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Not A Satisfying Victory August 29, 2006

Posted by gordonwatts in computers.
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The Mac-Windows wars are continuous. Especially in a mixed household. The Mac wins this one, but I’m not sure it is anything to be proud of…

The goal? Copy the 700 MB episode of a series that my wife and mother-in-law were missing from our server back in Seattle.

  1. Serve the file on the web, using Saffari on the Mac managed to copy down only the first 15 minutes or so before the conneciton broke (flakey wireless here in Ottawa!). Unfortunately, there was no warning message seen and the file size looked right — so while the first 15 minutes of the file played just fine…
  2. Managed to use a small utility I wrote some time ago to copy the file down to my PC. Now, needed to get it to the mac as her screen is larger than mine…
  3. Tried to use my USB Key… ops, it is only 512 MB. No go.
  4. Tried to use myGigabeat SS, with a 60 MB disk drive, but when I tried to copy it over it popped a dialog box: “This file is in a format that the Gigabeat S may not be able to play. Click “skip” to skip the file.” And the options I was given “Skip”, “Skip All”, and “Cancel”. Wankers. Nothing I could do to copy the thing over.
  5. My Windows machine knows nothing about the iPod, perhaps it will see it as a simple disk. Oh. Battery dead. And it is constructed so  you can’t both power the device and transer data (at least not the connectors Paula had with her).
  6. We have a wireless network. So I tried to expose the file from a web server on Windows. The web server wasn’t installed and requested the installation CD when I tried to install it. Of course, that CD is… well, I have no idea.
  7. Turned on file sharing and put it on a file share. The Mac, however, couldn’t find the share. But another windows computer in the house could. No idea what I did wrong on the Mac for this one.
  8. Contemplated installing FolderShare, one of my favorite utilities (why can’t they add a Linux version!!!), but decided that, at this point, that would be too much like giving up.
  9. Filesharing on the Mac was turned on, and I managed to see it from my Windows machine! I could then drag-and-drop the file from computer to computer. Whew.

Well, that was until I saw the datarate. Initial rates had it copying in 9 or 10 minutes. But then it quickly turned into 180 or so minutes. Looking at the networking monitor I could see a saw-tooth pattern in the datarate. The rate would steadily climb, and then suddenly drop. Using some net status utilities I discovered that the drops in data rate were correlated with retransmitted packets. In other words: when a packet is lost on the connection the algorithm assumes that the connection is flakely and only transmits a small amount of data. Since that data makes it through just fine, it sends a bit more, and so on and so on, slowly increasing in rate. Until another packet is lost. That algorithm is awful for this sort of network connection. After a lost packet it should come back at full speed; packet loss has nothing to do with data rate in this envorinoment; it is essentially random (noise and interference).

Upshot? The computers will copy the file over the next couple of hours. And they will watch the missing episode tomorrow.

Mac wins. But nothing to be proud of. What I should have done in the first place was use wget from the mac to download the file from Seattle. Then it would have been there, on the Mac, and no transfers would have been required (wget is resilient to network interruptions).

Comments»

1. agm - August 29, 2006

There is always the magic that is a cross-over cable, or patching both boxes into a hub or router…

2. Gordon Watts - August 29, 2006

Yes! And that would have made the transfer go a lot faster… if only we had those cables here….🙂


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