One document matched: draft-ietf-v6ops-enterprise-incremental-ipv6-06.xml
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<rfc category="info" docName="draft-ietf-v6ops-enterprise-incremental-ipv6-06"
ipr="trust200902">
<!-- ***** FRONT MATTER ***** -->
<front>
<title abbrev="Enterprise IPv6 Deployment">Enterprise IPv6 Deployment
Guidelines</title>
<author fullname="Kiran K. Chittimaneni" initials="K"
surname="Chittimaneni">
<organization>Dropbox Inc.</organization>
<address>
<postal>
<street>1600 Amphitheater Pkwy</street>
<city>Mountain View, California</city>
<country>USA</country>
<code>CA 94043</code>
</postal>
<email>kk@dropbox.com</email>
</address>
</author>
<author fullname="Tim Chown" initials="T.J." surname="Chown">
<organization>University of Southampton</organization>
<address>
<postal>
<street>Highfield</street>
<city>Southampton</city>
<code>SO17 1BJ</code>
<region>Hampshire</region>
<country>United Kingdom</country>
</postal>
<email>tjc@ecs.soton.ac.uk</email>
</address>
</author>
<author fullname="Lee Howard" initials="L" surname="Howard">
<organization>Time Warner Cable</organization>
<address>
<postal>
<street>13820 Sunrise Valley Drive</street>
<!-- Reorder these if your country does things differently -->
<city>Herndon</city>
<region>VA</region>
<code>20171</code>
<country>US</country>
</postal>
<phone>+1 703 345 3513</phone>
<email>lee.howard@twcable.com</email>
</address>
</author>
<author fullname="Victor Kuarsingh" initials="V" surname="Kuarsingh">
<organization>Dyn Inc</organization>
<address>
<postal>
<street>150 Dow Street</street>
<city>Manchester, NH</city>
<country>US</country>
<code/>
</postal>
<email>victor@jvknet.com</email>
</address>
</author>
<author fullname="Yanick Pouffary" initials="Y" surname="Pouffary">
<organization>Hewlett Packard</organization>
<address>
<postal>
<street>950 Route Des Colles</street>
<city>Sophia-Antipolis</city>
<country>France</country>
<code>06901</code>
</postal>
<email>Yanick.Pouffary@hp.com</email>
</address>
</author>
<author fullname="Eric Vyncke" initials="E" surname="Vyncke">
<organization>Cisco Systems</organization>
<address>
<postal>
<street>De Kleetlaan 6a</street>
<city>Diegem</city>
<country>Belgium</country>
<code>1831</code>
</postal>
<phone>+32 2 778 4677</phone>
<email>evyncke@cisco.com</email>
</address>
</author>
<date day="31" month="July" year="2014"/>
<!-- Meta-data Declarations -->
<!-- WG name at the upperleft corner of the doc,
IETF is fine for individual submissions.
If this element is not present, the default is "Network Working Group",
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<keyword>IPv6 migration transition enterprise</keyword>
<!-- Keywords will be incorporated into HTML output
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keywords will be used for the search engine. -->
<abstract>
<t>Enterprise network administrators worldwide are in various stages of
preparing for or deploying IPv6 into their networks. The administrators
face different challenges than operators of Internet access providers,
and have reasons for different priorities. The overall problem for many
administrators will be to offer Internet-facing services over IPv6,
while continuing to support IPv4, and while introducing IPv6 access
within the enterprise IT network. The overall transition will take most
networks from an IPv4-only environment to a dual stack network
environment and eventually an IPv6-only operating mode. This document
helps provide a framework for enterprise network architects or
administrators who may be faced with many of these challenges as they
consider their IPv6 support strategies.</t>
</abstract>
</front>
<middle>
<section anchor="Introduction" title="Introduction">
<t>An Enterprise Network is defined in <xref target="RFC4057"/> as a
network that has multiple internal links, one or more router connections
to one or more Providers, and is actively managed by a network
operations entity (the "administrator", whether a single person or
department of administrators). Administrators generally support an
internal network, consisting of users' workstations, personal computers,
mobile devices, other computing devices and related peripherals, a server
network, consisting of accounting and business application servers, and an
external network, consisting of Internet-accessible services such as web
servers, email servers, VPN systems, and customer applications. This
document is intended as guidance for enterprise network architects and
administrators in planning their IPv6 deployments.</t>
<t>The business reasons for spending time, effort, and money on IPv6
will be unique to each enterprise. The most common drivers are due to
the fact that when Internet service providers, including mobile wireless
carriers, run out of IPv4 addresses, they will provide native IPv6 and
non-native IPv4. The non-native IPv4 service may be NAT64, NAT444,
Dual-stack Lite, MAP-T, MAP-E, or other transition technologies. Compared
to tunneled or translated service, native traffic typically performs
better and more reliably than non-native. For example, for client networks trying to reach enterprise networks, the IPv6 experience will be better
than the transitional IPv4 if the enterprise deploys IPv6 in its public-
facing services. The native IPv6 network path should also be simpler to
manage and, if necessary, troubleshoot. Further, enterprises doing
business in growing parts of the world may find IPv6 growing faster there, where again potential new customers, employees and partners are using
IPv6. It is thus in the enterprise's interests to deploy native IPv6, at
the very least in its public-facing services, but ultimately across the
majority or all of its scope.</t>
<t/>
<t>The text in this document provides specific guidance for enterprise
networks, and complements other related work in the IETF, including
<xref target="I-D.ietf-v6ops-design-choices"/> and <xref
target="RFC5375"/>.</t>
<section title="Enterprise Assumptions">
<t>For the purpose of this document, we assume:</t>
<t><list style="symbols">
<t>The administrator is considering deploying IPv6 (but see <xref
target="IPv4-only"/> below).</t>
<t>The administrator has existing IPv4 networks and devices which
will continue to operate and be supported.</t>
<t>The administrator will want to minimize the level of disruption
to the users and services by minimizing number of technologies and
functions that are needed to mediate any given application. In
other words: provide native IP wherever possible.</t>
</list></t>
<t>Based on these assumptions, an administrator will want to use
technologies which minimize the number of flows being tunnelled,
translated or intercepted at any given time. The administrator will
choose transition technologies or strategies which allow most traffic
to be native, and will manage non-native traffic. This will allow the
administrator to minimize the cost of IPv6 transition technologies, by
containing the number and scale of transition systems.</t>
<t>Tunnels used for IPv6/IPv4 transition are expected as near/mid-
term mechanisms, while IPv6 tunneling will be used for many long-term
operational purposes such as security, routing control, mobility,
multi-homing, traffic engineering, etc. We refer to the former class
of tunnels as "transition tunnels"</t>
</section>
<section anchor="IPv4-only" title="IPv4-only Considerations">
<t>As described in <xref target="RFC6302"/> administrators should take
certain steps even if they are not considering IPv6. Specifically,
Internet-facing servers should log the source port number, timestamp
(from a reliable source), and the transport protocol. This will allow
investigation of malefactors behind address-sharing technologies such
as NAT444, MAP, or Dual-stack Lite. Such logs should be protected for
integrity, safeguarded for privacy and periodically purged within
applicable regulations for log retention.</t>
<t>Other IPv6 considerations may impact ostensibly IPv4-only networks,
e.g. <xref target="RFC6104"/> describes the rogue IPv6 RA problem,
which may cause problems in IPv4-only networks where IPv6 is enabled
in end systems on that network. Further discussion of the security
implications of IPv6 in IPv4-only networks can be found in <xref
target="RFC7123"/>).</t>
</section>
<section title="Reasons for a Phased Approach">
<t>Given the challenges of transitioning user workstations, corporate
systems, and Internet-facing servers, a phased approach allows
incremental deployment of IPv6, based on the administrator's own
determination of priorities. This document outlines suggested
phases: a Preparation and Assessment Phase, an Internal Phase,
and an External Phase. The Preparation Phase is highly recommended to
all administrators, as it will save errors and complexity in later
phases. Each administrator must decide whether to begin with an
External Phase (enabling IPv6 for Internet-facing systems, as
recommended in <xref target="RFC5211"/>) or an Internal Phase
(enabling IPv6 for internal interconnections first).</t>
<t>Each scenario is likely to be different to some extent, but we can
highlight some considerations:</t>
<t><list style="symbols">
<t>In many cases, customers outside the network will have IPv6
before the internal enterprise network. For these customers, IPv6
may well perform better, especially for certain applications, than
translated or tunneled IPv4, so the administrator may want to
prioritize the External Phase such that those customers have the
simplest and most robust connectivity to the enterprise, or at
least its external-facing elements.</t>
<t>Employees who access internal systems by VPN may find that
their ISPs provide translated IPv4, which does not support the
required VPN protocols. In these cases, the administrator may want
to prioritize the External Phase, and any other
remotely-accessible internal systems. It is worth noting that a
number of emerging VPN solutions provide dual-stack connectivity;
thus a VPN service may be useful for employees in IPv4-only access
networks to access IPv6 resources in the enterprise network (much
like many public tunnel broker services, but specifically for the
enterprise). Some security considerations are described in <xref
target="I-D.ietf-opsec-vpn-leakages"/>. </t>
<t>Internet-facing servers cannot be managed over IPv6 unless the
management systems are IPv6-capable. These might be Network
Management Systems (NMS), monitoring systems, or just remote
management desktops. Thus in some cases, the Internet-facing
systems are dependent on IPv6-capable internal networks. However,
dual-stack Internet-facing systems can still be managed over
IPv4.</t>
<t>Virtual machines may enable a faster rollout once initial
system deployment is complete. Management of VMs over IPv6 is
still dependent on the management software supporting IPv6.</t>
<t>IPv6 is enabled by default on all modern operating systems, so
it may be more urgent to manage and have visibility on the
internal traffic. It is important to manage IPv6 for security
purposes, even in an ostensibly IPv4-only network, as described in
<xref target="RFC7123"/>.</t>
<t>In many cases, the corporate accounting, payroll, human
resource, and other internal systems may only need to be reachable
from the internal network, so they may be a lower priority. As
enterprises require their vendors to support IPv6, more internal
applications will support IPv6 by default and it can be expected
that eventually new applications will only support IPv6. The
inventory, as described in <xref target="inventory_phase"/>, will
help determine the systems' readiness, as well as the readiness of
the supporting network elements and security, which will be a
consideration in prioritization of these corporate systems.</t>
<t>Some large organizations (even when using private IPv4
addresses<xref target="RFC1918"/>) are facing IPv4 address
exhaustion because of the internal network growth (for example the
vast number of virtual machines) or because of the acquisition of
other companies that often raise private IPv4 address overlapping
issues.</t>
<t>IPv6 restores end to end transparency even for internal
applications (of course security policies must still be enforced).
When two organizations or networks merge <xref
target="RFC6879"/>, the unique addressing of
IPv6 can make the merger much easier and faster. A merger may,
therefore, prioritize IPv6 for the affected systems.</t>
</list> These considerations are in conflict; each administrator
must prioritize according to their company's conditions. It is worth
noting that the reasons given in one "Large Corporate User's View of
IPng", described in <xref target="RFC1687"/>, for reluctance to deploy
have largely been satisfied or overcome in the intervening years.</t>
</section>
</section>
<section title="Preparation and Assessment Phase" toc="default">
<t/>
<section title="Program Planning">
<t>Since enabling IPv6 is a change to the most fundamental Internet
Protocol, and since there are so many interdependencies, having a
professional project manager organize the work is highly recommended.
In addition, an executive sponsor should be involved in determining
the goals of enabling IPv6 (which will establish the order of the
phases), and should receive regular updates.</t>
<t>It may be necessary to complete the Preparation Phase before
determining whether to prioritized the Internal or External Phase, since
needs and readiness assessments are part of that phase. For a large
enterprise, it may take several iterations to really understand the
level of effort required. Depending on the required schedule, it may
be useful to roll IPv6 projects into other architectural upgrades--this
can be an excellent way to improve the network and reduce costs.
However, by increasing the scope of projects, the schedule is often
affected. For instance, a major systems upgrade may take a year to
complete, where just patching existing systems may take only a few
months. </t>
<t>The deployment of IPv6 will not generally stop all other technology
work. Once IPv6 has been identified as an important initiative, all
projects, both new and in-progress, will need to be reviewed to ensure
IPv6 support.</t>
<t>It is normal for assessments to continue in some areas while
execution of the project begins in other areas. This is fine, as long
as recommendations in other parts of this document are considered,
especially regarding security (for instance, one should not deploy
IPv6 on a system before security has been evaluated). </t>
</section>
<section anchor="inventory_phase" title="Inventory Phase">
<t>To comprehend the scope of the inventory phase we recommend
dividing the problem space in two: network infrastructure readiness
and applications readiness.</t>
<section title="Network infrastructure readiness assessment">
<t>The goal of this assessment is to identify the level of IPv6
readiness of network equipment. This will identify the effort required
to move to an infrastructure that supports IPv6 with the same
functional service capabilities as the existing IPv4 network. This may
also require a feature comparison and gap analysis between IPv4 and
IPv6 functionality on the network equipment and software. IPv6 support
will require testing; features often work differently in vendors' labs
than production networks. Some devices and software will require IPv4
support for IPv6 to work.</t>
<t>The inventory will show which network devices are already
capable, which devices can be made IPv6 ready with a
code/firmware upgrade, and which devices will need to be
replaced. The data collection consists of a network discovery to
gain an understanding of the topology and inventory network
infrastructure equipment and code versions with information
gathered from static files and IP address management, DNS and
DHCP tools.</t>
<t>Since IPv6 might already be present in the environment,
through default configurations or VPNs, an infrastructure
assessment (at minimum) is essential to evaluate potential
security risks.</t> </section>
<section title="Applications readiness assessment">
<t>Just like network equipment, application software needs to
support IPv6. This includes OS, firmware, middleware and
applications (including internally developed applications). Vendors
will typically handle IPv6 enablement of off-the-shelf products, but
often enterprises need to request this support from vendors. For
internally developed applications it is the responsibility of the
enterprise to enable them for IPv6. Analyzing how a given
application communicates over the network will dictate the steps
required to support IPv6. Applications should avoid instructions
specific to a given IP address family. Any applications that use
APIs, such as the C language, that expose the IP version
specifically, need to be modified to also work with IPv6.</t>
<t>There are two ways to IPv6-enable applications. The first
approach is to have separate logic for IPv4 and IPv6, thus leaving
the IPv4 code path mainly untouched. This approach causes the least
disruption to the existing IPv4 logic flow, but introduces more
complexity, since the application now has to deal with two logic
loops with complex race conditions and error recovery mechanisms
between these two logic loops. The second approach is to create a
combined IPv4/IPv6 logic, which ensures operation regardless of the
IP version used on the network. Knowing whether a given
implementation will use IPv4 or IPv6 in a given deployment is a
matter of some art; see Source Address Selection <xref
target="RFC6724"/> and Happy Eyeballs <xref target="RFC6555"/>. It
is generally recommended that the application developer use industry
IPv6-porting tools to locate the code that needs to be updated. Some
discussion of IPv6 application porting issues can be found in <xref
target="RFC4038"/>.</t>
</section>
<section title="Importance of readiness validation and testing">
<t>Lastly IPv6 introduces a completely new way of addressing
endpoints, which can have ramifications at the network layer all the
way up to the applications. So to minimize disruption during the
transition phase we recommend complete functionality, scalability
and security testing to understand how IPv6 impacts the services and
networking infrastructure.</t>
</section>
</section>
<section title="Training">
<t>Many organizations falter in IPv6 deployment because of a
perceived training gap. Training is important for those who work with
addresses regularly, as with anyone whose work is changing. Better
knowledge of the reasons IPv6 is being deployed will help inform the
assessment of who needs training, and what training they need.</t>
</section>
<section title="Security Policy">
<t>It is obvious that IPv6 networks should be deployed in a secure
way. The industry has learnt a lot about network security with IPv4,
so, network operators should leverage this knowledge and expertise
when deploying IPv6. IPv6 is not so different than IPv4: it is a
connectionless network protocol using the same lower layer service and
delivering the same service to the upper layer. Therefore, the
security issues and mitigation techniques are mostly identical with
same exceptions that are described further.</t>
<section title="IPv6 is no more secure than IPv4">
<t>Some people believe that IPv6 is inherently more secure than IPv4
because it is new. Nothing can be more wrong. Indeed, being a new
protocol means that bugs in the implementations have yet to be
discovered and fixed and that few people have the operational
security expertise needed to operate securely an IPv6 network. This
lack of operational expertise is the biggest threat when deploying
IPv6: the importance of training is to be stressed again.</t>
<t>One security myth is that thanks to its huge address space, a
network cannot be scanned by enumerating all IPv6 address in a /64
LAN hence a malevolent person cannot find a victim. <xref
target="RFC5157"/> describes some alternate techniques to find
potential targets on a network, for example enumerating all DNS
names in a zone. Additional advice in this area is also given in
<xref target="I-D.ietf-opsec-ipv6-host-scanning"/>.</t>
<t>Another security myth is that IPv6 is more secure because it
mandates the use of IPsec everywhere. While the original IPv6
specifications may have implied this, <xref target="RFC6434"/>
clearly states that IPsec support is not mandatory. Moreover, if all
the intra-enterprise traffic is encrypted, both malefactors and
security tools that rely on payload inspection (IPS, firewall, ACL,
IPFIX (<xref target="RFC7011"/> and <xref target="RFC7012"/>), etc)
will be thwarted. Therefore, IPsec is as useful in IPv6
as in IPv4 (for example to establish a VPN overlay over a
non-trusted network or reserved for some specific applications).</t>
<t>The last security myth is that amplification attacks (such as
<xref target="SMURF"/>) do not exist in IPv6 because there is no
more broadcast. Alas, this is not true as ICMP error (in some cases)
or information messages can be generated by routers and hosts when
forwarding or receiving a multicast message (see Section 2.4 of
<xref target="RFC4443"/>). Therefore, the generation and the
forwarding rate of ICMPv6 messages must be limited as in IPv4.</t>
<t>It should be noted that in a dual-stack network the security
implementation for both IPv4 and IPv6 needs to be considered, in
addition to security considerations related to the interaction of
(and transition between) the two, while they coexist.</t>
</section>
<section title="Similarities between IPv6 and IPv4 security">
<t>As mentioned earlier, IPv6 is quite similar to IPv4, therefore
several attacks apply for both protocol families, including:</t>
<t><list style="symbols">
<t>Application layer attacks: such as cross-site scripting or
SQL injection</t>
<t>Rogue device: such as a rogue Wi-Fi Access Point</t>
<t>Flooding and all traffic-based denial of services (including
the use of control plane policing for IPv6 traffic see <xref
target="RFC6192"/>)</t>
</list></t>
<t>A specific case of congruence is IPv6 Unique Local Addresses
(ULAs) <xref target="RFC4193"/> and IPv4 private addressing <xref
target="RFC1918"/>, which do not provide any security by 'magic'. In
both cases, the edge router must apply strict filters to block those
private addresses from entering and, just as importantly, leaving
the network. This filtering can be done by the enterprise or by the
ISP, but the cautious administrator will prefer to do it in the
enterprise.</t>
<t>IPv6 addresses can be spoofed as easily as IPv4 addresses and
there are packets with bogon IPv6 addresses (see <xref
target="CYMRU"/>). Anti-bogon filtering must be done in the data and
routing planes. It can be done by the enterprise or by the ISP, or
both, but again the cautious administrator will prefer to do it in
the enterprise.</t>
</section>
<section anchor="ipv6_security_specifics"
title="Specific Security Issues for IPv6">
<t>Even if IPv6 is similar to IPv4, there are some differences that
create some IPv6-only vulnerabilities or issues. We give examples of
such differences in this section.</t>
<t>Privacy extension addresses <xref target="RFC4941"/> are usually
used to protect individual privacy by periodically changing the
interface identifier part of the IPv6 address to avoid tracking a
host by its otherwise always identical and unique MAC-based EUI-64.
While this presents a real advantage on the Internet, moderated by
the fact that the prefix part remains the same, it complicates the
task of following an audit trail when a security officer or network
operator wants to trace back a log entry to a host in their network,
because when the tracing is done the searched IPv6 address could
have disappeared from the network. Therefore, the use of privacy
extension addresses usually requires additional monitoring and
logging of the binding of the IPv6 address to a data-link layer
address (see also the monitoring section of <xref
target="I-D.ietf-opsec-v6"/>). Some early enterprise deployments
have taken the approach of using tools that harvest IP/MAC address
mappings from switch and router devices to provide address
accountability; this approach has been shown to work, though it can
involve gathering significantly more address data than in equivalent
IPv4 networks. An alternative is to try to prevent the use of
privacy extension addresses by enforcing the use of DHCPv6, such
that hosts only get addresses assigned by a DHCPv6 server. This can
be done by configuring routers to set the M-bit in Router
Advertisements, combined with all advertised prefixes being included
without the A-bit set (to prevent the use of stateless
auto-configuration). This technique of course requires that all
hosts support stateful DHCPv6. It is important to note that not all
operating systems exhibit the same behavior when processing RAs with
the M-Bit set. The varying OS behavior is related to the lack of
prescriptive definition around the A, M and O-bits within the ND
protocol. <xref target="I-D.liu-bonica-dhcpv6-slaac-problem"/>
provides a much more detailed analysis on the interaction of the
M-Bit and DHCPv6.</t>
<t>Extension headers complicate the task of stateless packet filters
such as ACLs. If ACLs are used to enforce a security policy, then
the enterprise must verify whether its ACL (but also stateful
firewalls) are able to process extension headers (this means
understand them enough to parse them to find the upper layers
payloads) and to block unwanted extension headers (e.g., to
implement <xref target="RFC5095"/>). This topic is discussed further
in <xref target="RFC7045"/>.</t>
<t>Fragmentation is different in IPv6 because it is done only by
source host and never during a forwarding operation. This means that
ICMPv6 packet-too-big messages must be allowed to pass through the
network and not be filtered <xref target="RFC4890"/>. Fragments can
also be used to evade some security mechanisms such as RA-guard
<xref target="RFC6105"/>. See also <xref target="RFC5722"/>, and
<xref target="RFC7113"/>.</t>
<t>One of the biggest differences between IPv4 and IPv6 is the
introduction of the Neighbor Discovery Protocol <xref
target="RFC4861"/>, which includes a variety of important IPv6
protocol functions, including those provided in IPv4 by ARP <xref
target="RFC0826"/>. NDP runs over ICMPv6 (which as stated above
means that security policies must allow some ICMPv6 messages to
pass, as described in RFC 4890), but has the same lack of security
as, for example, ARP, in that there is no inherent message
authentication. While Secure Neighbour Discovery (SeND) <xref
target="RFC3971"/> and CGA <xref target="RFC3972"/> have been
defined, they are not widely implemented). The threat model for
Router Advertisements within the NDP suite is similar to that of
DHCPv4 (and DHCPv6), in that a rogue host could be either a rogue
router or a rogue DHCP server. An IPv4 network can be made more
secure with the help of DHCPv4 snooping in edge switches, and
likewise RA snooping can improve IPv6 network security (in IPv4-only
networks as well). Thus enterprises using such techniques for IPv4
should use the equivalent techniques for IPv6, including RA-guard
<xref target="RFC6105"/> and all work in progress from the SAVI WG,
e.g. <xref target="RFC6959"/>, which is similar to the
protection given by dynamic ARP monitoring in IPv4. Other DoS
vulnerabilities are related to NDP cache exhaustion, and mitigation
techniques can be found in (<xref target="RFC6583"/>).</t>
<t>As stated previously, running a dual-stack network doubles the
attack exposure as a malevolent person has now two attack vectors:
IPv4 and IPv6. This simply means that all routers and hosts
operating in a dual-stack environment with both protocol families
enabled (even if by default) must have a congruent security policy
for both protocol versions. For example, permit TCP ports 80 and 443
to all web servers and deny all other ports to the same servers must
be implemented both for IPv4 and IPv6. It is thus important that the
tools available to administrators readily support such
behaviour.</t>
</section>
</section>
<section title="Routing">
<t>An important design choice to be made is what IGP to use inside the
network. A variety of IGPs (IS-IS, OSPFv3 and RIPng) support IPv6
today and picking one over the other is a design choice that will be
dictated mostly by existing operational policies in an enterprise
network. As mentioned earlier, it would be beneficial to maintain
operational parity between IPv4 and IPv6 and therefore it might make
sense to continue using the same protocol family that is being used
for IPv4. For example, in a network using OSPFv2 for IPv4, it might
make sense to use OSPFv3 for IPv6. It is important to note that
although OSPFv3 is similar to OSPFv2, they are not the same. On the
other hand, some organizations may chose to run different routing
protocols for different IP versions. For example, one may chose to run
OSPFv2 for IPv4 and IS-IS for IPv6. An important design question to
consider here is whether to support one IGP or two different IGPs in
the longer term. <xref target="I-D.ietf-v6ops-design-choices"/>
presents advice on the design choices that arise when considering IGPs
and discusses the advantages and disadvantages to different approaches
in detail.</t>
</section>
<section title="Address Plan">
<t>The most common problem encountered in IPv6 networking is in
applying the same principles of conservation that are so important in
IPv4. IPv6 addresses do not need to be assigned conservatively. In
fact, a single larger allocation is considered more conservative than
multiple non-contiguous small blocks, because a single block occupies
only a single entry in a routing table. The advice in <xref
target="RFC5375"/> is still sound, and is recommended to the reader.
If considering ULAs, give careful thought to how well it is supported,
especially in multiple address and multicast scenarios, and assess the
strength of the requirement for ULA. <xref
target="I-D.ietf-v6ops-ula-usage-recommendations"/> provides much more
detailed analysis and recommendations on the usage of ULAs.</t>
<t>The enterprise administrator will want to evaluate whether the
enterprise will request address space from a LIR (Local Internet
Registry, such as an ISP), a RIR (Regional Internet Registry, such as
AfriNIC, APNIC, ARIN, LACNIC, or RIPE-NCC) or a NIR (National Internet
Registry, operated in some countries). The normal allocation is
Provider Aggregatable (PA) address space from the enterprise's ISP,
but use of PA space implies renumbering when changing provider.
Instead, an enterprise may request Provider Independent (PI) space;
this may involve an additional fee, but the enterprise may then be
better able to be multihomed using that prefix, and will avoid a
renumbering process when changing ISPs (though it should be noted that
renumbering caused by outgrowing the space, merger, or other internal
reason would still not be avoided with PI space).</t>
<t>The type of address selected (PI vs. PA) should be congruent with
the routing needs of the enterprise. The selection of address type
will determine if an operator will need to apply new routing
techniques and may limit future flexibility. There is no right answer,
but the needs of the external phase may affect what address type is
selected.</t>
<t>Each network location or site will need a prefix assignment.
Depending on the type of site/location, various prefix sizes may be
used. In general, historical guidance suggests that each site should
get at least a /48, as documented in RFC 5375 and <xref
target="RFC6177"/>. In addition to allowing for simple planning, this
can allow a site to use its prefix for local connectivity, should the
need arise, and if the local ISP supports it.</t>
<t>When assigning addresses to end systems, the enterprise may use
manually-configured addresses (common on servers) or SLAAC or DHCPv6
for client systems. Early IPv6 enterprise deployments have used SLAAC,
both for its simplicity but also due to the time DHCPv6 has taken to
mature. However, DHCPv6 is now very mature, and thus workstations
managed by an enterprise may use stateful DHCPv6 for addressing on
corporate LAN segments. DHCPv6 allows for the additional configuration
options often employed by enterprise administrators, and by using
stateful DHCPv6, administrators correlating system logs know which
system had which address at any given time. Such an accountability
model is familiar from IPv4 management, though for DHCPv6 hosts are
identified by DUID rather than MAC address. For equivalent
accountability with SLAAC (and potentially privacy addresses), a
monitoring system that harvests IP/MAC mappings from switch and router
equipment could be used.</t>
<t>A common deployment consideration for any enterprise network is how
to get host DNS records updated. Commonly, either the host will send
DNS updates or the DHCP server will update records. If there is
sufficient trust between the hosts and the DNS server, the hosts may
update (and the enterprise may use SLAAC for addressing). Otherwise,
the DHCPv6 server can be configured to update the DNS server.
Note that an enterprise network with this more controlled environment
will need to disable SLAAC on network segments and force end hosts to
use DHCPv6 only.</t>
<t>In the data center or server room, assume a /64 per VLAN. This
applies even if each individual system is on a separate VLAN. In a /48
assignment, typical for a site, there are then still 65,535 /64
blocks. Some administrators reserve a /64 but configure a small subnet,
such as /112, /126, or /127, to prevent rogue devices from attaching
and getting numbers; an alternative is to monitor traffic for
surprising addresses or ND tables for new entries. Addresses are either
configured manually on the server, or reserved on a DHCPv6 server,
which may also synchronize forward and reverse DNS (though see <xref
target="RFC6866"/> for considerations on static addressing). SLAAC is
not recommended for servers, because of the need to synchronize RA
timers with DNS TTLs so that the DNS entry expires at the same time as
the address. </t>
<t>All user access networks should be a /64. Point-to-point links
where Neighbor Discovery Protocol is not used may also utilize a /127
(see <xref target="RFC6164"/>).</t>
<t>Plan to aggregate at every layer of network hierarchy. There is no
need for VLSM <xref target="RFC1817"/> in IPv6, and addressing plans
based on conservation of addresses are short-sighted. Use of prefixes
longer then /64 on network segments will break common IPv6 functions
such as SLAAC<xref target="RFC4862"/>. Where multiple VLANs or other
layer two domains converge, allow some room for expansion. Renumbering
due to outgrowing the network plan is a nuisance, so allow room within
it. Generally, plan to grow to about twice the current size that can
be accommodated; where rapid growth is planned, allow for twice that
growth. Also, if DNS (or reverse DNS) authority may be delegated to
others in the enterprise, assignments need to be on nibble boundaries
(that is, on a multiple of 4 bits, such as /64, /60, /56, ..., /48,
/44), to ensure that delegated zones align with assigned prefixes.</t>
<t>If using ULAs, it is important to note that AAAA and PTR records
for ULA are not recommended to be installed in the global DNS.
Similarly, reverse (address-to-name) queries for ULA must not be sent
to name servers outside of the organization, due to the load that such
queries would create for the authoritative name servers for the
ip6.arpa zone. For more details please refer to section 4.4 of <xref
target="RFC4193"/>.</t>
<t>Enterprise networks more and more include virtual networks where a
single physical node may host many virtualized addressable devices. It
is imperative that the addressing plans assigned to these virtual
networks and devices be consistent and non-overlapping with the
addresses assigned to real networks and nodes. For example, a virtual
network established within an isolated lab environment may at a later
time become attached to the production enterprise network.</t>
</section>
<section title="Tools Assessment">
<t>Enterprises will often have a number of operational tools and
support systems which are used to provision, monitor, manage and
diagnose the network and systems within their environment. These tools
and systems will need to be assessed for compatibility with IPv6. The
compatibility may be related to the addressing and connectivity of
various devices as well as IPv6 awareness of the tools and processing
logic.</t>
<t>The tools within the organization fall into two general categories,
those which focus on managing the network, and those which are focused
on managing systems and applications on the network. In either
instance, the tools will run on platforms which may or may not be
capable of operating in an IPv6 network. This lack in functionality
may be related to Operating System version, or based on some hardware
constraint. Those systems which are found to be incapable of utilizing
an IPv6 connection, or which are dependent on an IPv4 stack, may need
to be replaced or upgraded.</t>
<t>In addition to devices working on an IPv6 network natively, or via
a transition tunnel, many tools and support systems may require
additional software updates to be IPv6 aware, or even a hardware
upgrade (usually for additional memory: IPv6 addresses are larger and
for a while, IPv4 and IPv6 addresses will coexist in the tool). This
awareness may include the ability to manage IPv6 elements and/or
applications in addition to the ability to store and utilize IPv6
addresses.</t>
<t>Considerations when assessing the tools and support systems may
include the fact that IPv6 addresses are significantly larger than
IPv4, requiring data stores to support the increased size. Such issues
are among those discussed in <xref target="RFC5952"/>. Many
organizations may also run dual-stack networks, therefore the tools
need to not only support IPv6 operation, but may also need to support
the monitoring, management and intersection with both IPv6 and IPv4
simultaneously. It is important to note that managing IPv6 is not just
constrained to using large IPv6 addresses, but also that IPv6
interfaces and nodes are likely to use two or more addresses as part
of normal operation. Updating management systems to deal with these
additional nuances will likely consume time and considerable
effort.</t>
<t>For networking systems, like node management systems, it is not
always necessary to support local IPv6 addressing and connectivity.
Operations such as SNMP MIB polling can occur over IPv4 transport
while seeking responses related to IPv6 information. Where this may
seem advantageous to some, it should be noted that without local IPv6
connectivity, the management system may not be able to perform all
expected functions - such as reachability and service checks.</t>
<t>Organizations should be aware that changes to older IPv4-only SNMP
MIB specifications have been made by the IETF related to legacy
operation in <xref target="RFC2096"/> and <xref target="RFC2011"/>.
Updated specifications are now available in <xref target="RFC4292"/>
and <xref target="RFC4293"/> which modified the older MIB framework to
be IP protocol agnostic, supporting both IPv4 and IPv6. Polling
systems will need to be upgraded to support these updates as well as
the end stations which are polled.</t>
</section>
</section>
<section title="External Phase">
<t>The external phase for enterprise IPv6 adoption covers topics which
deal with how an organization connects its infrastructure to the
external world. These external connections may be toward the Internet at
large, or to other networks. The external phase covers connectivity,
security and monitoring of various elements and outward facing or
accessible services.</t>
<section title="Connectivity">
<t>The enterprise will need to work with one or more Service Providers
to gain connectivity to the Internet or transport service
infrastructure such as a BGP/MPLS IP VPN as described in <xref
target="RFC4364"/> and <xref target="RFC4659"/>. One significant
factor that will guide how an organization may need to communicate
with the outside world will involve the use of PI (Provider
Independent) and/or PA (Provider Aggregatable) IPv6 space.</t>
<t>Enterprises should be aware that depending on which address type
they selected (PI vs. PA) in their planning phase, they may need to
implement new routing functions and/or behaviours to support their
connectivity to the ISP. In the case of PI, the upstream ISP may offer
options to route the prefix (typically a /48) on the enterprise's
behalf and update the relevant routing databases. Otherwise, the
enterprise may need to perform this task on their own and use BGP to
inject the prefix into the global BGP system.</t>
<t>Note that the rules set by the RIRs for an enterprise acquiring PI
address space have changed over time. For example, in the European
region the RIPE-NCC no longer requires an enterprise to be multihomed
to be eligible for an IPv6 PI allocation. Requests can be made
directly or via a LIR. It is possible that the rules may change again,
and may vary between RIRs.</t>
<t>When seeking IPv6 connectivity to a Service Provider, Native IPv6
connectivity is preferred since it provides the most robust and
efficient form of connectivity. If native IPv6 connectivity is not
possible due to technical or business limitations, the enterprise may
utilize readily available transition tunnel IPv6 connectivity. There
are IPv6 transit providers which provide robust tunnelled IPv6
connectivity which can operate over IPv4 networks. It is important to
understand the transition tunnel mechanism used, and to consider that
it will have higher latency than native IPv4 or IPv6, and may have
other problems, e.g. related to MTUs.</t>
<t>It is important to evaluate MTU considerations when adding IPv6
to an existing IPv4 network. It is generally desirable to have the
IPv6 and IPv4 MTU congruent to simplify operations (so the two address
families behave similarly, that is, as expected). If the enterprise
uses transition tunnels inside or externally for IPv6 connectivity,
then modification of the MTU on hosts/routers may be needed as
mid-stream fragmentation is no longer supported in IPv6. It is
preferred that pMTUD is used to optimize the MTU, so erroneous
filtering of the related ICMPv6 message types should be monitored.
Adjusting the MTU may be the only option if undesirable upstream
ICMPv6 filtering cannot be removed.</t>
</section>
<section title="Security">
<t>The most important part of security for external IPv6 deployment is
filtering and monitoring. Filtering can be done by stateless ACLs or a
stateful firewall. The security policies must be consistent for IPv4
and IPv6 (else the attacker will use the less protected protocol
stack), except that certain ICMPv6 messages must be allowed through
and to the filtering device (see <xref target="RFC4890"/>):</t>
<t><list style="symbols">
<t>Packet Too Big: essential to allow Path MTU discovery to work</t>
<t>Parameter Problem</t>
<t>Time Exceeded</t>
</list></t>
<t>In addition, Neighbor Discovery Protocol messages (including
Neighbor Solicitation, Router Advertisements, etc.) are required for
local hosts.</t>
<t>It could also be safer to block all fragments where the transport
layer header is not in the first fragment to avoid attacks as
described in <xref target="RFC5722"/>. Some filtering devices allow
this filtering. Ingress filters and firewalls should follow <xref
target="RFC5095"/> in handling routing extension header type 0,
dropping the packet and sending ICMPv6 Parameter Problem, unless
Segments Left = 0 (in which case, ignore the header).</t>
<t>If an Intrusion Prevention System (IPS) is used for IPv4 traffic,
then an IPS should also be used for IPv6 traffic. In general, make
sure IPv6 security is at least as good as IPv4. This also includes all
email content protection (anti-spam, content filtering, data leakage
prevention, etc.).</t>
<t>The edge router must also implement anti-spoofing techniques based
on <xref target="RFC2827"/> (also known as BCP 38).</t>
<t>In order to protect the networking devices, it is advised to
implement control plane policing as per <xref target="RFC6192"/>.</t>
<t>The potential NDP cache exhaustion attack (see <xref
target="RFC6583"/>) can be mitigated by two techniques:</t>
<t><list style="symbols">
<t>Good NDP implementation with memory utilization limits as well
as rate-limiters and prioritization of requests.</t>
<t>Or, as the external deployment usually involves just a couple
of exposed statically configured IPv6 addresses (virtual addresses
of web, email, and DNS servers), then it is straightforward to
build an ingress ACL allowing traffic for those addresses and
denying traffic to any other addresses. This actually prevents the
attack as a packet for a random destination will be dropped and
will never trigger a neighbor resolution.</t>
</list></t>
</section>
<section title="Monitoring">
<t>Monitoring the use of the Internet connectivity should be done for
IPv6 as it is done for IPv4. This includes the use of IP Flow
Information eXport (IPFIX) <xref target="RFC7012"/> to report abnormal
traffic patterns (such as port scanning, SYN-flooding, related IP
source addresses) from monitoring tools and evaluating data read from
SNMP MIBs <xref target="RFC4293"/> (some of which also enable the
detection of abnormal bandwidth utilization) and syslogs (finding
server and system errors). Where Netflow is used, version 9 is required
for IPv6 support. Monitoring systems should be able to examine IPv6
traffic, use IPv6 for connectivity, record IPv6 address, and any log
parsing tools and reporting need to support IPv6. Some of this data
can be sensitive (including personally identifiable information) and
care in securing it should be taken, with periodic purges. Integrity
protection on logs and sources of log data is also important to
detect unusual behavior (misconfigurations or attacks). Logs may be
used in investigations, which depend on trustworthy data sources
(tamper resistant).
</t>
<t>In addition, monitoring of external services (such as web sites)
should be made address-specific, so that people are notified when
either the IPv4 or IPv6 version of a site fails.</t>
</section>
<section title="Servers and Applications">
<t>The path to the servers accessed from the Internet usually involves
security devices (firewall, IPS), server load balancing (SLB) and real
physical servers. The latter stage is also multi-tiered for
scalability and security between presentation and data storage. The
ideal transition is to enable native dual-stack on all devices; but
as part of the phased approach, operators have used the following
techniques with success:</t>
<t><list style="symbols">
<t>Use a network device to apply NAT64 and basically translate an
inbound TCP connection (or any other transport protocol) over IPv6
into a TCP connection over IPv4. This is the easiest to deploy as
the path is mostly unchanged but it hides all IPv6 remote users
behind a single IPv4 address which leads to several audit trail
and security issues (see <xref target="RFC6302"/>).</t>
<t>Use the server load balancer which acts as an application proxy
to do this translation. Compared to the NAT64, it has the
potential benefit of going through the security devices as native
IPv6 (so more audit and trace abilities) and is also able to
insert a HTTP X-Forward-For header which contains the remote IPv6
address. The latter feature allows for logging, and rate-limiting
on the real servers based on the IPV6 address even if those
servers run only IPv4.</t>
</list></t>
<t>In either of these cases, care should be taken to secure logs for
privacy reasons, and to periodically purge them.</t>
</section>
<section title="Network Prefix Translation for IPv6">
<t>Network Prefix Translation for IPv6, or NPTv6 as described in <xref
target="RFC6296"/> provides a framework to utilize prefix ranges
within the internal network which are separate (address-independent)
from the assigned prefix from the upstream provider or registry. As
mentioned above, while NPTv6 has potential use-cases in IPv6 networks,
the implications of its deployment need to be fully understood,
particularly where any applications might embed IPv6 addresses in
their payloads.</t>
<t>Use of NPTv6 can be chosen independently from how addresses are
assigned and routed within the internal network, how prefixes are
routed towards the Internet, or whether PA or PI addresses are
used.</t>
</section>
</section>
<section title="Internal Phase">
<t>This phase deals with the delivery of IPv6 to the internal
user-facing side of the IT infrastructure, which comprises various
components such as network devices (routers, switches, etc.), end user
devices and peripherals (workstations, printers, etc.), and internal
corporate systems.</t>
<t>An important design paradigm to consider during this phase is
"dual-stack when you can, tunnel when you must". Dual-stacking allows a
more robust, production-quality IPv6 network than is typically
facilitated by internal use of transition tunnels that are harder to
troubleshoot and support, and that may introduce scalability and
performance issues. Tunnels may of course still be used in production
networks, but their use needs to be carefully considered, e.g. where the
transition tunnel may be run through a security or filtering device.
Tunnels do also provide a means to experiment with IPv6 and gain some
operational experience with the protocol. <xref target="RFC4213"/>
describes various transition mechanisms in more detail. <xref
target="RFC6964"/> suggests operational guidance when
using ISATAP tunnels <xref target="RFC5214"/>, though we would recommend
use of dual-stack wherever possible.</t>
<section title="Security">
<t>IPv6 must be deployed in a secure way. This means that all existing
IPv4 security policies must be extended to support IPv6; IPv6 security
policies will be the IPv6 equivalent of the existing IPv4 ones (taking
into account the difference for <xref target="RFC4890">ICMPv6</xref>).
As in IPv4, security policies for IPv6 will be enforced by firewalls,
ACL, IPS, VPN, and so on.</t>
<t><xref target="RFC4941">Privacy extension addresses</xref> raise a
challenge for an audit trail as explained in section <xref
target="ipv6_security_specifics"/>. The enterprise may choose to
attempt to enforce use of DHCPv6, or deploy monitoring tools that
harvest accountability data from switches and routers (thus making the
assumption that devices may use any addresses inside the network).</t>
<t>One major issue is threats against Neighbor Discovery. This means,
for example, that the internal network at the access layer (where hosts
connect to the network over wired or wireless) should implement <xref
target="RFC6105">RA-guard</xref> and the techniques being specified by
<xref target="RFC6959">SAVI WG</xref>; see also <xref
target="ipv6_security_specifics"/> for more information.</t>
</section>
<section title="Network Infrastructure">
<t>The typical enterprise network infrastructure comprises a
combination of the following network elements - wired access switches,
wireless access points, and routers (although it is fairly common to
find hardware that collapses switching and routing functionality into
a single device). Basic wired access switches and access points
operate only at the physical and link layers, and don't really have
any special IPv6 considerations other than being able to support IPv6
addresses themselves for management purposes. In many instances, these
devices possess a lot more intelligence than simply switching packets.
For example, some of these devices help assist with link layer
security by incorporating features such as ARP inspection and DHCP
Snooping, or they may help limit where multicast floods by using IGMP
(or, in the case of IPv6, MLD) snooping.</t>
<t>Another important consideration in enterprise networks is first hop
router redundancy. This directly ties into network reachability from
an end host's point of view. IPv6 Neighbor Discovery (ND), <xref
target="RFC4861"/>, provides a node with the capability to maintain a
list of available routers on the link, in order to be able to switch
to a backup path should the primary be unreachable. By default, ND
will detect a router failure in 38 seconds and cycle onto the next
default router listed in its cache. While this feature provides a
basic level of first hop router redundancy, most enterprise IPv4
networks are designed to fail over much faster. Although this delay
can be improved by adjusting the default timers, care must be taken to
protect against transient failures and to account for increased
traffic on the link. Another option to provide robust first hop
redundancy is to use the Virtual Router Redundancy Protocol for IPv6
(VRRPv3), <xref target="RFC5798"/>. This protocol provides a much
faster switchover to an alternate default router than default ND
parameters. Using VRRPv3, a backup router can take over for a failed
default router in around three seconds (using VRRPv3 default
parameters). This is done without any interaction with the hosts and a
minimum amount of VRRP traffic.</t>
<t>Last but not the least, one of the most important design choices to
make while deploying IPv6 on the internal network is whether to use
Stateless Automatic Address Configuration (SLAAC), <xref
target="RFC4862"/>, or Dynamic Host Configuration Protocol for IPv6
(DHCPv6), <xref target="RFC3315"/>, or a combination thereof. Each
option has advantages and disadvantages, and the choice will
ultimately depend on the operational policies that guide each
enterprise's network design. For example, if an enterprise is looking
for ease of use, rapid deployment, and less administrative overhead,
then SLAAC makes more sense for workstations. Manual or DHCPv6
assignments are still needed for servers, as described in the External
Phase and Address Plan sections of this document. However, if the
operational policies call for precise control over IP address
assignment for auditing then DHCPv6 may be preferred. DHCPv6 also
allows you to tie into DNS systems for host entry updates and gives
you the ability to send other options and information to clients. It
is worth noting that in general operation RAs are still needed in
DHCPv6 networks, as there is no DHCPv6 Default Gateway option.
Similarly, DHCPv6 is needed in RA networks for other configuration
information, e.g. NTP servers or, in the absence of support for DNS
resolvers in RAs <xref target="RFC6106"/>, DNS resolver
information.</t>
</section>
<section title="End user devices">
<t>Most operating systems (OSes) that are loaded on workstations and
laptops in a typical enterprise support IPv6 today. However, there are
various out-of-the-box nuances that one should be mindful about. For
example, the default behavior of OSes vary; some may have IPv6 turned
off by default, some may only have certain features such as privacy
extensions to IPv6 addresses (RFC 4941) turned off while others have
IPv6 fully enabled. Further, even when IPv6 is enabled, the choice of
which address is used may be subject to Source Address Selection (RFC
6724) and Happy Eyeballs (RFC 6555). Therefore, it is advised that
enterprises investigate the default behavior of their installed OS
base and account for it during the Inventory phases of their IPv6
preparations. Furthermore, some OSes may have some transition
tunneling mechanisms turned on by default and in such cases it is
recommended to administratively shut down such interfaces unless
required.</t>
<t>It is important to note that it is recommended that IPv6 be
deployed at the network and system infrastructure level before it is
rolled out to end user devices; ensure IPv6 is running and routed on
the wire, and secure and correctly monitored, before exposing IPv6 to
end users.</t>
<t>Smartphones and tablets are significant IPv6-capable platforms,
depending on the support of the carrier's data network.</t>
<t>IPv6 support for peripherals varies. Much like servers, printers are
generally configured with a static address (or DHCP reservation) so
clients can discover them reliably. </t>
</section>
<section title="Corporate Systems">
<t>No IPv6 deployment will be successful without ensuring that all the
corporate systems that an enterprise uses as part of its IT
infrastructure support IPv6. Examples of such systems include, but are
not limited to, email, video conferencing, telephony (VoIP), DNS,
RADIUS, etc. All these systems must have their own detailed IPv6
rollout plan in conjunction with the network IPv6 rollout. It is
important to note that DNS is one of the main anchors in an enterprise
deployment, since most end hosts decide whether or not to use IPv6
depending on the presence of IPv6 AAAA records in a reply to a DNS
query. It is recommended that system administrators selectively turn
on AAAA records for various systems as and when they are IPv6 enabled;
care must be taken though to ensure all services running on that host
name are IPv6-enabled before adding the AAAA record. Care with web
proxies is advised; a mismatch in the level of IPv6 support between
the client, proxy, and server can cause communication problems. All
monitoring and reporting tools across the enterprise will need to be
modified to support IPv6.</t>
</section>
</section>
<section title="IPv6-only">
<t>Early IPv6 enterprise deployments have generally taken a dual-stack
approach to enabling IPv6, i.e. the existing IPv4 services have not been
turned off. Although IPv4 and IPv6 networks will coexist for a long
time, the long term enterprise network roadmap should include steps to
simplify engineering and operations by deprecating IPv4 from the
dual-stack network. In some extreme cases, deploying dual-stack networks
may not even be a viable option for very large enterprises due to the
RFC 1918 address space not being large enough to support the network's
growth. In such cases, deploying IPv6-only networks might be the only
choice available to sustain network growth. In other cases, there may be
elements of an otherwise dual-stack network that may be run IPv6-only.</t>
<t>If nodes in the network don't need to talk to an IPv4-only node, then
deploying IPv6-only networks should be straightforward. However, most
nodes will need to communicate with some IPv4-only nodes; an IPv6-only
node may therefore require a translation mechanism. As <xref
target="RFC6144"/> points out, it is important to look at address
translation as a transition strategy towards running an IPv6-only
network.</t>
<t>There are various stateless and stateful IPv4/IPv6 translation
methods available today that help IPv6 to IPv4 communication. RFC 6144
provides a framework for IPv4/IPv6 translation and describes in detail
various scenarios in which such translation mechanisms could be used.
<xref target="RFC6145"/> describes stateless address translation. In
this mode, a specific IPv6 address range will represent IPv4 systems
(IPv4-converted addresses), and the IPv6 systems have addresses
(IPv4-translatable addresses) that can be algorithmically mapped to a
subset of the service provider's IPv4 addresses. <xref
target="RFC6146"/>, NAT64, describes stateful address translation. As
the name suggests, the translation state is maintained between IPv4
address/port pairs and IPv6 address/port pairs, enabling IPv6 systems to
open sessions with IPv4 systems. <xref target="RFC6147"/>, DNS64,
describes a mechanism for synthesizing AAAA resource records (RRs) from
A RRs. Together, RFCs 6146 and RFC 6147 provide a viable method for an
IPv6-only client to initiate communications to an IPv4-only server. As
described in the assumptions section, the administrator will usually
want most traffic or flows to be native, and only translate as needed.</t>
<t>The address translation mechanisms for the stateless and stateful
translations are defined in <xref target="RFC6052"/>. It is important to
note that both of these mechanisms have limitations as to which
protocols they support. For example, RFC 6146 only defines how stateful
NAT64 translates unicast packets carrying TCP, UDP, and ICMP traffic
only. The classic problems of IPv4 NAT also apply, e.g. handling IP
literals in application payloads. The ultimate choice of which
translation mechanism to chose will be dictated mostly by existing
operational policies pertaining to application support, logging
requirements, etc.</t>
<t>There is additional work being done in the area of address
translation to enhance and/or optimize current mechanisms. For example,
<xref target="I-D.xli-behave-divi"/> describes limitations with the
current stateless translation, such as IPv4 address sharing and
application layer gateway (ALG) problems, and presents the concept and
implementation of dual-stateless IPv4/IPv6 translation (dIVI) to address
those issues.</t>
<t>It is worth noting that for IPv6-only access networks that use
technologies such as NAT64, the more content providers (and enterprises)
that make their content available over IPv6, the less the requirement to
apply NAT64 to traffic leaving the access network. This particular point
is important for enterprises which may start their IPv6 deployment well
into the global IPv6 transition. As time progresses, and given the
current growth in availability of IPv6 content, IPv6-only operation
using NAT64 to manage some flows will become less expensive to run
versus the traditional NAT44 deployments since only IPv6 to IPv4 flows
need translation. <xref target="RFC6883"/> provides guidance and
suggestions for Internet Content Providers and Application Service
Providers in this context.</t>
<t>Enterprises should also be aware that networks may be subject to
future convergence with other networks (i.e. mergers, acquisitions,
etc). An enterprise considering IPv6-only operation may need to be aware
that additional transition technologies and/or connectivity strategies
may be required depending on the level of IPv6 readiness and deployment
in the merging networking.</t>
</section>
<section title="Considerations For Specific Enterprises">
<t/>
<section title="Content Delivery Networks">
<t>Some guidance for Internet Content and Application Service Providers
can be found in <xref target="RFC6883"/>, which includes a dedicated
section on Content Delivery Networks (CDNs). An enterprise that relies
on a CDN to deliver a 'better' e-commerce experience needs to ensure
that their CDN provider also supports IPv4/IPv6 traffic selection so
that they can ensure 'best' access to the content. A CDN could
enable external IPv6 content delivery even if the enterprise provides
that content over IPv4. </t>
</section>
<section title="Data Center Virtualization">
<t>IPv6 Data Center considerations are described in <xref
target="I-D.ietf-v6ops-dc-ipv6"/>.</t>
</section>
<section title="University Campus Networks">
<t>A number of campus networks around the world have made some initial
IPv6 deployment. This has been encouraged by their National Research
and Education Network (NREN) backbones having made IPv6 available
natively since the early 2000's. Universities are a natural place for
IPv6 deployment to be considered at an early stage, perhaps compared
to other enterprises, as they are involved by their very nature in
research and education.</t>
<t>Campus networks can deploy IPv6 at their own pace; there is no need
to deploy IPv6 across the entire enterprise from day one, rather
specific projects can be identified for an initial deployment, that
are both deep enough to give the university experience, but small
enough to be a realistic first step. There are generally three areas
in which such deployments are currently made.</t>
<t>In particular those initial areas commonly approached are:</t>
<t><list style="symbols">
<t>External-facing services. Typically the campus web presence and
commonly also external-facing DNS and MX services. This ensures
early IPv6-only adopters elsewhere can access the campus services
as simply and as robustly as possible.</t>
<t>Computer science department. This is where IPv6-related
research and/or teaching is most likely to occur, and where many
of the next generation of network engineers are studying, so
enabling some or all of the campus computer science department
network is a sensible first step.</t>
<t>The eduroam wireless network. Eduroam <xref
target="I-D.wierenga-ietf-eduroam"/> is the de facto wireless
roaming system for academic networks, and uses 802.1X-based
authentication, which is agnostic to the IP version used (unlike
web-redirection gateway systems). Making a campus' eduroam network
dual-stack is a very viable early step.</t>
</list></t>
<t>The general IPv6 deployment model in a campus enterprise will still
follow the general principles described in this document. While the
above early stage projects are commonly followed, these still require
the campus to acquire IPv6 connectivity and address space from their
NREN (or other provider in some parts of the world), and to enable
IPv6 on the wire on at least part of the core of the campus network.
This implies a requirement to have an initial address plan, and to
ensure appropriate monitoring and security measures are in place, as
described elsewhere in this document.</t>
<t>Campuses which have deployed to date do not use ULAs, nor do they
use NPTv6. In general, campuses have very stable PA-based address
allocations from their NRENs (or their equivalent). However, campus
enterprises may consider applying for IPv6 PI; some have already done
so. The discussions earlier in this text about PA vs. PI still
apply.</t>
<t>Finally, campuses may be more likely than many other enterprises to
run multicast applications, such as IP TV or live lecture or seminar
streaming, so may wish to consider support for specific IPv6 multicast
functionality, e.g. Embedded-RP <xref target="RFC3956"/> in routers
and MLDv1 and MLDv2 snooping in switches.</t>
</section>
</section>
<section title="Security Considerations">
<t>This document has multiple security sections detailing how to
securely deploy an IPv6 network within an enterprise network.</t>
</section>
<section title="Acknowledgements">
<t>The authors would like to thank Robert Sparks, Steve Hanna, Tom
Taylor, Brian Haberman, Stephen Farrell, Chris Grundemann, Ray Hunter,
Kathleen Moriarty, Benoit Claise, Brian Carpenter, Tina Tsou, Christian
Jaquenet, and Fred Templin for their substantial comments and
contributions.</t>
</section>
<section title="IANA Considerations">
<t>There are no IANA considerations or implications that arise from this
document.</t>
</section>
</middle>
<!-- *****BACK MATTER ***** -->
<back>
<references title="Informative References">
&rfc0826;
&rfc1687;
&rfc1817;
&rfc1918;
&rfc2011;
&rfc2096;
&rfc2827;
&rfc3315;
&rfc3956;
&rfc3971;
&rfc3972;
&rfc4038;
&rfc4057;
&rfc4193;
&rfc4213;
&rfc4293;
&rfc4292;
&rfc4364;
&rfc4443;
&rfc4659;
&rfc4861;
&rfc4862;
&rfc4890;
&rfc4941;
&rfc5095;
&rfc7012;
&rfc5157;
&rfc5211;
&rfc5214;
&rfc5375;
&rfc5722;
&rfc5798;
&rfc5952;
&rfc6052;
&rfc6104;
&rfc6105;
&rfc6106;
&rfc6144;
&rfc6145;
&rfc6146;
&rfc6147;
&rfc6177;
&rfc6164;
&rfc6192;
&rfc6296;
&rfc6302;
&rfc6434;
&rfc6555;
&rfc6583;
&rfc6724;
&rfc6866;
&rfc6879;
&rfc6883;
&rfc6959;
&rfc6964;
&rfc7011;
&rfc7113;
&rfc7123;
<reference anchor="RFC7045"
target="http://tools.ietf.org/html/rfc7045">
<front>
<title>Transmission and Processing of IPv6 Extension Headers</title>
<author fullname="Brian Carpenter" initials="B" surname="Carpenter"/>
<author fullname="Sheng Jiang" initials="S" surname="Jiang"/>
<date month="December" year="2013"/>
</front>
<seriesInfo name="RFC7045" value=""/>
</reference>
&I-D.xli-behave-divi;
&I-D.wierenga-ietf-eduroam;
&I-D.ietf-v6ops-dc-ipv6;
&I-D.ietf-v6ops-design-choices;
&I-D.ietf-opsec-v6;
&I-D.ietf-opsec-ipv6-host-scanning;
&I-D.liu-bonica-dhcpv6-slaac-problem;
&I-D.ietf-v6ops-ula-usage-recommendations;
&I-D.draft-ietf-opsec-vpn-leakages;
<reference anchor="SMURF"
target="http://www.cert.org/advisories/CA-1998-01.html">
<front>
<title>CERT Advisory CA-1998-01 Smurf IP Denial-of-Service
Attacks</title>
<author/>
<date/>
</front>
</reference>
<reference anchor="CYMRU"
target="http://www.team-cymru.org/Services/Bogons/">
<front>
<title>THE BOGON REFERENCE</title>
<author/>
<date/>
</front>
</reference>
</references>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-23 20:46:59 |