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.

On Apr 16, 2005, at 7:08 PM, Jim wrote:

> Is there a way I can get more?
>
> Thanks
>
> Jim
>
> Kevin Brown wrote:
>> If you mean that you can push 33Mb/s with this config, well, don't 
>> expect it to get much higher.  Even running full duplex you might not 
>> get much higher than that in general.
>>> The windows and linux boxes are connected via a crossover cable.  
>>> Both are configured for 100MBPS full duplex.
>
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