SC3 kernel tweaks

These are the sysctl settings which are a good starting point for tuning file transfer rates.

### IPV4 specific settings
net.ipv4.tcp_timestamps = 0 # turns TCP timestamp support off, default 1, reduces CPU use
net.ipv4.tcp_sack = 1 # turn SACK support off, default on

# on systems with a VERY fast bus -> memory interface this is the big gainer
net.ipv4.tcp_rmem = 4096  262144 1048576 # sets min/default/max TCP read buffer, default 4096 87380 174760
net.ipv4.tcp_wmem = 4096  262144 1048576 # sets min/pressure/max TCP write buffer, default 4096 16384 131072
#net.ipv4.tcp_mem  = 262144 4194304 8388608 # sets min/pressure/max TCP buffer space, default 31744 32256 32768
net.ipv4.tcp_mem  =  97280  131072 262144  # sets min/pressure/max TCP buffer space, default 31744 32256 32768

### CORE settings (mostly for socket and UDP effect)
net.core.rmem_max =  1048575 # maximum receive socket buffer size, default 131071
net.core.wmem_max =  1048575 # maximum send socket buffer size, default 131071
net.core.rmem_default = 262143 # default receive socket buffer size, default 65535
net.core.wmem_default = 262143 # default send socket buffer size, default 65535
net.core.optmem_max = 262143 # maximum amount of option memory buffers, default 10240
net.core.netdev_max_backlog = 1000 # number of unprocessed input packets before kernel starts dropping them, default 300

To use them, save to a file and do

 # sysctl -p SC3-TWEAK-FILE