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Tomato Devs and experts - Why is Samba slow over wireless?

Discussion in 'Tomato Firmware' started by spliff, Oct 4, 2008.

  1. spliff

    spliff LI Guru Member

    I tested two ASUS WL-520GU's that have this problem. Wireless is very fast but Samba transfers are slower than other types of traffic. I have a Linux NAS server that is very fast over wired (60 megabytes/sec read sustained) but over a wireless link the transfers are slow and unreliable.

    Here is a picture that demonstrates what I am seeing.


    The first transfer on the left is a samba file transfer from my server to my Laptop using my Tomato access point. It is configured as an AP, all settings are default. Security is turned off. The second transfer (much faster and consistent) is when I downloaded the same file over http (apache) from the same server. I checked the CPU for both and it was well under 100%. Its not a chipset issue because I have the same problem when I use a Cisco CB21AG (A/B/G cardbus adapter) or the other ASUS WL-520GU as an ethernet bridge.

    Why is Samba so slow over Tomato? I tested Samba transfers using a Cisco 1200AP that I have at home and it is a solid transfer, no ups and downs like when using Tomato.
  2. spliff

    spliff LI Guru Member

    I think I found the solution! :rockon:

    I lowered the "Fragmentation Threshold" to 1500 and low and behold Samba is fast and smooth now. If I set the value to 1600 Samba is slow and choppy. Somewhere between 1500 and 1600 is the correct value. Makes me think that this should be not to much higher than the MTU of the wireless interface.

    Set to 1500

    Seth to 1600

    Can anyone else confirm this with another router model? Also, can someone post more information on this setting and what it does? Why is the default set higher than the MTU of the wireless interface? Why does it only affect Samba? I wonder if the Tomato default should be changed.

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