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Versions: (draft-byrne-v6ops-64share) 00 01 04 05 06 07 08 09 10 02 RFC 7278

V6OPS Working Group                                             C. Byrne
Internet-Draft                                              T-Mobile USA
Intended Status: Informational                                  D. Drown
Expires: August 12, 2013                                February 8, 2013


  Extending an IPv6 /64 Prefix from a 3GPP Mobile Interface to a LAN
                      draft-ietf-v6ops-64share-02


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
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   This Internet-Draft will expire on August 12, 2013.

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   Copyright (c) 2013 IETF Trust and the persons identified as the
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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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
     3.0 General Behavior for All Scenarios . . . . . . . . . . . . .  3
     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 advertise the same IPv6 prefix to the LAN with RA.

   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.

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



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   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 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.  The UE
   cannot originate or terminate any global scope packets in this case
   since it does not have a global scope IPv6 address to source or
   receive packets. 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 effectively
   an IPv6 router that does not require any global connectivity.  Lack
   of connectivity will prevent proper Path MTU Discovery [RFC1981]


   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.

   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 IPv6
       Stateless Address Autoconfiguration [RFC4862] feature for global



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       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.

   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 IPv6
       SLAAC feature on the 3GPP radio interface to avoid address



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       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 destine 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.  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.

   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 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



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       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 destine 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 3.2 does not allow for Privacy Extension to run 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 Sylvain Decremps, Mark
   Smith, Dmitry Anipko, Masanobu Kawashima, Teemu Savolainen, Mikael
   Abrahamsson, Eric Vyncke, Alexandru Petrescu, Jouni Korhonen, Julien
   Laganier, and Ales Vizdal.

7. Informative References

   [RFC1981]  McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
              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,



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              "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


























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