That's a great question! The answer seems to be "Neither" (at least, using
commands with which I'm familiar).
These commands were done on a freshly booted VM where a few data movement tests
were performed before starting the below.
# netstat -i
Kernel Interface table
Iface MTU RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0 1500 82560 0 0 0 86307 0 0 0 BMRU
lo 65536 278 0 0 0 278 0 0 0 LRU
tun0 1422 82192 0 0 0 89595 0 0 0 MOPRU
But:
# netstat -s | egrep -i 'drop|lost|retrans'
3343 outgoing packets dropped
101 dropped because of missing route
2975 segments retransmited
TCPLostRetransmit: 5
2963 fast retransmits
2 forward retransmits
3 retransmits in slow start
1 SACK retransmits failed
And, after writing a ~30meg file:
4731 outgoing packets dropped
101 dropped because of missing route
4362 segments retransmited
TCPLostRetransmit: 5
4349 fast retransmits
2 forward retransmits
3 retransmits in slow start
1 SACK retransmits failed
TCPSynRetrans: 1
# netstat -i
Kernel Interface table
Iface MTU RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0 1500 92832 0 0 0 111539 0 0 0 BMRU
lo 65536 308 0 0 0 308 0 0 0 LRU
tun0 1422 92391 0 0 0 116211 0 0 0 MOPRU
...and if I set on the machine and just "look around" reading man pages or
whatever for 10 minutes, the netstat -s results remain static.
So it appears that things go wonky only when under stress.
As far as getting access to a test environment, it's possible, but will take a
lot of coordination on our end so would like to hold that as a last resort for
now.
-----Original Message-----
From: David Woodhouse [mailto:[email protected]]
Sent: Sunday, March 17, 2019 4:39 PM
To: Nikos Mavrogiannopoulos; Phillips, Tony
Cc: [email protected]
Subject: Re: [EXTERNAL] Re: What throughput is reasonable?
On Sun, 2019-03-17 at 12:44 +0000, Nikos Mavrogiannopoulos wrote:
> David, Could it be we set a smaller snd or recv buffer to reduce
> latency in openconnect? In ocserv we have something configurable for
> that. BTW Tony, have you tried a more recent rhel7?
Tony, on which interface are the packets being dropped? Is it the tun
device? If so, perhaps increasing the buffer with TUNSETSNDBUF might
help?
Are you able to give us access to a test environment?
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