[rescue] What is this traffic?

microcode at zoho.com microcode at zoho.com
Thu Oct 29 12:05:05 CDT 2015

On Thu, Oct 29, 2015 at 04:34:38PM +0000, Mike Spooner wrote:
> Sorry to be late to this thread... from the description of observed
> behaviour, this sounds very much like the switch and router have a
> disagreement about Ethernet "duplex" mode - during negotiation, one has
> picked half-duplex, the other full-duplex, causing a stream of "late
> collision" errors on the one using half-duplex mode.
> In this situation, I have seen effective throughput drop to 10% of what
> should be possible, due to all the errors and semi-synchronised
> transmission-backoffs.

The throughput seems fine. I can get the rated performance from my carrier,
just not from my ISP. I can get full rated switch bandwidth between boxes on
the LAN. The performance issue is almost certainly between me and the ISP,
specifically likely between the carrier and the ISP. But the finger pointing
makes fixing it unlikely.

> If you have access to any kind of "configuration settings" interface on the
> router, and that provides a way to change the Ethernet duplex setting on
> the "inside" interface, it may well be worth changing that, but be careful
> to not cut yourself off if it does not work (ie: use a modern PC directly
> conencted to apply the change; don't use a 20+ year-old Sun workstation).

I will look and if it blows up I can always hard reset the router.

> If this resolves the storm, half-duplex-all-over isn't ideal, but should
> give you between 50% and 80% of the theoretical throughput (depends a bit
> on the exact traffic pattern).

I was not able to find any setting like that on the router. Thanks for your
email though.


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