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Dual-Stack Lite Broadband Deployments Following IPv4 Exhaustion
RFC 6333

Internet Engineering Task Force (IETF)                         A. Durand
Request for Comments: 6333                              Juniper Networks
Category: Standards Track                                       R. Droms
ISSN: 2070-1721                                                    Cisco
                                                             J. Woodyatt
                                                                   Apple
                                                                  Y. Lee
                                                                 Comcast
                                                             August 2011

    Dual-Stack Lite Broadband Deployments Following IPv4 Exhaustion

Abstract

   This document revisits the dual-stack model and introduces the Dual-
   Stack Lite technology aimed at better aligning the costs and benefits
   of deploying IPv6 in service provider networks.  Dual-Stack Lite
   enables a broadband service provider to share IPv4 addresses among
   customers by combining two well-known technologies: IP in IP (IPv4-
   in-IPv6) and Network Address Translation (NAT).

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6333.

Durand, et al.               Standards Track                    [Page 1]
RFC 6333                     Dual-Stack Lite                 August 2011

Copyright Notice

   Copyright (c) 2011 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.

Table of Contents

   1. Introduction ....................................................3
   2. Requirements Language ...........................................4
   3. Terminology .....................................................4
   4. Deployment Scenarios ............................................4
      4.1. Access Model ...............................................4
      4.2. CPE ........................................................5
      4.3. Directly Connected Device ..................................6
   5. B4 Element ......................................................7
      5.1. Definition .................................................7
      5.2. Encapsulation ..............................................7
      5.3. Fragmentation and Reassembly ...............................7
      5.4. AFTR Discovery .............................................7
      5.5. DNS ........................................................8
      5.6. Interface Initialization ...................................8
      5.7. Well-Known IPv4 Address ....................................8
   6. AFTR Element ....................................................9
      6.1. Definition .................................................9
      6.2. Encapsulation ..............................................9
      6.3. Fragmentation and Reassembly ...............................9
      6.4. DNS .......................................................10
      6.5. Well-Known IPv4 Address ...................................10
      6.6. Extended Binding Table ....................................10
   7. Network Considerations .........................................10
      7.1. Tunneling .................................................10
      7.2. Multicast Considerations ..................................10
   8. NAT Considerations .............................................11
      8.1. NAT Pool ..................................................11
      8.2. NAT Conformance ...........................................11
      8.3. Application Level Gateways (ALGs) .........................11
      8.4. Sharing Global IPv4 Addresses .............................11
      8.5. Port Forwarding / Keep Alive ..............................11

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