Internet Engineering Task Force (IETF)
Request for Comments: 6204
Category: Informational
ISSN: 2070-1721
H. Singh
W. Beebee
Cisco Systems, Inc.
C. Donley
B. Stark
O. Troan, Ed.
Cisco Systems, Inc.
April 2011

Basic Requirements for IPv6 Customer Edge Routers


This document specifies requirements for an IPv6 Customer Edge (CE) router. Specifically, the current version of this document focuses on the basic provisioning of an IPv6 CE router and the provisioning of IPv6 hosts attached to it.

Status of This Memo

This document is not an Internet Standards Track specification; it is published for informational purposes.

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). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see 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

Copyright Notice

Copyright © 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 ( 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 ....................................................2
      1.1. Requirements Language ......................................3
   2. Terminology .....................................................3
   3. Architecture ....................................................4
      3.1. Current IPv4 End-User Network Architecture .................4
      3.2. IPv6 End-User Network Architecture .........................4
           3.2.1. Local Communication .................................6
   4. Requirements ....................................................6
      4.1. General Requirements .......................................6
      4.2. WAN-Side Configuration .....................................7
      4.3. LAN-Side Configuration ....................................11
      4.4. Security Considerations ...................................13
   5. Acknowledgements ...............................................13
   6. Contributors ...................................................14
   7. References .....................................................14
      7.1. Normative References ......................................14
      7.2. Informative References ....................................16

1. Introduction

This document defines basic IPv6 features for a residential or small- office router, referred to as an IPv6 CE router. Typically, these routers also support IPv4.

Mixed environments of dual-stack hosts and IPv6-only hosts (behind the CE router) can be more complex if the IPv6-only devices are using a translator to access IPv4 servers [RFC6144]. Support for such mixed environments is not in scope of this document.

This document specifies how an IPv6 CE router automatically provisions its WAN interface, acquires address space for provisioning of its LAN interfaces, and fetches other configuration information from the service provider network. Automatic provisioning of more complex topology than a single router with multiple LAN interfaces is out of scope for this document.

See [RFC4779] for a discussion of options available for deploying IPv6 in service provider access networks.

1.1. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].

2. Terminology

   End-User Network          one or more links attached to the IPv6 CE
                             router that connect IPv6 hosts.

IPv6 Customer Edge Router a node intended for home or small-office

use that forwards IPv6 packets not explicitly addressed to itself. The IPv6 CE router connects the end-user network to a service provider network.

   IPv6 Host                 any device implementing an IPv6 stack
                             receiving IPv6 connectivity through the
                             IPv6 CE router.
   LAN Interface             an IPv6 CE router's attachment to a link in
                             the end-user network.  Examples are
                             Ethernets (simple or bridged), 802.11
                             wireless, or other LAN technologies.  An
                             IPv6 CE router may have one or more
                             network-layer LAN interfaces.
   Service Provider          an entity that provides access to the
                             Internet.  In this document, a service
                             provider specifically offers Internet
                             access using IPv6, and may also offer IPv4
                             Internet access.  The service provider can
                             provide such access over a variety of
                             different transport methods such as DSL,
                             cable, wireless, and others.
   WAN Interface             an IPv6 CE router's attachment to a link
                             used to provide connectivity to the service
                             provider network; example link technologies
                             include Ethernets (simple or bridged), PPP
                             links, Frame Relay, or ATM networks, as
                             well as Internet-layer (or higher-layer)
                             "tunnels", such as tunnels over IPv4 or
                             IPv6 itself.

3. Architecture

3.1. Current IPv4 End-User Network Architecture

An end-user network will likely support both IPv4 and IPv6. It is not expected that an end-user will change their existing network topology with the introduction of IPv6. There are some differences in how IPv6 works and is provisioned; these differences have implications for the network architecture. A typical IPv4 end-user network consists of a "plug and play" router with NAT functionality and a single link behind it, connected to the service provider network.

A typical IPv4 NAT deployment by default blocks all incoming connections. Opening of ports is typically allowed using a Universal Plug and Play Internet Gateway Device (UPnP IGD) [UPnP-IGD] or some other firewall control protocol.

Another consequence of using private address space in the end-user network is that it provides stable addressing; i.e., it never changes even when you change service providers, and the addresses are always there even when the WAN interface is down or the customer edge router has not yet been provisioned.

Rewriting addresses on the edge of the network also allows for some rudimentary multihoming, even though using NATs for multihoming does not preserve connections during a fail-over event [RFC4864].

Many existing routers support dynamic routing, and advanced end-users can build arbitrary, complex networks using manual configuration of address prefixes combined with a dynamic routing protocol.

3.2. IPv6 End-User Network Architecture

The end-user network architecture for IPv6 should provide equivalent or better capabilities and functionality than the current IPv4 architecture.

The end-user network is a stub network. Figure 1 illustrates the model topology for the end-user network.

                     +-------+-------+                      \
                     |   Service     |                       \
                     |   Provider    |                        | Service
                     |    Router     |                        | Provider
                     +-------+-------+                        | network
                             |                               /
                             | Customer                     /
                             | Internet connection         /
                      +------+--------+                    \
                      |     IPv6      |                     \
                      | Customer Edge |                      \
                      |    Router     |                      /
                      +---+-------+-+-+                     /
          Network A       |       |   Network B            | End-User
    ---+-------------+----+-    --+--+-------------+---    | network(s)
       |             |               |             |        \
   +----+-----+ +-----+----+     +----+-----+ +-----+----+   \
   |IPv6 Host | |IPv6 Host |     | IPv6 Host| |IPv6 Host |   /
   |          | |          |     |          | |          |  /
   +----------+ +-----+----+     +----------+ +----------+ /

Figure 1: An Example of a Typical End-User Network

This architecture describes the:

  • Basic capabilities of an IPv6 CE router
  • Provisioning of the WAN interface connecting to the service provider
  • Provisioning of the LAN interfaces

For IPv6 multicast traffic, the IPv6 CE router may act as a Multicast Listener Discovery (MLD) proxy [RFC4605] and may support a dynamic multicast routing protocol.

The IPv6 CE router may be manually configured in an arbitrary topology with a dynamic routing protocol. Automatic provisioning and configuration are described for a single IPv6 CE router only.

3.2.1. Local Communication

Link-local IPv6 addresses are used by hosts communicating on a single link. Unique Local IPv6 Unicast Addresses (ULAs) [RFC4193] are used by hosts communicating within the end-user network across multiple links, but without requiring the application to use a globally routable address. The IPv6 CE router defaults to acting as the demarcation point between two networks by providing a ULA boundary, a multicast zone boundary, and ingress and egress traffic filters.

A dual-stack host is multihomed to IPv4 and IPv6 networks. The IPv4 and IPv6 topologies may not be congruent, and different addresses may have different reachability, e.g., ULAs. A host stack has to be able to quickly fail over and try a different source address and destination address pair if communication fails, as outlined in [HAPPY-EYEBALLS].

At the time of this writing, several host implementations do not handle the case where they have an IPv6 address configured and no IPv6 connectivity, either because the address itself has a limited topological reachability (e.g., ULA) or because the IPv6 CE router is not connected to the IPv6 network on its WAN interface. To support host implementations that do not handle multihoming in a multi-prefix environment [MULTIHOMING-WITHOUT-NAT], the IPv6 CE router should not, as detailed in the requirements below, advertise itself as a default router on the LAN interface(s) when it does not have IPv6 connectivity on the WAN interface or when it is not provisioned with IPv6 addresses. For local IPv6 communication, the mechanisms specified in [RFC4191] are used.

ULA addressing is useful where the IPv6 CE router has multiple LAN interfaces with hosts that need to communicate with each other. If the IPv6 CE router has only a single LAN interface (IPv6 link), then link-local addressing can be used instead.

In the event that more than one IPv6 CE router is present on the LAN, then coexistence with IPv4 requires all of them to conform to these recommendations, especially requirements ULA-5 and L-4 below.

4. Requirements

4.1. General Requirements

The IPv6 CE router is responsible for implementing IPv6 routing; that is, the IPv6 CE router must look up the IPv6 destination address in its routing table to decide to which interface it should send the packet.

In this role, the IPv6 CE router is responsible for ensuring that traffic using its ULA addressing does not go out the WAN interface, and does not originate from the WAN interface.

   G-1:  An IPv6 CE router is an IPv6 node according to the IPv6 Node
         Requirements [RFC4294] specification.
   G-2:  The IPv6 CE router MUST implement ICMP according to [RFC4443].
         In particular, point-to-point links MUST be handled as
         described in Section 3.1 of [RFC4443].
   G-3:  The IPv6 CE router MUST NOT forward any IPv6 traffic between
         its LAN interface(s) and its WAN interface until the router has
         successfully completed the IPv6 address acquisition process.
   G-4:  By default, an IPv6 CE router that has no default router(s) on
         its WAN interface MUST NOT advertise itself as an IPv6 default
         router on its LAN interfaces.  That is, the "Router Lifetime"
         field is set to zero in all Router Advertisement messages it
         originates [RFC4861].
   G-5:  By default, if the IPv6 CE router is an advertising router and
         loses its IPv6 default router(s) on the WAN interface, it MUST
         explicitly invalidate itself as an IPv6 default router on each
         of its advertising interfaces by immediately transmitting one
         or more Router Advertisement messages with the "Router
         Lifetime" field set to zero [RFC4861].

4.2. WAN-Side Configuration

The IPv6 CE router will need to support connectivity to one or more access network architectures. This document describes an IPv6 CE router that is not specific to any particular architecture or service provider and that supports all commonly used architectures.

IPv6 Neighbor Discovery and DHCPv6 protocols operate over any type of IPv6-supported link layer, and there is no need for a link-layer- specific configuration protocol for IPv6 network-layer configuration options as in, e.g., PPP IP Control Protocol (IPCP) for IPv4. This section makes the assumption that the same mechanism will work for any link layer, be it Ethernet, the Data Over Cable Service Interface Specification (DOCSIS), PPP, or others.

WAN-side requirements:

   W-1:  When the router is attached to the WAN interface link, it MUST
         act as an IPv6 host for the purposes of stateless [RFC4862] or
         stateful [RFC3315] interface address assignment.
   W-2:  The IPv6 CE router MUST generate a link-local address and
         finish Duplicate Address Detection according to [RFC4862] prior
         to sending any Router Solicitations on the interface.  The
         source address used in the subsequent Router Solicitation MUST
         be the link-local address on the WAN interface.
   W-3:  Absent other routing information, the IPv6 CE router MUST use
         Router Discovery as specified in [RFC4861] to discover a
         default router(s) and install default route(s) in its routing
         table with the discovered router's address as the next hop.
   W-4:  The router MUST act as a requesting router for the purposes of
         DHCPv6 prefix delegation ([RFC3633]).
   W-5:  DHCPv6 address assignment (IA_NA) and DHCPv6 prefix delegation
         (IA_PD) SHOULD be done as a single DHCPv6 session.
   W-6:  The IPv6 CE router MUST use a persistent DHCP Unique Identifier
         (DUID) for DHCPv6 messages.  The DUID MUST NOT change between
         network interface resets or IPv6 CE router reboots.

Link-layer requirements:

   WLL-1:  If the WAN interface supports Ethernet encapsulation, then
           the IPv6 CE router MUST support IPv6 over Ethernet [RFC2464].
   WLL-2:  If the WAN interface supports PPP encapsulation, the IPv6 CE
           router MUST support IPv6 over PPP [RFC5072].
   WLL-3:  If the WAN interface supports PPP encapsulation, in a dual-
           stack environment with IPCP and IPV6CP running over one PPP
           logical channel, the Network Control Protocols (NCPs) MUST be
           treated as independent of each other and start and terminate

Address assignment requirements:

   WAA-1:  The IPv6 CE router MUST support Stateless Address
           Autoconfiguration (SLAAC) [RFC4862].
   WAA-2:  The IPv6 CE router MUST follow the recommendations in Section
           4 of [RFC5942], and in particular the handling of the L flag
           in the Router Advertisement Prefix Information option.
   WAA-3:  The IPv6 CE router MUST support DHCPv6 [RFC3315] client
   WAA-4:  The IPv6 CE router MUST be able to support the following
           DHCPv6 options: IA_NA, Reconfigure Accept [RFC3315], and
           DNS_SERVERS [RFC3646].
   WAA-5:  The IPv6 CE router SHOULD support the DHCPv6 Simple Network
           Time Protocol (SNTP) option [RFC4075] and the Information
           Refresh Time option [RFC4242].
   WAA-6:  If the IPv6 CE router receives a Router Advertisement message
           (described in [RFC4861]) with the M flag set to 1, the IPv6
           CE router MUST do DHCPv6 address assignment (request an IA_NA
   WAA-7:  If the IPv6 CE router is unable to assign address(es) through
           SLAAC, it MAY do DHCPv6 address assignment (request an IA_NA
           option) even if the M flag is set to 0.
   WAA-8:  If the IPv6 CE router does not acquire global IPv6
           address(es) from either SLAAC or DHCPv6, then it MUST create
           global IPv6 address(es) from its delegated prefix(es) and
           configure those on one of its internal virtual network
   WAA-9:  As a router, the IPv6 CE router MUST follow the weak host
           (Weak ES) model [RFC1122].  When originating packets from an
           interface, it will use a source address from another one of
           its interfaces if the outgoing interface does not have an
           address of suitable scope.

Prefix delegation requirements:

   WPD-1:  The IPv6 CE router MUST support DHCPv6 prefix delegation
           requesting router behavior as specified in [RFC3633] (IA_PD
   WPD-2:  The IPv6 CE router MAY indicate as a hint to the delegating
           router the size of the prefix it requires.  If so, it MUST
           ask for a prefix large enough to assign one /64 for each of
           its interfaces, rounded up to the nearest nibble, and MUST be
           configurable to ask for more.
   WPD-3:  The IPv6 CE router MUST be prepared to accept a delegated
           prefix size different from what is given in the hint.  If the
           delegated prefix is too small to address all of its
           interfaces, the IPv6 CE router SHOULD log a system management
   WPD-4:  The IPv6 CE router MUST always initiate DHCPv6 prefix
           delegation, regardless of the M and O flags in a received
           Router Advertisement message.
   WPD-5:  If the IPv6 CE router initiates DHCPv6 before receiving a
           Router Advertisement, it MUST also request an IA_NA option in
   WPD-6:  If the delegated prefix(es) are aggregate route(s) of
           multiple, more-specific routes, the IPv6 CE router MUST
           discard packets that match the aggregate route(s), but not
           any of the more-specific routes.  In other words, the next
           hop for the aggregate route(s) should be the null
           destination.  This is necessary to prevent forwarding loops
           when some addresses covered by the aggregate are not
           reachable [RFC4632].

(a) The IPv6 CE router SHOULD send an ICMPv6 Destination

Unreachable message in accordance with Section 3.1 of [RFC4443] back to the source of the packet, if the packet is to be dropped due to this rule.

   WPD-7:  If the IPv6 CE router requests both an IA_NA and an IA_PD
           option in DHCPv6, it MUST accept an IA_PD option in DHCPv6
           Advertise/Reply messages, even if the message does not
           contain any addresses.
   WPD-8:  By default, an IPv6 CE router MUST NOT initiate any dynamic
           routing protocol on its WAN interface.

4.3. LAN-Side Configuration

The IPv6 CE router distributes configuration information obtained during WAN interface provisioning to IPv6 hosts and assists IPv6 hosts in obtaining IPv6 addresses. It also supports connectivity of these devices in the absence of any working WAN interface.

An IPv6 CE router is expected to support an IPv6 end-user network and IPv6 hosts that exhibit the following characteristics:

  1. Link-local addresses may be insufficient for allowing IPv6 applications to communicate with each other in the end-user network. The IPv6 CE router will need to enable this communication by providing globally scoped unicast addresses or ULAs [RFC4193], whether or not WAN connectivity exists.
  1. IPv6 hosts should be capable of using SLAAC and may be capable of using DHCPv6 for acquiring their addresses.
  1. IPv6 hosts may use DHCPv6 for other configuration information, such as the DNS_SERVERS option for acquiring DNS information.

Unless otherwise specified, the following requirements apply to the IPv6 CE router's LAN interfaces only.

ULA requirements:

   ULA-1:  The IPv6 CE router SHOULD be capable of generating a ULA
           prefix [RFC4193].
   ULA-2:  An IPv6 CE router with a ULA prefix MUST maintain this prefix
           consistently across reboots.
   ULA-3:  The value of the ULA prefix SHOULD be user-configurable.
   ULA-4:  By default, the IPv6 CE router MUST act as a site border
           router according to Section 4.3 of [RFC4193] and filter
           packets with local IPv6 source or destination addresses
   ULA-5:  An IPv6 CE router MUST NOT advertise itself as a default
           router with a Router Lifetime greater than zero whenever all
           of its configured and delegated prefixes are ULA prefixes.

LAN requirements:

   L-1:   The IPv6 CE router MUST support router behavior according to
          Neighbor Discovery for IPv6 [RFC4861].
   L-2:   The IPv6 CE router MUST assign a separate /64 from its
          delegated prefix(es) (and ULA prefix if configured to provide
          ULA addressing) for each of its LAN interfaces.
   L-3:   An IPv6 CE router MUST advertise itself as a router for the
          delegated prefix(es) (and ULA prefix if configured to provide
          ULA addressing) using the "Route Information Option" specified
          in Section 2.3 of [RFC4191].  This advertisement is
          independent of having or not having IPv6 connectivity on the
          WAN interface.
   L-4:   An IPv6 CE router MUST NOT advertise itself as a default
          router with a Router Lifetime [RFC4861] greater than zero if
          it has no prefixes configured or delegated to it.
   L-5:   The IPv6 CE router MUST make each LAN interface an advertising
          interface according to [RFC4861].
   L-6:   In Router Advertisement messages, the Prefix Information
          option's A and L flags MUST be set to 1 by default.
   L-7:   The A and L flags' settings SHOULD be user-configurable.
   L-8:   The IPv6 CE router MUST support a DHCPv6 server capable of
          IPv6 address assignment according to [RFC3315] OR a stateless
          DHCPv6 server according to [RFC3736] on its LAN interfaces.
   L-9:   Unless the IPv6 CE router is configured to support the DHCPv6
          IA_NA option, it SHOULD set the M flag to 0 and the O flag to
          1 in its Router Advertisement messages [RFC4861].
   L-10:  The IPv6 CE router MUST support providing DNS information in
          the DHCPv6 DNS_SERVERS and DOMAIN_LIST options [RFC3646].
   L-11:  The IPv6 CE router SHOULD support providing DNS information in
          the Router Advertisement Recursive DNS Server (RDNSS) and DNS
          Search List (DNSSL) options as specified in [RFC6106].
   L-12:  The IPv6 CE router SHOULD make available a subset of DHCPv6
          options (as listed in Section 5.3 of [RFC3736]) received from
          the DHCPv6 client on its WAN interface to its LAN-side DHCPv6
   L-13:  If the delegated prefix changes, i.e., the current prefix is
          replaced with a new prefix without any overlapping time
          period, then the IPv6 CE router MUST immediately advertise the
          old prefix with a Preferred Lifetime of zero and a Valid
          Lifetime of the lower of the current Valid Lifetime and 2
          hours (which must be decremented in real time) in a Router
          Advertisement message as described in Section 5.5.3, (e) of
   L-14:  The IPv6 CE router MUST send an ICMP Destination Unreachable
          message, code 5 (Source address failed ingress/egress policy)
          for packets forwarded to it that use an address from a prefix
          that has been deprecated.

4.4. Security Considerations

It is considered a best practice to filter obviously malicious traffic (e.g., spoofed packets, "Martian" addresses, etc.). Thus, the IPv6 CE router ought to support basic stateless egress and ingress filters. The CE router is also expected to offer mechanisms to filter traffic entering the customer network; however, the method by which vendors implement configurable packet filtering is beyond the scope of this document.

Security requirements:

   S-1:  The IPv6 CE router SHOULD support [RFC6092].  In particular,
         the IPv6 CE router SHOULD support functionality sufficient for
         implementing the set of recommendations in [RFC6092],
         Section 4.  This document takes no position on whether such
         functionality is enabled by default or mechanisms by which
         users would configure it.
   S-2:  The IPv6 CE router MUST support ingress filtering in accordance
         with BCP 38 [RFC2827].

5. Acknowledgements

Thanks to the following people (in alphabetical order) for their guidance and feedback:

   Mikael Abrahamsson, Tore Anderson, Merete Asak, Scott Beuker, Mohamed
   Boucadair, Rex Bullinger, Brian Carpenter, Lorenzo Colitti, Remi
   Denis-Courmont, Gert Doering, Alain Durand, Katsunori Fukuoka, Tony
   Hain, Thomas Herbst, Kevin Johns, Erik Kline, Stephen Kramer, Victor
   Kuarsingh, Francois-Xavier Le Bail, Arifumi Matsumoto, David Miles,
   Shin Miyakawa, Jean-Francois Mule, Michael Newbery, Carlos Pignataro,
   John Pomeroy, Antonio Querubin, Hiroki Sato, Teemu Savolainen, Matt
   Schmitt, David Thaler, Mark Townsley, Bernie Volz, Dan Wing, James
   Woodyatt, and Cor Zwart.

This document is based in part on CableLabs' eRouter specification. The authors wish to acknowledge the additional contributors from the eRouter team:

Ben Bekele, Amol Bhagwat, Ralph Brown, Eduardo Cardona, Margo Dolas, Toerless Eckert, Doc Evans, Roger Fish, Michelle Kuska, Diego Mazzola, John McQueen, Harsh Parandekar, Michael Patrick, Saifur Rahman, Lakshmi Raman, Ryan Ross, Ron da Silva, Madhu Sudan, Dan Torbet, and Greg White.

6. Contributors

The following people have participated as co-authors or provided substantial contributions to this document: Ralph Droms, Kirk Erichsen, Fred Baker, Jason Weil, Lee Howard, Jean-Francois Tremblay, Yiu Lee, John Jason Brzozowski, and Heather Kirksey.

7. References

7.1. Normative References

   [RFC1122]  Braden, R., Ed., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122, October 1989.
   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.
   [RFC2464]  Crawford, M., "Transmission of IPv6 Packets over Ethernet
              Networks", RFC 2464, December 1998.
   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, May 2000.
   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, July 2003.
   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              December 2003.
   [RFC3646]  Droms, R., Ed., "DNS Configuration options for Dynamic
              Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
              December 2003.
   [RFC3736]  Droms, R., "Stateless Dynamic Host Configuration Protocol
              (DHCP) Service for IPv6", RFC 3736, April 2004.
   [RFC4075]  Kalusivalingam, V., "Simple Network Time Protocol (SNTP)
              Configuration Option for DHCPv6", RFC 4075, May 2005.
   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, November 2005.
   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005.
   [RFC4242]  Venaas, S., Chown, T., and B. Volz, "Information Refresh
              Time Option for Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 4242, November 2005.
   [RFC4294]  Loughney, J., Ed., "IPv6 Node Requirements", RFC 4294,
              April 2006.
   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", RFC 4443,
              March 2006.
   [RFC4605]  Fenner, B., He, H., Haberman, B., and H. Sandick,
              "Internet Group Management Protocol (IGMP) / Multicast
              Listener Discovery (MLD)-Based Multicast Forwarding
              ("IGMP/MLD Proxying")", RFC 4605, August 2006.
   [RFC4632]  Fuller, V. and T. Li, "Classless Inter-domain Routing
              (CIDR): The Internet Address Assignment and Aggregation
              Plan", BCP 122, RFC 4632, August 2006.
   [RFC4779]  Asadullah, S., Ahmed, A., Popoviciu, C., Savola, P., and
              J. Palet, "ISP IPv6 Deployment Scenarios in Broadband
              Access Networks", RFC 4779, January 2007.
   [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.
   [RFC4864]  Van de Velde, G., Hain, T., Droms, R., Carpenter, B., and
              E. Klein, "Local Network Protection for IPv6", RFC 4864,
              May 2007.
   [RFC5072]  Varada, S., Ed., Haskins, D., and E. Allen, "IP Version 6
              over PPP", RFC 5072, September 2007.
   [RFC5942]  Singh, H., Beebee, W., and E. Nordmark, "IPv6 Subnet
              Model: The Relationship between Links and Subnet
              Prefixes", RFC 5942, July 2010.
   [RFC6092]  Woodyatt, J., Ed., "Recommended Simple Security
              Capabilities in Customer Premises Equipment (CPE) for
              Providing Residential IPv6 Internet Service", RFC 6092,
              January 2011.
   [RFC6106]  Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
              "IPv6 Router Advertisement Options for DNS Configuration",
              RFC 6106, November 2010.

7.2. Informative References


              Wing, D. and A. Yourtchenko, "Happy Eyeballs: Trending
              Towards Success with Dual-Stack Hosts", Work in Progress,
              March 2011.


              Troan, O., Ed., Miles, D., Matsushima, S., Okimoto, T.,
              and D. Wing, "IPv6 Multihoming without Network Address
              Translation", Work in Progress, March 2011.
   [RFC6144]  Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
              IPv4/IPv6 Translation", RFC 6144, April 2011.


              UPnP Forum, "Universal Plug and Play (UPnP) Internet
              Gateway Device (IGD)", November 2001,

Authors' Addresses

   Hemant Singh
   Cisco Systems, Inc.
   1414 Massachusetts Ave.
   Boxborough, MA  01719
   Phone: +1 978 936 1622
   Wes Beebee
   Cisco Systems, Inc.
   1414 Massachusetts Ave.
   Boxborough, MA  01719
   Phone: +1 978 936 2030
   Chris Donley
   858 Coal Creek Circle
   Louisville, CO  80027
   Barbara Stark
   725 W Peachtree St.
   Atlanta, GA  30308
   Ole Troan (editor)
   Cisco Systems, Inc.
   Telemarksvingen 20
   N-0655 OSLO,