Thank you for the information.  One of these days I'll get ambitious and 
buy a couple of gigabit cards.

Kurt Granroth wrote:
> Not much more, in any case.  The general rule of thumb for a 100Mbps 
> network is 40% efficiency.
> 
> My knowledge of this is sporadic, rusty, and incomplete... but here goes:
> 
> 100BaseT dictates that each 8 bit byte is encoded in a 10 bit packet.  
> Therefore, the theoretical max throughput of raw bits would be about 
> 76Mbps (megabit would be 1024x1204, not 1000x1000 when talking about data).
> 
> Nobody pushes raw bits over the network, though.  We use Ethernet on one 
> layer and then IP and then TCP or UDP.  All of these layers have their 
> overhead.  Let's take TCP/IP over Ethernet.  A maximum Ethernet packet 
> is 1514 bytes.  Of that, 54 or 66 bytes (depending on data type) are 
> taken by the Ethernet, IP, and TCP headers.  That's about 4%.  But then, 
> TCP requires an ACK packet for each and every data packet.  That means 
> that the headers actually take up about 8% of the space.  Subtracting 
> that from our theoretical max shows that the TCP/IP over Ethernet has a 
> theoretical max of 70Mbps.
> 
> Remember, though, that up to now, we are talking about theoretical 
> maximums.  The real world is quite a bit more variable.  Here's where my 
> knowledge gets increasingly iffy.  Take each statement from this point 
> on with a big grain of salt.
> 
> Okay, so the theoretical max is 70Mbps but that assumes that each packet 
> is maxed out with data.  If we go to a worst case scenario where each 
> data packet only contains 1 byte, then the actual throughput would be 
> less than 1Mbps.  Say the packets are each (on average) half full.  
> Then, our actual throughput would be under 60Mbps.
> 
> Beyond this, I admit that it gets into voodoo territory.  I know there 
> are a lot of other factors (like packet switching, collisions, etc) that 
> work to drive the actual throughput lower and lower but I don't know 
> enough about those factors to really comment.
> 
> The end result, though, is that 40% is the highest you can reasonably 
> expect.  So 33Mbps is getting pretty close.  Maybe you could eek another 
> 4 or 5Mbps out of that that with some careful tweaking... but that's 
> going to be it.
> 

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