One document matched: draft-perkins-intarea-multicast-ieee802-00.xml
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<rfc ipr="trust200902"
docName='draft-perkins-intarea-multicast-ieee802-00.txt' >
<front>
<title abbrev="Multicast Over IEEE 802 Wireless">
Multicast Considerations over IEEE 802 Wireless Media</title>
<author fullname="Charles E. Perkins" initials="C.E." surname="Perkins">
<organization abbrev="Futurewei">Futurewei Inc. </organization>
<address>
<postal>
<street>2330 Central Expressway</street>
<city>Santa Clara</city>
<code>95050</code>
<region>CA</region>
<country>USA</country>
</postal>
<phone>+1-408-330-4586</phone>
<email>charliep@computer.org</email>
</address>
</author>
<author fullname="Dorothy Stanley" initials="D" surname="Stanley">
<organization abbrev="HPE">Hewlett Packard Enterprise </organization>
<address>
<postal>
<street>2000 North Naperville Rd.</street>
<city>Naperville</city>
<code>60566</code>
<region>IL</region>
<country>USA</country>
</postal>
<phone>+1 630 979 1572</phone>
<email>dstanley@arubanetworks.com</email>
</address>
</author>
<author fullname="Warren Kumari" initials="W" surname="Kumari">
<organization abbrev="Google">Google </organization>
<address>
<postal>
<street>1600 Amphitheatre Parkway</street>
<city>Mountain View</city>
<code>94043</code>
<region>CA</region>
<country>USA</country>
</postal>
<email>warren@kumari.net</email>
</address>
</author>
<author fullname="Juan Carlos Zuniga" initials="JC" surname="Zuniga">
<organization abbrev="InterDigital">InterDigital </organization>
<address>
<postal>
<street>1000 Sherbrooke W, 10th Floor</street>
<city>Montreal</city>
<code>H3A 3G4</code>
<region>QC</region>
<country>Canada</country>
</postal>
<email>j.c.zuniga@ieee.org</email>
</address>
</author>
<date/> <!-- day="25" month="October" year="2010" /> -->
<area>Routing</area>
<workgroup>Internet Area [intarea]</workgroup>
<keyword>Multicast</keyword>
<keyword>IEEE 802 Wireless</keyword>
<abstract>
<t>
This document describes some performance issues that have been observed
when multicast packet transmission is attempted over IEEE 802 wireless
media. Multicast features specified for IEEE 802 wireless media
related to multicast are also described, along with explanations about
how these features can help ameliorate the observed performance issues.
IETF protocols that are likely to be affected by the observed
performance issues are identified, and workarounds are proposed
in some cases.
The performance of multicast over wireless media often can be quite
different than the performance of unicast. This draft describes the
nature of the differences and the effects on representative IETF
protocols. We also describe some efforts that have been made by
IEEE 802 Wireless groups to ameliorate the performance differences.
</t>
</abstract>
</front>
<middle>
<section anchor='intro' title='Introduction'>
<t>
Many IETF protocol designs depend upon multicast or broadcast for delivery
of control messages to multiple receivers. Multicast is used for various
purposes such as neighborhood discovery, network flooding, address resolution,
as well as reduction in media access for data traffic.
</t>
<t>
IETF protocols typically expect to rely on network protocol layering in
order to reduce or eliminate any dependence of higher level protocols on
the specific nature of the MAC layer protocols or the physical media.
In the case of multicast transmission, higher level protocols may be designed
as if transmitting a packet to an IP address has the same cost in
interference and network media access, regardless of whether the destination
IP address is a unicast address or a multicast or broadcast address.
This model of operation was reasonable for networks where the physical
medium was like an Ethernet.
</t>
<t>
Unfortunately, for many wireless media, the costs can be quite different.
It is the purpose of this Internet Draft to identify the ways in which the
costs can be different. Using this information, we then proceed to identify
some possible effects on the actual operation of IETF protocols over
wireless media.
</t>
<t>
IEEE 802 Wireless working groups, especially 802.11, have made a number
of attempts to improve the performance of multicast transmissions at layer 2.
In this draft we also include a description of some of these efforts. This
information is closely related to material presented at IETF 94
[cite 11-15-1261-03]
</t>
</section>
<section anchor='def' title="Terminology">
<!--
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
"MAY", and "OPTIONAL" in this document are to be interpreted as
described in <xref target="RFC2119" />.</t>
<t>This document also uses some terminology from <xref
target="RFC5444" />.</t>
-->
<t>This document defines the following terminology:</t>
<t><list style="hanging">
<t hangText="basic rate"><vspace />
a "lowest common denominator" rate at which multicast
and broadcast traffic is generally transmitted.</t>
<t><vspace /></t>
<t hangText="MCS"><vspace />
Modulation and Coding Scheme.</t>
<t><vspace /></t>
</list></t>
<!-- <t><vspace blankLines="19" /></t> -->
</section>
<section anchor='layer2' title='Identified Issues at Layer 2'>
<t>
In this section we list some of the issues arising at layer 2
surrounding the use of multicast in IETF protocols over wireless media.
</t>
<t>
<list style="symbols">
<t> Multicast traffic is typically much less reliable than unicast traffic.
</t>
<t> Multicast / broadcast traffic is generally sent at a lowest common
denominator rate, known as a basic rate. This might be as low
as 6 Mbps, when unicast links are operating at 600 Mbps.
Transmission at a lower rate requires more occupancy of the wireless
medium and thus less airtime for everything else.</t>
<t> Wireless multicast affects wired LANs because the AP
extends the wired segment.
<list style="symbols">
<t> All broadcast frames on LAN side are copied to WLAN.</t>
<t> In WLAN, broadcast messages transmitted at most robust MCS.</t>
<t> Most robust MCS implies large frames sent at slow rate.</t>
</list></t>
<t> Multicast can work poorly with the power-save mechanisms in 802.11.
<list style="symbols">
<t> Both unicast and multicast traffic can be delayed by power-saving
mechanisms.</t>
<t> Unicast is delayed until a STA wakes up and asks for it.
Additionally, unicast traffic may be delayed to improve power save,
efficiency and increase probability of aggregation.</t>
<t> Multicast traffic is delayed in a wireless network if any of the STAs
in that network are power savers. All STAs have to be awake at a
known time to receive multicast traffic.</t>
<t> Packets can also be discarded due to buffer limitations in the AP
and non-AP STA.</t>
</list></t>
</list>
</t>
</section>
<section anchor='ietf-effects'
title='Some Possible Effects on Representative IETF protocols'>
<t>
In this section we list some of the issues arising at layer 3
surrounding the use of multicast in IETF protocols over wireless media.
We mention a few representative IETF protocols, and
describe some possible effects due to performance degradation when
using multicast transmissions for control messages. Common uses include:
<list style="symbols">
<t> Control plane for IPv4 and IPv6 </t>
<t> ARP and Neighbor Discovery </t>
<t> Service discovery </t>
<t> Applications (video delivery, stock data etc) </t>
<t> Other L3 protocols (non-IP) </t>
</list>
</t>
<section anchor='IPv4' title='IPv4 uses'>
<t>
The following list contains a few representative IPv4 protocols using
multicast.
<list style="symbols">
<t> ARP </t>
<t> DHCP </t>
<t> mDNS </t>
</list>
After initial configuration, ARP and DHCP occur much less commonly.
</t>
</section> <!-- 'IPv4 uses' -->
<section anchor='IPv6' title='IPv6 uses'>
<t>
The following list contains a few representative IPv6 protocols
using multicast. IPv6 makes much more extensive use of multicast.
<list style="symbols">
<t> DHCPv6 </t>
<t> Liveness detection (NUD) </t>
<t> Some control plane protocols are not very tolerant of packet
loss, especially neighbor discovery.</t>
<t> Services may be considered lost if several consecutive
packets fail.</t>
</list>
</t>
<t>Address Resolution</t>
<t>Service Discovery</t>
<t>Route Discovery</t>
<t>Decentralized Address Assignment</t>
<t>Geographic routing</t>
</section> <!-- 'IPv6 uses' -->
<section anchor='mld' title='Disabling Multicast on WiFi'>
<t>
Multicast Listener Discovery(MLD) <xref target="RFC4541" /> is
often used to identify members of a multicast group that are connected
to the ports of a switch. Forwarding multicast frames into a
WiFi-enabled area can use such switch support for hardware forwarding
state information. However, since IPv6 makes heavy use of multicast,
each STA with an IPv6 address will require state on the switch for
several and possibly many multicast solicited-node addresses.
Multicast addresses that do not have forwarding state installed
(perhaps due to hardware memory limitations on the switch) cause
frames to be flooded on all ports of the switch.
</t>
</section> <!-- 'Disabling Multicast on WiFi' -->
<section anchor='spurious ' title='Spurious Neighbor Discovery'>
<t>
On the Internet there is a "background radiation" of scanning
traffic (people scanning for vulnerable machines) and backscatter
(responses from spoofed traffic, etc). This means that the router
is constantly getting packets destined for machines whose IP addresses
may or may not be in use. In the cases where the IP is assigned to a
machine, the router broadcasts an ARP request, gets back an ARP reply,
caches this and then can deliver traffic to the host. In the cases
where 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 not
populate the ARP cache, and the next time there is traffic for that
IP address it will broadcast ARP requests again. The rate of these
ARP requests is proportional to the size of the subnets, the rate of
scanning and backscatter, and how long the router keeps state on
non-responding ARPs. As it turns out, this rate
is inversely proportional to how occupied the subnet is (valid ARPs
end up in a cache, stopping the broadcasting; unused IPs never respond,
and so cause more broadcasts). Depending on the address space in use,
the time of day, how occupied the subnet is, and other unknown factors,
on the order of 2000 broadcasts per second have been observed
at the IETF NOCs.
</t>
<t>
On a wired network, there is not a huge difference amongst unicast,
multicast and broadcast traffic; but this is not true in the wireless
realm. Wireless equipment often is unable to send this
amount of broadcast and multicast traffic. Consequently, on the
wireless networks, we observe a significant amount of dropped
broadcast and multicast packets. This, in turn, means that when
a host connects it is often not able to complete DHCP, and IPv6 RAs
get dropped, leading to users being unable to use the network.
</t>
</section> <!-- 'layer3' title='Spurious Neighbor Discovery' -->
</section> <!-- 'Some Possible Effects on Representative IETF protocols' -->
<section anchor='optim2' title='Layer 2 optimizations'>
<t>
This section lists some optimizations that have been specified for
use with 802.11 that are aimed at reducing or eliminating the
causes of performance loss discussed in
section <xref target="layer2"/>.
</t>
<section anchor='proxy-arp' title='Proxy ARP in 802.11-2012'>
<t>
The AP knows all associated STAs MAC address and IP address;
in other words, the AP acts as the central "manager" for all the
802.11 STAs in its BSS. Proxy ARP is easy to implement at the AP,
and offers the following advantages:
<list style="symbols">
<t> Reduced broadcast traffic (transmitted at low MCS) on
the wireless medium </t>
<t> STA benefits from extended power save in sleep mode,
as ARP requests are replied to by AP. </t>
<t> Keeps ARP frames off the wireless medium. </t>
</list>
</t>
<t> Here is the specification language from clause 10.23.13 in [2]
as described in <xref target="dot11-proxyarp"/>:
<list style="empty">
<t> When the AP supports Proxy ARP "[...] the AP shall maintain a
Hardware Address to Internet Address mapping for each associated
station, and shall update the mapping when the Internet Address of
the associated station changes. When the IPv4 address being
resolved in the ARP request packet is used by a non-AP STA
currently associated to the BSS, the proxy ARP service shall
respond on behalf of the non-AP STA" </t>
</list>
</t>
</section>
<section anchor='buffer' title='Buffering to improve Power-Save'>
<t>
The AP acts on behalf of STAs in various ways. In order to
improve the 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 reception.
</t>
</section> <!-- 'Buffering to improve Power-Save' -->
<section anchor='ipv6' title='IPv6 support in 802.11-2012'>
<t> IPv6 uses Neighbor Discovery Protocol (NDP) instead
Every IPv6 node subscribes to special multicast address
Neighbor-Solicitation message replaces ARP
</t>
<t> Here is the specification language from-10.23.13 in [2]:
<list style="empty">
<t> "When an IPv6 address is being resolved, the Proxy Neighbor
Discovery service shall respond with a Neighbor Advertisement
message [...] on behalf of an associated STA to an [ICMPv6]
Neighbor Solicitation message [...]. When MAC address mappings
change, the AP may send unsolicited Neighbor Advertisement
Messages on behalf of a STA." </t>
</list> </t>
<t> NDP may be used to request additional information
<list style="symbols">
<t> Maximum Transmission Unit </t>
<t> Router Solicitation </t>
<t> Router Advertisement, etc. </t>
</list>
NDP messages are sent as group addressed (broadcast) frames in 802.11.
Using the proxy operation helps to keep NDP messages off the wireless
medium. </t>
</section> <!-- 'IPv6 support in 802.11-2012' -->
<section anchor='DMS' title='Directed Multicast Service (DMS)'>
<t> DMS enables a client to request that the AP transmit multicast
group addressed frames destined to the requesting clients as
individually addressed frames [i.e., convert multicast to unicast].
<list style="symbols">
<t> DMS Requires 802.11n A-MSDUs </t>
<t> Individually addressed frames are acknowledged and are
buffered for power save clients </t>
<t> Requesting STA may specify traffic characteristics for DMS
traffic</t>
<t> DMS was defined in IEEE Std 802.11v-2011 </t>
</list>
DMS is not currently implemented in products.
</t>
</section> <!-- 'Directed Multicast Service (DMS)' -->
<section anchor='GCR' title='GroupCast with Retries (GCR)'>
<t> GCR (defined in <xref target="dot11aa"/>) provides greater
reliability by using either unsolicited
retries or a block acknowledgement mechanism.
GCR increases probability of broadcast frame reception success,
but still does not guarantee success.
</t>
<t> For the block acknowledgement mechanism, the AP transmits each
group addressed frame as conventional group addressed transmission.
Retransmissions are group addressed, but hidden from non-11aa
clients. A directed block acknowledgement scheme is used to
harvest reception status from receivers; retransmissions are
based upon these responses.
</t>
<t> 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 acknowledgement requests to only a small subset of the
group.
</t>
<t> GCR may introduce unacceptable latency. After sending a group
of data frames to the group, the AP has do the following:
<list style="symbols">
<t> unicast a Block Ack Request (BAR) to a subset of members.</t>
<t> wait for the corresponding Block Ack (BA).</t>
<t> retransmit any missed frames.</t>
<t> resume other operations which may have been delayed.</t>
</list>
This latency may not be acceptable for some traffic.
</t>
<t> There are ongoing extensions in 802.11 to improve GCR performance.
<list style="symbols">
<t> BAR is sent using downlink MU-MIMO (note that downlink MU-MIMO
is already specified in 802.11-REVmc 4.3).</t>
<t> BA is sent using uplink MU-MIMO (which is a .11ax feature).</t>
<t> Additional 802.11ax extensions are under consideration;
see <xref target="mc-ack-mux" /></t>
<t> Latency may also be reduced by simultaneously receiving BA
information from multiple clients.</t>
</list>
</t>
</section> <!-- 'GroupCast with Retries (GCR)' -->
</section> <!-- 'Layer 2 optimizations' -->
<section anchor='optim3' title='Higher Layer Optimizations and Mitigations'>
<t>
This section lists some optimizations that have been specified for
use with 802.11 that are aimed at reducing or eliminating the
causes of performance loss discussed in
section <xref target="optim3"/>.
</t>
<section anchor='mitigate-spurious'
title='Mitigating Problems from Spurious Neighbor Discovery'>
<t>
<list style="hanging" hangIndent="6">
<t hangText="ARP Sponges"><vspace blankLines="1"/>
ARP Sponges sit on a network and learn what IPs addresses are
actually in use. They also listen for ARP requests, and, if it
sees an ARP for an IP address which it believes is not used, 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 IP is
later assigned to an machine (e.g using DHCP), the ARP sponge
will see this, and will stop replying for that address.
Gratuitous ARPs (or the machine ARPing for its gateway) will
replace the sponged address in the router ARP table. This
technique is quite effective; but, unfortunately, the ARP
sponge daemons were not really designed for this use (the
standard one <xref target="arpsponge" />, was designed to deal
with the disappearance of participants from an IXP)
and so are not optimized for this purpose. We have to run one
daemon per subnet, the tuning is tricky (the scanning rate
versus the population rate versus retires, etc.) and sometimes
the daemons just seem to stop, requiring a restart of the
daemon and causing disruption.
<vspace blankLines="1"/>
</t>
<t hangText="Router mitigations"><vspace blankLines="1"/>
Some routers (often those based on Linux) implement a
"negative ARP cache" daemon. Simply put, if the router does
not see a reply to an ARP it can be configured to cache this
information for some interval. Unfortunately, the core routers
which we are using do not support this. When a host connects
to network and gets an IP address, it will ARP for its default
gateway (the router). The router will update its cache with
the IP to host MAC mapping learnt from the request (passive
ARP learning).
<vspace blankLines="1"/></t>
<t hangText="Firewall unused space"><vspace blankLines="1"/>
The distribution of users on wireless networks / subnets changes
from meeting to meeting (e.g the "IETF-secure" SSID was renamed
to "IETF", fewer users use "IETF-legacy", etc). This utilization
is difficult to predict ahead of time, but we can monitor the
usage as attendees use the different networks. By configuring
multiple DHCP pools per subnet, and enabling them sequentially,
we can have a large subnet, but only assign addresses from the
lower portions of it. This means that we can apply input IP
access lists, which deny traffic to the upper, unused portions.
This means that the router does not attempt to forward packets
to the unused portions of the subnets, and so does not ARP for it.
This method has proven to be very effective, but is somewhat of a
blunt axe, is fairly labor intensive, and requires coordination.
<vspace blankLines="1"/></t>
<t hangText="Disabling/filtering ARP requests"><vspace blankLines="1"/>
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 the ARP
request sent by that host. This means that we should be able to
disable and / or filter ARP requests from the router.
Unfortunately, ARP is a very low level / fundamental part of the
IP stack, and is often offloaded from the normal control plane.
While many routers can filter layer-2 traffic, this is usually
implemented as an input filter and / or has limited ability to
filter output broadcast traffic. This means that the simple
"just disable ARP or filter it outbound" seems like a really
simple (and obvious) solution, but implementations / architectural
issues make this difficult or awkward in practice.
<vspace blankLines="1"/>
</t>
<t hangText="NAT"><vspace blankLines="1"/>
The broadcasts are overwhelmingly being caused by outside
scanning / backscatter traffic. This means that, if we were to
NAT the entire (or a large portion) of the attendee networks,
there would be no NAT translation entries for unused addresses,
and so the router would never ARP for them. The IETF NOC has
discussed NATing the entire (or large portions) attendee address
space, but a: elegance and b: flaming torches and pitchfork
concerns means we have not attempted this yet.
<vspace blankLines="1"/>
</t>
<t hangText="Stateful firewalls"><vspace blankLines="1"/>
Another obvious solution would be to put a stateful firewall
between the wireless network and the Internet. This firewall
would block incoming traffic not associated with an outbound
request. The IETF philosophy has been to have the network as
open as possible / honor the end-to-end principle. An attendee
on the meeting network should be an Internet host, and should
be able to receive unsolicited requests.
Unfortunately, keeping the network working and
stable is the first priority and a stateful firewall may
be required in order to achieve this.
</t>
</list>
</t>
</section> <!-- 'Mitigating Problems from Spurious Neighbor Discovery' -->
</section> <!-- 'Layer 3 optimizations' -->
<section anchor='other-media'
title='Multicast Considerations for Other Wireless Media'>
<t>
Many of the causes of performance degradation described in earlier
sections are also observable for wireless media other than 802.11.
</t>
<t>
For instance, problems with power save, excess media occupancy,
and poor reliability will also affect 802.15.3 and 802.15.4.
However, 802.15 media specifications do not include similar
mechanisms of the type that have been developed for 802.11.
In fact, the design philosophy for 802.15 is more oriented
towards minimality, with the result that many such functions
would more likely be relegated to operation within higher layer
protocols. This leads to a patchwork of non-interoperable
and vendor-specific solutions. See <xref target="uli" /> for
some additional discussion, and a proposal for a task group
to resolve similar issues, in which the multicast problems
might be considered for mitigation.
</t>
</section> <!-- 'Multicast Considerations for Other Wireless Media' -->
<section anchor='sec' title='Security Considerations'>
<t>
This document does not introduce any security mechanisms,
and does not have any impact on existing security mechanisms.
</t>
</section>
<section anchor='iana' title='IANA Considerations'>
<t>
This document does not specify any IANA actions.
</t>
</section>
</middle>
<back>
<references title="Informative References">
<!-- <?rfc include='reference.RFC.2119.xml'?> -->
<?rfc include='reference.RFC.4541.xml'?>
<reference anchor="uli">
<front>
<title>LLC Proposal for 802.15.4</title>
<author surname="Pat Kinney">
<organization> "IEEE 802 Wireless"</organization>
<address>
<uri>https://mentor.ieee.org/802.15/dcn/15/15-15-0521-01-wng0-llc-proposal-for-802-15-4.pptx</uri>
</address>
</author>
<date month="Nov" year="2015"/>
</front>
</reference>
<reference anchor="mc-ack-mux">
<front>
<title>Multiplexing of Acknowledgements for Multicast Transmission</title>
<author surname="Yusuke Tanaka et al.">
<organization> "IEEE 802 Wireless"</organization>
<address>
<uri>https://mentor.ieee.org/802.11/dcn/15/11-15-0800-00-00ax-multiplexing-of-acknowledgements-for-multicast-transmission.pptx</uri>
</address>
</author>
<date month="July" year="2015"/>
</front>
</reference>
<reference anchor="dot11">
<front>
<title> Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) Specifications</title>
<author surname="P802.11">
<organization> "IEEE 802 Wireless" </organization>
<address>
<uri>http://standards.ieee.org/getieee802/download/802.11-2012.pdf (includes 802.11v amendment)</uri>
</address>
</author>
<date month="March" year="2012"/>
</front>
</reference>
<reference anchor="mc-props">
<front>
<title>IEEE 802.11 multicast properties</title>
<author surname="Adrian Stephens">
<organization> "IEEE 802 Wireless" </organization>
<address>
<uri>https://mentor.ieee.org/802.11/dcn/15/11-15-1161-02-0arc-802-11-multicast-properties.ppt</uri>
</address>
</author>
<date month="March" year="2015"/>
</front>
</reference>
<reference anchor="arpsponge">
<front>
<title>Arp Sponge</title>
<author surname="Arien Vijn, Steven Bakker">
<organization> "AMS" </organization>
<address>
<uri>https://ams-ix.net/downloads/arpsponge/3.12.2/arpsponge-3.12.2/arpsponge.txt</uri>
</address>
</author>
<date month="March" year="2015"/>
</front>
</reference>
<reference anchor="dot11-proxyarp">
<front>
<title>Proxy ARP in 802.11ax</title>
<author surname="P802.11">
<organization> "IEEE 802 Wireless" </organization>
<address>
<uri>https://mentor.ieee.org/802.11/dcn/15/11-15-1015-01-00ax-proxy-arp-in-802-11ax.pptx</uri>
</address>
</author>
<date month="September" year="2015"/>
</front>
</reference>
<reference anchor="dot11aa">
<front>
<title> Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) Specifications
Amendment 2: MAC Enhancements for
Robust Audio Video Streaming</title>
<author surname="P802.11">
<organization> "IEEE 802 Wireless" </organization>
<address>
<uri>http://standards.ieee.org/getieee802/download/802.11aa-2012.pdf</uri>
</address>
</author>
<date month="March" year="2012"/>
</front>
</reference>
<reference anchor="mc-prob-stmt">
<front>
<title>Multicast on 802.11</title>
<author surname="Mikael Abrahamsson and Adrian Stephens">
<organization> "IAB, IEEE 802 Wireless" </organization>
<address>
<uri>https://www.iab.org/wp-content/IAB-uploads/2013/01/multicast-problem-statement.pptx</uri>
</address>
</author>
<date month="March" year="2015"/>
</front>
</reference>
<!--
<reference anchor="dot15mc">
<front>
<title>IEEE 802.15.4 and ZigBee as Enabling Technologies</title>
<author surname='Stefano Tennina et al.'>
<organization>
</organization>
<address>
<uri>https://www.iab.org/wp-content/IAB-uploads/2013/01/multicast-problem-statement.pptx</uri>
</address>
</author>
<date month="March" year="2015"/>
</front>
</reference>
<author surname='Stefano Tennina, Anis Koubaa, Roberta Daidone,
Mario Alves, et al.'>
Koubaa had first 'a' with caret
Mario had 'a' with accent
-->
</references>
<!--
<section anchor="acknowledgements" title="Acknowledgements">
<t>
This document stems from discussions with the following people,
in alphabetical order:
Warren Kumari.
</t>
</section>
-->
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-24 02:59:11 |