4

A nearby question has brought to my attention the ss utility on Linux, another utility to investigate sockets.

It would appear that it may be a great tool to monitor the performance of, say, an ssh session over a portable mobile hotspot, where using ping would be fruitless.

# sh -c 'date; while(true); do echo -n `date +%H%M%S`" "; ss -i |fgrep -A1 :ssh |fgrep rtt |cut -d" " -f3- ;sleep 10;done'
Tue Feb 11 09:16:08 PST 2014
091608 wscale:2,7 rto:603.333 rtt:230.833/93.333 ato:63.333 cwnd:9 ssthresh:6 send 436.7Kbps rcv_rtt:104953 rcv_space:779096
091618 wscale:2,7 rto:626.666 rtt:228.75/100 ato:63.333 cwnd:9 ssthresh:6 send 440.7Kbps rcv_rtt:104953 rcv_space:779096
091628 wscale:2,7 rto:676.666 rtt:244.166/105.833 ato:63.333 cwnd:5 ssthresh:6 send 229.4Kbps rcv_rtt:104953 rcv_space:779096
091638 wscale:2,7 rto:663.333 rtt:232.5/103.333 ato:63.333 cwnd:6 ssthresh:6 send 289.0Kbps rcv_rtt:104953 rcv_space:779096
091648 wscale:2,7 rto:643.333 rtt:226.666/89.166 ato:63.333 cwnd:6 ssthresh:6 send 296.5Kbps rcv_rtt:104953 rcv_space:779096
091658 wscale:2,7 rto:736.666 rtt:249.166/122.5 ato:40 cwnd:6 ssthresh:6 send 269.7Kbps rcv_rtt:104953 rcv_space:779096
091708 wscale:2,7 rto:693.333 rtt:232.083/106.666 ato:40 cwnd:7 ssthresh:6 send 337.8Kbps rcv_rtt:104953 rcv_space:779096
091718 wscale:2,7 rto:683.333 rtt:228.75/86.666 ato:40 cwnd:7 ssthresh:6 send 342.7Kbps rcv_rtt:104953 rcv_space:779096
091728 wscale:2,7 rto:680 rtt:242.916/110 ato:40 cwnd:8 ssthresh:6 send 368.9Kbps rcv_rtt:104953 rcv_space:779096
091738 wscale:2,7 rto:503.333 rtt:183.333/12.5 ato:40 cwnd:40 ssthresh:9 send 2.4Mbps rcv_rtt:104953 rcv_space:779096
091748 wscale:2,7 rto:823.333 rtt:269.583/80 ato:43.333 cwnd:40 ssthresh:45 send 1.7Mbps rcv_rtt:104953 rcv_space:779096
^C

My understanding is that rtt is probably the most interesting parameter here.

Is there a way to monitor these parameters through some kind of non-pull-based API, or get even more info about the doings of an individual connection?

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