Internet DRAFT - draft-gmann-homenet-relay-autoconf
draft-gmann-homenet-relay-autoconf
Network Working Group C. Grundemann
Internet-Draft C. Donley
Intended status: Informational CableLabs
Expires: September 13, 2012 March 12, 2012
Home Network Autoconfiguration via DHCPv6 Relay
draft-gmann-homenet-relay-autoconf-01
Abstract
This document describes a method for efficiently delegating subnets
of an IPv6 prefix among home routers while simultaneously creating
functional routing tables in all home routers without the need for a
routing protocol.
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].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on September 13, 2012.
Copyright Notice
Copyright (c) 2012 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
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carefully, as they describe your rights and restrictions with respect
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Expected Home Network Topologies . . . . . . . . . . . . . . . 3
3. Home Router Behavior . . . . . . . . . . . . . . . . . . . . . 4
3.1. CER Behavior . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. IR Behavior . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Home Router Provisioning Example . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
8. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
There are several mechanisms for distributing IPv6 address and
routing information within a home network. However, many of these
require complex new protocols, or hierarchical addressing topologies.
A simpler and more efficient solution to home network
autoconfiguration is to provide centralized prefix delegation
control, utilize an existing protocol [RFC3315], and remove the need
for a routing protocol. This simpler approach can be achieved by
relaying all DHCPv6 IA_PD [RFC3633] requests and responses to and
from the CPE Edge Router (CER) and snooping their contents along the
way. This approach is analogous to how many Service Providers plan
to distribute IPv6 prefixes to subscribers in the WAN.
2. Expected Home Network Topologies
It is expected that home networks will be arbitrarily constructed by
home users. Figure 1 illustrates an example multi-router home
network topology.
This document assumes that the vast majority of home networks will
connect to a single ISP and will be generally constructed in a tree
architecture. This document also assumes that IPv6 hosts are capable
of dealing with multiple IPv6 addresses and have some manner of
address selection functionality (internal multi-homing).
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+-------+-------+ \
| Service | \
| Provider | | Service
| Router | | Provider
+-------+-------+ | network
| /
| Customer /
| Internet connection
|
+------+--------+ \
| IPv6 | \
| Customer Edge | \
| Router | |
+----+-+---+----+ |
Network A | | | Network B/E |
----+-------------+----+ | +---+-------------+------+ |
| | | | | | | |
+----+-----+ +-----+----+ | +----+-----+ +-----+----+ | |
|IPv6 Host | |IPv6 Host | | | IPv6 Host| |IPv6 Host | | |
| | | | | | | | | | |
+----------+ +----------+ | +----------+ +----------+ | |
| | | | |
| ---+------+------+-----+ |
| | Network B/E |
+------+--------+ | | End-User
| IPv6 | | | networks
| Interior +------+ |
| Router | |
+---+-------+---+ |
Network C | | Network D |
----+-------------+---+- --+---+-------------+--- |
| | | | |
+----+-----+ +-----+----+ +----+-----+ +-----+----+ |
|IPv6 Host | |IPv6 Host | | IPv6 Host| |IPv6 Host | |
| | | | | | | | /
+----------+ +----------+ +----------+ +----------+ /
Figure 1
3. Home Router Behavior
All routers within a home MUST be capable of determining whether or
not they are the CER for their home. This document recommends use of
the CER_ID [I-D.donley-dhc-cer-id-option] but other methods may also
be used.
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3.1. CER Behavior
Once a home router has determined that it is the CER, it is
responsible for requesting, receiving and sub-delegating a GUA prefix
from the ISP [RFC6204], [I-D.ietf-v6ops-6204bis].
Once the CER obtains a GUA prefix, it responds to all DHCPv6 requests
on its LAN interface. The CER MUST add a route to its routing table
mapping each delegated prefix to the DHCP client or DHCP relay to
which it was sent.
3.2. IR Behavior
Once a home router has determined that it is an Internal Router (IR)
(e.g. via receipt of the DHCP CER ID Option
[I-D.donley-dhc-cer-id-option] specifying a different router as CER)
and received an IA_PD, the IR MUST relay DHCPv6 IA_PD requests
[RFC3633] received on its LAN interface to the delegating router or
relay agent from which it received its IA_PD.
The IR MUST prefer its CER as its default router when directly
connected and MUST install an entry for IA_PD observed in DHCPv6
Relay message in its routing and forwarding tables. This behavior is
referred to as 'DHCP snooping'. When installing an entry in the
routing and forwarding tables for the observed IA_PD assignments, the
IR MUST map the IA_PD to the IR transmitting the request. The IR
MUST purge the IA_PD entry and the route to the prefix upon IA_PD
lease expiration.
4. Home Router Provisioning Example
1. CER Receives a GUA and IA_PD from the ISP.
2. CER configures a /64 on its LAN interface(s) and advertises
itself as a default router candidate in its RA.
3. Directly attached internal routers (Level 1 IRs) install a
default router based on RAs received from the CER and initiate
SLAAC when appropriate. When multiple default routers are
advertised, L1 IRs will choose the default router that matches
the received CER_ID whenever possible.
4. Level 1 IRs initiate DHCPv6 with CER.
A. Requests include IA_PD and CER_ID options, and may include
an IA_NA.
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B. The CER responds to the IR with an IA_PD (e.g. /64), a
CER_ID that contains the CER's LAN IP, and IA_NA when
applicable.
5. The CER records to which IR each delegated prefix is distributed
and construct its routing and forwarding tables accordingly
[RFC3633].
6. Level 1 IRs (L1IRs) advertise themselves as default router
candidates via their RAs and indicate whether DHCPv6 information
is available.
7. Indirectly attached (e.g. Level 2) IRs install a default router
based on RAs received from directly upstream IR(s) and initiate
SLAAC when appropriate.
8. Indirectly attached IRs initiate DHCPv6.
A. Requests include IA_PD and CER_ID options, and may include
an IA_NA.
B. The directly upstream IR responds with: CER_ID that contains
the CER's LAN IP, and IA_NA when applicable.
C. The directly attached IR relays the IA_PD request to the
delegating router or relay from which it obtained its IA_PD.
D. The CER responds to the IA_PD request with an IR IPv6 Prefix
(e.g. /64).
E. This response is relayed back to the IR via one or more
relays.
9. The CER records the IR or DHCPv6 relay to which the delegated
prefix is distributed and uses the mapping to build its routing
and forwarding tables.
10. IRs inspect the contents of all relayed IA_PD response and
record both the prefix contained and IR/downstream DHCPv6 relay
the message is sent to. These prefix/address tuples are used to
construct local routing and forwarding tables.
11. Indirectly attached IRs advertise themselves as default router
candidates via their RAs and indicate whether DHCPv6 information
is available.
12. Repeat steps 7 through 10 as needed.
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5. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
6. Security Considerations
TBD
7. Acknowledgements
TBD
8. Normative References
[I-D.donley-dhc-cer-id-option]
Donley, C. and C. Grundemann, "Customer Edge Router
Identification Option", draft-donley-dhc-cer-id-option-00
(work in progress), March 2012.
[I-D.ietf-v6ops-6204bis]
Stark, B., Donley, C., Singh, H., Troan, O., and W.
Beebee, "Basic Requirements for IPv6 Customer Edge
Routers", draft-ietf-v6ops-6204bis-05 (work in progress),
December 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[RFC6204] Singh, H., Beebee, W., Donley, C., Stark, B., and O.
Troan, "Basic Requirements for IPv6 Customer Edge
Routers", RFC 6204, April 2011.
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Authors' Addresses
Chris Grundemann
CableLabs
858 Coal Creek Cir
Louisville, CO 80027
US
Email: c.grundemann@cablelabs.com
Chris Donley
CableLabs
858 Coal Creek Cir
Louisville, CO 80027
US
Email: c.donley@cablelabs.com
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