 | | | RE: hw tcp v4 csum failed?? Wha!?!?! | RE: hw tcp v4 csum failed?? Wha!?!?! 2005-01-21 - By Jay Lee
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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
--
Jay Lee
Network / Systems Administrator
Information Technology Dept.
Philadelphia Biblical University
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