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why only the first packet retransmission

asked 2021-04-29 08:29:36 +0000

Kasa gravatar image

I did an experiment about retransmission. I am confused that why from 15:23:17 to 15:23:35 only seq 120091 retransmits. In my opinion,seq number from 120627 to 130275 should retransmit too,because their RTOs are time out. But they didn't retransmited until seq 120091 retransmission finished. Does anyone know why? ---------------------------------------------------'DATA-------------------------------

421 2021-04-25 15:23:16.912689    0x3001 (12289) 1.1.1.1               2.2.2.2               TCP      54     1079 → 23 [ACK] Seq=68 Ack=120091 Win=57352 Len=0
422 2021-04-25 15:23:16.922435    0x6701 (26369) 2.2.2.2               1.1.1.1               TCP      590    23 → 1079 [ACK] Seq=120091 Ack=68 Win=4061 Len=536
423 2021-04-25 15:23:16.932525    0x6702 (26370) 2.2.2.2               1.1.1.1               TCP      590    23 → 1079 [ACK] Seq=120627 Ack=68 Win=4061 Len=536
424 2021-04-25 15:23:16.942618    0x6703 (26371) 2.2.2.2               1.1.1.1               TCP      590    23 → 1079 [ACK] Seq=121163 Ack=68 Win=4061 Len=536
425 2021-04-25 15:23:16.952712    0x6704 (26372) 2.2.2.2               1.1.1.1               TCP      590    23 → 1079 [ACK] Seq=121699 Ack=68 Win=4061 Len=536
426 2021-04-25 15:23:16.962805    0x6705 (26373) 2.2.2.2               1.1.1.1               TCP      590    23 → 1079 [ACK] Seq=122235 Ack=68 Win=4061 Len=536
427 2021-04-25 15:23:16.972898    0x6706 (26374) 2.2.2.2               1.1.1.1               TCP      590    23 → 1079 [ACK] Seq=122771 Ack=68 Win=4061 Len=536
428 2021-04-25 15:23:16.982990    0x6707 (26375) 2.2.2.2               1.1.1.1               TCP      590    23 → 1079 [ACK] Seq=123307 Ack=68 Win=4061 Len=536
429 2021-04-25 15:23:16.993084    0x6708 (26376) 2.2.2.2               1.1.1.1               TCP      590    23 → 1079 [ACK] Seq=123843 Ack=68 Win=4061 Len=536
430 2021-04-25 15:23:17.003179    0x6709 (26377) 2.2.2.2               1.1.1.1               TCP      590    23 → 1079 [ACK] Seq=124379 Ack=68 Win=4061 Len=536
431 2021-04-25 15:23:17.013279    0x670a (26378) 2.2.2.2               1.1.1.1               TCP      590    23 → 1079 [ACK] Seq=124915 Ack=68 Win=4061 Len=536
432 2021-04-25 15:23:17.023372    0x670b (26379) 2.2.2.2               1.1.1.1               TCP      590    23 → 1079 [ACK] Seq=125451 Ack=68 Win=4061 Len=536
433 2021-04-25 15:23:17.033469    0x670c (26380) 2.2.2.2               1.1.1.1               TCP      590    23 → 1079 [ACK] Seq=125987 Ack=68 Win=4061 Len=536
434 2021-04-25 15:23:17.043562    0x670d (26381) 2.2.2.2               1.1.1.1               TCP      590    23 → 1079 [ACK] Seq=126523 Ack=68 Win=4061 Len=536
435 2021-04-25 15:23:17.053653    0x670e (26382) 2.2.2.2               1.1.1.1               TCP      590    23 → 1079 [ACK] Seq=127059 Ack=68 Win=4061 Len=536
436 2021-04-25 15:23:17.063746    0x670f (26383) 2 ...
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answered 2021-04-29 08:50:12 +0000

SYN-bit gravatar image

That's how it is defined in the first RFC detailing the TCP protocol (RFC 793):

   RETRANSMISSION TIMEOUT

    For any state if the retransmission timeout expires on a segment in
    the retransmission queue, send the segment at the front of the
    retransmission queue again, reinitialize the retransmission timer,
    and return.
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Asked: 2021-04-29 08:29:36 +0000

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Last updated: Apr 29