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Versions: (draft-byrne-v6ops-64share) 00 01
04 05 06 07 08 09 10 RFC 7278
V6OPS Working Group C. Byrne
Internet-Draft T-Mobile USA
Intended Status: Informational D. Drown
Expires: November 18, 2013 A. Vizdal
Deutsche Telekom AG
May 17, 2013
Extending an IPv6 /64 Prefix from a 3GPP Mobile Interface to a LAN
draft-ietf-v6ops-64share-06
Abstract
This document describes three methods for extending an IPv6 /64
prefix from a User Equipment 3GPP radio interface to a LAN.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 18, 2013.
Copyright and License Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. The Challenge of Providing IPv6 Addresses to a LAN via a 3GPP
UE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Methods for Extending the 3GPP Interface /64 IPv6 Prefix to a
LAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.0 General Behavior for All Scenarios . . . . . . . . . . . . . 4
3.1 Scenario 1: No Global Address on the UE . . . . . . . . . . 4
3.2 Scenario 2: Global Address Only Assigned to LAN . . . . . . 5
3.3 Scenario 3: A Single Global Address Assigned to 3GPP Radio
and LAN Interface . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Informative References . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
3GPP mobile cellular networks such as GSM, UMTS, and LTE have
architectural support for IPv6 [RFC6459], but only 3GPP Release-10
and onwards of the 3GPP specification supports DHCPv6 Prefix
Delegation [RFC3633] for delegating IPv6 prefixes to a LAN. To
facilitate the use of IPv6 in a LAN prior to the deployment of DHCPv6
Prefix Delegation in 3GPP networks and in User Equipment (UE), this
document describes how the 3GPP UE radio interface assigned global
/64 prefix may be extended from the 3GPP radio interface to a LAN.
This is achieved by receiving the Router Advertisement (RA) [RFC4861]
announced globally unique /64 IPv6 prefix from the 3GPP radio
interface and then advertising the same IPv6 prefix to the LAN with
RA. For all of the cases in the scope of this document, the UE may
be any device that function as an IPv6 router between the 3GPP
network and a LAN.
This document describes three methods for achieving IPv6 prefix
extension from a 3GPP radio interface to a LAN including:
1) The 3GPP UE does not have a global scope IPv6 address on any
interface, only link-local IPv6 addresses are present on the UE
2) The 3GPP UE only has a global scope address on the LAN interface
3) The 3GPP UE maintains the same consistent 128 bit global scope
IPv6 anycast address [RFC4291] on the 3GPP radio interface and the
LAN interface. The LAN interface is configured as a /64 and the
3GPP radio interface is configured as a /128.
Section 3 describes the characteristics of each of the three
approaches.
2. The Challenge of Providing IPv6 Addresses to a LAN via a 3GPP UE
As described in [RFC6459], 3GPP networks assign a /64 global scope
prefix to each UE using RA. DHCPv6 Prefix Delegation is an optional
part of 3GPP Release-10 and is not covered by any earlier releases.
Neighbor Discovery Proxy (ND Proxy) [RFC4389] functionality has been
suggested as an option for extending the assigned /64 from the 3GPP
radio interface to the LAN, but ND Proxy is an experimental protocol
and has some limitations with loop-avoidance.
DHCPv6 is the best way to delegate a prefix to a LAN. The methods
described in this document should only be applied when deploying
DHCPv6 Prefix Delegation is not achievable in the 3GPP network and
the UE. The methods described in this document are at various stages
of implementation and deployment planning. The goal of this memo is
to document the available methods which may used prior to DHCPv6
deployment.
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3. Methods for Extending the 3GPP Interface /64 IPv6 Prefix to a LAN
3.0 General Behavior for All Scenarios
As [RFC6459] describes, the 3GPP network assigned /64 is completely
dedicated to the UE and the gateway does not consume any of the /64
addresses. The gateway routes the entire /64 to the UE and does not
perform ND or Network Unreachability Detection (NUD) [RFC4861].
Communication between the UE and the gateway is only done using link-
local addresses and the link is point-to-point. This allows for the
UE to reliably manipulate the /64 from the 3GPP radio interface
without negatively impacting the point-to-point 3GPP radio link
interface. The LAN interface RA configuration must be tightly
coupled with the 3GPP interface state. If the 3GPP interface goes
down or changes the IPv6 prefix, that state should be reflected in
the LAN IPv6 configuration. Just as in a standard IPv6 router, the
packet TTL will be decremented when passing packets between
interfaces across the UE. The RA function on the UE is exclusively
run on the LAN interface.
3.1 Scenario 1: No Global Address on the UE
In this case, the UE receives the /64 from the 3GPP network via RA
and simply configures Neighbor Discovery Protocol (NDP) [RFC4861] on
the LAN interface to announce the /64 via RA. The UE forwards all
traffic destine to the /64 out of the LAN interface. The UE shall
not run Stateless Address Autoconfiguration [RFC4862] to assign a
global address on the 3GPP radio interface while routing is enabled.
The 3GPP UE does not assign itself any global IPv6 addresses. Lack
of global scope connectivity will limit network services running on
the UE (e.g. DNS caching that requires global connectivity) and
prevent proper Path MTU Discovery [RFC1981] to occur on the UE
providing an IPv6 router function. The LAN attached devices have
complete access to the /64, but the 3GPP UE only has link-local
addresses.
This method is appropriate for a use-case where the UE is only an
IPv6 router that does not require any global connectivity.
Below is the general procedure for this scenario:
1. The user activates router functionality for a LAN on the UE.
2. The UE checks to make sure the 3GPP interface is active and has
an IPv6 address. If the interface does not have an IPv6 address,
an attempt will be made to acquire one, or else the procedure
will terminate.
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3. In this example, the UE finds the 3GPP interface has the IPv6
address 2001:db8:ac10:f002:1234:4567:0:9/64 assigned and active.
4. The UE copies the prefix 2001:db8:ac10:f002::/64 from the 3GPP
interface to the LAN interface, removes the global IPv6 address
configuration from the 3GPP radio interface, disables the IPv6
Stateless Address Autoconfiguration (SLAAC) [RFC4862] feature for
global addresses on the 3GPP radio interface to avoid address
autoconfiguration, and begins announcing the global prefix
2001:db8:ac10:f002::/64 via RA to the LAN. The 3GPP interface
and LAN interface only maintain link-local addresses while the UE
uses RA to announce the /64 to the LAN.
5. Since the UE and gateway do not assign any of the addresses from
the /64, there is no chance of an address conflict on the 3GPP
radio interface. On the LAN interface, there is no chance of an
address conflict since the hosts on the LAN will use Duplicate
Address Detection (DAD) [RFC4862].
3.2 Scenario 2: Global Address Only Assigned to LAN
For this case, the UE receives the RA from the 3GPP network but does
not use a global address on the 3GPP interface. The 3GPP RA /64
prefix information is used to configure NDP on the LAN and assigns
itself an address on the LAN link. The LAN interface uses RA to
announce the prefix to the LAN. The UE LAN interface defends its LAN
IPv6 address with DAD. The UE shall not run Stateless Address
Autoconfiguration [RFC4862] to assign a global address on the 3GPP
radio interface while routing is enabled.
This method allows the UE to originate and terminate IPv6
communications as a host while acting as an IPv6 router. The
movement of the IPv6 prefix from the 3GPP radio interface to the LAN
interface may result in long-lived data connections being terminated
during the transition from a host-only mode to router-and-host mode.
This method is appropriate if the UE or software on the UE cannot
support multiple interfaces with the same anycast IPv6 address and
the UE requires global connectivity while acting as a router.
Below is the general procedure for this scenario:
1. The user activates router functionality for a LAN on the UE.
2. The UE checks to make sure the 3GPP interface is active and has
an IPv6 address. If the interface does not have an IPv6 address,
an attempt will be made to acquire one, or else the procedure
will terminate.
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3. In this example, the UE finds the 3GPP interface has the IPv6
address 2001:db8:ac10:f002:1234:4567:0:9 assigned and active.
4. The UE moves the address 2001:db8:ac10:f002:1234:4567:0:9 as a
/64 from the 3GPP interfaces to the LAN interface, disables the
IPv6 SLAAC feature on the 3GPP radio interface to avoid address
autoconfiguration, and begins announcing the prefix
2001:db8:ac10:f002::/64 via RA to the LAN. For this example, the
LAN has 2001:db8:ac10:f002:1234:4567:0:9/64 and the 3GPP radio
only has a link-local address.
5. The UE directly processes all packets destined to itself at
2001:db8:ac10:f002:1234:4567:0:9.
6. The UE, acting as a router running NDP on the LAN, will route
packets to and from the LAN. IPv6 packets passing between
interfaces will have the TTL decremented.
7. On the LAN interface, there is no chance of address conflict
since the address is defended using DAD. The 3GPP radio
interface only has link-local addresses.
3.3 Scenario 3: A Single Global Address Assigned to 3GPP Radio and LAN
Interface
In this method, the UE assigns itself one address from the 3GPP
network RA announced /64. This one address is configured as anycast
[RFC4291] on both the 3GPP radio interface as a /128 and on the LAN
interface as a /64. This allows the UE to maintain long lived data
connections since the 3GPP radio interface address does not change
when the router function is activated. This method may cause
complications for certain software that may not support multiple
interfaces with the same anycast IPv6 address or are sensitive to
prefix length changes. This method also creates complications for
ensuring uniqueness for Privacy Extensions [RFC4941]. Privacy
Extensions should be disabled on the 3GPP radio interface while this
method is enabled.
There might also be more complex scenarios in which the prefix length
is not changed and privacy extensions are supported by having the
subnet span multiple interfaces, as ND Proxy does [RFC4389]. Further
elaboration is out of scope of the present document.
Below is the general procedure for this scenario:
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1. The user activates router functionality for a LAN on the UE.
2. The UE checks to make sure the 3GPP interfaces is active and has
an IPv6 address. If the interface does not have an IPv6 address,
an attempt will be made to acquire one, or else the procedure
will terminate.
3. In this example, the UE finds the 3GPP interface has the IPv6
address 2001:db8:ac10:f002:1234:4567:0:9 assigned and active.
4. The UE moves the address 2001:db8:ac10:f002:1234:4567:0:9 as an
anycast /64 from the 3GPP interface to the LAN interface and
begins announcing the prefix 2001:db8:ac10:f002::/64 via RA to
the LAN. The 3GPP interface maintains the same IPv6 anycast
address with a /128. For this example, the LAN has
2001:db8:ac10:f002:1234:4567:0:9/64 and the 3GPP radio interface
has 2001:db8:ac10:f002:1234:4567:0:9/128.
5. The UE directly processes all packets destined to itself at
2001:db8:ac10:f002:1234:4567:0:9.
6. On the LAN interface, there is no chance of address conflict
since the address is defended using DAD. The 3GPP radio
interface only has a /128 and no other systems on the 3GPP radio
point-to-point link may use the global /64.
4. Security Considerations
Since Scenario 3.3 does not allow for Privacy Extension to run on the
3GPP interface, UEs that require this functionality must find an
alternative method or only associate the IPv6 Privacy Extension
procedure on the LAN.
5. IANA Considerations
This document does not require any action from IANA.
6. Acknowledgments
Many thanks for review and discussion from Dave Thaler, Sylvain
Decremps, Mark Smith, Dmitry Anipko, Masanobu Kawashima, Teemu
Savolainen, Mikael Abrahamsson, Eric Vyncke, Alexandru Petrescu,
Jouni Korhonen, and Julien Laganier.
7. Informative References
[RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
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for IP version 6", RFC 1981, August 1996.
[RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
Host Configuration Protocol (DHCP) version 6", RFC 3633,
December 2003.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery
Proxies (ND Proxy)", RFC 4389, April 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.
[RFC6459] Korhonen, J., Ed., 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.
Authors' Addresses
Cameron Byrne
T-Mobile USA
Bellevue, Washington, USA
EMail: Cameron.Byrne@T-Mobile.com
Dan Drown
Email: Dan@Drown.org
Ales Vizdal
Deutsche Telekom AG
Tomickova 2144/1
Prague, 149 00
Czech Republic
EMail: Ales.Vizdal@t-mobile.cz
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