matth...@fastmail.us writes:
I am amused by "older laptop" and "USB-C". Those don't go together! I
call anything new enough to have USB-C "relatively new".
> $ ifconfig ure0
> ure0: flags=0x8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
> capabilities=0x3ff00<IP4CSUM_Rx,IP4CSUM_Tx,TCP4CSUM_Rx,TCP4CSUM_Tx>
> capabilities=0x3ff00<UDP4CSUM_Rx,UDP4CSUM_Tx,TCP6CSUM_Rx,TCP6CSUM_Tx>
> capabilities=0x3ff00<UDP6CSUM_Rx,UDP6CSUM_Tx>
> enabled=0
> ec_capabilities=0x1<VLAN_MTU>
> ec_enabled=0
> address: 9c:eb:e8:54:53:73
> media: Ethernet autoselect (1000baseT full-duplex)
> status: active
> However, using iperf3 to measure networking performance, it seems a bit
> substandard:
>
> $ iperf3 -c 192.168.1.131
> [ ID] Interval Transfer Bitrate Retr
> [ 5] 0.00-10.02 sec 55.4 MBytes 46.4 Mbits/sec 0 sender
> [ 5] 0.00-10.24 sec 55.5 MBytes 45.4 Mbits/sec receiver
>From other comments, it seems like this device is just not that good.
The only suggestions I would have to debug it are:
- Test in UDP mode also. TCP is extremely sensitive to loss.
iperf/TCP measures how well you can do TCP which is what you usually
care about, and if it's close to line rate (even 350/1000), you know
all is well. But if it's slow, you don't know if each packet is
slow with little loss, or loss often, or loss above a certain rate,
or ?
- Look at "netstat -i" and error counters, and also do "netstat -s"
before and after and diff them, on a system with nothing else
happening (maybe even single user). Anything that changes that you
don't expect is interesting and I've found a lot of issues this way.
- Run tcpdump and save to a file, and use tcpdump2xplot from
graphics/xplot-devel to visualize it, after patching up the perl
program or editing the trace to make it look like tcpdump used to
look. This is a lot of effort, and requires you to not only learn
to deal with that software, but to really understand TCP. But it
can be very illuminating as to what is going on.
You can also select one stream and just examine the text output.
