[e2e] tcp connection timeout

[Tim Dorcey]

> What is the point of having a long-lived TCP session with
> keepalive in the 21st century?

One possible consideration is that many applications operate over a network
where traffic is not allowed to flow in one direction unless traffic has
recently been sent in the other direction.  I am thinking of NAT's and
firewalls.  If an application wants a host "outside" the NAT/firewall to be
able to send something to it at an arbitrary time, there seems no other
option then to periodically send something out to it.  Since these devices
often operate at the transport level, there might be some rational for
putting this functionality in the host transport layer.

Tim