USB 1.1 Adapter Throughput?

  • Hey all,

    Last night I finally got my pfSense router set up. I'm using a laptop with an integrated NIC (LAN) and a NetGear FA101 10/100 USB 1.1 adapter (WAN). I have 7mbit service and used to be able to get very close to that on bandwidth tests. However, since installing the fpSense router my bandwidth has dropped to about 3.5mbit. Could this be the maximum throughput of the USB 1.1 adapter? I know the spec for USB 1.1 is 12mbit so I figured I wouldn't have any problems… Could there really be THAT much overhead?


  • well, keep in mind it will most likely negotiate only 10mb, and while 3.5mb out of 10mb is not great, it is not outrageous either, although it does seem low.  one thing to check: possibly it is NOT negotiating correctly, and there is a speed/duplex mismatch, which will screw your TCP thruput into the ground.

  • Actually its a 10/100 adapter (surprisingly) and the 100mbit light is lit up on it so I think that's what it has negotiating at.

  • While USB 1.1 may have a theoretical bandwidth of 12 Mb/s, that includes all the communications overheads.  In reality you'll rarely get more than 8 Mb/s through USB 1.1.  Importantly that's the total bandwidth, whereas your 7 Mb/s service is simply specifying the download portion.  How close you get to that 8 Mb/s depends on a long list of things, including:

    1. Quality of the USB device
    2. Quality of the USB chipset's support for USB 1.1
    3. Quality of the USB drivers

    At this point in time USB support in FreeBSD is still relatively young and immature - it's getting better but if you're using chipsets that the developers haven't, or a device that they haven't, then you'll have more problems.

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