, and 802.15 should be encouraged to revisit L2 The IEEE 802.1, 802.11, and 802.15 Working Groups should be
multicast issues and provide workable solutions. encouraged to revisit Layer 2 multicast issues and provide workable
solutions.
9. Security Considerations 9. Security Considerations
This document does not introduce or modify any security mechanisms. This document does not introduce or modify any security mechanisms.
Multicast deployed on wired or wireless networks as discussed in this Multicast deployed on wired or wireless networks as discussed in this
document can be made more secure in a variety of ways. [RFC4601], document can be made more secure in a variety of ways. [RFC4601],
for instance, specifies the use of IPsec to ensure authentication of for instance, specifies the use of IPsec to ensure authentication of
the link-local messages in the Protocol Independent Multicast - the link-local messages in the Protocol Independent Multicast -
Sparse Mode (PIM-SM) routing protocol. [RFC5796]specifies mechanisms Sparse Mode (PIM-SM) routing protocol. [RFC5796] specifies
to authenticate the PIM-SM link-local messages using the IP security mechanisms to authenticate the PIM-SM link-local messages using the
(IPsec) Encapsulating Security Payload (ESP) or (optionally) the IP security (IPsec) Encapsulating Security Payload (ESP) or
Authentication Header (AH). (optionally) the Authentication Header (AH).
When using mechanisms that convert multicast traffic to unicast When using mechanisms that convert multicast traffic to unicast
traffic for traversing radio links, the AP (or other entity) is traffic for traversing radio links, the AP (or other entity) is
forced to explicitly track which subscribers care about certain forced to explicitly track which subscribers care about certain
multicast traffic. This is generally a reasonable tradeoff, but does multicast traffic. This is generally a reasonable trade-off but does
result in another entity that is tracking what entities subscribe to result in another entity that is tracking what entities subscribe to
which multicast traffic. While such information is already (by which multicast traffic. While such information is already (by
necessity) tracked elsewhere, this does present an expansion of the necessity) tracked elsewhere, this does present an expansion of the
attack surface for that potentially privacy-sensitive information. attack surface for that potentially privacy-sensitive information.
As noted in [group_key], the unreliable nature of multicast As noted in [group_key], the unreliable nature of multicast
transmission over wireless media can cause subtle problems with transmission over wireless media can cause subtle problems with
multicast group key management and updates. When WPA (TKIP) or WPA2 multicast group key management and updates. [group_key] states that
(AES-CCMP) encryption is in use, AP to client (From DS) multicasts when TKIP (WPA, now deprecated) or AES-CCMP (WPA2/WPA3) encryption is
have to be encrypted with a separate encryption key that is known to in use, AP-to-client (FromDS) multicasts have to be encrypted with a
all of the clients (this is called the Group Key). Quoting further separate encryption key that is known to all of the clients (this is
from that website, "... most clients are able to get connected and called the Group Key). Quoting further from that website, "... most
surf the web, check email, etc. even when From DS multicasts are clients are able to get connected and surf the web, check email, etc.
broken. So a lot of people don't realize they have multicast even when FromDS multicasts are broken. So a lot of people don't
problems on their network..." realize they have multicast problems on their network..."
This document encourages the use of proxy methods to conserve network This document encourages the use of proxy methods to conserve network
bandwidth and power utilization by low-power devices. Such proxy bandwidth and power utilization by low-power devices. Such proxy
methods in general have security considerations that require the methods in general have security considerations that require the
proxy to be trusted to not misbehave. One such proxy method listed proxy to be trusted to not misbehave. One such proxy method listed
is an Arp Sponge which listens for ARP requests, and, if it sees an is an ARP Sponge that listens for ARP requests, and, if it sees an
ARP for an IP address that it believes is not used, it will reply ARP for an IP address that it believes is not used, it will reply
with its own MAC address. ARP poisoning and false advertising could with its own MAC address. ARP poisoning and false advertising could
potentially undermine (e.g. DoS) this, and other, proxy approaches. potentially undermine (e.g., DoS) this and other proxy approaches.
10. IANA Considerations 10. IANA Considerations
This document does not request any IANA actions. This document has no IANA actions.
11. Acknowledgements
This document has benefitted from discussions with the following
people, in alphabetical order: Mikael Abrahamsson, Bill Atwood,
Stuart Cheshire, Donald Eastlake, Toerless Eckert, Jake Holland, Joel
Jaeggli, Jan Komissar, David Lamparter, Morten Pedersen, Pascal
Thubert, Jeffrey (Zhaohui) Zhang
12. Informative References 11. Informative References
[arpsponge] [arpsponge]
Wessel, M. and N. Sijm, "Effects of IPv4 and IPv6 address Wessel, M. and N. Sijm, "Effects of IPv4 and IPv6 address
resolution on AMS-IX and the ARP Sponge", July 2009, resolution on AMS-IX and the ARP Sponge", July 2009,
<http://citeseerx.ist.psu.edu/viewdoc/ <http://citeseerx.ist.psu.edu/viewdoc/
summary?doi=10.1.1.182.4692>. summary?doi=10.1.1.182.4692>.
[bridge-mc-2-uc] [bridge-mc-2-uc]
Fietkau, F., "bridge: multicast to unicast", January 2017, "bridge: multicast to unicast", commit 6db6f0e, January
<https://github.com/torvalds/linux/ 2017, <https://github.com/torvalds/linux/commit/6db6f0e>.
commit/6db6f0eae6052b70885562e1733896647ec1d807>.
[CAB] Fietkau, F., "Limit multicast buffer hardware queue [CAB] "limit multicast buffer hardware queue depth", commit
depth", 2013, 2687951, June 2013,
<https://patchwork.kernel.org/patch/2687951/>. <https://patchwork.kernel.org/patch/2687951/>.
[Deri-2010] [Deri-2010]
Deri, L. and J. Gasparakis, "10 Gbit Hardware Packet Deri, L. and J. Gasparakis, "10 Gbit Hardware Packet
Filtering Using Commodity Network Adapters", RIPE 61, Filtering Using Commodity Network Adapters", RIPE 61,
2010, <http://ripe61.ripe.net/ November 2010, <http://ripe61.ripe.net/
presentations/138-Deri_RIPE_61.pdf>. presentations/138-Deri_RIPE_61.pdf>.
[dot11] "IEEE 802 Wireless", "802.11-2016 - IEEE Standard for [dot11] IEEE, "Information Technology--Telecommunications and
Information technology--Telecommunications and information Information Exchange between Systems - Local and
exchange between systems Local and metropolitan area Metropolitan Area Networks--Specific Requirements - Part
networks--Specific requirements - Part 11: Wireless LAN 11: Wireless LAN Medium Access Control (MAC) and Physical
Medium Access Control (MAC) and Physical Layer (PHY) Layer (PHY) Specifications (includes 802.11v amendment)",
Specification (includes 802.11v amendment)", March 2016, DOI 10.1109/IEEESTD.2021.9363693, IEEE Std 802.11-2020,
<http://standards.ieee.org/findstds/ December 2020,
standard/802.11-2016.html>. <https://standards.ieee.org/standard/802_11-2020.html>.
[dot11-proxyarp] [dot11-proxyarp]
Hiertz, G. R., Mestanov, F., and B. Hart, "Proxy ARP in Hiertz, G., Mestanov, F., and B. Hart, "Proxy ARP in
802.11ax", September 2015, 802.11ax", September 2015,
<https://mentor.ieee.org/802.11/dcn/15/11-15-1015-01-00ax- <https://mentor.ieee.org/802.11/dcn/15/11-15-1015-01-00ax-
proxy-arp-in-802-11ax.pptx>. proxy-arp-in-802-11ax.pptx>.
[dot11aa] "IEEE 802 Wireless", "Part 11: Wireless LAN Medium Access [dot11aa] IEEE, "Information technology--Telecommunications and
Control (MAC) and Physical Layer (PHY) Specifications information exchange between systems Local and
Amendment 2: MAC Enhancements for Robust Audio Video metropolitan area networks--Specific requirements Part 11:
Streaming", March 2012, Wireless LAN Medium Access Control (MAC) and Physical
Layer (PHY) Specifications Amendment 2: MAC Enhancements
for Robust Audio Video Streaming",
DOI 10.1109/IEEESTD.2012.6204193, IEEE Std 802.11aa-2012,
March 2012,
<https://standards.ieee.org/standard/802_11aa-2012.html>. <https://standards.ieee.org/standard/802_11aa-2012.html>.
[group_key] [group_key]
Spiff, "Why do some WiFi routers block multicast packets "Subject: Why do some WiFi routers block multicast packets
going from wired to wireless?", January 2017, going from wired to wireless?", message to the Super User
Q & A community, January 2017,
<https://superuser.com/questions/730288/why-do-some-wifi- <https://superuser.com/questions/730288/why-do-some-wifi-
routers-block-multicast-packets-going-from-wired-to- routers-block-multicast-packets-going-from-wired-to-
wireless>. wireless>.
[I-D.ietf-6lo-backbone-router] [IEEE802.1ak]
Thubert, P., Perkins, C. E., and E. Levy-Abegnoli, "IPv6 IEEE, "Local and Metropolitan Area Networks Virtual
Backbone Router", Work in Progress, Internet-Draft, draft- Bridged Local Area Networks - Amendment 07: Multiple
ietf-6lo-backbone-router-20, 23 March 2020, Registration Protocol", DOI 10.1109/IEEESTD.2007.380667,
<https://www.ietf.org/archive/id/draft-ietf-6lo-backbone- IEEE Std 802.1ak-2007, June 2007,
router-20.txt>. <https://www.ieee802.org/1/pages/802.1ak.html>.
[I-D.ietf-6tisch-architecture]
Thubert, P., "An Architecture for IPv6 over the Time-
Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)",
Work in Progress, Internet-Draft, draft-ietf-6tisch-
architecture-30, 26 November 2020,
<https://www.ietf.org/archive/id/draft-ietf-6tisch-
architecture-30.txt>.
[I-D.ietf-mboned-driad-amt-discovery]
Holland, J., "DNS Reverse IP Automatic Multicast Tunneling
(AMT) Discovery", Work in Progress, Internet-Draft, draft-
ietf-mboned-driad-amt-discovery-13, 20 December 2019,
<https://www.ietf.org/archive/id/draft-ietf-mboned-driad-
amt-discovery-13.txt>.
[ietf_802-11] [ietf_802-11]
Stanley, D., "IEEE 802.11 multicast capabilities", Stanley, D., "IEEE 802.11 multicast capabilities",
November 2015, <https://mentor.ieee.org/802.11/ November 2015, <https://mentor.ieee.org/802.11/
dcn/15/11-15-1261-03-0arc-multicast-performance- dcn/15/11-15-1261-03-0arc-multicast-performance-
optimization-features-overview-for-ietf-nov-2015.ppt>. optimization-features-overview-for-ietf-nov-2015.ppt>.
[mc-ack-mux]
Tanaka, Y., Sakai, E., Morioka, Y., Mori, M., Hiertz, G.,
and S. Coffey, "Multiplexing of Acknowledgements for
Multicast Transmission", July 2015,
<https://mentor.ieee.org/802.11/dcn/15/11-15-0800-00-00ax-
multiplexing-of-acknowledgements-for-multicast-
transmission.pptx>.
[mc-prob-stmt] [mc-prob-stmt]
Abrahamsson, M. and A. Stephens, "Multicast on 802.11", Abrahamsson, M. and A. Stephens, "Multicast on 802.11",
March 2015, <https://www.iab.org/wp-content/IAB- 2013, <https://www.iab.org/wp-content/IAB-uploads/2013/01/
uploads/2013/01/multicast-problem-statement.pptx>. multicast-problem-statement.pptx>.
[mc-props] Stephens, A., "IEEE 802.11 multicast properties", March [mc-props] Stephens, A., "IEEE 802.11 multicast properties",
2015, <https://mentor.ieee.org/802.11/ September 2015, <https://mentor.ieee.org/802.11/
dcn/15/11-15-1161-02-0arc-802-11-multicast- dcn/15/11-15-1161-02-0arc-802-11-multicast-
properties.ppt>. properties.ppt>.
[Oliva2013] [Oliva2013]
de la Oliva, A., Serrano, P., Salvador, P., and A. Banchs, de la Oliva, A., Serrano, P., Salvador, P., and A. Banchs,
"Performance evaluation of the IEEE 802.11aa multicast "Performance evaluation of the IEEE 802.11aa multicast
mechanisms for video streaming", 2013 IEEE 14th mechanisms for video streaming", 2013 IEEE 14th
International Symposium on "A World of Wireless, Mobile International Symposium on "A World of Wireless, Mobile
and Multimedia Networks" (WoWMoM) pp. 1-9, June 2013. and Multimedia Networks" (WoWMoM), pp. 1-9,
DOI 10.1109/WoWMoM.2013.6583394, June 2013,
<https://doi.org/10.1109/WoWMoM.2013.6583394>.
[RFC0826] Plummer, D., "An Ethernet Address Resolution Protocol: Or [RFC0826] Plummer, D., "An Ethernet Address Resolution Protocol: Or
Converting Network Protocol Addresses to 48.bit Ethernet Converting Network Protocol Addresses to 48.bit Ethernet
Address for Transmission on Ethernet Hardware", STD 37, Address for Transmission on Ethernet Hardware", STD 37,
RFC 826, DOI 10.17487/RFC0826, November 1982, RFC 826, DOI 10.17487/RFC0826, November 1982,
<https://www.rfc-editor.org/info/rfc826>. <https://www.rfc-editor.org/info/rfc826>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", [RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, DOI 10.17487/RFC2131, March 1997, RFC 2131, DOI 10.17487/RFC2131, March 1997,
<https://www.rfc-editor.org/info/rfc2131>. <https://www.rfc-editor.org/info/rfc2131>.
skipping to change at page 24, line 10 skipping to change at line 1096
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007, DOI 10.17487/RFC4861, September 2007,
<https://www.rfc-editor.org/info/rfc4861>. <https://www.rfc-editor.org/info/rfc4861>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007, DOI 10.17487/RFC4862, September 2007,
<https://www.rfc-editor.org/info/rfc4862>. <https://www.rfc-editor.org/info/rfc4862>.
[RFC5424] Gerhards, R., "The Syslog Protocol", RFC 5424,
DOI 10.17487/RFC5424, March 2009,
<https://www.rfc-editor.org/info/rfc5424>.
[RFC5757] Schmidt, T., Waehlisch, M., and G. Fairhurst, "Multicast [RFC5757] Schmidt, T., Waehlisch, M., and G. Fairhurst, "Multicast
Mobility in Mobile IP Version 6 (MIPv6): Problem Statement Mobility in Mobile IP Version 6 (MIPv6): Problem Statement
and Brief Survey", RFC 5757, DOI 10.17487/RFC5757, and Brief Survey", RFC 5757, DOI 10.17487/RFC5757,
February 2010, <https://www.rfc-editor.org/info/rfc5757>. February 2010, <https://www.rfc-editor.org/info/rfc5757>.
[RFC5796] Atwood, W., Islam, S., and M. Siami, "Authentication and [RFC5796] Atwood, W., Islam, S., and M. Siami, "Authentication and
Confidentiality in Protocol Independent Multicast Sparse Confidentiality in Protocol Independent Multicast Sparse
Mode (PIM-SM) Link-Local Messages", RFC 5796, Mode (PIM-SM) Link-Local Messages", RFC 5796,
DOI 10.17487/RFC5796, March 2010, DOI 10.17487/RFC5796, March 2010,
<https://www.rfc-editor.org/info/rfc5796>. <https://www.rfc-editor.org/info/rfc5796>.
skipping to change at page 25, line 23 skipping to change at line 1154
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 8415, DOI 10.17487/RFC8415, November 2018, RFC 8415, DOI 10.17487/RFC8415, November 2018,
<https://www.rfc-editor.org/info/rfc8415>. <https://www.rfc-editor.org/info/rfc8415>.
[RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C.
Perkins, "Registration Extensions for IPv6 over Low-Power Perkins, "Registration Extensions for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Neighbor Wireless Personal Area Network (6LoWPAN) Neighbor
Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018,
<https://www.rfc-editor.org/info/rfc8505>. <https://www.rfc-editor.org/info/rfc8505>.
[RFC8777] Holland, J., "DNS Reverse IP Automatic Multicast Tunneling
(AMT) Discovery", RFC 8777, DOI 10.17487/RFC8777, April
2020, <https://www.rfc-editor.org/info/rfc8777>.
[RFC8929] Thubert, P., Ed., Perkins, C.E., and E. Levy-Abegnoli,
"IPv6 Backbone Router", RFC 8929, DOI 10.17487/RFC8929,
November 2020, <https://www.rfc-editor.org/info/rfc8929>.
[RFC9030] Thubert, P., Ed., "An Architecture for IPv6 over the Time-
Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)",
RFC 9030, DOI 10.17487/RFC9030, May 2021,
<https://www.rfc-editor.org/info/rfc9030>.
[Tramarin2017] [Tramarin2017]
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Acknowledgements
This document has benefitted from discussions with the following
people, in alphabetical order: Mikael Abrahamsson, Bill Atwood,
Stuart Cheshire, Donald Eastlake 3rd, Toerless Eckert, Jake Holland,
Joel Jaeggli, Jan Komissar, David Lamparter, Morten Pedersen, Pascal
Thubert, and Jeffrey (Zhaohui) Zhang.
Authors' Addresses Authors' Addresses
Charles E. Perkins Charles E. Perkins
Blue Meadow Networks Lupin Lodge
Phone: +1-408-330-4586 Phone: +1 408 255 9223
Email: charliep@computer.org Email: charliep@lupinlodge.com
Mike McBride Mike McBride
Futurewei Technologies Inc. Futurewei Technologies Inc.
2330 Central Expressway 2330 Central Expressway
Santa Clara, CA 95055 Santa Clara, CA 95055
United States of America United States of America
Email: michael.mcbride@futurewei.com Email: michael.mcbride@futurewei.com
Dorothy Stanley Dorothy Stanley
Hewlett Packard Enterprise Hewlett Packard Enterprise
2000 North Naperville Rd. 6280 America Center Dr.
Naperville, IL 60566 San Jose, CA 95002
United States of America United States of America
Phone: +1 630 979 1572 Phone: +1 630 363 1389
Email: dstanley1389@gmail.com Email: dorothy.stanley@hpe.com
Warren Kumari Warren Kumari
Google Google
1600 Amphitheatre Parkway 1600 Amphitheatre Parkway
Mountain View, CA 94043 Mountain View, CA 94043
United States of America United States of America
Email: warren@kumari.net Email: warren@kumari.net
Juan Carlos Zuniga Juan Carlos Zúñiga
SIGFOX SIGFOX
425 rue Jean Rostand Montreal
31670 Labege Canada
France
Email: j.c.zuniga@ieee.org Email: j.c.zuniga@ieee.org
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