Tuesday, August 28, 2007

Apple TV: Using an AirPort Disk, Part 1

Apple TV plays iTunes media files — movies, songs, etc. — on an HDTV via a wireless home network. I first talked about my own new Apple TV in Apple TV is a Winner!. In Apple TV: Getting Content I showed how to use HandBrake and especially BitTorrent to get movies to play on it. In Apple TV: Adding Subtitles I talked about overlaying subtitles for the hearing-impaired (like me). Now in this post I would like to discuss my experiments with storing Apple TV movie files on an external USB 2.0 hard drive attached to an AirPort Extreme 802.11n base station.

The AirPort Extreme 802.11n base station is a fairly new product from Apple. It replaces the old AirPort Extreme base station that looks like a tiny spaceship and lacks support for the emerging 802.11n wireless standard. The old AirPort Extreme base station is limited to 802.11g, which is not as fast. For brevity, I'll refer to the new AirPort Extreme 802.11n base station as "Extreme-n," and to the old AirPort Extreme base station which lacks 802.11n support as "Extreme-g."

Extreme-n is the first Apple base station to which you can hook an external hard drive, one that has a USB 2.0 interface. The drive can then be mounted, server-like, on the desktop of every Mac on the network. (I'm talking about Mac networks here. Much of what I say can also be implemented on PCs running Windows an linked by non-Apple WiFi gear, but the details are different, and I have no personal experience with them.)

I just got a new Extreme-n. I already had an Extreme-g, used (among other things) to provide wireless network access to my Apple TV. On the wireless Extreme-g network were two Macs: a MacBook Pro with an Intel Core Duo (not a Core 2 Duo) processor, and an iMac. Also on the network were three AirPort Express base stations, which were being used to extend the range of the network and to stream AirTunes.

I also just got a Western Digital My Book™ Essential Edition 500GB external USB 2.0 hard drive. It comes with a USB cable that allows it to be attached directly to a Mac ... or to an Extreme-g.

My purpose in doing this was mainly so that I could have a lot of storage for movies. To that end, I could have USB-cabled the My Book directly to the MacBook Pro that I use to rip DVDs and download movie files. But that would have turned the portable MacBook into a glorified desktop machine, so I figured hanging the My Book off an Extreme-n would be a better choice.

My reasoning, as it turned out, was in one way a bit flawed. I thought the MacBook Pro was capable of 802.11n speeds and could talk to the Extreme-n in that superfast way. I had simply misread the information I'd located on the Web about which current Mac models can be 802.11n-enabled. Turns out that MacBook with a Core 2 Duo processor from Intel can; those like mine with just a Core Duo processor cannot.

But I hadn't twigged to that when I installed my Extreme-n with the 500GB My Book hooked to it.

The installation went surprisingly smoothly. Note that you need a Mac with Mac OS X v.10.4 or later for setup and administration of an Extreme-n. Though the Extreme-n can be used by Mac OS X v.10.2.7 or later — I was running 10.3.9 on my iMac — I decided to upgrade that machine to the same 10.4.10 that runs on my MacBook. That meant I could use the new setup and administration software that comes with the Extreme-n, which bears the name AirPort Utility. AirPort Utility is the all-in-one replacement for the old AirPort Setup Assistant and AirPort Admin Utility.

Since I was laboring under the misapprehension that I would be able to use swift 802.11n connections to stream movies from my MacBook to my Apple TV via the Extreme-n, I decided to set up the Extreme-n in tandem with my existing Extreme-g, creating what techies call a dual-band network. I would configure the new Extreme-n to utilize only the 5.0 GHz band, which 802.11n is capable of exploiting in its search for higher transmission speeds. Meanwhile, the Extreme-g would be responsible for handing the lowly 2.4 GHz band, wherein 802.11g transmissions take place.

To create a dual-band network using two paired base stations, you first need to decide which base station will connect to your broadband Internet source ... in my case, a cable modem. (Other possible choices include a DSL modem and a broadband Internet connection provided by a wired Ethernet network.)

I read Apple's Designing AirPort Extreme 802.11n Networks (I recommend you do, too) and came away with the impression that the Extreme-n generally ought to be made the Internet-connected one, with the Extreme-g a subsidiary to it. But that would have meant I would have had to fool with my existing Extreme-g's configuration, which I was loath to do. So I looked for alternatives.

After much head-scratching and several visits to this MacOSXHints forum thread, I realized that I could safely reverse the order of the two base stations. That would involve leaving in place the existing Ethernet cable running from my cable modem to the WAN port on my Extreme-g, while hooking a second Ethernet cable from the LAN port on the Extreme-g to a LAN port (there are three) on the Extreme-n. (In my experiments, I found I could just as well hook that second cable into the Extreme-n's WAN port! It didn't matter! My possibly incorrect understanding of this is that operating the Extreme-n as a "bridge," not a "router" — see below — turns the Extreme-n's WAN port into just another LAN port.)

Doing things in that way let me leave the configuration of my existing Extreme-g base station, and all my existing AirPort Express base stations, completely alone. All I had to do was configure the new Extreme-n as a "bridge" in AirPort Utility. This simply amounts to selecting "Off (Bridge Mode)" as its method of connection sharing, rather than "Share a public IP address."

Here are more details on that. When "Off (Bridge Mode)" is selected in the Manual Setup mode of AirPort Utility, the Extreme-n acts as a bridge between the Extreme-g and the other devices/computers on the network. Basically, what that means is that it doesn't touch the Internet addressing information — the so-called IP addresses — contained in packets it transmits on the network.

Meanwhile, the Extreme-g uses "Share a public IP address" as its connection-sharing mode — just as it always did before — which means it dynamically figures out what my Internet provider has assigned as my current IP address, and it maps all downstream devices' (my two computers, my AirPort Expresses, my Apple TV, etc.) IP addresses (which it has itself assigned to them) to that one master IP address. In this way, the Extreme-g acts as a "gateway."

Inserting the new Extreme-n logically "between" the gateway and the lesser network devices does nothing whatever to change that, as long as "Off (Bridge Mode)" is used for its connection sharing, making it a "bridge."

Though it is blind to Internet addressing, thee Extreme-n sets up its own "network," which is actually just one of two segments of the entire dual-band network. I named this new network/segment "N net," while the original Extreme-g continues to host a network (now also just a segment, actually) called "X net."

Thankfully, you don't really have to understand all this stuff about gateways, bridges, etc. to set up the Extreme-n the way I set mine up. This is because AirPort Utility defaults to an assisted setup mode, rather than manual setup (which you can select if you don't want to do an assisted setup). In assisted setup mode, when the proper time comes you simply specify that you want the Extreme-n to be used as a bridge.

My assumption (which turned out to be wrong and had to be corrected manually later) was that I also ought to set up the Extreme-n to use the 5.0 GHz frequency range of 802.11n exclusively, while the Extreme-g continued to use just the 2.4 GHz range associated with 802.11g. Had I realized from the get-go that my MacBook is not 802.11n-capable, I would instead have accepted the default option in assisted setup, the one which allows the Extreme-n to operate in both ranges.

So the actual process of hooking up and configuring an Extreme-n to act as a bridge to an existing Extreme-g's router turns out to be simple. Ignoring niggling details like installing the AirPort software from the CD that comes with the Extreme-n and then allowing Software Update to replace it with the most up-to-date version, it involves:

  • Setting up the new Extreme-n physically
  • Hooking an Ethernet cable from any Extreme-n LAN port (or even the WAN port!) to the LAN port on the existing Extreme-g
  • Setting up the external hard drive physically, plugging it in, and USB-cabling it to the Extreme-n
  • Powering up the Extreme-n
  • Running AirPort Utility in assisted mode to configure the Extreme-n
  • Designating all the parameters you typically need to designate when configuring any base station
  • Making sure you put the Extreme-n in bridge mode during the configuration process. Using assisted setup in AirPort utility, you select "Bridge mode" instead of "Share a single IP address using DHCP and NAT." Using manual setup, you click on the Internet icon and use the Connection Sharing popup menu to select "Off (Bridge mode)"
  • Optionally setting the Extreme-n during the configuration process not to use the 2.4 GHz band employed by 802.11g, provided you actually have computers and othe network devices that can take advantage of 802.11n and don't rely on 802.11g or 802.11b. When using assisted setup in AirPort Utility, you do this by selecting "802.11n (802.11a compatible)" as the Radio Mode, instead of "802.11n (802.11b/g compatible)." Better yet, use manual setup to select "802.11n only (5 GHz)," which avoids diluting transmission speeds by maintaining 802.11a compatibility
  • At the end of the configuration process, clicking Update

When you finally update the Extreme-n's config in this way, after it powers back up you will hopefully be rewarded (perhaps after all too many excruciating seconds of a slowly blinking amber status light) with a solid green light which says it has successfully established an Internet connection. That means you're good to go.

Note that the status light typically comes on solid amber at power up, then after a few seconds turns briefly green. Then the blinking amber status light takes over. Out of the box, since the Extreme-n doesn't yet know how you want it to connect to the Internet, the blinking amber light tends not to go away. But after the Extreme-n is successfully configured the way you want it, a solid green light becomes your eventual reward. (Also, there is a way in AirPort Utility's Manual Setup to change the solid green light of the Extreme-n to a green light that blinks when there is activity on the base station ... a good way for you to tell whether the Extreme-n or Extreme-g is doing the lion's share of the work.)

After I got the Extreme-n configured, it didn't take long for me to start gloating over the fact that each of my Macs could join either one of the two "networks" (actually segments of one dual-band network) I now had. That is, both "X net" (the original network) and "N net" showed up in the AirPort menu of each Mac, and whichever one I chose, from whichever Mac, worked fine.

At first, the My Book didn't just show up on my desktop, however. I had to open AirPort Disk Utility and check "Show AirPort Disks in the menu bar," at which time a new AirPort Disks menu popped onto my menu bar. It allowed me to select and mount the My Book. Also, checking "Automatically discover AirPort disks" makes them auto-mount, I found ... though you have to enter the password you assigned to the disk, earlier in AirPort Utility. (Alternatively, you can sign on to the disk as a "guest," with whatever privileges you gave guests in AirPort Utility.)

So. It turns out to be pretty easy to attach an Extreme-n as a bridge to an existing Extreme-g and its network, thus providing a second network — which is actually part of the original network, using a different network name. The second network, handled by the Extreme-n, can be just for swift 802.11n connections in the 5.0 GHz band, while all slower 802.11g connections are handled by the Extreme-g. This is what a dual-band network is all about.

In my arrangement, the Extreme-g became the Internet gateway. In Apple's literature, the Extreme-n is used as the gateway. Other than that, my arrangement started out being just the same as Apple recommends.

But that soon had to change, once I found out my MacBook Pro was not capable of being 802.11n-enabled, after all. More on that in Part 2 of this post ...


micah said...

By far the most thorough approach to EXACTLY what it is I'm trying to do. I'll try it this weekend.

I have a:

Time Capsule
Western Digital 500 gig Drive (Movies, Music)
Airport Express
Airport Extreme N
Airport Extreme G
Apple TV

Any suggestions as to how best approach your set up using my devices?

eric said...


Bad news ... after several months of using an AirPort disk attached to my AirPort Extreme-n base station, I got tired of fighting with it. Also, it turned out to be too slow a connection for my purposes.

Fighting with it: it kept getting its access locked out on my two Macs, such that I could not re-mount the AirPort disk until I went through a cumbersome procedure involving moving the MyBook temporarily to one of the Macs and then back to the base station, after removing power to the base station and then starting it up again. Updates to the base station software cured most of that problem, but it did not cure the problem in which the Mac backup software Time Machine (I was trying to use the AirPort disk for backups) would manage to mess up the MyBook and cause it to have to be reinitialized in Disk Utility.

Too slow: 802.11g speeds are just too slow for operations involving copying movie files, say from a Mac to the AirPort disk. I was using the AirPort disk for my iTunes library, with lots of movie files in it. Most of the time, such as when streaming a movie into an Apple TV across the network, the speed was fine. But for large-scale library maintenance operations, it was just too slow.

Time Machine backups were also excruciatingly slow.

What with the speed and reliability issues, I regretfully moved my AirPort disk to one of my Macs.

That said, if you run into problems this weekend with your installation, feel free to ask about them. I'll help you if I can.

micah said...

That's good feedback, Eric.

I may take you up on it this weekend, as I still want to try out the dual band concept- my wife has an old ibook g4, and I'd like to build her a separate 802.11b network entry point to see if that helps network throughput.

Thanks for the fantastic feedback!