0

If a copy a file from my desktop to my laptop, the speed is usually 3 or 4 times faster than if I go in the other direction.

Desktop is connected to the router by a cable, laptop is wifi.

If I connect the laptop with a cable, speeds are fast both directions.

Router is a wrt54gl with dd-wrt. Both machines running Win7

Why would this happen? How can I identify the problem and fix it?

Improve this question
12
  • How do you copy it? SMB? SCP? Does one side have a much larger/faster random pool? Do the speeds change when you use wired connections for both (if not then you know it has nothing to do with Wireless). Etc etc.
    – Hennes
    Jul 21, 2013 at 15:37
  • Windows machines at both ends, so using various windows utilities. How should I test speed? What's a random pool? Wired on both sides is MUCH faster.
    – foosion
    Jul 21, 2013 at 15:45
  • 1
    You might want to edit your question... for as it stands, you say " from my desktop to my desktop" but further on in the question, you say "Desktop is connected to the router by a cable, laptop is wifi." Which is it? Are you talking about two desktops, or one desktop and one laptop? Also, are both computers running the same Operating System? If it is indeed a laptop, have you tried connecting it to your router with a network cable, and checking the transfer speed that way?
    – Bon Gart
    Jul 21, 2013 at 15:50
  • SCP and other encrypted links need random information for their encryption. Both on Windows and other operating systems this can exhaust the available supply of random numbers and thus slow down. (No idea if SMB/samba uses random, but I know sFTP and SCP do). -- As to wired is much faster. Aye. Generally I expect 100mbit wired to outperform 300mbit wireless.
    – Hennes
    Jul 21, 2013 at 15:50
  • @Hennes: Neither protocol requires a lot of cryptographically secure randomness. At most, SSH and SSL need only a few hundred bits – for things like creating a static session key that's used for the entire communication. (This applies to SFTP and SCP which use SSH as a transport.) SMB doesn't even need that; it lacks encryption.
    – u1686_grawity
    Jul 21, 2013 at 15:53

3 Answers 3

Reset to default
1

I can say this. Your problem isn't isolated to your situation. Apparently people have been posting about this very same issue for a few years now.... IE slow network transfers in one direction only across wireless.

What I'm finding, is that there appear to be different solutions, and that most appear to be specific to the hardware. For example, from smallbuilder.com...

So, after trying a few things, I set "Enable HW Accelerator" to Off under LAN - Switch Control and now I get 1.5MB/s in both directions!

This previous SU question resulted in a working solution for someone OTHER than the person who posted the question...

I went to the configuration screen of my network adapter and changed the following configuration settings:

  • Large Send Offload V2 (IPv4) = Disabled (was Enabled)
  • Large Send Offload V2 (IPv6) = Disabled (was Enabled)

A solution from a Microsoft Technet post, but no news on whether it was successful...

Try disabling Receive Window Auto-Tuning:

  • 1) Go to Start and type cmd.

  • 2) Right-click on cmd and select “Run as administrator”.

  • 3) Type: netsh interface tcp set global autotuninglevel=disabled and press Enter.

If you want to to re-enable it:

Type: netsh interface tcp set global autotuninglevel=normal and press Enter.

Also you can try configure the network card :

  • 1) Click the Start Button, type "devmgmt.msc" (without quotation marks) in the Start Search box and press Enter.

  • 2) Double click to expand "Network Adaptors".

  • 3) Right click your network card and click Properties

  • 4) Click Advance tab. High light Speed & Duplex

  • 5) If you would like to use the full functionality, please set the Value to the highest Full.

  • 6) Click OK.

There were also some smaller posts where people fixed their issues after finding that settings in their routers or network adapters had not been set to Full Duplex... that changing from an AUTO setting to a specific Full Duplex setting resulted in equal (and faster) network transfer speeds.

Sorry I don't have one specific answer to the issue... there just doesn't seem to be a single fix.

Improve this answer
8
  • Changing the desktop ethernet adapter to full duplex (from auto) helped with write to desktop speed when the notebook was close to the router, but not otherwise. Changing the router ports to full duplex (from auto) improved write to desktop speed a little, but there's still a large spread. Large send offload made no difference. Netsh resulted in an error message. I don't have Enable HW acceleration.
    – foosion
    Jul 21, 2013 at 20:16
  • What speed does your laptop say it is connected at? What kind of wireless security are you using? Does the problem persist if you disable that security?
    – Bon Gart
    Jul 22, 2013 at 2:07
  • Connection speed varies. 54Mbs is the most common, but it can go as low as 5.5. It appears to be more variable and to go lower while testing upload/download speeds and shortly afterwards. Even with connection speed bouncing around, read (download) is much faster than write (upload). Download was 11-12Mbs in most recent test, while upload was 2.5-6.0 (tested using a program which writes and reads a 20Mb file). Security is WPA2 personal - AES. Disabling doesn't help.
    – foosion
    Jul 22, 2013 at 10:04
  • BTW, on wifi, I can read from the internet (per speedtest.net) slightly faster than I can read from the desktop on my LAN.
    – foosion
    Jul 22, 2013 at 10:30
  • The connection speed between the laptop and the router should be more constant... it shouldn't bounce up and down like that. Granted, if you never saw very fast connection speeds to the router at all, it would bounce... but that's usually when a 54g card can't seem to connect faster than 10-15 max... but if you can hit 54, and that's the max for the WNIC, it shouldn't bounce unless there's an issue with the antenna, or material between the laptop and the router, or interference on the channel (change the channel you are using) like a 2.4ghz cordless phone or a nearby microwave oven etc
    – Bon Gart
    Jul 22, 2013 at 13:39
0

Your WiFi connection simply does not have the bandwidth of the wired connection, even at a 10/100 ethernet port. More modern routers offer faster wireless connections than the WRT54G, plus gigabit ethernet. See: http://community.linksys.com/t5/Wireless-Routers/WRT54GL-Is-wireless-faster-than-20Mbps-possible/m-p/517359?comm_cc=HSus&comm_lang=en#M227951

Improve this answer
1
  • 1
    That does not explain why it's faster in one direction than the other. In both cases it's using wifi for the laptop - router connection.
    – foosion
    Jul 21, 2013 at 15:43
0

This is part of the nature of the way access points work. Access point to client transmissions will always be more efficient than client to access point transmissions.

A Wifi network wouldn't work unless every node could reach the access point. Thus the access point can transmit very reliably, because it is guaranteed to hear all other nodes. However, client nodes frequently can't hear each other reliably. So it's much more likely for the laptop to have its transmissions stepped on, and thus need to repeat them. This greatly reduces the available bandwidth from the client to the access point.

Improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .