TCP: increase default initial receive window

Issue

• A patch was submitted to Linux that increases the default initial receive window on Linux. (http://marc.info/?l=linux-netdev&m=129290761921768&w=3)

• This optimizes for cases when a tcp payload cannot fit into a single initial receive window by increasing the initial rwnd to a point where a large percentage of this type of traffic in the wild would fit into the initial window.

• Please implement this patch in RHEL 6.