[nsp] DSL Architecture Question

[Chris Roberts]

Mikael Abrahamsson wrote:
>
> May I ask what your motivation in using a ATM dslam is? We have
> deployed dslams where we terminate the ATM in the dslam and the dslam
> has an ethernet uplink (basically the dslam gives us one customer per
> vlan) and we then terminate this in some kind of ethernet device
> which might have any kind of uplink (RBE like functionality but on
> vlan).
>
> We looked at ATM only dslams and just couldnt figure out what
> advantage it would give us.

A lot of ATM DSLAMs out there are dirt cheap, due to the lack of IP
termination within the platform. This is great if you already have an ATM
core and can central locate your BRAS function, but for new DSL installs
based on IP networks it's not great. However buying ATM DSLAMs with
integrated IP is expensive (normally around double the price of the DSLAM
for the IP termination cards, dependant on vendor), and a lot of the IP
based DSLAMs don't yet have the functionality afforded to you if you're
using a full IP implementation such as Cisco's with ATM backhaul (read: MPLS
termination, QoS, etc, etc). The other option is L2TP backhaul to a central
RAS, which a lot of the simpler IP based DSLAMs support, but L2TP has it's
own difficulties and nuances.

Cheers,
Chris.