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Versions: (draft-manyfolks-ipv6-cellular-host)
00 01 02 RFC 3316
INTERNET-DRAFT Jari Arkko
Internet Engineering Task Force Peter Hedman
Gerben Kuijpers
Hesham Soliman
Ericsson
John Loughney
Pertti Suomela
Juha Wiljakka
Nokia
Issued: April 10, 2002
Expires: October 10, 2002
IPv6 for Second and Third Generation Cellular Hosts
<draft-ietf-ipv6-cellular-host-01.txt>
Status of This Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as 'work in progress.'
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
As increasing numbers of cellular hosts are being connected to the
Internet, IPv6 becomes necessary. Examples of such hosts are devices
used with General Packet Radio Service (GPRS) or Universal Mobile
Telecommunications System (UMTS) networks. Standardization
organizations are also making IPv6 mandatory in their newest
specifications. However, the concept of IPv6 covers many aspects,
numerous standards, a number of different situations and is still
evolving. A rapid adoption of IPv6 is desired for cellular hosts. In
addition, the characteristics of cellular links in terms of
bandwidth, cost and delay put special requirements on IPv6. For
these reasons it is necessary to understand how the IPv6 deployment
in second and third generation cellular networks will start and
which parts of IPv6 are used in which situations. This informational
document lists basic components of IPv6 functionality and discusses
some issues relating to the use of these components when operating
over cellular interfaces.
Internet Draft IPv6 for 2G and 3G Cellular Hosts April 10, 2002
Abstract............................................................1
1 Introduction......................................................3
1.1 Scope of this Document.........................................3
1.2 Abbreviations..................................................4
1.4 Cellular Host IPv6 Features....................................5
2 Basic IP..........................................................5
2.1 RFC1981 - Path MTU Discovery for IP Version 6..................5
2.2 RFC2373 - IP Version 6 Addressing Architecture.................5
2.3 RFC2460 - Internet Protocol Version 6..........................6
2.4 RFC2461 - Neighbor Discovery for IPv6..........................6
2.5 RFC2462 - IPv6 Stateless Address Autoconfiguration.............7
2.6 RFC2463 - Internet Control Message Protocol for the IPv6.......7
2.7 RFC2472 - IP version 6 over PPP................................8
2.8 RFC2473 - Generic Packet Tunneling in IPv6 Specification.......8
2.9 RFC2710 - Multicast Listener Discovery (MLD) for IPv6..........8
2.10 RFC2711 - IPv6 Router Alert Option............................8
2.11 RFC2893 - Transition Mechanisms for IPv6 Hosts and Routers....8
2.12 RFC3041 - Privacy Extensions for Address Configuration in IPv68
2.13 RFC3056 - Connection of IPv6 Domains via IPv4 Clouds..........9
2.14 Dynamic Host Configuration Protocol for IPv6 (DHCPv6).........9
2.15 Default Address Selection for IPv6............................9
2.16 DNS...........................................................9
3 IP Security.......................................................9
3.1 RFC2104 - HMAC: Keyed-Hashing for Message Authentication......11
3.2 RFC2401 - Security Architecture for the Internet Protocol.....11
3.3 RFC2402 - IP Authentication Header............................11
3.4 RFC2403 - The Use of HMAC-MD5-96 within ESP and AH............11
3.5 RFC2404 - The Use of HMAC-SHA-96 within ESP and AH............11
3.6 RFC2405 - The ESP DES-CBC Cipher Algorithm With Explicit IV...11
3.7 RFC2406 - IP Encapsulating Security Payload (ESP).............11
3.8 RFC2407 - The Internet IP Security DoI for ISAKMP.............11
3.9 RFC2408 û Internet Security Association & Key Management Prot.12
3.10 RFC2409 - The Internet Key Exchange (IKE)....................12
3.11 RFC2410 - The NULL Encryption Algorithm & its Use With IPsec.12
3.12 RFC2451 - The ESP CBC-Mode Cipher Algorithms.................13
3.13 IP Security Remote Access....................................13
4 IP Mobility......................................................13
5 Security Considerations..........................................13
6 References.......................................................15
6.1 Normative.....................................................15
6.2 Non-Normative.................................................17
7 Acknowledgements.................................................18
8 Authors' Addresses...............................................18
Appendix A Revision History........................................19
Appendix B Cellular Host IPv6 Addressing in the 3GPP Model.........19
Appendix C Transition Issues.......................................20
Appendix D Mobility Issues.........................................21
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Internet Draft IPv6 for 2G and 3G Cellular Hosts April 10, 2002
1 Introduction
Technologies such as GPRS (General Packet Radio Service), UMTS
(Universal Mobile Telecommunications System), and CDMA2000 (Code
Division Multiple Access 2000, the name identifying the third
generation technology of IS-95 CDMA standard and ANSI-41 network)
are making it possible for cellular hosts to have an always-on
connection to the Internet. IPv6 becomes necessary, as it is
expected that the number of such cellular hosts will increase
rapidly. Standardization organizations working with cellular
technologies have recognized this and are making IPv6 mandatory in
their newest specifications. 3GPP (Third Generation Partnership
Project) has specified IPv6 support [3GPP-IPv6] as mandatory for
future UMTS IP multimedia hosts [3GPP-IMS].
Support for IPv6 and the introduction of UMTS starts with 3GPP
Release 99 networks and hosts. IPv6 is specified as the only IP
version supported in Release 5 for IP Multimedia Subsystem (IMS).
Additionally, there is interest within the IPv6 working group about
how IPv6 will be used by other organizations. For example, the
working group has developed Recommendations for IPv6 in 3GPP
Standards [IPv6-3GPP].
The functionality necessary to provide the connectivity through the
cellular interface is outlined in this draft. For this document, the
cellular interface is considered to be the interface that is used to
connect to a cellular access network (e.g. GPRS or UMTS) and
provides connectivity to IPv6 networks. The description is made from
a cellular host point of view.
1.1 Scope of this Document
This document lists IPv6 specifications and discusses some issues
relating to the use of these specifications when operating over
cellular interfaces. Such a specification is necessary in order to
determine the optimal way to use IPv6 in a cellular environment.
Important considerations are given in order to eliminate unnecessary
user confusion with regards to configuration options, ensure
interoperability and to provide an easy reference for those
implementing IPv6 in a cellular host. The overarching desire is to
ensure that cellular hosts are good citizens on the Internet.
The main audiences of this document are the implementers who need
guidance on what to implement in their cellular hosts, and cellular
standardization organizations that need a reference to how IPv6
should be used in their specifications. Note that, at the time of
writing this document, there is on-going work to define a general-
purpose requirements document for IPv6 nodes.
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Internet Draft IPv6 for 2G and 3G Cellular Hosts April 10, 2002
For the purposes of this document, a cellular host is considered to
be a host with a cellular interface (for example, one based on GPRS
or UMTS standards). There are different ways to implement cellular
hosts:
- The host can be a "closed 2G or 3G host" with a very compact
size and optimized 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.
- The host can be an "open 2G or 3G host" with a compact size,
but where it is possible to download applications; such as a
PDA-type of phone.
If a cellular host has additional interfaces on which IP is used,
(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 a PC card, other than
recommending link specific behavior on the cellular link.
This document discusses IPv6 functionality as specified when this
draft is written. Ongoing work on IPv6 may affect what is needed
from future hosts. The reader should also be advised other relevant
work exists for various other layers. Examples of this include the
header compression work done in the IETF ROHC group, or the TCP work
in [TCPWIRELESS].
1.2 Abbreviations
2G Second Generation Mobile Telecommunications, for example
GSM and GPRS technologies.
3G Third Generation Mobile Telecommunications, for example
UMTS technology.
3GPP Third Generation Partnership Project
AH Authentication Header
APN Access Point Name. The APN is a logical name referring
to a GGSN and an external network.
ESP Encapsulating Security Payload
ETSI European Telecommunications Standards Institute
IMS IP Multimedia Subsystem
GGSN Gateway GPRS Support Node (a default router for 3GPP
IPv6 cellular hosts)
GPRS General Packet Radio Service
GSM Global System for Mobile Communications
IKE Internet Key Exchange
ISAKMP Internet Security Association and Key Management
Protocol
MT Mobile Terminal, for example, a mobile phone handset.
MTU Maximum Transmission Unit
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Internet Draft IPv6 for 2G and 3G Cellular Hosts April 10, 2002
PDP Packet Data Protocol
SGSN Serving GPRS Support Node
TE Terminal Equipment, for example, a laptop attached
through a 3GPP handset.
UMTS Universal Mobile Telecommunications System
WLAN Wireless LAN
1.4 Cellular Host IPv6 Features
This specification defines IPv6 features for cellular hosts in three
groups.
Basic IP
In this group, we describe the basic parts of IPv6.
IP Security
In this group, we discuss IP Security parts, as well as
discuss the suitability of various security functions for
different applications in cellular hosts.
IP Mobility
In this group, we discuss IP layer mobility functionality,
and its usage scenarios in cellular hosts.
2 Basic IP
2.1 RFC1981 - Path MTU Discovery for IP Version 6
Path MTU Discovery [RFC-1981] may be used.
The IPv6 specification [RFC-2460] states in chapter 5 that "a
minimal IPv6 implementation (e.g., in a boot ROM) may simply
restrict itself to sending packets no larger than 1280 octets, and
omit implementation of Path MTU Discovery."
If Path MTU Discovery is not implemented then the sending packet
size is limited to 1280 octets (standard limit in [RFC-2460]).
However, if this is done, the cellular host must be able to receive
packets with size up to the link MTU before reassembly. This is
because the node at the other side of the link has no way of knowing
less than the MTU is accepted.
2.2 RFC2373 - IP Version 6 Addressing Architecture
The IPv6 Addressing Architecture [RFC-2373] is a mandatory part of
IPv6. IPX & NSAP addresses should not be used. Currently, this
standard is being updated by [ADDRARCHv3]; therefore, when this
draft is approved, this must be supported as well.
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2.3 RFC2460 - Internet Protocol Version 6
The Internet Protocol Version 6 is specified in [RFC-2460]. This
standard is a mandatory part of IPv6.
By definition, a cellular host acts as a host, not as a router.
Implementation requirements for a cellular router are not defined in
this document.
Consequently, the cellular host must implement all non-router packet
receive processing as described in RFC 2460. This includes the
generation of ICMPv6 error reports, and the processing of at least
the following extension headers:
- Hop-by-Hop Options header: at least the Pad1 and PadN options
- Destination Options header: at least the Pad1 and PadN options
- Routing (Type 0) header: final destination (host) processing
only
- Fragment header
- AH and ESP headers (see also a discussion on the use of IPsec
for various purposes in Section 3)
- The No Next Header value
Unrecognized options in Hop-by-Hop Options or Destination Options
extensions must be processed as described in RFC 2460.
The cellular host must follow the packet transmission rules in RFC
2460.
The cellular host must always be able to receive fragment headers.
However, if it does not implement path MTU (Section 2.1) it may not
need to send fragment headers.
Cellular Hosts will act as the destination when processing the
Routing Header. This will also ensure that the cellular hosts will
not be inappropriately used as relays or components in Denial-of-
Service attacks. Acting as the destination involves the following.
The cellular hosts must check the Segments Left field in the header,
and proceed if it is zero or one and the next address is one of the
host's addresses. If not, however, the host must implement error
checks as specified in section 4.4 of RFC 2460. There is no need for
the host to send Routing Headers.
2.4 RFC2461 - Neighbor Discovery for IPv6
Neighbor Discovery is described in [RFC-2461]. This standard is a
mandatory part of IPv6.
2.4.1 Neighbor Discovery in 3GPP
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In cellular networks, some Neighbor Discovery messages can cause
unnecessary traffic and consume valuable (limited) bandwidth. All
current cellular links resemble a point-to-point link; hence, the
host's only neighbor on the cellular link is the default router that
is already known through Router Discovery. This router most likely
will not be a final destination for the host's traffic.
Additionally, due to special characteristics of the cellular link,
lower layer connectivity information should make it unnecessary to
track the reachability of the router. Therefore, Neighbor
Solicitation and Advertisement messages may be used for the cellular
interface, but are not required. In addition, a cellular host should
not send the link layer sub-option on its cellular interface, and
should silently ignore it if received on the same interface.
3GPP hosts only need to use Router Solicitations and Router
Advertisements for 3GPP IPv6 Address Autoconfiguration. Neighbor
Solicitations and Advertisements may be used for Neighbor
Unreachability Detection (NUD). They are not required for 3GPP IPv6
Stateless Address Autoconfiguration, since address duplication is
not possible in this address assignment mechanism (see section
2.5.1).
2.5 RFC2462 - IPv6 Stateless Address Autoconfiguration
IPv6 Stateless Address Autoconfiguration is defined in [RFC-2462].
This standard is a mandatory part of IPv6.
2.5.1 Stateless Address Autoconfiguration in 3GPP
A 3GPP cellular host must process a Router Advertisement as stated
in chapter 5.5.3 of [RFC-2462].
These cellular hosts need not perform Duplicate Address Detection on
its cellular interface, as each delegated prefix is unique within
its scope when allocated using the 3GPP IPv6 Stateless Address
Autoconfiguration.
See appendix B for more details on 3GPP IPv6 Stateless Address
Autoconfiguration.
2.6 RFC2463 - Internet Control Message Protocol for the IPv6
The Internet Control Message Protocol for the IPv6 is defined [RFC-
2463]. This standard is a mandatory part of IPv6. Currently, this
work is being updated.
As per RFC 2463 section 2, ICMPv6 requirements must be fully
implemented by every IPv6 node. See also Section 3 for an
explanation of the use of IPsec for protecting ICMPv6
communications.
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2.7 RFC2472 - IP version 6 over PPP
IPv6 over PPP [RFC-2472] must be supported for cellular hosts that
implement PPP.
2.7.1 IP version 6 over PPP in 3GPP
A 3GPP cellular host must support the IPv6CP interface identifier
option. This option is needed to be able to connect other non-3GPP
devices to the Internet using a PPP link between the 3GPP device
(MT) 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 to be 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, 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 for its
link-local address.
2.8 RFC2473 - Generic Packet Tunneling in IPv6 Specification
Generic Packet Tunneling [RFC-2473] may be supported if needed for
transition mechanisms and must be supported if the Mobile Node
functionality of Mobile IP is implemented.
2.9 RFC2710 - Multicast Listener Discovery (MLD) for IPv6
Multicast Listener Discovery [RFC-2710] may be supported, if the
cellular host supports multicast functionality. There is no need for
MLD if the host supports only the well-known multicast addresses,
such as the All Nodes Address or Solicited Node Multicast Address.
2.10 RFC2711 - IPv6 Router Alert Option
The Router Alert Option [RFC-2711] may be supported. If the cellular
host does not perform packet forwarding at the IP layer, the
receiver side of the Router Alert Option may be omitted.
2.11 RFC2893 - Transition Mechanisms for IPv6 Hosts and Routers
[RFC-2893] specifies a number of transition mechanisms for IPv6 hosts.
Cellular hosts may support the dual stack mechanism mentioned in this
standard. This also includes resolving addresses from the DNS and
selecting the type of address for the correspondent host (IPv4 vs.
IPv6). Cellular hosts should not support configured or automatic
tunnels to avoid unnecessary tunneling over the air interface.
2.12 RFC3041 - Privacy Extensions for Address Configuration in IPv6
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Privacy Extensions for Stateless Address Autoconfiguration [RFC-
3041] may be used. Refer to section 5 for a discussion of the
benefits of privacy extensions in a 3GPP environment.
2.13 RFC3056 - Connection of IPv6 Domains via IPv4 Clouds
Connection of IPv6 domains via IPv4 clouds [RFC-3056] should not be
supported to avoid unnecessary tunneling over the air interface. For
a cellular host, this specification would mean capability to create
6to4 tunnels starting from the cellular host itself. In a cellular
environment, tunneling over the air interface should be minimized.
Hence, 6to4 tunneling should be carried out by intermediate 6to4
routers rather than the cellular host.
2.14 Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
The Dynamic Host Configuration Protocol for IPv6 [DHCPv6] may be
used. DHCPv6 is not needed when IPv6 stateless autoconfiguration is
used, and no other functions of DHCPv6 are used.
2.15 Default Address Selection for IPv6
Default Address Selection for IPv6 [DEFADDR] should be supported
since cellular hosts can have more than one IPv6 address.
2.16 DNS
Cellular hosts should support DNS, as described in [RFC-1034], [RFC-
1035] and [RFC-1886].
If DNS is used, a cellular host should perform DNS requests in the
recursive mode, to limit signaling over the air interface.
3 IP Security
IPsec [RFC-2401] is a fundamental part of IPv6, and support for AH
and ESP is described as mandatory in the standards.
The first part of this section discusses the applicability of IP
Security and other security mechanisms for certain types of common
tasks in cellular hosts. The second part, subsections 3.1 to 3.13,
lists the RFCs related to IPsec and discusses the use of these parts
of IPsec in a cellular context.
In general, the need to use a security mechanism depends on the
intended application for it. In order to gain an understanding on
where different security mechanisms are useful and what limitations
they have, we discuss a few example applications common in cellular
hosts: end-to-end VPNs, web browsing, and IPv6 control message
protection. We cannot list all possible services here, and in
general, we expect application protocol standards to have
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requirements on what security services they must employ. For new
applications, it is strongly suggested that some of the existing set
of security mechanisms be used rather than new ones developed,
adding to the amount of memory and implementation effort needed for
a host supporting multiple services. Note that cellular hosts able
to download applications must be prepared to offer sufficient
security services for these applications regardless of the needs of
the initial set of applications in those hosts.
Cellular hosts that provide an end-to-end VPN service to a corporate
intranet, for example, should use IPsec and IKE for this purpose. An
IPsec Remote Access solution should also be supported. The set of
standards necessary for such an "application" are discussed in
sections 3.1 to 3.13.
Note that in other applications it may not be necessary to use IKE.
For instance, hosts may use IPsec ESP [RFC-2406] for protecting SIP
signaling in the IMS [3GPP-ACC] but provide authentication and key
management through another mechanism such as UMTS AKA
(Authentication and Key Agreement) [UMTS-AKA].
Cellular hosts that provide a web browsing service should use TLS
[RFC-2246]. The fact that just TLS should be the protocol to provide
web security relates to current deployment and the suitability of
the single-side certificate trust model for this application.
Without security, the user would be blocked from some of the sites -
such as e-commerce sites - that do require security.
Cellular hosts may also wish to protect their IPv6 control
communications, e.g. ICMPv6 or Neighbor Discovery. IPsec is the
recommended approach for this purpose, and it works well towards a
specific home server, such as a corporate gateway. However, neither
IPsec nor other existing security services are very helpful in
securing communications to the local next hop routers (GGSNs) or
other 3GPP nodes in a global roaming situation. This is in part due
to the difficulties in establishing a suitable trust infrastructure
for creating the necessary Security Associations (SAs). In order for
a host to create a SA with the next hop router for the purposes of
securing the router and neighbor discovery tasks would mean the
following. First, both the routers and all cellular hosts would have
to be registered to a PKI system. Second, a trusted Certificate
Authority (CA) would have to be found that encompasses both the
visiting cellular host of an operator as well as the infrastructure
of another operator. It is not clear if this is possible with
today's technology. Furthermore, as [ICMPIKEv6] points out, dynamic
SA negotiation can't be used for the protection of the first few
connectivity establishment messages in ICMPv6. Roaming nodes may
have difficulty providing manually keyed SAs with their current
local routers. For these reasons, it is typically not possible to
provide pure IPv6 router and infrastructure protection except in a
very limited manner.
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The following sections list standards related to the IPsec
functionality, and discuss their applicability in a cellular
context. The latter discussion focuses on the use of IPsec as a VPN
mechanism towards a particular corporate network, and does not
necessarily apply to other usage scenarios; in some other context, a
different set of protocols may need to be employed. In particular,
the below discussion is not relevant for applications that use other
security services than IPsec.
3.1 RFC2104 - HMAC: Keyed-Hashing for Message Authentication
This standard [RFC-2104] must be supported. It is referenced by RFC
2403 that describes how IPsec protects the integrity of packets.
3.2 RFC2401 - Security Architecture for the Internet Protocol
This standard [RFC-2401] must be supported.
3.3 RFC2402 - IP Authentication Header
This standard [RFC-2402] must be supported. The IPsec WG has
discussed the role of AH in the future, and it is possible that it
will be made optional in the future versions of the IPsec protocol
set. Implementers are recommended to take this in account.
3.4 RFC2403 - The Use of HMAC-MD5-96 within ESP and AH
This standard [RFC-2403] must be supported.
3.5 RFC2404 - The Use of HMAC-SHA-96 within ESP and AH
This standard [RFC-2404] must be supported.
3.6 RFC2405 - The ESP DES-CBC Cipher Algorithm With Explicit IV
This standard [RFC-2405] may be supported. It is, however,
recommended that stronger algorithms than DES be used. Algorithms,
such as AES, are undergoing work in the IPsec working group.
3.7 RFC2406 - IP Encapsulating Security Payload (ESP)
This standard [RFC-2406] must be supported.
3.8 RFC2407 - The Internet IP Security DoI for ISAKMP
Automatic key management, [RFC-2408] and [RFC-2409], is not a
mandatory part of the IP Security Architecture. Note, however, that
in the cellular environment the IP addresses of a host may change
dynamically. For this reason the use of manually configured Security
Associations is not practical, as the newest host address would have
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to be updated to the SA database of the peer as well. Any key
management mechanism may be used, but ISAKMP/IKE is the standard one
and recommended here for the VPN service.
It is likely that several simplifying assumptions can be made in the
cellular environment, with respect to the mandated parts of the IP
Security DoI, ISAKMP, and IKE. Although work on such simplifications
would be useful, is not described here.
3.9 RFC2408 û Internet Security Association and Key Management Protocol
This standard [RFC-2408] may be supported according to the IPv6
standards, but may be necessary in some applications, as described
in Section 3.8.
3.10 RFC2409 - The Internet Key Exchange (IKE)
This standard [RFC-2409] may be supported according to the IPv6
standards, but may be necessary in some applications, as described
in Section 3.8.
Interactions with the ICMPv6 packets and IPsec policies may cause
unexpected behavior for IKE-based SA negotiation unless some special
handling is performed in the implementations.
The ICMPv6 protocol provides many functions, which in IPv4 were
either non-existent or provided by lower layers. For instance, IPv6
implements address resolution using an IP packet, ICMPv6 Neighbor
Solicitation message. In contrast, IPv4 uses an ARP message at a
lower layer.
The IPsec architecture has a Security Policy Database that specifies
which traffic is protected, and how. It turns out that the
specification of policies in the presence of ICMPv6 traffic is not
easy. For instance, a simple policy of protecting all traffic
between two hosts on the same network would trap even address
resolution messages, leading to a situation where IKE can't
establish a Security Association since in order to send the IKE UDP
packets one would have had to send the Neighbor Solicitation
Message, which would have required an SA.
In order to avoid this problem, this specification recommends that
Neighbor Solicitation, Neighbor Advertisement, Router Solicitation,
and Router Advertisement messages must not lead to the use of IKE-
based SA negotiation. The Redirect message should not lead to the
use of IKE-based SA negotiation. Other ICMPv6 messages may use IKE-
based SA negotiation as is desired in the Security Policy Data Base.
3.11 RFC2410 - The NULL Encryption Algorithm & its Use With IPsec
This standard [RFC-2410] must be supported.
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3.12 RFC2451 - The ESP CBC-Mode Cipher Algorithms
This standard [RFC-2451] must be supported if encryption algorithms
other than DES are implemented, e.g.: CAST-128, RC5, IDEA, Blowfish,
3DES.
3.13 IP Security Remote Access
IPsec is often used in situations where legacy RADIUS or other
authentication is desired instead of PKI-based authentication.
Cellular hosts offering DES services to corporate intranets should
support remote access solutions, which are currently being defined
by the IETF.
4 IP Mobility
Mobile IPv6 manages IP mobility resulting from the change in Care of
Address when a host moves within the Internet topology.
However, at the time this is being written Mobile IPv6 specification
is not yet a standard and may change. Some aspects of securing MIPv6
are also currently being debated. Yet, at the same time the first
cellular IPv6 hosts need to be produced. The implementers should
therefore consider the implications of relying on preliminary
information. Appendix D discusses certain functions that are
particularly prone to modifications, and describe the tradeoffs
involved.
5 Security Considerations
This document does not specify any new protocols or functionality,
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. In the following, we discuss both of
these issues:
- The suggested limitations (Section 2.3) in the processing of
routing headers limits also exposure to Denial-of-Service
attacks through cellular hosts.
- IPv6 addressing privacy [RFC3041] may be used in cellular
hosts. However, it should be noted that in the 3GPP model, the
network would assign new addresses, in most cases, to hosts in
roaming situations and typically, also when the cellular hosts
activate a PDP context. 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
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address. On the other hand, since a GGSN's coverage area is
expected to be very large when compared to currently deployed
default routers (no handovers between GGSNs are possible), a
cellular host can keep an address 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.
- The use of various security services such as IPsec or TLS in
the connection of typical applications in cellular hosts is
discussed in Chapter 3 and recommendations are given there.
- Chapter 3 also discusses under what conditions it is possible
to provide IPsec protection of e.g. ICMPv6 communications
- 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 QoS mechanisms mitigate these
problems to an extent, it is still apparent that Denial-of-
Service 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 of further study. It is also often easy to fill
the cellular link and queues on both sides with additional or
large packets.
- In certain areas of the world, it is possible to buy a prepaid
cellular subscription without presenting personal
identification. This could be leveraged by attackers that wish
to remain unidentified. We 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.
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- Cellular devices that have local network interfaces (such as
IrDA or Bluetooth) may be used to launch attacks through them,
unless the local interfaces are secured in an appropriate
manner. Therefore, we recommend that any local network
interface should have access controls to prevent by passers
from using the cellular host as an intermediary.
6 References
6.1 Normative
[ADDRARCHv3] Hinden, R. and Deering, S. "IP Version 6 Addressing
Architecture", Work in progress.
[DEFADDR] Draves, R., "Default Address Selection for IPv6",
Work in progress.
[DHCPv6] Bound, J. et al., "Dynamic Host Configuration
Protocol for IPv6 (DHCPv6)", Work in progress.
[RFC-1981] McCann, J., Mogul, J. and Deering, S., "Path MTU
Discovery for IP version 6", RFC 1981, August 1996.
[RFC-1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC-1886] Thomson, S. and Huitema, C., "DNS Extensions to
support IP version 6, RFC 1886, December 1995.
[RFC-2104] Krawczyk, K., Bellare, M., and Canetti, R., "HMAC:
Keyed-Hashing for Message Authentication", RFC 2104,
February 1997.
[RFC-2246] Dierks, T. and Allen, C., "The TLS Protocol Version
1.0", RFC 2246, January 1999
[RFC-2373] Hinden, R. and Deering, S., "IP Version 6 Addressing
Architecture", RFC 2373, July 1998.
[RFC-2401] Kent, S. and Atkinson, R., "Security Architecture for
the Internet Protocol", RFC 2401, November 1998.
[RFC-2402] Kent, S. and Atkinson, R., "IP Authentication
Header", RFC 2402, November 1998.
[RFC-2403] Madson, C., and Glenn, R., "The Use of HMAC-MD5
within ESP and AH", RFC 2403, November 1998.
[RFC-2404] Madson, C., and Glenn, R., "The Use of HMAC-SHA-1
within ESP and AH", RFC 2404, November 1998.
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[RFC-2405] Madson, C. and Doraswamy, N., "The ESP DES-CBC Cipher
Algorithm With Explicit IV", RFC 2405, November 1998.
[RFC-2406] Kent, S. and Atkinson, R., "IP Encapsulating Security
Protocol (ESP)", RFC 2406, November 1998.
[RFC-2407] Piper, D., "The Internet IP Security Domain of
Interpretation for ISAKMP", RFC 2407, November 1998.
[RFC-2408] Maughan, D., Schertler, M., Schneider, M., and
Turner, J., "Internet Security Association and Key
Management Protocol (ISAKMP)", RFC 2408, November
1998.
[RFC-2409] Harkins, D., and Carrel, D., "The Internet Key
Exchange (IKE)", RFC 2409, November 1998.
[RFC-2410] Glenn, R. and Kent, S., "The NULL Encryption
Algorithm and Its Use With IPsec", RFC 2410, November
1998
[RFC-2451] Pereira, R. and Adams, R., "The ESP CBC-Mode Cipher
Algorithms", RFC 2451, November 1998
[RFC-2460] Deering, S. and Hinden, R., "Internet Protocol,
Version 6 (IPv6) Specification", RFC 2460, December
1998.
[RFC-2461] Narten, T., Nordmark, E. and Simpson, W., "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461,
December 1998.
[RFC-2462] Thomson, S. and Narten, T., "IPv6 Stateless Address
Autoconfiguration", RFC 2462.
[RFC-2463] Conta, A. and Deering, S., "ICMP for the Internet
Protocol Version 6 (IPv6)", RFC 2463, December 1998.
[RFC-2473] Conta, A. and Deering, S., "Generic Packet Tunneling
in IPv6 Specification", RFC 2473, December 1998.
[RFC-2710] Deering, S., Fenner, W. and Haberman, B., "Multicast
Listener Discovery (MLD) for IPv6", RFC 2710, October
1999.
[RFC-2711] Partridge, C. and Jackson, A., "IPv6 Router Alert
Option", RFC 2711, October 1999.
[RFC-2874] Crawford, M. and Huitema, C., "DNS Extensions to
Support IPv6 Address Aggregation and Renumbering",
RFC 2874, July 2000.
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[RFC-3041] Narten, T. and Draves, R., "Privacy Extensions for
Stateless Address Autoconfiguration in IPv6", RFC
3041, January 2001.
6.2 Non-Normative
[3GPP-ACC] 3GPP Technical Specification 3GPP TS 33.203,
"Technical Specification Group Services and System
Aspects; 3G Security; Access security for IP-based
services (Release 5)", 3rd Generation Partnership
Project, March 2002.
[3GPP-IMS] 3rd Generation Partnership Project; Technical
Specification Group Services and System Aspects; IP
Multimedia (IM) Subsystem - Stage 2; (3G TS 23.228)
[3GPP-IPv6] 3rd Generation Partnership Project; Technical
Specification Group Services and System Aspects
"Architectural requirements" (TS 23.221)
[ICMPIKEv6] Arkko, J., "Effects of ICMPv6 on IKE and IPsec
Policies", Expired Internet Draft, Available at
http://www.arkko.com/publications/draft-arkko-icmpv6-
ike-effects-00.txt.
[IPv6-3GPP] Wasserman, M (editor), "Recommendations for IPv6 in
3GPP Standards" Work in Progress.
[MIPv6] Johnson D. and Perkins, C., "Mobility Support in
IPv6", Work in progress.
[RFC-1034] Mockapetris, P., "Domain names û concepts and
facilities", RFC 1034, November 1987
[RFC-2529] Carpenter, B. and Jung, C., "Transmission of IPv6
over IPv4 Domains without Explicit Tunnels", RFC
2529, March 1999.
[RFC-2893] Gilligan, R. and Nordmark, E., "Transition Mechanisms
for IPv6 Hosts and Routers", RFC 2893, August 2000.
[RFC-3056] Carpenter, B. and Moore, K., "Connection of IPv6
domains via IPv4 clouds", RFC 3056, February 2001.
[TCPWIRELESS] Inamura, H. et al. "TCP over 2.5G and 3G Networks".
IETF, Work in progress.
[UMTS-AKA] 3GPP Technical Specification 3GPP TS 33.102,
"Technical Specification Group Services and System
Aspects; 3G Security; Security Architecture (Release
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4)", 3rd Generation Partnership Project, December
2001.
7 Acknowledgements
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 at the IPv6 WG mailing
list for their comments and input.
We would also like to thank David DeCamp, Karim El Malki, Markus
Isomki, Petter Johnsen, Janne Rinne, Jonne Soininen, Vlad Stirbu
and Shabnam Sultana for their comments and input in preparation of
this document.
8 Authors' Addresses
Jari Arkko
Ericsson
02420 Jorvas
Finland
Phone: +358 40 5079256
Fax: +358 40 2993401
E-Mail: Jari.Arkko@ericsson.com
Peter Hedman
Ericsson
SE-221 83 LUND
SWEDEN
Phone: +46 46 231760
Fax: +46 46 231650
E-mail: peter.hedman@emp.ericsson.se
Gerben Kuijpers
Ericsson
Skanderborgvej 232
DK-8260 Viby J
DENMARK
Phone: +45 89385100
Fax: +45 89385101
E-mail: gerben.a.kuijpers@ted.ericsson.se
Hesham Soliman
Ericsson Radio Systems AB
Torshamnsgatan 23, Kista, Stockholm
SWEDEN
Phone: +46 8 4046619
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Fax: +46 8 4047020
E-mail: Hesham.Soliman@era.ericsson.se
John Loughney
Nokia Research Center
Itmerenkatu 11 û 13
FIN-00180 HELSINKI
FINLAND
Phone: +358 7180 36242
Fax: +358 7180 36851
E-mail: john.loughney@nokia.com
Pertti Suomela
Nokia Mobile Phones
Visiokatu 3
FIN-33720 TAMPERE
Finland
Phone: +358 7180 40546
Fax: +358 7180 48381
E-mail: pertti.suomela@nokia.com
Juha Wiljakka
Nokia Mobile Phones
Visiokatu 3
FIN-33720 TAMPERE
Finland
Phone: +358 7180 47562
Fax: +358 7180 48381
E-mail: juha.wiljakka@nokia.com
Appendix A Revision History
Changes from draft-ietf-ipv6-cellular-host-00.txt:
- Introduction edited
- 1.1 on scoping added
- keywords removed
- DNS discovery removed
- some more to be added here.
Appendix B Cellular Host IPv6 Addressing in the 3GPP Model
The appendix aims to very briefly describe the 3GPP IPv6 addressing
model for 2G (GPRS) and 3G (UMTS) cellular networks from Release 99
onwards. More information can be found from 3GPP Technical
Specification 23.060.
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There are two possibilities to allocate the address for an IPv6 node
û 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
procedure does not need any external entity involved in the address
autoconfiguration (apart from the GGSN).
In order to support the standard IPv6 stateless address
autoconfiguration mechanism, as defined by the IETF, the GGSN shall
assign a prefix that is unique within its scope to each primary PDP
context that uses IPv6 stateless address autoconfiguration. This
avoids the necessity to perform Duplicate Address Detection at the
network level for every address built by the mobile host. The GGSN
always provides an Interface Identifier to the mobile host. The
Mobile host uses the interface identifier provided by the GGSN to
generate its link-local address. Since the GGSN provides the
cellular host with the interface identifier, it must ensure the
uniqueness of such identifier on the link (I.e. no collisions
between its own link local address and the cellular host's).
In addition, the GGSN 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 is allocated a unique prefix, will eliminate the
need for DAD messages over the air interface, and consequently
allows an efficient use of bandwidth. Furthermore, the allocation of
a prefix to each PDP context will allow hosts to implement the
privacy extensions in RFC 3041 without the need for further DAD
messages.
Appendix C Transition Issues
IETF has specified a number of IPv4 / IPv6 transition mechanisms
[RFC-2893] to ensure smooth transition from IPv4 to IPv6 and
interoperability between IPv4 and IPv6 during the transition period.
The three main transition methods from a cellular network point of
view are dual IPv4 / IPv6 stacks, tunneling and protocol
translators, such as NAT-PT or SIIT.
It is recommended that cellular hosts have dual IPv4 / IPv6 stacks
to be able to interoperate with both IPv4 and IPv6 domains and use
both IPv6 and IPv4 applications / services. It is recommended that
most transition mechanisms be provided by the network in order to
save the limited resources of the cellular host. Tunneling (for
example RFC 3056 - Connection of IPv6 Domains via IPv4 Clouds)
should be carried out in the network. In addition, any protocol
translation function, such as NAT-PT, should be implemented in the
network, not in the cellular host.
The tunneling mechanism specified by [RFC-2529] is not relevant for
a cellular host. [RFC-2529] allows isolated IPv6-only hosts to
connect to an IPv6 router via an IPv4 domain. The scenario of an
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IPv6-only host in an IPv4-only cellular network is considered
unlikely.
Appendix D Mobility Issues
This appendix discusses the level of support of MIPv6 required by
cellular hosts and highlight the scenarios in which such support is
needed. Mobile IPv6 is specified in [MIPv6].
Mobile IP is required for hosts moving within the Internet topology.
At the highest level, the Mobile IPv6 functionality within Mobile
Nodes can be divided to the following parts:
- Correspondent Node (CN) functionality, defined by Mobile IPv6
specification [MIPv6], i.e. the basic functionality needed to
correspond with mobile nodes.
- Mobile Node (MN) functionality [MIPv6]. This includes the
ability to configure Home and Care-of-Addresses (CoA) send
Binding Updates (BUs) and receive Binding Acknowledgements and
Requests. In addition, this function also includes the ability
to maintain a Binding Update List.
- Route optimization. The functionality needed to correspond with
mobile nodes in an optimal manner.
We will discuss the use of each part in turn.
The basic functionality of a Correspondent Node, i.e. process the
Home Address Option, must be supported by all hosts. However, at the
time this is being written, the Home Address Option is defined only
in preliminary form in [MIPv6]. Furthermore, at present it is
unclear whether this option can be understood by all nodes or only
in conjunction with Route Optimization. This is due to the possible
use of the option in Denial-of-Service attacks that employ CNs as
reflectors. Cellular host implementers are advised that leaving out
Home Address Option support may prevent their hosts to communicate
with future MIPv6 MNs. On the other hand, the inclusion of Home
Address Option without Route Optimization being active for that host
may present a threat that allows the cellular hosts to be used as
reflectors in Denial-of-Service attacks.
The mobile node functionality is needed when the host itself will
move within the Internet topology i.e. changes its care-of address.
This function is needed in cellular systems where MIPv6 is used for
intra-access technology mobility. In other cellular systems where
intra-access technology mobility is handled by other means (e.g. GTP
in a 3GPP system), hosts with additional, non-cellular interfaces
must have this functionality if they need to retain session or IP
layer reachability while moving between different access
technologies, i.e. - to use MIPv6 for inter-system IP handovers.
For instance, when a hosts has both a Wireless LAN (WLAN) and an
UMTS interface, MIPv6 MN functionality is needed to retain sessions
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when moving from UMTS area to a WLAN area. The UMTS network provides
a basic mobility service (layer 2 mobility) to all hosts without
requiring the implementation of IP layer mobility. Hosts that have
interfaces only to networks providing such other mobility services,
or hosts that do not require session mobility through interface
handovers may have this functionality for reachability when the DNS
is used to locate a host. That is, when roaming between different
cellular operators. A host, in this case, would require a home
address in the DNS and a Home agent. When connected to a default
router for the host, the host would update its Home Agent with its
new address.
Mobile node functionality is fully defined in the Mobile IPv6
specifications and should only be implemented according to an
official standard.
The Route Optimization functionality for a CN, i.e. processing of
Binding Updates, should be supported by all hosts supporting the
Mobile Node functions and may be supported by all hosts.
Route Optimization functionality should also only be implemented
according to an official standard.
Hosts that implement MIPv6 must support the security features
defined in [MIPv6]. Note that MNs, CNs, and Route Optimization
functionality may have different requirements.
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