1. UDP Reveive buffers: We like to increase the kernel's rcv buffers for
UDP.  This is done by setting SO_RCVBUF with setsockopt on the server
socket.  Under linux-2.2, SO_RCVBUF's max value is apparantly
/proc/sys/net/core/rmem_max times 2.  rmem_max has a default of 2^16-1, so
SO_RCVBUF's max is by default 2^17-1.  Setting rmem_max to 524280 (with
"echo 524280 > /proc/sys/net/core/rmem_max") allows SO_RCVBUF to be 1
megabyte.  

Why do we do this?  Netflow is fairly high-volume (last I checked, my
netflow devices were sending ~300kbits/s).  If our server is busy for a
few seconds reading or writing a database, or doing something else that
could take a while, we could lose packets if the rcv buffers are too
small.

Note that a receive buffer this large could cause trouble if we were using
it on a large number of sockets.
