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Re: Ethernet performance.



On Apr 17, R. Chris Ross wrote
> 
>      I am quite new at the world of IP networks and have been doing 
> some testing on a Debian 1.2 system and Free BSD.  Last night I ran a 
> test as described in one of the ethernet FAQs by running FTP on a 
> file that was ~2.5Meg the rate came out at 1.09M/sec.  From what I 
> can tell this is quite good for 10 Base2 since this indicates a rate 
> around 8Mbit/sec of data not including overhead.  With no tuning at 
> all it is supprising to get proformance on this order or am I faking 
> my self out?

 
 The numbers above do not look right:

 The theoretical throughput on 10base2 is about 1.183 Mbytes/sec. This
 number assumes some rather ideal conditions: one ACK for 22 large 1460
 byte segments, no collisions, the minimun inter-packet gap of 9.6 ms, 64k
 windows, and no delays for either sender or receiver transitions (that is
 no TCP/IP delays). 

 throughput = (22*1460bytes)/(22*1538+84bytes) * 
              (10,000 bits/sec)/(8bits/sec) =
            = 1,183,667 bytes/sec
 


-- 
Ioannis Tambouras 
ioannis@flinet.com, West Palm Beach, Florida
Signed pgp-key on key server. 


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