IPv6 Migration Planning

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Confidential
Not for release to
third parties.

© 2007 OPNET Technologies, Inc.
All rights reserved.

OPNET and OPNET product
names are trademarks of
OPNET Technologies, Inc.
IPv6 Migration
Planning

OPNET Technologi
es, Inc.
7255 Woodm
ont Avenue
Bethesda, MD 20814
www.opnet.com


7/6/2007

Related
OPNET So
lu
tion
s

I
P
v6
Plann
i
ng
an
d
Op
er
atio
n
s


Modu
le
IT Gu
r
u
® Net
w
o
r
k

Pla
nne
r
SP Guru® Net
w
ork
Pla
nne
r
W
h
ite Paper
Title

IPv6 Migration Planning
Confidential
Not for release to
third parties.

Contents
1 Introduction...............................................................................................................2
2 The Motivation and Rationale for IPv6.....................................................................3
3 The Business Case for Planning................................................................................3
4 IPv6 Transition Approaches......................................................................................4
5 Key Steps in the Planning Process............................................................................5
6 What a Planning Solution Should Support..............................................................10
7
OPNET
’s Solution for IPv6 Migration Planning....................................................11
8 Benefits of
OPNET
’s IPv6 Planning Solution........................................................18
1 Introduction
IPv6 is the next major production version of the Internet Protocol, IP. It is the successor to
IPv4, the version of IP in continuous use since the 1980s. (IPv5 was an experimental
protocol never used in production). IPv6 addresses several limitations of IPv4 and also
provides many new features and concepts to improve Internet communications. Some of the
key features include a large address space, efficient addressing, a simplified protocol
header, support for end-to-end QoS and improved security.
In this paper, we will:
• Describe the motivation and rationale for migration to IPv6
• Discuss the need for planning the migration
• Introduce IPv6 transition architectures
• Highlight the key steps in the planning process
• Introduce OPNET’s solution for IPv6 migration planning
This paper does not contain feature-by-feature documentation or detailed descriptions of the
protocols involved. You can find more information about various features described in this
paper in the online documentation that comes with the OPNET products.
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2 The Motivation and Rationale for IPv6
IPv6 was developed in the mid-1990’s by the Internet Engineering Task Force (IETF). It was
primarily engineered to remove the fundamental address space limitation of IPv4. IPv6 uses
128 bits for IP addresses versus 32 bits in IPv4, thus providing a practically unlimited
address space that enables any device to have a unique IP address. This eliminates the
need for network address translation (NAT) as a means to cope with limited address space,
although today NATing also is viewed as a component of network security and is not
expected to go away. IPv6 improves routing efficiency through better address aggregation
that results in smaller Internet routing tables. It also provides better end-to-end security,
improved QoS support, and increased mobility.
In addition to the technological benefits of IPv6 that are motivating the migration, the U.S.
Federal Government has issued a mandate that government agencies’ networks must
support IPv6 by June 2008. While the precise definition of that support may still be evolving,
Federal agencies are taking aggressive steps towards IPv6 migration. Organizations that
collaborate with government agencies have to follow suit.
Governments and organizations in other countries (e.g., Asia and Japan) are further along
the migration path to IPv6 due to limited IPv4 address allocations. Organizations conducting
business in these areas have to support IPv6 communication.
Enterprises are interested in IPv6 as they can take greater advantage of technologies like
telecommuting where several devices will need unique IP addresses.
3 The Business Case for Planning
Any change to an IT infrastructure requires planning. The end-goals of the transition planning
are to:
• Minimize costs
• Reduce the risk associated with the transition and
• Ensure a smooth and manageable transition process
Transition costs include the necessary equipment upgrades (hardware and software), staff
education and operational expenses. There are several technical issues associated with a
transition. In order for a transition to be seamless, your organization must:
1
Ensure that the network has the same rechability and isolation characteristics as
before, i.e., communication patterns are preserved
2
Ensure that the previous level of security is maintained
3
Ensure that network and application performance remains unaffected
4
Ensure that IPv4 and IPv6 can co-exist
5
Ensure that the new network can survive failures as before
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4 IPv6 Transition Approaches
There are several transition approaches provided to manage the transition and support both
IPv4 and IPv6 protocols in parallel during the transition. We introduce a few important ones
in this section.
Dual stack (IPv4 and IPv6 together)
The dual-stack implementation is a common transitional mechanism where all devices
(workstations, servers, routers, etc.) support both versions – IPv4 and IPv6. The applications
and the network can communicate using either version.
This transitional mechanism is relatively easy to implement. Both protocols co-exist and
hence, there is no problem supporting older and newer applications that use IPv4 and IPv6
respectively. The disadvantage of this approach is that the devices have to support both
versions and they need extra processing power (memory, CPU etc.) to handle both
protocols.

IPv6/IPv4 Network
IPv6/IPv4
IPv6/IPv4
IPv6/IPv4
Network
IPv6/IPv4
Network
Router
IPv6/IPv4
Router
IPv6/IPv4

Figure 1. Dual-Stack Architecture (Both versions co-exist)
Tunnels (IPv6 in IPv4)
Tunneling uses encapsulation to carry IPv6 traffic in IPv4 packets and vice versa. This allows
for a partial transition where portions of the network can migrate to IPv6 while the rest of the
network remains in its original state.
The advantage of tunnels is that you can reuse the existing infrastructure in situations where
old devices do not have enough processing power to support both protocols or you are not
ready or financially able to upgrade. The disadvantage of tunneling is that it involves tedious
configuration. Tunnel endpoints need extra processing power to handle encapsulation and
decapsulation. Tunnels can create routing inefficiencies if they are not configured to match
the underlying routing topology. Tunnels also introduce security issues, as packets that were
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previously visible are now encapsulated. Troubleshooting within the tunnel is difficult due to
the lack of visibility into the end-to-end traffic paths.
There are two types of tunnels: static and dynamic. Static tunnels are created manually.
Dynamic tunnels use several techniques to automatically define the endpoints (6to4,
ISATAP, Teredo, TSP Tunnel Broker etc.). Dynamic tunnels involve fewer configurations
than static tunnels. However, they create IPv4 address bindings (when the tunnel endpoints
are derived directly from IPv4 addresses). Providing redundancy with dynamic tunnels is also
a challenge.
IPv4 Network
IPv6/IPv4
IPv6/IPv4
IPv6/IPv4
Network
IPv6/IPv4
Network
Router
IPv6/IPv4
Router
IPv6/IPv4
Tunnel with IPv6 traffic in IPv4

Figure 2. Tunneling Architecture (Tunnels encapsulate IPv6 packets in IPv4)
Translation
Translation lets you convert packets from one protocol to another. The advantage of this
approach is that it allows for communication between devices supporting any version.
However the disadvantage is that the translator has to read every packet header and this
requires extra processing power. Configuration of the translator is tedious. The translator
also becomes a single point of failure.

IPv4
IPv6
IPv4 Network

IPv6 Network
Router
N
AT-PT
Protocol Translation

Figure 3. Protocol Translation Architecture
5 Key Steps in the Planning Process
For any of the transition architectures discussed earlier, there are several key steps in the
planning process. Typically, IPv6 is deployed in stages – i.e., one site at a time. The planning
steps have to be repeated for all intermediate scenarios so that any interim changes towards
the final goal do not cause any disruption to the production network.
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It is expected that IPv6 and IPv4 will co-exist in any architecture for an extended timeframe.
Hence, as you plan to make changes to support IPv6, the plans must keep the old IPv4
configuration and connectivity intact or provide alternatives to allow for IPv4 interoperability.
Identify your equipment needs
Hardware and software must be upgraded to support IPv6. You must make two decisions as
part of this planning step: the devices that need to be upgraded; and the IPv6 functionality
that you would like to support. Vendor hardware and software versions support new features
incrementally. As you conduct the upgrade process periodically, the readiness assessment
should take stock of your network inventory and determine the devices that need to be
upgraded to support a specific IPv6 function. For example, you may want only the core
network devices to support IPv6 QoS. In this case, you may want to check if all the software
versions on the core routers support IPv6 QoS.
Migrate addresses
Existing IPv4 addresses have to be translated to IPv6. With IPv4, address plans were
designed to limit consumption of addresses. With IPv6 however, there is an unlimited
address space. Hence, you can either preserve or modify the addressing structure/hierarchy
as part of the migration. If you change the structure to take advantage of the new IPv6
addressing features, you must correspondingly update any routing and/or security policies
that were based on the old structure.
The addressing scheme can be based on a prefix supplied by a provider or 6to4 prefixes that
are derived using the existing IPv4 addresses if you are using 6to4 dynamic tunnels. The
6to4 schemes let you retain the existing IPv4 hierarchy and structure. You may choose to
start with the 6to4 scheme initially for simplicity and later move onto the provider supplied
prefix for a production deployment. To transition addresses, you will need to:
• Understand the current IPv4 hierarchy and structure
• Understand routing behavior that relies on the addressing structure (address
aggregation, summarization etc.)
• Generate IPv6 addresses based on a provider supplied prefix and some
knowledge of the IPv4 address hierarchy
• Automatically generate 6to4 addresses if you are using the 6to4 dynamic
tunneling approach
Migrate routing configurations
With an addressing structure in place, routing configurations have to be migrated from IPv4
to IPv6. To transition routing, you must:
• Select routing protocols and configure their parameters
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• Identify and change routing configurations where they were previously dependent
on IPv4 addressing structures (e.g. address aggregation, summarization etc.)
• Change routing policies that previously applied to IPv4 packets to now work on
IPv6 traffic or encapsulated IPv6 traffic
Ideally, the routing topology of the IPv6 network matches the IPv4 network. Typically
however, the routing topology can change if the addressing hierarchy changes or if you use
tunnels. This implies that you may have two sets of routing policies – one that applies to IPv4
traffic and another that applies to IPv6 traffic.

Router
Router
Router
Router
Router
Router
Router
Router
Router
Router
Router
Router
Routers supporting IPv6 (yellow)
This network supports IPv4 only
IPv6 communication paths
IPv4 communication paths
Routers supporting IPv4 (blue)
This network supports IPv4 and IPv6

Figure 4. Routing topology in a IPv4-only network (left) and an IPv6/IPv4 network
(right)
Verify network reachability and isolation
In a seamless migration, the network’s reachability and isolation characteristics should be
preserved. However, if there is any change in the addressing structure or routing topology,
portions of the network that were previously reachable may have lost connectivity. You
should compare the routes before and after the transition. Devices that were previously
reachable (or not) should continue to be.
Additionally, although devices in the new network can talk to each other as before, their
communication paths may have changed. Tunnels in particular can create routing
inefficiencies (tunnels may take longer paths). This can affect network and application
performance.
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Route
r
Route
r
Route
r
Route
r
Route
r

Route
r
Route
r
Route
r
IGP Shortest Path (4hops)
Tunnel path (5 hops)
Tunnel endpoints

Figure 5. Tunnels may select less optimal paths
Analyze network performance
IPv6 creates additional overhead due to the altered protocol headers. The IPv6 header
(without extensions) is 40 bytes and is double the size of the IPv4 header of 20 bytes.
IPv4 Header (20 bytes)
32 bits
128 bits
IPv6 Header (40 bytes)

Figure 6. Comparison of IPv4 and IPv6 protocol headers
Additionally, tunnels add encapsulation overheads. This results in an increase in traffic
volume.
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IPv4 Header
IPv6 Header
Transport header and Payload
20 bytes added due
to tunneling
Original packet

Figure 7. Tunneling adds the extra IPv4 header due to encapsulation
The protocol overhead affects link utilization significantly if the average network packet size
is small (e.g. a network with many small VoIP packets) or if the traffic paths change.
Path changes can occur due to changes in the address structure, routing configuration or if
tunnels are added. As a result, new links that become over utilized will need to be upgraded.
Alternatively, traffic engineering schemes can be implemented to move traffic from those
links onto less utilized paths.
Plan a resilient migration
Critical traffic in the IPv6 network should be adequately protected. You would need to
understand what happens if any resources critical to the transition strategy fail (e.g. tunnels,
dual-stack routers etc.). IPv6 migration can concentrate network vulnerability on fewer critical
resources, so failure scenarios of these critical resources should be evaluated.
Migrate security policies
Maintaining security during the transition is of utmost importance. Security policies (e.g.
packet filters, route filters) must now deal with the old IPv4 communications and the new
IPv6 traffic paths. If the routing topologies are different in the IPv4 and IPv6 network and a
route filter relied on any hierarchical routing, the rule should now be translated to handle the
routing structure for IPv6.
During the planning process, you must first identify and understand the existing security
measures. These measures must then be translated to work on the new packets. The
packets may be native IPv6 packets in an IPv6-only domain or they maybe IPv4 packets
carrying encapsulated IPv6 traffic in an IPv4 domain. In the latter case, the policy must first
check if there is an embedded packet and then read the embedded IPv6 header before
applying the rules.
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R
R
R
R
IPV6 domain
IPV4 domain
Policies implemented in an area already converted to v6
R
R
Tunnel
R
R
R
R
IPV6 domain
IPV4 domain
Policies implemented in a IPv4 domain carrying IPv6 traffic
R
R
Tunnel

Figure 8. Policies may be located in a IPv6-only domain or in an IPv4 domain carrying
IPv6 traffic
Analyze application performance
The migration can result in new traffic paths. Application packet sizes will change due to new
MTU’s, fragmentation schemes and the additional overhead imposed by the new IPv6
datagrams. This in turn affects application response time. Any changes to application
performance must be monitored carefully to ensure that they do not exceed SLAs or create
user dissatisfaction.
6 What a Planning Solution Should Support
To support the key steps in the planning process discussed in the earlier section, a planning
solution should have the following features or characteristics.
• An operationally correct representation of the network in its present state
(topology, routing configurations, optionally traffic). The network should represent
the IPv4 routing configuration and traffic paths correctly
• Support to introduce the new IPv6 architectures (dual-stack, tunneling, etc.)
• A detailed routing model that recreates routes based on the combined IPv4 and
IPv6 configurations
• Support for the co-existence of IPv4 and IPv6 architectures in the same network
• Support for a variety of underlying networking technologies (Frame Relay, ATM,
MPLS etc.)
• Key metrics such as link utilization as well as SLAs for key metrics
• Ability to view the new paths for traffic in the IPv6 network
• Detailed reporting on what equipment changes have to be made to support v6
technologies (hardware and software upgrades)
• Detailed before-and-after reporting on the changes to the network and
applications as a result of IPv6 deployment, as well as visual aids for easy
understanding and presentation
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• Ability to plan incremental migration (turn on IPv6 selectively)
• Ability to fail devices or links and analyze whether survivability characteristics of
the network have been adversely impacted by the migration
OPNET’s IPv6 Planning and Operations™ Module supports the above features and lets you
plan your migration effectively.
7 OPNET’s Solution for IPv6 Migration Planning
OPNET’s IPv6 Planning and Operations™ Module allows you to build an operational model
of the IPv4 network automatically from device configuration files, which are typically readily
available (note: OPNET’s VNE Server® solution can be used to gather these files directly
from your devices) and takes you end-to-end through the transition steps. The solution
consists of two major components:
• The IPv6 readiness assessment
• The IPv6 migration planner
The IPv6 Readiness Assessment
The IPv6 readiness assessment checks device OS configurations to see if they are ready to
support a set of IPv6 features specific to network requirements. You must first select the
IPv6 features you intend to deploy and the devices or sections of the network where you
would like to apply the features. The assessment then executes a series of rules that check
the device configurations and generate reports. The output helps you gauge the amount of
work necessary to attain an operational implementation of IPv6 in your network. Additionally,
you can define and create your own rules.
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Figure 9. Features to consider for readiness assessment (left) and a sample report
(right)
The IPv6 Migration Planner
The IPv6 migration planner breaks down the complex migration steps using an easy-to-
understand wizard. The wizard steps include a pre-deployment analysis, device selection,
tunnel/address/routing and traffic configuration followed by reporting options.

Figure 10. The IPv6 Migration Planner
The pre-deployment analysis lets you know which devices are already configured for IPv6.
The device selection lets you select devices and apply IPv6 incrementally.
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Figure 11. Pre-deployment analysis output
Following device selection, you can select the tunnel mechanism (6to4, manual, etc.), define
the tunnel endpoints and choose the interfaces that originate and terminate the tunnels. The
software performs a topology analysis based on the selected nodes and determines if
tunnels are necessary and recommends a tunneling mechanism.
The addressing features within the wizard let you see the existing IPv4 address structure
with several constructs (IP subnets, AS numbers, etc.) and apply a new address plan
interactively. Addresses can be auto-generated based on a user-supplied prefix or using the
6to4 translation scheme.
Routing configurations are automatically migrated using the existing IPv4 routing structure or
alternatively, you can select new IPv6 routing protocols. Once the protocols are selected, the
protocol settings are automatically configured on the selected devices.
The traffic configuration lets you selectively convert IPv4 traffic to IPv6. During this process,
IPv4 traffic is scaled proportionally to account for the IPv6 protocol overhead.
The software then uses analytical techniques and algorithms to model steady state network
behavior. This solution recreates the device routing tables from detailed configuration
information. Individual traffic flows possess detailed attributes such as source, destination
and packet rate. The resulting reports can be used to study routing and reachability across
the network in steady state, and in scenarios with one or more failed devices.
The software supports several underlying IPv6 technologies –dual-stack, manual tunnels,
6to4 tunnels and 6PE tunnels. Support for routing technologies includes OSPFv3, RIPng,
and IS-IS.
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The output consists of several visualizations and reports. We discuss a few of the more
important ones here.
Visualizations include the IPv4/IPv6 address types, IPv4/IPv6 routing protocols and “before
and after” routing paths. The visualizations help you understand how the routing topology
has changed and any route changes that affect performance.


6to4 addresses
IPv4 addresses

Figure 12. Visualization of routing protocols and address types


Traffic path before IPv6
Traffic path after IPv6

Figure 13. Illustration of before-and-after traffic paths - Tunnels can create
routing inefficiencies
Reports include the IPv4 and IPv6 addresses, an inventory of the configuration (tunnel
configuration, routing protocols, routing policies, security policies, etc.) and network
performance before and after. The reports assist you in understanding the impact of change
on network performance and support a cost-benefit analysis of the transition for
management. Detailed engineering reports on the address plans and routing configurations
are useful for the operations staff. Figures 14-20 show sample reports generated by the IPv6
migration planner.
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Figure 14. Tunnel configuration

Figure 15. IPv6 addresses

Figure 16. Change in performance relative to the baseline
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Figure 17. Utilization levels before and after the migration

Figure 18. Breakdown of link utilizations in the network
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Figure 19. Traffic composition

Figure 20. Traffic volume before and after the migration

Figure 21. Breakdown of traffic volume in the network
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OPNET’s survivability analysis provides the ability to configure individual failure events or
perform an exhaustive failure analysis by iterating through all possible failure scenarios. You
can select the devices crucial to the transition strategy (e.g., tunnel endpoint devices) and
perform a failure analysis on these specific elements (links or nodes). Alternatively, you can
perform an iterative failure analysis on all elements. The analysis identifies critical failures
and provides several high-level as well as detailed reports on the impact of the failure.


Figure 22. Survivability scores before (left) and after (right) the migration
The analyses discussed until now are based on OPNET’s Flow Analysis capability, which
models traffic as flows. Flows can be aggregated volumes of traffic, or can be detailed
enough to represent individual applications. In Flow Analysis, the individual timing and
handling of each packet by the network is not modeled. However, the planning solution also
supports discrete-event simulation (DES). DES provides a dynamic model that explicitly
simulates packets and protocol messages. This permits application response times for
normal and failure conditions to be generated by overlaying an application trace on the new
network and simulating using DES.
The software’s modeling framework lets you create any number of scenarios to represent the
deployment stages. The workflow can be repeated on all the scenarios to ensure that
intermediate steps to not cause any problems.
8 Benefits of OPNET’s IPv6 Planning Solution
IPv6 is a technology that offers many new, powerful features. Migration to IPv6 involves
several steps that need careful consideration and planning. OPNET’s IPv6 Planning and
Operations™ Module lets you plan your migration so that it is smooth and seamless. The
IPv6 readiness assessment and the IPv6 migration planner let you make choices and
evaluate them prior to production deployment.
There are several advantages to using OPNET’s IPv6 Planning and Operations™ Module.
• The planning environment is a safe, easy and cost-effective way to try candidate
IPv6 deployment and migration strategies without any effect on the production
network
• The simulation-based approach provides the capability of measuring application
and network performance under different situations and can be used to prove that
a particular migration strategy will not disrupt service level agreements.
Page 18 of 19
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W
h
ite Paper
Title

IPv6 Migration Planning
Confidential
Not for release to
third parties.

• The planning environment offers the ability to carry out a “virtual migration” on an
incremental basis, deploying IPv6 site-by-site. Using the software, your
organization can ensure that the deployment sequence is viable and decide on
the most effective sequence without a trial-and-error process in production.
• The OPNET products have a number of visual aids, and summaries that are
useful to understand the deployment process. These reports can be used to
effectively present a deployment approach to management, coupled with
quantitative data concerning the impact of the migration.
• Ensuring that the network meets service level agreements (SLA) with respect to
application performance is of utmost importance to the organization. However, it
is a complex problem, and generally one that is not easily analyzed using manual
techniques. The Planning environment offers the ability to predict the impact of
the migration on application performance.
• The planning environment can act as a training ground for staff as they come up
to speed with the new technology. Staff can “try” a variety of configurations to
understand the key features of the protocol without affecting the production
network.
CONFIDENTIAL INFORMATION
DO NOT DISCLOSE, FORWARD, DISTRIBUTE, SHARE, OR MAKE COPIES OF THIS
DOCUMENT IN WHOLE OR IN PART. This document contains confidential information and
may contain information that is proprietary, privileged, and/or exempt from disclosure under
applicable law. This document is intended for the exclusive use of the person to whom it is
disclosed. If you are an unauthorized person, you are hereby notified that any viewing, copying,
disclosure or distribution of this information may be subject to legal action. All unauthorized
persons must immediately destroy the original documentation without making any copies or further
unauthorized disclosure.
Page 19 of 19
© 2007
OPNET Te
chnologi
es,
In
c.

All righ
ts r
e
serv
ed.

OPNET and
OPNE
T produ
ct
names are tradema
r
ks
o
f


OPNET
Tech
no
log
ies
,
In
c.