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On Wed, 5 Oct 2005, Leonard Isham wrote:
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.
Sure VPNs can make things worse under some circumstances. What I was
trying to say was just that it can also help, as he was asking for under
some circumstances.
A live example:
I have a bad wireless (802.11B) network at home that causes my laptop to
loose network connectivity from time to time. All my sessions running
directly over internet then dies, while my SSH session to my email server
that runs over an OpenVPN link survives as my TAP-Win32 adapter never
reports "down".
--
_____________________________________________________________
Mathias Sundman (^) ASCII Ribbon Campaign
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