Abstract
This document lists a set of IPv6-related requirements to be
supported by cellular hosts.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Connectivity Requirements . . . . . . . . . . . . . . . . . . 3
2.1. WiFi Connectivity . . . . . . . . . . . . . . . . . . . . 7
3. Advanced Requirements . . . . . . . . . . . . . . . . . . . . 8
4. Cellular Devices with LAN Capabilities . . . . . . . . . . . . 9
5. APIs & Applications . . . . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . . 13
Authors . . . . . . . . . . . . . . . . . . . . . . . . 15
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1. Introduction
[RFC3316] lists a set of features to be supported by cellular hosts
to connect to 3GPP cellular networks. Since the publication of that
document, new functions have been specified within the 3GPP and the
IETF whilst others have been updated. Moreover, in the light of
recent IPv6 production deployments, additional features to facilitate
IPv6-only deployments while accessing IPv4-only service are to be
considered.
A detailed overview of IPv6 support in 3GPP architectures is provided
in [RFC6459].
This document makes use of the terms defined in [RFC6459].
PREFIX64 denotes an IPv6 prefix used to build IPv4-converted IPv6
addresses [RFC6052].
1.1. Scope
Various types of nodes can be connected to 3GPP networks requiring
specific functions. Indeed, a 3GPP network can be used to connect
user equipment such as a mobile telephone, a CPE or a machine-to-
machine (M2M) device. 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 network. This document describes these
functionalities.
This document is structured to initially provide the generic IPv6
requirements which are valid for all nodes, whatever their function
or service (e.g., SIP [RFC3261]) capability. The document also
contains, dedicated sections covering specific functionalities the
specific device types must support (e.g., smartphones, devices
providing some LAN functions (mobile CPE or broadband dongles)).
M2M devices profile is not considered in the first version of this
document.
The requirements listed below are valid for both 3GPP GPRS and 3GPP
EPS access. For EPS, "PDN type" terminology is used instead of "PDP
context".
2. Connectivity Requirements
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REQ#1: The cellular host MUST support the IPv6 addressing
architecture described in ([RFC4291]). For address
representation, [RFC5952] MUST be supported.
REQ#2: The cellular host MUST support both IPv6 and IPv4v6 PDP
Contexts.
This allows each operator to select their own strategy
regarding IPv6 introduction. Both IPv6 and IPv4v6 PDP
contexts MUST be supported in addition to the IPv4 PDP
context. IPv4, IPv6 or IPv4v6 PDP-Context request
acceptance depends on the mobile network configuration.
REQ#3: The cellular host MUST comply with the behavior defined in
[TS.23060] [TS.23401] [TS.24008] for requesting a PDP context
type. In particular, the cellular host MUST request an IPv6 PDP
context if the cellular host is IPv6-only and requesting 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., cellular host with LAN
capabilities):
* 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
and/or an IPv6 prefix by the network. It MAY initiate
another PDP request in addition to the one already
activated for a given APN.
* If the requested PDP type and subscription data 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 text above focuses on the specification part which explains
the behavior for requesting IPv6-related PDP context(s).
Understanding this behavior is important to avoid having broken
IPv6 implementations in cellular devices.
REQ#4: The cellular host MUST support the PCO (Protocol
Configuration Options) [TS.24008] to retrieve the IPv6
address(es) of the Recursive DNS server(s).
In-band signaling is a convenient method to inform the
cellular host about various services, including DNS server
information. It does not require any specific protocol to
be supported and it is already deployed in IPv4 cellular
networks to convey such DNS information.
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REQ#5: The cellular host MUST support IPv6 aware Traffic Flow
Templates (TFT) [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
mobile network for certain IP traffic.
REQ#6: The cellular host MUST support ICMPv6 ([RFC4443]).
The base protocol MUST be fully implemented by every IPv6
node as indicated in Section 2 of [RFC4443].
REQ#7: The device MUST support the Neighbor Discovery Protocol
([RFC4861] and [RFC5942]).
In particular, MTU communication via Router Advertisement
SHOULD be supported since many 3GPP networks do not have a
standard MTU setting due to inconsistencies in GTP
[RFC3314] mobility tunnel infrastructure deployments.
REQ#8: The cellular host MUST support IPv6 Stateless Address
Autoconfiguration ([RFC4862]) apart from the exceptions noted in
[TS.23060] (3G) and [TS.23401] (LTE):
Stateless mode is the only way to configure a cellular
host. The GGSN must allocate a prefix that is unique
within its scope to each primary PDP context.
The cellular host MUST use the interface identifier sent in
PDP Context Accept message to configure its link local
address. The cellular host may use a different Interface
Identifiers to configure its global addresses.
REQ#9: The cellular host SHOULD support Router Advertisement Options
[RFC6106] for DNS configuration.
The support of this function allows for a consistent method
of informing cellular hosts about DNS recursive servers
across various types of access networks. The cellular host
SHOULD support RA-based DNS information discovery.
REQ#10: The cellular host SHOULD embed a DHCPv6 client [RFC3736].
Stateless DHCPv6 is useful to retrieve other information
than DNS.
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If [RFC6106] is not supported, the cellular host SHOULD
retrieve DNS information using stateless DHCPv6 [RFC3736].
If the cellular host receives the DNS information in
several channels for the same interface, the following
preference order MUST be followed:
1. PCO
2. RA
3. DHCPv6
REQ#11: The cellular host SHOULD support a method to locally
construct IPv4-embedded IPv6 addresses [RFC6052]. A method to
learn PREFIX64 SHOULD be supported by the cellular host.
This solves the issue when applications use IPv4 referrals
on IPv6-only access networks.
The cellular host SHOULD implement the method specified in
[I-D.ietf-behave-nat64-discovery-heuristic] to retrieve the
PREFIX64.
REQ#12: The cellular host SHOULD implement the Customer Side
Translator function (CLAT, [I-D.ietf-v6ops-464xlat]) function
which is compliant with [RFC6052][RFC6145][RFC6146].
CLAT function in the cellular host allows for IPv4-only
application and IPv4-referals to work on an IPv6-only PDP.
CLAT function requires a NAT64 capability [RFC6146] in the
core network.
REQ#13: The cellular device SHOULD embed a DNS64 function [RFC6147].
Local DNS64 functionality allows for compatibility with
DNSSEC. Means to configure or discover a PREFIX64 is also
required on the cellular device.
REQ#14: The cellular host SHOULD support PCP [I-D.ietf-pcp-base].
The support of PCP is seen as a driver to save battery
consumption exacerbated by keepalive messages. PCP also
gives the possibility of enabling incoming connections to
the user. Indeed, because several stateful devices may be
deployed in mobile networks (e.g., NAT and/or Firewalls),
PCP can be used by the cellular host to control network
based NAT and Firewall functions which will reduce per-
application signaling and save battery consumption.
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REQ#15: When the cellular host is dual stack connected, it SHOULD
support means to prefer native IPv6 connection over connection
established through translation devices (e.g., NAT44 and NAT64).
Cellular hosts SHOULD follow the procedure specified in
[RFC6724] for source address selection.
Some potential issues are discussed in
[I-D.ietf-mif-happy-eyeballs-extension] for MIFed devices.
REQ#16: The cellular host SHOULD support Happy Eyeballs procedure
defined in [RFC6555].
REQ#17: The cellular host SHOULD NOT perform Duplicate Address
Detection (DAD) for these Global IPv6 addresses (as the GGSN or
PDN-GW must not configure any IPv6 addresses using the prefix
allocated to the cellular host). Refer to Section 4 for DAD
considerations on the LAN interface when the 3GPP connection is
shared.
REQ#18: The cellular device MAY embed a BIH function [RFC6535]
facilitating the communication between an IPv4 application and
an IPv6 server.
2.1. WiFi Connectivity
It is increasingly common for cellular hosts have a Wi-Fi interface
in addition to their cellular interface. These hosts are likely to
be connected to private or public hotspots. Below are listed some
generic requirements:
REQ#19: IPv6 MUST be supported on the Wi-Fi interface. In
particular, IPv6-only connectivity MUST be supported over the
Wi-Fi interface.
Recent tests revealed that IPv4 configuration is
required to enable IPv6-only connectivity. Indeed,
some cellular handsets can access a Wi-Fi IPv6-only
network by configuring first a static IPv4 address.
Once the device is connected to the network and the
wlan0 interface got an IPv6 global address, the IPv4
address can be deleted from the configuration. This
avoids the device to ask automatically for a DHCPv4
server, and allows to connect to IPv6-only networks.
IPv6 Stateless Address Autoconfiguration ([RFC4862])
MUST be supported.
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REQ#20: DHCPv6 client SHOULD be supported on Wi-Fi interface
([RFC3736]).
REQ#21: Wi-Fi interface SHOULD support Router Advertisement Options
for DNS configuration ([RFC6106]). If the device receives the
DNS information in several channels for the same interface,
the following preference order MUST be followed:
1. RA
2. DHCPv6
3. Advanced Requirements
REQ#22: The cellular host MUST support Path MTU discovery
([RFC1981]). If the MTU used by cellular hosts is larger than
1280 bytes, they can rely on Path MTU discovery function to
discover the real path MTU.
REQ#23: The cellular host SHOULD support the Privacy Extensions for
Stateless Address Autoconfiguration in IPv6 ([RFC4941]).
The activation of privacy extension makes it more
difficult to track a host over time when compared to
using a permanent interface identifier. [RFC4941] does
not require any DAD mechanism to be activated as the
GGSN (or PDN-GW) MUST NOT configure any global address
based on the prefix allocated to the cellular host.
REQ#24: The cellular host SHOULD support ROHC for IPv6 ([RFC5795]).
Bandwidth in mobile environments 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.
REQ#25: The cellular host SHOULD support IPv6 Router Advertisement
Flags Options ([RFC5175]).
Some flags are used by the GGSN (or PDN-GW) to inform
cellular hosts about the autoconfiguration process.
REQ#26: The cellular host SHOULD support Router Advertisement
extension for communicating default router preferences and
more-specific routes as described in [RFC4191].
This function can be used for instance for traffic
offload.
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4. Cellular Devices with LAN Capabilities
This section focuses on cellular devices (e.g., CPE, smartphones or
dongles with tethering features) which provide IP connectivity to
other devices connected to them. In such case, all connected devices
are sharing the same GPRS, UMTS or EPS connection. In addition to
the generic requirements listed in Section 2, these cellular devices
have to meet the requirements listed below.
REQ#27: The cellular device MUST support Prefix Delegation
capabilities [RFC3633] and MUST support Prefix Exclude Option
for DHCPv6-based Prefix Delegation as defined in [RFC6603].
Particularly, it MUST behave as a Requesting Router.
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 shorter prefix than
/64 to cellular hosts so that each LAN segment can get
its own /64 prefix and multilink 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
prefixes:
(1) one for 3GPP link allocated using SLAAC
mechanism and
(2) another one delegated for LANs acquired
during 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/PDN-GW) will have to ensure [RFC3633]
compliancy (e.g., halving the Delegated prefix and
assigning the WAN prefix out of the 1st half and the
prefix to be delegated to the terminal from the 2nd
half).
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REQ#28: The cellular device MUST be compliant with the CPE
requirements specified in [RFC6204].
REQ#29: Prefix delegation which allows to allocate a shorter prefix
to a cellular host is only available since 3GPP Release 10.
For deployments requiring to share the same /64 prefix, the
cellular device SHOULD support [I-D.ietf-v6ops-64share] to
enable sharing a /64 prefix between the 3GPP interface towards
the GGSN (WAN interface) and the LAN interfaces.
REQ#30: The cellular device SHOULD support the Customer Side
Translator (CLAT) [I-D.ietf-v6ops-464xlat].
Various IP devices are likely to be connected to
cellular device, acting as a CPE. Some of these
devices can be dual-stack, others are IPv6-only or
IPv4-only. IPv6-only connectivity for cellular device
does not allow IPv4-only sessions to be established for
hosts connected on the LAN segment of cellular devices.
In order to allow IPv4 sessions establishment initiated
from devices located on LAN segment side and target
IPv4 nodes, a solution consists in integrating the CLAT
function in the cellular device. As elaborated in
Section 2, the CLAT function allows also IPv4
applications to continue running over an IPv6-only
host.
REQ#31: If a RA MTU is advertised from the 3GPP network, the
cellular device SHOULD relay that upstream MTU information to
the downstream attached LAN devices in RA.
Since 3GPP networks extensively use IP-in-IP/UDP GTP
tunnels, the effective MTU is frequently effectively
reduced to 1440 bytes. While a host may generate
packets with an MTU of 1500 bytes, this results in
undesirable fragmentation of the GTP IP/UDP packets.
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 GTP tunnels.
5. APIs & Applications
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REQ#32: Name resolution libraries MUST support both IPv4 and IPv6.
In particular, the cellular host MUST support
[RFC3596].
REQ#33: Applications MUST be independent of the underlying IP
address family.
This means applications must be IP version agnostic.
REQ#34: Applications using URIs MUST follow [RFC3986]. For example,
SIP applications MUST follow the correction defined in
[RFC5954].
6. Security Considerations
The security considerations identified in [RFC3316] are to be taken
into account.
REQ#35: If the cellular device provides LAN features, it SHOULD be
compliant with the security requirements specified in
[RFC6092].
7. IANA Considerations
This document does not require any action from IANA.
8. Acknowledgements
Many thanks to H. Soliman, H. Singh, L. Colliti, T. Lemon, B.
Sarikaya, J. Korhonen, M. Mawatari, M. Abrahamsson, P. Vickers and V.
Kuarsingh for the discussion in the v6ops mailing list.
9. References
9.1. Normative References
[RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
for IP version 6", RFC 1981, August 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
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A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi,
"DNS Extensions to Support IP Version 6", RFC 3596,
October 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.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and
More-Specific Routes", RFC 4191, November 2005.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control
Message Protocol (ICMPv6) for the Internet Protocol
Version 6 (IPv6) Specification", RFC 4443, March 2006.
[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.
[RFC5175] Haberman, B. and R. Hinden, "IPv6 Router Advertisement
Flags Option", RFC 5175, March 2008.
[RFC5795] Sandlund, K., Pelletier, G., and L-E. Jonsson, "The RObust
Header Compression (ROHC) Framework", RFC 5795,
March 2010.
[RFC5942] Singh, H., Beebee, W., and E. Nordmark, "IPv6 Subnet
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Model: The Relationship between Links and Subnet
Prefixes", RFC 5942, July 2010.
[RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952, August 2010.
[RFC5954] Gurbani, V., Carpenter, B., and B. Tate, "Essential
Correction for IPv6 ABNF and URI Comparison in RFC 3261",
RFC 5954, August 2010.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
October 2010.
[RFC6106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
"IPv6 Router Advertisement Options for DNS Configuration",
RFC 6106, November 2010.
[RFC6145] Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
Algorithm", RFC 6145, April 2011.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, April 2011.
[RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van
Beijnum, "DNS64: DNS Extensions for Network Address
Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
April 2011.
[RFC6535] Huang, B., Deng, H., and T. Savolainen, "Dual-Stack Hosts
Using "Bump-in-the-Host" (BIH)", RFC 6535, February 2012.
[RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
Dual-Stack Hosts", RFC 6555, April 2012.
[RFC6603] Korhonen, J., Savolainen, T., Krishnan, S., and O. Troan,
"Prefix Exclude Option for DHCPv6-based Prefix
Delegation", RFC 6603, May 2012.
[RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown,
"Default Address Selection for Internet Protocol Version 6
(IPv6)", RFC 6724, September 2012.
9.2. Informative References
[I-D.ietf-behave-nat64-discovery-heuristic]
Savolainen, T., Korhonen, J., and D. Wing, "Discovery of
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the IPv6 Prefix Used for IPv6 Address Synthesis",
draft-ietf-behave-nat64-discovery-heuristic-12 (work in
progress), November 2012.
[I-D.ietf-mif-happy-eyeballs-extension]
Chen, G., Williams, C., Wing, D., and A. Yourtchenko,
"Happy Eyeballs Extension for Multiple Interfaces",
draft-ietf-mif-happy-eyeballs-extension-01 (work in
progress), October 2012.
[I-D.ietf-pcp-base]
Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
Selkirk, "Port Control Protocol (PCP)",
draft-ietf-pcp-base-29 (work in progress), November 2012.
[I-D.ietf-v6ops-464xlat]
Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT:
Combination of Stateful and Stateless Translation",
draft-ietf-v6ops-464xlat-08 (work in progress),
September 2012.
[RFC3314] Wasserman, M., "Recommendations for IPv6 in Third
Generation Partnership Project (3GPP) Standards",
RFC 3314, September 2002.
[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.
[RFC6092] Woodyatt, J., "Recommended Simple Security Capabilities in
Customer Premises Equipment (CPE) for Providing
Residential IPv6 Internet Service", RFC 6092,
January 2011.
[RFC6204] Singh, H., Beebee, W., Donley, C., Stark, B., and O.
Troan, "Basic Requirements for IPv6 Customer Edge
Routers", RFC 6204, April 2011.
[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.
[TS.23060]
3GPP, "General Packet Radio Service (GPRS); Service
description; Stage 2", September 2011.
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[TS.23401]
3GPP, "General Packet Radio Service (GPRS) enhancements
for Evolved Universal Terrestrial Radio Access Network
(E-UTRAN) access", September 2011.
[TS.24008]
3GPP, "Mobile radio interface Layer 3 specification; Core
network protocols; Stage 3", June 2011.
Authors'
David Binet
France Telecom
Mohamed Boucadair
France Telecom
Ales Vizdal
Deutsche Telekom AG
Cameron Byrne
T-Mobile
USA
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Gang Chen
China Mobile
Additional Source: Internet Engineering Task Force
