Subject: Re: dial-up over regular ethernet IP (xs4)
To: der Mouse <mouse@Rodents.Montreal.QC.CA>
From: Dennis Ferguson <>
List: tech-net
Date: 06/05/2002 17:18:18
> > I tried finding out more about PPPoE (of which the name suggests it
> > can do the trick),
> Not quite.  PPPoE is PPP over Ethernet; you want PPP over IP, or PPP
> over something else (eg telnet) over IP.  Unless your host and the
> target host are on the same Ethernet (or fake it with encapsulating
> bridges or some such), PPPoE will not help you.

There are two standard protocols for tunneling PPP over IP,
L2TP (RFC 2661) and PPTP (RFC 2637), so there's no particular need
to invent another one.  Actually only L2TP is standard, PPTP is a
Microsoft thing.  PPTP is supported quite widely for the thing the
Rogier wants to do, however, since Windows supports it and that is
what Windows uses it for.  PPTP is tunneled in GRE, while L2TP uses UDP.

> > Now, why would I want that?  In short: I'd like a cheap solution to a
> > problem.  Time and complexity are of little importance.
> > [VPNish thing]
> If you don't control the PPP server, what you propose is approximately
> impossible to set up; if you do, you don't need to bother with PPP, you
> can just encapsulate and tunnel.  (Depending on the reasons behind the
> on-campus requirement, you may need to encrypt to satisfy the security
> needs the requirement is there to address.  POTS dialup is
> significantly harder to tap than random network connections.)

If the PPP server supported one of these two protocols there'd be some hope.
Windows PPTP even supports some type of encryption, though I don't know
whether it uses IPSEC or something else.

Dennis Ferguson