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Go Back and Forth Fast in Preview

If you're reading a PDF in Apple's Preview software, and you follow a bookmark or an internal link to move around within the PDF, you can quickly return to where you were by pressing the keyboard shortcut Command-[ (that's Command-Left Bracket). Or, you can choose Go > Back.

The command works iteratively, so you can go back to just the previously viewed page or if you issue the command again, to the page before that, and so on. There's also an equivalent Go > Forward (Command-]).

 
 

AirPort Base Station Upgraded to Gigabit Ethernet

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In the midst of other announcements last week, Apple quietly released an upgraded AirPort Extreme Base Station with 802.11n featuring gigabit Ethernet (1000 Mbps) on all four wired ports. While the company didn't release information separately, they contacted me to note the change, and the Apple Store's product listing has been updated. The new base station can be ordered now.

The AirPort Extreme with N had a lot of wonderful features, hard to find elsewhere, in its initial release in February 2007, including a USB port for adding and sharing printers and hard drives. (There are a lot of small problems with the way in which sharing is enabled and managed, however, which I document thoroughly in "Take Control of Your 802.11n AirPort Extreme Network." They may be fixed in this new version.)

Apple also chose to include both 2.4 GHz and 5 GHz radios, putting the AirPort in a rather special class in which either chunk of spectrum could be used. 5 GHz is relatively unoccupied and has a greater span of available frequency, making it ideal for new installations. Most Core 2 Duo Macs (the now-discontinued 17-inch iMac being one exception) also had 802.11n with both radios built in, enabled through a $1.99 Apple Store software purchase or found on the AirPort Extreme with N installation disc.

My primary complaint with the first release of the base station was the lack of gigabit Ethernet, which was especially pronounced given Apple's widespread early inclusion of the fastest common Ethernet flavor in its computers, starting with Power Mac models in 2000. Apple was way ahead of competing computer makers in this regard. And a few other network equipment makers had already released gigabit Ethernet 802.11n routers when Apple's Draft N entry appeared in February, making it an even stranger decision to trail competitors.

I also suspected that the overall performance of the 802.11n draft specification that Apple is using was constricted due to internal Ethernet limits. In my testing for a review in Macworld, I was able to top 90 Mbps in Wi-Fi to Ethernet and Wi-Fi to Wi-Fi transfers, where one computer was transmitting full bore to another. However, I achieved 50 Mbps in each direction (100 Mbps aggregated) when two computers were attempting to send to each other at full speed over Wi-Fi. That 100 Mbps aggregate was closer to the full speed of 802.11n, but the internal networking of the base station was still throttling the bandwidth.

Apple says that their new gigabit Ethernet base station is up to 50 percent faster for wireless-to-wired links, which would put it closer to 150 Mbps, a speed achieved on the few gigabit Ethernet-based Draft N routers from other manufacturers. Apple didn't state numbers for wireless-to-wireless links, which I can understand, because those links can be more variable, and other constraints may apply. I can't wait to test the revised model to see if intra-Wi-Fi links can hit nearly 150 Mbps, too.

When testing the previous version of the base station in February, I discovered that with NAT (Network Address Translation) enabled to share access from an incoming broadband link, performance was restricted to about 30 Mbps from a wireless connection to the broadband side, and 60 Mbps from a wired local connection to the broadband side. Apple confirmed this was a bug that was due to performance issues in their NAT software. Apple wasn't able to tell me if this limitation has been fixed in the latest model, but I am hoping so.

This bug emerges in only two edge cases: where a broadband connection exceeds 30 Mbps, which is true for some fiber and cable customers; or where a corporate or office LAN isn't supplying addresses to the computers connected via the AirPort Extreme. If NAT is turned off, the AirPort gateway has no performance limitations.

The price for the AirPort Extreme Base Station with 802.11n remains $179.

 

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