Independent Submission D. Binet
Request for Comments: 7849 M. Boucadair
Category: Informational Orange
ISSN: 2070-1721 A. Vizdal
Deutsche Telekom AG
eircom | meteor
May 2016 An IPv6 Profile for 3GPP Mobile Devices
This document defines a profile that is a superset of the connection
to IPv6 cellular networks defined in the IPv6 for Third Generation
Partnership Project (3GPP) Cellular Hosts document. This document
defines a profile that is a superset of the connections to IPv6
cellular networks defined in "IPv6 for Third Generation Partnership
Project (3GPP) Cellular Hosts" (RFC 7066).
Both mobile hosts and mobile devices with the capability to share
their 3GPP mobile connectivity are in scope.
The consensus-based IETF description of IPv6 functionality for
cellular hosts is described in RFC 7066.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This is a contribution to the RFC Series, independently of any other
RFC stream. The RFC Editor has chosen to publish this document at
its discretion and makes no statement about its value for
implementation or deployment. Documents approved for publication by
the RFC Editor are not a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 31.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 41.2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 52. Connectivity Recommendations . . . . . . . . . . . . . . . . 63. Recommendations for Cellular Devices with LAN Capabilities . 114. Advanced Recommendations . . . . . . . . . . . . . . . . . . 135. Security Considerations . . . . . . . . . . . . . . . . . . . 156. References . . . . . . . . . . . . . . . . . . . . . . . . . 166.1. Normative References . . . . . . . . . . . . . . . . . . 166.2. Informative References . . . . . . . . . . . . . . . . . 17
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
IPv6 deployment in 3GPP mobile networks is the only viable solution
to the exhaustion of IPv4 addresses in those networks. Several
mobile operators have already deployed IPv6 [RFC2460] or are in the
pre-deployment phase. One of the major hurdles as perceived by some
mobile operators is the lack of availability of working IPv6
implementation in mobile devices (e.g., Section 3.3 of [OECD]).
[RFC7066] lists a set of features to be supported by cellular hosts
to connect to 3GPP mobile networks. In the light of recent IPv6
production deployments, additional features to facilitate IPv6-only
deployments while accessing IPv4-only services should be considered.
This document fills this void. Concretely, this document lists means
to ensure IPv4 service over an IPv6-only connectivity given the
adoption rate of this model by mobile operators. Those operators
require that no service degradation is experienced by customers
serviced with an IPv6-only model compared to the level of service of
customers with legacy IPv4-only devices.
This document defines an IPv6 profile for mobile devices listing
specifications produced by various Standards Developing Organizations
(including 3GPP, IETF, and the Global System for Mobile
Communications Association (GSMA)). The objectives of this effort
are as follows:
1. List in one single document a comprehensive list of IPv6 features
for a mobile device, including both IPv6-only and dual-stack
mobile deployment contexts. These features cover various packet
core architectures such as General Packet Radio Service (GPRS) or
Evolved Packet Core (EPC).
2. Help operators with the detailed device requirement list
preparation (to be exchanged with device suppliers). This is
also a contribution to harmonize operators' requirements towards
3. Inform vendors of a set of features to allow for IPv6
connectivity and IPv4 service continuity (over an IPv6-only
The recommendations do not include 3GPP release details. For more
information on the 3GPP release details, the reader may refer to
Section 6.2 of [RFC6459]. More details can be found at [R3GPP].
Some of the features listed in this profile document could require
that dedicated functions be activated at the network side. It is out
of scope of this document to list these network-side functions.
A detailed overview of IPv6 support in 3GPP architectures is provided
in [RFC6459]. IPv6-only considerations in mobile networks are
further discussed in [RFC6342].
This document is organized as follows:
o Section 2 lists generic recommendations, including functionalities
to provide IPv4 service over an IPv6-only connectivity.
o Section 3 enumerates a set of recommendations for cellular devices
with Local Area Network (LAN) capabilities (e.g., Customer Edge
(CE) routers with cellular access link, dongles with tethering
o Section 4 identifies a set of advanced recommendations to fulfill
requirements of critical services such as VoLTE (Voice over LTE).
This document makes use of the terms defined in [RFC6459]. In
addition, the following terms are used:
o 3GPP cellular host (or "cellular host" for short): denotes a 3GPP
device that can be connected to 3GPP mobile networks.
o 3GPP cellular device (or "cellular device" for short): refers to a
cellular host that supports the capability to share its 3GPP
o IPv4 service continuity: denotes the features used to provide
access to IPv4-only services to customers serviced with an
IPv6-only connectivity. A typical example of IPv4 service
continuity technique is Network Address and Protocol Translation
from IPv6 Clients to IPv4 Servers (NAT64) [RFC6146].
PREFIX64 denotes an IPv6 prefix used to build IPv4-converted IPv6
A 3GPP mobile network can be used to connect various User Equipment
(UE) such as a mobile telephone or a CE router. Because of this
diversity of terminals, it is necessary to define a set of IPv6
functionalities valid for any node directly connecting to a 3GPP
mobile network. This document describes these functionalities.
The machine-to-machine (M2M) devices profile is out of scope.
This document is structured to provide the generic IPv6
recommendations that are valid for all nodes, whatever their function
(e.g., host or CE router) or service (e.g., Session Initiation
Protocol (SIP) [RFC3261]) capability. The document also contains
sections covering specific functionalities for devices providing some
LAN functions (e.g., mobile CE router or broadband dongles).
The recommendations listed below are valid for both 3GPP GPRS and
3GPP Evolved Packet System (EPS). For EPS, the term "PDN-Connection"
is used instead of PDP-Context. Other non-3GPP accesses [TS.23402]
are out of scope of this document.
This profile is a superset of that of the IPv6 profile for 3GPP
Cellular Hosts [RFC7066], which is in turn a superset of IPv6 Node
Requirements [RFC6434]. It targets cellular nodes, including GPRS
and EPC, that require features to ensure IPv4 service delivery over
an IPv6-only transport in addition to the base IPv6 service.
Moreover, this profile also covers cellular CE routers that are used
in various mobile broadband deployments. Recommendations inspired
from real deployment experiences (e.g., roaming) are included in this
profile. Also, this profile sketches recommendations for the sake of
deterministic behaviors of cellular devices when the same
configuration information is received over several channels.
For conflicting recommendations in [RFC7066] and [RFC6434] (e.g.,
Neighbor Discovery Protocol), this profile adheres to [RFC7066].
Indeed, the support of Neighbor Discovery Protocol is mandatory in
3GPP cellular environment as it is the only way to convey an IPv6
prefix towards the 3GPP cellular device. In particular, Maximum
Transmission Unit (MTU) communication via Router Advertisement (RA)
must be supported since many 3GPP networks do not have a standard MTU
This profile uses a stronger language for the support of Prefix
Delegation compared to [RFC7066]. The main motivation is that
cellular networks are more and more perceived as an alternative to
fixed networks for home IP-based services delivery; especially with
the advent of smartphones and 3GPP data dongles. There is a need for
an efficient mechanism to assign larger prefixes to cellular hosts so
that each LAN segment can get its own /64 prefix and multi-link
subnet issues to be avoided. The support of this functionality in
both cellular and fixed networks is key for fixed-mobile convergence.
The use of address-family-dependent Application Programming
Interfaces (APIs) or hard-coded IPv4 address literals may lead to
broken applications when IPv6 connectivity is in use. As such, means
to minimize broken applications when the cellular host is attached to
an IPv6-only network should be encouraged. Particularly, (1) name
resolution libraries (e.g., [RFC3596]) must support both IPv4 and
IPv6; (2) applications must be independent of the underlying IP
address family; and (3) applications relying upon Uniform Resource
Identifiers (URIs) must follow [RFC3986] and its updates. Note, some
IETF specifications (e.g., SIP [RFC3261]) contains broken IPv6
Augmented Backus-Naur Form (ABNF) and rules to compare URIs with
embedded IPv6 addresses; fixes (e.g., [RFC5954]) must be used
The recommendations included in each section are listed in a priority
This document is not a standard, and conformance with it is not
required in order to claim conformance with IETF standards for IPv6.
Compliance with this profile does not require the support of all
enclosed items. Obviously, the support of the full set of features
may not be required in some deployment contexts. However, the
authors believe that not supporting relevant features included in
this profile (e.g., Customer-Side Translator (CLAT) [RFC6877]) may
lead to a degraded level of service.
2. Connectivity Recommendations
This section identifies the main connectivity recommendations to be
followed by a cellular host to attach to a network using IPv6 in
addition to what is defined in [RFC6434] and [RFC7066]. Both dual-
stack and IPv6-only deployment models are considered. IPv4 service
continuity features are listed in this section because these are
critical for operators with an IPv6-only deployment model. These
recommendations apply also for cellular devices (see Section 3).
C_REC#1: In order to allow each operator to select their own
strategy regarding IPv6 introduction, the cellular host
must support both IPv6 and IPv4v6 PDP-Contexts [TS.23060].
IPv4, IPv6, or IPv4v6 PDP-Context request acceptance
depends on the cellular network configuration.
C_REC#2: The cellular host must comply with the behavior defined in
[TS.23060], [TS.23401], and [TS.24008] for requesting a
In particular, the cellular host must request by default an
IPv6 PDP-Context if the cellular host is IPv6-only and
request an IPv4v6 PDP-Context if the cellular host is dual-
stack or when the cellular host is not aware of
connectivity types requested by devices connected to it
(e.g., a cellular host with LAN capabilities as discussed
in Section 3):
* If the requested IPv4v6 PDP-Context is not supported by
the network but IPv4 and IPv6 PDP types are allowed,
then the cellular host will be configured with an IPv4
address or an IPv6 prefix by the network. It must
initiate another PDP-Context activation of the other
address family in addition to the one already activated
for a given Access Point Name (APN). The purpose of
initiating a second PDP-Context is to achieve dual-stack
connectivity by means of two PDP-Contexts.
* If the subscription data or network configuration allows
only one IP address family (IPv4 or IPv6), the cellular
host must not request a second PDP-Context to the same
APN for the other IP address family.
The network informs the cellular host about allowed Packet
Data Protocol (PDP) types by means of Session Management
(SM) cause codes. In particular, the following cause codes
can be returned:
* cause #50 "PDP type IPv4 only allowed" - This cause code
is used by the network to indicate that only PDP type
IPv4 is allowed for the requested Public Data Network
* cause #51 "PDP type IPv6 only allowed" - This cause code
is used by the network to indicate that only PDP type
IPv6 is allowed for the requested PDN connectivity.
* cause #52 "single address bearers only allowed" - This
cause code is used by the network to indicate that the
requested PDN connectivity is accepted with the
restriction that only single IP version bearers are
The text above focuses on the specification (an excerpt
from [TS.23060], [TS.23401], and [TS.24008]) that explains
the behavior for requesting IPv6-related PDP-Context(s).
C_REC#3: The cellular host must support the Protocol Configuration
Options (PCOs) [TS.24008] to retrieve the IPv6 address(es)
of the Recursive DNS server(s).
The 3GPP network communicates parameters by means of the
protocol configuration options information element when
activating, modifying, or deactivating a PDP-Context.
PCO is a convenient method to inform the cellular host
about various services, including DNS server
information. It does not require additional protocol to
be supported by the cellular host and it is already
deployed in IPv4 cellular networks to convey such DNS
C_REC#4: The cellular host must support IPv6-aware Traffic Flow
Templates (TFTs) [TS.24008].
Traffic Flow Templates are employing a packet filter to
couple an IP traffic with a PDP-Context. Thus, a
dedicated PDP-Context and radio resources can be
provided by the cellular network for certain IP traffic.
C_REC#5: If the cellular host receives the DNS information in
several channels for the same interface, the following
preference order must be followed:
The purpose of this recommendation is to guarantee for a
deterministic behavior to be followed by all cellular hosts
when the DNS information is received in various channels.
C_REC#6: Because of potential operational deficiencies to be
experienced in some roaming situations, the cellular host
must be able to be configured with a home PDP-Context
type(s) and a roaming PDP-Context type(s). The purpose of
the roaming profile is to limit the PDP type(s) requested
by the cellular host when out of the home network. Note
that distinct PDP type(s) and APN(s) can be configured for
home and roaming cases.
A detailed analysis of roaming failure cases is included
The configuration can be either local to the device or
be managed dynamically using, for example, Open Mobile
Alliance (OMA) management. The support of dynamic means
C_REC#7: In order to ensure IPv4 service continuity in an IPv6-only
deployment context, the cellular host should support a
method to learn PREFIX64(s).
In the context of NAT64, IPv6-enabled applications
relying on address referrals will fail because an
IPv6-only client will not be able to make use of an IPv4
address received in a referral. This feature allows for
solving the referral problem (because an IPv6-enabled
application can construct IPv4-embedded IPv6 addresses
[RFC6052]) and, also, for distinguishing between
IPv4-converted IPv6 addresses and native IPv6 addresses.
In other words, this feature contributes to offload both
the CLAT module and NAT64 devices. Refer to Section 3
of [RFC7051] for an inventory of the issues related to
the discovery of PREFIX64(s).
In environments based on the Port Control Protocol
(PCP), cellular hosts should follow [RFC7225] to learn
the IPv6 Prefix used by an upstream PCP-controlled NAT64
device. If PCP is not enabled, the cellular host should
implement the method specified in [RFC7050] to retrieve
C_REC#8: In order to ensure IPv4 service continuity in an IPv6-only
deployment context, the cellular host should implement the
CLAT [RFC6877] function in compliance with [RFC6052],
[RFC6145], and [RFC6146].
The CLAT function in the cellular host allows for
IPv4-only application and IPv4 referrals to work on an
IPv6-only connectivity. The more applications are
address family independent, the less the CLAT function
is solicited. The CLAT function requires a NAT64
capability [RFC6146] in the network.
The cellular host should only invoke CLAT in the absence
of IPv4 connectivity on the cellular side, i.e., when
the network does not assign an IPv4 address on the
cellular interface. Note, NAT64 assumes an IPv6-only
The IPv4 Service Continuity Prefix used by CLAT is
defined in [RFC7335].
CLAT and/or NAT64 do not interfere with native IPv6
CLAT may not be required in some contexts, e.g., if
other solutions such as Bump-in-the-Host (BIH) [RFC6535]
The cellular device can act as a CE router connecting
various IP hosts on a LAN segment; this is also the case
with using WLAN (Wireless LAN) tethering or a WLAN
hotspot from the cellular device. Some of these IP
hosts can be dual-stack, others are IPv6-only or
IPv4-only. IPv6-only connectivity on the cellular
device does not allow IPv4-only sessions to be
established for hosts connected on the LAN segment of
the cellular device. IPv4 session establishment
initiated from hosts located on the LAN segment side and
destined for IPv4 nodes must be maintained. A solution
is to integrate the CLAT function to the LAN segment in
the cellular device.
C_REC#9: The cellular host may be able to be configured to limit PDP
type(s) for a given APN. The default mode is to allow all
supported PDP types. Note, C_REC#2 discusses the default
behavior for requesting PDP-Context type(s).
This feature is useful to drive the behavior of the UE
to be aligned with (1) service-specific constraints such
as the use of IPv6-only for VoLTE, (2) network
conditions with regard to the support of specific PDP
types (e.g., IPv4v6 PDP-Context is not supported), (3)
IPv4 sunset objectives, (4) subscription data, etc.
Note, a cellular host changing its connection between an
IPv6-specific APN and an IPv4-specific APN will
interrupt related network connections. This may be
considered as a brokenness situation by some
The configuration can be either local to the device or
be managed dynamically using, for example, OMA
management. The support of dynamic means is encouraged.
3. Recommendations for Cellular Devices with LAN Capabilities
This section focuses on cellular devices (e.g., CE routers,
smartphones, or dongles with tethering features) that provide IP
connectivity to other devices connected to them. In this case, all
connected devices are sharing the same 2G, 3G, or LTE connection. In
addition to the generic recommendations listed in Section 2, these
cellular devices have to meet the recommendations listed below.
L_REC#1: For deployments that require that the same /64 prefix be
shared, the cellular device should support [RFC7278] to
enable sharing a /64 prefix between the LAN and the WAN
interfaces. The WAN interface is the one towards the
Gateway GPRS Support Node (GGSN) / Packet Data Network
Prefix Delegation (refer to L_REC#2) is the target
solution for distributing prefixes in the LAN side but,
because the device may attach to earlier 3GPP release
networks, a means to share a /64 prefix is also
[RFC7278] must be invoked only if Prefix Delegation is
not in use.
L_REC#2: The cellular device must support Prefix Delegation
capabilities [RFC3633] and must support the Prefix Exclude
Option for DHCPv6-based Prefix Delegation as defined in
[RFC6603]. Particularly, it must behave as a Requesting
Cellular networks are more and more perceived as an
alternative to fixed broadband networks for home IP-
based services delivery; especially with the advent of
smartphones and 3GPP data dongles. There is a need for
an efficient mechanism to assign larger prefixes (other
than /64s) to cellular hosts so that each LAN segment
can get its own /64 prefix and multi-link subnet issues
to be avoided.
In case a prefix is delegated to a cellular host using
DHCPv6, the cellular device will be configured with two
(1) one for the 3GPP link allocated using the Stateless
Address Autoconfiguration (SLAAC) mechanism and
(2) another one delegated for LANs acquired during the
Prefix Delegation operation.
Note that the 3GPP network architecture requires both
the WAN and the delegated prefix to be aggregatable so
the subscriber can be identified using a single prefix.
Without the Prefix Exclude Option, the delegating router
(GGSN/PGW) will have to ensure compliance with [RFC3633]
(e.g., halving the delegated prefix and assigning the
WAN prefix out of the first half and the prefix to be
delegated to the terminal from the second half).
Because Prefix Delegation capabilities may not be
available in some attached networks, L_REC#1 is strongly
recommended to accommodate early deployments.
L_REC#3: The cellular CE router must be compliant with the
requirements specified in [RFC7084].
There are several deployments, particularly in emerging
countries, that rely on mobile networks to provide
broadband services (e.g., customers are provided with
mobile CE routers).
Note, this profile does not require IPv4 service
continuity techniques listed in Section 4.4 of [RFC7084]
because those are specific to fixed networks. IPv4
service continuity techniques specific to the mobile
networks are included in this profile.
This recommendation does not apply to handsets with
tethering capabilities; it is specific to cellular CE
routers in order to ensure the same IPv6 functional
parity for both fixed and cellular CE routers. Note,
modern CE routers are designed with advanced functions
such as link aggregation that consists in optimizing the
network usage by aggregating the connectivity resources
offered via various interfaces (e.g., Digital Subscriber
Line (DSL), LTE, WLAN, etc.) or offloading the traffic
via a subset of interfaces. Ensuring IPv6 feature
parity among these interface types is important for the
sake of specification efficiency, service design
simplification, and validation effort optimization.
L_REC#4: If an RA MTU is advertised from the 3GPP network, the
cellular device should send RAs to the downstream attached
LAN devices with the same MTU as seen on the mobile
Receiving and relaying RA MTU values facilitates a more
harmonious functioning of the mobile core network where
end nodes transmit packets that do not exceed the MTU
size of the mobile network's tunnels that use the GPRS
Tunneling Protocol (GTP).
[TS.23060] indicates providing a link MTU value of 1358
octets to the 3GPP cellular device will prevent the IP
layer fragmentation within the transport network between
the cellular device and the GGSN/PGW. More details
about link MTU considerations can be found in Annex C of
4. Advanced Recommendations
This section identifies a set of advanced recommendations to fulfill
requirements of critical services such as VoLTE. These
recommendations apply for mobile hosts, including mobile devices.
A_REC#1: The cellular host must support the RObust Header
Compression (ROHC) RTP Profile (0x0001) and the ROHC UDP
Profile (0x0002) for IPv6 [RFC5795]. Other ROHC profiles
may be supported.
Bandwidth in cellular networks must be optimized as much
as possible. ROHC provides a solution to reduce
bandwidth consumption and to reduce the impact of having
bigger packet headers in IPv6 compared to IPv4.
The "RTP/UDP/IP" ROHC profile (0x0001) to compress RTP
packets and the "UDP/IP" ROHC profile (0x0002) to
compress Real-time Transport Control Protocol (RTCP)
packets are required for VoLTE by Section 4.1 of
IR.92.7.0 [IR92]. Note, [IR92] indicates that the host
must be able to apply the compression to packets that
are carried over the voice-media-dedicated radio bearer.
A_REC#2: The cellular host should support PCP [RFC6887].
The support of PCP is seen as a driver to save battery
consumption exacerbated by keep-alive messages. PCP
also gives the possibility of enabling incoming
connections to the cellular device. Indeed, because
several stateful devices may be deployed in wireless
networks (e.g., NAT64 and/or IPv6 Firewalls), PCP can be
used by the cellular host to control network-based NAT64
and IPv6 Firewall functions that will reduce per-
application signaling and save battery consumption.
According to [Power], the consumption of a cellular
device with a keep-alive interval equal to 20 seconds
(which is the default value in [RFC3948], for example)
is 29 mA (2G) / 34 mA (3G). This consumption is reduced
to 16 mA (2G) / 24 mA (3G) when the interval is
increased to 40 seconds, to 9.1 mA (2G) / 16 mA (3G) if
the interval is equal to 150 seconds, and to 7.3 mA (2G)
/ 14 mA (3G) if the interval is equal to 180 seconds.
When no keep-alive is issued, the consumption would be
5.2 mA (2G) / 6.1 mA (3G). The impact of keepalive
messages would be more severe if multiple applications
are issuing those messages (e.g., SIP, IPsec, etc.).
Deploying PCP allows cellular hosts to manage protocols
that convey IP addresses and/or port numbers (see
Section 2.2 of [RFC6889]) without requiring Application
Level Gateways (ALGs) to be enabled at the network side
(e.g., NAT64). Avoiding soliciting ALGs makes it easier
to develop a service without any adherence with the
underlying transport network.
A_REC#3: In order for host-based validation of DNS Security
Extensions (DNSSEC) to continue to function in an IPv6-only
connectivity with NAT64 deployment context, the cellular
host should embed a DNS64 function ([RFC6147]).
This is called "DNS64 in stub-resolver mode" in
As discussed in Section 5.5 of [RFC6147], a security-
aware and validating host has to perform the DNS64
Because synthetic AAAA records cannot be successfully
validated in a host, learning the PREFIX64 used to
construct IPv4-converted IPv6 addresses allows the use
of DNSSEC [RFC4033] [RFC4034] [RFC4035]. Means to
configure or discover a PREFIX64 are required on the
cellular device as discussed in C_REC#7.
[RFC7051] discusses why a security-aware and validating
host has to perform the DNS64 function locally and why
it has to be able to learn the proper PREFIX64(s).
A_REC#4: When the cellular host is dual-stack connected (i.e.,
configured with an IPv4 address and IPv6 prefix), it should
support means to prefer a native IPv6 connection over a
connection established through translation devices (e.g.,
NAT44 and NAT64).
When both IPv4 and IPv6 DNS servers are configured, a
dual-stack host must first contact its IPv6 DNS server.
This preference allows it to offload IPv4-only DNS
Cellular hosts should follow the procedure specified in
[RFC6724] for source address selection.
5. Security Considerations
The security considerations identified in [RFC7066] and [RFC6459] are
to be taken into account.
In the case of cellular CE routers, compliance with L_REC#3 entails
compliance with [RFC7084], which in turn recommends compliance with
Recommended Simple Security Capabilities in Customer Premises
Equipment (CPE) for Providing Residential IPv6 Internet Service
[RFC6092]. Therefore, the security considerations in Section 6 of
[RFC6092] are relevant. In particular, it bears repeating here that
the true impact of stateful filtering may be a reduction in security
and that the IETF makes no statement, expressed or implied, as to
whether using the capabilities described in any of these documents
ultimately improves security for any individual users or for the
Internet community as a whole.
The cellular host must be able to generate IPv6 addresses that
preserve privacy. The activation of the privacy extension (e.g.,
using [RFC7217]) makes it more difficult to track a host over time
when compared to using a permanent Interface Identifier. Tracking a
host is still possible based on the first 64 bits of the IPv6
address. Means to prevent against such tracking issues may be
enabled in the network side. Note, privacy extensions are required
by regulatory bodies in some countries.
Host-based validation of DNSSEC is discussed in A_REC#3 (see
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