A GbE device not able to forward full-rate odd-byte frames

it shouldnt matter - if the clock is wrong the the generated data would be arriving @ faster than 1 Gbps - 1/5 frame / sec or 1 part per million should be well with allowed clock tolerance

i suggest is you try this with different length tests - internal buffering probably takes up the slack up to some limit.

you have to ask whether it really matters that the device cannot handle that last 0.2% of continuous wirespeed thruput.

i suggest you run the traffic generator with 510 / 511 / 512 byte frames and see if 510 is OK as well - that should point out the anomaly on odd length frames.

FWIW odd transfers inside the device memory may have some extra overhead - but if the design is that close to the edge you should be having other issues.

Maybe they misalign internal frame transfers, so for odd length frames they do 2 DMA cycles per x bytes rather than 1? in which case this is likely a bug or hardware programming issue.

Hmm, from the numbers I would rather guess the device under test can only send even length frames and pads if asked to forward odd length ones.

Thanks for your comments. Yes, it seems that the device has some kind of internal bug when odd-sized frames are injected with the full 1Gbps rate. I tried 510, it was ok, tried

The device company claimed that Ethernet standard allows 200ppm clock difference (+-100ppm) among different Ethernet devices.

I'm wondering this kind of odd-byte problem is common in Ethernet devices. I think it's not, is it?

Regards, Jay Kim

Who knows. As it makes no difference in everyday operation you will only notice by looking at the wire.