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At first sorry for my english, I hope you will understand me.

I have a Ubuntu 11.04 box. There is a cable modem (motorola sbg900) plugged in via USB. My bandwidth should be 8mbit download and 0,7mbit upload. Some time ago everything worked just fine, but for last couple of weeks I couldnt download faster than 400-450kB/s. Today I took a closer look at this and it seems that USB connection is the problem. I tried connecting to the modem via RJ45, and max download speed was 8mbit (good). I went back to USB and nothing more than 400-450kB/s (so 4mbits).

I have no idea whats wrong. I cant use RJ45 - I have to use USB connection to the cable modem.

Please help..

$ uname -a
Linux NAS 2.6.38-10-generic #46-Ubuntu SMP Tue Jun 28 15:05:41 UTC 2011 i686 i686 i386 GNU/Linux

$ sudo lsusb -v -s 004:004

Bus 004 Device 004: ID 07b2:0900 Motorola BCS, Inc. SURFboard Gateway
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               1.10
  bDeviceClass            2 Communications
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0        32
  idVendor           0x07b2 Motorola BCS, Inc.
  idProduct          0x0900 SURFboard Gateway
  bcdDevice            1.01
  iManufacturer           1 Motorola Corporation
  iProduct                2 USB Cable Modem
  iSerial                 3 XXXXXXXXXXXX
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength           80
    bNumInterfaces          2
    bConfigurationValue     1
    iConfiguration          4 USB Ethernet Configuration
    bmAttributes         0xc0
      Self Powered
    MaxPower              100mA
    ** UNRECOGNIZED:  05 24 00 10 01
    ** UNRECOGNIZED:  05 24 06 00 01
    ** UNRECOGNIZED:  0d 24 0f 03 00 00 00 00 ea 05 00 00 00
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           1
      bInterfaceClass         2 Communications
      bInterfaceSubClass      6 Ethernet Networking
      bInterfaceProtocol      0 
      iInterface              5 Communication Interface Class
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x85  EP 5 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0008  1x 8 bytes
        bInterval              64
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass        10 CDC Data
      bInterfaceSubClass      0 Unused
      bInterfaceProtocol      0 
      iInterface              6 Data Interface Class
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       1
      bNumEndpoints           2
      bInterfaceClass        10 CDC Data
      bInterfaceSubClass      0 Unused
      bInterfaceProtocol      0 
      iInterface              6 Data Interface Class
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x02  EP 2 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
Device Status:     0x0001
  Self Powered
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migrated from serverfault.com Apr 16 '12 at 22:08

This question came from our site for professional system and network administrators.

1  
How are you testing your speed? Is perhaps your ISP over-subscribing their uplink? Are you testing against some remote system that cannot handle more then 450KB/s? –  Zoredache Apr 16 '12 at 22:09
    
I tested it on torrents, on speedtest.net and FTP (my ISP's server, so its like "local"). Im 100% sure that is not the remote servers problem, ISP problem etc. Its USB connection problem for sure. –  gibson Apr 16 '12 at 22:22
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