wdiff rfc7066v1.txt rfc7066.txt

Internet Engineering Task Force (IETF) J. Korhonen, Ed.
Request for Comments: 7066 Renesas Mobile Broadcom
Obsoletes: 3316 J. Arkko, Ed.
Category: Informational Ericsson
ISSN: 2070-1721 T. Savolainen
Nokia
S. Krishnan
Ericsson
October 2013

IPv6 for Third Generation Partnership Project (3GPP) Cellular Hosts

Abstract

As the deployment of third and fourth generation cellular networks
progresses, a large number of cellular hosts are being connected to
the Internet. Standardization organizations have made the Internet
Protocol version 6 (IPv6) mandatory in their specifications.
However, the concept of IPv6 covers many aspects and numerous
specifications. In addition, the characteristics of cellular links
in terms of bandwidth, cost, and delay put special requirements on
how IPv6 is used. This document considers IPv6 for cellular hosts
that attach to the General Packet Radio Service (GPRS), Universal
Mobile Telecommunications System (UMTS), or Evolved Packet System
(EPS) networks (hereafter collectively referred to as Third
Generation Partnership Project (3GPP) networks). This document also
lists specific IPv6 functionalities that need to be implemented in
addition to what is already prescribed in the IPv6 Node Requirements
document.
document (RFC 6434). It also discusses some issues related to the
use of these components when operating in these networks. This
document obsoletes RFC 3316.

Status of This Memo

This document is not an Internet Standards Track specification; it is
published for informational purposes.

This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7066.

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
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Scope of This Document . . . . . . . . . . . . . . . . . 3
1.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Cellular Host IPv6 Features . . . . . . . . . . . . . . . 6 5
2. Basic IP . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Internet Protocol Version 6 . . . . . . . . . . . . . . . 6
2.2. Neighbor Discovery in 3GPP Networks . . . . . . . . . . . 6
2.3. Stateless Address Autoconfiguration . . . . . . . . . . . 8 7
2.4. IP Version 6 over PPP . . . . . . . . . . . . . . . . . . 8
2.5. Multicast Listener Discovery (MLD) for IPv6 . . . . . . . 9
2.6. Privacy Extensions for Address Configuration in IPv6 . . 9
2.7. Dynamic Host Configuration Protocol for IPv6 (DHCPv6) . . 9
2.8. DHCPv6 Prefix Delegation . . . . . . . . . . . . . . . . 10 9
2.9. Router Preferences and More-Specific Routes . . . . . . . 10
2.10. Neighbor Discovery and Additional Host Configuration . . 10
3. IP Security . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1. Extension Header Considerations . . . . . . . . . . . . . 10
4. Mobility . . . . . . . . . . . . . . . . . . . . . . . . . . 11 10
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.1. Normative References . . . . . . . . . . . . . . . . . . 13
7.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. Cellular Host IPv6 Addressing in the 3GPP Model . . 16
Appendix B. Changes from RFC 3316 . . . . . . . . . . . . . . . 17

1. Introduction

Technologies such as GPRS (General Packet Radio Service), UMTS
(Universal Mobile Telecommunications System), Evolved Packet System
(EPS), CDMA2000 (Code Division Multiple Access 2000), and eHRPD
(Enhanced High Rate Packet Data) are making it possible for cellular
hosts to have an always-on connection to the Internet. IPv6
[RFC2460] has become essential to such networks as the number of
cellular hosts is increasing rapidly. Standardization organizations
working with cellular technologies have recognized this and made IPv6
mandatory in their specifications.

Support for IPv6 and the introduction of UMTS started with 3GPP
Release-99 networks and hosts. For a detailed description of IPv6 in
3GPP networks, including the Evolved Packet System, see [RFC6459].

1.1. Scope of This Document

For the purpose of this document, a cellular interface is considered
to be the interface to a cellular access network based on the
following standards: 3GPP GPRS and UMTS Release-99 and Release-4 to
Release-11; EPS Release-8 to Release-11; and future UMTS or EPS
releases. A cellular host is considered to be a host with such a
cellular interface.

This document complements the IPv6 Node Requirements [RFC6434] in
places where clarifications are needed with discussion on the use of
these selected IPv6 specifications when operating over a cellular
interface. Such a specification is necessary in order to enable the
optimal use of IPv6 in a cellular network environment. The
description is made from the point of view of a cellular host.
Complementary access technologies may be supported by the cellular
host, but those are not discussed in detail. Important
considerations are given in order to eliminate unnecessary user
confusion over configuration options, ensure interoperability, and
provide an easy reference for those who are implementing IPv6 in a
cellular host. It is necessary to ensure that cellular hosts are
good citizens of the Internet.

This document is informational in its nature, and it is not intended
to replace, update, or contradict any IPv6 standards documents or the
IPv6 Node Requirements [RFC6434].

This document is primarily targeted to the implementers of cellular
hosts that will be used with the cellular networks listed in the
scope. this
document. This document provides guidance on which IPv6-related
specifications are to be implemented in such cellular hosts. Parts
of this document may also apply to other cellular link types, but
this document does not provide any detailed analysis on other link
types. This document should not be used as a definitive list of IPv6
functionalities for cellular links other than those listed above.
Future changes in 3GPP networks that impact host implementations may
result in updates to this document.

There are different ways to implement cellular hosts:

o The host can be a "closed" device with optimized built-in
applications, with no possibility to add or download applications
that can have IP communications. An example of such a host is a
very simple form of a mobile phone.

o The host can be an open device, e.g., a "smart phone" where it is
possible to download applications to expand the functionality of
the device.

o The cellular radio modem part can be separated from the host IP
stack with an interface. One example of such a host is a laptop
computer that uses a USB cellular modem for cellular access.

If a cellular host has additional IP-capable interfaces (such as
Ethernet, WLAN, Bluetooth, etc.), then there may be additional
requirements for the device, beyond what is discussed in this
document. Additionally, this document does not make any
recommendations on the functionality required on laptop computers
having a cellular interface such as an embedded modem or a USB modem
stick, other than recommending link-specific behavior on the cellular
link.

This document discusses IPv6 functionality as of the time when this
document was written. Ongoing work on IPv6 may affect what is
required of future hosts.

Transition mechanisms used by cellular hosts are not in the scope of
this document and are left for further study. The primary transition
mechanism supported by 3GPP is dual-stack [RFC4213]. Dual-stack-
capable bearer support has been added to GPRS starting from 3GPP
Release-9 and to EPS starting from Release-8 [RFC6459], whereas the
earlier 3GPP releases required multiple single IP version bearers to
support dual-stack.

1.2. Abbreviations

2G Second Generation Mobile Telecommunications, such as Global
System for Mobile Communications (GSM) and GPRS technologies.

3G Third Generation Mobile Telecommunications, such as UMTS
technology.

4G Fourth Generation Mobile Telecommunications, such as LTE
technology.

3GPP Third Generation Partnership Project. Throughout the document,
the term "3GPP networks" refers to architectures standardized
by 3GPP, in Second, Third, and Fourth Generation releases: 99,
4, and 5, as well as future releases.

APN Access Point Name. The APN is a logical name referring to a
GGSN and/or a PGW, and an external network.

EPC Evolved Packet Core.

EPS Evolved Packet System.

ESP Encapsulating Security Payload.

GGSN Gateway GPRS Support Node (a default router for 3GPP IPv6
cellular hosts in GPRS).

GPRS General Packet Radio Service.

LTE Long Term Evolution.

MT Mobile Terminal, for example, a mobile phone handset.

MTU Maximum Transmission Unit.

PDN Packet Data Network.

PDP Packet Data Protocol.

PGW Packet Data Network Gateway (the default router for 3GPP IPv6
cellular hosts in EPS).

SGW Serving Gateway (the user plane equivalent of a Serving GPRS
Support Node (SGSN) in EPS (and the default router for 3GPP
IPv6 cellular hosts when using Proxy Mobile IPv6 (PMIPv6))).

TE Terminal Equipment, for example, a laptop attached through a
3GPP handset.

UMTS Universal Mobile Telecommunications System.

WLAN Wireless Local Area Network.

1.3. Cellular Host IPv6 Features

This document lists IPv6 features for cellular hosts that hosts; these features
are split into three groups. groups and are discussed below.

Basic IP
In this group, the basic IPv6 features essential for cellular
hosts are listed and described.

IP Security

In this group, the parts related to IP Security are described.

Mobility

In this group, IP-layer mobility issues are described.

2. Basic IP

For most parts, refer to the IPv6 Node Requirements document
[RFC6434].

2.1. Internet Protocol Version 6

The Internet Protocol version 6 (IPv6) is specified in [RFC2460].
This specification is a mandatory part of IPv6. A cellular host must
conform to the generic IPv6 host requirements [RFC6434], unless
specifically pointed out otherwise in this document.

2.2. Neighbor Discovery in 3GPP Networks

A cellular host must support Neighbor Solicitation and Neighbor
Advertisement messages [RFC4861]. Some further notes on how these
are Neighbor
Discovery is applied in the particular type of an interface can be useful,
however:
useful.

In 3GPP networks, some Neighbor Discovery messages can be unnecessary
in certain cases. GPRS, UMTS, and EPS links resemble a point-to-
point link; hence, the cellular host's only neighbor on the cellular
link is the default router that is already known through Router
Discovery. The cellular host always solicits for routers when the
cellular interface is brought up (as described in [RFC4861],
Section 6.3.7).

There are no link-layer addresses on the 3GPP cellular link
technology. Therefore, address resolution and next-hop determination
are not needed. If the cellular host still attempts to do address
resolution, e.g., for the default router, it must be understood that
the GGSN/PGW may not even answer the address resolution Neighbor
Solicitations. And even if it does, the Neighbor Advertisement is
unlikely to contain the Target link-layer address option as there are
no link-layer addresses on the 3GPP cellular link technology.

The cellular host must support Neighbor Unreachability Detection
(NUD) as specified in [RFC4861]. Note that the link-layer address
considerations above also apply to NUD. The NUD-triggered Neighbor
Advertisement is also unlikely to contain the Target link-layer
address option as there are no link-layer addresses. The cellular
host should also be prepared for NUD initiated by a router (i.e., GGSN/PGW) initiated
NUD.
GGSN/PGW). However, it is unlikely a router to host router-to-host NUD would ever
take place on GPRS, UMTS, or EPS links. See Appendix A for more
discussion on the router to host router-to-host NUD.

In 3GPP networks, it is desirable to reduce any additional periodic
signaling. Therefore, the cellular host should include a mechanism
in upper-layer protocols to provide reachability confirmations when
two-way IP-layer reachability can be confirmed (see [RFC4861],
Section 7.3.1). These confirmations would allow the suppression of
NUD-related messages in most cases.

Host TCP implementation should provide reachability confirmation in
the manner explained in [RFC4861], Section 7.3.1.

The widespread use of UDP in 3GPP networks poses a problem for
providing reachability confirmation. As UDP itself is unable to
provide such confirmation, applications running on top of UDP should
provide the confirmation where possible. In particular, when UDP is
used for transporting DNS, the DNS response should be used as a basis
for reachability confirmation. Similarly, when UDP is used to
transport RTP [RFC3550], the RTP Control Protocol (RTCP) [RFC3550]
feedback should be used as a basis for the reachability confirmation.
If an RTCP packet is received with a reception report block
indicating some packets have gone through, then packets are reaching
the peer. If they have reached the peer, they have also reached the
neighbor.

When UDP is used for transporting SIP [RFC3261], responses to SIP
requests should be used as the confirmation that packets sent to the
peer are reaching it. When the cellular host is acting as the
server-side SIP node, no such confirmation is generally available.
However, a host may interpret the receipt of a SIP ACK request as
confirmation that the previously sent response to a SIP INVITE
request has reached the peer.

2.3. Stateless Address Autoconfiguration

IPv6 Stateless Address Autoconfiguration is defined in [RFC4862].
This specification is a mandatory part of IPv6 and also the only
mandatory method to configure an IPv6 address in a 3GPP cellular
host.

A cellular host in a 3GPP network must process a Router Advertisement
as stated in [RFC4862]. The Router Advertisement contains a maximum
of one prefix information option with lifetimes set to infinite (both
valid and preferred lifetimes). The advertised prefix cannot ever be
used for on-link determination (see [RFC6459], Section 5.2), and the
lifetime of the advertised prefix is tied to the PDP Context/PDN
Connection lifetime. Keeping the forward compatibility in mind,
there is no reason for the 3GPP cellular host to have 3GPP-specific
handling of the prefix information option(s) although 3GPP
specifications state that the Router Advertisement may contain a
maximum of one prefix information option and the lifetimes are set to
infinite.

Hosts in 3GPP networks can set DupAddrDetectTransmits equal to zero,
as each assigned prefix is unique within its scope when advertised
using 3GPP IPv6 Stateless Address Autoconfiguration. In addition,
the default router (GGSN/PGW) will not configure any addresses on its
interfaces based on prefixes advertised to IPv6 cellular hosts on
those interfaces. Thus, the host is not required to perform
Duplicate Address Detection on the cellular interface.

Furthermore, the GGSN/PGW will provide the cellular host with an
interface identifier that must be used for link-local address
configuration. The link-local address configured from this interface
identifier is guaranteed not to collide with the link-local address
that the GGSN/PGW uses. Thus, the cellular host is not required to
perform Duplicate Address Detection for the link-local address on the
cellular interface.

See Appendix A for more details on 3GPP IPv6 Stateless Address
Autoconfiguration.

2.4. IP Version 6 over PPP

A cellular host in a 3GPP network that supports PPP [RFC1661] on the
interface between the MT and the TE must support the IPv6 Control
Protocol (IPV6CP) [RFC5072] interface identifier option. This option
is needed to be able to connect other devices to the Internet using a
PPP link between the cellular device (MT, e.g., a USB dongle) and
other devices (TE, e.g., a laptop). The MT performs the PDP Context
activation based on a request from the TE. This results in an
interface identifier being suggested by the MT to the TE, using the
IPV6CP option. To avoid any duplication in link-local addresses
between the TE and the GGSN/PGW, the MT must always reject other
suggested interface identifiers by the TE. This results in the TE
always using the interface identifier suggested by the GGSN/PGW for
its link-local address.

The rejection of interface identifiers suggested by the TE is only
done for creation of link-local addresses, according to 3GPP
specifications. The use of privacy addresses [RFC4941] or similar
technologies for unique local IPv6 unicast addresses [RFC4193] and
global addresses is not affected by the above procedure.

2.5. Multicast Listener Discovery (MLD) for IPv6

Within 3GPP networks, hosts connect to their default routers (GGSN/
PGW) via point-to-point links. Moreover, there are exactly two IP
devices connected to the point-to-point link, and no attempt is made
(at the link layer) to suppress the forwarding of multicast traffic.
Consequently, sending MLD reports for link-local addresses in a 3GPP
environment is not necessary, although sending them causes no harm or
interoperability issues. Refer to Section 5.10 of [RFC6434] for MLD
usage for multicast group knowledge that is not link-local.

2.6. Privacy Extensions for Address Configuration in IPv6

Privacy Extensions for Stateless Address Autoconfiguration [RFC4941]
or other similar technologies may be supported by a cellular host.
Privacy, in general, is important for the Internet. In 3GPP
networks, the lifetime of an address assignment depends on many
factors such as radio coverage, device status, and user preferences.
As a result, the prefix the cellular host uses is also subject to
frequent changes.

Refer to Section 6 for a discussion of the benefits of Privacy
Extensions in a 3GPP network.

2.7. Dynamic Host Configuration Protocol for IPv6 (DHCPv6)

As of 3GPP Release-11, the Dynamic Host Configuration Protocol for
IPv6 (DHCPv6) [RFC3315] is neither required nor supported for address
autoconfiguration. The IPv6 stateless autoconfiguration Stateless Address Autoconfiguration still
remains the only mandatory address configuration method. However,
DHCPv6 may be useful for other configuration needs on a cellular
host, e.g., Stateless DHCPv6 [RFC3736] may be used to configure DNS
and SIP server addresses, and DHCPv6 Prefix Delegation [RFC3633] may
be used to delegate a prefix to the cellular host for use on its
downstream non-cellular links.

2.8. DHCPv6 Prefix Delegation

Starting from Release-10, DHCPv6 Prefix Delegation was added as an
optional feature to the 3GPP system architecture [RFC3633]. The
Prefix Delegation model defined for Release-10 requires that the /64
IPv6 prefix assigned to the cellular host on the 3GPP link must
aggregate with the shorter delegated IPv6 prefix. The cellular host
should implement the Prefix Exclude Option for DHCPv6 Prefix
Delegation [RFC6603] (see [RFC6459], Section 5.3 for further
discussion).

2.9. Router Preferences and More-Specific Routes

The cellular host should implement the Default Router Preferences and
More-Specific Routes extension to Router Advertisement messages
[RFC4191]. These options may be useful for cellular hosts that also
have additional interfaces on which IPv6 is used.

2.10. Neighbor Discovery and Additional Host Configuration

The DNS server configuration is learned from the 3GPP link-layer
signaling. However, the cellular host should also implement the IPv6
Router Advertisement Options for DNS Configuration [RFC6106]. DHCPv6
is still optional for cellular hosts, and learning the DNS server
addresses from the link-layer signaling can be cumbersome when the MT
and the TE are separated using techniques other than the PPP
interface.

The cellular host should also honor the MTU option in the Router
Advertisement (see [RFC4861], Section 4.6.4). The 3GPP system
architecture uses extensive tunneling in its packet core network
below the 3GPP link, and this may lead to packet fragmentation
issues. Therefore, the GGSN/PGW may propose to the cellular host an
MTU that takes the additional tunneling overhead into account.

3. IP Security

IPsec [RFC4301] is a fundamental, but not mandatory, part of IPv6.
Refer to the IPv6 Node Requirements (Section 11 of [RFC6434]) for the
security requirements that also apply to cellular hosts.

3.1. Extension Header Considerations

Support for the Routing Header Type 0 (RH0) has been deprecated
[RFC5095]. Therefore, the cellular host should by default follow the
RH0 processing described in Section 3 of [RFC5095].

IPv6 packet fragmentation has known security concerns. The cellular
host must follow the handling of overlapping fragments as described
in [RFC5722], and the cellular host must not fragment any Neighbor
Discovery messages as described in [RFC6980].

4. Mobility
For the purposes of this document, IP mobility is not relevant. The
movement of cellular hosts within 3GPP networks is handled by link-
layer mechanisms in the majority of cases. 3GPP Release-8 introduced
Dual-Stack Mobile IPv6 (DSMIPv6) for client-based mobility [RFC5555].
Client-based IP mobility is optional in the 3GPP architecture.

5. Acknowledgements

The authors would like to thank the original authors for their
groundwork for this document: Gerben Kuijpers, John Loughney, Hesham
Soliman, and Juha Wiljakka.

The original [RFC3316] document was based on the results of a team
that included Peter Hedman and Pertti Suomela in addition to the
authors. Peter and Pertti have contributed both text and their IPv6
experience to this document.

The authors would like to thank Jim Bound, Brian Carpenter, Steve
Deering, Bob Hinden, Keith Moore, Thomas Narten, Erik Nordmark,
Michael Thomas, Margaret Wasserman, and others on the IPv6 WG mailing
list for their comments and input.

We would also like to thank David DeCamp, Karim El Malki, Markus
Isomaki, Petter Johnsen, Janne Rinne, Jonne Soininen, Vlad Stirbu,
and Shabnam Sultana for their comments and input in preparation of
this document.

For this revised version of [RFC3316] the authors would like to thank
Dave Thaler, Ales Vizdal, Gang Chen, Ray Hunter, Charlie Kaufman,
Owen DeLong, and Alexey Melnikov for their comments, reviews, and
input.

6. Security Considerations

This document does not specify any new protocols or functionalities,
and as such, it does not introduce any new security vulnerabilities.
However, specific profiles of IPv6 functionality are proposed for
different situations, and vulnerabilities may open or close depending
on which functionality is included and what is not. There are also
aspects of the cellular environment that make certain types of
vulnerabilities more severe. The following issues are discussed:

o The suggested limitations (Section 3.1) in the processing of
extension headers also limits exposure to Denial-of-Service (DoS)
attacks through cellular hosts.

o IPv6 addressing privacy [RFC4941] or similar technology may be
used in cellular hosts. However, it should be noted that in the
3GPP model, the network would assign a new prefix, in most cases,
to hosts in roaming situations and typically, situations; the network would also typically
assign a new prefix when the cellular hosts activate a PDP Context
or a PDN Connection. 3GPP devices must not use interface
identifiers that are unique to the device, so the only difference
in address between 3GPP devices using Stateless Address
Autoconfiguration is in the prefix. This means that 3GPP networks
will already provide a limited form of addressing privacy, and no
global tracking of a single host is possible through its address.
On the other hand, since a GGSN/
PGW's GGSN/PGW's coverage area is expected to
be very large when compared to currently deployed default routers
(no handovers between GGSN/PGWs are possible), a cellular host can
keep a prefix for a long time. Hence, IPv6 addressing privacy can
be used for additional privacy during the time the host is on and
in the same area. The privacy features can also be used to, e.g.,
make different transport sessions appear to come from different IP
addresses. However, it is not clear that these additional efforts
confuse potential observers any further, as they could monitor
only the network prefix part.

o The use and recommendations of various security services such as
IPsec or Transport Layer Security (TLS) [RFC5246] in the
connection of typical applications that also apply to cellular
hosts are discussed in Section 11 of [RFC6434].

o The airtime used by cellular hosts is expensive. In some cases,
users are billed according to the amount of data they transfer to
and from their host. It is crucial for both the network and the
users that the airtime is used correctly and no extra charges are
applied to users due to misbehaving third parties. The cellular
links also have a limited capacity, which means that they may not
necessarily be able to accommodate more traffic than what the user
selected, such as a multimedia call. Additional traffic might
interfere with the service level experienced by the user. While
Quality-of-Service mechanisms mitigate these problems to an
extent, it is still apparent that DoS aspects may be highlighted
in the cellular environment. It is possible for existing DoS
attacks that use, for instance, packet amplification, to be
substantially more damaging in this environment. How these
attacks can be protected against is still an area for further
study. It is also often easy to fill the cellular link and queues
on both sides with additional or large packets.

o Within some service provider networks, it is possible to buy a
prepaid cellular subscription without presenting personal
identification. Attackers that wish to remain unidentified could
leverage this. Note that while the user hasn't been identified,
the equipment still is; the operators can follow the identity of
the device and block it from further use. The operators must have
procedures in place to take notice of third party complaints
regarding the use of their customers' devices. It may also be
necessary for the operators to have attack detection tools that
enable them to efficiently detect attacks launched from the
cellular hosts.

o Cellular devices that have local network interfaces (such as WLAN
or Bluetooth) may be used to launch attacks through them, unless
the local interfaces are secured in an appropriate manner.
Therefore, local network interfaces should have access control to
prevent others from using the cellular host as an intermediary.

o The 3GPP link model mitigates most of the known IPv6 on-link and
neighbor cache targeted attacks (see Section 2.2 and Appendix A).

o Advice for implementations in the face of Neighbor Discovery DoS
attacks may be useful in some environments [RFC6583].

o Section 9 of [RFC6459] further discusses some recent concerns
related to the security of cellular hosts.

7. References

7.1. Normative References

[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.

[RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
for IPv6 Hosts and Routers", RFC 4213, October 2005.

[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.

[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.

[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.

[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, September 2007.

[RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
of Type 0 Routing Headers in IPv6", RFC 5095, December
2007.

[RFC5722] Krishnan, S., "Handling of Overlapping IPv6 Fragments",
RFC 5722, December 2009.

[RFC6434] Jankiewicz, E., Loughney, J., and T. Narten, "IPv6 Node
Requirements", RFC 6434, December 2011.

[RFC6980] Gont, F., "Security Implications of IPv6 Fragmentation
with IPv6 Neighbor Discovery", RFC 6980, August 2013.

7.2. Informative References

[RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51,
RFC 1661, July 1994.

[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.

[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.

[RFC3316] Arkko, J., Kuijpers, G., Soliman, H., Loughney, J., and J.
Wiljakka, "Internet Protocol Version 6 (IPv6) for Some
Second and Third Generation Cellular Hosts", RFC 3316,
April 2003.

[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.

[RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
Host Configuration Protocol (DHCP) version 6", RFC 3633,
December 2003.

[RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol
(DHCP) Service for IPv6", RFC 3736, April 2004.

[RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and
More-Specific Routes", RFC 4191, November 2005.

[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005.

[RFC5072] Varada, S., Haskins, D., and E. Allen, "IP Version 6 over
PPP", RFC 5072, September 2007.

[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.

[RFC5555] Soliman, H., "Mobile IPv6 Support for Dual Stack Hosts and
Routers", RFC 5555, June 2009.

[RFC6106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
"IPv6 Router Advertisement Options for DNS Configuration",
RFC 6106, November 2010.

[RFC6459] Korhonen, J., Soininen, J., Patil, B., Savolainen, T.,
Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation
Partnership Project (3GPP) Evolved Packet System (EPS)",
RFC 6459, January 2012.

[RFC6583] Gashinsky, I., Jaeggli, J., and W. Kumari, "Operational
Neighbor Discovery Problems", RFC 6583, March 2012.

[RFC6603] Korhonen, J., Savolainen, T., Krishnan, S., and O. Troan,
"Prefix Exclude Option for DHCPv6-based Prefix
Delegation", RFC 6603, May 2012.

[TS.23060]
3GPP, "General Packet Radio Service (GPRS); Service
description; Stage 2", 3GPP TS 23.060 11.5.0, March 2013.

[TS.23401]
3GPP, "General Packet Radio Service (GPRS) enhancements
for Evolved Universal Terrestrial Radio Access Network
(E-UTRAN) access", 3GPP TS 23.401 11.5.0, March 2013.

[TS.23402]
3GPP, "Architectural enhancements for non-3GPP accesses",
3GPP TS 23.402 11.6.0, March 2013.

[TS.29061]
3GPP, "Interworking between the Public Land Mobile Network
(PLMN) supporting packet based services and Packet Data
Networks (PDN)", 3GPP TS 29.061 11.4.0, March 2013.

Appendix A. Cellular Host IPv6 Addressing in the 3GPP Model

This appendix aims to very briefly describe the 3GPP IPv6 addressing
model for 2G (GPRS), 3G (UMTS), and 4G (EPS) cellular networks from
Release-99 onwards. More information for 2G and 3G can be found in
3GPP Technical Specifications [TS.23060] and [TS.29061]. The
equivalent documentation for 4G can be found in 3GPP Technical
Specifications [TS.23401], [TS.23402], and [TS.29061].

There are two possibilities to allocate the address for an IPv6 node:
stateless and stateful autoconfiguration. The stateful address
allocation mechanism needs a DHCP server to allocate the address for
the IPv6 node. On the other hand, the stateless autoconfiguration Stateless Address
Autoconfiguration procedure does not need any external entity
involved in the address autoconfiguration (apart from the GGSN/PGW).
At the time of writing this document, the IPv6 Stateless Address
Autoconfiguration mechanism is still the only mandatory and supported
address configuration method for the cellular 3GPP link.

In order to support the standard IPv6 Stateless Address
Autoconfiguration mechanism as recommended by the IETF, the GGSN/PGW
shall assign a single /64 IPv6 prefix that is unique within its scope
to each primary PDP Context or PDN Connection that uses IPv6
Stateless Address Autoconfiguration. This avoids the necessity to
perform Duplicate Address Detection (DAD) at the network level for
any address built by the mobile host. The GGSN/PGW always provides
an interface identifier to the mobile host. The mobile host uses the
interface identifier provided by the GGSN/PGW to generate its link-
local address. The GGSN/PGW provides the cellular host with the
interface identifier, usually in a random manner. It must ensure the
uniqueness of such an identifier on the link (i.e., no collisions
between its own link-local address and the cellular host's).

In addition, the GGSN/PGW will not use any of the prefixes assigned
to cellular hosts to generate any of its own addresses. This use of
the interface identifier, combined with the fact that each PDP
Context or PDN Connection is allocated a unique prefix, will
eliminate the need for DAD messages over the air interface and
consequently reduces inefficient use of radio resources.
Furthermore, the allocation of a prefix to each PDP Context or PDN
Connection will allow hosts to implement the Privacy Extensions in
[RFC4941] without the need for further DAD messages.

In practice, the GGSN/PGW only needs to route all traffic destined to
the cellular host that falls under the prefix assigned to it. This
implies the GGSN/PGW may implement a minimal Neighbor Discovery
protocol subset since, due to the point-to-point link model and the
absence of link-layer addressing, the address resolution can be
entirely statically configured per PDP Context or PDN Connection, and
there is no need to defend any addresses other than the link-local
addresses for very unlikely duplicates. This also has an additional
effect on a router to host router-to-host NUD. There is really no need for it, the NUD,
since from the point of view of GGSN/PGW, it GGSN/PGW does not need to
care for a single address but just routes the whole prefix to the
cellular host. However, the cellular host must be prepared for the
unlikely event of receiving a NUD against its link-local address. It
should be noted that the 3GPP specifications at the time of writing
this document are silent about what should happen if the router to router-to-
host NUD fails.

See Section 5 of [RFC6459] for further discussion on 3GPP address
allocation and the 3GPP link model.

Appendix B. Changes from RFC 3316

o Clarified that [RFC4941] or similar technologies instead of plain
[RFC4941] may be used for
privacy purposes (as stated in [RFC6459]).

o Clarified that MLD for link-local addresses is not necessary, but
doing it causes no harm (instead of saying it may not be needed in
some cases).

o Clarified that a cellular host should not do any changes in its
stack to meet the 3GPP link restriction on the Router
Advertisement Prefix Information Options (PIOs).

o Clarified that a cellular host should not do any changes in its
stack to meet the infinite prefix lifetime requirement the 3GPP
link has.

o Clarified that the prefix lifetime is tied to the PDP Context/PDN
Connection lifetime.

o Clarified explicitly that a NUD from the gateway side to the User
Equipment's link-local address is possible.

o Added references to 3GPP specifications.

o Provided additional clarification on NUD on 3GPP cellular links.

o Added an explicit note that the prefix on the link is /64.

o Clarified that DHCPv6 ([RFC3315]) is not used at all for address
autoconfiguration.

o Removed all sections that can be directly found in [RFC6434].

o Added clarifications to 3GPP link model and how Neighbor Discovery
works on it.

o Added [RFC4191] recommendations.

o Added DHCPv6-based Prefix Delegation recommendations.

o Added [RFC6106] recommendations.

o Added reference to [RFC5555] regarding client-based mobility.

o Added text regarding Router Advertisement MTU option handling.

o Added Evolved Packet System text.

o Added clarification on the primary 3GPP IPv6 transition mechanism.

o Added reference to [RFC5095], which deprecates the RH0.

o Added references to [RFC5722] and [RFC6980] regarding IPv6
fragmentation handling.

o Added reference to [RFC6583] for Neighbor Discovery denial-of-
service attack considerations.

o Made the PPP IPV6CP [RFC5072] support text conditional.

Authors' Addresses

Jouni Korhonen (editor)
Renesas Mobile
Broadcom
Porkkalankatu 24
FIN-00180 Helsinki
Finland

EMail: jouni.nospam@gmail.com

Jari Arkko (editor)
Ericsson
Jorvas 02420
Finland

EMail: jari.arkko@piuha.net
Teemu Savolainen
Nokia
Hermiankatu 12 D
FI-33720 Tampere
Finland

EMail: teemu.savolainen@nokia.com

Suresh Krishnan
Ericsson
8400 Decarie Blvd.
Town of Mount Royal, QC
Canada

Phone: +1 514 345 7900 x42871
EMail: suresh.krishnan@ericsson.com