TCP Performance

Tim Warnock timoid at timoid.org
Tue Aug 27 17:07:00 UTC 2013


> Regardless, your problem looks like either tail drops or packet loss, which
> you showed originally. The task is to find out where this is occurring, and
> which of the two it is. If you want to confirm what is going on, there are
> some great bandwidth calculators on the internet which will show you what
> bandwidth you can get with a given ms delay and % packet loss.
> 
> As far as flow control, its really outside the scope. If you ever need flow
> control, there is usually a specific reason like FCoE, and if not, it's
> generally better to just fix the backplane congestion issue if you can,
> than ever worry about using FC. The problem with FC isn't node to node, its
> when you have node to node to node with additional devices, it isn't smart
> enough to discriminate, and can crater your network 3 devices over when it
> would be much better to just lose a few packets.
> 
> -Blake

In my experience - if you're traversing licenced microwave links as indicated flow control will definitely need to be ON.

Check the radio modem stats to confirm but - if you're seeing lots of drops there you're overflowing the buffers on the radio modem.



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