draft-ietf-6man-ipv6-address-generation-privacy-08.txt   rfc7721.txt 
Network Working Group A. Cooper Internet Engineering Task Force (IETF) A. Cooper
Internet-Draft Cisco Request for Comments: 7721 Cisco
Intended status: Informational F. Gont Category: Informational F. Gont
Expires: March 26, 2016 Huawei Technologies ISSN: 2070-1721 Huawei Technologies
D. Thaler D. Thaler
Microsoft Microsoft
September 23, 2015 March 2016
Privacy Considerations for IPv6 Address Generation Mechanisms Security and Privacy Considerations for
draft-ietf-6man-ipv6-address-generation-privacy-08.txt IPv6 Address Generation Mechanisms
Abstract Abstract
This document discusses privacy and security considerations for This document discusses privacy and security considerations for
several IPv6 address generation mechanisms, both standardized and several IPv6 address generation mechanisms, both standardized and
non-standardized. It evaluates how different mechanisms mitigate non-standardized. It evaluates how different mechanisms mitigate
different threats and the trade-offs that implementors, developers, different threats and the trade-offs that implementors, developers,
and users face in choosing different addresses or address generation and users face in choosing different addresses or address generation
mechanisms. mechanisms.
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 http://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 a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
This Internet-Draft will expire on March 26, 2016. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7721.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2016 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Weaknesses in IEEE-identifier-based IIDs . . . . . . . . . . 4 3. Weaknesses in IEEE-Identifier-Based IIDs . . . . . . . . . . 5
3.1. Correlation of activities over time . . . . . . . . . . . 5 3.1. Correlation of Activities over Time . . . . . . . . . . . 5
3.2. Location tracking . . . . . . . . . . . . . . . . . . . . 6 3.2. Location Tracking . . . . . . . . . . . . . . . . . . . . 6
3.3. Address scanning . . . . . . . . . . . . . . . . . . . . 6 3.3. Address Scanning . . . . . . . . . . . . . . . . . . . . 7
3.4. Device-specific vulnerability exploitation . . . . . . . 7 3.4. Device-Specific Vulnerability Exploitation . . . . . . . 7
4. Privacy and security properties of address generation 4. Privacy and Security Properties of Address Generation
mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . 7 Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. IEEE-identifier-based IIDs . . . . . . . . . . . . . . . 9 4.1. IEEE-Identifier-Based IIDs . . . . . . . . . . . . . . . 10
4.2. Static, manually configured IIDs . . . . . . . . . . . . 10 4.2. Static, Manually Configured IIDs . . . . . . . . . . . . 10
4.3. Constant, semantically opaque IIDs . . . . . . . . . . . 10 4.3. Constant, Semantically Opaque IIDs . . . . . . . . . . . 10
4.4. Cryptographically generated IIDs . . . . . . . . . . . . 10 4.4. Cryptographically Generated IIDs . . . . . . . . . . . . 10
4.5. Stable, semantically opaque IIDs . . . . . . . . . . . . 10 4.5. Stable, Semantically Opaque IIDs . . . . . . . . . . . . 11
4.6. Temporary IIDs . . . . . . . . . . . . . . . . . . . . . 11 4.6. Temporary IIDs . . . . . . . . . . . . . . . . . . . . . 11
4.7. DHCPv6 generation of IIDs . . . . . . . . . . . . . . . . 12 4.7. DHCPv6 Generation of IIDs . . . . . . . . . . . . . . . . 12
4.8. Transition/co-existence technologies . . . . . . . . . . 12 4.8. Transition and Coexistence Technologies . . . . . . . . . 12
5. Miscellaneous Issues with IPv6 addressing . . . . . . . . . . 13 5. Miscellaneous Issues with IPv6 Addressing . . . . . . . . . . 13
5.1. Network Operation . . . . . . . . . . . . . . . . . . . . 13 5.1. Network Operation . . . . . . . . . . . . . . . . . . . . 13
5.2. Compliance . . . . . . . . . . . . . . . . . . . . . . . 13 5.2. Compliance . . . . . . . . . . . . . . . . . . . . . . . 13
5.3. Intellectual Property Rights (IPRs) . . . . . . . . . . . 13 5.3. Intellectual Property Rights (IPRs) . . . . . . . . . . . 13
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13 6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 7.1. Normative References . . . . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 7.2. Informative References . . . . . . . . . . . . . . . . . 15
9.1. Normative References . . . . . . . . . . . . . . . . . . 14 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 18
9.2. Informative References . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction 1. Introduction
IPv6 was designed to improve upon IPv4 in many respects, and IPv6 was designed to improve upon IPv4 in many respects, and
mechanisms for address assignment were one such area for improvement. mechanisms for address assignment were one such area for improvement.
In addition to static address assignment and DHCP, stateless In addition to static address assignment and DHCP, stateless
autoconfiguration was developed as a less intensive, fate-shared autoconfiguration was developed as a less intensive, fate-shared
means of performing address assignment. With stateless means of performing address assignment. With stateless
autoconfiguration, routers advertise on-link prefixes and hosts autoconfiguration, routers advertise on-link prefixes and hosts
generate their own interface identifiers (IIDs) to complete their generate their own Interface Identifiers (IIDs) to complete their
addresses. [RFC7136] clarifies that the IID should be treated as an addresses. [RFC7136] clarifies that the IID should be treated as an
opaque value, while [RFC7421] provides an analysis of the 64-bit opaque value, while [RFC7421] provides an analysis of the 64-bit
boundary in IPv6 addressing (e.g. the implications of the IID length boundary in IPv6 addressing (e.g., the implications of the IID length
on security and privacy). Over the years, many interface identifier on security and privacy). Over the years, many IID generation
generation techniques have been defined, both standardized and non- techniques have been defined, both standardized and non-standardized:
standardized:
o Manual configuration o Manual configuration [RFC7707]
* IPv4 address * IPv4 address
* Service port * Service port
* Wordy * Wordy
* Low-byte * Low-byte
o Stateless Address Auto-Cofiguration (SLAAC) o Stateless Address Autoconfiguration (SLAAC)
* IEEE 802 48-bit MAC or IEEE EUI-64 identifier [RFC2464] * IEEE 802 48-bit Media Access Control (MAC) or IEEE 64-bit
Extended Unique Identifier (EUI-64) [RFC2464]
* Cryptographically generated [RFC3972] * Cryptographically generated [RFC3972]
* Temporary (also known as "privacy addresses") [RFC4941] * Temporary (also known as "privacy addresses") [RFC4941]
* Constant, semantically opaque (also known as random) * Constant, semantically opaque (also known as "random")
[Microsoft] [Microsoft]
* Stable, semantically opaque [RFC7217] * Stable, semantically opaque [RFC7217]
o DHCPv6-based [RFC3315] o DHCPv6 based [RFC3315]
o Specified by transition/co-existence technologies o Specified by transition/co-existence technologies
* Derived from an IPv4 address (e.g., [RFC5214], [RFC6052]) * Derived from an IPv4 address (e.g., [RFC5214], [RFC6052])
* Derived from an IPv4 address and port set ID (e.g., [RFC7596], * Derived from an IPv4 address and port set ID (e.g., [RFC7596],
[RFC7597], [RFC7599]) [RFC7597], [RFC7599])
* Derived from an IPv4 address and port (e.g., [RFC4380]) * Derived from an IPv4 address and port (e.g., [RFC4380])
Deriving the IID from a globally unique IEEE identifier [RFC2464] Deriving the IID from a globally unique IEEE identifier [RFC2464]
[RFC4862] was one of the earliest mechanisms developed (and [RFC4862] was one of the earliest mechanisms developed (and
originally specified in [RFC1971] and [RFC1972]). A number of originally specified in [RFC1971] and [RFC1972]). A number of
privacy and security issues related to the IIDs derived from IEEE privacy and security issues related to the IIDs derived from IEEE
identifiers were discovered after their standardization, and many of identifiers were discovered after their standardization, and many of
the mechanisms developed later aimed to mitigate some or all of these the mechanisms developed later aimed to mitigate some or all of these
weaknesses. This document identifies four types of threats against weaknesses. This document identifies four types of attacks against
IEEE-identifier-based IIDs, and discusses how other existing IEEE-identifier-based IIDs and discusses how other existing
techniques for generating IIDs do or do not mitigate those threats. techniques for generating IIDs do or do not mitigate those attacks.
2. Terminology 2. Terminology
This section clarifies the terminology used throughout this document. This section clarifies the terminology used throughout this document.
Public address: Public address:
An address that has been published in a directory or other public An address that has been published in a directory or other public
location, such as the DNS, a SIP proxy [RFC3261], an application- location, such as the DNS, a SIP proxy [RFC3261], an application-
specific DHT, or a publicly available URI. A host's public specific Distributed Hash Table (DHT), or a publicly available
addresses are intended to be discoverable by third parties. URI. A host's public addresses are intended to be discoverable by
third parties.
Stable address: Stable address:
An address that does not vary over time within the same IPv6 link. An address that does not vary over time within the same IPv6 link.
Note that [RFC4941] refers to these as "public" addresses, but Note that [RFC4941] refers to these as "public" addresses, but
"stable" is used here for reasons explained in Section 4. "stable" is used here for reasons explained in Section 4.
Temporary address: Temporary address:
An address that varies over time within the same IPv6 link. An address that varies over time within the same IPv6 link.
Constant IID: Constant IID:
An IPv6 interface identifier that is globally stable. That is, An IPv6 interface identifier that is globally stable. That is,
the Interface ID will remain constant even if the node moves from the Interface ID will remain constant even if the node moves from
one IPv6 link to another. one IPv6 link to another.
Stable IID: Stable IID:
An IPv6 interface identifier that is stable within some specified An IPv6 interface identifier that is stable within some specified
context. For example, an Interface ID can be globally stable context. For example, an Interface ID can be globally stable
(constant), or could be stable per IPv6 link (meaning that the (constant) or could be stable per IPv6 link (meaning that the
Interface ID will remain unchanged as long as a the node stays on Interface ID will remain unchanged as long as the node stays on
the same IPv6 link, but may change when the node moves from one the same IPv6 link but may change when the node moves from one
IPv6 link to another). IPv6 link to another).
Temporary IID: Temporary IID:
An IPv6 interface identifier that varies over time. An IPv6 interface identifier that varies over time.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[RFC2119]. These words take their normative meanings only when they [RFC2119]. These words take their normative meanings only when they
are presented in ALL UPPERCASE. are presented in ALL UPPERCASE.
3. Weaknesses in IEEE-identifier-based IIDs 3. Weaknesses in IEEE-Identifier-Based IIDs
There are a number of privacy and security implications that exist There are a number of privacy and security implications that exist
for hosts that use IEEE-identifier-based IIDs. This section for hosts that use IEEE-identifier-based IIDs. This section
discusses four generic attack types: correlation of activities over discusses four generic attack types: correlation of activities over
time, location tracking, address scanning, and device-specific time, location tracking, address scanning, and device-specific
vulnerability exploitation. The first three of these rely on the vulnerability exploitation. The first three of these rely on the
attacker first gaining knowledge of the IID of the target host. This attacker first gaining knowledge of the IID of the target host. This
could be achieved by a number of different entities: the operator of could be achieved by a number of different entities: the operator of
a server to which the host connects, such as a web server or a peer- a server to which the host connects, such as a web server or a peer-
to-peer server; an entity that connects to the same IPv6 link as the to-peer server; an entity that connects to the same IPv6 link as the
target (such as a conference network or any public network); a target (such as a conference network or any public network); a
passive observer of traffic that the host broadcasts; or an entity passive observer of traffic that the host broadcasts; or an entity
that is on-path to the destinations with which the host communicates, that is on path to the destinations with which the host communicates,
such as a network operator. such as a network operator.
3.1. Correlation of activities over time 3.1. Correlation of Activities over Time
As with other identifiers, an IPv6 address can be used to correlate As with other identifiers, an IPv6 address can be used to correlate
the activities of a host for at least as long as the lifetime of the the activities of a host for at least as long as the lifetime of the
address. The correlation made possible by IEEE-identifier-based IIDs address. The correlation made possible by IEEE-identifier-based IIDs
is of particular concern since they last roughly for the lifetime of is of particular concern since they last roughly for the lifetime of
a device's network interface, allowing correlation on the order of a device's network interface, allowing correlation on the order of
years. years.
As [RFC4941] explains, As [RFC4941] explains,
"[t]he use of a non-changing interface identifier to form [t]he use of a non-changing interface identifier to form addresses
addresses is a specific instance of the more general case where a is a specific instance of the more general case where a constant
constant identifier is reused over an extended period of time and identifier is reused over an extended period of time and in
in multiple independent activities. Anytime the same identifier multiple independent activities. Anytime the same identifier is
is used in multiple contexts, it becomes possible for that used in multiple contexts, it becomes possible for that identifier
identifier to be used to correlate seemingly unrelated activity. to be used to correlate seemingly unrelated activity. ... The use
... The use of a constant identifier within an address is of of a constant identifier within an address is of special concern
special concern because addresses are a fundamental requirement of because addresses are a fundamental requirement of communication
communication and cannot easily be hidden from eavesdroppers and and cannot easily be hidden from eavesdroppers and other parties.
other parties. Even when higher layers encrypt their payloads, Even when higher layers encrypt their payloads, addresses in
addresses in packet headers appear in the clear." packet headers appear in the clear.
IP addresses are just one example of information that can be used to IP addresses are just one example of information that can be used to
correlate activities over time. DNS names, cookies [RFC6265], correlate activities over time. DNS names, cookies [RFC6265],
browser fingerprints [Panopticlick], and application-layer usernames browser fingerprints [Panopticlick], and application-layer usernames
can all be used to link a host's activities together. Although IEEE- can all be used to link a host's activities together. Although IEEE-
identifier-based IIDs are likely to last at least as long or longer identifier-based IIDs are likely to last at least as long or longer
than these other identifiers, IIDs generated in other ways may have than these other identifiers, IIDs generated in other ways may have
shorter or longer lifetimes than these identifiers depending on how shorter or longer lifetimes than these identifiers depending on how
th ey are generated. Therefore, the extent to which a host's they are generated. Therefore, the extent to which a host's
activities can be correlated depends on whether the host uses activities can be correlated depends on whether the host uses
multiple identifiers together and the lifetimes of all of those multiple identifiers together and the lifetimes of all of those
identifiers. Frequently refreshing an IPv6 address may not mitigate identifiers. Frequently refreshing an IPv6 address may not mitigate
correlation if an attacker has access to other longer lived correlation if an attacker has access to other longer-lived
identifiers for a particular host. This is an important caveat to identifiers for a particular host. This is an important caveat to
keep in mind throughout the discussion of correlation in this keep in mind throughout the discussion of correlation in this
document. For further discussion of correlation, see Section 5.2.1 document. For further discussion of correlation, see Section 5.2.1
of [RFC6973]. of [RFC6973].
As noted in [RFC4941], in some cases correlation is just as feasible As noted in [RFC4941], in some cases correlation is just as feasible
for a host using an IPv4 address as for a host using an IEEE for a host using an IPv4 address as for a host using an IEEE
identifier to generate its IID in its IPv6 address. Hosts that use identifier to generate its IID in its IPv6 address. Hosts that use
static IPv4 addressing or who are consistently allocated the same static IPv4 addressing or who are consistently allocated the same
address via DHCPv4 can be tracked as described above. However, the address via DHCPv4 can be tracked as described above. However, the
widespread use of both NAT and DHCPv4 implementations that assign the widespread use of both NAT and DHCPv4 implementations that assign the
same host a different address upon lease expiration mitigates this same host a different address upon lease expiration mitigates this
threat in the IPv4 case as compared to the IEEE identifier case in threat in the IPv4 case as compared to the IEEE identifier case in
IPv6. IPv6.
3.2. Location tracking 3.2. Location Tracking
Because the IPv6 address structure is divided between a topological Because the IPv6 address structure is divided between a topological
portion and an interface identifier portion, an interface identifier portion and an interface identifier portion, an interface identifier
that remains constant when a host connects to different IPv6 links that remains constant when a host connects to different IPv6 links
(as an IEEE-identifier-based IID does) provides a way for observers (as an IEEE-identifier-based IID does) provides a way for observers
to track the movements of that host. In a passive attack on a mobile to track the movements of that host. In a passive attack on a mobile
host, a server that receives connections from the same host over time host, a server that receives connections from the same host over time
would be able to determine the host's movements as its prefix would be able to determine the host's movements as its prefix
changes. changes.
Active attacks are also possible. An attacker that first learns the Active attacks are also possible. An attacker that first learns the
host's interface identifier by being connected to the same IPv6 link, host's interface identifier by being connected to the same IPv6 link,
running a server that the host connects to, or being on-path to the running a server that the host connects to, or being on path to the
host's communications could subsequently probe other networks for the host's communications could subsequently probe other networks for the
presence of the same interface identifier by sending a probe packet presence of the same interface identifier by sending a probe packet
(ICMPv6 Echo Request, or any other probe packet). Even if the host (e.g., ICMPv6 Echo Request, or any other probe packet). Even if the
does not respond, the first hop router will usually respond with an host does not respond, the first-hop router will usually respond with
ICMP Destination Unreachable/Address Unreachable (type 1, code 3) an ICMP Destination Unreachable/Address Unreachable (type 1, code 3)
when the host is not present, and be silent when the host is present. when the host is not present and be silent when the host is present.
Location tracking based on IP address is generally not possible in Location tracking based on IP address is generally not possible in
IPv4 since hosts get assigned wholly new addresses when they change IPv4 since hosts get assigned wholly new addresses when they change
networks. networks.
3.3. Address scanning 3.3. Address Scanning
The structure of IEEE-based identifiers used for address generation The structure of IEEE-based identifiers used for address generation
can be leveraged by an attacker to reduce the target search space can be leveraged by an attacker to reduce the target search space
[I-D.ietf-opsec-ipv6-host-scanning]. The 24-bit Organizationally [RFC7707]. The 24-bit Organizationally Unique Identifier (OUI) of
Unique Identifier (OUI) of MAC addresses, together with the fixed MAC addresses, together with the fixed value (0xff, 0xfe) used to
value (0xff, 0xfe) used to form a Modified EUI-64 interface form a Modified EUI-64 interface identifier, greatly help to reduce
identifier, greatly help to reduce the search space, making it easier the search space, making it easier for an attacker to scan for
for an attacker to scan for individual addresses using widely-known individual addresses using widely known popular OUIs. This erases
popular OUIs. This erases much of the protection against address much of the protection against address scanning that the larger IPv6
scanning that the larger IPv6 address space could provide as compared address space could provide as compared to IPv4.
to IPv4.
3.4. Device-specific vulnerability exploitation 3.4. Device-Specific Vulnerability Exploitation
IPv6 addresses that embed IEEE identifiers leak information about the IPv6 addresses that embed IEEE identifiers leak information about the
device (Network Interface Card vendor, or even Operating System and/ device (e.g., Network Interface Card vendor, or even Operating System
or software type), which could be leveraged by an attacker with and/or software type), which could be leveraged by an attacker with
knowledge of device/software-specific vulnerabilities to quickly find knowledge of device- or software-specific vulnerabilities to quickly
possible targets. Attackers can exploit vulnerabilities in hosts find possible targets. Attackers can exploit vulnerabilities in
whose IIDs they have previously obtained, or scan an address space to hosts whose IIDs they have previously obtained or scan an address
find potential targets. space to find potential targets.
4. Privacy and security properties of address generation mechanisms 4. Privacy and Security Properties of Address Generation Mechanisms
Analysis of the extent to which a particular host is protected Analysis of the extent to which a particular host is protected
against the threats described in Section 3 depends on how each of a against the attacks described in Section 3 depends on how each of a
host's addresses is generated and used. In some scenarios, a host host's addresses is generated and used. In some scenarios, a host
configures a single global address and uses it for all configures a single global address and uses it for all
communications. In other scenarios, a host configures multiple communications. In other scenarios, a host configures multiple
addresses using different mechanisms and may use any or all of them. addresses using different mechanisms and may use any or all of them.
[RFC3041] (later obsoleted by [RFC4941]) sought to address some of [RFC3041] (later obsoleted by [RFC4941]) sought to address some of
the problems described in Section 3 by defining "temporary addresses" the problems described in Section 3 by defining "temporary addresses"
for outbound connections. Temporary addresses are meant to for outbound connections. Temporary addresses are meant to
supplement the other addresses that a device might use, not to supplement the other addresses that a device might use, not to
replace them. They use IIDs that are randomly generated and change replace them. They use IIDs that are randomly generated and change
skipping to change at page 7, line 41 skipping to change at page 8, line 4
ability to use a stable address when more address stability is ability to use a stable address when more address stability is
desired (e.g., for IPv6 addresses published in the DNS). desired (e.g., for IPv6 addresses published in the DNS).
[RFC3484] originally specified that stable addresses be used for [RFC3484] originally specified that stable addresses be used for
outbound connections unless an application explicitly prefers outbound connections unless an application explicitly prefers
temporary addresses. The default preference for stable addresses was temporary addresses. The default preference for stable addresses was
established to avoid applications potentially failing due to the established to avoid applications potentially failing due to the
short lifetime of temporary addresses or the possibility of a reverse short lifetime of temporary addresses or the possibility of a reverse
look-up failure or error. However, [RFC3484] allowed that look-up failure or error. However, [RFC3484] allowed that
"implementations for which privacy considerations outweigh these "implementations for which privacy considerations outweigh these
application compatibility concerns MAY reverse the sense of this application-compatibility concerns MAY reverse the sense of this
rule" and instead prefer by default temporary addresses rather than rule" and instead prefer by default temporary addresses rather than
stable addresses. Indeed most implementations (notably including stable addresses. Indeed, most implementations (notably including
Windows) chose to default to temporary addresses for outbound Windows) chose to default to temporary addresses for outbound
connections since privacy was considered more important (and few connections since privacy was considered more important (and few
applications supported IPv6 at the time, so application compatibility applications supported IPv6 at the time, so application compatibility
concerns were minimal). [RFC6724] then obsoleted [RFC3484] and concerns were minimal). [RFC6724] then obsoleted [RFC3484] and
changed the default to match what implementations actually did. changed the default to match what implementations actually did.
The envisioned relationship in [RFC3484] between stability of an The envisioned relationship in [RFC3484] between stability of an
address and its use in "public" can be misleading when conducting address and its use in "public" can be misleading when conducting
privacy analysis. The stability of an address and the extent to privacy analysis. The stability of an address and the extent to
which it is linkable to some other public identifier are independent which it is linkable to some other public identifier are independent
of one another. For example, there is nothing that prevents a host of one another. For example, there is nothing that prevents a host
from publishing a temporary address in a public place, such as the from publishing a temporary address in a public place, such as the
DNS. Publishing both a stable address and a temporary address in the DNS. Publishing both a stable address and a temporary address in the
DNS or elsewhere where t hey can be linked together by a public DNS or elsewhere where they can be linked together by a public
identifier allows the host's activities when using either address to identifier allows the host's activities when using either address to
be correlated together. be correlated together.
Moreover, because temporary addresses were designed to supplement Moreover, because temporary addresses were designed to supplement
other addresses generated by a host, the host may still configure a other addresses generated by a host, the host may still configure a
more stable address even if it only ever intentionally uses temporary more stable address even if it only ever intentionally uses temporary
addresses (as source addresses) for communication to off-link addresses (as source addresses) for communication to off-link
destinations. An attacker can probe for the stable address even if destinations. An attacker can probe for the stable address even if
it is never used as such a source address or advertised (e.g., in DNS it is never used as such a source address or advertised outside the
or SIP) outside the link. link (e.g., in DNS or SIP).
This section compares the privacy and security properties of a This section compares the privacy and security properties of a
variety of IID generation mechanisms and their possible usage variety of IID generation mechanisms and their possible usage
scenarios, including scenarios in which a single mechanism is used to scenarios, including scenarios in which a single mechanism is used to
generate all of a host's IIDs and those in which temporary addresses generate all of a host's IIDs and those in which temporary addresses
are used together with addresses generated using a different IID are used together with addresses generated using a different IID
generation mechanism. The analysis of the exposure of each IID type generation mechanism. The analysis of the exposure of each IID type
to correlation assumes that IPv6 prefixes are shared by a reasonably to correlation assumes that IPv6 prefixes are shared by a reasonably
large number of nodes. As [RFC4941] notes, if a very small number of large number of nodes. As [RFC4941] notes, if a very small number of
nodes (say, only one) use a particular prefix for an extended period nodes (say, only one) use a particular prefix for an extended period
of time, the prefix itself can be used to correlate the host's of time, the prefix itself can be used to correlate the host's
activities regardless of how the IID is generated. For example, activities regardless of how the IID is generated. For example,
[RFC3314] recommends that prefixes be uniquely assigned to mobile [RFC3314] recommends that prefixes be uniquely assigned to mobile
handsets where IPv6 is used within GPRS. In cases where this advice handsets where IPv6 is used within General Packet Radio Service
is followed and prefixes persist for extended periods of time (or get (GPRS). In cases where this advice is followed and prefixes persist
reassigned to the same handsets whenever those hand sets reconnect to for extended periods of time (or get reassigned to the same handsets
the same network router), hosts' activities could be correlatable for whenever those handsets reconnect to the same network router), hosts'
longer periods than the analysis below would suggest. activities could be correlatable for longer periods than the analysis
below would suggest.
The table below provides a summary of the whole analysis. A "No" The table below provides a summary of the whole analysis. A "No"
entry indicates that the attack is prevented from being carried out entry indicates that the attack is prevented from being carried out
on the basis of the IID, but the host may still be vulnerable on the basis of the IID, but the host may still be vulnerable
depending on how it employs other protocols. depending on how it employs other protocols.
+--------------+-------------+----------+-------------+-------------+ +--------------+-------------+----------+-------------+-------------+
| Mechanism(s) | Correlation | Location | Address | Device | | Mechanism(s) | Correlation | Location | Address | Device |
| | | tracking | scanning | exploits | | | | tracking | scanning | exploits |
+--------------+-------------+----------+-------------+-------------+ +--------------+-------------+----------+-------------+-------------+
skipping to change at page 9, line 40 skipping to change at page 9, line 45
| | | | | | | | | | | |
| Temporary | For temp | No | No | No | | Temporary | For temp | No | No | No |
| | address | | | | | | address | | | |
| | lifetime | | | | | | lifetime | | | |
| | | | | | | | | | | |
| DHCPv6 | For lease | No | Depends on | No | | DHCPv6 | For lease | No | Depends on | No |
| | lifetime | | generation | | | | lifetime | | generation | |
| | | | mechanism | | | | | | mechanism | |
+--------------+-------------+----------+-------------+-------------+ +--------------+-------------+----------+-------------+-------------+
Table 1: Privacy and security properties of IID generation mechanisms Table 1: Privacy and Security Properties of IID Generation Mechanisms
4.1. IEEE-identifier-based IIDs 4.1. IEEE-Identifier-Based IIDs
As discussed in Section 3, addresses that use IIDs based on IEEE As discussed in Section 3, addresses that use IIDs based on IEEE
identifiers are vulnerable to all four threats. They allow identifiers are vulnerable to all four attacks. They allow
correlation and location tracking for the lifetime of the device correlation and location tracking for the lifetime of the device
since IEEE identifiers last that long and their structure makes since IEEE identifiers last that long and their structure makes
address scanning and device exploits possible. address scanning and device exploits possible.
4.2. Static, manually configured IIDs 4.2. Static, Manually Configured IIDs
Because static, manually configured IIDs are stable, both correlation Because static, manually configured IIDs are stable, both correlation
and location tracking are possible for the life of the address. and location tracking are possible for the life of the address.
The extent to which location tracking can be successfully performed The extent to which location tracking can be successfully performed
depends, to a some extent, on the uniqueness of the employed IID. depends, to some extent, on the uniqueness of the employed IID. For
For example, one would expect "low byte" IIDs to be more widely example, one would expect "low byte" IIDs to be more widely reused
reused than, for example, IIDs where the whole 64-bits follow some than, for example, IIDs where the whole 64 bits follow some pattern
pattern that is unique to a specific organization. Widely reused that is unique to a specific organization. Widely reused IIDs will
IIDs will typically lead to false positives when performing location typically lead to false positives when performing location tracking.
tracking.
Whether manually configured addresses are vulnerable to address Whether manually configured addresses are vulnerable to address
scanning and device exploits depends on the specifics of how the IIDs scanning and device exploits depends on the specifics of how the IIDs
are generated. are generated.
4.3. Constant, semantically opaque IIDs 4.3. Constant, Semantically Opaque IIDs
Although a mechanism to generate a constant, semantically opaque IID Although a mechanism to generate a constant, semantically opaque IID
has not been standardized, it has been in wide use for many years on has not been standardized, it has been in wide use for many years on
at least one platform (Windows). Windows uses the [RFC4941] random at least one platform (Windows). Windows uses the random generation
generation mechanism in lieu of generating an IEEE-identifier-based mechanism described in [RFC4941] in lieu of generating an IEEE-
IID. This mitigates the device-specific exploitation and address identifier-based IID. This mitigates the device-specific
scanning attacks, but still allows correlation and location tracking exploitation and address-scanning attacks but still allows
because the IID is constant across IPv6 links and time. correlation and location tracking because the IID is constant across
IPv6 links and time.
4.4. Cryptographically generated IIDs 4.4. Cryptographically Generated IIDs
Cryptographically generated addresses (CGAs) [RFC3972] bind a hash of Cryptographically Generated Addresses (CGAs) [RFC3972] bind a hash of
the host's public key to an IPv6 address in the SEcure Neighbor the host's public key to an IPv6 address in the SEcure Neighbor
Discovery (SEND) [RFC3971] protocol. CGAs may be regenerated for Discovery (SEND) protocol [RFC3971]. CGAs may be regenerated for
each subnet prefix, but this is not required given that they are each subnet prefix, but this is not required given that they are
computationally expensive to generate. A host using a CGA can be computationally expensive to generate. A host using a CGA can be
correlated for as long as the lifetime of the combination of the correlated for as long as the lifetime of the combination of the
public key and the chosen modifier block, since it is possible to public key and the chosen modifier block since it is possible to
rotate modifier blocks without generating new public keys. Because rotate modifier blocks without generating new public keys. Because
the cryptographic hash of the host's public key uses the subnet the cryptographic hash of the host's public key uses the subnet
prefix as an input, even if the host does not generate a new public prefix as an input, even if the host does not generate a new public
key or modifier block when it moves to a different IPv6 link, its key or modifier block when it moves to a different IPv6 link, its
location cannot be tracked via the IID. CGAs do not allow device- location cannot be tracked via the IID. CGAs do not allow device-
specific exploitation or address scanning attacks. specific exploitation or address-scanning attacks.
4.5. Stable, semantically opaque IIDs 4.5. Stable, Semantically Opaque IIDs
[RFC7217] specifies an algorithm that generates, for each network [RFC7217] specifies an algorithm that generates, for each network
interface, a unique random IID per IPv6 link. The aforementioned interface, a unique random IID per IPv6 link. The aforementioned
algorithm is employed not only for global unicast addresses, but also algorithm is employed not only for global unicast addresses, but also
for unique local unicast addresses and link-local unicast addresses, for unique local unicast addresses and link-local unicast addresses
since these addresses may leak out via application protocols (e.g., since these addresses may leak out via application protocols (e.g.,
IPv6 addresses embedded in email headers). IPv6 addresses embedded in email headers).
A host that stays connected to the same IPv6 link could therefore be A host that stays connected to the same IPv6 link could therefore be
tracked at length, whereas a mobile host's activities could only be tracked at length, whereas a mobile host's activities could only be
correlated for the duration of each network connection. Location correlated for the duration of each network connection. Location
tracking is not possible with these addresses. They also do not tracking is not possible with these addresses. They also do not
allow device-specific exploitation or address scanning attacks. allow device-specific exploitation or address-scanning attacks.
4.6. Temporary IIDs 4.6. Temporary IIDs
A host that uses only a temporary address mitigates all four threats. A host that uses only a temporary address mitigates all four threats.
Its activities may only be correlated for the lifetime a single Its activities may only be correlated for the lifetime of a single
temporary address. temporary address.
A host that configures both an IEEE-identifier-based IID and A host that configures both an IEEE-identifier-based IID and
temporary addresses makes the host vulnerable to the same attacks as temporary addresses makes the host vulnerable to the same attacks as
if temporary addresses were not in use, although the viability of if temporary addresses were not in use, although the viability of
some of them depends on how the host uses each address. An attacker some of them depends on how the host uses each address. An attacker
can correlate all of the host's activities for which it uses its can correlate all of the host's activities for which it uses its
IEEE-identifier-based IID. Once an attacker has obtained the IEEE- IEEE-identifier-based IID. Once an attacker has obtained the IEEE-
identifier-based IID, location tracking becomes possible on other identifier-based IID, location tracking becomes possible on other
IPv6 links even if the host only makes use of temporary addresses on IPv6 links even if the host only makes use of temporary addresses on
those other IPv6 links; the attacker can actively probe the other those other IPv6 links; the attacker can actively probe the other
IPv6 links for the presence of the IEEE-identifier-based IID. IPv6 links for the presence of the IEEE-identifier-based IID.
Device-specific vulnerabilities can still be exploited. Address Device-specific vulnerabilities can still be exploited. Address
scanning is also still possible because the IEEE-identifier-based scanning is also still possible because the IEEE-identifier-based
address can be probed. address can be probed.
If the host instead generates a constant, semantically opaque IID to If the host instead generates a constant, semantically opaque IID to
use in a stable address for server-like connections together with use in a stable address for server-like connections together with
temporary addresses for outbound connections (as is the default in temporary addresses for outbound connections (as is the default in
Windows), it sees some improvements over the previous scenario. The Windows), it sees some improvements over the previous scenario. The
address scanning and device-specific exploitation attacks are no address-scanning attacks and device-specific exploitation attacks are
longer possible because the OUI is no longer embedded in any of the no longer possible because the OUI is no longer embedded in any of
host's addresses. However, correlation of some activities across the host's addresses. However, correlation of some activities across
time and location tracking are both s till possible because the time and location tracking are both still possible because the
semantically opaque IID is constant. And once an attacker has semantically opaque IID is constant. And once an attacker has
obtained the host's semantically opaque IID, location tracking is obtained the host's semantically opaque IID, location tracking is
possible on any network by probing for that IID, even if the host possible on any network by probing for that IID, even if the host
only uses temporary addresses on those networks. However, if the only uses temporary addresses on those networks. However, if the
host generates but never uses a constant, semantically opaque IID, it host generates but never uses a constant, semantically opaque IID, it
mitigates all four threats. mitigates all four threats.
When used together with temporary addresses, the stable, semantically When used together with temporary addresses, the stable, semantically
opaque IID generation mechanism [RFC7217] improves upon the previous opaque IID generation mechanism [RFC7217] improves upon the previous
scenario by limiting the potential for correlation to the lifetime of scenario by limiting the potential for correlation to the lifetime of
the stable address (which may still be lengthy for hosts that are not the stable address (which may still be lengthy for hosts that are not
mobile) and by eliminating the possibility for location tracking mobile) and by eliminating the possibility for location tracking
(since a different IID is generated for each subnet prefix). As in (since a different IID is generated for each subnet prefix). As in
the previous scenario, a host that configures but does not use a the previous scenario, a host that configures but does not use a
stable, semant ically opaque address mitigates all four threats. stable, semantically opaque address mitigates all four threats.
4.7. DHCPv6 generation of IIDs 4.7. DHCPv6 Generation of IIDs
The security/privacy implications of DHCPv6-based addresses will The security and privacy implications of DHCPv6-based addresses will
typically depend on whether the client requests an IA_NA (Identity typically depend on whether the client requests an IA_NA (Identity
Association for Non-temporary Addresses) or an IA_TA ( Identity Association for Non-temporary Addresses) or an IA_TA (Identity
Association for Temporary Addresses) [RFC3315] and the specific Association for Temporary Addresses) [RFC3315] and the specific
DHCPv6 server software being employed. DHCPv6 server software being employed.
DHCPv6 temporary addresses have the same properties as SLAAC DHCPv6 temporary addresses have the same properties as SLAAC
temporary addresses Section 4.6 [RFC4941]. On the other hand, the temporary addresses (see Section 4.6). On the other hand, the
properties of DHCPv6 non-temporary addresses typically depend on the properties of DHCPv6 non-temporary addresses typically depend on the
specific DHCPv6 server software being employed. Recent releases of specific DHCPv6 server software being employed. Recent releases of
most popular DHCPv6 server software typically lease random addresses most popular DHCPv6 server software typically lease random addresses
with a similar lease time as that of IPv4. Thus, these addresses can with a similar lease time as that of IPv4. Thus, these addresses can
be considered to be "stable, semantically opaque". be considered to be "stable, semantically opaque". [DHCPv6-IID]
[I-D.ietf-dhc-stable-privacy-addresses] specifies an algorithm that specifies an algorithm that can be employed by DHCPv6 servers to
can be employed by DHCPv6 servers to generate "stable, semantically generate "stable, semantically opaque" addresses.
opaque" addresses.
On the other hand, some DHCPv6 software leases sequential addresses On the other hand, some DHCPv6 software leases sequential addresses
(typically low-byte addresses). These addresses can be considered to (typically low-byte addresses). These addresses can be considered to
be stable addresses. The drawback of this address generation scheme be stable addresses. The drawback of this address generation scheme
compared to "stable, semantically opaque" addresses is that, since compared to "stable, semantically opaque" addresses is that, since
they follow specific patterns, they enable IPv6 address scans. they follow specific patterns, they enable IPv6 address scans.
4.8. Transition/co-existence technologies 4.8. Transition and Coexistence Technologies
Addresses specified based on transition/co-existence technologies Addresses specified based on transition or coexistence technologies
that embed an IPv4 address within an IPv6 address are not included in that embed an IPv4 address within an IPv6 address are not included in
Table 1 because their privacy and security properties are inherited Table 1 because their privacy and security properties are inherited
from the embedded address. For example, Teredo [RFC4380] specifies a from the embedded address. For example, Teredo [RFC4380] specifies a
means to generate an IPv6 address from the underlying IPv4 address means to generate an IPv6 address from the underlying IPv4 address
and port, leaving many other bits set to zero. This makes it and port, leaving many other bits set to zero. This makes it
relatively easy for an attacker to scan for IPv6 addresses by relatively easy for an attacker to scan for IPv6 addresses by
guessing the Teredo client's IPv4 address and port (which for many guessing the Teredo client's IPv4 address and port (which for many
NATs is not randomized). For this reason, popular implementations NATs is not randomized). For this reason, popular implementations
(e.g., Windows), began deviating from the standard by including 12 (e.g., Windows) began deviating from the standard by including 12
random bits in place of zero bits. This modification was later random bits in place of zero bits. This modification was later
standardized in [RFC5991]. standardized in [RFC5991].
Some other transition technologies (e.g., [RFC5214], [RFC6052]) Some other transition technologies (e.g., [RFC5214], [RFC6052])
specify means to generate an IPv6 address from an underlying IPv4 specify means to generate an IPv6 address from an underlying IPv4
address without a port. Such mechanisms thus make it much easier for address without a port. Such mechanisms thus make it much easier for
an attacker to conduct an address scan than for mechanisms that an attacker to conduct an address scan than for mechanisms that
require finding a port number as well. require finding a port number as well.
Finally, still other mechanisms (e.g., [RFC7596], [RFC7597], Finally, still other mechanisms (e.g., [RFC7596], [RFC7597],
[RFC7599]) are somewhere in between, using an IPv4 address and a port [RFC7599]) are somewhere in between, using an IPv4 address and a port
set ID (which for many NATs is not randomized). In general, such set ID (which for many NATs is not randomized). In general, such
mechanisms are thus typically as easy to scan as in the Teredo mechanisms are thus typically as easy to scan as in the Teredo
example above without the 12-bit mitigation. example above without the 12-bit mitigation.
5. Miscellaneous Issues with IPv6 addressing 5. Miscellaneous Issues with IPv6 Addressing
5.1. Network Operation 5.1. Network Operation
It is generally agreed that IPv6 addresses that vary over time in a It is generally agreed that IPv6 addresses that vary over time in a
specific IPv6 link tend to increase the complexity of event logging, specific IPv6 link tend to increase the complexity of event logging,
trouble-shooting, enforcement of access controls and quality of trouble-shooting, enforcement of access controls and quality of
service, etc. As a result, some organizations disable the use of service, etc. As a result, some organizations disable the use of
temporary addresses [RFC4941] even at the expense of reduced privacy temporary addresses [RFC4941] even at the expense of reduced privacy
[Broersma]. [Broersma].
5.2. Compliance 5.2. Compliance
Some IPv6 compliance testing suites required (and might still Some IPv6 compliance testing suites required (and might still
require) implementations to support IEEE-identifier-based IIDS in require) implementations to support IEEE-identifier-based IIDs in
order to be approved as compliant. This document recommends that order to be approved as compliant. This document recommends that
compliance testing suites be relaxed to allow other forms of address compliance testing suites be relaxed to allow other forms of address
generation that are more amenable to privacy. generation that are more amenable to privacy.
5.3. Intellectual Property Rights (IPRs) 5.3. Intellectual Property Rights (IPRs)
Some IPv6 addressing techniques might be covered by Intellectual Some IPv6 addressing techniques might be covered by Intellectual
Property rights, which might limit their implementation in different Property rights, which might limit their implementation in different
Operating Systems. [CGA-IPR] and [KAME-CGA] discuss the IPRs on operating systems. [CGA-IPR] and [KAME-CGA] discuss the IPRs on
CGAs. CGAs.
6. Security Considerations 6. Security Considerations
This whole document concerns the privacy and security properties of This whole document concerns the privacy and security properties of
different IPv6 address generation mechanisms. different IPv6 address generation mechanisms.
7. IANA Considerations 7. References
This document does not require actions by IANA.
8. Acknowledgements
The authors would like to thank Bernard Aboba, Brian Carpenter, Tim
Chown, Lorenzo Colitti, Rich Draves, Robert Hinden, Robert Moskowitz,
Erik Nordmark, Mark Smith, Ole Troan, and James Woodyatt for
providing valuable comments on earlier versions of this document.
9. References
9.1. Normative References 7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998,
<http://www.rfc-editor.org/info/rfc2464>. <http://www.rfc-editor.org/info/rfc2464>.
skipping to change at page 15, line 24 skipping to change at page 15, line 20
[RFC7136] Carpenter, B. and S. Jiang, "Significance of IPv6 [RFC7136] Carpenter, B. and S. Jiang, "Significance of IPv6
Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136, Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136,
February 2014, <http://www.rfc-editor.org/info/rfc7136>. February 2014, <http://www.rfc-editor.org/info/rfc7136>.
[RFC7217] Gont, F., "A Method for Generating Semantically Opaque [RFC7217] Gont, F., "A Method for Generating Semantically Opaque
Interface Identifiers with IPv6 Stateless Address Interface Identifiers with IPv6 Stateless Address
Autoconfiguration (SLAAC)", RFC 7217, Autoconfiguration (SLAAC)", RFC 7217,
DOI 10.17487/RFC7217, April 2014, DOI 10.17487/RFC7217, April 2014,
<http://www.rfc-editor.org/info/rfc7217>. <http://www.rfc-editor.org/info/rfc7217>.
9.2. Informative References 7.2. Informative References
[Broersma] [Broersma] Broersma, R., "IPv6 Everywhere: Living with a Fully
Broersma, R., "IPv6 Everywhere: Living with a Fully
IPv6-enabled environment", Australian IPv6 Summit 2010, IPv6-enabled environment", Australian IPv6 Summit 2010,
Melbourne, VIC Australia, October 2010, October 2010, Melbourne, VIC Australia, October 2010,
<http://www.ipv6.org.au/10ipv6summit/talks/ <http://www.ipv6.org.au/10ipv6summit/talks/
Ron_Broersma.pdf>. Ron_Broersma.pdf>.
[CGA-IPR] IETF, "Intellectual Property Rights on RFC 3972", 2005, [CGA-IPR] IETF, "IPR Details: Microsoft's Statement about IPR
claimed in RFC 3972", November 2005,
<https://datatracker.ietf.org/ipr/676/>. <https://datatracker.ietf.org/ipr/676/>.
[I-D.ietf-dhc-stable-privacy-addresses] [DHCPv6-IID]
Gont, F. and S. LIU, "A Method for Generating Semantically Gont, F. and W. Liu, "A Method for Generating Semantically
Opaque Interface Identifiers with Dynamic Host Opaque Interface Identifiers with Dynamic Host
Configuration Protocol for IPv6 (DHCPv6)", draft-ietf-dhc- Configuration Protocol for IPv6 (DHCPv6)", Work in
stable-privacy-addresses-02 (work in progress), April Progress, draft-ietf-dhc-stable-privacy-addresses-02,
2015. April 2015.
[I-D.ietf-opsec-ipv6-host-scanning]
Gont, F. and T. Chown, "Network Reconnaissance in IPv6
Networks", draft-ietf-opsec-ipv6-host-scanning-08 (work in
progress), August 2015.
[KAME-CGA] [KAME-CGA] The KAME Project, "The KAME IPR policy and concerns of
KAME, "The KAME IPR policy and concerns of some some technologies which have IPR claims", November 2005,
technologies which have IPR claims", 2005,
<http://www.kame.net/newsletter/20040525/>. <http://www.kame.net/newsletter/20040525/>.
[Microsoft] [Microsoft]
Microsoft, "IPv6 interface identifiers", 2013, <target='ht Microsoft, "IPv6 interface identifiers", 2013,
tp://www.microsoft.com/resources/documentation/windows/xp/ <http://www.microsoft.com/resources/documentation/
all/proddocs/en-us/sag_ip_v6_imp_addr7.mspx?mfr=true>. windows/xp/all/proddocs/en-us/
sag_ip_v6_imp_addr7.mspx?mfr=true>.
[Panopticlick] [Panopticlick]
Electronic Frontier Foundation, "Panopticlick", 2011, Electronic Frontier Foundation, "Panopticlick", 2011,
<http://panopticlick.eff.org>. <http://panopticlick.eff.org>.
[RFC1971] Thomson, S. and T. Narten, "IPv6 Stateless Address [RFC1971] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 1971, DOI 10.17487/RFC1971, August Autoconfiguration", RFC 1971, DOI 10.17487/RFC1971, August
1996, <http://www.rfc-editor.org/info/rfc1971>. 1996, <http://www.rfc-editor.org/info/rfc1971>.
[RFC1972] Crawford, M., "A Method for the Transmission of IPv6 [RFC1972] Crawford, M., "A Method for the Transmission of IPv6
skipping to change at page 17, line 37 skipping to change at page 17, line 33
Murakami, T., and T. Taylor, Ed., "Mapping of Address and Murakami, T., and T. Taylor, Ed., "Mapping of Address and
Port with Encapsulation (MAP-E)", RFC 7597, Port with Encapsulation (MAP-E)", RFC 7597,
DOI 10.17487/RFC7597, July 2015, DOI 10.17487/RFC7597, July 2015,
<http://www.rfc-editor.org/info/rfc7597>. <http://www.rfc-editor.org/info/rfc7597>.
[RFC7599] Li, X., Bao, C., Dec, W., Ed., Troan, O., Matsushima, S., [RFC7599] Li, X., Bao, C., Dec, W., Ed., Troan, O., Matsushima, S.,
and T. Murakami, "Mapping of Address and Port using and T. Murakami, "Mapping of Address and Port using
Translation (MAP-T)", RFC 7599, DOI 10.17487/RFC7599, July Translation (MAP-T)", RFC 7599, DOI 10.17487/RFC7599, July
2015, <http://www.rfc-editor.org/info/rfc7599>. 2015, <http://www.rfc-editor.org/info/rfc7599>.
[RFC7707] Gont, F. and T. Chown, "Network Reconnaissance in IPv6
Networks", RFC 7707, DOI 10.17487/RFC7707, March 2016,
<http://www.rfc-editor.org/info/rfc7707>.
Acknowledgements
The authors would like to thank Bernard Aboba, Brian Carpenter, Tim
Chown, Lorenzo Colitti, Rich Draves, Robert Hinden, Robert Moskowitz,
Erik Nordmark, Mark Smith, Ole Troan, and James Woodyatt for
providing valuable comments on earlier draft versions of this
document.
Authors' Addresses Authors' Addresses
Alissa Cooper Alissa Cooper
Cisco Cisco
707 Tasman Drive 707 Tasman Drive
Milpitas, CA 95035 Milpitas, CA 95035
US United States
Phone: +1-408-902-3950 Phone: +1-408-902-3950
Email: alcoop@cisco.com Email: alcoop@cisco.com
URI: https://www.cisco.com/ URI: https://www.cisco.com/
Fernando Gont Fernando Gont
Huawei Technologies Huawei Technologies
Evaristo Carriego 2644 Evaristo Carriego 2644
Haedo, Provincia de Buenos Aires 1706 Haedo, Provincia de Buenos Aires 1706
Argentina Argentina
Phone: +54 11 4650 8472 Phone: +54 11 4650 8472
Email: fgont@si6networks.com Email: fgont@si6networks.com
URI: http://www.si6networks.com URI: http://www.si6networks.com
skipping to change at page 18, line 16 skipping to change at page 18, line 37
Evaristo Carriego 2644 Evaristo Carriego 2644
Haedo, Provincia de Buenos Aires 1706 Haedo, Provincia de Buenos Aires 1706
Argentina Argentina
Phone: +54 11 4650 8472 Phone: +54 11 4650 8472
Email: fgont@si6networks.com Email: fgont@si6networks.com
URI: http://www.si6networks.com URI: http://www.si6networks.com
Dave Thaler Dave Thaler
Microsoft Microsoft
Microsoft Corporation
One Microsoft Way One Microsoft Way
Redmond, WA 98052 Redmond, WA 98052
United States
Phone: +1 425 703 8835 Phone: +1 425 703 8835
Email: dthaler@microsoft.com Email: dthaler@microsoft.com
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