the MTU of 1500 was chosen for 10Mbps ethernet and was kept
for 100Mbps and 1Gbps ethernet for backwards compatibility
on mixed networks. However MTU=1500 is too small
for 100Mbps and 1Gbps ethernet. In Gbps ethernet jumbo frames
(ie bigger MTU) is used to increase throughput.
On my LVS performance page I found that decreasing the MTU
decreased max throughput on 100Mbps ethernet. Since the decrease
was approx linear with MTU, I wondered if the linearity would
still be linear beyond 1500, and if increasing the MTU
on 100Mbps would increase max throughput (ignoring
the problem of fragmenting packets once they got off the LAN).
I couldn't increase the MTU above 1500 with ifconfig or ip link.
I found that the MTU seemed to be defined in
ETH_DATA_LEN and ETH_FRAME_LEN
and increased these by 1500, recompiled the kernel and net-tools
and rebooted. I still can't install a device with MTU>1500
Joseph Mack PhD, Senior Systems Engineer, Lockheed Martin
contractor to the National Environmental Supercomputer Center,
mailto:mack.joseph@xxxxxxx ph# 919-541-0007, RTP, NC, USA