 | | | RE: hw tcp v4 csum failed?? Wha!?!?! | RE: hw tcp v4 csum failed?? Wha!?!?! 2005-01-21 - By Daniel Wittenberg
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Agreed, I completely understand how it works. I just didn't agree with
your statement that "it has to be Full Duplex if it's 100Mbs switch".
Dan
On Fri, 2005-01-21 at 14:29 -0500, Jay Lee wrote:
> Daniel Wittenberg said:
> > I don't think this is the case, I have seen *many* cisco switches (and
> > other gear too) that use 10/Half and they are switches that handle
> > 10/100/1000 speeds. I don't think duplex and speed go together unless
> > you are talking gigabit.
>
> Duplex simply means can the NIC send while it's receiving on the network.
> Half duplex means the NIC must be either sending or recieivng not both at
> once. Full duplex means that the NIC can both send and recieve at the
> same time. A hub has no buffers so only one node can be sending packets
> at a time, if two nodes try to send packets at once you get a collision
> and the packet must be resent by both. Naturally, if two seperate nodes
> on a hub can't send at the same time, then a single NIC cannot send and
> recieve packets at the same time, thus the half duplex setting. A switch
> has buffers which prevent such collisions allowing multiple nodes to send
> at once and a single NIC to both send and recieve at the same time, full
> duplex. The speed at which the NIC is sending does not matter (as long as
> it's not above the speed of the switch) since the switch can buffer the
> packets. So a 10/100 switch should have no problem handling a 10/full
> duplex connection. Of course, this is all theory and when it comes to
> bare hardware theory can often be tossed out the window, voodoo networking
> sometimes works better :) But the error message he is recieving leads me
> to suspect the NIC, not the switch.
>
> Jay
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