Network Issues

Testing network performance

netcat

Netcat

From client machine to server ...

On server:

netcat -l -p 1234 > /dev/null

On client:

dd if=/dev/zero bs=1M count=1000 |netcat server 1234

From server to client machine ... On client:

netcat -l -p 1234 > /dev/null

On server:

dd if=/dev/zero bs=1M count=1000 |netcat client 1234

You can exchange /dev/zero with e.g. /dev/md0 (for a raid device) or /dev/sda for testing your harddisk performance.

ethtool

Ethtool gives you important informations over your network card, its settings and actual modes:

ethtool eth0

sysctl

Settings for tpc ip settings:

for i in rmem wmem mem; do sysctl net.ipv4.tcp_${i}; done

gives e.g. on an older machine (366MHz AMD K6, 33MHz bus)

net.ipv4.tcp_rmem = 4096	87380	577600
net.ipv4.tcp_wmem = 4096	16384	577600
net.ipv4.tcp_mem = 13536	18050	27072

and on a "newer" system (AMD Athlon XP 2000+, 133MHz bus)

net.ipv4.tcp_rmem = 4096	87380	4194304
net.ipv4.tcp_wmem = 4096	16384	4194304
net.ipv4.tcp_mem = 170592	227456	341184

I can be set with e.g.:

sysctl -w net.ipv4.tcp_wmem="4096 16384 1048576"

But consider: better know what you are doing! On modern linux systems this should not be necessary.

iperf

Messures the network perfomance.

On the server do (start iperf in server mode)

iperf -s

On the client machine do

iperf -c server_ip -i 1 -t 10

Typical values

• 15-25 Mbits/sec for a 54Mbit Wireless LAN
• 300-350 Mbits/sec for a Gigabit LAN

The values depend heavily to

• quality of the network card
• quality of the cable (already CAT 6 !?) or wireless connection
• bus speed
• processor speed

Links

• Main insperation for this articele: linuxquestions.org - gigabit ethernet performance