nanog mailing list archives
RE: TCP Performance
From: "Nick Olsen" <nick () flhsi com>
Date: Tue, 27 Aug 2013 13:11:52 -0400
I do indeed have stats for "TX Pause Frames" And they do increment. However, Our router is ignoring them since it doesn't support flow control. I guess my next question would be. In the scenario where we insert a switch between the radio and the router that does support flow control. Are we not only moving where the overflow is going to occur? Will we not see the router still burst traffic at line rate toward the switch, Which then buffer overflows sending to the radio on account of it receiving pause frames? Nick Olsen Network Operations (855) FLSPEED x106 ---------------------------------------- From: "Tim Warnock" <timoid () timoid org> Sent: Tuesday, August 27, 2013 1:08 PM To: "Blake Dunlap" <ikiris () gmail com>, "nick () flhsi com" <nick () flhsi com> Cc: "nanog () nanog org" <nanog () nanog org> Subject: RE: TCP Performance
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.
Current thread:
- TCP Performance Nick Olsen (Aug 27)
- Re: TCP Performance Blake Dunlap (Aug 27)
- <Possible follow-ups>
- Re: TCP Performance Nick Olsen (Aug 27)
- Re: TCP Performance Blake Dunlap (Aug 27)
- RE: TCP Performance Tim Warnock (Aug 27)
- Re: TCP Performance Blake Dunlap (Aug 27)
- Re: TCP Performance Nick Olsen (Aug 27)
- Re: TCP Performance Nick Olsen (Aug 27)
- RE: TCP Performance Nick Olsen (Aug 27)
- Re: TCP Performance Blake Dunlap (Aug 27)
- Re: TCP Performance Nick Olsen (Aug 27)