[RHEL6] TCP-Tunneled PPP links hangs after random amount of time.

Issue

• When transferring a large amount of data transfer over PPP link tunneled on a TCP pipe, the PPP communications stalls after random amount of time.

• Here is a sample network setup:

=== NETWORK LAYOUT=== 

    |1|                          |2|                          |3|
172.30.7.16  ---Ethernet---- 172.30.7.22 ----Ethernet---- 172.30.7.11
172.30.7.7   ---PPPoTCP----- 172.30.7.6

• The issue happens while system |3| tries to establish communications with system |1| PPP endpoint (172.30.7.7).