[Linux-aus] strange LAN congestion problem

Adam Nielsen a.nielsen at shikadi.net
Tue Jun 17 09:49:10 EST 2014

Hi all,

> Hi Nick ..  I agree with Kevin and Graham, you are probably
> exhausting the buffers/memory in the ADSL router/switch.

I'm a bit confused about these suggestions.  If I understand the
original problem correctly, you can transfer data over the LAN at
1Gbps, but if there is a TCP connection going through the LAN and out
over ADSL then suddenly the 1Gbps LAN drops to ADSL speeds?

How are the buffers in the ADSL router affecting the data transferred
between the two PCs when that traffic is going through an independent
(D-Link) switch?  The traffic is never reaching the ADSL router.

Perhaps the problem is that there is some sort of QoS service running
on the PCs themselves, so when you upload a file and the ADSL service
limits it to 40kB/s, the QoS kicks in and drops *all* traffic on that
NIC to the same speed as it thinks that is the total bandwidth

Nick doesn't say what OS is running on the PCs or whether there is any
QoS active, but I would probably start looking there.


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