| Rfc | 7084 |
|---|
| Title | Basic Requirements for IPv6 Customer Edge Routers |
|---|
| Author | H. Singh, W.
Beebee, C. Donley, B. Stark |
|---|
| Date | November 2013 |
|---|
| Format: | TXT, HTML |
|---|
| Obsoletes | RFC6204 |
|---|
| Updated by | RFC9096 |
|---|
| Status: | INFORMATIONAL |
|---|
|
Internet Engineering Task Force (IETF) H. Singh
Request for Comments: 7084 W. Beebee
Obsoletes: 6204 Cisco Systems, Inc.
Category: Informational C. Donley
ISSN: 2070-1721 CableLabs
B. Stark
AT&T
November 2013
Basic Requirements for IPv6 Customer Edge Routers
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. The document also covers IP transition
technologies. Two transition technologies in RFC 5969's IPv6 Rapid
Deployment on IPv4 Infrastructures (6rd) and RFC 6333's Dual-Stack
Lite (DS-Lite) are covered in the document. The document obsoletes
RFC 6204.
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
http://www.rfc-editor.org/info/rfc7084.
Copyright Notice
Copyright (c) 2013 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
1.1. Requirements Language ......................................3
2. Terminology .....................................................4
3. Architecture ....................................................5
3.1. Current IPv4 End-User Network Architecture .................5
3.2. IPv6 End-User Network Architecture .........................5
3.2.1. Local Communication .................................7
4. Requirements ....................................................7
4.1. General Requirements .......................................7
4.2. WAN-Side Configuration .....................................8
4.3. LAN-Side Configuration ....................................12
4.4. Transition Technologies Support ...........................14
4.4.1. 6rd ................................................14
4.4.2. Dual-Stack Lite (DS-Lite) ..........................15
4.5. Security Considerations ...................................16
5. Acknowledgements ...............................................17
6. Contributors ...................................................17
7. References .....................................................18
7.1. Normative References ......................................18
7.2. Informative References ....................................20
1. Introduction
This document defines basic IPv6 features for a residential or small-
office router, referred to as an "IPv6 CE router", in order to
establish an industry baseline for features to be implemented on such
a router.
These routers typically 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.
The document also covers the IP transition technologies that were
available at the time this document was written. Two transition
technologies in 6rd [RFC5969] and DS-Lite [RFC6333] are covered in
the document.
1.1. Requirements Language
Take careful note: Unlike other IETF documents, the key words "MUST",
"MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in this document are not used as
described in RFC 2119 [RFC2119]. This document uses these keywords
not strictly for the purpose of interoperability, but rather for the
purpose of establishing industry-common baseline functionality. As
such, the document points to several other specifications (preferable
in RFC or stable form) to provide additional guidance to implementers
regarding any protocol implementation required to produce a
successful CE router that interoperates successfully with a
particular subset of currently deploying and planned common IPv6
access networks.
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
Ethernet (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 it 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 Ethernet (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; that is, 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.
Many existing routers support dynamic routing (which learns routes
from other routers), 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:
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 [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.
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.
Coexistence with IPv4 requires any IPv6 CE router(s) on the LAN 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 specification [RFC6434].
G-2: The IPv6 CE router MUST implement ICMPv6 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 and the delegated
prefix 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) and/or detects loss of
connectivity 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 a 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: 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.
W-6: The WAN interface of the CE router SHOULD support a Port
Control Protocol (PCP) client as specified in [RFC6887] for use
by applications on the CE router. The PCP client SHOULD follow
the procedure specified in Section 8.1 of [RFC6887] to discover
its PCP server. This document takes no position on whether
such functionality is enabled by default or mechanisms by which
users would configure the functionality. Handling PCP requests
from PCP clients in the LAN side of the CE router is out of
scope.
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
independently.
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
behavior.
WAA-4: The IPv6 CE router MUST be able to support the following
DHCPv6 options: Identity Association for Non-temporary
Address (IA_NA), Reconfigure Accept [RFC3315], and
DNS_SERVERS [RFC3646]. The IPv6 CE router SHOULD be able to
support the DNS Search List (DNSSL) option as specified in
[RFC3646].
WAA-5: The IPv6 CE router SHOULD implement the Network Time
Protocol (NTP) as specified in [RFC5905] to provide a time
reference common to the service provider for other
protocols, such as DHCPv6, to use. If the CE router
implements NTP, it requests the NTP Server DHCPv6 option
[RFC5908] and uses the received list of servers as primary
time reference, unless explicitly configured otherwise. LAN
side support of NTP is out of scope for this document.
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 option).
WAA-7: If the IPv6 CE router does not acquire a global IPv6
address(es) from either SLAAC or DHCPv6, then it MUST create
a global IPv6 address(es) from its delegated prefix(es) and
configure those on one of its internal virtual network
interfaces, unless configured to require a global IPv6
address on the WAN interface.
WAA-8: The CE router MUST support the SOL_MAX_RT option [RFC7083]
and request the SOL_MAX_RT option in an Option Request
Option (ORO).
WAA-9: As a router, the IPv6 CE router MUST follow the weak host
(Weak End System) 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.
WAA-10: The IPv6 CE router SHOULD implement the Information Refresh
Time option and associated client behavior as specified in
[RFC4242].
Prefix delegation requirements:
WPD-1: The IPv6 CE router MUST support DHCPv6 prefix delegation
requesting router behavior as specified in [RFC3633]
(Identity Association for Prefix Delegation (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 SHOULD
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. [RFC6177] covers the recommendations for service
providers for prefix allocation sizes.
WPD-4: By default, the IPv6 CE router MUST initiate DHCPv6 prefix
delegation when either the M or O flags are set to 1 in a
received Router Advertisement (RA) message. Behavior of the
CE router to use DHCPv6 prefix delegation when the CE router
has not received any RA or received an RA with the M and the
O bits set to zero is out of scope for this document.
WPD-5: Any packet received by the CE router with a destination
address in the prefix(es) delegated to the CE router but not
in the set of prefixes assigned by the CE router to the LAN
must be dropped. In other words, the next hop for the
prefix(es) delegated to the CE router 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-6: 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, unless configured to only obtain its
WAN IPv6 address via DHCPv6; see [DHCPv6-STATEFUL-ISSUES].
WPD-7: By default, an IPv6 CE router MUST NOT initiate any dynamic
routing protocol on its WAN interface.
WPD-8: The IPv6 CE router SHOULD support the [RFC6603] Prefix
Exclude option.
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.
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 [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 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
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.
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 ([RFC4861]), the Prefix
Information option's A and L flags MUST be set to 1 by
default.
L-7: The A and L flags' ([RFC4861]) 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 zero 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 MUST support providing DNS information in
the Router Advertisement Recursive DNS Server (RDNSS) and DNS
Search List options. Both options are 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
server.
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 either a) zero or b) the lower of the current
Valid Lifetime and two hours (which must be decremented in
real time) in a Router Advertisement message as described in
Section 5.5.3, (e) of [RFC4862].
L-14: The IPv6 CE router MUST send an ICMPv6 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 invalidated.
4.4. Transition Technologies Support
4.4.1. 6rd
6rd [RFC5969] specifies an automatic tunneling mechanism tailored to
advance deployment of IPv6 to end users via a service provider's IPv4
network infrastructure. Key aspects include automatic IPv6 prefix
delegation to sites, stateless operation, simple provisioning, and
service that is equivalent to native IPv6 at the sites that are
served by the mechanism. It is expected that such traffic is
forwarded over the CE router's native IPv4 WAN interface and not
encapsulated in another tunnel.
The CE router SHOULD support 6rd functionality. If 6rd is supported,
it MUST be implemented according to [RFC5969]. The following CE
Requirements also apply:
6rd requirements:
6RD-1: The IPv6 CE router MUST support 6rd configuration via the 6rd
DHCPv4 Option 212. If the CE router has obtained an IPv4
network address through some other means such as PPP, it
SHOULD use the DHCPINFORM request message [RFC2131] to
request the 6rd DHCPv4 Option. The IPv6 CE router MAY use
other mechanisms to configure 6rd parameters. Such
mechanisms are outside the scope of this document.
6RD-2: If the IPv6 CE router is capable of automated configuration
of IPv4 through IPCP (i.e., over a PPP connection), it MUST
support user-entered configuration of 6rd.
6RD-3: If the CE router supports configuration mechanisms other than
the 6rd DHCPv4 Option 212 (user-entered, TR-069 [TR-069],
etc.), the CE router MUST support 6rd in "hub and spoke"
mode. 6rd in "hub and spoke" requires all IPv6 traffic to go
to the 6rd Border Relay. In effect, this requirement removes
the "direct connect to 6rd" route defined in Section 7.1.1 of
[RFC5969].
6RD-4: A CE router MUST allow 6rd and native IPv6 WAN interfaces to
be active alone as well as simultaneously in order to support
coexistence of the two technologies during an incremental
migration period such as a migration from 6rd to native IPv6.
6RD-5: Each packet sent on a 6rd or native WAN interface MUST be
directed such that its source IP address is derived from the
delegated prefix associated with the particular interface
from which the packet is being sent (Section 4.3 of
[RFC3704]).
6RD-6: The CE router MUST allow different as well as identical
delegated prefixes to be configured via each (6rd or native)
WAN interface.
6RD-7: In the event that forwarding rules produce a tie between 6rd
and native IPv6, by default, the IPv6 CE router MUST prefer
native IPv6.
4.4.2. Dual-Stack Lite (DS-Lite)
Dual-Stack Lite [RFC6333] enables both continued support for IPv4
services and incentives for the deployment of IPv6. It also
de-couples IPv6 deployment in the service provider network from the
rest of the Internet, making incremental deployment easier. 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). It is
expected that DS-Lite traffic is forwarded over the CE router's
native IPv6 WAN interface, and not encapsulated in another tunnel.
The IPv6 CE router SHOULD implement DS-Lite functionality. If
DS-Lite is supported, it MUST be implemented according to [RFC6333].
This document takes no position on simultaneous operation of Dual-
Stack Lite and native IPv4. The following CE router requirements
also apply:
WAN requirements:
DLW-1: The CE router MUST support configuration of DS-Lite via the
DS-Lite DHCPv6 option [RFC6334]. The IPv6 CE router MAY use
other mechanisms to configure DS-Lite parameters. Such
mechanisms are outside the scope of this document.
DLW-2: The IPv6 CE router MUST NOT perform IPv4 Network Address
Translation (NAT) on IPv4 traffic encapsulated using DS-Lite.
DLW-3: If the IPv6 CE router is configured with an IPv4 address on
its WAN interface, then the IPv6 CE router SHOULD disable the
DS-Lite Basic Bridging BroadBand (B4) element.
4.5. 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 SHOULD support ingress filtering in
accordance with BCP 38 [RFC2827]. Note that this requirement
was downgraded from a MUST from RFC 6204 due to the difficulty
of implementation in the CE router and the feature's redundancy
with upstream router ingress filtering.
S-3: If the IPv6 CE router firewall is configured to filter incoming
tunneled data, the firewall SHOULD provide the capability to
filter decapsulated packets from a tunnel.
5. Acknowledgements
Thanks to the following people (in alphabetical order) for their
guidance and feedback:
Mikael Abrahamsson, Tore Anderson, Merete Asak, Rajiv Asati, Scott
Beuker, Mohamed Boucadair, Rex Bullinger, Brian Carpenter, Tassos
Chatzithomaoglou, Lorenzo Colitti, Remi Denis-Courmont, Gert Doering,
Alain Durand, Katsunori Fukuoka, Brian Haberman, Tony Hain, Thomas
Herbst, Ray Hunter, Joel Jaeggli, 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, Daniel Roesen,
Hiroki Sato, Teemu Savolainen, Matt Schmitt, David Thaler, Mark
Townsley, Sean Turner, Bernie Volz, Dan Wing, Timothy Winters, James
Woodyatt, Carl Wuyts, 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. Thanks to Ole
Troan for editorship in the original RFC 6204 document.
7. References
7.1. Normative References
[RFC1122] Braden, R., "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.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, 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., 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., "DNS Configuration options for Dynamic Host
Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
December 2003.
[RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed
Networks", BCP 84, RFC 3704, March 2004.
[RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol
(DHCP) Service for IPv6", RFC 3736, April 2004.
[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.
[RFC4443] Conta, A., Deering, S., and M. Gupta, "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.
[RFC5072] Varada, S., Haskins, D., and E. Allen, "IP Version 6 over
PPP", RFC 5072, September 2007.
[RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, June 2010.
[RFC5908] Gayraud, R. and B. Lourdelet, "Network Time Protocol (NTP)
Server Option for DHCPv6", RFC 5908, June 2010.
[RFC5942] Singh, H., Beebee, W., and E. Nordmark, "IPv6 Subnet
Model: The Relationship between Links and Subnet
Prefixes", RFC 5942, July 2010.
[RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
Infrastructures (6rd) -- Protocol Specification", RFC
5969, August 2010.
[RFC6092] Woodyatt, J., "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.
[RFC6177] Narten, T., Huston, G., and L. Roberts, "IPv6 Address
Assignment to End Sites", BCP 157, RFC 6177, March 2011.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, August 2011.
[RFC6334] Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite",
RFC 6334, August 2011.
[RFC6434] Jankiewicz, E., Loughney, J., and T. Narten, "IPv6 Node
Requirements", RFC 6434, December 2011.
[RFC6603] Korhonen, J., Savolainen, T., Krishnan, S., and O. Troan,
"Prefix Exclude Option for DHCPv6-based Prefix
Delegation", RFC 6603, May 2012.
[RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
Selkirk, "Port Control Protocol (PCP)", RFC 6887, April
2013.
[RFC7083] Droms, R., "Modification to Default Values of SOL_MAX_RT
and INF_MAX_RT", RFC 7083, November 2013.
7.2. Informative References
[DHCPv6-STATEFUL-ISSUES]
Troan, O. and B. Volz, "Issues with multiple stateful
DHCPv6 options", Work in Progress, May 2013.
[MULTIHOMING-WITHOUT-NAT]
Troan, O., Ed., Miles, D., Matsushima, S., Okimoto, T.,
and D. Wing, "IPv6 Multihoming without Network Address
Translation", Work in Progress, December 2010.
[RFC6144] Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
IPv4/IPv6 Translation", RFC 6144, April 2011.
[TR-069] Broadband Forum, "CPE WAN Management Protocol", TR-069
Amendment 4, July 2011,
<http://www.broadband-forum.org/technical/trlist.php>.
[UPnP-IGD] UPnP Forum, , "InternetGatewayDevice:2 Device Template
Version 1.01", December 2010,
<http://upnp.org/specs/gw/igd2/>.
Authors' Addresses
Hemant Singh
Cisco Systems, Inc.
1414 Massachusetts Ave.
Boxborough, MA 01719
USA
Phone: +1 978 936 1622
EMail: shemant@cisco.com
URI: http://www.cisco.com/
Wes Beebee
Cisco Systems, Inc.
1414 Massachusetts Ave.
Boxborough, MA 01719
USA
Phone: +1 978 936 2030
EMail: wbeebee@cisco.com
URI: http://www.cisco.com/
Chris Donley
CableLabs
858 Coal Creek Circle
Louisville, CO 80027
USA
EMail: c.donley@cablelabs.com
Barbara Stark
AT&T
1057 Lenox Park Blvd. NE
Atlanta, GA 30319
USA
EMail: barbara.stark@att.com