The IT Law of Holes: Stop Digging and Start the Technology Migration

Eventually, you'll need to retire the legacy systems and make that technology migration. Embrace the Law of Holes and learn how to set your cap-and-grow strategy.

Jeff Loughridge

May 21, 2012

4 Min Read
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IT leaders make investment decisions based on which technologies are positioned to support the business. They're faced with decreasing per-unit capex/opex costs and increasing requirements for bandwidth and computing resources. Older technologies yield to newer versions that are faster, more flexible and easier to use. But how do you know when it's time for a technology migration?

This may sound familiar: Your business relies on a 15-year-old networking technology. A newer version or a functional replacement has been available for five years. The older version is beginning to show its age in its ability to meet technology and business requirements. You find yourself in a situation in which:

  1. Engineers who understand the technology are more difficult to find, and thus more expensive.

  2. Support costs are rising as the vendor focuses on newer technologies.

  3. Network hardware is approaching end-of-life status.

  4. The technology barely meets today's performance/throughput requirements.

  5. Internal support costs are rising.

I've worked with clients who see that the legacy networking technology should be ushered out. While they may recognize the problem, the dollars required to fund a transition effort are removed from the budget year after year. Why? The pain may not yet be acute, and other items in the budget may appear much more pressing. However, the delay means that once the migration does take place, it will be more costly and complex.

These companies may not have internal staff members who can make the case for migrating from older technology. The complexity of the technology migration effort may be so daunting that no one is willing to risk his upward mobility to advocate it, lest it exceed the budget and miss the targeted completion date.

In many cases, my advice to clients follows a networking law that I call the Law of Holes: When you're in a hole, stop digging. Sounds simple, right?

My law is based on a cap-and-grow strategy: Cap your spending on the old technology. Invest in the technology that represents the future. When an abrupt stop in spending isn't possible, severely restrict it, preferably backed by a mandate that any spending on the legacy technology must be approved by the CIO. This signals to the organization that leadership stands behind the technology migration effort and sees its success as crucial.

Next: The Cap-and-Grow PhilosophyFor cap and grow to be viable, the two iterations of the technology must be able to operate simultaneously. There is no requirement for a flag day in which a complete migration must be performed. Side-by-side operation could be enabled by a translation mechanism, a gateway that unites the two technologies, or a segmentation in which the technologies operate independently.

For example, enterprises have long relied on time division multiplexing (TDM) circuits for WAN connections. Fractional T1s, T1s, DS3s and OC12 circuits are examples of TDM circuits.

TDM WAN has numerous disadvantages: TDM provisioning is slow--the time to obtain or upgrade a TDM circuit is often measured in months. Upgrade increments aren't granular. The next upgrade for a DS3 circuit (45 Mbps) is an OC3 (155 Mbps). Using multiple DS3 may be an option for bandwidth in between 45 and 155 Mbps, although discrete circuits can have repercussions on load balancing.

While TDM may dominate your enterprise WAN circuits, Ethernet is the technology of choice in the LAN. The network builds in the last eight years have resulted in a sizable Ethernet footprint for the U.S.'s top metropolitan areas. Ethernet is quickly emerging as the preferred WAN access technology. Ethernet cards for your WAN-facing routers are inexpensive. These circuits can be upgraded in small increments, and these upgrades usually involve only a few keystrokes by the provider. No more waiting months for bandwidth upgrades.

How might a cap-and-grow strategy work in an enterprise moving to Ethernet? For any upgrades to circuits to headquarters, data centers and other heavy-bandwidth sites, the business can switch to Ethernet access. TDM and Ethernet access circuits can be used simultaneously for WAN access, so there are no compatibility concerns. Branch sites can also move to Ethernet access in metropolitan areas, where the prices for Ethernet access have fallen rapidly.

I mentioned exceptions in my description of cap and grow. If you have branches with low-bandwidth needs, you may want to stick with TDM access, as the price-per-meg of Ethernet will likely exceed TDM for speeds under 6 Mbps. Don't forget to evaluate business cable service. Many of my clients are very satisfied with a business cable service. The handoff is Ethernet--just as it is in your home for cable Internet--so it can be very similar to Ethernet access from a provider such as the local exchange carrier.

My Law of Holes has many applications in IT--think IPv4 to IPv6, TDM telephony to VoIP, and traditional IT operation to cloud computing. If you recognize that a migration is needed, advocate for a technology migration. Show your organization why it's time to stop digging.

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