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    VPC-Z1 and jumbo frames

    Discussion in 'VAIO / Sony' started by abirkill, Mar 26, 2011.

  1. abirkill

    abirkill Notebook Enthusiast

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    Just spent an amusingly frustrating half-hour trying to get jumbo frame support working on my Z1, so thought I'd save others from going through the same process!

    Firstly, the Intel 82577LC adaptor in the Vaio Z does support jumbo frames, as confirmed on the Intel site:

    Intel® 82577LC Gigabit Ethernet PHY

    According to Intel, on Windows 7 it should simply be a case of going to Device Manager, finding the Intel Gigabit card, going to the advanced tab, and enabling jumbo frame support. However, if your setup is like mine, then there is absolutely no mention of jumbo frames either here or in the performance subsection.

    I upgraded my Intel drivers to the latest version, 16.1, but this also did not give a jumbo frame option that I could find.

    After searching online I found some instructions on how to enable jumbo frame support in Windows, by adding the following registry key:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\<interface>
    Edit->New, DWORD Value, MTU
    Edit->Modify, 9018

    However, this made no difference to me -- any attempt to send a packet over 1500 bytes caused it to be fragmented.

    Further searching online finally found this page with instructions on enabling jumbo frame support on the Intel card in a different location in the registry:

    Jumbo Frames on Hyper-V Server TechNuggets

    Following the instructions here and cycling the network adaptor down and up again caused some progress to be made -- the ping -f -l 2000 <ip> command finally didn't complain that it would have to fragment the packet. However, it instead simply didn't respond to the ping at all.

    Those familiar with jumbo frame support will know that this almost always means that there is a device in the network chain that doesn't support jumbo frames. Having used jumbo frames with other PCs over my network, I could narrow this down to a new gigabit switch I'd recently installed -- or so I thought!

    Unfortunately bypassing this switch had no effect whatsoever. After pondering this for a few minutes, a slow sinking sensation set in. I undocked my Vaio Z from the Sony dock, and plugged my network cable directly into network port on the side of the laptop -- hey presto, jumbo frame support working!

    So we can add another frustration to the list of frustrations with the Vaio Z dock -- as well as not having audio outputs, the gigabit hub that is built into it doesn't support jumbo frames.

    This is especially annoying for two reasons -- firstly, the dock prohibits (by means of a plastic peg) connecting the network cable directly to the laptop, and secondly, the two port hub built into the dock seems to me to be totally pointless anyway (has anyone actually found it useful, or would a single network connection be just as good?)

    Anyway, hopefully this may save someone a bit of time!
     
    abirkill, Mar 26, 2011
    #1