Capacity Planning –
What are the keys to effective capacity planning?
What Type of Network Pro are you?

Guest Author:
Jim Metzler
Industry Analyst, Ashton Metzler & Assoc.

WAN capacity planning is a somewhat unique network management function particularly when compared to a management function such as troubleshooting. As an example, effective troubleshooting typically requires a deep understanding of a variety of technologies, effective capacity planning actually requires a combination of technical and business acumen. Given that it is a somewhat unique management function, it’s reasonable to ask: What are the key steps on the road to successful capacity planning?

To exemplify the key steps let’s reference a hypothetical company called TightBudget. One of the first tasks that TightBudget has to perform in order to be successful with capacity planning is to establish targets. For example, TightBudget could establish the target that none of its WAN links will run at greater than seventy percent utilization or no WAN link will exhibit more than 80 milliseconds of end-to-end delay. Of course, it makes no sense for TightBudget to establish targets if it doesn’t have the tools and processes to measure the WAN links to see where they stand relative to those targets.

As part of establishing targets, TightBudget has to be able to answer the question: What happens if we exceed those targets? A generic answer to that question is that if the WAN links exceed their targets the performance of the applications that run over those WAN links will degrade.

However in order to get the approval to spend money to add WAN capacity TightBudget needs to be able to provide more than just a generic answer. That leads to a second key step, TightBudget needs the tools and processes to understand what is running over the WAN links. For example, if what is running over a particular WAN link is a file transfer that isn’t time critical, then exceeding those limits will allow the company to put off spending for an upgrade without negatively impacting any users. However, if what is running over a particular WAN link is a time sensitive, business critical application, then exceeding those limits will likely negatively impact the business.

The next step is to work out a number of details in ways that both ensure an acceptable user experience and will be accepted by TightBudget’s major stakeholders. One detail is determining if there should be a single target for all WAN links or if there should be multiple targets based on factors such as the length of the links, the cost of the links or the applications that run over the links.

Another detail is determining when a circuit should be upgraded. Should it be upgraded when utilization or delay get close to the target? When they exceed the target, even if that is momentary? Or when they exceed the target for an extended period of time?

The final step in creating an effective capacity planning process is perhaps the most difficult: TightBudget’s network organization must establish and maintain trust with the people who set the IT budget and the people who approve circuit upgrades. Most network organizations go through a budgeting exercise just prior to the beginning of their fiscal year. Projecting forward previous increases in WAN traffic combined with applying the previously described capacity planning methodology enables network organizations quantify how much of an increase they need in their WAN budget.

Whether or not they get their budget approved depends in part on whether or not they have developed trust with the people who approve the budget. In addition, even if they are successful and get the WAN budget approved, most network organizations still need to ask permission prior to spending the budget. The capacity planning process described here can help network organizations justify spending the money, but again, only if the people who approve the expenditures trust the process.

To build the trust that necessary trust to get budgets approved and to get permission to spend money, TightBudget’s network organization needs to work with the appropriate stakeholders to help them understand and accept each step of the process. This includes how the targets were set, what happens if the targets are exceeded and what the organization is doing to monitor the WAN links and take action when needed, but no sooner than is needed.

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