In article ,
The Natural Philosopher writes:
On 27/08/13 08:41, dennis@home wrote:
On 26/08/2013 23:08, The Natural Philosopher wrote:
On 26/08/13 22:29, dennis@home wrote:
On 26/08/2013 20:22, Tim Streater wrote:
In article ,
(Andrew Gabriel) wrote:

In article ,
Tim Streater writes:
In article ,
The Natural Philosopher wrote:
How else can BT know where to vector the actual ATM conversation?
I would have expected that, with one end in my local exchange, the
other end on the ISP's router, BT would use their management
software to set up a VC between those points over their ATM
network,
and that would be it as far as their involvement was concerned.
However, giggling for "BT Radius Server" appears to indicate
that it
doesn't work like that; perhaps the simple approach doesn't scale.

It doesn't actually know who your ISP is until your router tries to
login.
If you reconfigure your router with the login details for another
person
using a different ISP (but also on BT wholesale), you will find
you can
login to their ISP on your line just like you normally log in to
yours.

So the ATM circuit is built on the fly? That would make some sense.


Its done at the IP layer.
The customers ATM circuit does not get as far as the ISP on the ADSL
services.
I think it does. The circuits are delivered via ATM to the ISP. Not
via Ethernet.

Just because the link to the ISP is over ATM doesn't mean subscribers
ATM circuits are presented at the ISP end.
They could be delivered via ethernet

Indeed they could, But I dont think they are in fact.

ISP gets an IP link over ATM (originally a multiple of 155Mbits/s,
but I think they're now a multiple of 622Mbits/s), and customer's
sessions are presented as L2TP sessions over that IP link (i.e. IP
nested in L2TP's UDP/IP). ISP never sees the customer's ATM session.

BT also have a service where they will actually terminate the
L2TP sessions and route the end-users traffic directly to the
internet for the ISP, but I don't know any ISP which uses that.
It wouldn't leave anything much for the ISP to do.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]