TBF or Token Bucket Filter is a tool from the linux kernel. It can be inserted as a “queueing discipline” for an Ethernet device. TBF is usually employed to limit the bandwidth.

I tried to configure TBF on my Ubuntu 9.10 VMware box, but I got disappointing results: I only got around 100kbps, no matter what I configured. I tried the same setup on a physical server, with the same results.

After a full afternoon of experimenting and Googling, I was able to solve the issue by disabling offloading:

# ethtool -k eth0
Offload parameters for eth0:
Cannot get device flags: Operation not supported
rx-checksumming: on
tx-checksumming: on
scatter-gather: on
tcp-segmentation-offload: on
udp-fragmentation-offload: off
generic-segmentation-offload: on
generic-receive-offload: off
large-receive-offload: off

# ethtool -K eth0 sg off
# ethtool -K eth0 tso off
# ethtool -K eth0 gso off

# ethtool -k eth0
Offload parameters for eth0:
Cannot get device flags: Operation not supported
rx-checksumming: on
tx-checksumming: on
scatter-gather: off
tcp-segmentation-offload: off
udp-fragmentation-offload: off
generic-segmentation-offload: off
generic-receive-offload: off
large-receive-offload: off

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