Aruba Networks is the last major wireless LAN vendor to launch 802.11n fast Wi-Fi wireless LAN products - but it claims to have better power-over-Ethernet support and central switching than the competition.
"This had to be done right," said Roger Hockaday, director of marketing EMEA for Aruba, explaining that a later generation of Atheros' 802.11n draft silicon lets Aruba's access points run in full 802.11n mode on most current power-over-Ethernet installations, saving the cost of power injectors. Meanwhile, an upgrade lets its chassis wireless switch handle up to 32Gbit/s of encrypted wireless traffic, and cope with the higher data rates of 802.11n, he said. Aruba's press release is here.
"The first generation of 802.11n draft silicon used 20W of power if the 2.4GHz and 5GHz radios are both in use," said Hockaday. This was beyond the ability of the IEEE 802.3af power over Ethernet standard, which is rated for around 14W. The current generation of draft 802.11n silicon, in Aruba's AP-124 and AP-125 access points, reduces the chip count, so the power demand has dropped to 17W, which Hockaday says is within the tolerance of most poE kit: "The majority operate at the higher end of the voltage range, and deliver more power than specified."
If the network can't deliver enough power for 17W, the access point will fall back from 3x3 antennas to 3x2: "Aruba's access point will deliver full 802.11n 3x3 MIMO performance in the overwhelming majority of installations, but where the power supplied is insufficient it will gracefully backoff as many functional blocks as necessary to maintain stability," said Hockaday. "In most cases this precludes the need to upgrade PoE infrastructure just to support an 802.11n deployment."
While other companies such as Trapeze have moved to a different architecture which shifts some switching to the edge to accommodate the high bandwidth of 802.11n, Hockaday says that central switching is the best architecture, and Aruba is upgrading its Wi-Fi switches and blades to handle 802.11n capacities. The blades of its chassis switch have had the supervisor function integrated, freeing up slots, so a MMC-6000 Multi-Service controller with four blades can now handle 80Gbit/s of encrypted traffic and 8000 access points, and the MMC-3000 can handle 8 Git/s and 500 access points.
Till now, wired and wireless switches have always adapted to new bandwidth with faster core capability, says Hockaday. "Why would a vendor want to switch at the edge?" he asked. "Cisco and Aruba have the ability to invest in high performance switching at the core, while other wireless switches may be built on PC platforms and the vendors can't afford to get the high performance silicon required for faster core switches."
In fact, Aruba already offers the option of splitting traffic and switching some nearer the edge for situations where it is useful, such as branch offices, he said. "We think centrally switching is the best way, but we give people all the options that are necessary."
Trapeze Networks responded by arguing that upgrades to the central switch are costly and not necessary, if distributed switching can manage the load. "Trapeze customers who upgrade to 11n use the controller they already have installed," said Michael Coci, director of technical marketing at Trapeze. "Aruba customers who upgrade to 11n must buy new APs, plus the controller hardware necessary to support them. That means higher costs, additional hardware, and added customer effort."
"If customers like the centralised forwarding path, Trapeze will certainly sell them hardware that is capable of 802.11n speeds," said Matthew Gast, director of consulting engineering at Trapeze. "The raw data throughput of switch fabrics isn't a barrier for us in the wireless industry. We can all buy switch fabrics that move data through the network at wire speed. The barrier is in performing all the crypto operations for client devices."
Coci likened Aruba and Trapeze's 802.11n upgrades to recent operating system upgrades from Microsoft and Apple: "If I'm a Microsoft customer who wants to upgrade to Vista, because of the heavier requirements I have to buy new hardware. If I'm an Apple customer and I want Leopard, I buy the new OS, and enjoy all the new functionality while running it on my existing hardware. Which vendor's customers are better served - which vendor has the better architecture?"
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