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ACK from server not received by client

Hi, Can anyone help me to understand this captures?

client 72.189.226.91 server 192.168.78.118 port 8086

Client report random connection problem on connect to server port 8086. I attach the anon captures

For example (one error time):

  • Captures at Client side (client_side_anon.pcapng) 2020-11-11 12:39:49,591869 72.189.226.91 192.168.78.118 TCP 74 43188 → 8086 [SYN] Seq=0 Win=14600 Len=0 MSS=1460 SACK_PERM=1 TSval=739647657 TSecr=0 WS=64

The server doesn't response to this SYN with an ACK (really yes but it does not receive it, see below the capture on the server)

Client request again 2020-11-11 12:39:52,595107 72.189.226.91 192.168.78.118 TCP 74 [TCP Retransmission] 43188 → 8086 [SYN] Seq=0 Win=14600 Len=0 MSS=1460 SACK_PERM=1 TSval=739648408 TSecr=0 WS=64 ... at this point fail.

  • Caputres at Server side (server_side_anon.pcacpng) The SYNC is received by the server

2020-11-11 12:39:49,599532 72.189.226.91 192.168.78.118 TCP 74 43188 → 8086 [SYN] Seq=0 Win=14600 Len=0 MSS=1460 SACK_PERM=1 TSval=739647657 TSecr=0 WS=64 and it response with ACK

2020-11-11 12:39:49,599568 192.168.78.118 72.189.226.91 TCP 66 8086 → 43188 [ACK] Seq=1 Ack=2413873066 Win=249 Len=0 TSval=190156218 TSecr=697151199

But this ACK is never seen at client side

Why this ACK i not received by the client side and it requet again? and the server resends it ... and so on. TCP Retransmission Where can the problem be here?

Captures: link text link text

Blockquote

ACK from server not received by client

Hi, Can anyone help me to understand this captures?

client 72.189.226.91 server 192.168.78.118 port 8086

Client report random connection problem on connect to server port 8086. I attach the anon captures

For example (one error time):

  • Captures at Client side (client_side_anon.pcapng) (client_side_anon.pcapng)

    2020-11-11 12:39:49,591869  72.189.226.91   192.168.78.118  TCP 74  43188 → 8086 [SYN] Seq=0 Win=14600 Len=0 MSS=1460 SACK_PERM=1 TSval=739647657 TSecr=0 WS=64
WS=64

The server doesn't response to this SYN with an ACK (really yes but it does not receive it, see below the capture on the server)

Client request again again

2020-11-11 12:39:52,595107  72.189.226.91   192.168.78.118  TCP 74  [TCP Retransmission] 43188 → 8086 [SYN] Seq=0 Win=14600 Len=0 MSS=1460 SACK_PERM=1 TSval=739648408 TSecr=0 WS=64
...

...

at this point fail.

  • Caputres

    Captures at Server side (server_side_anon.pcacpng) The SYNC is received by the server

2020-11-11 12:39:49,599532  72.189.226.91   192.168.78.118  TCP 74  43188 → 8086 [SYN] Seq=0 Win=14600 Len=0 MSS=1460 SACK_PERM=1 TSval=739647657 TSecr=0 WS=64

and it response with ACK

2020-11-11 12:39:49,599568  192.168.78.118  72.189.226.91   TCP 66  8086 → 43188 [ACK] Seq=1 Ack=2413873066 Win=249 Len=0 TSval=190156218 TSecr=697151199

TSecr=697151199

But this ACK is never seen at client side

Why this ACK i not received by the client side and it requet again? and the server resends it ... and so on. TCP Retransmission Where can the problem be here?

Captures: link textCapture 1 link textCapture 2

Blockquote