Reducing buffer usage for a TCP proxy session between a client and a server by a service gateway includes: determining a first round trip time (RTT) for a server side TCP session and determining a second RTT for a client side TCP session; comparing the first RTT with the second RTT; determining whether the second RTT exceeds the first RTT beyond a threshold; if so, then calculating a desired RTT based on the second RTT; and setting a timer according to the calculated desired RTT, where a TCP acknowledgment for the server side TCP session is delayed until the timer expires. The desired RTT may be calculated as a percentage of the second RTT or as the second RTT minus a predetermined value. The service gateway waits until the timer has expired before sending a TCP acknowledgment data packet to the server.