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


  • Subject: Re: [Openvpn-users] Re: Can tunneled TCP connections survive Internet connection interruption?
  • From: Leonard Isham <leonard.isham@xxxxxxxxx>
  • Date: Wed, 5 Oct 2005 07:14:14 -0400

On 10/5/05, Mathias Sundman <mathias@xxxxxxxxxx> wrote:
> On Tue, 4 Oct 2005, Leonard Isham wrote:
> >
> > 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.
>

Depends on quite a number of "things," including traffic shaping that
silently drops packets.

  What I was attempting to explain is that if the loss of connectivity
is long enough to interrupt the application a VPN will not fix the
application. I have seen quite a few applications designed to work on
a LAN that are pushed into a WAN and or VPN environment and they
simply do not scale to the expanded environment.

 Also frequent connectivity losses can really mess up connections.

Packet analyser anyone.... This would allow you to see the details of
where the "rubber meets the road"  and troubleshoot in greater depth.

--
Leonard Isham, CISSP
Ostendo non ostento.

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