wdiff rfc6879v1.txt rfc6879.txt

Internet Engineering Task Force (IETF) S. Jiang
Request for Comments: 6879 B. Liu
Category: Informational Huawei Technologies Co., Ltd.
ISSN: 2070-1721 B. Carpenter
University of Auckland
February 2013

IPv6 Enterprise Network Renumbering Scenarios,
Considerations, and Methods

Abstract

This document analyzes events that cause renumbering and describes
the current renumbering methods. These are described in three
categories: those applicable during network design, those applicable
during preparation for renumbering, and those applicable during the
renumbering operation.

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/rfc6879.

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 ....................................................2
2. Enterprise Network Illustration for Renumbering .................3
3. Enterprise Network Renumbering Scenario Categories ..............5
3.1. Renumbering Caused by External Network Factors .............5
3.2. Renumbering Caused by Internal Network Factors .............5
4. Network Renumbering Considerations and Current Methods ..........6
4.1. Considerations and Current Methods during Network Design ...6
4.2. Considerations and Current Methods for the
Preparation of Renumbering ................................10
4.3. Considerations and Current Methods during
Renumbering Operation .....................................11
5. Security Considerations ........................................13
6. Acknowledgements ...............................................14
7. References .....................................................14
7.1. Normative References ......................................14
7.2. Informative References ....................................15

1. Introduction

Site renumbering is difficult. Network managers frequently attempt
to avoid future renumbering by numbering their network resources from
Provider-Independent (PI) address space. However, widespread use of
PI address space would aggravate BGP4 scaling problems [RFC4116] and,
depending on Regional Internet Registry (RIR) policies, PI space is
not always available for enterprises of all sizes. Therefore, it is
desirable to develop mechanisms that simplify IPv6 renumbering for
enterprises.

This document is an analysis of IPv6 site renumbering for enterprise
networks. It undertakes scenario descriptions, including
documentation of current capabilities and existing practices. The
reader is assumed to be familiar with [RFC4192] and [RFC5887].
Proposals for new technology and methods are out of scope.

Since IPv4 and IPv6 are logically separate from the perspective of
renumbering, regardless of overlapping of the IPv4/IPv6 networks or
devices, this document focuses on IPv6 only, leaving IPv4 out of
scope. Dual-stack networks or IPv4/IPv6 transition scenarios are out
of scope as well.

This document focuses on enterprise network renumbering; however,
most of the analysis is also applicable to ISP network renumbering.
Renumbering in home networks is out of scope, but it can also benefit
from the analysis in this document.

The concept of an enterprise network and a typical network
illustration are introduced first. Then, current renumbering methods
are introduced according to the following categories: those
applicable during network design, those applicable during preparation
for renumbering, and those applicable during the renumbering
operation.

2. Enterprise Network Illustration for Renumbering

An Enterprise Network, as defined in [RFC4057], is a network that has
multiple internal links, has one or more router connections to one or
more Providers, and is actively managed by a network operations
entity.

Figure 1 provides a sample enterprise network architecture for a
simple case. Those entities mainly affected by renumbering are
illustrated:

* Gateway (Border router, firewall, web cache, etc.)

* Application server (for internal or external users)

* DNS and DHCP servers

* Routers

* Hosts (desktops, etc.)
Uplink 1 Uplink 2
| |
+---+---+ +---+---+
+---- |Gateway| --------- |Gateway| -----+
| +-------+ +-------+ |
| Enterprise Network |
| +------+ +------+ +------+ |
| | APP | |DHCPv6| | DNS | |
| |Server| |Server| |Server| |
| +---+--+ +---+--+ +--+---+ |
| | | | |
| ---+--+---------+------+---+- |
| | | |
| +--+---+ +---+--+ |
| |Router| |Router| |
| +--+---+ +---+--+ |
| | | |
| -+---+----+-------+---+--+- |
| | | | | |
| +-+--+ +--+-+ +--+-+ +-+--+ |
| |Host| |Host| |Host| |Host| |
| +----+ +----+ +----+ +----+ |
+----------------------------------------+

Figure 1. Enterprise Network Illustration

Address reconfiguration is fulfilled either by the Dynamic Host
Configuration Protocol for IPv6 (DHCPv6) or by Neighbor Discovery
(ND) for IPv6 protocols. During a renumbering event, the Domain Name
Service (DNS) records need to be synchronized while routing tables,
Access Control Lists (ACLs), and IP filtering tables in various
devices also need to be updated. It is taken for granted that
applications will work entirely on the basis of DNS names, but any
direct dependencies on IP addresses in application-layer entities
must also be updated.

The issue of static addresses is described in a dedicated draft
[STATIC-PROB]. document
[RFC6866].

The emerging cloud-based enterprise network architecture might be
different than Figure 1. However, it is out of the scope of this
document since it is far from mature and has not been widely deployed
yet.

It is assumed that IPv6 enterprise networks are IPv6-only or dual-
stack in which a logical IPv6 plane is independent from IPv4. As
mentioned above, IPv4/IPv6 coexistence scenarios are out of scope.

This document focuses on routable unicast addresses; link-local,
multicast, and anycast addresses are also out of scope.

3. Enterprise Network Renumbering Scenario Categories

In this section, we divide enterprise network renumbering scenarios
into two categories defined by external and internal network factors,
which require renumbering for different reasons.

3.1. Renumbering Caused by External Network Factors

The following ISP uplink-related events can cause renumbering:

o The enterprise network switches to a new ISP. When this occurs,
the enterprise stops numbering its resources from the prefix
allocated by the old ISP and renumbers its resources from the
prefix allocated by the new ISP.

When the enterprise switches ISPs, a "flag day" renumbering event
[RFC4192] may be averted if, during a transitional period, the
enterprise network may number its resources from either prefix.
One way to facilitate such a transitional period is for the
enterprise to contract service from both ISPs during the
transition.

o The renumbering event can be initiated by receiving new prefixes
from the same uplink. This might happen if the enterprise network
is switched to a different location within the network topology of
the same ISP due to various considerations, such as commercial,
performance or services reasons, etc. Alternatively, the ISP
itself might be renumbered due to topology changes or migration to
a different or additional prefix. These ISP renumbering events
would initiate enterprise network renumbering events, of course.

o The enterprise network adds a new uplink(s) for multihoming
purposes. This might not be a typical renumbering case because
the original addresses will not be changed. However, initial
numbering may be considered as a special renumbering event. The
enterprise network removes uplink(s) or old prefixes.

3.2. Renumbering Caused by Internal Network Factors

o As companies split, merge, grow, relocate, or reorganize, the
enterprise network architectures might need to be rebuilt. This
will trigger partial or total internal renumbering.

o The enterprise network might proactively adopt a new address
scheme, for example, by switching to a new transition mechanism or
stage of a transition plan.

o The enterprise network might reorganize its topology or subnets.

4. Network Renumbering Considerations and Current Methods

In order to carry out renumbering in an enterprise network,
systematic planning and administrative preparation are needed.
Careful planning and preparation could make the renumbering process
smoother.

This section describes current considerations and methods for
enterprise renumbering, chosen among existing mechanisms. There are
known gaps analyzed by [GAP-ANALYSIS] and [STATIC-PROB]. [RFC6866]. If these gaps
are filled in the future, enterprise renumbering could be processed
more automatically, with fewer issues.

4.1. Considerations and Current Methods during Network Design

This section describes the considerations or issues relevant to
renumbering that a network architect should carefully plan when
building or designing a new network.

- Prefix Delegation (PD)

In a large or a multisite enterprise network, the prefix should be
carefully managed, particularly for renumbering events. Prefix
information needs to be delegated from router to router. The DHCPv6
PD options ([RFC3633] and [RFC6603]) provide a mechanism for
automated delegation of IPv6 prefixes. Normally, DHCPv6 PD options
are used between the internal enterprise routers; for example, a
router receives a prefix(es) from its upstream router (a border
gateway or edge router, etc.) through DHCPv6 PD options and then
advertises it (them) to the local hosts through Router Advertisement
(RA) messages.

- Usage of Fully Qualified Domain Names (FQDNs)

In general, FQDNs are recommended to be used to configure network
connectivity, such as tunnels, servers, etc. The capability to use
FQDNs as endpoint names has been standardized in several RFCs (e.g.,
for IPsec [RFC5996]) although many system/network administrators do
not realize that it is there and it works well as a way to avoid
manual modification during renumbering.

Note that using FQDNs would rely on DNS systems. For a link-local
network that does not have a DNS system, multicast DNS [RFC6762]
could be utilized. For some specific circumstances, using FQDNs
might not be chosen if adding DNS service in the node/network would
cause undesired complexity or issues.

Service discovery protocols such as the Service Location Protocol
[RFC2608], multicast DNS with Service Records (SRVs), and DNS Service
Discovery [RFC6763] use names and can reduce the number of places
that IP addresses need to be configured. However, it should be noted
that these protocols are normally used link-local only.

Network designers generally have little control over the design of
application software. However, it is important to avoid any software
that has a built-in dependency on IP addresses instead of FQDNs
[STATIC-PROB].
[RFC6866].

- Usage of Parameterized Address Configuration

Besides DNS records, IP addresses might also be configured in many
other places such as ACLs, various IP filters, various kinds of text-
based configuration files, etc.

In some cases, one IP address can be defined as a value once, and
then the administrators can use either keywords or variables to call
the value in other places such as a sort of internal inheritance CLI
(command line interface) or other local configuration. Among the
real current devices, some routers support defining multiple loopback
interfaces that can be called in other configurations. For example,
when defining a tunnel, it can call the defined loopback interface to
use its address as the local address of the tunnel.

This kind of parameterized address configuration is recommended,
since it makes managing a renumbering event easier by reducing the
number of places where a device's configuration must be updated.

- Usage of Unique Local Addresses (ULAs)

ULAs are defined in [RFC4193] as PI prefixes. Since there is a
40-bit pseudorandom field in the ULA prefix, there is no practical
risk of collision (please refer to Section 3.2.3 in [RFC4193] for
more detail). For enterprise networks, using ULA simultaneously with
PA addresses can provide a logically local routing plane logically separated
from the global routing plane. The benefit is to ensure stable and
specific local communication regardless of any ISP uplink failure.
This benefit is especially meaningful for renumbering. It mainly
includes three use cases described below.

o During the transition period, it is desirable to isolate local
communication changes in the global routing plane. If we use ULA
for the local communication, this isolation is achieved.

o Enterprise administrators might want to avoid the need to renumber
their internal-only, private nodes when they have to renumber the
PA addresses of the whole network because of changing ISPs, ISPs
restructuring their address allocation, or any other reasons. In
these situations, a ULA is an effective tool for the internal-only
nodes.

o ULAs can be a way of avoiding renumbering from having an impact on
multicast. In most deployments, multicast is only used internally
(intra-domain), and the addresses used for multicast sources and
Rendezvous Points need not be reachable nor routable externally.
Hence, one may, at least internally, make use of ULAs for
multicast-specific infrastructure.

- Address Types

This document focuses on the dynamically configured global unicast
addresses in enterprise networks. They are the targets of
renumbering events.

Manually configured addresses are not scalable in medium to large
sites; hence, they should be avoided for both network elements and
application servers [STATIC-PROB]. [RFC6866].

- Address configuration models

In IPv6 networks, there are two autoconfiguration models for address
assignment after each host obtains a link-local address: Stateless
Address Autoconfiguration (SLAAC) [RFC4862] by ND [RFC4861] and
stateful address configuration by DHCPv6 [RFC3315]. In the latest
work, DHCPv6 may also support the host-generated address model by
assigning a prefix through DHCPv6 messages [PREFIX-DHCPV6].

SLAAC is considered to support easy renumbering by broadcasting an RA
message with a new prefix. DHCPv6 can also trigger the renumbering
process by sending unicast RECONFIGURE messages, though it might
cause a large number of interactions between hosts and the DHCPv6
server.

This document has no preference between the SLAAC and DHCPv6 address
configuration models. It is the network architect's job to decide
which configuration model is employed. However, it should be noticed
that using DHCPv6 and SLAAC together within one network, especially
in one subnet, might cause operational issues. For example, some
hosts use DHCPv6 as the default configuration model while some use
ND. Then, the host's address configuration model depends on the
policies of operating systems and cannot be controlled by the
network. Section 5.1 of [GAP-ANALYSIS] discusses more details on
this topic. So, in general, this document recommends using DHCPv6 or
SLAAC independently in different subnets.

However, since DHCPv6 is also used to configure many other network
parameters, there are ND and DHCPv6 coexistence scenarios.
Combinations of address configuration models might coexist within a
single enterprise network. [SAVI] provides recommendations to avoid
collisions and to review collision handling in such scenarios.

- DNS

Although the A6 DNS record model [RFC2874] was designed for easier
renumbering, it left many unsolved technical issues [RFC3364].
Therefore, it has been moved to Historic status [RFC6563] and should
not be used.

Often, a small site depends on its ISP's DNS system rather than
maintaining its own. When renumbering, this requires administrative
coordination between the site and its ISP.

It is recommended that the site have an automatic and systematic
procedure for updating/synchronizing its DNS records, including both
forward and reverse mapping. In order to simplify the operational
procedure, the network architect should combine the forward and
reverse DNS updates in a single procedure. A manual on-demand
updating model does not scale and increases the chance of errors.
Either a database-driven mechanism, a secure dynamic DNS update
[RFC3007], or both could be used.

A dynamic DNS update can be provided by the DHCPv6 client or by the
server on behalf of individual hosts. [RFC4704] defines a DHCPv6
option to be used by DHCPv6 clients and servers to exchange
information about the client's FQDN and about who has the
responsibility for updating the DNS with the associated AAAA and PTR
(Pointer Record) RRs (Resource Records). For example, if a client
wants the server to update the FQDN-address mapping in the DNS
server, it can include the Client FQDN option with proper settings in
the SOLICIT with Rapid Commit, REQUEST, RENEW, and REBIND message
originated by the client. When the DHCPv6 server gets this option,
it can use a secure dynamic DNS update on behalf of the client. This
document suggests use of this FQDN option. However, since it is a
DHCPv6 option, only the DHCP-managed hosts can make use of it. In
SLAAC mode, hosts need either to use a secure dynamic DNS update
directly, or to register addresses on a registration server. This
could in fact be a DHCPv6 server (as described in [ADDR-REG]); then
the server would update corresponding DNS records.

- Security

Any automatic renumbering scheme has a potential exposure to
hijacking. A malicious entity in the network could forge prefixes to
renumber the hosts, so proper network security mechanisms are needed.
Further details are in the Security Considerations section below.

- Miscellaneous

A site or network should also avoid embedding addresses from other
sites or networks in its own configuration data. Instead, the FQDNs
should be used. Thus, connections can be restored after renumbering
events at other sites. This also applies to host-based connectivity.

4.2. Considerations and Current Methods for the Preparation of
Renumbering

In ND, it is not possible to reduce a prefix's lifetime to below two
hours. So, renumbering should not be an unplanned sudden event.
This issue could only be avoided by early planning and preparation.

This section describes several recommendations for the preparation of
an enterprise renumbering event. By adopting these recommendations,
a site could be renumbered more easily. However, these
recommendations might increase the daily traffic, server load, or
burden of network operation. Therefore, only those networks that are
expected to be renumbered soon, or very frequently, should adopt
these recommendations, with balanced consideration between daily cost
and renumbering cost.

- Reduce the address preferred time or valid time or both

Long-lifetime addresses might cause issues for renumbering events.
Particularly, some offline hosts might reconnect using these
addresses after renumbering events. Shorter, preferred lifetimes
with relatively long valid lifetimes may allow short transition
periods for renumbering events and avoid frequent address renewals.

- Reduce the DNS record Time to Live (TTL) on the local DNS server

The DNS AAAA RR TTL on the local DNS server should be manipulated to
ensure that stale addresses are not cached.

Recent research [BA2011] [JSBM2002] indicates that it is both
practical and reasonable for A, AAAA, and PTRs that belong to leaf
nodes of the DNS (i.e., not including the DNS root or DNS top-level
domains) to be configured with very short DNS TTL values, not only
during renumbering events but also for longer-term operation.

- Reduce the DNS configuration lifetime on the hosts

Since the DNS server could be renumbered as well, the DNS
configuration lifetime of the hosts should also be reduced if
renumbering events are expected. In ND, the DNS configuration can be
done through reducing the lifetime value in the Recursive DNS Server
(RDNSS) option [RFC6106]. In DHCPv6, the DNS configuration option
specified in [RFC3646] doesn't provide a lifetime attribute, but we
can reduce the DHCPv6 client lease time to achieve a similar effect.

- Identify long-living sessions

Any applications that maintain very long transport connections (hours
or days) should be identified in advance, if possible. Such
applications will need special handling during renumbering, so it is
important to know that they exist.

4.3. Considerations and Current Methods during Renumbering Operation

Renumbering events are not instantaneous events. Normally, there is
transition period in which both the old prefix and the new prefix are
used in the site. Better network design and management, better pre-
preparation, and a longer transition periods period are helpful to reduce the
issues during a renumbering operation.

- Within/Without a flag day

As is described in [RFC4192] "a 'flag day' is a procedure in which
the network, or a part of it, is changed during a planned outage, or
suddenly, causing an outage while the network recovers".

If a renumbering event is processed within a flag day, the network
service/connectivity will be unavailable for a period until the
renumbering event is completed. It is efficient and provides
convenience for network operation and management. However, a network
outage is usually unacceptable for end users and enterprises. A
renumbering procedure without a flag day provides smooth address
switching, but much more operational complexity and difficulty is
introduced.

- Transition period

If a renumbering transition period is longer than all address
lifetimes, after which the address leases expire, each host will
automatically pick up its new IP address. In this case, it would be
the DHCPv6 server or RA itself that automatically accomplishes client
renumbering.

Address deprecation should be associated with the deprecation of
associated DNS records. The DNS records should be deprecated as
early as possible, before the addresses themselves.

- Network initiative enforced renumbering

If the network has to enforce renumbering before address leases
expire, the network should initiate DHCPv6 RECONFIGURE messages. For
some operating systems such as Windows 7, if the hosts receive RA
messages with ManagedFlag=0, they will release the DHCPv6 addresses
and utilize SLAAC according to the prefix information in the RA
messages, so this could be another enforcement method for some
specific scenarios.

- Impact to branch/main on main and branch sites

Renumbering in the main/branch main site might cause impact on branch/main branch site communications.
communications, and vice versa. The routes, ingress filtering of the
site's gateways, and DNS might need to be updated. This needs
careful planning and organizing.

- DNS record update and DNS configuration on hosts

DNS records on the local DNS server should be updated if hosts are
renumbered. If the site depends on an ISP's DNS system, it should
report the new hosts' DNS records to its ISP. During the transition
period, both old and new DNS records are valid. If the TTLs of DNS
records are shorter than the transition period, an administrative
operation might not be necessary.

DNS configuration on hosts should be updated if local recursive DNS
servers are renumbered. During the transition period, both old and
new DNS server addresses might coexist on the hosts. If the lifetime
of DNS configuration is shorter than the transition period, name
resolving failure may be reduced to a minimum.

- Tunnel concentrator renumbering

A tunnel concentrator itself might be renumbered. This change should
be reconfigured in relevant hosts or routers, unless the
configuration of the tunnel concentrator was based on FQDN.

For IPsec, Internet Key Exchange Protocol version 2 (IKEv2) [RFC5996]
defines the ID_FQDN Identification type, which could be used to
identify an IPsec VPN concentrator associated with a site's domain
name. For current practice, the community needs to change its bad
habit of using IPsec in an address-oriented way, and renumbering is
one of the main reasons for that.

- Connectivity session survivability

During the renumbering operations, connectivity sessions in the IP
layer would break if the old address is deprecated before the session
ends. However, the upper-layer sessions can survive by using session
survivability technologies, such as Stanza Headers and Internet
Metadata 6 (SHIM6) [RFC5533]. As mentioned above, some long-living
applications may need to be handled specially.

- Verification of success

The renumbering operation should end with a thorough check that all
network elements and hosts are using only the new prefixes and that
network management and monitoring systems themselves are still
operating correctly. A database clean up may also be needed.

5. Security Considerations

Any automatic renumbering scheme has a potential exposure to
hijacking by an insider attack. For attacks on ND, SEcure Neighbor
Discovery (SEND) [RFC3971] is a possible solution, but it is complex
and there is almost no real deployment at the time of writing.
Compared to the nontrivial deployment of SEND, RA-Guard [RFC6105] is
a lightweight alternative that focuses on preventing rogue router
advertisements in a network. However, it is also not widely deployed
at the time when this memo was published.

For DHCPv6, there are built-in secure mechanisms (like Secure DHCPv6
[SECURE-DHCPV6]), and authentication of DHCPv6 messages [RFC3315]
could be utilized. However, these security mechanisms also have not
been verified by widespread deployment at the time of writing.

A site that is listed by IP address in a blacklist can escape that
list by renumbering itself. However, the new prefix might be back on
a blacklist rather soon if the root cause for being added to such a
list is not corrected. In practice, the cost of renumbering will
typically be much larger than the cost of getting off the blacklist.

A Dynamic DNS update might bring risk of a Denial-of-Service (DoS)
attack to the DNS server. So, along with the update authentication,
session filtering/limitation might also be needed.

The "make-before-break" approach of [RFC4192] requires the routers to
keep advertising the old prefixes for some time. However, if the ISP
changes the prefixes very frequently, the coexistence of old and new
prefixes might cause potential risk to the enterprise routing system,
since the old address relevant route path might already be invalid
and the routing system just doesn't know it. However, normally,
enterprise scenarios don't involve this extreme situation.

6. Acknowledgements

This work is inspired by RFC 5887; thank you to the authors (Randall
Atkinson and Hannu Flinck). Useful ideas were also presented in
documents by Tim Chown and Fred Baker. The authors also want to
thank Wesley George, Olivier Bonaventure, Lee Howard, Ronald Bonica,
other 6renum members, and several reviewers for their valuable
comments.

7. References

7.1. Normative References

[RFC2608] Guttman, E., Perkins, C., Veizades, J., and M. Day,
"Service Location Protocol, Version 2", RFC 2608, June
1999.

[RFC3007] Wellington, B., "Secure Domain Name System (DNS) Dynamic
Update", RFC 3007, November 2000.

[RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
C., and M. Carney, "Dynamic Host Configuration Protocol
for IPv6 (DHCPv6)", RFC 3315, July 2003.

[RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
Host Configuration Protocol (DHCP) version 6", RFC 3633,
December 2003.

[RFC3646] Droms, R., Ed., "DNS Configuration options for Dynamic
Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
December 2003.

[RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
"SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005.

[RFC4057] Bound, J., Ed., "IPv6 Enterprise Network Scenarios", RFC
4057, June 2005.

[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005.

[RFC4704] Volz, B., "The Dynamic Host Configuration Protocol for
IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN)
Option", RFC 4704, October 2006.

[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.

[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol Version 2 (IKEv2)", RFC
5996, September 2010.

[RFC6106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
"IPv6 Router Advertisement Options for DNS
Configuration", RFC 6106, November 2010.

7.2. Informative References

[RFC2874] Crawford, M. and C. Huitema, "DNS Extensions to Support
IPv6 Address Aggregation and Renumbering", RFC 2874, July
2000.

[RFC3364] Austein, R., "Tradeoffs in Domain Name System (DNS)
Support for Internet Protocol version 6 (IPv6)", RFC
3364, August 2002.

[RFC4116] Abley, J., Lindqvist, K., Davies, E., Black, B., and V.
Gill, "IPv4 Multihoming Practices and Limitations", RFC
4116, July 2005.

[RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for
Renumbering an IPv6 Network without a Flag Day", RFC
4192, September 2005.

[RFC5533] Nordmark, E. and M. Bagnulo, "Shim6: Level 3 Multihoming
Shim Protocol for IPv6", RFC 5533, June 2009.

[RFC5887] Carpenter, B., Atkinson, R., and H. Flinck, "Renumbering
Still Needs Work", RFC 5887, May 2010.

[RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and
J. Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105,
February 2011.

[RFC6563] Jiang, S., Conrad, D., and B. Carpenter, "Moving A6 to
Historic Status", RFC 6563, March 2012.

[RFC6603] Korhonen, J., Ed., Savolainen, T., Krishnan, S., and O.
Troan, "Prefix Exclude Option for DHCPv6-based Prefix
Delegation", RFC 6603, May 2012.

[RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
February 2013.

[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, February 2013.

[SECURE-DHCPV6]
Jiang, S.,

[RFC6866] Carpenter, B., and S. Shen, "Secure DHCPv6 Using CGAs", Work
in Progress, March 2012.

[PREFIX-DHCPV6] Jiang, S., Xia, F., and B. Sarikaya, "Prefix Assignment
in DHCPv6", Work "Problem Statement for
Renumbering IPv6 Hosts with Static Addresses in Progress,
Enterprise Networks", RFC 6866, February 2013.

[SAVI] Bi, J., Yao, G., Halpern, J., and E. Levy-Abegnoli, "SAVI
for Mixed Address Assignment Methods Scenario", Work in
Progress, November 2012.

[ADDR-REG]
Jiang, S., Chen, G., and S. Krishnan "A Generic IPv6
Addresses Registration Solution Using DHCPv6", Work in
Progress, February 2013.

[BA2011] S. Bhatti, and R. Atkinson, "Reducing DNS Caching", Proc.
14th IEEE Global Internet Symposium (GI2011), Shanghai,
China, April 15 2011.

[GAP-ANALYSIS]
Liu, B., Jiang, S., Carpenter, B. Venaas, S., and W.
George, "IPv6 Site Renumbering Gap Analysis", Work in
Progress, December 2012.

[STATIC-PROB]
Carpenter, B., and S. Jiang, "Problem Statement for
Renumbering IPv6 Hosts with Static Addresses in
Enterprise Networks", Work in Progress, December 2012.

[BA2011] S. Bhatti, and R. Atkinson, "Reducing DNS Caching", Proc.
14th IEEE Global Internet Symposium (GI2011), Shanghai,
China, April 15 2011.

[JSBM2002]
J. Jung, E. Sit, H. Balakrishnan, and R. Morris, "DNS
Performance and the Effectiveness of Caching", IEEE/ACM
Transactions on Networking, 10(5):589-603, 2002.

[PREFIX-DHCPV6]
Jiang, S., Xia, F., and B. Sarikaya, "Prefix Assignment
in DHCPv6", Work in Progress, February 2013.

[SAVI] Bi, J., Yao, G., Halpern, J., and E. Levy-Abegnoli, "SAVI
for Mixed Address Assignment Methods Scenario", Work in
Progress, November 2012.

[SECURE-DHCPV6]
Jiang, S., and S. Shen, "Secure DHCPv6 Using CGAs", Work
in Progress, March 2012.

Authors' Addresses

Sheng Jiang
Huawei Technologies Co., Ltd.
Q14, Huawei Campus
No.156 Beiqing Rd.
Hai-Dian District, Beijing 100095
P.R. China

EMail: jiangsheng@huawei.com

Bing Liu
Huawei Technologies Co., Ltd.
Q14, Huawei Campus
No.156 Beiqing Rd.
Hai-Dian District, Beijing 100095
P.R. China

EMail: leo.liubing@huawei.com

Brian Carpenter
Department of Computer Science
University of Auckland
PB 92019
Auckland, 1142
New Zealand

EMail: brian.e.carpenter@gmail.com