> > You may have noticed all 2nd generation tunneling protocols now all
support
> > UDP (or other non TCP) based tunnels- L2TP, CIPE, IPSec, for example.
>
> Right. I write code for L2TP LACs and LNSes, among other devices for my
> day job; I have some experience in this area.

I like the description "Day Job". Fortunately besides the odd email I'm
having fun with the waterblaster and some deck furniture today :)

> One might argue that any kind of system will be (at least somewhat)
> unreliable if the network underneath is unreliable. :-)

Absolutely - which is why, of course, we have TCP in the first place
(besides the advantage of ports for services).

There's a couple of issues which have got muddled here. The first (The one
I was attempting to answer) was regarding Aarons problems with PPPoSSH,
whereas the second is the "Micro-Outages" of ~15s. Certainly 15 second
outages should have no effect whatsoever on TCP sessions for most OSes with
default timeout values, so I'm surprised that Juha was having dropped
sessions (are you on a Mac', Juha?). Likewise, most VPN's should cope fine
with this. However, my concern with PPPoSSH is that it may well cause
disconnects in this scenario because it is an inherently flawed VPN
solution. I don't think that it's quite fair to judge Telecom's performance
w.r.t "Micro-Outages" using PPPoSSH as an example. This doesn't mean of
course that Telecom are doing a good job, just that we should be careful in
equating the performance of _some_ VPN solutions with the performance of the
ADSL connection...

Personally, while I would find micro-outages annoying (to say the least!), I
wouldn't expect them to break connections. Has anyone done a comparative
study using Telecoms ADSL service to compare "normal" TCP-based services
with tunnels between the same pair of machines?

Brent Russell,
Department of Physics,
University of Otago.

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Received on Sat Jan 6 12:03:18 2001