Internet Engineering Task Force H. Singh
Internet-Draft W. Beebee
Intended status: Informational Cisco Systems, Inc.
Expires: June 21, 2010 C. Donley
CableLabs
B. Stark
AT&T
O. Troan, Ed.
Cisco Systems, Inc.
December 18, 2009
Basic Requirements for IPv6 Customer Edge Routers
draft-ietf-v6ops-ipv6-cpe-router-03
Abstract
This document specifies requirements for an IPv6 Customer Edge (CE)
router. Specifically, the current version of this document focuses
on the provisioning of an IPv6 CE router and the provisioning of IPv6
hosts attached to it.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
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This Internet-Draft will expire on June 21, 2010.
Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the
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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 BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
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 . . . . . . . . . . . . 5
4. Use Cases and Requirements . . . . . . . . . . . . . . . . . . 6
4.1. WAN side configuration . . . . . . . . . . . . . . . . . . 6
4.2. LAN side configuration . . . . . . . . . . . . . . . . . . 8
4.3. General requirements . . . . . . . . . . . . . . . . . . . 9
4.4. Security Considerations . . . . . . . . . . . . . . . . . 10
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Normative References . . . . . . . . . . . . . . . . . . . . . 11
Appendix A. Changes in revision 3 . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
This document defines IPv6 features for a residential or small office
router referred to as an IPv6 CE router. Typically these routers
also support IPv4.
This document specifies how an IPv6 CE router automatically
provisions its WAN interface, acquires an address block 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 which 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 Internet 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 a company that offers its customers access to
the Internet. In this document, a Service
Provider specifically offers Internet access
using IPv6, and may also offer IPv4 Internet
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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, X.25,
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 have to 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 which has
implications for the network architecture. A typical IPv4 end-user
network consist of a "plug and play" NAT box connected to the ISP.
The assumption is a single NAT device with a single link behind it.
The NAT provides stable addressing allowing for manually configured
addresses on the nodes in the end-user network.
A typical IPv4 NAT deployment by default blocks all incoming
connections. Opening of ports is typically allowed using UPnP 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 ISPs, 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 multi-homing; even though using NATs for multi-homing
does not preserve connections during fail-overs [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.
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3.2. IPv6 end-user network architecture
The end-user network architecture for IPv6 should provide equivalent
or better capabilities and functionality than the equivalent IPv4
architecture.
The end-user network is a stub network. Figure 1 illustrates the
model topology for the end-user network.
An example of a typical end-user network.
+-------+-------+ \
| Service | \
| Provider | | ISP
| Router | | network
+-------+-------+ |
| /
| Customer /
| Internet connection /
|
+------+--------+ \
| IPv6 | \
| Customer Edge | \
| Router | /
+---+-------+-+-+ /
Network A | | Network B | Customer
---+-------------+----+- --+--+-------------+--- |network(s)
| | | | \
+----+-----+ +-----+----+ +----+-----+ +-----+----+ \
|IPv6 Host | |IPv6 Host | | IPv6 Host| |IPv6 Host | /
| | | | | | | | /
+----------+ +-----+----+ +----------+ +----------+/
Figure 1
This architecture describes the:
o Basic capabilities of an IPv6 CE router
o Provisioning of the WAN interface connecting to the ISP
o Provisioning of the LAN interfaces
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.
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For IPv6 multicast traffic the IPv6 CE router may act as an MLD proxy
[RFC4605] and may support a dynamic multicast routing protocol.
IPv6 CE router may be manually configured in an arbitrary topology
with a dynamic routing protocol. Automatic provisioning and
configuration is described for a single IPv6 CE router only.
4. Use Cases and Requirements
4.1. 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 supports all commonly used architectures.
IPv6 Neighbor Discovery and DHCP 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 PPP IPCP for IPv4. This section makes the assumption
that the same mechanism will work for any link-layer, be it Ethernet,
DOCSIS, PPP/PPPoE or others.
When the router is attached to the WAN interface link it must act as
an IPv6 host for the purposes of stateless or stateful interface
address assignment ([RFC4862]/[RFC3315]). The router acts as a
requesting router for the purposes of DHCP prefix delegation
([RFC3633]).
DHCP address assignment (IA_NA) and DHCP prefix delegation (IA_PD)
should be done as a single DHCP session.
Link-layer requirements:
WLL-1: The IPv6 CE router MUST support IPv6 over Ethernet [RFC2464].
WLL-2: The IPv6 CE router MUST support IPv6 over PPP [RFC5072] and
PPPoE [RFC2516]. In a dual-stack environment with IPCP and
IPV6CP running over one PPP logical channel, the NCPs MUST be
treated as independent of each other and start and terminate
independently.
Address assignment requirements:
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WAA-1: The IPv6 CE router MUST support SLAAC [RFC4862].
WAA-2: The IPv6 CE router MUST follow the recommendation in
[I-D.ietf-6man-ipv6-subnet-model] and in particular the
handling of the L-bit in the Router Advertisement Prefix
Information Option.
WAA-3: The IPv6 CE router MUST support DHCP [RFC3315] client
behavior. It MUST be able to support the following DHCP
options: IA_NA, Reconfigure Accept [RFC3315], DNS_SERVERS
[RFC3646].
WAA-4: The IPv6 CE router SHOULD support the DHCP SNTP option
[RFC4075] and the Information Refresh Time Option [RFC4242].
WAA-5: If the IPv6 CE router receives an RA message (described in
[RFC4861]) with the M-bit set to 1, the IPv6 CE router MUST
do DHCP address assignment (request an IA_NA option). If the
IPv6 CE router is unable to assign an address through SLAAC
it MAY do DHCP address assignment (request an IA_NA) even if
the M-bit is set to 0.
WAA-6: If the IPv6 CE router does not acquire a global IPv6 address
from either SLAAC or DHCP, then it MUST create a global IPv6
address from its delegated prefix and configure that on one
of its internal virtual network interfaces. As a router the
IPv6 CE router follows the weak host model [RFC1122] and when
originating packets out the WAN-interface will use a suitably
scoped source address from one of its other interfaces.
Prefix Delegation requirements:
WPD-1: The IPv6 CE router MUST support DHCP prefix delegation
requesting router behavior as specified in [RFC3633] (IA_PD
option). The IPv6 CE router MUST ask for a prefix large
enough to cover all of its LAN interfaces.
WPD-2: The IPv6 CE router MUST always initiate DHCP prefix
delegation, regardless of the M and O-bits in a received
Router Advertisement. If the IPv6 CE Router initiates DHCP
before receiving a Router Advertisement it MUST also request
an IA_NA option in DHCP.
WPD-3: Absent of other routing information the IPv6 CE router MUST
use Router Discovery as specified in [RFC4861] to discover a
default router and install a default route in its routing
table with the discovered router's address as the next-hop.
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WPD-4: If the delegated prefix is an aggregate route of multiple,
more-specific routes the IPv6 CE router MUST discard packets
that match the aggregate route, but not any of the more-
specific routes. In other words, the "next-hop" for the
aggregate route should be the null destination. This is
necessary to prevent forwarding loops when some addresses
covered by the aggregate are not reachable [RFC4632]. The
IPv6 CE Router SHOULD send an ICMPv6 Destination Unreachable
according to section 3.1 [RFC4443] back to the source of the
packet if the packet is to be dropped due to this rule.
WPD-5: If the IPv6 CE router requests both an IA_NA and an IA_PD in
DHCP, it MUST accept an IA_PD in DHCP Advertise/Reply
messages, even if the message does not contain any addresses
(IA_NA options with status code NoAddrsAvail).
WPD-6: An IPv6 CE router MUST not by default initiate any dynamic
routing protocol on its WAN interface.
4.2. 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 will be expected to support an IPv6 end-user
network and IPv6 hosts that exhibit the following characteristics:
1. Link-local addresses are 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 will be capable of using SLAAC and may be capable of
using DHCP for acquiring their addresses.
3. IPv6 hosts will use DHCP for other configuration information,
such as the DNS_SERVERS option for acquiring DNS information.
Unless otherwise specified these requirements only apply to the IPv6
CE router's LAN interfaces.
Requirements:
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L-1: The IPv6 CE router MUST support ULA addressing [RFC4193].
L-2: The IPv6 CE router MUST have a ULA prefix that it maintains
consistently across reboots. The value of the ULA prefix
SHOULD be user configurable.
L-3: The IPv6 CE router by default 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.
L-4: The IPv6 CE router MUST support router behavior of Neighbor
Discovery for IPv6 [RFC4861].
L-5: The IPv6 CE router MUST assign a separate /64 from its
delegated prefix (and ULA prefix if configured to provide ULA
addressing) for each of its LAN interfaces. The IPV6 CE
router MUST make the interface an advertising interface
according to [RFC4861]. In router advertisements messages,
the Prefix Information Option's A/L-bits MUST be set to 1 by
default; the A/L bits setting SHOULD be user configurable.
L-6: The IPv6 CE router MUST support a DHCP server [RFC3315] on its
LAN interfaces. It MAY support Stateless Dynamic Host
Configuration Protocol (DHCP) Service for IPv6 [RFC3736].
L-7: The IPv6 CE SHOULD support DHCP address assignment (IA_NA)
[RFC3315].
L-8: Unless the IPv6 CE router is configured to support the DHCP
IA_NA option, it SHOULD set M=0 and O=1 in its Router
Advertisement messages [RFC4861].
L-9: The IPv6 CE router MUST support providing DNS information in
the DHCP DNS_SERVERS option [RFC3646].
L-10: The IPv6 CE router SHOULD pass the additional set of DHCP
options received from the DHCP client on its WAN interface
from the Service Provider to IPv6 hosts.
4.3. 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,
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and does not originate from the WAN interface.
An IPv6 CE router is an IPv6 node according to the IPv6 Node
Requirements [RFC4294] specification.
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.
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 should support basic stateless egress and ingress
filters. The CE router should also 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
[I-D.ietf-v6ops-cpe-simple-security].
S-2: The IPv6 CE router MUST support ingress filtering in accordance
with [RFC2827](BCP 38)
5. Acknowledgements
Thanks to the following people (in alphabetical order) for their
guidance and feedback:
Mikael Abrahamsson, Merete Asak, Scott Beuker, Rex Bullinger, Brian
Carpenter, Remi Denis-Courmont, Alain Durand, Katsunori Fukuoka, Tony
Hain, Thomas Herbst, Kevin Johns, Stephen Kramer, Victor Kuarsingh,
Francois-Xavier Le Bail, David Miles, Shin Miyakawa, Jean-Francois
Mule, Michael Newbery, Carlos Pignataro, John Pomeroy, Antonio
Querubin, Teemu Savolainen, Matt Schmitt, Hiroki Sato, Mark Townsley,
Bernie Volz, James Woodyatt, Dan Wing and Cor Zwart
This draft 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
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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. IANA Considerations
This memo includes no request to IANA.
8. Normative References
[I-D.ietf-6man-ipv6-subnet-model]
Singh, H., Beebee, W., and E. Nordmark, "IPv6 Subnet
Model: the Relationship between Links and Subnet
Prefixes", draft-ietf-6man-ipv6-subnet-model-06 (work in
progress), November 2009.
[I-D.ietf-v6ops-cpe-simple-security]
Woodyatt, J., "Recommended Simple Security Capabilities in
Customer Premises Equipment for Providing Residential IPv6
Internet Service", draft-ietf-v6ops-cpe-simple-security-08
(work in progress), October 2009.
[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.
[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Networks", RFC 2464, December 1998.
[RFC2516] Mamakos, L., Lidl, K., Evarts, J., Carrel, D., Simone, D.,
and R. Wheeler, "A Method for Transmitting PPP Over
Ethernet (PPPoE)", RFC 2516, February 1999.
[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.
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[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.
[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.
[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., "IPv6 Node Requirements", RFC 4294,
April 2006.
[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.
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[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] S.Varada, Haskins, D., and E. Allen, "IP Version 6 over
PPP", RFC 5072, September 2007.
Appendix A. Changes in revision 3
o Added "the CPE Router SHOULD send an ICMPv6 Destination
Unreachable ([RFC4443] section 3.1) back to the source of the
packet if the packet is to be dropped due to aggregate null
route."
o Clarified that if IPV6CP and IPCP run over the same PPP session
they should be treated independently.
o Removed RFC2460 in the section of RFCs that SHOULD be supported.
o Clarified that the router acts as a host for the purposes of
address assignment. Not for any other ND function e.g Redirects.
o Improved default router selection / default route RIB insertion
text.
o Added text describing that the weak host model has to be supported
in the unnumbered WAN case.
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/
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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
725 W Peachtree St
Atlanta, GA 30308
USA
Email: barbara.stark@att.com
Ole Troan (editor)
Cisco Systems, Inc.
Veversmauet 8
N-5017 BERGEN,
Norway
Phone:
Email: ot@cisco.com
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