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NSLU2 speed issues - hub vs. switch

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  • paulbart1234
    I brought this up in a previous post, and subsequent messages seem to confirm it: there may be an issue with half duplex ethernet on the NSLU2. If you
    Message 1 of 2 , Aug 15, 2004
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      I brought this up in a previous post, and subsequent messages seem
      to confirm it: there may be an issue with 'half duplex' ethernet on
      the NSLU2.

      If you connect something to a 'hub', it talks 'half duplex'. If you
      connect to a 'switch', it talks 'full duplex'.

      When you talk 'half duplex', the 'carrier detect' input on the
      IXP42x is used to determine whether/not someone else is 'talking' on
      the ethernet connection. This is used for collision detection.

      On the project I'm currently working on (also IXP420-based), we had
      a problem with the PHY, where 'carrier detect' wasn't working
      correctly. We ended up getting tons of collision errors when
      talking 'half duplex' (for example: when plugged-into a 'hub' (vs.
      a 'switch')). It was a hardware/software design problem, which
      we've since fixed.

      I have a feeling that the NSLU2 may have a similar problem - maybe
      the "ETH_CRS[0/1]" signal(s) on the IXP420 aren't properly connected
      to the corresponding signal on the PHY chip. I don't know exactly
      how to confirm this - other than (perhaps) looking at "ifconfig -a"
      output, and seeing how many errors are seen on a 'hub' vs.
      a 'switch'.

      I could be wrong on this, but since I've noticed serious speed
      issues on a 'hub' (half duplex) (which went away when I went to
      a 'switch' (full duplex)), and others seem to have seen similar
      issues, I thought I'd point this out.

      - Paulb
    • Christopher Zapf
      FWIW, here is my data when I am connected to a HUB (Netgear DS104) and only get around 3 Mbit/s speed: # ifconfig -a ixp0 Link encap:Ethernet HWaddr
      Message 2 of 2 , Aug 15, 2004
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        FWIW, here is my data when I am connected to a HUB
        (Netgear DS104) and only get around 3 Mbit/s speed:

        # ifconfig -a
        ixp0 Link encap:Ethernet HWaddr
        00:04:5A:0F:AC:A7
        inet addr:172.16.1.33 Bcast:172.16.255.255
        Mask:255.255.0.0
        UP BROADCAST RUNNING PROMISC MULTICAST
        MTU:1500 Metric:1
        RX packets:492001 errors:4099 dropped:0
        overruns:0 frame:1910
        TX packets:745751 errors:0 dropped:0
        overruns:0 carrier:0
        collisions:0 txqueuelen:256
        RX bytes:64022786 (61.0 MiB) TX
        bytes:403085975 (384.4 MiB)

        ixp1 Link encap:Ethernet HWaddr
        00:04:5A:0F:AC:A7
        BROADCAST MULTICAST MTU:1500 Metric:1
        RX packets:0 errors:0 dropped:0 overruns:0
        frame:0
        TX packets:0 errors:0 dropped:0 overruns:0
        carrier:0
        collisions:0 txqueuelen:256
        RX bytes:0 (0.0 iB) TX bytes:0 (0.0 iB)

        lo Link encap:Local Loopback
        inet addr:127.0.0.1 Mask:255.0.0.0
        UP LOOPBACK RUNNING MTU:16436 Metric:1
        RX packets:18 errors:0 dropped:0 overruns:0
        frame:0
        TX packets:18 errors:0 dropped:0 overruns:0
        carrier:0
        collisions:0 txqueuelen:0
        RX bytes:2281 (2.2 kiB) TX bytes:2281 (2.2
        kiB)


        --- paulbart1234 <paulbart@...> wrote:

        > I brought this up in a previous post, and subsequent
        > messages seem
        > to confirm it: there may be an issue with 'half
        > duplex' ethernet on
        > the NSLU2.
        >
        > If you connect something to a 'hub', it talks 'half
        > duplex'. If you
        > connect to a 'switch', it talks 'full duplex'.
        >
        > When you talk 'half duplex', the 'carrier detect'
        > input on the
        > IXP42x is used to determine whether/not someone else
        > is 'talking' on
        > the ethernet connection. This is used for collision
        > detection.
        >
        > On the project I'm currently working on (also
        > IXP420-based), we had
        > a problem with the PHY, where 'carrier detect'
        > wasn't working
        > correctly. We ended up getting tons of collision
        > errors when
        > talking 'half duplex' (for example: when
        > plugged-into a 'hub' (vs.
        > a 'switch')). It was a hardware/software design
        > problem, which
        > we've since fixed.
        >
        > I have a feeling that the NSLU2 may have a similar
        > problem - maybe
        > the "ETH_CRS[0/1]" signal(s) on the IXP420 aren't
        > properly connected
        > to the corresponding signal on the PHY chip. I
        > don't know exactly
        > how to confirm this - other than (perhaps) looking
        > at "ifconfig -a"
        > output, and seeing how many errors are seen on a
        > 'hub' vs.
        > a 'switch'.
        >
        > I could be wrong on this, but since I've noticed
        > serious speed
        > issues on a 'hub' (half duplex) (which went away
        > when I went to
        > a 'switch' (full duplex)), and others seem to have
        > seen similar
        > issues, I thought I'd point this out.
        >
        > - Paulb
        >
        >
        >




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