[e2e] tcp connection timeout

[Joe Touch]

Tim Dorcey wrote:
>> 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

That sounds like a "NAT-traversing tunnel" property, such as might
already be provided by PPP (which already has keepalives).

Joe