So Cisco has decided not to wait for ratification of the IEEE 802.3at standard, also known as PoE-Plus, for supplying network kit with more power than can be provided using the older 802.3af standard. They're launching, what they're called enhanced PoE (ePoE) on their switch platforms, because their Aironet 1250 802.11n wireless access point needs just too much oomph from those 802.3af switch ports.

Having a quick natter on the phone with their CTO for Cisco's access networking and services group, Pat Calhoun, he spelt out how they're going to proceed with ePoE. Basically they’re not going to change how power is supplied over the cables, which is something the IEEE standards group is considering for 802.3at. Cisco will use the Cisco Discovery Protocol to negotiate with network devices requiring more than that deliverable by 802.3af. This means that legacy 802.3af-compliant devices will still work, but if the Aironet 1250 AP is not connected with Cisco’s ePoE system, you’ll have to turn one of the radios off. This can’t be done dynamically either, due to how the 802.11 wireless standard works.

So, are there vendors out there whose 802.11n APs can operate at full clip and still conform to 802.3af power requirements? Well, there are some who say they can, but I suppose until you try them out, you’ll never know how it performs in practice. Remember the 802.11n and 802.3at standards still haven’t been ratified yet, making the whole combination look like a bit of dog’s breakfast at the minute.

30 Jan 2008