IP Technical question

[Clive D.W. Feather]

Roland Perry said:
> (This probably answers the OP's enquiry, in the sense that traceability 
> to the accountholder is preserved, but not necessarily to the premises; 
> and to impersonate him as that accountholder someone needs to steal his 
> password, it's not just a case of getting physical access to some 
> suitable copper).

Right.

> Secondly, if (say) I take my router round to my mum's house and plug it 
> in, will I get the specified line speed for *my* username/password, or 
> inherit the speed for *her* username/password (nailed into the physical 
> connection somehow).

There are two limitations involved.

(1) The DSLAM and modem will negotiate a speed. This is based on both line
characteristics (error rate traded off against speed) and on the profile
loaded into the DSLAM. So if there's a "max 4Mb" profile loaded in, they
won't negotiate over 4Mb no matter what happens.

(2) The point where the ISP breaks out the separate connection - either the
LNS or LAC (and they may be in the same box) connected to the BT Central - 
will be able to limit the number of bytes sent to the line, as with any
other kind of rate limiting done in a router. This will affect downstream
only.

I believe that the DLSAM profile is set by the ISP and then fiddled by BT.
This stuff was discussed on demon.service a year or so ago - you could
investigate your favourite archive.

-- 
Clive D.W. Feather     | If you lie to the compiler,
clive@davros.org       | it will get its revenge.
http://www.davros.org  |   - Henry Spencer