[LINK] RFI: MACs and PPP

[Chris Maltby]

> Roger Clarke wrote:
> >The question:  is there any such concept as a MAC for the modem port 
> >of a device?  If not, is there any reliable identifier of the machine 
> >on a dial-up connection?
> 
On Tue, Nov 09, 2004 at 11:41:06AM +1100, Carl Makin wrote:
> No.  There is currently no reliable identifier.  Some ISPs are logging 
> CLID which goes partway towards what you are asking.

That's about as good as it gets.

> MAC isn't a fully reliable indicator either as pretty much every card in 
> use now has the ability to have its MAC address changed.

And CLI can be disabled. If you want to really know who is at the
other end you've got to use some decent authentication - relyinging
on CLI or MAC address is pointless.

> I don't know if the line is identified on an ADSL connection.

There is an ATM link layer for ADSL which implements a virtual
circuit much the same as a phone call. It has signalling which
includes the caller ID etc, which some ADSL providers use in so
called "bridge mode" in place of a PPP negotiation to determine
who is at the other end of the link.

Chris