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<pre>Internet Engineering Task Force (IETF) H. Singh
Request for Comments: 6204 W. Beebee
Category: Informational Cisco Systems, Inc.
ISSN: 2070-1721 C. Donley
CableLabs
B. Stark
AT&T
O. Troan, Ed.
Cisco Systems, Inc.
April 2011
<span class="h1">Basic Requirements for IPv6 Customer Edge Routers</span>
Abstract
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 <a href="./rfc5741#section-2">Section 2 of RFC 5741</a>.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
<a href="http://www.rfc-editor.org/info/rfc6204">http://www.rfc-editor.org/info/rfc6204</a>.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a> and the IETF Trust's Legal
Provisions Relating to IETF Documents
(<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>) 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
<span class="grey">Singh, et al. Informational [Page 1]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-2" ></span>
<span class="grey"><a href="./rfc6204">RFC 6204</a> IPv6 CE Router Requirements April 2011</span>
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
<a href="#section-1">1</a>. Introduction ....................................................<a href="#page-2">2</a>
<a href="#section-1.1">1.1</a>. Requirements Language ......................................<a href="#page-3">3</a>
<a href="#section-2">2</a>. Terminology .....................................................<a href="#page-3">3</a>
<a href="#section-3">3</a>. Architecture ....................................................<a href="#page-4">4</a>
<a href="#section-3.1">3.1</a>. Current IPv4 End-User Network Architecture .................<a href="#page-4">4</a>
<a href="#section-3.2">3.2</a>. IPv6 End-User Network Architecture .........................<a href="#page-4">4</a>
<a href="#section-3.2.1">3.2.1</a>. Local Communication .................................<a href="#page-6">6</a>
<a href="#section-4">4</a>. Requirements ....................................................<a href="#page-6">6</a>
<a href="#section-4.1">4.1</a>. General Requirements .......................................<a href="#page-6">6</a>
<a href="#section-4.2">4.2</a>. WAN-Side Configuration .....................................<a href="#page-7">7</a>
<a href="#section-4.3">4.3</a>. LAN-Side Configuration ....................................<a href="#page-11">11</a>
<a href="#section-4.4">4.4</a>. Security Considerations ...................................<a href="#page-13">13</a>
<a href="#section-5">5</a>. Acknowledgements ...............................................<a href="#page-13">13</a>
<a href="#section-6">6</a>. Contributors ...................................................<a href="#page-14">14</a>
<a href="#section-7">7</a>. References .....................................................<a href="#page-14">14</a>
<a href="#section-7.1">7.1</a>. Normative References ......................................<a href="#page-14">14</a>
<a href="#section-7.2">7.2</a>. Informative References ....................................<a href="#page-16">16</a>
<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span>
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 [<a href="./rfc6144" title=""Framework for IPv4/IPv6 Translation"">RFC6144</a>]. 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 [<a href="./rfc4779" title=""ISP IPv6 Deployment Scenarios in Broadband Access Networks"">RFC4779</a>] for a discussion of options available for deploying
IPv6 in service provider access networks.
<span class="grey">Singh, et al. Informational [Page 2]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-3" ></span>
<span class="grey"><a href="./rfc6204">RFC 6204</a> IPv6 CE Router Requirements April 2011</span>
<span class="h3"><a class="selflink" id="section-1.1" href="#section-1.1">1.1</a>. Requirements Language</span>
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 <a href="./rfc2119">RFC 2119</a> [<a href="./rfc2119" title=""Key words for use in RFCs to Indicate Requirement Levels"">RFC2119</a>].
<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. Terminology</span>
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.
<span class="grey">Singh, et al. Informational [Page 3]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-4" ></span>
<span class="grey"><a href="./rfc6204">RFC 6204</a> IPv6 CE Router Requirements April 2011</span>
<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. Architecture</span>
<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a>. Current IPv4 End-User Network Architecture</span>
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) [<a href="#ref-UPnP-IGD">UPnP-IGD</a>] 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 [<a href="./rfc4864" title=""Local Network Protection for IPv6"">RFC4864</a>].
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.
<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a>. IPv6 End-User Network Architecture</span>
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.
<span class="grey">Singh, et al. Informational [Page 4]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-5" ></span>
<span class="grey"><a href="./rfc6204">RFC 6204</a> IPv6 CE Router Requirements April 2011</span>
+-------+-------+ \
| 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:
o Basic capabilities of an IPv6 CE router
o Provisioning of the WAN interface connecting to the service
provider
o Provisioning of the LAN interfaces
For IPv6 multicast traffic, the IPv6 CE router may act as a Multicast
Listener Discovery (MLD) proxy [<a href="./rfc4605" title=""Internet Group Management Protocol (IGMP) / Multicast Listener Discovery (MLD)-Based Multicast Forwarding ("">RFC4605</a>] 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.
<span class="grey">Singh, et al. Informational [Page 5]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-6" ></span>
<span class="grey"><a href="./rfc6204">RFC 6204</a> IPv6 CE Router Requirements April 2011</span>
<span class="h4"><a class="selflink" id="section-3.2.1" href="#section-3.2.1">3.2.1</a>. Local Communication</span>
Link-local IPv6 addresses are used by hosts communicating on a single
link. Unique Local IPv6 Unicast Addresses (ULAs) [<a href="./rfc4193" title=""Unique Local IPv6 Unicast Addresses"">RFC4193</a>] 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
[<a href="#ref-HAPPY-EYEBALLS">HAPPY-EYEBALLS</a>].
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 [<a href="#ref-MULTIHOMING-WITHOUT-NAT">MULTIHOMING-WITHOUT-NAT</a>], 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 [<a href="./rfc4191" title=""Default Router Preferences and More-Specific Routes"">RFC4191</a>] 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.
<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. Requirements</span>
<span class="h3"><a class="selflink" id="section-4.1" href="#section-4.1">4.1</a>. General Requirements</span>
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.
<span class="grey">Singh, et al. Informational [Page 6]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-7" ></span>
<span class="grey"><a href="./rfc6204">RFC 6204</a> IPv6 CE Router Requirements April 2011</span>
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 [<a href="./rfc4294" title=""IPv6 Node Requirements"">RFC4294</a>] specification.
G-2: The IPv6 CE router MUST implement ICMP according to [<a href="./rfc4443" title=""Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification"">RFC4443</a>].
In particular, point-to-point links MUST be handled as
described in <a href="./rfc4443#section-3.1">Section 3.1 of [RFC4443]</a>.
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 [<a href="./rfc4861" title=""Neighbor Discovery for IP version 6 (IPv6)"">RFC4861</a>].
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 [<a href="./rfc4861" title=""Neighbor Discovery for IP version 6 (IPv6)"">RFC4861</a>].
<span class="h3"><a class="selflink" id="section-4.2" href="#section-4.2">4.2</a>. WAN-Side Configuration</span>
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.
<span class="grey">Singh, et al. Informational [Page 7]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-8" ></span>
<span class="grey"><a href="./rfc6204">RFC 6204</a> IPv6 CE Router Requirements April 2011</span>
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 [<a href="./rfc4862" title=""IPv6 Stateless Address Autoconfiguration"">RFC4862</a>] or
stateful [<a href="./rfc3315" title=""Dynamic Host Configuration Protocol for IPv6 (DHCPv6)"">RFC3315</a>] interface address assignment.
W-2: The IPv6 CE router MUST generate a link-local address and
finish Duplicate Address Detection according to [<a href="./rfc4862" title=""IPv6 Stateless Address Autoconfiguration"">RFC4862</a>] 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 [<a href="./rfc4861" title=""Neighbor Discovery for IP version 6 (IPv6)"">RFC4861</a>] 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 ([<a href="./rfc3633" title=""IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6"">RFC3633</a>]).
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 [<a href="./rfc2464" title=""Transmission of IPv6 Packets over Ethernet Networks"">RFC2464</a>].
WLL-2: If the WAN interface supports PPP encapsulation, the IPv6 CE
router MUST support IPv6 over PPP [<a href="./rfc5072" title=""IP Version 6 over PPP"">RFC5072</a>].
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
independently.
<span class="grey">Singh, et al. Informational [Page 8]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-9" ></span>
<span class="grey"><a href="./rfc6204">RFC 6204</a> IPv6 CE Router Requirements April 2011</span>
Address assignment requirements:
WAA-1: The IPv6 CE router MUST support Stateless Address
Autoconfiguration (SLAAC) [<a href="./rfc4862" title=""IPv6 Stateless Address Autoconfiguration"">RFC4862</a>].
WAA-2: The IPv6 CE router MUST follow the recommendations in <a href="./rfc5942#section-4">Section</a>
<a href="./rfc5942#section-4">4 of [RFC5942]</a>, 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 [<a href="./rfc3315" title=""Dynamic Host Configuration Protocol for IPv6 (DHCPv6)"">RFC3315</a>] client
behavior.
WAA-4: The IPv6 CE router MUST be able to support the following
DHCPv6 options: IA_NA, Reconfigure Accept [<a href="./rfc3315" title=""Dynamic Host Configuration Protocol for IPv6 (DHCPv6)"">RFC3315</a>], and
DNS_SERVERS [<a href="./rfc3646" title=""DNS Configuration options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)"">RFC3646</a>].
WAA-5: The IPv6 CE router SHOULD support the DHCPv6 Simple Network
Time Protocol (SNTP) option [<a href="./rfc4075" title=""Simple Network Time Protocol (SNTP) Configuration Option for DHCPv6"">RFC4075</a>] and the Information
Refresh Time option [<a href="./rfc4242" title=""Information Refresh Time Option for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)"">RFC4242</a>].
WAA-6: If the IPv6 CE router receives a Router Advertisement message
(described in [<a href="./rfc4861" title=""Neighbor Discovery for IP version 6 (IPv6)"">RFC4861</a>]) with the M flag set to 1, the IPv6
CE router MUST do DHCPv6 address assignment (request an IA_NA
option).
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
interfaces.
WAA-9: As a router, the IPv6 CE router MUST follow the weak host
(Weak ES) model [<a href="./rfc1122" title=""Requirements for Internet Hosts - Communication Layers"">RFC1122</a>]. 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.
<span class="grey">Singh, et al. Informational [Page 9]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-10" ></span>
<span class="grey"><a href="./rfc6204">RFC 6204</a> IPv6 CE Router Requirements April 2011</span>
Prefix delegation requirements:
WPD-1: The IPv6 CE router MUST support DHCPv6 prefix delegation
requesting router behavior as specified in [<a href="./rfc3633" title=""IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6"">RFC3633</a>] (IA_PD
option).
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
error.
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
DHCPv6.
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 [<a href="./rfc4632" title=""Classless Inter-domain Routing (CIDR): The Internet Address Assignment and Aggregation Plan"">RFC4632</a>].
(a) The IPv6 CE router SHOULD send an ICMPv6 Destination
Unreachable message in accordance with <a href="./rfc4443#section-3.1">Section 3.1 of
[RFC4443]</a> 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.
<span class="grey">Singh, et al. Informational [Page 10]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-11" ></span>
<span class="grey"><a href="./rfc6204">RFC 6204</a> IPv6 CE Router Requirements April 2011</span>
<span class="h3"><a class="selflink" id="section-4.3" href="#section-4.3">4.3</a>. LAN-Side Configuration</span>
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 [<a href="./rfc4193" title=""Unique Local IPv6 Unicast Addresses"">RFC4193</a>], whether or not WAN connectivity exists.
2. IPv6 hosts should be capable of using SLAAC and may be capable of
using DHCPv6 for acquiring their addresses.
3. 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 [<a href="./rfc4193" title=""Unique Local IPv6 Unicast Addresses"">RFC4193</a>].
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 <a href="./rfc4193#section-4.3">Section 4.3 of [RFC4193]</a> and filter
packets with local IPv6 source or destination addresses
accordingly.
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.
<span class="grey">Singh, et al. Informational [Page 11]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-12" ></span>
<span class="grey"><a href="./rfc6204">RFC 6204</a> IPv6 CE Router Requirements April 2011</span>
LAN requirements:
L-1: The IPv6 CE router MUST support router behavior according to
Neighbor Discovery for IPv6 [<a href="./rfc4861" title=""Neighbor Discovery for IP version 6 (IPv6)"">RFC4861</a>].
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 <a href="./rfc4191#section-2.3">Section 2.3 of [RFC4191]</a>. 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 [<a href="./rfc4861" title=""Neighbor Discovery for IP version 6 (IPv6)"">RFC4861</a>] 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 [<a href="./rfc4861" title=""Neighbor Discovery for IP version 6 (IPv6)"">RFC4861</a>].
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 [<a href="./rfc3315" title=""Dynamic Host Configuration Protocol for IPv6 (DHCPv6)"">RFC3315</a>] OR a stateless
DHCPv6 server according to [<a href="./rfc3736" title=""Stateless Dynamic Host Configuration Protocol (DHCP) Service for IPv6"">RFC3736</a>] 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 [<a href="./rfc4861" title=""Neighbor Discovery for IP version 6 (IPv6)"">RFC4861</a>].
L-10: The IPv6 CE router MUST support providing DNS information in
the DHCPv6 DNS_SERVERS and DOMAIN_LIST options [<a href="./rfc3646" title=""DNS Configuration options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)"">RFC3646</a>].
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 [<a href="./rfc6106" title=""IPv6 Router Advertisement Options for DNS Configuration"">RFC6106</a>].
L-12: The IPv6 CE router SHOULD make available a subset of DHCPv6
options (as listed in <a href="./rfc3736#section-5.3">Section 5.3 of [RFC3736]</a>) received from
the DHCPv6 client on its WAN interface to its LAN-side DHCPv6
server.
<span class="grey">Singh, et al. Informational [Page 12]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-13" ></span>
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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 <a href="#section-5.5.3">Section 5.5.3</a>, (e) of
[<a href="./rfc4862" title=""IPv6 Stateless Address Autoconfiguration"">RFC4862</a>].
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.
<span class="h3"><a class="selflink" id="section-4.4" href="#section-4.4">4.4</a>. Security Considerations</span>
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 [<a href="./rfc6092" title=""Recommended Simple Security Capabilities in Customer Premises Equipment (CPE) for Providing Residential IPv6 Internet Service"">RFC6092</a>]. In particular,
the IPv6 CE router SHOULD support functionality sufficient for
implementing the set of recommendations in <a href="./rfc6092#section-4">[RFC6092],
Section 4</a>. 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 <a href="https://www.rfc-editor.org/bcp/bcp38">BCP 38</a> [<a href="./rfc2827" title=""Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing"">RFC2827</a>].
<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>. Acknowledgements</span>
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
<span class="grey">Singh, et al. Informational [Page 13]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-14" ></span>
<span class="grey"><a href="./rfc6204">RFC 6204</a> IPv6 CE Router Requirements April 2011</span>
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.
<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>. Contributors</span>
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.
<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>. References</span>
<span class="h3"><a class="selflink" id="section-7.1" href="#section-7.1">7.1</a>. Normative References</span>
[<a id="ref-RFC1122">RFC1122</a>] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, <a href="./rfc1122">RFC 1122</a>, October 1989.
[<a id="ref-RFC2119">RFC2119</a>] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a>, March 1997.
[<a id="ref-RFC2464">RFC2464</a>] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Networks", <a href="./rfc2464">RFC 2464</a>, December 1998.
[<a id="ref-RFC2827">RFC2827</a>] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", <a href="https://www.rfc-editor.org/bcp/bcp38">BCP 38</a>, <a href="./rfc2827">RFC 2827</a>, May 2000.
[<a id="ref-RFC3315">RFC3315</a>] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
C., and M. Carney, "Dynamic Host Configuration Protocol
for IPv6 (DHCPv6)", <a href="./rfc3315">RFC 3315</a>, July 2003.
[<a id="ref-RFC3633">RFC3633</a>] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
Host Configuration Protocol (DHCP) version 6", <a href="./rfc3633">RFC 3633</a>,
December 2003.
<span class="grey">Singh, et al. Informational [Page 14]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-15" ></span>
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[<a id="ref-RFC3646">RFC3646</a>] Droms, R., Ed., "DNS Configuration options for Dynamic
Host Configuration Protocol for IPv6 (DHCPv6)", <a href="./rfc3646">RFC 3646</a>,
December 2003.
[<a id="ref-RFC3736">RFC3736</a>] Droms, R., "Stateless Dynamic Host Configuration Protocol
(DHCP) Service for IPv6", <a href="./rfc3736">RFC 3736</a>, April 2004.
[<a id="ref-RFC4075">RFC4075</a>] Kalusivalingam, V., "Simple Network Time Protocol (SNTP)
Configuration Option for DHCPv6", <a href="./rfc4075">RFC 4075</a>, May 2005.
[<a id="ref-RFC4191">RFC4191</a>] Draves, R. and D. Thaler, "Default Router Preferences and
More-Specific Routes", <a href="./rfc4191">RFC 4191</a>, November 2005.
[<a id="ref-RFC4193">RFC4193</a>] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", <a href="./rfc4193">RFC 4193</a>, October 2005.
[<a id="ref-RFC4242">RFC4242</a>] Venaas, S., Chown, T., and B. Volz, "Information Refresh
Time Option for Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", <a href="./rfc4242">RFC 4242</a>, November 2005.
[<a id="ref-RFC4294">RFC4294</a>] Loughney, J., Ed., "IPv6 Node Requirements", <a href="./rfc4294">RFC 4294</a>,
April 2006.
[<a id="ref-RFC4443">RFC4443</a>] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", <a href="./rfc4443">RFC 4443</a>,
March 2006.
[<a id="ref-RFC4605">RFC4605</a>] Fenner, B., He, H., Haberman, B., and H. Sandick,
"Internet Group Management Protocol (IGMP) / Multicast
Listener Discovery (MLD)-Based Multicast Forwarding
("IGMP/MLD Proxying")", <a href="./rfc4605">RFC 4605</a>, August 2006.
[<a id="ref-RFC4632">RFC4632</a>] Fuller, V. and T. Li, "Classless Inter-domain Routing
(CIDR): The Internet Address Assignment and Aggregation
Plan", <a href="https://www.rfc-editor.org/bcp/bcp122">BCP 122</a>, <a href="./rfc4632">RFC 4632</a>, August 2006.
[<a id="ref-RFC4779">RFC4779</a>] Asadullah, S., Ahmed, A., Popoviciu, C., Savola, P., and
J. Palet, "ISP IPv6 Deployment Scenarios in Broadband
Access Networks", <a href="./rfc4779">RFC 4779</a>, January 2007.
[<a id="ref-RFC4861">RFC4861</a>] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", <a href="./rfc4861">RFC 4861</a>,
September 2007.
[<a id="ref-RFC4862">RFC4862</a>] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", <a href="./rfc4862">RFC 4862</a>, September 2007.
<span class="grey">Singh, et al. Informational [Page 15]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-16" ></span>
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[<a id="ref-RFC4864">RFC4864</a>] Van de Velde, G., Hain, T., Droms, R., Carpenter, B., and
E. Klein, "Local Network Protection for IPv6", <a href="./rfc4864">RFC 4864</a>,
May 2007.
[<a id="ref-RFC5072">RFC5072</a>] Varada, S., Ed., Haskins, D., and E. Allen, "IP Version 6
over PPP", <a href="./rfc5072">RFC 5072</a>, September 2007.
[<a id="ref-RFC5942">RFC5942</a>] Singh, H., Beebee, W., and E. Nordmark, "IPv6 Subnet
Model: The Relationship between Links and Subnet
Prefixes", <a href="./rfc5942">RFC 5942</a>, July 2010.
[<a id="ref-RFC6092">RFC6092</a>] Woodyatt, J., Ed., "Recommended Simple Security
Capabilities in Customer Premises Equipment (CPE) for
Providing Residential IPv6 Internet Service", <a href="./rfc6092">RFC 6092</a>,
January 2011.
[<a id="ref-RFC6106">RFC6106</a>] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
"IPv6 Router Advertisement Options for DNS Configuration",
<a href="./rfc6106">RFC 6106</a>, November 2010.
<span class="h3"><a class="selflink" id="section-7.2" href="#section-7.2">7.2</a>. Informative References</span>
[<a id="ref-HAPPY-EYEBALLS">HAPPY-EYEBALLS</a>]
Wing, D. and A. Yourtchenko, "Happy Eyeballs: Trending
Towards Success with Dual-Stack Hosts", Work in Progress,
March 2011.
[<a id="ref-MULTIHOMING-WITHOUT-NAT">MULTIHOMING-WITHOUT-NAT</a>]
Troan, O., Ed., Miles, D., Matsushima, S., Okimoto, T.,
and D. Wing, "IPv6 Multihoming without Network Address
Translation", Work in Progress, March 2011.
[<a id="ref-RFC6144">RFC6144</a>] Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
IPv4/IPv6 Translation", <a href="./rfc6144">RFC 6144</a>, April 2011.
[<a id="ref-UPnP-IGD">UPnP-IGD</a>]
UPnP Forum, "Universal Plug and Play (UPnP) Internet
Gateway Device (IGD)", November 2001,
<<a href="http://www.upnp.org/">http://www.upnp.org/</a>>.
<span class="grey">Singh, et al. Informational [Page 16]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-17" ></span>
<span class="grey"><a href="./rfc6204">RFC 6204</a> IPv6 CE Router Requirements April 2011</span>
Authors' Addresses
Hemant Singh
Cisco Systems, Inc.
1414 Massachusetts Ave.
Boxborough, MA 01719
USA
Phone: +1 978 936 1622
EMail: shemant@cisco.com
URI: <a href="http://www.cisco.com/">http://www.cisco.com/</a>
Wes Beebee
Cisco Systems, Inc.
1414 Massachusetts Ave.
Boxborough, MA 01719
USA
Phone: +1 978 936 2030
EMail: wbeebee@cisco.com
URI: <a href="http://www.cisco.com/">http://www.cisco.com/</a>
Chris Donley
CableLabs
858 Coal Creek Circle
Louisville, CO 80027
USA
EMail: c.donley@cablelabs.com
Barbara Stark
AT&T
725 W Peachtree St.
Atlanta, GA 30308
USA
EMail: barbara.stark@att.com
Ole Troan (editor)
Cisco Systems, Inc.
Telemarksvingen 20
N-0655 OSLO,
Norway
EMail: ot@cisco.com
Singh, et al. Informational [Page 17]
</pre>
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