Failure:

    keepalive idle time: 60
    keepalive probe count: 6
    keepalive probe interval: 10

    14:20:29.842918 IP 128.138.158.139.55241 > 128.138.158.131.22: . ack 1 win 1460 <nop,nop,timestamp 18421038 25364172>
    14:20:29.848884 IP 128.138.158.131.22 > 128.138.158.139.55241: P 1:43(42) ack 1 win 5792 <nop,nop,timestamp 25364173 18421038>
    14:20:29.848958 IP 128.138.158.139.55241 > 128.138.158.131.22: . ack 43 win 1460 <nop,nop,timestamp 18421044 25364173>

    [*** pull plug on B ***]

    14:21:29.839127 IP 128.138.158.139.55241 > 128.138.158.131.22: . ack 43 win 1460 <nop,nop,timestamp 18481044 25364173>

    [*** then nothing ***]

    So the first probe goes out fine, then nothing.


Failure: 

    keepalive idle time: 10
    keepalive probe count: 6
    keepalive probe interval: 10

    14:34:58.373950 IP 128.138.158.139.48848 > 128.138.158.131.22: . ack 1 win 1460 <nop,nop,timestamp 19289701 25451025>
    14:34:58.379770 IP 128.138.158.131.22 > 128.138.158.139.48848: P 1:43(42) ack 1 win 5792 <nop,nop,timestamp 25451025 19289701>
    14:34:58.379835 IP 128.138.158.139.48848 > 128.138.158.131.22: . ack 43 win 1460 <nop,nop,timestamp 19289707 25451025>

    [*** pull plug on B ***]

    14:35:08.377644 IP 128.138.158.139.48848 > 128.138.158.131.22: . ack 43 win 1460 <nop,nop,timestamp 19299707 25451025>
    14:35:18.376148 IP 128.138.158.139.48848 > 128.138.158.131.22: . ack 43 win 1460 <nop,nop,timestamp 19309707 25451025>
    14:35:28.374607 IP 128.138.158.139.48848 > 128.138.158.131.22: . ack 43 win 1460 <nop,nop,timestamp 19319707 25451025>
    14:35:38.373120 IP 128.138.158.139.48848 > 128.138.158.131.22: . ack 43 win 1460 <nop,nop,timestamp 19329707 25451025>
    14:35:48.371585 IP 128.138.158.139.48848 > 128.138.158.131.22: . ack 43 win 1460 <nop,nop,timestamp 19339707 25451025>

    [*** then nothing ***]


Success:

    keepalive idle time: 10
    keepalive probe count: 3
    keepalive probe interval: 5

    14:44:18.536603 IP 128.138.158.139.41102 > 128.138.158.131.22: . ack 1 win 1460 <nop,nop,timestamp 19849949 25507041>
    14:44:18.542476 IP 128.138.158.131.22 > 128.138.158.139.41102: P 1:43(42) ack 1 win 5792 <nop,nop,timestamp 25507041 19849949>
    14:44:18.542537 IP 128.138.158.139.41102 > 128.138.158.131.22: . ack 43 win 1460 <nop,nop,timestamp 19849955 25507041>

    [one probe just to see it work]

    14:44:28.540486 IP 128.138.158.139.41102 > 128.138.158.131.22: . ack 43 win 1460 <nop,nop,timestamp 19859955 25507041>
    14:44:28.540772 IP 128.138.158.131.22 > 128.138.158.139.41102: . ack 1 win 5792 <nop,nop,timestamp 25508041 19849955>

    [pull the plug on B]

    14:44:38.538944 IP 128.138.158.139.41102 > 128.138.158.131.22: . ack 43 win 1460 <nop,nop,timestamp 19869955 25508041>
    14:44:43.538206 IP 128.138.158.139.41102 > 128.138.158.131.22: . ack 43 win 1460 <nop,nop,timestamp 19874955 25508041>
    14:44:48.572597 IP 128.138.158.139.41102 > 128.138.158.131.22: . ack 43 win 1460 <nop,nop,timestamp 19879990 25508041>
    14:44:53.572534 IP 128.138.158.139.41102 > 128.138.158.131.22: R 1:1(0) ack 43 win 1460 <nop,nop,timestamp 19884990 25508041>

    Textbook behavior.