[En-Nut-Discussion] Network Link state on at91_emac and others

[Harald Kipp]

Ole Reinhardt wrote:

> The PC will mostly drop the connection just in the moment of
> disconnection as most OSes behave like this.

If this is the case, then "most OSes" are plain wrong.

We just tried Kubuntu (Kernel 2.6.22) and Windows 2000 SP4:

1. Establishing a TELNET connection to our Internet gate.
2. Pull the cable at the PC running the TELNET client.
3. Reconnecting the cable after a few seconds.

On both systems the TELNET connection is still alive. If you like we can 
try OS X too, but I'm sure it will behave the same way unless you 
enabled special keepalive options.

> That's why I don't see having a timeout or even holding the
> sockets is a good idea.

I will not getting tired to argue, that TCP is designed to keep 
connections on broken links.

I will not getting tired to argue, that dropping connections on Ethernet 
link loss will not solve any problem.

I will not getting tired to argue, that implementing keepalive is the 
only correct way to detect broken links.

I will not getting tired to argue, that keepalive, if implemented, must 
be disabled by default.

Harald