# Revision history [back]

### The server sent many TCP Dup ack to client

Dear all,

The client uploaded the file to a server, and I see there are many TCP Dup ACK from server to client. The SLE number is the same, but the SRE number is increasing. But I did not see retransmission in the client to server's packets. Please advise what does it mean?

And will dup ack also reduce the congestion window on the client-side? Please advise. Thank you!

codec

[TCP Dup ACK 1300#1] 445 → 62113 [ACK] Seq=10598 Ack=957401 Win=65535 Len=0 SLE=958651 SRE=961151
.......
[TCP Dup ACK 1300#33] 445 → 62113 [ACK] Seq=10598 Ack=957401 Win=65535 Len=0 SLE=958651 SRE=1022401


### The server sent many TCP Dup ack to client

Dear all,

The client uploaded the file to a server, and I see there are many TCP Dup ACK from server to client. The SLE number is the same, but the SRE number is was increasing. But I I read the document because the server still receiving the data from the client before timeout so the SRE was increasing from the server to the client.

my questions are

1. will the out of order retransmission slow down the sending throughput from client to server? because I saw the sender did not see retransmission in the client to server's packets. Please advise what send out enough data to approach the TCP window size of the receiver.

2. If the receiver's TCP window size is 128KB, the sender sent large data at one time to the receiver but out of order when delivered to the receiver. How does it mean?

And the receiver to handle the delivered out of order package? will dup ack also reduce the congestion window on the client-side? Please advise. put the data into the buffer to wait for previous data until the buffer is full? Any suggested document I can read to understand the detail?

Thank you!

codec

[TCP Dup ACK 1300#1] 445 → 62113 [ACK] Seq=10598 Ack=957401 Win=65535 Len=0 SLE=958651 SRE=961151
.......
[TCP Dup ACK 1300#33] 445 → 62113 [ACK] Seq=10598 Ack=957401 Win=65535 Len=0 SLE=958651 SRE=1022401