Hello, Could anyone explain the behavior I observe below?
I have the following registration extract: a packet with seq=3020828 is sent out but never acknowledged. The packet is also retransmitted multiple times, but the receiver keeps acknowledging the previous seq:
57788 2018-07-16 15:36:20.552618000 10.245.40.74 10.245.54.13 TCP 2974 64613 -> 14004 [ACK] Seq=3020828 Ack=73535403 Win=65536 Len=2920
...
58376 2018-07-16 15:36:20.851770000 10.245.40.74 10.245.54.13 TCP 1514 [TCP Retransmission] 64613 -> 14004 [ACK] Seq=3020828 Ack=74313583 Win=1296 Len=1460
58378 2018-07-16 15:36:21.101721000 10.245.54.13 10.245.40.74 TCP 1350 14004 -> 64613 [PSH, ACK] Seq=74313583 Ack=3020828 Win=4096 Len=1296 [TCP segment of a reassembled PDU]
...
60992 2018-07-16 15:36:22.652682000 10.245.40.74 10.245.54.13 TCP 1514 [TCP Retransmission] 64613 -> 14004 [ACK] Seq=3020828 Ack=77762103 Win=1296 Len=1460
60994 2018-07-16 15:36:22.658427000 10.245.54.13 10.245.40.74 TCP 1514 14004 -> 64613 [ACK] Seq=77762103 Ack=3020828 Win=4096 Len=1460 [TCP segment of a reassembled PDU]
On the receiver side, I do see the packet coming in, but it is someone ignored and it keeps acknowledging the previous seq:
13878 2018-07-16 15:36:20.825430000 10.245.40.74 10.245.54.13 TCP 1514 [TCP Retransmission] 64613 -> 14004 [ACK] Seq=3020828 Ack=74313583 Win=1296 Len=1460
18810 2018-07-16 15:36:36.047313000 10.245.54.13 10.245.40.74 TCP 29254 14004 -> 64613 [ACK] Seq=114189103 Ack=3020828 Win=20480 Len=29200 [TCP segment of a reassembled PDU]
...
13991 2018-07-16 15:36:21.425465000 10.245.40.74 10.245.54.13 TCP 1514 [TCP Retransmission] 64613 -> 14004 [ACK] Seq=3020828 Ack=74834803 Win=1296 Len=1460
13993 2018-07-16 15:36:21.433178000 10.245.54.13 10.245.40.74 TCP 27794 14004 -> 64613 [ACK] Seq=74834803 Ack=3020828 Win=4096 Len=27740 [TCP segment of a reassembled PDU]
According to the ACK packet, there is enough room in the recv window, but somehow the packet is ignored. After 5 unsuccessful retransmission, the sender eventually drops the connection.
Thanks.
