draft-ietf-6man-rfc4941bis-12.txt   rfc8981.txt 
IPv6 Maintenance (6man) Working Group F. Gont Internet Engineering Task Force (IETF) F. Gont
Internet-Draft SI6 Networks Request for Comments: 8981 SI6 Networks
Obsoletes: 4941 (if approved) S. Krishnan Obsoletes: 4941 S. Krishnan
Intended status: Standards Track Kaloom Category: Standards Track Kaloom
Expires: May 6, 2021 T. Narten ISSN: 2070-1721 T. Narten
R. Draves R. Draves
Microsoft Research Microsoft Research
November 2, 2020 February 2021
Temporary Address Extensions for Stateless Address Autoconfiguration in Temporary Address Extensions for Stateless Address Autoconfiguration in
IPv6 IPv6
draft-ietf-6man-rfc4941bis-12
Abstract Abstract
This document describes an extension to IPv6 Stateless Address This document describes an extension to IPv6 Stateless Address
Autoconfiguration that causes hosts to generate global scope Autoconfiguration that causes hosts to generate temporary addresses
addresses with randomized interface identifiers that change over with randomized interface identifiers for each prefix advertised with
time. Changing global scope addresses over time limits the window of autoconfiguration enabled. Changing addresses over time limits the
time during which eavesdroppers and other information collectors may window of time during which eavesdroppers and other information
trivially perform address-based network activity correlation when the collectors may trivially perform address-based network-activity
same address is employed for multiple transactions by the same host. correlation when the same address is employed for multiple
Additionally, it reduces the window of exposure of a host as being transactions by the same host. Additionally, it reduces the window
accessible via an address that becomes revealed as a result of active of exposure of a host as being accessible via an address that becomes
communication. This document obsoletes RFC4941. revealed as a result of active communication. This document
obsoletes RFC 4941.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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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). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on May 6, 2021. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8981.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology
1.2. Problem Statement . . . . . . . . . . . . . . . . . . . . 4 1.2. Problem Statement
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Background
2.1. Extended Use of the Same Identifier . . . . . . . . . . . 4 2.1. Extended Use of the Same Identifier
2.2. Possible Approaches . . . . . . . . . . . . . . . . . . . 6 2.2. Possible Approaches
3. Protocol Description . . . . . . . . . . . . . . . . . . . . 6 3. Protocol Description
3.1. Design Guidelines . . . . . . . . . . . . . . . . . . . . 7 3.1. Design Guidelines
3.2. Assumptions . . . . . . . . . . . . . . . . . . . . . . . 7 3.2. Assumptions
3.3. Generation of Randomized Interface Identifiers . . . . . 8 3.3. Generation of Randomized IIDs
3.3.1. Simple Randomized Interface Identifiers . . . . . . . 8 3.3.1. Simple Randomized IIDs
3.3.2. Hash-based Generation of Randomized Interface 3.3.2. Generation of IIDs with Pseudorandom Functions
Identifiers . . . . . . . . . . . . . . . . . . . . . 9 3.4. Generating Temporary Addresses
3.4. Generating Temporary Addresses . . . . . . . . . . . . . 11 3.5. Expiration of Temporary Addresses
3.5. Expiration of Temporary Addresses . . . . . . . . . . . . 12 3.6. Regeneration of Temporary Addresses
3.6. Regeneration of Temporary Addresses . . . . . . . . . . . 13 3.7. Implementation Considerations
3.7. Implementation Considerations . . . . . . . . . . . . . . 14 3.8. Defined Protocol Parameters and Configuration Variables
3.8. Defined Constants and Configuration Variables . . . . . . 14 4. Implications of Changing IIDs
4. Implications of Changing Interface Identifiers . . . . . . . 15 5. Significant Changes from RFC 4941
5. Significant Changes from RFC4941 . . . . . . . . . . . . . . 17 6. Future Work
6. Future Work . . . . . . . . . . . . . . . . . . . . . . . . . 18 7. IANA Considerations
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 19 8. Security Considerations
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 9. References
9. Security Considerations . . . . . . . . . . . . . . . . . . . 19 9.1. Normative References
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 9.2. Informative References
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 Acknowledgments
11.1. Normative References . . . . . . . . . . . . . . . . . . 21 Authors' Addresses
11.2. Informative References . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction 1. Introduction
[RFC4862] specifies "Stateless Address Autoconfiguration (SLAAC) for [RFC4862] specifies Stateless Address Autoconfiguration (SLAAC) for
IPv6", which typically results in hosts configuring one or more IPv6, which typically results in hosts configuring one or more
"stable" IPv6 addresses composed of a network prefix advertised by a "stable" IPv6 addresses composed of a network prefix advertised by a
local router and a locally-generated Interface Identifier (IID). The local router and a locally generated interface identifier (IID). The
security and privacy implications of such addresses have been security and privacy implications of such addresses have been
discussed in detail in [RFC7721], [RFC7217], and [RFC7707]. This discussed in detail in [RFC7721], [RFC7217], and [RFC7707]. This
document specifies an extension for SLAAC to generate temporary document specifies an extension to SLAAC for generating temporary
addresses, that can help mitigate some of the aforementioned issues. addresses that can help mitigate some of the aforementioned issues.
This is a revision of RFC4941, and formally obsoletes RFC4941. This document is a revision of RFC 4941 and formally obsoletes it.
Section 5 describes the changes from [RFC4941]. Section 5 describes the changes from [RFC4941].
The default address selection for IPv6 has been specified in The default address selection for IPv6 has been specified in
[RFC6724]. The determination as to whether to use stable versus [RFC6724]. In some cases, the determination as to whether to use
temporary addresses can in some cases only be made by an application. stable versus temporary addresses can only be made by an application.
For example, some applications may always want to use temporary For example, some applications may always want to use temporary
addresses, while others may want to use them only in some addresses, while others may want to use them only in some
circumstances or not at all. An Application Programming Interface circumstances or not at all. An Application Programming Interface
(API) such as that specified in [RFC5014] can enable individual (API) such as that specified in [RFC5014] can enable individual
applications to indicate a preference for the use of temporary applications to indicate a preference for the use of temporary
addresses. addresses.
Section 2 provides background information. Section 3 describes a Section 2 provides background information. Section 3 describes a
procedure for generating temporary addresses. Section 4 discusses procedure for generating temporary addresses. Section 4 discusses
implications of changing interface identifiers (IIDs). Section 5 implications of changing IIDs. Section 5 describes the changes from
describes the changes from [RFC4941]. [RFC4941].
1.1. Terminology 1.1. Terminology
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 BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
The terms "public address", "stable address", "temporary address", The terms "public address", "stable address", "temporary address",
"constant IID", "stable IID", and "temporary IID" are to be "constant IID", "stable IID", and "temporary IID" are to be
interpreted as specified in [RFC7721]. interpreted as specified in [RFC7721].
The term "global scope addresses" is used in this document to The term "global-scope addresses" is used in this document to
collectively refer to "Global unicast addresses" as defined in collectively refer to "Global unicast addresses" as defined in
[RFC4291] and "Unique local addresses" as defined in [RFC4193], and [RFC4291] and "Unique local addresses" as defined in [RFC4193], and
not to "globally reachable" addresses, as defined in [RFC8190]. not to "globally reachable addresses" as defined in [RFC8190].
1.2. Problem Statement 1.2. Problem Statement
Addresses generated using stateless address autoconfiguration Addresses generated using SLAAC [RFC4862] contain an embedded
[RFC4862] contain an embedded interface identifier, which may remain interface identifier, which may remain stable over time. Anytime a
stable over time. Anytime a fixed identifier is used in multiple fixed identifier is used in multiple contexts, it becomes possible to
contexts, it becomes possible to correlate seemingly unrelated correlate seemingly unrelated activity using this identifier.
activity using this identifier.
The correlation can be performed by The correlation can be performed by:
o An attacker who is in the path between the host in question and * An attacker who is in the path between the host in question and
the peer(s) to which it is communicating, and who can view the the peer(s) to which it is communicating, who can view the IPv6
IPv6 addresses present in the datagrams. addresses present in the datagrams.
o An attacker who can access the communication logs of the peers * An attacker who can access the communication logs of the peers
with which the host has communicated. with which the host has communicated.
Since the identifier is embedded within the IPv6 address, it cannot Since the identifier is embedded within the IPv6 address, it cannot
be hidden. This document proposes a solution to this issue by be hidden. This document proposes a solution to this issue by
generating interface identifiers that vary over time. generating interface identifiers that vary over time.
Note that an attacker, who is on path, may be able to perform Note that an attacker, who is on path, may be able to perform
significant correlation based on: significant correlation based on:
o The payload contents of unencrypted packets on the wire * The payload contents of unencrypted packets on the wire.
o The characteristics of the packets such as packet size and timing * The characteristics of the packets, such as packet size and
timing.
Use of temporary addresses will not prevent such correlation, nor Use of temporary addresses will not prevent such correlation, nor
will it prevent an on-link observer (e.g. the host's default router) will it prevent an on-link observer (e.g., the host's default router)
from tracking all the host's addresses. from tracking all the host's addresses.
2. Background 2. Background
This section discusses the problem in more detail, provides context This section discusses the problem in more detail, provides context
for evaluating the significance of the concerns in specific for evaluating the significance of the concerns in specific
environments, and makes comparisons with existing practices. environments, and makes comparisons with existing practices.
2.1. Extended Use of the Same Identifier 2.1. Extended Use of the Same Identifier
The use of a non-changing interface identifier to form addresses is a The use of a non-changing IID to form addresses is a specific
specific instance of the more general case where a constant instance of the more general case where a constant identifier is
identifier is reused over an extended period of time and in multiple reused over an extended period of time and in multiple independent
independent activities. Any time the same identifier is used in activities. Anytime the same identifier is used in multiple
multiple contexts, it becomes possible for that identifier to be used contexts, it becomes possible for that identifier to be used to
to correlate seemingly unrelated activity. For example, a network correlate seemingly unrelated activity. For example, a network
sniffer placed strategically on a link across which all traffic to/ sniffer placed strategically on a link traversed by all traffic to/
from a particular host crosses could keep track of which destinations from a particular host could keep track of which destinations a host
a host communicated with and at what times. Such information can in communicated with and at what times. In some cases, such information
some cases be used to infer things, such as what hours an employee can be used to infer things, such as what hours an employee was
was active, when someone is at home, etc. Although it might appear active, when someone is at home, etc. Although it might appear that
that changing an address regularly in such environments would be changing an address regularly in such environments would be desirable
desirable to lessen privacy concerns, it should be noted that the to lessen privacy concerns, it should be noted that the network-
network prefix portion of an address also serves as a constant prefix portion of an address also serves as a constant identifier.
identifier. All hosts at, say, a home, would have the same network All hosts at, say, a home would have the same network prefix, which
prefix, which identifies the topological location of those hosts. identifies the topological location of those hosts. This has
This has implications for privacy, though not at the same granularity implications for privacy, though not at the same granularity as the
as the concern that this document addresses. Specifically, all hosts concern that this document addresses. Specifically, all hosts within
within a home could be grouped together for the purposes of a home could be grouped together for the purposes of collecting
collecting information. If the network contains a very small number information. If the network contains a very small number of hosts --
of hosts, say, just one, changing just the interface identifier will say, just one -- changing just the IID will not enhance privacy,
not enhance privacy, since the prefix serves as a constant since the prefix serves as a constant identifier.
identifier.
One of the requirements for correlating seemingly unrelated One of the requirements for correlating seemingly unrelated
activities is the use (and reuse) of an identifier that is activities is the use (and reuse) of an identifier that is
recognizable over time within different contexts. IP addresses recognizable over time within different contexts. IP addresses
provide one obvious example, but there are more. For example, provide one obvious example, but there are more. For example:
o Many hosts also have DNS names associated with their addresses, in * Many hosts also have DNS names associated with their addresses, in
which case the DNS name serves as a similar identifier. Although which case, the DNS name serves as a similar identifier. Although
the DNS name associated with an address is more work to obtain (it the DNS name associated with an address is more work to obtain (it
may require a DNS query), the information is often readily may require a DNS query), the information is often readily
available. In such cases, changing the address on a host over available. In such cases, changing the address on a host over
time would do little to address the concerns raised in this time would do little to address the concerns raised in this
document, unless the DNS name is changed at the same time as well document, unless the DNS name is also changed at the same time
(see Section 4). (see Section 4).
o Web browsers and servers typically exchange "cookies" with each * Web browsers and servers typically exchange "cookies" with each
other [RFC6265]. Cookies allow web servers to correlate a current other [RFC6265]. Cookies allow web servers to correlate a current
activity with a previous activity. One common usage is to send activity with a previous activity. One common usage is to send
back targeted advertising to a user by using the cookie supplied back targeted advertising to a user by using the cookie supplied
by the browser to identify what earlier queries had been made by the browser to identify what earlier queries had been made
(e.g., for what type of information). Based on the earlier (e.g., for what type of information). Based on the earlier
queries, advertisements can be targeted to match the (assumed) queries, advertisements can be targeted to match the (assumed)
interests of the end-user. interests of the end user.
The use of a constant identifier within an address is of special The use of a constant identifier within an address is of special
concern because addresses are a fundamental requirement of concern, because addresses are a fundamental requirement of
communication and cannot easily be hidden from eavesdroppers and communication and cannot easily be hidden from eavesdroppers and
other parties. Even when higher layers encrypt their payloads, other parties. Even when higher layers encrypt their payloads,
addresses in packet headers appear in the clear. Consequently, if a addresses in packet headers appear in the clear. Consequently, if a
mobile host (e.g., laptop) accessed the network from several mobile host (e.g., laptop) accessed the network from several
different locations, an eavesdropper might be able to track the different locations, an eavesdropper might be able to track the
movement of that mobile host from place to place, even if the upper movement of that mobile host from place to place, even if the upper-
layer payloads were encrypted. layer payloads were encrypted.
Changing global scope addresses over time limits the time window over Changing addresses over time limits the time window over which
which eavesdroppers and other information collectors may trivially eavesdroppers and other information collectors may trivially
correlate network activity when the same address is employed for correlate network activity when the same address is employed for
multiple transactions by the same host. Additionally, it reduces the multiple transactions by the same host. Additionally, it reduces the
window of exposure of a host as being accessible via an address that window of exposure during which a host is accessible via an address
becomes revealed as a result of active communication. that becomes revealed as a result of active communication.
The security and privacy implications of IPv6 addresses are discussed The security and privacy implications of IPv6 addresses are discussed
in detail in [RFC7721], [RFC7707], and [RFC7217]. in detail in [RFC7721], [RFC7707], and [RFC7217].
2.2. Possible Approaches 2.2. Possible Approaches
One approach, compatible with the stateless address autoconfiguration One approach, compatible with the SLAAC architecture, would be to
architecture, would be to change the interface identifier portion of change the IID portion of an address over time. Changing the IID can
an address over time. Changing the interface identifier can make it make it more difficult to look at the IP addresses in independent
more difficult to look at the IP addresses in independent
transactions and identify which ones actually correspond to the same transactions and identify which ones actually correspond to the same
host, both in the case where the routing prefix portion of an address host, both in the case where the routing-prefix portion of an address
changes and when it does not. changes and when it does not.
Many hosts function as both clients and servers. In such cases, the Many hosts function as both clients and servers. In such cases, the
host would need a name (e.g. a DNS domain name) for its use as a host would need a name (e.g., a DNS domain name) for its use as a
server. Whether the address stays fixed or changes has little server. Whether the address stays fixed or changes has little impact
privacy implication since the name remains constant and serves as a on privacy, since the name remains constant and serves as a constant
constant identifier. When acting as a client (e.g., initiating identifier. However, when acting as a client (e.g., initiating
communication), however, such a host may want to vary the addresses communication), such a host may want to vary the addresses it uses.
it uses. In such environments, one may need multiple addresses: a In such environments, one may need multiple addresses: a stable
stable address associated with the name, that is used to accept address associated with the name, which is used to accept incoming
incoming connection requests from other hosts, and a temporary connection requests from other hosts, and a temporary address used to
address used to shield the identity of the client when it initiates shield the identity of the client when it initiates communication.
communication.
On the other hand, a host that functions only as a client may want to On the other hand, a host that functions only as a client may want to
employ only temporary addresses for public communication. employ only temporary addresses for public communication.
To make it difficult to make educated guesses as to whether two To make it difficult to make educated guesses as to whether two
different interface identifiers belong to the same host, the different IIDs belong to the same host, the algorithm for generating
algorithm for generating alternate identifiers must include input alternate identifiers must include input that has an unpredictable
that has an unpredictable component from the perspective of the component from the perspective of the outside entities that are
outside entities that are collecting information. collecting information.
3. Protocol Description 3. Protocol Description
The following subsections define the procedures for the generation of The following subsections define the procedures for the generation of
IPv6 temporary addresses. IPv6 temporary addresses.
3.1. Design Guidelines 3.1. Design Guidelines
Temporary addresses observe the following properties: Temporary addresses observe the following properties:
1. Temporary addresses are typically employed for initiating 1. Temporary addresses are typically employed for initiating
outgoing sessions. outgoing sessions.
2. Temporary addresses are used for a short period of time 2. Temporary addresses are used for a short period of time
(typically hours to days) and are subsequently deprecated. (typically hours to days) and are subsequently deprecated.
Deprecated addresses can continue to be used for established Deprecated addresses can continue to be used for established
connections, but are not used to initiate new connections. connections but are not used to initiate new connections.
3. New temporary addresses are generated over time to replace 3. New temporary addresses are generated over time to replace
temporary addresses that expire. temporary addresses that expire (i.e., become deprecated and
eventually invalidated).
4. Temporary addresses must have a limited lifetime (limited "valid 4. Temporary addresses must have a limited lifetime (limited "valid
lifetime" and "preferred lifetime" from [RFC4862]). The lifetime lifetime" and "preferred lifetime" from [RFC4862]). The lifetime
of an address should be further reduced when privacy-meaningful of an address should be further reduced when privacy-meaningful
events (such as a host attaching to a different network, or the events (such as a host attaching to a different network, or the
regeneration of a new randomized MAC address) takes place. The regeneration of a new randomized Media Access Control (MAC)
lifetime of temporary addresses must be statistically different address) take place. The lifetime of temporary addresses must be
for different addresses, such that it is hard to predict or infer statistically different for different addresses, such that it is
when a new temporary address is generated, or correlate a newly- hard to predict or infer when a new temporary address is
generated address with an existing one. generated or correlate a newly generated address with an existing
one.
5. By default, one address is generated for each prefix advertised 5. By default, one address is generated for each prefix advertised
by stateless address autoconfiguration. The resulting Interface by SLAAC. The resulting interface identifiers must be
Identifiers must be statistically different when addresses are statistically different when addresses are configured for
configured for different prefixes or different network different prefixes or different network interfaces. This means
interfaces. This means that, given two addresses, it must be that, given two addresses, it must be difficult for an outside
difficult for an outside entity to infer whether the addresses entity to infer whether the addresses correspond to the same host
correspond to the same host or network interface. or network interface.
6. It must be difficult for an outside entity to predict the 6. It must be difficult for an outside entity to predict the
Interface Identifiers that will be employed for temporary interface identifiers that will be employed for temporary
addresses, even with knowledge of the algorithm/method employed addresses, even with knowledge of the algorithm/method employed
to generate them and/or knowledge of the Interface Identifiers to generate them and/or knowledge of the IIDs previously employed
previously employed for other temporary addresses. These for other temporary addresses. These IIDs must be semantically
Interface Identifiers must be semantically opaque [RFC7136] and opaque [RFC7136] and must not follow any specific patterns.
must not follow any specific patterns.
3.2. Assumptions 3.2. Assumptions
The following algorithm assumes that for a given temporary address, The following algorithm assumes that, for a given temporary address,
an implementation can determine the prefix from which it was an implementation can determine the prefix from which it was
generated. When a temporary address is deprecated, a new temporary generated. When a temporary address is deprecated, a new temporary
address is generated. The specific valid and preferred lifetimes for address is generated. The specific valid and preferred lifetimes for
the new address are dependent on the corresponding lifetime values the new address are dependent on the corresponding lifetime values
set for the prefix from which it was generated. set for the prefix from which it was generated.
Finally, this document assumes that when a host initiates outgoing Finally, this document assumes that, when a host initiates outgoing
communication, temporary addresses can be given preference over communications, temporary addresses can be given preference over
stable addresses (if available), when the device is configured to do stable addresses (if available), when the device is configured to do
so. [RFC6724] mandates implementations to provide a mechanism, which so. [RFC6724] mandates that implementations provide a mechanism that
allows an application to configure its preference for temporary allows an application to configure its preference for temporary
addresses over stable addresses. It also allows for an addresses over stable addresses. It also allows an implementation to
implementation to prefer temporary addresses by default, so that the prefer temporary addresses by default, so that the connections
connections initiated by the host can use temporary addresses without initiated by the host can use temporary addresses without requiring
requiring application-specific enablement. This document also application-specific enablement. This document also assumes that an
assumes that an API will exist that allows individual applications to API will exist that allows individual applications to indicate
indicate whether they prefer to use temporary or stable addresses and whether they prefer to use temporary or stable addresses and override
override the system defaults (see e.g. [RFC5014]). the system defaults (see, for example, [RFC5014]).
3.3. Generation of Randomized Interface Identifiers 3.3. Generation of Randomized IIDs
The following subsections specify example algorithms for generating The following subsections specify example algorithms for generating
temporary interface identifiers that follow the guidelines in temporary IIDs that follow the guidelines in Section 3.1 of this
Section 3.1 of this document. The algorithm specified in document. The algorithm specified in Section 3.3.1 assumes a
Section 3.3.1 benefits from a Pseudo-Random Number Generator (PRNG) pseudorandom number generator (PRNG) is available on the system. The
available on the system. The algorithm specified in Section 3.3.2 algorithm specified in Section 3.3.2 allows for code reuse by hosts
allows for code reuse by hosts that implement [RFC7217]. that implement [RFC7217].
3.3.1. Simple Randomized Interface Identifiers 3.3.1. Simple Randomized IIDs
One approach is to select a pseudorandom number of the appropriate One approach is to select a pseudorandom number of the appropriate
length. A host employing this algorithm should generate IIDs as length. A host employing this algorithm should generate IIDs as
follows: follows:
1. Obtain a random number from a pseudo-random number generator 1. Obtain a random number from a PRNG that can produce random
(PRNG) that can produce random numbers of at least as many bits numbers of at least as many bits as required for the IID (please
as required for the Interface Identifier (please see the next see the next step). [RFC4086] specifies randomness requirements
step). [RFC4086] specifies randomness requirements for security. for security.
2. The Interface Identifier is obtained by taking as many bits from 2. The IID is obtained by taking as many bits from the random number
the random number obtained in the previous step as necessary. obtained in the previous step as necessary. See [RFC7136] for
See [RFC7136] for the necessary number of bits, that is, the the necessary number of bits (i.e., the length of the IID). See
length of the IID. See also [RFC7421] for a discussion of the also [RFC7421] for a discussion of the privacy implications of
privacy implications of the IID length. Note: there are no the IID length. Note: there are no special bits in an IID
special bits in an Interface Identifier [RFC7136]. [RFC7136].
3. The resulting Interface Identifier MUST be compared against the 3. The resulting IID MUST be compared against the reserved IPv6 IIDs
reserved IPv6 Interface Identifiers [RFC5453] [IANA-RESERVED-IID] [RFC5453] [IANA-RESERVED-IID] and against those IIDs already
and against those Interface Identifiers already employed in an employed in an address of the same network interface and the same
address of the same network interface and the same network network prefix. In the event that an unacceptable identifier has
prefix. In the event that an unacceptable identifier has been been generated, a new IID should be generated by repeating the
generated, a new interface identifier should be generated, by algorithm from the first step.
repeating the algorithm from the first step.
3.3.2. Hash-based Generation of Randomized Interface Identifiers 3.3.2. Generation of IIDs with Pseudorandom Functions
The algorithm in [RFC7217] can be augmented for the generation of The algorithm in [RFC7217] can be augmented for the generation of
temporary addresses. The benefit of this would be that a host could temporary addresses. The benefit of this is that a host could employ
employ a single algorithm for generating stable and temporary a single algorithm for generating stable and temporary addresses by
addresses, by employing appropriate parameters. employing appropriate parameters.
Hosts would employ the following algorithm for generating the Hosts would employ the following algorithm for generating the
temporary IID: temporary IID:
1. Compute a random identifier with the expression: 1. Compute a random identifier with the expression:
RID = F(Prefix, Net_Iface, Network_ID, Time, DAD_Counter, RID = F(Prefix, Net_Iface, Network_ID, Time, DAD_Counter,
secret_key) secret_key)
Where: Where:
skipping to change at page 9, line 34 skipping to change at line 398
RID: RID:
Random Identifier Random Identifier
F(): F():
A pseudorandom function (PRF) that MUST NOT be computable from A pseudorandom function (PRF) that MUST NOT be computable from
the outside (without knowledge of the secret key). F() MUST the outside (without knowledge of the secret key). F() MUST
also be difficult to reverse, such that it resists attempts to also be difficult to reverse, such that it resists attempts to
obtain the secret_key, even when given samples of the output obtain the secret_key, even when given samples of the output
of F() and knowledge or control of the other input parameters. of F() and knowledge or control of the other input parameters.
F() SHOULD produce an output of at least as many bits as F() SHOULD produce an output of at least as many bits as
required for the Interface Identifier. F() could be the required for the IID. BLAKE3 (256-bit key, arbitrary-length
result of applying a cryptographic hash over an encoded output) [BLAKE3] is one possible option for F().
version of the function parameters. While this document does Alternatively, F() could be implemented with a keyed-hash
not recommend a specific mechanism for encoding the function message authentication code (HMAC) [RFC2104]. HMAC-SHA-256
parameters (or a specific cryptographic hash function), a [FIPS-SHS] is one possible option for such an implementation
cryptographically robust construction will ensure that the alternative. Note: use of HMAC-MD5 [RFC1321] is considered
mapping from parameters to the hash function input is an unacceptable for F() [RFC6151].
injective map, as might be attained by using fixed-width
encodings and/or length-prefixing variable-length parameters.
SHA-256 [FIPS-SHS] is one possible option for F(). Note: MD5
[RFC1321] is considered unacceptable for F() [RFC6151].
Prefix: Prefix:
The prefix to be used for SLAAC, as learned from an ICMPv6 The prefix to be used for SLAAC, as learned from an ICMPv6
Router Advertisement message. Router Advertisement message.
Net_Iface: Net_Iface:
The MAC address corresponding to the underlying network-
The MAC address corresponding to the underlying network interface card, in the case the link uses IEEE 802 link-layer
interface card, in the case the link uses IEEE802 link-layer
identifiers. Employing the MAC address for this parameter identifiers. Employing the MAC address for this parameter
(over the other suggested options in RFC7217) means that the (over the other suggested options in [RFC7217]) means that the
re-generation of a randomized MAC address will result in a regeneration of a randomized MAC address will result in a
different temporary address. different temporary address.
Network_ID: Network_ID:
Some network-specific data that identifies the subnet to which Some network-specific data that identifies the subnet to which
this interface is attached -- for example, the IEEE 802.11 this interface is attached -- for example, the IEEE 802.11
Service Set Identifier (SSID) corresponding to the network to Service Set Identifier (SSID) corresponding to the network to
which this interface is associated. Additionally, "Simple which this interface is associated. Additionally, "Simple
Procedures for Detecting Network Attachment in IPv6" ("Simple Procedures for Detecting Network Attachment in IPv6" ("Simple
DNA") [RFC6059] describes ideas that could be leveraged to DNA") [RFC6059] describes ideas that could be leveraged to
generate a Network_ID parameter. This parameter SHOULD be generate a Network_ID parameter. This parameter SHOULD be
employed if some form of "Network_ID" is available. employed if some form of "Network_ID" is available.
Time: Time:
An implementation-dependent representation of time. One An implementation-dependent representation of time. One
possible example is the representation in UNIX-like systems possible example is the representation in UNIX-like systems
[OPEN-GROUP], that measure time in terms of the number of [OPEN-GROUP], which measure time in terms of the number of
seconds elapsed since the Epoch (00:00:00 Coordinated seconds elapsed since the Epoch (00:00:00 Coordinated
Universal Time (UTC), 1 January 1970). The addition of the Universal Time (UTC), 1 January 1970). The addition of the
"Time" argument results in (statistically) different interface "Time" argument results in (statistically) different IIDs over
identifiers over time. time.
DAD_Counter: DAD_Counter:
A counter that is employed to resolve Duplicate Address A counter that is employed to resolve the conflict where an
Detection (DAD) conflicts. unacceptable identifier has been generated. This can be
result of Duplicate Address Detection (DAD), or step 3 below.
secret_key: secret_key:
A secret key that is not known by the attacker. The secret A secret key that is not known by the attacker. The secret
key SHOULD be of at least 128 bits. It MUST be initialized to key SHOULD be of at least 128 bits. It MUST be initialized to
a pseudo-random number (see [RFC4086] for randomness a pseudorandom number (see [RFC4086] for randomness
requirements for security) when the operating system is requirements for security) when the operating system is
"bootstrapped". The secret_key MUST NOT be employed for any "bootstrapped". The secret_key MUST NOT be employed for any
other purpose than the one discussed in this section. For other purpose than the one discussed in this section. For
example, implementations MUST NOT employ the same secret_key example, implementations MUST NOT employ the same secret_key
for the generation of stable addresses [RFC7217] and the for the generation of stable addresses [RFC7217] and the
generation of temporary addresses via this algorithm. generation of temporary addresses via this algorithm.
2. The Interface Identifier is finally obtained by taking as many 2. The IID is finally obtained by taking as many bits from the RID
bits from the RID value (computed in the previous step) as value (computed in the previous step) as necessary, starting from
necessary, starting from the least significant bit. See the least significant bit. See [RFC7136] for the necessary
[RFC7136] for the necessary number of bits, that is, the length number of bits (i.e., the length of the IID). See also [RFC7421]
of the IID. See also [RFC7421] for a discussion of the privacy for a discussion of the privacy implications of the IID length.
implications of the IID length. Note: there are no special bits Note: there are no special bits in an IID [RFC7136].
in an Interface Identifier [RFC7136].
3. The resulting Interface Identifier MUST be compared against the 3. The resulting IID MUST be compared against the reserved IPv6 IIDs
reserved IPv6 Interface Identifiers [RFC5453] [IANA-RESERVED-IID] [RFC5453] [IANA-RESERVED-IID] and against those IIDs already
and against those Interface Identifiers already employed in an employed in an address of the same network interface and the same
address of the same network interface and the same network network prefix. In the event that an unacceptable identifier has
prefix. In the event that an unacceptable identifier has been been generated, the DAD_Counter should be incremented by 1, and
generated, the value DAD_Counter should be incremented by 1, and
the algorithm should be restarted from the first step. the algorithm should be restarted from the first step.
3.4. Generating Temporary Addresses 3.4. Generating Temporary Addresses
[RFC4862] describes the steps for generating a link-local address [RFC4862] describes the steps for generating a link-local address
when an interface becomes enabled as well as the steps for generating when an interface becomes enabled, as well as the steps for
addresses for other scopes. This document extends [RFC4862] as generating addresses for other scopes. This document extends
follows. When processing a Router Advertisement with a Prefix [RFC4862] as follows. When processing a Router Advertisement with a
Information option carrying a prefix for the purposes of address Prefix Information option carrying a prefix for the purposes of
autoconfiguration (i.e., the A bit is set), the host MUST perform the address autoconfiguration (i.e., the A bit is set), the host MUST
following steps: perform the following steps:
1. Process the Prefix Information Option as defined in [RFC4862], 1. Process the Prefix Information option as specified in [RFC4862],
adjusting the lifetimes of existing temporary addresses, with the adjusting the lifetimes of existing temporary addresses, with the
overall constraint that no temporary addresses should ever remain overall constraint that no temporary addresses should ever remain
"valid" or "preferred" for a time longer than "valid" or "preferred" for a time longer than
(TEMP_VALID_LIFETIME) or (TEMP_PREFERRED_LIFETIME - (TEMP_VALID_LIFETIME) or (TEMP_PREFERRED_LIFETIME -
DESYNC_FACTOR) respectively. The configuration variables DESYNC_FACTOR), respectively. The configuration variables
TEMP_VALID_LIFETIME and TEMP_PREFERRED_LIFETIME correspond to TEMP_VALID_LIFETIME and TEMP_PREFERRED_LIFETIME correspond to the
maximum target lifetimes for temporary addresses. maximum valid lifetime and the maximum preferred lifetime of
temporary addresses, respectively.
Note:
DESYNC_FACTOR is the value computed when the address was
created (see step 4 below).
2. One way an implementation can satisfy the above constraints is to 2. One way an implementation can satisfy the above constraints is to
associate with each temporary address a creation time (called associate with each temporary address a creation time (called
CREATION_TIME) that indicates the time at which the address was CREATION_TIME) that indicates the time at which the address was
created. When updating the preferred lifetime of an existing created. When updating the preferred lifetime of an existing
temporary address, it would be set to expire at whichever time is temporary address, it would be set to expire at whichever time is
earlier: the time indicated by the received lifetime or earlier: the time indicated by the received lifetime or
(CREATION_TIME + TEMP_PREFERRED_LIFETIME - DESYNC_FACTOR). A (CREATION_TIME + TEMP_PREFERRED_LIFETIME - DESYNC_FACTOR). A
similar approach can be used with the valid lifetime. similar approach can be used with the valid lifetime.
Note:
DESYNC_FACTOR is the value computed when the address was
created (see step 4 below).
3. If the host has not configured any temporary address for the 3. If the host has not configured any temporary address for the
corresponding prefix, the host SHOULD create a new temporary corresponding prefix, the host SHOULD create a new temporary
address for such prefix. address for such prefix.
Note: Note:
For example, a host might implement prefix-specific policies For example, a host might implement prefix-specific policies
such as not configuring temporary addresses for the Unique such as not configuring temporary addresses for the Unique
Local IPv6 Unicast Addresses (ULA) [RFC4193] prefix. Local IPv6 Unicast Addresses (ULAs) [RFC4193] prefix.
4. When creating a temporary address, the DESYNC_FACTOR MUST be 4. When creating a temporary address, DESYNC_FACTOR MUST be computed
computed for this prefix, and the lifetime values MUST be derived and associated with the newly created address, and the address
from the corresponding prefix as follows: lifetime values MUST be derived from the corresponding prefix as
follows:
* Its Valid Lifetime is the lower of the Valid Lifetime of the * Its valid lifetime is the lower of the Valid Lifetime of the
prefix and TEMP_VALID_LIFETIME. prefix and TEMP_VALID_LIFETIME.
* Its Preferred Lifetime is the lower of the Preferred Lifetime * Its preferred lifetime is the lower of the Preferred Lifetime
of the prefix and TEMP_PREFERRED_LIFETIME - DESYNC_FACTOR. of the prefix and TEMP_PREFERRED_LIFETIME - DESYNC_FACTOR.
5. A temporary address is created only if this calculated Preferred 5. A temporary address is created only if this calculated preferred
Lifetime is greater than REGEN_ADVANCE time units. In lifetime is greater than REGEN_ADVANCE time units. In
particular, an implementation MUST NOT create a temporary address particular, an implementation MUST NOT create a temporary address
with a zero Preferred Lifetime. with a zero preferred lifetime.
6. New temporary addresses MUST be created by appending a randomized 6. New temporary addresses MUST be created by appending a randomized
interface identifier to the prefix that was received. IID to the prefix that was received. Section 3.3 of this
Section 3.3 of this document specifies some sample algorithms for document specifies some sample algorithms for generating the
generating the randomized interface identifier. randomized IID.
7. The host MUST perform duplicate address detection (DAD) on the 7. The host MUST perform DAD on the generated temporary address. If
generated temporary address. If DAD indicates the address is DAD indicates the address is already in use, the host MUST
already in use, the host MUST generate a new randomized interface generate a new randomized IID and repeat the previous steps as
identifier, and repeat the previous steps as appropriate up to appropriate (starting from step 4), up to TEMP_IDGEN_RETRIES
TEMP_IDGEN_RETRIES times. If after TEMP_IDGEN_RETRIES times. If, after TEMP_IDGEN_RETRIES consecutive attempts, the
consecutive attempts no non-unique address was generated, the host is unable to generate a unique temporary address, the host
host MUST log a system error and SHOULD NOT attempt to generate a MUST log a system error and SHOULD NOT attempt to generate a
temporary address for the given prefix for the duration of the temporary address for the given prefix for the duration of the
host's attachment to the network via this interface. This allows host's attachment to the network via this interface. This allows
hosts to recover from occasional DAD failures, or otherwise log hosts to recover from occasional DAD failures or otherwise log
the recurrent address collisions. the recurrent address collisions.
3.5. Expiration of Temporary Addresses 3.5. Expiration of Temporary Addresses
When a temporary address becomes deprecated, a new one MUST be When a temporary address becomes deprecated, a new one MUST be
generated. This is done by repeating the actions described in generated. This is done by repeating the actions described in
Section 3.4, starting at step 4). Note that, except for the Section 3.4, starting at step 4). Note that, in normal operation,
transient period when a temporary address is being regenerated, in except for the transient period when a temporary address is being
normal operation at most one temporary address per prefix should be regenerated, at most one temporary address per prefix should be in a
in a non-deprecated state at any given time on a given interface. nondeprecated state at any given time on a given interface. Note
Note that if a temporary address becomes deprecated as result of that if a temporary address becomes deprecated as result of
processing a Prefix Information Option with a zero Preferred processing a Prefix Information option with a zero preferred
Lifetime, then a new temporary address MUST NOT be generated. To lifetime, then a new temporary address MUST NOT be generated (in
ensure that a preferred temporary address is always available, a new response to the same Prefix Information option). To ensure that a
temporary address SHOULD be regenerated slightly before its preferred temporary address is always available, a new temporary
predecessor is deprecated. This is to allow sufficient time to avoid address SHOULD be regenerated slightly before its predecessor is
race conditions in the case where generating a new temporary address deprecated. This is to allow sufficient time to avoid race
is not instantaneous, such as when duplicate address detection must conditions in the case where generating a new temporary address is
be run. The host SHOULD start the address regeneration process not instantaneous, such as when DAD must be performed. The host
REGEN_ADVANCE time units before a temporary address would actually be SHOULD start the process of address regeneration REGEN_ADVANCE time
deprecated. units before a temporary address is deprecated.
As an optional optimization, an implementation MAY remove a As an optional optimization, an implementation MAY remove a
deprecated temporary address that is not in use by applications or deprecated temporary address that is not in use by applications or
upper layers as detailed in Section 6. upper layers, as detailed in Section 6.
3.6. Regeneration of Temporary Addresses 3.6. Regeneration of Temporary Addresses
The frequency at which temporary addresses change depends on how a The frequency at which temporary addresses change depends on how a
device is being used (e.g., how frequently it initiates new device is being used (e.g., how frequently it initiates new
communication) and the concerns of the end user. The most egregious communication) and the concerns of the end user. The most egregious
privacy concerns appear to involve addresses used for long periods of privacy concerns appear to involve addresses used for long periods of
time (weeks to months to years). The more frequently an address time (from weeks to years). The more frequently an address changes,
changes, the less feasible collecting or coordinating information the less feasible collecting or coordinating information keyed on
keyed on interface identifiers becomes. Moreover, the cost of IIDs becomes. Moreover, the cost of collecting information and
collecting information and attempting to correlate it based on attempting to correlate it based on IIDs will only be justified if
interface identifiers will only be justified if enough addresses enough addresses contain non-changing identifiers to make it
contain non-changing identifiers to make it worthwhile. Thus, having worthwhile. Thus, having large numbers of clients change their
large numbers of clients change their address on a daily or weekly address on a daily or weekly basis is likely to be sufficient to
basis is likely to be sufficient to alleviate most privacy concerns. alleviate most privacy concerns.
There are also client costs associated with having a large number of There are also client costs associated with having a large number of
addresses associated with a host (e.g., in doing address lookups, the addresses associated with a host (e.g., in doing address lookups, the
need to join many multicast groups, etc.). Thus, changing addresses need to join many multicast groups, etc.). Thus, changing addresses
frequently (e.g., every few minutes) may have performance frequently (e.g., every few minutes) may have performance
implications. implications.
Hosts following this specification SHOULD generate new temporary Hosts following this specification SHOULD generate new temporary
addresses on a periodic basis. This can be achieved by generating a addresses over time. This can be achieved by generating a new
new temporary address at least once every (TEMP_PREFERRED_LIFETIME - temporary address REGEN_ADVANCE time units before a temporary address
REGEN_ADVANCE - DESYNC_FACTOR) time units. As described above, becomes deprecated. As described above, this produces addresses with
generating a new temporary address REGEN_ADVANCE time units before a a preferred lifetime no larger than TEMP_PREFERRED_LIFETIME. The
temporary address becomes deprecated produces addresses with a value DESYNC_FACTOR is a random value computed when a temporary
preferred lifetime no larger than TEMP_PREFERRED_LIFETIME. The value address is generated; it ensures that clients do not generate new
DESYNC_FACTOR is a random value computed for a prefix when a addresses at a fixed frequency and that clients do not synchronize
temporary address is generated, that ensures that clients do not with each other and generate new addresses at exactly the same time.
generate new addresses with a fixed frequency, and that clients do When the preferred lifetime expires, a new temporary address MUST be
not synchronize with each other and generate new addresses at exactly generated using the algorithm specified in Section 3.4 (starting at
the same time. When the preferred lifetime expires, a new temporary step 4).
address MUST be generated using the algorithm specified in
Section 3.4.
Because the precise frequency at which it is appropriate to generate Because the frequency at which it is appropriate to generate new
new addresses varies from one environment to another, implementations addresses varies from one environment to another, implementations
SHOULD provide end users with the ability to change the frequency at SHOULD provide end users with the ability to change the frequency at
which addresses are regenerated. The default value is given in which addresses are regenerated. The default value is given in
TEMP_PREFERRED_LIFETIME and is one day. In addition, the exact time TEMP_PREFERRED_LIFETIME and is one day. In addition, the exact time
at which to invalidate a temporary address depends on how at which to invalidate a temporary address depends on how
applications are used by end users. Thus, the suggested default applications are used by end users. Thus, the suggested default
value of two days (TEMP_VALID_LIFETIME) may not be appropriate in all value of two days (TEMP_VALID_LIFETIME) may not be appropriate in all
environments. Implementations SHOULD provide end users with the environments. Implementations SHOULD provide end users with the
ability to override both of these default values. ability to override both of these default values.
Finally, when an interface connects to a new (different) link, Finally, when an interface connects to a new (different) link,
existing temporary addresses for the corresponding interface MUST be existing temporary addresses for the corresponding interface MUST be
eliminated, and new temporary addresses MUST be generated immediately removed, and new temporary addresses MUST be generated for use on the
for use on the new link. If a device moves from one link to another, new link, using the algorithm in Section 3.4. If a device moves from
generating new temporary addresses ensures that the device uses one link to another, generating new temporary addresses ensures that
different randomized interface identifiers for the temporary the device uses different randomized IIDs for the temporary addresses
addresses associated with the two links, making it more difficult to associated with the two links, making it more difficult to correlate
correlate addresses from the two different links as being from the addresses from the two different links as being from the same host.
same hosts. The host MAY follow any process available to it, to The host MAY follow any process available to it to determine that the
determine that the link change has occurred. One such process is link change has occurred. One such process is described by "Simple
described by Simple DNA [RFC6059]. Detecting link changes would DNA" [RFC6059]. Detecting link changes would prevent link down/up
prevent link down/up events from causing temporary addresses to be events from causing temporary addresses to be (unnecessarily)
(unnecessarily) regenerated. regenerated.
3.7. Implementation Considerations 3.7. Implementation Considerations
Devices implementing this specification MUST provide a way for the Devices implementing this specification MUST provide a way for the
end user to explicitly enable or disable the use of temporary end user to explicitly enable or disable the use of temporary
addresses. In addition, a site might wish to disable the use of addresses. In addition, a site might wish to disable the use of
temporary addresses in order to simplify network debugging and temporary addresses in order to simplify network debugging and
operations. Consequently, implementations SHOULD provide a way for operations. Consequently, implementations SHOULD provide a way for
trusted system administrators to enable or disable the use of trusted system administrators to enable or disable the use of
temporary addresses. temporary addresses.
Additionally, sites might wish to selectively enable or disable the Additionally, sites might wish to selectively enable or disable the
use of temporary addresses for some prefixes. For example, a site use of temporary addresses for some prefixes. For example, a site
might wish to disable temporary address generation for "Unique local" might wish to disable temporary-address generation for ULA [RFC4193]
[RFC4193] prefixes while still generating temporary addresses for all prefixes while still generating temporary addresses for all other
other global prefixes. Another site might wish to enable temporary prefixes advertised via PIOs for address configuration. Another site
address generation only for the prefixes 2001:db8:1::/48 and might wish to enable temporary-address generation only for the
2001:db8:2::/48 while disabling it for all other prefixes. To prefixes 2001:db8:1::/48 and 2001:db8:2::/48 while disabling it for
support this behavior, implementations SHOULD provide a way to enable all other prefixes. To support this behavior, implementations SHOULD
and disable generation of temporary addresses for specific prefix provide a way to enable and disable generation of temporary addresses
subranges. This per-prefix setting SHOULD override the global for specific prefix subranges. This per-prefix setting SHOULD
settings on the host with respect to the specified prefix subranges. override the global settings on the host with respect to the
Note that the per-prefix setting can be applied at any granularity, specified prefix subranges. Note that the per-prefix setting can be
and not necessarily on a per subnet basis. applied at any granularity, and not necessarily on a per-subnet
basis.
3.8. Defined Constants and Configuration Variables
Constants and configuration variables defined in this document
include:
TEMP_VALID_LIFETIME -- Default value: 2 days. Users should be able 3.8. Defined Protocol Parameters and Configuration Variables
to override the default value.
TEMP_PREFERRED_LIFETIME -- Default value: 1 day. Users should be Protocol parameters and configuration variables defined in this
able to override the default value. document include:
Note: TEMP_VALID_LIFETIME
The TEMP_PREFERRED_LIFETIME value MUST be less than the Default value: 2 days. Users should be able to override the
TEMP_VALID_LIFETIME value, to avoid the pathological case where an default value.
address is employed for new communications, but becomes invalid in
less than 1 second, disrupting those communications
REGEN_ADVANCE -- 2 + (TEMP_IDGEN_RETRIES * DupAddrDetectTransmits * TEMP_PREFERRED_LIFETIME
RetransTimer / 1000) Default value: 1 day. Users should be able to override the
default value. Note: The TEMP_PREFERRED_LIFETIME value MUST be
smaller than the TEMP_VALID_LIFETIME value, to avoid the
pathological case where an address is employed for new
communications but becomes invalid in less than 1 second,
disrupting those communications.
Notes: REGEN_ADVANCE
This parameter is specified as a function of other protocol 2 + (TEMP_IDGEN_RETRIES * DupAddrDetectTransmits * RetransTimer /
parameters, to account for the time possibly spent in Duplicate 1000)
Address Detection (DAD) in the worst-case scenario of
TEMP_IDGEN_RETRIES. This prevents the pathological case where the
generation of a new temporary address is not started with enough
anticipation such that a new preferred address is generated before
the currently-preferred temporary address becomes deprecated.
RetransTimer is specified in [RFC4861], while | Rationale: This parameter is specified as a function of other
DupAddrDetectTransmits is specified in [RFC4862]. Since | protocol parameters, to account for the time possibly spent in
RetransTimer is specified in units of milliseconds, this | DAD in the worst-case scenario of TEMP_IDGEN_RETRIES. This
expression employs the constant "1000" such that REGEN_ADVANCE is | prevents the pathological case where the generation of a new
expressed in seconds. | temporary address is not started with enough anticipation, such
| that a new preferred address is generated before the currently
| preferred temporary address becomes deprecated.
|
| RetransTimer is specified in [RFC4861], while
| DupAddrDetectTransmits is specified in [RFC4862]. Since
| RetransTimer is specified in units of milliseconds, this
| expression employs the constant "1000", such that REGEN_ADVANCE
| is expressed in seconds.
MAX_DESYNC_FACTOR -- 0.4 * TEMP_PREFERRED_LIFETIME. Upper bound on MAX_DESYNC_FACTOR
DESYNC_FACTOR. 0.4 * TEMP_PREFERRED_LIFETIME. Upper bound on DESYNC_FACTOR.
Note: | Rationale: Setting MAX_DESYNC_FACTOR to 0.4
Setting MAX_DESYNC_FACTOR to 0.4 TEMP_PREFERRED_LIFETIME results | TEMP_PREFERRED_LIFETIME results in addresses that have
in addresses that have statistically different lifetimes, and a | statistically different lifetimes, and a maximum of three
maximum of 3 concurrent temporary addresses when the default | concurrent temporary addresses when the default values
parameters specified in this section are employed. | specified in this section are employed.
DESYNC_FACTOR -- A random value within the range 0 - DESYNC_FACTOR
MAX_DESYNC_FACTOR. It is computed for a prefix each time a temporary A random value within the range 0 - MAX_DESYNC_FACTOR. It is
address is generated, and must be smaller than computed each time a temporary address is generated, and is
(TEMP_PREFERRED_LIFETIME - REGEN_ADVANCE). associated with the corresponding address. It MUST be smaller
than (TEMP_PREFERRED_LIFETIME - REGEN_ADVANCE).
TEMP_IDGEN_RETRIES -- Default value: 3 TEMP_IDGEN_RETRIES
Default value: 3
4. Implications of Changing Interface Identifiers 4. Implications of Changing IIDs
The desire to protect individual privacy can conflict with the desire The desire to protect individual privacy can conflict with the desire
% to effectively maintain and debug a network. Having clients use to effectively maintain and debug a network. Having clients use
addresses that change over time will make it more difficult to track addresses that change over time will make it more difficult to track
down and isolate operational problems. For example, when looking at down and isolate operational problems. For example, when looking at
packet traces, it could become more difficult to determine whether packet traces, it could become more difficult to determine whether
one is seeing behavior caused by a single errant host, or by a number one is seeing behavior caused by a single errant host or a number of
of them. them.
Network deployments are currently recommended to provide multiple It is currently recommended that network deployments provide multiple
IPv6 addresses from each prefix to general-purpose hosts [RFC7934]. IPv6 addresses from each prefix to general-purpose hosts [RFC7934].
However, in some scenarios, use of a large number of IPv6 addresses However, in some scenarios, use of a large number of IPv6 addresses
may have negative implications on network devices that need to may have negative implications on network devices that need to
maintain entries for each IPv6 address in some data structures (e.g., maintain entries for each IPv6 address in some data structures (e.g.,
[RFC7039]). For example, concurrent active use of multiple IPv6 SAVI [RFC7039]). For example, concurrent active use of multiple IPv6
addresses will increase neighbor discovery traffic if Neighbor Caches addresses will increase Neighbor Discovery traffic if Neighbor Caches
in network devices are not large enough to store all addresses on the in network devices are not large enough to store all addresses on the
link. This can impact performance and energy efficiency on networks link. This can impact performance and energy efficiency on networks
on which multicast is expensive (e.g. on which multicast is expensive (see e.g., [MCAST-PROBLEMS]).
[I-D.ietf-mboned-ieee802-mcast-problems]). Additionally, some Additionally, some network-security devices might incorrectly infer
network security devices might incorrectly infer IPv6 address forging IPv6 address forging if temporary addresses are regenerated at a high
if temporary addresses are regenerated at a high rate. rate.
The use of temporary addresses may cause unexpected difficulties with The use of temporary addresses may cause unexpected difficulties with
some applications. For example, some servers refuse to accept some applications. For example, some servers refuse to accept
communications from clients for which they cannot map the IP address communications from clients for which they cannot map the IP address
into a DNS name. That is, they perform a DNS PTR query to determine into a DNS name. That is, they perform a DNS PTR query to determine
the DNS name, and may then also perform an AAAA query on the returned the DNS name corresponding to an IPv6 address, and may then also
name to verify that the returned DNS name maps back into the address perform a AAAA query on the returned name to verify it maps back into
being used. Consequently, clients not properly registered in the DNS the same address. Consequently, clients not properly registered in
may be unable to access some services. However, a host's DNS name the DNS may be unable to access some services. However, a host's DNS
(if non-changing) would serve as a constant identifier. The wide name (if non-changing) would serve as a constant identifier. The
deployment of the extension described in this document could wide deployment of the extension described in this document could
challenge the practice of inverse-DNS-based "validation", which has challenge the practice of inverse-DNS-based "validation", which has
little validity, though it is widely implemented. In order to meet little validity, though it is widely implemented. In order to meet
server challenges, hosts could register temporary addresses in the server challenges, hosts could register temporary addresses in the
DNS using random names (for example, a string version of the random DNS using random names (for example, a string version of the random
address itself), albeit at the expense of increased complexity. address itself), albeit at the expense of increased complexity.
In addition, some applications may not behave robustly if temporary In addition, some applications may not behave robustly if an address
addresses are used and an address expires before the application has becomes invalid while it is still in use by the application or if the
terminated, or if it opens multiple sessions, but expects them to all application opens multiple sessions and expects them to all use the
use the same addresses. same address.
[RFC4941] employed a randomized temporary Interface Identifier for [RFC4941] employed a randomized temporary IID for generating a set of
generating a set of temporary addresses, such that temporary temporary addresses, such that temporary addresses configured at a
addresses configured at a given time for multiple SLAAC prefixes given time for multiple SLAAC prefixes would employ the same IID.
would employ the same Interface Identifier. Sharing the same IID Sharing the same IID among multiple addresses allowed a host to join
among multiple address allowed host to join only one solicited-node only one solicited-node multicast group per temporary address set.
multicast group per temporary address set.
This document requires that the Interface Identifiers of all This document requires that the IIDs of all temporary addresses on a
temporary addresses on a host are statistically different from each host are statistically different from each other. This means that
other. This means that when a network employs multiple prefixes, when a network employs multiple prefixes, each temporary address of a
each temporary address of a set will result in a different solicited- set will result in a different solicited-node multicast address, and,
node multicast address, and thus the number of multicast groups that thus, the number of multicast groups that a host must join becomes a
a host must join becomes a function of the number of SLAAC prefixes function of the number of SLAAC prefixes employed for generating
employed for generating temporary addresses. temporary addresses.
Thus, a network that employs multiple prefixes may require hosts to Thus, a network that employs multiple prefixes may require hosts to
join more multicast groups than for an RFC4941 implementation. If join more multicast groups than in the case of implementations of RFC
the number of multicast groups were large enough, a node might need 4941. If the number of multicast groups were large enough, a host
to resort to setting the network interface card to promiscuous mode. might need to resort to setting the network interface card to
This could cause the node to process more packets than strictly promiscuous mode. This could cause the host to process more packets
necessary, and might have a negative impact on battery-life, and on than strictly necessary and might have a negative impact on battery
system performance in general. life and system performance in general.
We note that since this document reduces the default We note that since this document reduces the default
TEMP_VALID_LIFETIME from 7 days (in [RFC4941]) to 2 days, the number TEMP_VALID_LIFETIME from 7 days (in [RFC4941]) to 2 days, the number
of concurrent temporary addresses per SLAAC prefix will be smaller of concurrent temporary addresses per SLAAC prefix will be smaller
than for RFC4941 implementations, and thus the number of multicast than for RFC 4941 implementations; thus, the number of multicast
groups for a network that employs, say, between 1 and three prefixes groups for a network that employs, say, between 1 and 3 prefixes,
will be similar than of RFC4941 implementations. will be similar to the number of such groups for RFC 4941
implementations.
Implementations concerned with the maximum number of multicast groups Implementations concerned with the maximum number of multicast groups
that would be required to join as a result of configured addresses, that would be required to join as a result of configured addresses,
or the overall number of configured addresses, should consider or the overall number of configured addresses, should consider
enforcing implementation-specific limits on e.g. the maximum number enforcing implementation-specific limits on, e.g., the maximum number
of configured addresses, the maximum number of SLAAC prefixes that of configured addresses, the maximum number of SLAAC prefixes that
are employed for auto-configuration, and/or the maximum ratio for are employed for autoconfiguration, and/or the maximum ratio for
TEMP_VALID_LIFETIME/TEMP_PREFERRED_LIFETIME (that ultimately controls TEMP_VALID_LIFETIME/TEMP_PREFERRED_LIFETIME (which ultimately
the approximate number of concurrent temporary addresses per SLAAC controls the approximate number of concurrent temporary addresses per
prefix). Many of these configuration limits are readily available in SLAAC prefix). Many of these configuration limits are readily
SLAAC and RFC4941 implementations. We note that these configurable available in SLAAC and RFC 4941 implementations. We note that these
limits are meant to prevent pathological behaviors (as opposed to configurable limits are meant to prevent pathological behaviors (as
simply limiting the usage of IPv6 addresses), since IPv6 opposed to simply limiting the usage of IPv6 addresses), since IPv6
implementations are expected to leverage the usage of multiple implementations are expected to leverage the usage of multiple
addresses [RFC7934]. addresses [RFC7934].
5. Significant Changes from RFC4941 5. Significant Changes from RFC 4941
This section summarizes the substantive changes in this document This section summarizes the substantive changes in this document
relative to RFC 4941. relative to RFC 4941.
Broadly speaking, this document introduces the following changes: Broadly speaking, this document introduces the following changes:
o Addresses a number of flaws in the algorithm for generating * Addresses a number of flaws in the algorithm for generating
temporary addresses: The aforementioned flaws include the use of temporary addresses. The aforementioned flaws include the use of
MD5 for computing the temporary IIDs, and reusing the same IID for MD5 for computing the temporary IIDs, and reusing the same IID for
multiple prefixes (see [RAID2015] and [RFC7721] for further multiple prefixes (see [RAID2015] and [RFC7721] for further
details). details).
o Allows hosts to employ only temporary addresses: * Allows hosts to employ only temporary addresses. [RFC4941]
[RFC4941] assumed that temporary addresses were configured in assumed that temporary addresses were configured in addition to
addition to stable addresses. This document does not imply or stable addresses. This document does not imply or require the
require the configuration of stable addresses, and thus configuration of stable addresses; thus, implementations can now
implementations can now configure both stable and temporary configure both stable and temporary addresses or temporary
addresses, or temporary addresses only. addresses only.
o Removes the recommendation that temporary addresses be disabled by * Removes the recommendation that temporary addresses be disabled by
default: default. This is in line with BCP 188 ([RFC7258]) and also with
This is in line with BCP188 ([RFC7258]), and also with BCP204 BCP 204 ([RFC7934]).
([RFC7934]).
o Reduces the default maximum Valid Lifetime for temporary * Reduces the default maximum valid lifetime for temporary addresses
addresses: The default Valid Lifetime for temporary addresses has (TEMP_VALID_LIFETIME). TEMP_VALID_LIFETIME has been reduced from
been reduced from 1 week to 2 days, decreasing the typical number 1 week to 2 days, decreasing the typical number of concurrent
of concurrent temporary addresses from 7 to 3. This reduces the temporary addresses from 7 to 3. This reduces the possible stress
possible stress on network elements (see Section 4 for further on network elements (see Section 4 for further details).
details).
o DESYNC_FACTOR is computed on a per-prefix basis each time a * DESYNC_FACTOR is computed each time a temporary address is
temporary address is generated, such that each temporary address generated and is associated with the corresponding temporary
has a statistically different preferred lifetime, and that address, such that each temporary address has a statistically
temporary addresses are not generated at a constant frequency. different preferred lifetime, and thus temporary addresses are not
generated at any specific frequency.
o Changes the requirement to not try to regenerate temporary * Changes the requirement to not try to regenerate temporary
addresses upon DAD failures from "MUST NOT" to "SHOULD NOT". addresses upon TEMP_IDGEN_RETRIES consecutive DAD failures from
"MUST NOT" to "SHOULD NOT".
o The discussion about the security and privacy implications of * The discussion about the security and privacy implications of
different address generation techniques has been replaced with different address generation techniques has been replaced with
references to recent work in this area ([RFC7707], [RFC7721], and references to recent work in this area ([RFC7707], [RFC7721], and
[RFC7217]). [RFC7217]).
o Addresses all errata submitted for [RFC4941]. * This document incorporates errata submitted (at the time of
writing) for [RFC4941] by Jiri Bohac and Alfred Hoenes.
6. Future Work 6. Future Work
An implementation might want to keep track of which addresses are An implementation might want to keep track of which addresses are
being used by upper layers so as to be able to remove a deprecated being used by upper layers so as to be able to remove a deprecated
temporary address from internal data structures once no upper layer temporary address from internal data structures once no upper-layer
protocols are using it (but not before). This is in contrast to protocols are using it (but not before). This is in contrast to
current approaches where addresses are removed from an interface when current approaches, where addresses are removed from an interface
they become invalid [RFC4862], independent of whether or not upper when they become invalid [RFC4862], independent of whether or not
layer protocols are still using them. For TCP connections, such upper-layer protocols are still using them. For TCP connections,
information is available in control blocks. For UDP-based such information is available in control blocks. For UDP-based
applications, it may be the case that only the applications have applications, it may be the case that only the applications have
knowledge about what addresses are actually in use. Consequently, an knowledge about what addresses are actually in use. Consequently, an
implementation generally will need to use heuristics in deciding when implementation generally will need to use heuristics in deciding when
an address is no longer in use. an address is no longer in use.
7. Implementation Status 7. IANA Considerations
[The RFC-Editor should remove this section before publishing this
document as an RFC]
The following are known implementations of this document:
o FreeBSD kernel: There is a FreeBSD kernel implementation of this
document, albeit not yet committed. The implementation has been
done in April 2020 by Fernando Gont <fgont@si6networks.com>. The
corresponding patch can be found at:
<https://www.gont.com.ar/code/fgont-patch-freebsd-rfc4941bis.txt>
o Linux kernel: A Linux kernel implementation of this document has
been committed to the net-next tree. The implementation has been
produced in April 2020 by Fernando Gont <fgont@si6networks.com>.
The corresponding patch can be found at:
<https://patchwork.ozlabs.org/project/netdev/
patch/20200501035147.GA1587@archlinux-current.localdomain/>
o slaacd(8): slaacd(8) has traditionally used different randomized
interface identifiers for each prefix, and it has recently reduced
the Valid Lifetime of temporary addresses as specified in
Section 3.8, thus fully implementing this document. The
implementation has been done by Florian Obser
<florian@openbsd.org>, with the update to the temporary address
Valid Lifetime applied in March 2020. The implementation can be
found at: <https://github.com/openbsd/src/tree/master/sbin/slaacd>
8. IANA Considerations
There are no IANA registries within this document. The RFC-Editor This document has no IANA actions.
can remove this section before publication of this document as an
RFC.
9. Security Considerations 8. Security Considerations
If a very small number of hosts (say, only one) use a given prefix If a very small number of hosts (say, only one) use a given prefix
for extended periods of time, just changing the interface identifier for extended periods of time, just changing the interface-identifier
part of the address may not be sufficient to mitigate address-based part of the address may not be sufficient to mitigate address-based
network activity correlation, since the prefix acts as a constant network-activity correlation, since the prefix acts as a constant
identifier. The procedures described in this document are most identifier. The procedures described in this document are most
effective when the prefix is reasonably non static or is used by a effective when the prefix is reasonably nonstatic or used by a fairly
fairly large number of hosts. Additionally, if a temporary address large number of hosts. Additionally, if a temporary address is used
is used in a session where the user authenticates, any notion of in a session where the user authenticates, any notion of "privacy"
"privacy" for that address is compromised for the part(ies) that for that address is compromised for the party or parties that receive
receive the authentication information. the authentication information.
While this document discusses ways to limit the lifetime of Interface While this document discusses ways to limit the lifetime of interface
Identifiers to reduce the ability of attackers to perform address- identifiers to reduce the ability of attackers to perform address-
based network activity correlation, the method described is believed based network-activity correlation, the method described is believed
to be ineffective against sophisticated forms of traffic analysis. to be ineffective against sophisticated forms of traffic analysis.
To increase effectiveness, one may need to consider the use of more To increase effectiveness, one may need to consider the use of more
advanced techniques, such as Onion Routing [ONION]. advanced techniques, such as onion routing [ONION].
Ingress filtering has been and is being deployed as a means of Ingress filtering has been and is being deployed as a means of
preventing the use of spoofed source addresses in Distributed Denial preventing the use of spoofed source addresses in Distributed Denial
of Service (DDoS) attacks. In a network with a large number of of Service (DDoS) attacks. In a network with a large number of
hosts, new temporary addresses are created at a fairly high rate. hosts, new temporary addresses are created at a fairly high rate.
This might make it difficult for ingress filtering mechanisms to This might make it difficult for ingress-/egress-filtering mechanisms
distinguish between legitimately changing temporary addresses and to distinguish between legitimately changing temporary addresses and
spoofed source addresses, which are "in-prefix" (using a spoofed source addresses, which are "in-prefix" (using a
topologically correct prefix and non-existent interface ID). This topologically correct prefix and nonexistent interface identifier).
can be addressed by using access control mechanisms on a per-address This can be addressed by using access-control mechanisms on a per-
basis on the network egress point, though as noted in Section 4 there address basis on the network ingress point -- though, as noted in
are corresponding costs for doing so. Section 4, there are corresponding costs for doing so.
10. Acknowledgments
The authors would like to thank (in alphabetical order) Fred Baker,
Brian Carpenter, Tim Chown, Lorenzo Colitti, Roman Danyliw, David
Farmer, Tom Herbert, Bob Hinden, Christian Huitema, Benjamin Kaduk,
Erik Kline, Gyan Mishra, Dave Plonka, Alvaro Retana, Michael
Richardson, Mark Smith, Dave Thaler, Pascal Thubert, Ole Troan,
Johanna Ullrich, Eric Vyncke, and Timothy Winters, for providing
valuable comments on earlier versions of this document.
This document incorporates errata submitted for [RFC4941] by Jiri
Bohac and Alfred Hoenes.
This document is based on [RFC4941] (a revision of RFC3041). Suresh
Krishnan was the sole author of RFC4941. He would like to
acknowledge the contributions of the IPv6 working group and, in
particular, Jari Arkko, Pekka Nikander, Pekka Savola, Francis Dupont,
Brian Haberman, Tatuya Jinmei, and Margaret Wasserman for their
detailed comments.
Rich Draves and Thomas Narten were the authors of RFC 3041. They
would like to acknowledge the contributions of the IPv6 working group
and, in particular, Ran Atkinson, Matt Crawford, Steve Deering,
Allison Mankin, and Peter Bieringer.
11. References 9. References
11.1. Normative References 9.1. 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,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086, "Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005, DOI 10.17487/RFC4086, June 2005,
<https://www.rfc-editor.org/info/rfc4086>. <https://www.rfc-editor.org/info/rfc4086>.
skipping to change at page 22, line 5 skipping to change at line 945
<https://www.rfc-editor.org/info/rfc6724>. <https://www.rfc-editor.org/info/rfc6724>.
[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, <https://www.rfc-editor.org/info/rfc7136>. February 2014, <https://www.rfc-editor.org/info/rfc7136>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
11.2. Informative References 9.2. Informative References
[FIPS-SHS] [BLAKE3] O'Connor, J., Aumasson, J. P., Neves, S., and Z. Wilcox-
NIST, "Secure Hash Standard (SHS)", FIPS O'Hearn, "BLAKE3: one function, fast everywhere", 2020,
Publication 180-4, August 2015, <https://blake3.io/>.
[FIPS-SHS] NIST, "Secure Hash Standard (SHS)", FIPS PUB 180-4,
DOI 10.6028/NIST.FIPS.180-4, August 2015,
<https://nvlpubs.nist.gov/nistpubs/FIPS/ <https://nvlpubs.nist.gov/nistpubs/FIPS/
NIST.FIPS.180-4.pdf>. NIST.FIPS.180-4.pdf>.
[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-12 (work
in progress), October 2020.
[IANA-RESERVED-IID] [IANA-RESERVED-IID]
IANA, "Reserved IPv6 Interface Identifiers", IANA, "Reserved IPv6 Interface Identifiers",
<http://www.iana.org/assignments/ipv6-interface-ids>. <https://www.iana.org/assignments/ipv6-interface-ids>.
[ONION] Reed, MGR., Syverson, PFS., and DMG. Goldschlag, "Proxies [MCAST-PROBLEMS]
for Anonymous Routing", Proceedings of the 12th Annual Perkins, C. E., McBride, M., Stanley, D., Kumari, W., and
Computer Security Applications Conference, San Diego, CA, J. C. Zuniga, "Multicast Considerations over IEEE 802
December 1996. Wireless Media", Work in Progress, Internet-Draft, draft-
ietf-mboned-ieee802-mcast-problems-13, 4 February 2021,
<https://tools.ietf.org/html/draft-ietf-mboned-ieee802-
mcast-problems-13>.
[ONION] Reed, M.G., Syverson, P.F., and D.M. Goldschlag, "Proxies
for Anonymous Routing", Proceedings of the 12th Annual
Computer Security Applications Conference,
DOI 10.1109/CSAC.1996.569678, December 1996,
<https://doi.org/10.1109/CSAC.1996.569678>.
[OPEN-GROUP] [OPEN-GROUP]
The Open Group, "The Open Group Base Specifications Issue The Open Group, "The Open Group Base Specifications Issue
7 / IEEE Std 1003.1-2008, 2016 Edition", 7", Section 4.16 Seconds Since the Epoch, IEEE Std 1003.1,
Section 4.16 Seconds Since the Epoch, 2016, 2016,
<http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/ <http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/
contents.html>. contents.html>.
[RAID2015] [RAID2015] Ullrich, J. and E.R. Weippl, "Privacy is Not an Option:
Ullrich, J. and E. Weippl, "Privacy is Not an Option:
Attacking the IPv6 Privacy Extension", International Attacking the IPv6 Privacy Extension", International
Symposium on Recent Advances in Intrusion Detection Symposium on Recent Advances in Intrusion Detection
(RAID), 2015, <https://www.sba-research.org/wp- (RAID), 2015, <https://publications.sba-
content/uploads/publications/Ullrich2015Privacy.pdf>. research.org/publications/Ullrich2015Privacy.pdf>.
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
DOI 10.17487/RFC1321, April 1992, DOI 10.17487/RFC1321, April 1992,
<https://www.rfc-editor.org/info/rfc1321>. <https://www.rfc-editor.org/info/rfc1321>.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
DOI 10.17487/RFC2104, February 1997,
<https://www.rfc-editor.org/info/rfc2104>.
[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Stateless Address Autoconfiguration in Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007, IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,
<https://www.rfc-editor.org/info/rfc4941>. <https://www.rfc-editor.org/info/rfc4941>.
[RFC5014] Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6 [RFC5014] Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6
Socket API for Source Address Selection", RFC 5014, Socket API for Source Address Selection", RFC 5014,
DOI 10.17487/RFC5014, September 2007, DOI 10.17487/RFC5014, September 2007,
<https://www.rfc-editor.org/info/rfc5014>. <https://www.rfc-editor.org/info/rfc5014>.
skipping to change at page 24, line 15 skipping to change at line 1060
[RFC7934] Colitti, L., Cerf, V., Cheshire, S., and D. Schinazi, [RFC7934] Colitti, L., Cerf, V., Cheshire, S., and D. Schinazi,
"Host Address Availability Recommendations", BCP 204, "Host Address Availability Recommendations", BCP 204,
RFC 7934, DOI 10.17487/RFC7934, July 2016, RFC 7934, DOI 10.17487/RFC7934, July 2016,
<https://www.rfc-editor.org/info/rfc7934>. <https://www.rfc-editor.org/info/rfc7934>.
[RFC8190] Bonica, R., Cotton, M., Haberman, B., and L. Vegoda, [RFC8190] Bonica, R., Cotton, M., Haberman, B., and L. Vegoda,
"Updates to the Special-Purpose IP Address Registries", "Updates to the Special-Purpose IP Address Registries",
BCP 153, RFC 8190, DOI 10.17487/RFC8190, June 2017, BCP 153, RFC 8190, DOI 10.17487/RFC8190, June 2017,
<https://www.rfc-editor.org/info/rfc8190>. <https://www.rfc-editor.org/info/rfc8190>.
Acknowledgments
Fernando Gont was the sole author of this document (a revision of RFC
4941). He would like to thank (in alphabetical order) Fred Baker,
Brian Carpenter, Tim Chown, Lorenzo Colitti, Roman Danyliw, David
Farmer, Tom Herbert, Bob Hinden, Christian Huitema, Benjamin Kaduk,
Erik Kline, Gyan Mishra, Dave Plonka, Alvaro Retana, Michael
Richardson, Mark Smith, Dave Thaler, Pascal Thubert, Ole Troan,
Johanna Ullrich, Eric Vyncke, Timothy Winters, and Christopher Wood
for providing valuable comments on earlier draft versions of this
document.
This document incorporates errata submitted for RFC 4941 by Jiri
Bohac and Alfred Hoenes (at the time of writing).
Suresh Krishnan was the sole author of RFC 4941 (a revision of RFC
3041). He would like to acknowledge the contributions of the IPv6
Working Group and, in particular, Jari Arkko, Pekka Nikander, Pekka
Savola, Francis Dupont, Brian Haberman, Tatuya Jinmei, and Margaret
Wasserman for their detailed comments.
Rich Draves and Thomas Narten were the authors of RFC 3041. They
would like to acknowledge the contributions of the IPv6 Working Group
and, in particular, Ran Atkinson, Matt Crawford, Steve Deering,
Allison Mankin, and Peter Bieringer.
Authors' Addresses Authors' Addresses
Fernando Gont Fernando Gont
SI6 Networks SI6 Networks
Evaristo Carriego 2644 Segurola y Habana 4310, 7mo Piso
Haedo, Provincia de Buenos Aires 1706 Villa Devoto
Ciudad Autonoma de Buenos Aires
Argentina Argentina
Phone: +54 11 4650 8472
Email: fgont@si6networks.com Email: fgont@si6networks.com
URI: https://www.si6networks.com URI: https://www.si6networks.com
Suresh Krishnan Suresh Krishnan
Kaloom Kaloom
Email: suresh@kaloom.com Email: suresh@kaloom.com
Thomas Narten Thomas Narten
Email: narten@cs.duke.edu Email: narten@cs.duke.edu
Richard Draves Richard Draves
Microsoft Research Microsoft Research
One Microsoft Way One Microsoft Way
Redmond, WA Redmond, WA
USA United States of America
Email: richdr@microsoft.com Email: richdr@microsoft.com
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