draft-ietf-intarea-broadcast-consider-08.txt   draft-ietf-intarea-broadcast-consider-09.txt 
Internet Engineering Task Force R. Winter Internet Engineering Task Force R. Winter
Internet-Draft University of Applied Sciences Augsburg Internet-Draft University of Applied Sciences Augsburg
Intended status: Informational M. Faath Intended status: Informational M. Faath
Expires: July 23, 2018 Conntac GmbH Expires: September 14, 2018 Conntac GmbH
F. Weisshaar F. Weisshaar
University of Applied Sciences Augsburg University of Applied Sciences Augsburg
January 19, 2018 March 13, 2018
Privacy considerations for protocols relying on IP broadcast and Privacy considerations for protocols relying on IP broadcast and
multicast multicast
draft-ietf-intarea-broadcast-consider-08 draft-ietf-intarea-broadcast-consider-09
Abstract Abstract
A number of application-layer protocols make use of IP broadcasts or A number of application-layer protocols make use of IP broadcasts or
multicast messages for functions like local service discovery or name multicast messages for functions such as local service discovery or
resolution. Some of these functions can only be implemented name resolution. Some of these functions can only be implemented
efficiently using such mechanisms. When using broadcasts or efficiently using such mechanisms. When using broadcasts or
multicast messages, a passive observer in the same broadcast/ multicast messages, a passive observer in the same broadcast/
multicast domain can trivially record these messages and analyze multicast domain can trivially record these messages and analyze
their content. Therefore, designers of protocols that make use their content. Therefore, designers of protocols that make use of
broadcast/multicast messages need to take special care when designing broadcast/multicast messages need to take special care when designing
their protocols. their protocols.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 23, 2018. This Internet-Draft will expire on September 14, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Privacy considerations . . . . . . . . . . . . . . . . . . . 5 2. Privacy considerations . . . . . . . . . . . . . . . . . . . 5
2.1. Message frequency . . . . . . . . . . . . . . . . . . . . 5 2.1. Message frequency . . . . . . . . . . . . . . . . . . . . 5
2.2. Persistent identifiers . . . . . . . . . . . . . . . . . 5 2.2. Persistent identifiers . . . . . . . . . . . . . . . . . 5
2.3. Anticipate user behavior . . . . . . . . . . . . . . . . 6 2.3. Anticipate user behavior . . . . . . . . . . . . . . . . 6
2.4. Consider potential correlation . . . . . . . . . . . . . 7 2.4. Consider potential correlation . . . . . . . . . . . . . 7
2.5. Configurability . . . . . . . . . . . . . . . . . . . . . 7 2.5. Configurability . . . . . . . . . . . . . . . . . . . . . 7
3. Operational considerations . . . . . . . . . . . . . . . . . 8 3. Operational considerations . . . . . . . . . . . . . . . . . 8
4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Other considerations . . . . . . . . . . . . . . . . . . . . 9 5. Other considerations . . . . . . . . . . . . . . . . . . . . 9
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Security Considerations . . . . . . . . . . . . . . . . . . . 10 8. Security Considerations . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . 10 9.1. Normative References . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . 10 9.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction 1. Introduction
Broadcast and multicast messages have a large (and to the sender Broadcast and multicast messages have a large (and to the sender
unknown) receiver group by design. Because of that, these two unknown) receiver group by design. Because of that, these two
mechanisms are vital for a number of basic network functions such as mechanisms are vital for a number of basic network functions such as
auto-configuration or link-layer address lookup. Also application auto-configuration or link-layer address lookup. Also application
developers use broadcast/multicast messages to implement things like developers use broadcast/multicast messages to implement things such
local service or peer discovery. It appears that an increasing as local service or peer discovery. It appears that an increasing
number of applications make use of it as suggested by experimental number of applications make use of it as suggested by experimental
results obtained on campus networks including the IETF meeting results obtained on campus networks including the IETF meeting
network [TRAC2016]. This trend is not entirely surprising. As RFC network [TRAC2016]. This trend is not entirely surprising. As
919 [RFC0919] puts it, "The use of broadcasts [...] is a good base [RFC0919] puts it, "The use of broadcasts [...] is a good base for
for many applications". Broadcast and multicast functionality in a many applications". Broadcast and multicast functionality in a
subnetwork are therefore important as a lack thereof renders the subnetwork are therefore important as a lack thereof renders the
protocols relying on these mechanisms inoperable [RFC3819]. protocols relying on these mechanisms inoperable [RFC3819].
Using broadcast/multicast can become problematic if the information Using broadcast/multicast can become problematic if the information
that is being distributed can be regarded as sensitive or when the that is being distributed can be regarded as sensitive or when the
information that is distributed by multiple of these protocols can be information that is distributed by multiple of these protocols can be
correlated in a way that sensitive data can be derived. This is correlated in a way that sensitive data can be derived. This is
clearly true for any protocol, but broadcast/multicast is special in clearly true for any protocol, but broadcast/multicast is special in
at least two respects: at least two respects:
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might be required. When encryption is not used, the content of might be required. When encryption is not used, the content of
these messages is easily accessible, making it easy to spoof and these messages is easily accessible, making it easy to spoof and
replay them. replay them.
Given the above, privacy protection for protocols based on broadcast Given the above, privacy protection for protocols based on broadcast
or multicast communication is significantly more difficult compared or multicast communication is significantly more difficult compared
to unicast communication and at the same time invading the privacy is to unicast communication and at the same time invading the privacy is
much easier. much easier.
Privacy considerations of IETF-specified protocols have received some Privacy considerations of IETF-specified protocols have received some
attention in the recent past (e.g. RFC 7721 [RFC7721] or RFC 7819 attention in the recent past (e.g. [RFC7721] or [RFC7819]). There
[RFC7819]). There is also general guidance available for document is also general guidance available for document authors on when and
authors on when and how to include a privacy considerations section how to include a privacy considerations section in their documents
in their documents and on how to evaluate the privacy implications of and on how to evaluate the privacy implications of Internet protocols
Internet protocols [RFC6973]. RFC6973 also describes potential [RFC6973]. RFC6973 also describes potential threats to privacy in
threats to privacy in great detail and lists terminology that is also great detail and lists terminology that is also used in this
used in this document. In contrast to RFC6973, this document document. In contrast to RFC6973, this document contains a number of
contains a number of privacy considerations especially for protocols privacy considerations especially for protocols that rely on
that rely on broadcast/multicast, intended to reduce the likelihood broadcast/multicast, intended to reduce the likelihood that a
that a broadcast/multicast protocol can be misused to collect broadcast/multicast protocol can be misused to collect sensitive data
sensitive data about devices, users and groups of users on a about devices, users and groups of users in a broadcast/multicast
broadcast/multicast domain. domain.
The above mentioned considerations particularly apply to protocols The above mentioned considerations particularly apply to protocols
designed outside the IETF - for two reasons. For one, non-standard designed outside the IETF - for two reasons. For one, non-standard
protocols will likely not receive operational attention and support protocols will likely not receive operational attention and support
in making them more secure such as e.g. DHCP snooping does for DHCP in making them more secure, e.g. what DHCP snooping does for DHCP.
because they typically are not documented. The other reason is that But because these protocols are typically not documented, network
these protocols have been designed in isolation, where a set of equipment does not provide similar features for them. The other
considerations to follow is useful in the absence of a larger reason is that these protocols have been designed in isolation, where
community providing feedback. In particular, carelessly designed a set of considerations to follow is useful in the absence of a
protocols that use broadcast/multicast can break privacy efforts at larger community providing feedback and expertise to improve the
different layers of the protocol stack such as MAC address or IP protocol. In particular, carelessly designed protocols that use
address randomization [RFC4941]. broadcast/multicast can break privacy efforts at different layers of
the protocol stack such as MAC address or IP address randomization
[RFC4941].
1.1. Types and usage of broadcast and multicast 1.1. Types and usage of broadcast and multicast
In IPv4, two major types of broadcast addresses exist, the limited In IPv4, two major types of broadcast addresses exist, the limited
broadcast which is defined as all-ones (255.255.255.255, defined in broadcast which is defined as all-ones (255.255.255.255, defined in
section 5.3.5.1 of [RFC1812]) and the directed broadcast with the section 5.3.5.1 of [RFC1812]) and the directed broadcast with the
given network prefix of an IP address and the host part of all-ones given network prefix of an IP address and the host part of all-ones
(defined in section 5.3.5.2. of [RFC1812]). Broadcast packets are (defined in section 5.3.5.2. of [RFC1812]). Broadcast packets are
received by all nodes in a subnetwork. Limited broadcasts never received by all nodes in a subnetwork. Limited broadcasts never
transit a router. The same is true for directed broadcasts by transit a router. The same is true for directed broadcasts by
default, but routers MAY provide an option to do this [RFC2644]. default, but routers may provide an option to do this [RFC2644].
IPv6 on the other hand does not provide broadcast addresses but IPv6 on the other hand does not provide broadcast addresses but
solely relies on multicast [RFC4291]. solely relies on multicast [RFC4291].
In contrast to broadcast addresses, multicast addresses represent an In contrast to broadcast addresses, multicast addresses represent an
identifier for a set of interfaces that can be a set different from identifier for a set of interfaces that can be a set different from
all nodes in the subnetwork. All interfaces that are identified by a all nodes in the subnetwork. All interfaces that are identified by a
given multicast address receive packets destined towards that address given multicast address receive packets destined towards that address
and are called a multicast group. In both IPv4 and IPv6, multiple and are called a multicast group. In both IPv4 and IPv6, multiple
pre-defined multicast addresses exist. The ones most relevant for pre-defined multicast addresses exist. The ones most relevant for
this document are the ones with subnet scope. For IPv4, an IP prefix this document are the ones with subnet scope. For IPv4, an IP prefix
is reserved for this purpose called the Local Network Control Block is reserved for this purpose called the Local Network Control Block
(224.0.0.0/24, defined in section 4 of [RFC5771]). For IPv6, the (224.0.0.0/24, defined in section 4 of [RFC5771]). For IPv6, the
relevant multicast addresses are the two All Nodes Addresses, which relevant multicast addresses are the two All Nodes Addresses, which
every IPv6-capable host is required to recognize as identifying every IPv6-capable host is required to recognize as identifying
itself (see section 2.7.1 of [RFC4291]). itself (see section 2.7.1 of [RFC4291]).
Typical usage of these addresses include local service discovery Typical usage of these addresses include local service discovery
(e.g. mDNS [RFC6762] and LLMNR [RFC4795] make use of multicast), (e.g. Multicast DNS (mDNS) [RFC6762] and Link-Local Multicast Name
Resolution (LLMNR) [RFC4795] make use of multicast),
autoconfiguration (e.g. DHCPv4 [RFC2131] uses broadcasts and DHCPv6 autoconfiguration (e.g. DHCPv4 [RFC2131] uses broadcasts and DHCPv6
[RFC3315] uses multicast addresses) and other vital network services [RFC3315] uses multicast addresses) and other vital network services
such as address resolution or duplicate address detection. But such as address resolution or duplicate address detection. But
besides these core network functions, also applications make use of besides these core network functions, also applications make use of
broadcast and multicast functionality, often implementing proprietary broadcast and multicast functionality, often implementing proprietary
protocols. In sum, these protocols distribute a diverse set of protocols. In sum, these protocols distribute a diverse set of
potentially privacy sensitive information to a large receiver group. potentially privacy sensitive information to a large receiver group
To become a receiver, the only requirement is to be part of the same and to be part of this receiver group, the only requirement is to be
subnetwork. on same subnetwork.
1.2. Requirements Language 1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in [RFC2119].
2. Privacy considerations 2. Privacy considerations
There are a few obvious and a few not necessarily obvious things There are a few obvious and a few not necessarily obvious things
designers of protocols utilizing broadcast/multicast should consider designers of protocols utilizing broadcast/multicast should consider
in respect to the privacy implications of their protocol. Most of in respect to the privacy implications of their protocol. Most of
these items are based on protocol behavior observed as part of these items are based on protocol behavior observed as part of
experiments on operational networks [TRAC2016]. experiments on operational networks [TRAC2016].
2.1. Message frequency 2.1. Message frequency
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also give the rough location of the user away (e.g. a campus or also give the rough location of the user away (e.g. a campus or
building). building).
This behavior has e.g. been observed by a synchronization mechanism This behavior has e.g. been observed by a synchronization mechanism
of a popular application, where multiple messages have been sent per of a popular application, where multiple messages have been sent per
minute via broadcast. Given this behavior, it is possible to record minute via broadcast. Given this behavior, it is possible to record
a device's time on the network with a sub-minute accuracy given only a device's time on the network with a sub-minute accuracy given only
the traffic of this single application installed on the device. But the traffic of this single application installed on the device. But
also services used for local name resolution in modern operating also services used for local name resolution in modern operating
systems utilize broadcast/multicast protocols (e.g. mDNS, LLMNR or systems utilize broadcast/multicast protocols (e.g. mDNS, LLMNR or
NetBIOS) to announce for example their shares regularly and allow a NetBIOS) to announce for example resources regularly which also allow
tracking of the online time of a device. tracking the online time of a device.
If a protocol relies on frequent or periodic broadcast/multicast If a protocol relies on frequent or periodic broadcast/multicast
messages, the frequency SHOULD be chosen conservatively, in messages, the frequency SHOULD be chosen conservatively, in
particular if the messages contain persistent identifiers (see next particular if the messages contain persistent identifiers (see next
subsection). Also, intelligent message suppression mechanisms such subsection). Also, intelligent message suppression mechanisms such
as the ones employed in mDNS [RFC6762] SHOULD be implemented. The as the ones employed in mDNS [RFC6762] SHOULD be implemented. The
lower the frequency of broadcast messages, the harder passive traffic lower the frequency of broadcast messages, the harder passive traffic
analysis and surveillance becomes. analysis and surveillance becomes.
2.2. Persistent identifiers 2.2. Persistent identifiers
A few protocols that make use of broadcast/multicast messages A few protocols that make use of broadcast/multicast messages
observed in the wild make use of persistent identifiers. This observed in the wild make use of persistent identifiers. This
includes the use of host names or more abstract persistent includes the use of host names or more abstract persistent
identifiers such as a universally unique identifiers (UUID) or identifiers such as a universally unique identifiers (UUID) or
similar. These IDs, which e.g. identify the installation of a similar. These IDs, which e.g. identify the installation of a
certain application might not change across updates of the software certain application might not change across updates of the software
and are therefore extremely long lived. This allows a passive and can therefore be extremely long lived. This allows a passive
observer to track a user precisely if broadcast/multicast messages observer to track a user precisely if broadcast/multicast messages
are frequent. This is even true in case the IP and/or MAC address are frequent. This is even true in case the IP and/or MAC address
changes. Such identifiers also allow two different interfaces (e.g. changes. Such identifiers also allow two different interfaces (e.g.
WiFi and Ethernet) to be correlated to the same device. If the WiFi and Ethernet) to be correlated to the same device. If the
application makes use of persistent identifiers for multiple application makes use of persistent identifiers for multiple
installations of the same application for the same user, this even installations of the same application for the same user, this even
allows to infer that different devices belong to the same user. allows to infer that different devices belong to the same user.
The aforementioned broadcast messages from a synchronization The aforementioned broadcast messages from a synchronization
mechanism of a popular application also included a persistent mechanism of a popular application also included a persistent
identifier in every broadcast. This identifier did never change identifier in every broadcast. This identifier never changed after
after the application was installed and allowed to track a device the application was installed and it allowed to track a device even
even when it changed its network interface or when it connected to a when it changed its network interface or when it connected to a
different network. different network.
Persistent IDs are considered bad practice in general for broadcast Persistent IDs are considered bad practice in general for broadcast
and multicast communication, as persistent application layer IDs will and multicast communication, as persistent application layer IDs will
make efforts on lower layers to randomize identifiers (e.g. make efforts on lower layers to randomize identifiers (e.g.
[I-D.huitema-6man-random-addresses]) useless. When protocols that [I-D.huitema-6man-random-addresses]) useless. When protocols that
make use of broadcast/multicast need to make use of IDs, frequent make use of broadcast/multicast need to make use of IDs, these IDs
rotations of these IDs SHOULD be considered to make user tracking SHOULD be rotated frequently to make user tracking more difficult.
more difficult.
2.3. Anticipate user behavior 2.3. Anticipate user behavior
A large number of users name their device after themselves, either A large number of users name their device after themselves, either
using their first name, last name or both. Often a host name using their first name, last name or both. Often a host name
includes the type, model or maker of a device, its function or includes the type, model or maker of a device, its function or it
includes language specific information. Based on data gathered includes language specific information. Based on data gathered
during experiments performed at IETF meetings and at a large campus during experiments performed at IETF meetings and at a large campus
network, this appears currently to be prevalent user behavior network, this appears currently to be prevalent user behavior
[TRAC2016]. For protocols using the host name as part of the [TRAC2016]. For protocols using the host name as part of the
messages, this clearly will reveal personally identifiable messages, this clearly will reveal personally identifiable
information to everyone on the local network. This information can information to everyone on the local network. This information can
also be used to mount more sophisticated attacks, when e.g. the owner also be used to mount more sophisticated attacks, when e.g. the owner
of a device is identified (as an interesting target) or properties of of a device is identified (as an interesting target) or properties of
the device are known (e.g. known vulnerabilities). the device are known (e.g. known vulnerabilities). Host names are
also a type of persistent identifier and therefore the considerations
in Section 2.2 apply.
Some of the most commonly used operating systems include the name the Some of the most commonly used operating systems include the name the
user chooses for the user account during the installation process as user chooses for the user account during the installation process as
part of the host name of the device. The name of the operating part of the host name of the device. The name of the operating
system can also be included, revealing therefore two pieces of system can also be included, revealing therefore two pieces of
information, which can be regarded as private information if the host information, which can be regarded as private information if the host
name is used in broadcast/multicast messages. name is used in broadcast/multicast messages.
Where possible, the use of host names and other user-provided Where possible, the use of host names and other user-provided
information in protocols making use of broadcast/multicast SHOULD be information in protocols making use of broadcast/multicast SHOULD be
avoided. If all that is required is a persistent identifier (which avoided. An application might want to display the information it
SHOULD be avoided, see Section 2.2), this SHOULD be generated
randomly. An application might want to display the information it
will broadcast on the LAN at install/config time, so the user is at will broadcast on the LAN at install/config time, so the user is at
least aware of the application's behavior. More host name least aware of the application's behavior. More host name
considerations can be found in [RFC8117]. More information on user considerations can be found in [RFC8117]. More information on user
participation can be found in RFC 6973 [RFC6973]. participation can be found in [RFC6973].
2.4. Consider potential correlation 2.4. Consider potential correlation
A large number of services and applications make use of the A large number of services and applications make use of the
broadcast/multicast mechanism. That means there are various sources broadcast/multicast mechanism. That means there are various sources
of information that are easily accessible by a passive observer. In of information that are easily accessible by a passive observer. In
isolation, the information these protocols reveal might seem isolation, the information these protocols reveal might seem
harmless, but given multiple such protocols, it might be possible to harmless, but given multiple such protocols, it might be possible to
correlate this information. E.g. a protocol that uses frequent correlate this information. E.g. a protocol that uses frequent
messages including a UUID to identify the particular installation messages including a UUID to identify the particular installation
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An application developer making use of broadcasts/multicasts as part An application developer making use of broadcasts/multicasts as part
of the application SHOULD make the broadcast feature, if possible, of the application SHOULD make the broadcast feature, if possible,
configurable, so that potentially sensitive information does not leak configurable, so that potentially sensitive information does not leak
on public networks, where the threat to privacy is much larger. on public networks, where the threat to privacy is much larger.
3. Operational considerations 3. Operational considerations
Besides changing end-user behavior, choosing sensible defaults as an Besides changing end-user behavior, choosing sensible defaults as an
operating system vendor (e.g. for suggesting host names) and the operating system vendor (e.g. for suggesting host names) and the
considerations for protocol designers mentioned in this document, considerations for protocol designers mentioned in this document,
there are things that the network administrators/operators can do to there is something that the network administrators/operators can do
limit the above mentioned problems. to limit the above mentioned problems.
A feature not uncommonly found on access points e.g. is to filter A feature commonly found on access points e.g. is to manage/filter
broadcast and multicast traffic. This will potentially break certain broadcast and multicast traffic. This will potentially break certain
applications or some of their functionality but will also protect the applications or some of their functionality but will also protect the
users from potentially leaking sensitive information. users from potentially leaking sensitive information. Wireless
access points often provide finer-grained control beyond a simple on/
off switch for well-known protocols or provide mechanisms to manage
broadcast/multicast traffic intelligently using e.g. proxies (see
[I-D.ietf-mboned-ieee802-mcast-problems]). These mechanisms however
only work on standardized protocols.
4. Summary 4. Summary
Increasingly, applications rely on protocols that send and receive Increasingly, applications rely on protocols that send and receive
broadcast and multicast messages. For some, broadcasts/multicasts broadcast and multicast messages. For some, broadcasts/multicasts
are the basis of their application logic, others use broadcasts/ are the basis of their application logic, others use broadcasts/
multicasts to improve certain aspects of the application but are multicasts to improve certain aspects of the application but are
fully functional in case broadcasts/multicasts fail. Irrespective of fully functional in case broadcasts/multicasts fail. Irrespective of
the role of broadcast and multicast messages for the application, the the role of broadcast and multicast messages for the application, the
designers of protocols that make use of them should be very careful designers of protocols that make use of them should be very careful
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the risk of information leakage (e.g. a home network as opposed the risk of information leakage (e.g. a home network as opposed
to a public Wifi) to a public Wifi)
5. Other considerations 5. Other considerations
Besides privacy implications, frequent broadcasting also represents a Besides privacy implications, frequent broadcasting also represents a
performance problem. In particular in certain wireless technologies performance problem. In particular in certain wireless technologies
such as 802.11, broadcast and multicast are transmitted at a much such as 802.11, broadcast and multicast are transmitted at a much
lower rate (the lowest common denominator rate) compared to unicast lower rate (the lowest common denominator rate) compared to unicast
and therefore have a much bigger impact on the overall available and therefore have a much bigger impact on the overall available
airtime [I-D.perkins-intarea-multicast-ieee802]. Further, it will airtime [I-D.ietf-mboned-ieee802-mcast-problems]. Further, it will
limit the ability for devices to go to sleep if frequent broadcasts limit the ability for devices to go to sleep if frequent broadcasts
are being sent. A similar problem in respect to Router are being sent. A similar problem in respect to Router
Advertisements is addressed in Advertisements is addressed in
[I-D.ietf-v6ops-reducing-ra-energy-consumption]. In that respect [I-D.ietf-v6ops-reducing-ra-energy-consumption]. In that respect
broadcasts/multicast can be used for another class of attacks that is broadcasts/multicast can be used for another class of attacks that is
not related to privacy. The potential impact on network performance not related to privacy. The potential impact on network performance
should nevertheless be considered when designing a protocol that should nevertheless be considered when designing a protocol that
makes use of broadcast/multicast. makes use of broadcast/multicast.
6. Acknowledgments 6. Acknowledgments
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[I-D.huitema-6man-random-addresses] [I-D.huitema-6man-random-addresses]
Huitema, C., "Implications of Randomized Link Layers Huitema, C., "Implications of Randomized Link Layers
Addresses for IPv6 Address Assignment", draft-huitema- Addresses for IPv6 Address Assignment", draft-huitema-
6man-random-addresses-03 (work in progress), March 2016. 6man-random-addresses-03 (work in progress), March 2016.
[I-D.ietf-dnssd-privacy] [I-D.ietf-dnssd-privacy]
Huitema, C. and D. Kaiser, "Privacy Extensions for DNS- Huitema, C. and D. Kaiser, "Privacy Extensions for DNS-
SD", draft-ietf-dnssd-privacy-00 (work in progress), SD", draft-ietf-dnssd-privacy-00 (work in progress),
October 2016. October 2016.
[I-D.ietf-mboned-ieee802-mcast-problems]
Perkins, C., McBride, M., Stanley, D., Kumari, W., and J.
Zuniga, "Multicast Considerations over IEEE 802 Wireless
Media", draft-ietf-mboned-ieee802-mcast-problems-01 (work
in progress), February 2018.
[I-D.ietf-v6ops-reducing-ra-energy-consumption] [I-D.ietf-v6ops-reducing-ra-energy-consumption]
Yourtchenko, A. and L. Colitti, "Reducing energy Yourtchenko, A. and L. Colitti, "Reducing energy
consumption of Router Advertisements", draft-ietf-v6ops- consumption of Router Advertisements", draft-ietf-v6ops-
reducing-ra-energy-consumption-03 (work in progress), reducing-ra-energy-consumption-03 (work in progress),
November 2015. November 2015.
[I-D.perkins-intarea-multicast-ieee802]
Perkins, C., Stanley, D., Kumari, W., and J. Zuniga,
"Multicast Considerations over IEEE 802 Wireless Media",
draft-perkins-intarea-multicast-ieee802-03 (work in
progress), July 2017.
[RFC0919] Mogul, J., "Broadcasting Internet Datagrams", STD 5, RFC [RFC0919] Mogul, J., "Broadcasting Internet Datagrams", STD 5, RFC
919, DOI 10.17487/RFC0919, October 1984, 919, DOI 10.17487/RFC0919, October 1984,
<http://www.rfc-editor.org/info/rfc919>. <http://www.rfc-editor.org/info/rfc919>.
[RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers", [RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers",
RFC 1812, DOI 10.17487/RFC1812, June 1995, RFC 1812, DOI 10.17487/RFC1812, June 1995,
<http://www.rfc-editor.org/info/rfc1812>. <http://www.rfc-editor.org/info/rfc1812>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, DOI 10.17487/RFC2131, March 1997, 2131, DOI 10.17487/RFC2131, March 1997,
 End of changes. 30 change blocks. 
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