Re: [Openvpn-users] Re: Can tunneled TCP connections survive Internet connection interruption?

[Mathias Sundman <mathias@xxxxxxxxxx>]

On Tue, 4 Oct 2005, Leonard Isham wrote:

> On 10/4/05, Kent Tong <kent@xxxxxxxxxxxx> wrote:
> > Leonard Isham <leonard.isham <at> gmail.com> writes:
> >
> > > Connections will fail and need to reestablish connectivity if the
> > > outage is lonf enough.
> >
> > Thanks for the reply. How long would be "long enough"? Or does it depends
> > on some factors other than the duration?
> >
> > How do people deal with this problem? It is a common need for us to
> > use client/server app over the VPN and if the database connection is
> > dropped regularly, then the app will be rendered useless.
>
> First lets make sure we are on the same page and set perspective.
>
> Bad connectivity is bad connectivity a VPN will not change that.
>
> If you application would fail with the connectivity loss it will with
> the VPN, or without it... game over... unless you can resolve the
> connectivity issue(s).

Not entirely true I believe. If "normal" connectivity is lost, some router 
on the way usually return ICMP destination-unreachble packets causing the 
TCP connection to be reset instantly. If you run your TCP application over 
an OpenVPN tunnel packets will just be silently dropped during the network 
outage until OpenVPN detect the network is down via --ping-restart, so TCP 
sessions inside the tunnel will survive until they time-out.

//Mathias

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