Apple has made fast even faster. The AirPort Extreme Base Station, in its first incarnation, achieved unprecedented speeds for Wi-Fi network transfers, topping 90 Mbps of actual throughput in ideal circumstances. Even in less-than-perfect conditions, the Extreme — with a recently updated draft version of the 802.11n standard — beat its 802.11g predecessor.

Apple has refreshed its previous Base Station by upgrading Ethernet from 10/100 Mbps to 10/100/1000 Mbps, offering Gigabit Ethernet in parity with the speed found on almost the entire Mac lineup. The lack of Gigabit Ethernet was our biggest carp in our last review.

This new model goes beyond improving just the wired side of the network. By adding Gigabit Ethernet, Apple took the governor off the top of the Base Station’s engine, allowing it to shoot far above the previous model’s limits. Apple AirPort Extreme network adapters can now top 140 Mbps of throughput in an ideal case. As we speculated in our earlier review, internal Ethernet speeds restricted 802.11n’s top rate.

For this review, we ran the same tests we performed previously, and we added some new ones. The ideal case tested then — as now — is with the Base Station set to use the 5GHz spectrum band, one of two alternatives. The other choice, 2.4GHz, is crowded with older Wi-Fi networks, Bluetooth device transmissions, cordless phones, and other interferers.

In the 5GHz band, the AirPort Extreme can use a wide channel, employing twice the frequency as standard 802.11b and 802.11g channels. This enabled us to achieve a consistent rate of 140 Mbps from the AirPort Extreme 802.11n network interface in an Intel Core 2 Duo Macintosh transmitting to a Gigabit Ethernet-equipped Mac attached to a local area network (LAN) port on the base station.

We found that speeds between two Apple 802.11n adapters remained high, but unchanged: around 90 Mbps throughput when sending a stream of packets from one wirelessly connected Mac to another, and about 50 Mbps when sending simultaneously between Macs.

(Except the 17-inch 1.87GHz iMac, all Macs with Intel Core 2 Duo processors include 802.11n. It’s a build-to-order option on the Mac Pro. Macs purchased before this summer may need to install the 802.11n enabler, which is included on the disc that ships with the new Base Station. There is no Mac-compatible, third-party 802.11n adapter that handles 5GHz signals, although QuickerTek offers 2.4GHz 802.11n cards and USB dongles.)

Performance in the busy 2.4GHz spectrum band was erratic due to real-world congestion where the Base Station was tested. After achieving poor performance, an Apple product manager suggested that we manually choose a Wi-Fi channel, rather than allowing the Base Station to pick an unused location via the default Automatic setting. (The device scans only for Wi-Fi networks, not other interference.)

Setting the device to channel 1 (out of 11 possible channels in the United States) made it practically unusable. Even using a spectrum analyzer, which can reveal all signals passing over the 2.4GHz band, we found no continuous interference. This presented a mystery that has remained unsolved.

Setting the Base Station to channel 11 relieved the problem, although speeds were much lower than those we’ve seen previously. We weren’t even able to achieve 50 Mbps between two Apple 802.11n adapters in one direction, and we got only 35 Mbps when both adapters were transmitting at full speed in each direction.

This is another argument for using the 5GHz band whenever possible if network performance is an issue. Neither Apple nor its competitors can control the increasingly heavy use of the lower-frequency band.

Gigabit Ethernet performance was as expected, achieving over 900 Mbps of throughput in one direction between two computers connected via the Base Station’s LAN and over 800 Mbps each way when simultaneously transmitting at full speed.

We discovered one disappointment that’s indirectly related to the new router model: We tested an Intel 802.11n adapter against the AirPort Extreme Base Station and found that compatibility issues limited the Intel device in 5GHz mode to 34 Mbps when transferring data at full speed to an Apple 802.11n adapter, and to just 50 Mbps when transferring data to a wired computer on the LAN.

The reason for this is that 802.11n isn’t complete; it’s a draft standard that is implemented differently by each company. Apple released a firmware update just before publication of this review that turns its AirPort Extreme Base Station with 802.11n into a certified Draft N device, with testing performed by the industry trade group The Wi-Fi Alliance, which controls the Wi-Fi name. At the time of our testing, Intel hadn’t released its certified update.

Although we didn’t test file-transfer speeds from volumes shared via USB in the previous review, reports indicated that the Gigabit Ethernet model had improved file transfer. In our testing of the earlier 10/100 Mbps model and the current Base Station, file-transfer speeds had improved by as much as 10 percent.

Apple also improved a problem that we brought to its attention in our last review. We experienced a slowdown in network speed when the Base Station was connected to a fast network via its wide area network (WAN) port — specifically, when it was also being used to distribute IP addresses to computers, phones, and other devices connected via Wi-Fi or through the LAN Ethernet ports. This distribution is called network address translation (NAT), and Apple confirmed at the time that firmware and hardware issues did limit the maximum speed between locally connected devices and the WAN. At that time, we reported that Wi-Fi devices couldn’t transfer data faster than about 30 Mbps to the WAN, and Ethernet-connected LAN computers maxed out at 60 Mbps. Well-planned office networks would turn off NAT and use a centrally located server to assign addresses (completely bypassing this problem). However, there are increasingly faster networks in homes as cable and fiber-optic networks spread. Those networks can reach speeds of 35 Mbps to 100 Mbps. Testing shows that the Gigabit Ethernet Base Station has substantially improved on this front. Wired LAN-to-WAN speeds now top 70 Mbps, and Wi-Fi-to-WAN speeds exceed 50 Mbps. While this is not as fast as we’d like to see, it should address most consumers’ concerns.

Buying advice
Apple has taken a seemingly minor upgrade of the AirPort Extreme Base Station and made it into a major improvement. Owners of the first model of the 802.11n Base Station who need speed may be slightly chagrined at how far Apple has boosted performance in just a few months. But the company has now set a high bar that it can improve on little with the current 802.11n and Ethernet standards underlying the Base Station’s networks.


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