Tuning Cisco TCP Stack

I’ve been showing people the value of a TCP 3 way handshake baseline and its value.

In this specific example, a customer was using FTP to download files to his Cisco equipment and the process was taking too long. After further analysis I mentioned that if the TCP Window Size was larger and if TCP Selective Acknowledgements (SACK) were enabled, performance would improve.

We performed a capture and noted the current Window size and confirmed that TCP SACK was not enabled.

I then made the necessary changes and we performed another capture to confirm that the change worked.

Enjoy