Network speed discrepancy


Golden Member
Nov 12, 2002
I just discovered some odd behavior from my network, wondering if anyone can help figure it out. I'll spare the entire setup details, but essentially it's got a NAS connected via MoCA bridge, a desktop connected via Ethernet, and a bunch of laptops using 5GHz wireless (dropping to 2.4 at times when they have poor reception). Router is a D-Link DIR855L (a newish N900 router).

My issue seems to be when transferring data between the desktop and the NAS. I'm getting speeds of maybe 24Mbps in either direction when moving a 500MB test file. I can get at least double to triple that speed when reading/writing to any laptop on the network, from the desktop. Initially I thought it was just the MoCA bridge being a bottleneck.....

But today I realized I can go from any laptop to the NAS at 60+Mbps. Sometimes I nearly max out the 100Mbps connection to the NAS. So it can't be the MoCA bridge being slow, since that traffic takes the same path from the router to the NAS.

The weirdest thing: Using a laptop to grab a test file off my desktop PC and move it to the NAS, I get very good speeds. Using the desktop to move that *very same file* to the *very same NAS*, I'm stuck at 20-something Mbps. I don't get it.... the file is moving from point A (desktop PC) to point B (NAS) both times, so why such a drastic change in speed based on how I initiate the transfer? Any ideas?


Jun 13, 2000
Check duplex negotiation on the desktop and make sure you're on the latest nic drivers. Some switches don't handles negotiation well and you may have to set it to full duplex.

Other than that, look at protocol level things that may cause slowness. .