Changing the TCP Window Size
You want to change the TCP Window Size

The TCP window-size regulates the amount of unacknowledged data the Edge SWG (ProxySG) receives before sending an acknowledgement. The default TCP window size is 65535 bytes (64Kbytes) on SGOS 6.7.3.x and older version. Starting with SGOS 6.7.4.1 - default TCP window size has been increased from 64K to 256K. Starting with SGOS 7.2.1.1 - default TCP window size has been increased from 256K to 1MB. ProxySG will accept any value between 8192 bytes and 4194240 bytes for the TCP window size configuration.

You can change the TCP window size through the Command Line Interface (CLI) using the following command:

#(config) tcp-ip window-size size

Verify the change using the following command:

#(config) show tcp-ip

On a TCP connection to achieve window size larger 64KBytes RFC1323 has to enabled on the Edge SWG (ProxySG). By default it is enabled on the Edge SWG (ProxySG). Also the next hop device which proxy is communicating with, RFC1323 has to be supported there as well.