V6OPS Working Group                                             C. Byrne
Internet-Draft                                              T-Mobile USA
Intended Status: Informational                                  D. Drown
Expires: November 18, 2013 January 15, 2014                                      A. Vizdal
                                                     Deutsche Telekom AG
                                                            May 17,
                                                           July 14, 2013

Extending an IPv6 /64 Prefix from a 3GPP Mobile Interface to a LAN
                      draft-ietf-v6ops-64share-07 link
                      draft-ietf-v6ops-64share-08

Abstract

   This document describes three two methods for extending an IPv6 /64 prefix
   from a User Equipment 3GPP radio interface to a LAN. LAN link.

Status of this Memo

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   This Internet-Draft will expire on November 18, 2013.

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V6OPS Working Group   draft-ietf-v6ops-64share-07           May 17, 2013

Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2. The Challenge of Providing IPv6 Addresses to a LAN link via a
      3GPP UE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3. Methods for Extending the 3GPP Interface /64 IPv6 Prefix to a
      LAN . . . link  . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.0
     3.1 General Behavior for All Scenarios . . . . . . . . . . . . .  4
     3.1 Scenario 1: No Global Address on the UE  . . . . . . . . . .  4
     3.2 Scenario 2: 1: Global Address Only Assigned to LAN link . . . . . .  5  4
     3.3 Scenario 3: 2: A Single Global Address Assigned to 3GPP Radio
         and LAN Interface link . . . . . . . . . . . . . . . . . . . . .  6 . . .  5
   4. Security Considerations . . . . . . . . . . . . . . . . . . . .  7  6
   5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  7  6
   6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . .  7  6
   7. Informative References  . . . . . . . . . . . . . . . . . . . .  7

V6OPS Working Group   draft-ietf-v6ops-64share-07           May 17, 2013

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. single LAN
   link.  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. LAN link.  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 link with RA.  For all of the cases in the
   scope of this document, the UE may be any device that functions as an
   IPv6 router between the 3GPP network and a LAN.

   This document describes three two methods for achieving IPv6 prefix
   extension from a 3GPP radio interface to a LAN link 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) link
   2) The 3GPP UE maintains the same consistent 128 bit global scope
      IPv6 anycast address [RFC4291] on the 3GPP radio interface and the
      LAN interface. link.  The LAN interface link 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 two
   approaches.

2. The Challenge of Providing IPv6 Addresses to a LAN link 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, LAN link, 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. LAN link.  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 be used
   prior to DHCPv6 deployment.

V6OPS Working Group   draft-ietf-v6ops-64share-07           May 17, 2013

3. Methods for Extending the 3GPP Interface /64 IPv6 Prefix to a LAN

3.0
   link

3.1 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 link RA configuration must be tightly coupled
   with the 3GPP interface link state.  If the 3GPP interface link goes down or changes the
   IPv6 prefix, that state should be reflected in the LAN link IPv6
   configuration.  Just as in a standard IPv6 router, the packet TTL
   will be decremented when passing packets between
   interfaces IPv6 links across
   the UE.  The UE is employing the weak host model. The RA function on
   the UE is exclusively run on the LAN interface.

3.1 link.

   The LAN link originated RA message carries a copy of the following
   3GPP radio link received RA message option fields:

   o  MTU (if not provided by the 3GPP network, the UE will provide its
      3GPP link MTU size)
   o  Prefix Information

3.2 Scenario 1: No Global Address on the UE

   In Only Assigned to LAN link

   For this case, the UE receives the /64 RA from the 3GPP network via 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 simply configures Neighbor Discovery Protocol (NDP) [RFC4861] assigns
   itself an address on the LAN interface link.  The LAN link uses RA to announce
   the /64 via RA.  The UE forwards all
   traffic destine prefix to the /64 out of the LAN.  The UE LAN interface. link 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.
   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.

V6OPS Working Group   draft-ietf-v6ops-64share-07           May 17, 2013

   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

   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
   link may result in long-lived data connections being terminated
   during the transition from a host-only mode to router-and-host mode.
   Connections which are likely to be effected are ones that have been
   specifically bound to the 3GPP radio interface.  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.

V6OPS Working Group   draft-ietf-v6ops-64share-07           May 17, 2013

   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 link 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 link interface, there is no chance of address conflict
       since the address is defended using DAD.  The 3GPP radio
       interface only has a link-local addresses. address.

3.3 Scenario 3: 2: A Single Global Address Assigned to 3GPP Radio and LAN
   Interface
   link

   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 link as a /128 and on the LAN
   interface link
   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]. When Privacy Extensions should
   are in use all temporary addresses will be disabled on copied from the 3GPP radio
   interface while this
   method is enabled. to the LAN link and the preferred and valid lifetimes will
   be synchronized, such that the temporary anycast addresses on both
   interfaces expire simultaneously.

   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:

V6OPS Working Group   draft-ietf-v6ops-64share-07           May 17, 2013

   1.  The user activates router functionality for a LAN on the UE.

   2.  The UE checks to make sure the 3GPP interfaces 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 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.

   tbd

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 Lorenzo Colitti, Julien Laganier. Laganier and Owen DeLong.

7. Informative References

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

V6OPS Working Group   draft-ietf-v6ops-64share-07           May 17, 2013
              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 Ales.Vizdal@T-Mobile.cz