Drivers for Transitioning to IPv6

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Drivers for Transitioning to IPv6

by Brady Hicks

Docid: 00018234

Publication Date: 2106

Report Type: TUTORIAL


IPv6 is the successor to IPv4, and is regarded as critical to the Internet’s
continued growth as a platform for innovation and economic development. However,
with a high demand for IPv6
expertise, there continues to remain growing pains in the proliferation of IPv6 applications
and services. Although these issues diminish each year, there remain a number of
considerations in regard to transitioning to an IPv6 deployment. This tutorial
takes a look at some of the factors driving its increasing use.

Report Contents:

Executive Summary

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IPv6 is the most-recent generation of the IP protocol suite, succeeding IPv4 for
enterprise, intranet, and consumer Internet applications. The
protocol – which was originally described in RFC 2460 – is designed to resolve
infrastructure issues and provide streamlined administration, tighter security,
and an enhanced addressing scheme. Other benefits include support for isochronous
(real-time) transmission and multicasting, improved network-level security, auto
configuration, more efficient data packet routing, and embedded Quality of
Service functions.

With proper planning and testing, a migration to
IPv6 can be accomplished with a manageable amount of disruption, as a number of
mechanisms have been developed to ensure compatibility and aid in the
transition. A successful IPv6 deployment still hinges on
the ability of network administrators and integrators to have IPv4 and
networks running in a parallel environment. However, many
organizations will soon need to implement a cutover solution and transition from running
IPv6 in tandem
IPv4 networks. The complexity of Internet and attached IP
intranets are complicating cutover transition strategies. Non-compliant
products need to be phased out as IPv4
applications approach
product-replacement lifecycles. IT personnel also need to be
adequately and rapidly trained in deploying and administering the new protocol.


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IPv6 has a number of features designed to address the shortcomings of IPv4,
including a new IP header format, a larger address space, a more efficient
routing infrastructure, stateless and stateful address configurations, enhanced
security, and standardized Quality of Service (QoS) support. The use
of peer-to-peer, mobile, always-on Internet applications and the
roll-out of wireless data services have driven the need to hasten the
IPv6. Additionally, the deployment of IP-enabled devices in a host of
applications such as smartphones, tablets, and home appliances has challenged the
limitations of
IPv4. IPv6 also provides for enhancements in
areas such as routing and network auto-configuration, more efficient
usage, increased security, and support for real-time data and

Many IPv6 gurus believe that IPv6 and IPv4
need to coexist for another 10 to 15 years and run side-by-side during the
transition. Others, however, feel the demand for IP mobility and other
“killer” applications will shorten the coexistence period to as
little as five years. The Office of Management and Budget (OMB) mandates that US federal
agencies begin to use the IPv6 protocol and, as
the future is now at hand, the OMB mandates are now predicating a
deployment strategy for the private sector.

Since IPv6 is not backwards compatible with IPv4,
organizations will have to change their network infrastructure and systems to
deploy IPv6. Organizations should understand the risks of deploying
IPv6, as well as strategies to mitigate such risks. Detailed planning will
enable an organization to navigate the process smoothly and securely.


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Transitioning to IPv6 provides several potential benefits for current
IPv4-based networks:

  • Addressing – The address field in IPv6 is 128 bits, while
    IPv4 uses only 32 bits. IPv6 also provides three modes of addressing –
    unicast, anycast, and multicast – while IPv4 only permits unicast
    where packets are sent to a specific address. Anycast simplifies
    routing and multicast permits the same message to be sent to multiple
    hosts with a single address.
  • Configuration – One of
    the innovative benefits of IPv6 is how it is configured. While IPv6
    addresses can still be configured manually or leased from a DHCP
    server, there is also an automatic configuration utilizing Universal
    Plug and Play (UPnP). If an un-configured device tries to connect to a
    network that doesn’t offer a DHCP server, the device can look at
    either the network’s router or the other devices on the network and
    determine an address that would be appropriate for it to use. This
    technique is referred to as link local addressing.
  • Performance – The IPv6 protocol is designed so that
    Internet backbone routers will have much smaller routing tables than
    they have with IPv4. Instead of knowing every possible route, the
    tables will include routes to only those connected directly
    them. The IPv6 protocol will contain the rest of the information
    necessary for a packet to reach its destination. IPv6 reduces the
    of header fields by eliminating unnecessary data and expediting
    handling. It is designed to make the protocol more efficient by
    overhead to a minimum. In IPv6, the required components are moved to
    front of the header. Optional components are moved to an extension
    header. This means that if optional components are not used, the
    extension headers are not necessary, which reduces the packet
  • Class of Service – IPv6 provides a flow label to identify
    types for special treatment and also separates congestion-controlled
    from non-congestion-controlled data to aid transmission of
    data, such as multimedia streams. These capabilities, although
    in IPv4 through such mechanisms as RSVP, are central to the IPv6
    structure and will be available on any conforming system.
  • Standardized QoS – The QoS implementation is set up so
    routers can identify packets belonging on an individual QoS
    basis. Routers will have the ability to allocate the necessary
    amount of
    bandwidth to those packets based on the flow/packet QoS
    Furthermore, QoS instructions are included in the IPv6 packet
    This means that the packet body can be encrypted, but QoS will still
    function because the header portion containing the QoS instructions
    not encrypted.
  • Mobility – Mobile IPv6 specifies routing support to
    permit an
    IPv6 host to continue using its home address as it moves around the
    Internet. Mobile IPv6 supports transparency above the IP layer,
    including maintenance of active TCP connections and UDP port

Table 1 compares some of the critical features in IPv4 with those
of IPv6.

Table 1. Features of IPv4
and IPv6



IPv6 Advantage

Address format

32 bit
128 bit
(Hexadecimal notation)

Eliminates needs for IP Classes

Address Space

The American Registry for Internet Numbers estimates that it has exhausted its
supply of IPv4 addresses.1

undecillion (2128) or
(340 trillion, trillion, trillion)

Universally inexhaustible pool of addresses. (e.g. if one trillion IPv6
address were
allocated per second, the IPv6 address pool would last for over 10 million,
trillion years)


for packet protection

becomes the key technology to protect data and control packets

Unified framework for security and more secure computing



broadcast and has different forms of multicast

Better bandwidth efficiency

Mobility Mobile IPv4

Mobile IPv6 provides fast handover, better router optimization and
hierarchical mobility

Better efficiency and scalability; Works with latest 3G/4G mobile

Quality of

TOS using Differentiated Service

Per Flow/Packet

Granular control of QoS

Configuration Manual or use
Universal Plug
and Play (UPnP) with or without DHCP

Operation Expenses and reduce error

Possible Pitfalls

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The initial number of existing IPv4 devices that are not upgradeable to
IPv6 or
that require major transitional integration to an all IPv6
world has begun to diminish. New computers and networking devices are now
fully IPv6 capable. This, however, does not address the IPv6
of a diminishing number of legacy IPv4 devices.

Primary obstacles tend to include economic-related
issues, challenges, related to migration, and security.

Economic Factors

Cost always ranks as a major concern for implementing any new technology.
Though the ultimate necessity for IPv6 remains clear, the need to start
the migration is also becoming a strategic and economic factor. Operating a dual-stack network to
accommodate both versions will be more expensive and probably require more
people than running either version alone. As functionality shifts from IPv4
IPv6, network architecture has to evolve, network management must be
redesigned, and routing protocols need to be changed. This will put an
operational and deployment
strain on many

The costs that will be incurred in the transition to IPv6 are no longer a
matter for debate. The reality is complicated by costs such as
labor resist easy quantification and estimation. In short, the transition
be an expense, possibly very expensive. Organizations such as ISPs can
higher costs than end-user organizations.

Regardless, IPv6 is an
making it less a question of how much it will cost and more of when the implementation

Migration Challenges

More than nine years since the official establishment of IPv6, the standard
still faces difficulty gaining adoption, with Google recently estimating2
that just 35 percent of its users access its services over it.

Renumbering to the new scheme can be difficult to estimate. New devices
with IPv6 preinstalled and will automatically
reconfigure, but many other components such as routers (rules, etc.),
IP addresses in software, and licenses tied to IP addresses will need to be
manually adjusted. The length and complexity of the new addresses will make
configuration work error-prone. Delays in DNS propagation of the new
addresses could
lead to additional problems.

As previously mentioned, many organizations will encounter problems
their large installed base of IPv4 hardware and software systems to IPv6,
may prove labor intensive. In addition, they will have to operate an IPv4
network and IPv6 network in parallel until they can abandon the
predecessor. The very nature of IPv6 makes it challenging to utilize the
systems and it will require organizations to expand their hardware
deployments to
maintain the same capacity. Since IPv6 comprises substantially more address
space than IPv4, it will require additional capacity. For example, older
routers will not be able to support the same number of IPv6 addresses as it
with IPv4, meaning organizations will have to deal with latency and
problems. The effect of IPv6 on quality of service and overall performance
somewhat uncertain, making it difficult for organizations to predefine


IPSec is completely integrated into IPv6. Any
computer that is running IPv6 will support IPSec encryption,
of the computer’s operating system. IPv6 supports authentication and
privacy, providing a basic security level for all applications,
independently of higher-level protocols such as S-HTTP and SSL. It
mandates the use of IPSec.

In some respects, however, network security may get worse before it gets
better for
organizations moving to IPv6. The standard’s anticipated benefits will not
manifest themselves until IPv6 is successfully implemented by partners,
organizations, and so on. Short-term security problems will parallel those
experienced under IPv4 and will likely increase as organizations run both
standards in parallel. This is true simply because running both will
their risk of attack as well as network security requirements.


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IPv6 is designed as a
natural evolution from IPv4. Providing an
transition from IPv4 to IPv6 is crucial for the success of IPv6. During the
transition period, it will be essential to maintain compatibility with the
existing installed base of IPv4 hosts and routers, and to facilitate
communication between the two protocols. Planning and testing are the top steps toward ensuring success.
Transition requires careful planning,
and the full impact on network operation, software, and the budget are needs to
considered. The challenge will be to break down the barriers of “acceptance
comfort zones” that a generation of IPv4-savvy engineers and
developers have grown accustom to. The path of least resistance has
been to make IPv4 adaptable. Transitional strategies
technologies are becoming the focus of equipment manufacturers, service
providers, and developers as further reliance on IPv4 can only lead to
“critical mass” of diminishing resources for Internet growth.

Transition Approaches

The transition process can be approached in one of four main ways:

  • Dual-Stack – A mechanism for communicating with both IPv4 and
    devices coexisting in a dual-layer IP backbone. It supports
    such as Telnet, SNMP, and others over an IPv6 transport. All routers would
    need to be upgraded.
  • Overlay Tunnels (Network Integration) – A technique to facilitate
    deployment and enable communications between IPv6 networks over an IPv4
    network or the Internet. IPv6 traffic is encapsulated within IPv4
    packets for
    the duration of the transit path across the IPv4 network.
  • Dedicated Data Links – IPv6 domains communicate using the same
    Layer 2
    infrastructure as IPv4, but over separate Frame Relay, optical links, or
  • MPLS Backbones – Allows isolated IPv6 domains to communicate over
    MPLS IPv4 backbone. Little change is required to backbone infrastructure
    because forwarding is based on labels, not the IP header.

Transition Model

In a somewhat simplistic model, the transition process could be also
as consisting of two components: transition to IPv6 hosts and transition to
IPv6 routing.

Transition to IPv6 Hosts. IPv6 transition is based on the assumption
that every IPv6 host would have dual stacks: IPv6 and IPv4. Such a dual host
would also have an application programming interface (API) that would
IPv4 and IPv6. The API is likely to be an extension of the current IPv4
API. Implementing an IPv6 stack on hosts and developing IPv6-capable APIs is
essential. These steps, however, are by no means sufficient to make IPv6
useful. In fact, until a sufficient number of networking applications are
ported to IPv6-capable APIs, it would be unrealistic to assume widespread
of IPv6. Therefore, the impact of supporting IPv6 is
likely to spread across the whole TCP/IP stack, from the network layer all
way up to the application layer. Organizations should not underestimate the
amount of effort needed to accomplish this, nor the potential for
software bugs during the modifications.

Transition to IPv6 Routing. Transition to IPv6 routing assumes
deployment of routers that would be able to support both IPv4 and IPv6
protocols and packet forwarding. The routing protocols that are expected to
used with IPv6, at least initially, are mostly straightforward extensions
the existing IPv4 routing protocols. To minimize interdependencies, the transition to IPv6 routing assumes
that there
will be noncontiguous IPv6 segments throughout the Internet. These segments
could be as large as a collection of many routing domains, or as small as a
single IP subnet or even a single host. IPv6 connectivity among hosts in
different segments is supported by tunneling IPv6 over IPv4
(RFC2529). The
use of IPv4 tunnels to carry IPv6 traffic over IPv4-only routers is an
essential component of the IPv6 routing transition.

Other Transition Techniques. Other techniques include
automatic tunnels, configured tunnels, and network address translation:

  • Automatic and Configured Tunnels – IPv6
    transition allows for two types of tunnels: automatic and manually
    configured, where new sites will be reached using mechanisms such as 6to4 to
    determine the egress side address of the tunnel. The use of automatic
    tunnels imposes two important preconditions: IPv6 addresses of the hosts
    that are reachable through automatic tunnels must be IPv4 compatible, and
    IPv4 addresses that are used to form IPv6 addresses of these hosts
    (IPv4-compatible addresses) must be routable. In addition, the use of
    automatic tunnels is currently defined only when the remote endpoint of a
    tunnel is a host. Its tunnel end-points are automatically determined by
    using IPv4 compatible IPv6 addresses as specified in RFC2373. Use of
    automatic tunnels between routers is not defined. The use of manually configured tunnels does not require hosts to have
    addresses that are IPv4-compatible, eliminating two of the preconditions
    associated with using automatic tunnels. A configured tunnel is created by
    manual configuration. This is achieved by building a virtual link (tunnel)
    between two IPv6
    routers. Keep
    mind that as the number of manually configured tunnels grows, the
    of tunnels configured manually would deteriorate.
  • Network Address Translation – IPv4 and IPv6 nodes will coexist for a
    until such time IPv6 becomes a requirement. Meanwhile, native IPv6
    will need to communicate with IPv4 nets even if neither of them supports the
    Dual-Stack approach. The NGtrans Working Group defined translation
    such as NAT-PT (RFC2766) providing features similar to IPv4 NAT features to
    translate between IPv4 and IPv6 addresses (and IP header formats) in an
    or at the edge of the Internet. One technology that supports connectivity in the presence of non-unique
    addresses is NAT. This means it allows each organization connected to
    Internet to reuse the same block of addresses. The use of NAT devices
    allows support of hierarchical routing without requiring wide-spread
    renumbering. The only addresses that would need to be changed when an
    organization changes its Internet service provider would be the globally
    addresses that the organization uses for its external connectivity.
    because information about these addresses is localized to the NAT devices,
    these devices would need to be reconfigured. NAT devices allow the interconnection of hosts that have IPv6-only
    with hosts that have IPv4-only addresses. With assigning globally unique IPv4
    addresses rendered virtually impossible, due to the exhaustion of the IPv4 address
    space, before a sufficient number of the Internet hosts would transition to
    IPv6, then NAT devices allow the transition to continue, even in the
    absence of the globally unique IPv4 addresses.

Deployment Scenarios

In addition to multiple mechanisms of transporting IPv6 over IPv4 core
networks, the following are other deployment scenarios.

  • IPv6 over DWDM Backbones – The deployment of Dense Wave Division
    Multiplexing (DWDM) has the capability of reserving wavelengths for IPv6
    traffic in an IPv4 topology.
  • IPv6 Backbone with Multiple-Protocol Labeling Switching (MPLS) – A
    topology of MPLS (an IETF standard) requires much less backbone
    upgrades or reconfiguration while also supporting connectivity between
    networks. With MPLS networks, forwarding is based on labels rather
    the IP header itself.
  • Native IPv6 – Integration of IPv4 traffic over an IPv6 backbone
    follows similar rules of the IPv6 over IPv4 mechanisms.
  • Tunneling IPv6 over IPv4 – A basic Transition Mechanisms
    for IPv6 hosts and routers that specifies the use of a Dual IP layer
    complete support for both IPv4 and IPv6 in hosts and routers, and
    IPv6-over-IPv4 tunneling , encapsulating IPv6 packets within IPv4
    headers to carry them over IPv4 routing infrastructures.
  • IPv6 to IPv4 Translational Gateways RFC
    3142 –
    A proposal that
    an IPv6-to-IPv4 transport relay translator (TRT). It enables IPv6-only
    hosts to exchange {TCP, UDP} traffic with IPv4-only hosts. A TRT system,
    locates in the middle, translates {TCP, UDP}/IPv6 to {TCP, UDP}/IPv4, or

Deployment Challenges

More ISPs, government agencies,

Web site operators, network equipment vendors, application developers, and
corporations are rushing support IPv6 on their backbone networks. A few years ago,
only a handful of US organizations – including the federal government and a few
leading-edge companies – had deployed IPv6 across their networks. Today,
companies in the US and around the world are coming together to permanently
enable IPv6 for their products and services.

Deployment Opportunities

With the advent of the
smartphone, Wi-Fi, and next generation 4G networks, mobile
services providers are making the capabilities of wireless broadband services to
support mobile applications, an affordable and accessible alternative to
traditional wireline technologies.

From automobiles to refrigerators, coffee makers, and home
climate control systems,  the demand for integrated IP based smart
technologies is anticipated to lead the
in development and growth of mobile applications primarily with respect to voice
and data convergence. As global communications converge
onto a common backbone, namely the worldwide IP networks, the ability to
delivering integrated smart technology services will also be enhanced. Based on the building blocks of  IP and Session
Initiation Protocol (SIP), mobile smart technologies
are gaining momentum as the standard that will
bridge the gap of previously disparate and incommunicado networks.
In addition, the cable and satellite TV industry is transitioning from
traditional broadband based broadcast technologies to IPTV. With the
exhaustion of IPv4  addresses, billions and trillions of IPv6 capable
applications and devices will be needed to keep pace with the explosion of
ubiquitous access applications.

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1Hogg, Scott. "ARIN Finally Runs Out of IPv4 Addresses." September 22, 2015.
2"Google | IPv6." Accessed June 14, 2021.

About the Author

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Brady Hicks is an editor with Faulkner Information Services. He writes
about computer and networking hardware, software, communications networks and
equipment, and the Internet.

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