Cisco develops own power-over-Ethernet standard

The proprietary "enhanced power over Ethernet" standard can power wireless access points designed for the 802.11n draft over the LAN.
Written by Richard Thurston on

Cisco has developed its own proprietary standard to support the latest wireless access points, the company said on Wednesday.

The latest wireless access points, designed for the 802.11n draft, cannot be effectively powered using current switching equipment. 802.11n-based equipment may prove attractive for businesses because it offers up to 300Mbps throughput.

Access points have traditionally been connected via mains electricity, but many new installations are powered over the LAN, using a technique known as "power over Ethernet" (PoE).

PoE can only support devices which use less than 15.4W. This includes older access points but, to work effectively, 802.11n-based access points require 18.5W. Businesses wanting to power 802.11n access points have had to disable one of the two radios, which decreases throughput, or else use two switch ports or a separate power injector.

But Cisco now claims to have overcome these problems by supplying 18.5W over the LAN. The power is carried in the spare copper pair which does not carry data.

Although Cisco is a member of the IEEE's PoE standards group--responsible for a global effort to standardize PoE technology--this development has been undertaken separately.

Cisco's go-it-alone effort reflects its history with the technology. Cisco initially developed its own PoE standard, which it called Inline Power, before giving in to competition and adopting standardized PoE in its switches.

The IEEE is developing a separate high-speed standard called PoE Plus, which will support approximately 30W and is expected to be finalized in around 12 months' time. Cisco said it is involved in the IEEE's PoE Plus discussions.

The company said it developed its own high-power technology, which it has named "enhanced PoE", because it had released its own 802.11n-based access point. The Aironet 1250 was released in September 2007.

"The 802.11n standard is out already, so we had to make the switching capability available to customers," said Inbar Lasser-Raab, senior marketing director in Cisco's access routing and switching division.

Lasser-Raab claimed that there would be no interference caused to data by the higher power usage.

Enhanced PoE is included with current Catalyst 3750 and 3560 switches, and will be included on the Catalyst 6500 and 4500 switches from the middle of this year, Cisco said.

Businesses that currently own those switches can install the feature for free via a software upgrade.

Cisco has also built PoE capability into its 2960 switches, but the feature will incur a substantial price premium.

A 24-port 2960 with eight PoE ports is priced at US$1,795, while the same switch with 24 PoE ports sells for US$2,995. Enhanced PoE is not currently available on the 2960.

Cisco has also introduced a small switch which can be powered over the LAN by other switches. The 2960 PD switch is intended for deployment in areas where there is no mains power. It has eight ports, of which one must be given up to bring in the power from the supporting switch. It will be sold at US$795.

Lasser-Raab recommended that, as with any PoE deployment, all redundancy options should be considered to avoid a mains outage taking down the network.


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