We previously discussed the impact of the different sizing policies on user's Quality of Experience (QoE). Let's now understand its consequences on budget: would the impact be insignificant, IT managers should actually decide not to care about oversizing.
Continuing the example of the preceding post, we can size our access line (equipped with an efficient traffic management system able to differentiate applications) from three different points of view:
- Usage-based sizing (aka 'Oversizing'): the performance is good for all applications, including recreational ones. The bandwidth demand being uncontrolled, inflation is high. It starts at 10 Mbps, with a demand increasing by +10% per quarter.
- Rightsizing: the performance is excellent for all business applications, and a few degradations are accepted for non critical ones. While significant, inflation is more reasonable than when Facebook and Dailymotion lead the demand. It starts at 4 Mbps, and inflates at 8% per quarter.
- Undersizing: the performance is 'acceptable' only for critical applications with important brownouts for others. Inflation is small. Access starts at 2 Mbps and demand inflates at +6% per quarter.
The combination of the different ingredients (initial traffic, demand inflation and available thresholds proposed by Telcos) leads to the following access bandwidth over a 3-year period:
We consider here bandwidth price ranging from 2,000€/month (@2 Mbps) up to 8,000€/month (@40 Mbps). This provides 3-year cumulated expenses of approximately 200 k€ (oversizing), 120 k€ (rightsizing) and 90 k€ (undersizing).
Rightsizing provides savings of 40% compared to uncontrolled access Oversizing, with an excellent QoE. Undersizing proposes 55% of savings to Oversizing scenario, at the detriment of application performance.
To finally decide about her/his sizing policy, the IT manager needs to balance bandwidth expenses with the cost of application brownouts. As this point may be a bit controversial, I realize it would deserve a dedicated post, to come soon…
Illustration: Charlie Chaplin in "Modern Times" (1936)
Comments