Transitioning a WAN to IPv6
By Stan Barber
Vice President, Engineering Operations
Global IP Network
NTT Communications

As you have read here and elsewhere, companies are beginning to offer IPv6 transition services to help an enterprise determine how to best exploit the capabilities of IPv6. In many cases, this work will outline the steps to take to integrate IPv6 into an existing corporate network running IPv4. NTT Communications is also offering an IPv6 transition service, but our capabilities center on our specific expertise in integrating IPv6 on an existing wide-area network. We do this because that is the locus of our practical experience.

Every day, we are operating one of the world’s largest commercial IPv6 networks and we know from actual real-world experience the specific details both architecturally and operationally what it takes to be successful in enhancing an existing network infrastructure to support both IPv6 and IPv4. We have been developing this expertise for more than a decade, and used that to transition our own network worldwide in 2003.

Our process for bringing IPv6 into an existing network centers on the same basic principles that many others are citing in their literature. First, you must be sure you fully understand the network that is operational today. That includes an inventory of the hardware and software that make up the network, but it also includes the current configuration of the hardware and software and the principles used in operating that network. These include change management as well as troubleshooting management. Once there is a thorough understanding of what exists, it is important to use that as a basis for determining what the new network (with IPv6) will be. Here you make decisions about architecture (e.g. dual-stack vs. overlaying IPv6 on the existing network) and any additional operational changes (e.g. monitoring the network via IPv6 instead of IPv4) that are relevant.

Planning how to get from the current state to the new end state is the next step. This is multi-dimensional project planning development activity coordinating diverse resources. The complexity of this task directly increases as the differences between the current network and the proposed final network increases. During this planning process, it will be a good time to break the project up into several phases with interim results that can be used as ways to step the various parts of the organization’s support teams from the current network to the new, final network. This is also a good time to review and replace any existing practices that don’t work with new ones that do. Using an incremental approach is a key feature of the NTT Communications transition strategy, as we strongly believe that will minimize any negative impact of the transition on the existing production network service.

Transitioning a WAN to IPv6 has some unique challenges that may not be seen when transitioning a large LAN. For example, WANs generally have to make use of some sort of active routing protocol (e.g. RIP, OSPF) to ensure that all parts of the network know how to reach all other parts of the network. There may also be multiple paths between any two points with some paths preferred over others. Using the IPv6 version of the routing protocol already in use on the network for IPv4 (e.g. OSPFv3 for IPv6 if OSPFv2 is used for IPv4) helps to simplify the transition since the IPv6 version is generally very similar to its IPv4 predecessor and the same management techniques can be leveraged in defining the parameters for IPv6 routing as those used for IPv4. This strategy should be used wherever possible in order to exploit the existing expertise of the enterprise’s existing network engineering and operations resources.

During the planning process, it is important to identify the resources with the enterprise that will need training on IPv6 and how the project will affect their day-to-day activities. This training is a vital key to a successful transition activity and must be customized to fit the individual needs of the enterprise. As with the transition activity itself, NTT Communications recommends an incremental training approach that equips the relevant staff with the necessary understanding of those things that impact the operation and support of the network just prior to the implementation phase where those skills are needed. This helps facilitate a successful transition by keeping the intensity of the training manageable and also serves to reinforce previous training sessions throughout the transition project. Using this approach helps the staff successfully integrate what it learned during training with the practical day-to-day activities of supporting the network as the IPv6 capabilities are brought into the production environment.

Generally, individual end-users of the network should not require specific IPv6 training. A properly constructed transition strategy should make the introduction of IPv6 transparent to how end-users use the network today. However, circumstances may be present that would make it impossible to avoid end-user training. This should be discovered during the planning process and then integrated as part of the training activity.

At this point, the project plan has been completed and is ready for review and approval by those in the enterprise that will be both participating and affected by the transition work. It is imperative that each group has a chance to review and approve the project plan so that the project manager can properly marshal their resources when it comes time to execute the plan.

Once the approvals are in place then, the hard work of implementation begins. As described above, the implementation and training activities should be incrementally integrated so that the necessary training is provided shortly before the phase where that training is put into practice commences. At the end of each phase of the implementation, there is an assessment done to determine if there is any remedial work needed before progressing to the next phase. Such remedial work may be required due to unanticipated changes from external factors like new business opportunities. This remedial work may also affect the rest of the project and may require revisions in the remaining part of the plan before proceeding to the next phase.

The project manager and the team supporting the implementation have to be prepared to take the time to do these evaluations in order to assure the least amount of negative impact on the production use of the network.

Once all phases are successfully completed, a transition has been done and the network has been evolved to support IPv6!

The NTT Communications IPv6 Transition Consultancy helps you in your IPv6 planning and transition activities. For more information, please contact us at ipv6@us.ntt.net.