Sharing /64 3GPP Mobile Interface Subnet to a LAN
draft-byrne-v6ops-64share-00

V6OPS Working Group                                             C. Byrne
Internet-Draft                                              T-Mobile USA
Intended Status: Informational                                 Dan Drown
Expires: April 1, 2013                                September 28, 2012

           Sharing /64 3GPP Mobile Interface Subnet to a LAN 
                      draft-byrne-v6ops-64share-00

Abstract

   This document describes a known and implemented method of sharing a
   /64 IPv6 subnet from a 3GPP interface to a tethered 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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on April 1, 2013.

Copyright and License Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.
 

Byrne                    Expires April 1, 2013                  [Page 1]
V6OPS Working Group   draft-byrne-v6ops-64share-00    September 28, 2012

Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2. The Challenge of Providing IPv6 Addresses to a 3GPP Tethered 
      LAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3. Method for Sharing the 3GPP Interface /64 to the Tethered LAN .  3
   4. Security Considerations . . . . . . . . . . . . . . . . . . . .  4
   5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  4
   6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . .  4
   7. Informative References  . . . . . . . . . . . . . . . . . . . .  4

 

Byrne                    Expires April 1, 2013                  [Page 2]
V6OPS Working Group   draft-byrne-v6ops-64share-00    September 28, 2012

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 standard supports DHCPv6 [RFC3633] for
   delegating IPv6 addresses to a tethered LAN.  To facilitate the use
   of IPv6 in a tethered LAN prior to deployment of DHCPv6 in a 3GPP
   network, this document describes how the 3GPP User Equipment (UE)
   interface assigned /64 subnet may be shared from the 3GPP interface
   to a tethered LAN.  This is achieved by specifying the 3GPP interface
   as an IPv6 /128 subnet taken from the 3GPP interface's network
   assigned /64 subnet.  Then, assign the same address to the tethered
   LAN interface with the full /64 subnet.  The /64 tethered LAN subnet
   will then be advertised to the tethered LAN via Router Advertisements
   (RA) [RFC4861].  

   The end result is that all interfaces have link-local IPv6 addresses,
   the 3GPP interface has a /128 address from the 3GPP network assigned
   /64, and the same address that is assigned to the 3GPP interface is
   assigned to the tethered LAN interface with a /64 subnet and
   advertised to the LAN via RA.

2. The Challenge of Providing IPv6 Addresses to a 3GPP Tethered LAN

   As described in [RFC6459], 3GPP networks assigns a /64 subnet to the
   UE with RA.  IPv6 prefix delegation is a 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
   sharing the assigned /64 from the 3GPP interface to the LAN, but ND
   Proxy is an experimental protocol and has some limitations with loop-
   avoidance and other complexities that prevent it from being broadly
   applied.

   DHCPv6 is the best way to assign subnets to tethered LANs.  The
   method described in this document should only be applied when
   deploying DHCPv6 is not achievable in the 3GPP network.

3. Method for Sharing the 3GPP Interface /64 to the Tethered LAN

   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.  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 use the 3GPP network assigned /64 to assign
   itself a /128 subnet address to the 3GPP interface for consistent
   network reachability and the same address with a /64 subnet to the
   tethered LAN interface.  The tethered LAN interface may then
 

Byrne                    Expires April 1, 2013                  [Page 3]
V6OPS Working Group   draft-byrne-v6ops-64share-00    September 28, 2012

   advertise the /64 subnet to the LAN with RA.

   For example, if the 3GPP network assigns to the UE via RA the subnet
   2001:0DB8:AC10:F002::/64, the UE may choose the address for its 3GPP
   interface to be 2001:DB80:AC10:F002:1234:4567::9/128.  When tethering
   a LAN, the UE may then assign that same address to its LAN with a /64
   subnet, such as 2001:DB80:AC10:F002:1234:4567::9/64.  The UE may then
   advertise the 2001:DB80:AC10:F002::/64 subnet to the tethered LAN
   using RA.  Since the UE only consumes one address from the 3GPP
   network assigned /64 for both the 3GPP interface and the LAN
   interface, there is no address conflict potential.  On the LAN, the
   /64 subnet is announced via RA and the interface address is defended
   with Duplicate Address Detection (DAD) [RFC4862].  Since the 3GPP
   interface is a point-to-point link and the gateway does not consume
   an address from the network assigned /64, there is no chance of
   conflict on the 3GPP interface for the /64.

   For completeness, while tethering a LAN the UE should provide
   [RFC6204] LAN-Side configuration support. Additionally, it may be
   beneficial to advertise the MTU of 1440 bytes via RA to the LAN to
   avoid fragmentation within the 3GPP network infrastructure.

4. Security Considerations

   The LAN features may be compliant with security requirements
   specified in [RFC6092]

5. IANA Considerations

   This document does not require any action from IANA.

6. Acknowledgments TBD

7. Informative References

   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              December 2003.

   [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.

 

Byrne                    Expires April 1, 2013                  [Page 4]
V6OPS Working Group   draft-byrne-v6ops-64share-00    September 28, 2012

   [RFC6092]  Woodyatt, J., Ed., "Recommended Simple Security
              Capabilities in Customer Premises Equipment (CPE) for
              Providing Residential IPv6 Internet Service", RFC 6092,
              January 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.

   Authors' Addresses

   Cameron Byrne
   T-Mobile USA
   Bellevue, Washington, USA

   EMail: Cameron.Byrne@T-Mobile.com

   Dan Drown
   Email: Dan@Drown.org

Byrne                    Expires April 1, 2013                  [Page 5]