Ethernet Card Limitations to Number of Connections?

[Chuck Swiger]

On Jun 13, 2007, at 10:14 AM, Michael K. Smith - Adhost wrote:
> Are there any physical limitations to the number of connections
> (TCP/UDP) that are determined by the physical interface itself?

Sure.  Divide the interface speed by the size of the smallest packets  
one can send including ethernet preamble, all headers, and the  
minimal gap between frames.  There's a PDF here with all of the details:

   ftp://ftp.cs.princeton.edu/techreports/2002/645.pdf

...but for 100Mbs full-duplex, you can send up to ~150 Kpps of  
minimum-size packets, or ~8 Kpps for max-sized packets.

> We have a PF load-balancing solution in place in front of a large  
> number of mail
> servers and we're considering using the same boxes to front our Name
> Server/Name Resolvers.  I'm concerned that the single uplink port  
> on the
> PF box will be overloaded with the number of connections.
>
> Any insights would be greatly appreciated.

One hopes that your "large number of mail servers" are only sending  
email to people who have actually opted in and wish to receive such  
email...?

-- 
-Chuck