Puzzled by bandwidth tests

[GusSmed]

I'm setting up for streaming video, and I'm trying to get a handle on the bandwidth requirements. As part of that, I was trying to test my current bandwidth 802.11g bandwidth in various parts of the house.

WirelessMon reports 54 mbits / sec everywhere, even in the basement where it reports low signal strength. I was having trouble believing that, so I transferred a 86 MB file at various locations as a test.

Sustained transfer rate over the wireless network varied from about 14 mbps to 9.5 mbps, depending on location. WirelessMon claimed it was 10 mbps no matter what my stopwatch said. 14 mbps seemed kind of slow, but I didn't get any faster than that even when adjacent to the router.

Next I tried a direct wired connection. I only got about 25 mbps. That doesn't seem right. It's certainly not a limitation of the gigabit LAN - when I transferred a 1.5 GB file from my desktop to my Synology Diskstation, I got a rate of 250 mbps. Maybe not quite as fast as I might expect, but certainly a lot faster than what the laptop got.

The laptop NIC claims to be a gigabit card, yet its actual performance is a good deal less.

What am I not understanding?

- Gus

 

[boomhower]

Are you sure your doing the math right and not getting your B/b mixed up?

 

[spidey07]

That's normal for wireless. It's slow. At best with 802.11g you'll get 22 Mbs in a perfect environment. 15 or less is the norm in actual throughput.

Also laptop hard drives aren't particularly fast so that's probably holding you back on that one.

 

[klocwerk]

waaaay too many variables in there including NICs, media, disks, etc etc.

Regarding the old bits/bytes confusion: in a nutshell gigabit == 1000 megabits per second == 125 megabytes per second (mbps/8) as a theoretical maximum. Actual rates will be markedly lower due to transfer and protocol overhead, processing, etc.
Not sure if you're getting caught up on that, but worth repeating here.

Wirelessmon is calling anything running 802.11g a 54mbps connection regardless of your actual connection speed. Don't believe it. 😉

 

[GusSmed]

I've always assumed about a 10:1 difference in bytes vs. bits due to handshaking overhead, even though there are only 8 bits per byte. That's probably an overestimate these days, it's a habit left over from the days when modem transfer protocols had start and stop bits for every byte. The numbers I reported were bits per second based on the 10:1 assumption.

Actual transfer times were about 60-100 seconds for a 86 MB file over the wireless network, and 33 seconds via the direct Ethernet connection. I find the very slow results over wired Ethernet disturbing, the rest of the machines don't seem to have this problem.

The laptop drive being a bottleneck occurred to me, so I did a local copy of the same file (not a move, I know that typically just adjusts directory entries). Took 3 seconds, so no, it's not the laptop's hard drive.

I did a quick check with my wife's netbook, and got a 30 second transfer time over the wireless network.

I don't suppose there's a utility that will report real connection speeds without the clumsy process of transferring a file and timing it by hand?

- Gus