With the ratification of the IEEE802.3at standard this month, Power over Ethernet will be ready to deliver 30W of power per port to a broad range of gear — everything from 802.11n equipment to IP video and thin clients. As such, you need to establish an enterprise-grade POE plan that optimizes flexibility, scalability, energy efficiency, reliability, safety, maintenance and management.
One of the biggest predictors of PoE flexibility and scalability is whether it is delivered via the network switch or through a piece of equipment called a midspan. PoE switches and midspans both deliver the same amount of power over the same distances, in support of the same IEEE specifications. However, today's PoE-enabled switches deliver basic industry-standard PoE capabilities to some or all network ports, with very few options over how that power is managed or budgeted.
In contrast, a midspan is a small, stand-alone piece of standards-compliant PoE equipment that sits between the existing switch and powered devices, and injects power into the data line using significantly more energy-efficient intelligent power management and allocation techniques than are available with PoE switches. Midspans also offer a variety of cost-saving power-infrastructure monitoring and maintenance capabilities that PoE switches do not include.
Typically, midspans offer the most flexible, scalable and energy-efficient solution, especially for first-time PoE deployment. Unless the existing data network infrastructure is inadequate (from a feature, capacity or performance perspective), or you need to simultaneously upgrade both the data and power infrastructure with a new PoE-capable switch, midspans are the best upgrade choice. They require no changes to the existing switch or CAT5 (and above) cabling, and are generally compatible with any Ethernet switch.
Midspans can be used to deploy PoE when PoE-capable switches aren't yet available, and/or if available PoE switches don't support all necessary data features. For instance, many enterprises have upgraded to high-power capability with midspans, even when switches were not yet available.
Finally, midspans decouple the power and data infrastructures for optimal flexibility and scalability. They enable PoE ports to be incrementally added, as needed. This contrasts with the installation of a new switch, for which the prescribed approach is to deploy PoE on as many ports as possible to support future growth.
The latest midspans also incorporate a number of enterprise-grade features that enhance energy efficiency, reliability and safety, flexibility and scalability, and management and maintenance.* Energy efficiency: A poorly designed PoE infrastructure can be a large energy drain. PoE is already the greatest heat generator in most switching closets. Cooling challenges are considered the biggest potential roadblock for widespread high-power PoE deployment.