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slowish network speed

Discussion in 'Networking Issues' started by vb7prog, Aug 16, 2005.

  1. vb7prog

    vb7prog Network Guru Member

    I have a small network which contains wired and wireless connections. On the network i have a file server running apache. When i download from the wired connection i see a rate of around 4000 KiloBytes per sec from the wireless i've seen rates as high as 2000 KiloBytes per second. These rates seem very slow compared to what the equipment is rated.

    100 Megabitps Switch = 4000(real output avg) / 12500(rate output max) 32% efficiency
    54 g wireless router = 2000(real output max) / 6750(rated output max) 29% efficiency

    is there a reason for this, i crimp my own wires could be a factor but i doubt it.

    another note is the wireless uses 256-bit AES encryption which purhaps would slow down the 54g but not that great.

    any thoughts how to speed stuff up or reasons why it might run slow? my wireless router is a WRT54G running DD-WRT's latest firmware
     
  2. howardp6

    howardp6 Network Guru Member

    How are you measuring throughput?

    A wired connection is capable of 200Mbs at full duplex, since a wired connection can send and receive at the same time. A wireless connection does not work at full duplex, since wireless routers cannot send and receive at the same time. A wireless 802.11g connection will give you typically about 22-24Mbs (small b = bits) or about 3MBs (big B = bytes). It depends on the size of the TCP rwin (receiving windows size) in Windows, which it set by the operating system in Windows XP, overhead (packets contain other information other than data and encryption), packet loss, the MTU and other factors such as firmware on the router, number of clients length of cables, sharp bends in cables, cable miswires and the efficiency of the switch and NICS. You can check for miswires with an Ethernet cable tester. Very short amd very long Ethernet cables are not good. You can measure throughput with measuring tools like IPERF. The TCP rwin can be increased in size by manually changing the registry (not recommended) or using tools like DRTCP and rebooting the computer. DRTCP can be obtained at WWW.DSLREPORTS.COM. The TCP rwin on my computer is about 128Kb and it is typically set by Windows XP at 32Kb. Are your wired devices operating at full duplex or half duplex? Your wireless connection should be at about 3MBs not 2MBs so your efficiency is about 66 percent of what is expected.
     
  3. vb7prog

    vb7prog Network Guru Member

    ok an update i ran iperf to test the speeds

    18.4 MegaBits per second on wireless (not bad)
    94.7 MegaBits per second on wired (not bad)

    the rates seen in iperf look pretty reasonable for overhead and stuff, before i was using either apache or ftp to transfer large non-compressable cd-sized files downloading using firefox

    I like real results ... and the benchmark is way off the real mark.

    ive change the tcp window on my machines to 128 KB that didn't affect the apache file transfers
     

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