Nimbostratus
Increasing the buffer low setting allows the BIG-IP system to buffer more server response data, esp useful for WAN connections, since the client side of the connection is typically "slower" than the server side. Although it does increase the memory required for each connection, it's a much more effective use of your servers than the alternative, which is to slow the server down to the client's speed by closing the server-side receive window.
A larger buffer size allows the servers to respond as quickly as they are able & close the connection, and allows BIG-IP to manage the client side of the connection independently. When the buffer high setting is reached, BIG-IP will close the serverside receive window until some of the buffered data is sent to the client. When the amount of data buffered in the proxy buffer has drained to the proxy buffer low threshold setting, the BIG-IP system opens the receive window to the server again, allowing the server to send more data.
With the buffer low set to 4096, the server receive window doesn't open again until there is < 4096 bytes of data waiting to be sent to the client.
Setting the 2 values the same allows the receive window, once closed, to open again as soon as any data at all is sent to the client, rather than having to wait for the buffer to drain to a significantly lower value: Once the buffer high setting is reached, the recv window is closed. But as soon as BIG-IP transmits any data to the client, the buffer size drops below the buffer low setting, and the receive window is opened immediately.
There's a solution on Ask5 (SOL3422) with some additional details that might be helpful: Click here
HTH
/deb
Nimbostratus