Making the move to IPv6

How one ISP is tackling the transition to a new addressing scheme for the Internet, and what it could mean for you.

The world is about to run out of the IPv4 addresses that are critical to the operation of the Internet. It could happen in the next three months, maybe even two. Why? Because, difficult though it may be to believe, almost all of the more than four billion IP addresses defined in the current addressing scheme are already spoken for.

The allocation of IP addresses is managed by an organisation called the Internet Assigned Numbers Authority (IANA), which allocates them in blocks of 16,777,216 addresses. The IANA hands these blocks to five regional registries to distribute in smaller blocks to their customers. In Europe the regional registry is called RIPE NCC.

Although there has been scaremongering about the exhaustion of the pool of IPv4 addresses, only IANA is really about to run out. RIPE may not run out for a year or more. After that, individual ISPs will still have unused addresses to work with.

ISPs and network operators still need to get their house in order to cope with the IPv6 addressing scheme that has long been seen as the answer to the problem. IPv6 is a 128bit protocol that supports 2128 (about 3.4×1038) addresses, compared to the 32bit IPv4 scheme that only provides 4,294,967,296 (232) addresses. So IPv6 is expected to serve us for a long time.

Nonetheless, there's an immediate engineering challenge to be overcome as we learn to work with the IPv6 scheme, and to manage a hybrid IPv4 and IPv6 offering while the transition takes place.

Timico's experience

Internet service provider Timico has been running IPv6 as part of its research and development activity for a number of years. The core of the network has been running both IPv4 and IPv6 addressing schemes, with connectivity to the rest of the Internet, for most of this time. Attempts to offer these services to our customers have been limited due to the lack of demand, a lack of vendor support and focus on the core IPv4 operations.

Now that IPv4 exhaustion is becoming a reality and IPv6 is maturing, more network providers are starting to work with the scheme. Apart from the larger number of addresses, IPv6 is a much better protocol than IPv4 with attractive features such as: stateless auto-configuration, so that routers do not need configuration and can just plug in and work; mobile IP addresses, so that a machine can roam away from its home network but still look as if it is at home, removing the need for a VPN; and built-in multicast, which removes a lot of the administrative overhead needed to do multicast using IPv4, by incorporating the required protocols within IPv6.


Timico's IPv6 deployment has been evolving since early 2004. Early deployment consisted of turning on a native IPv6 service on the Timico backbone, joining UK6x (a BT-sponsored IPv6 Internet exchange), interconnecting with other networks so that the company's IPv6 addresses could be reached from the rest of the Internet, and testing with any equipment that claimed to support the new protocol.

Early attempts at xDSL deployments in 2005 faced unforeseen issues with domestic routers, causing frequent reconnections and/or loss of sync. These issues were compounded by problems with passing IPv6 through BT's 20cn network, which truncated the v6 packets. This held Timico back from deploying an xDSL service.

Now, at the beginning of 2011, the company has found the situation to have improved greatly. Vendor support is improving and more content providers are ensuring their websites have IPv6 as well as IPv4 addresses. The main core of the protocol's standards has solidified, and over the past year the company has been polishing its deployment practices for what will become its next-generation core. Most of the remaining work concerns policy for such things as customer allocation plans, and new products.

State of play

The core of the Timico network currently runs both the IPv4 and IPv6 protocols side by side (this is known as a dual-stack arrangement) with good external connectivity to hundreds of networks and multiple Internet exchanges.

It has full support for IPv6 over MPLS including support for a range of access network types – leased lines, Ethernet circuits and xDSL capabilities (BT 21cn only). It also has customers using a tunnelled service over their DSL connections, employing generic routing-encapsulation techniques to create tunnels to present native IPv6 addresses to the customer. Timico's monitoring systems and services such as DNS have also been enabled for IPv6.

The dual-stack approach has proven to be the best way to get connectivity throughout the core, and to gain operation experience and test vendor support. A native IPv6 service is far easier to work with than a system of tunnels or transition mechanisms.

Running both protocols at once on the same equipment has had many benefits and as the IPv4 and IPv6 schemes act independently of each other we can safely work on one side of the fence without affecting the other. This system has the added benefit for us that our IPv6 network topology ends up mirroring that of our IPv4 network.

External connections

As an ISP, Timico is in the business of connecting people to the Internet – that is, to other ISP networks. Having obtained an IPv6 allocation from RIPE, its first task was to start interconnecting with other networks and gaining operational experience with IPv6 routing.

The company was present at the UK6x IPv6 Internet exchange, and has been building on the lessons learnt since its closure. It maintains hundreds of peering sessions with other IPv6-enabled networks, and prides itself on maintaining a full IPv6 routing table that currently consists of around 3,500 routes. This compares with around 332,000 routes in the Timico IPv4 routing table. [This is not a like-for-like comparison of the number of routes: the IPv4 address pool is more segmented and thus more inefficient, leading to the need for more routes.]


The multiprotocol label switching (MPLS) protocol, which simplifies routing decisions on the Internet and so enables higher performance connections, forms a big part of Timico's core and is the foundation of its Private Wide Area Network offering. MPLS and IPv6 are both important to the efficient future working of the Internet and must be able to work together. This is done using 6PE – an MPLS technology that allows transport of IPv6 traffic over an IPv4 infrastructure.

It is also feasible to use Mobile IPv6 with MPLS services, which will be of great interest when considering true network convergence.

Timico's core systems already support IPv6. Value-added customer services such as e-mail and web hosting are being overhauled to support IPv6 in the near future. There are still several areas where systems software has not caught up with the evolving network, and the company has sought to keep a close eye on that. Products such as the popular MySQL database don't fully support IPv6 and this can make using them complex.

The scarcity of IPv4 resources has led to the implementation of IP address allocation policies designed to save addresses. Techniques such as network address translation (NAT) have become standard tools for IPv4 deployments, but are not needed for IPv6. This means the company has to rethink its policies for IPv6, including the approach to network security.

It also needs to think again about how it satisfies its customers' needs for connectivity, ease of management, security, and support. This is easier to achieve on some access networks than others. Timico can already offer IPv6 versions of leased line, fixed Ethernet and the majority of our MPLS and PWAN services. IPv6 versions of its xDSL services are still being tested in the lab to ensure quality and reliability.


IPv4 and IPv6 are similar in many ways and learning IPv6 should come easily for most engineers who understand IPv4. However, new concepts such as auto-configuration, neighbour discovery, address planning and sub-netting can be cryptic and have unexpected results.

For this reason, lab tests are invaluable for reinforcing these principles in a safe environment. Training should cover all systems and network disciplines, with departments sharing information freely. It's also important to share the learning freely with other organisations: more often than not both sides win.

The owners of Timico have not found implementing IPv6 too difficult. The company started early, and so have been able to update plans, evolve deployment practices, and budget for new features, software and hardware as they have become available.

IPv6, as a more modern protocol, does bring advantages apart from the size of its address space. These include more efficient routing, better implementation of multicast, which should make broadcasting of data a lot easier, and greater mobility. The vastly increased address space will be a catalyst to connect far more devices to the Internet – which in turn will bring with it new applications and services.

Trefor Davies is CTO of UK ISP Timico. Chris Nicholls is an engineer in the company's network design team.

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