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UPDATE: When I connected via an Ethernet cable directly running from my Linux laptop to my wireless router, I get the correct bandwdith (~10 Mbits/s). It's only when I connect wirelessly that my bandwidth is so small as described below.


I have two laptops with roughly the same specs. One is running Windows 7, the other is running Ubuntu 12.04. When I run a speed test at http://testmy.net, the Linux laptop pulls approximately 1 Mbits/s, whereas the Windows laptop pulls approximately 10 Mbits/s. Running speed test on other speed-test providers yields similar differences in downstream bandwidth between the two laptops: the Linux laptop is consistently much slower.

Trying to exercise due diligence, I also tested the Linux laptop's bandwidth using iperf. The iperf server is on a Linux desktop computer (which I use exclusively) in my office at a major university in the UNC system. To run the server, I entered the command

# iperf -s -p 9090 -w 1024k -l 100k

and, on my Linux laptop at home (behind an AT&T U-Verse router), I ran the iperf client (test) by entering the command

$ iperf -i 2 -p 9090 -c XX.XX.XX.XX -t 50 -w 1024k -l 100k

The output from the test was

------------------------------------------------------------
Client connecting to XX.XX.XX.XX, TCP port 9090
TCP window size:  256 KByte (WARNING: requested 1.00 MByte)
------------------------------------------------------------
[  3] local 192.168.1.69 port 43880 connected with XX.XX.XX.XX port 9090
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0- 2.0 sec   400 KBytes  1.64 Mbits/sec
[  3]  2.0- 4.0 sec   400 KBytes  1.64 Mbits/sec
[  3]  4.0- 6.0 sec   300 KBytes  1.23 Mbits/sec
[  3]  6.0- 8.0 sec   300 KBytes  1.23 Mbits/sec
[  3]  8.0-10.0 sec   300 KBytes  1.23 Mbits/sec
[  3] 10.0-12.0 sec   400 KBytes  1.64 Mbits/sec
[  3] 12.0-14.0 sec   300 KBytes  1.23 Mbits/sec
[  3] 14.0-16.0 sec   400 KBytes  1.64 Mbits/sec
[  3] 16.0-18.0 sec   300 KBytes  1.23 Mbits/sec
[  3] 18.0-20.0 sec   300 KBytes  1.23 Mbits/sec
[  3] 20.0-22.0 sec   400 KBytes  1.64 Mbits/sec
[  3] 22.0-24.0 sec   300 KBytes  1.23 Mbits/sec
[  3] 24.0-26.0 sec   400 KBytes  1.64 Mbits/sec
[  3] 26.0-28.0 sec   300 KBytes  1.23 Mbits/sec
[  3] 28.0-30.0 sec   400 KBytes  1.64 Mbits/sec
[  3] 30.0-32.0 sec   300 KBytes  1.23 Mbits/sec
[  3] 32.0-34.0 sec   300 KBytes  1.23 Mbits/sec
[  3] 34.0-36.0 sec   200 KBytes   819 Kbits/sec
[  3] 36.0-38.0 sec   200 KBytes   819 Kbits/sec
[  3] 38.0-40.0 sec   200 KBytes   819 Kbits/sec
[  3] 40.0-42.0 sec   400 KBytes  1.64 Mbits/sec
[  3] 42.0-44.0 sec   400 KBytes  1.64 Mbits/sec
[  3] 44.0-46.0 sec   200 KBytes   819 Kbits/sec
[  3] 46.0-48.0 sec   300 KBytes  1.23 Mbits/sec
[  3] 48.0-50.0 sec   200 KBytes   819 Kbits/sec
[  3]  0.0-50.9 sec  7.81 MBytes  1.29 Mbits/sec

Thus, my iperf test shows that my Linux laptop is pulling much more slowly than my Windows laptop (which is pulling precisely the rate promised by my ISP for the plan I have).

Additionally, I set up a lighttpd web server on the same university Linux computer and attempted to download a several-gigabyte file using the following command:

$ aria2c -x 16 -s 20 http://XX.XX.XX.XX/testfile.tar

Using 8 concurrent connections --- I don't know why just 8, but I doubt that's relevant to this problem --- aria2c was able to download at approximately 1 Mbit/s also.

How can I investigate why my Linux laptop is downloading so slowly?

I'm not sure if this is relevant, but sometimes my Linux laptop when connecting to the wireless network will use device eth1, and other times it will use device eth2. This doesn't make sense to me because there's only 1 wireless device (I assume) on my laptop; it's a standard Dell laptop.

[Below are details on some of the hardware in my Linux laptop.]

Wireless interface:

        description: Wireless interface
        product: BCM4312 802.11b/g LP-PHY
        vendor: Broadcom Corporation
        physical id: 0
        bus info: pci@0000:0c:00.0
        logical name: eth2
        version: 01
        serial: 00:25:56:b2:16:3e
        width: 64 bits
        clock: 33MHz
        capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
        configuration: broadcast=yes driver=wl0 driverversion=6.20.155.1 (r326264) ip=192.168.1.69 latency=0 multicast=yes wireless=IEEE 802.11abg
        resources: irq:17 memory:f1ffc000-f1ffffff

System:

description: Portable Computer
    product: Latitude E6500 ()
    vendor: Winbond Electronics
    serial: obe
    width: 64 bits
    capabilities: smbios-2.4 dmi-2.4 vsyscall32
    configuration: boot=normal chassis=portable uuid=44454C4C-0000-1000-8000-80C04F6F6265
  *-core
       description: Motherboard
       vendor: Winbond Electronics
       physical id: 0
       serial: .obe    .              .
     *-firmware
          description: BIOS
          vendor: Winbond Electronics
          physical id: 0
          version: A24
          date: 08/19/2010
          size: 64KiB
          capacity: 1664KiB
          capabilities: isa pci pcmcia pnp upgrade shadowing cdboot bootselect int13floppy720 int5printscreen int9keyboard int14serial int17printer int10video acpi usb agp smartbattery biosbootspecification netboot
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migrated from stackoverflow.com May 8 '13 at 12:33

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Odd, I thought the wireless nic's are recognised as wl0. Anyway, that's my machine –  Matt H May 9 '13 at 0:20
    
I thought so too. They were under my previous laptop (from linuxcertified.com, not from Dell) running Ubuntu 11.10. Like I said, sometimes it's eth1, and sometimes it's eth2. That, alone, doesn't make sense to me. –  synaptik May 9 '13 at 0:29
    
The only idea I can think of is to ensure it's connecting via 802.11g and not b. If you can force your WiFi to only support g that might help isolate. –  Pecos Bill Mar 22 at 1:47

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