[c-nsp] IP DSLAM ( Fully Distributed BRAS)

[Chris Roberts]

> List,
> 
> 
> 
> I wanted to get some views and experiences of the much touted 'IP DSLAM'.
> As
> far as I can tell, many of the DSLAMs on the market right now are more
> Ethernet DSLAMS effectively bridging with a bit of fancy snooping etc for
> multicast. I call an IP DSLAM a box that has encapsulates subscriber
> traffic
> into IP packets on the trunk interface. Products on the market include the
> Alcatel ISAM, Huawei MA5600, Lucent Stinger etc with their relevant 'BRAS/
> IP Services' module.
> 

The problem with going the IP to the DSLAM model is the lack of support from
the DSLAM vendors for much in the way of IP services. If you're using your
DSLAMs for any kind of corporate customer then your customers Cisco style
QoS, MPLS, Multilink, etc, etc at the termination point, and this
functionality just isn't even in the roadmap (or is a long way off) for half
of the DSLAM vendors at the moment, and their IP services are sorely
lacking. It's been a bugbear of mine for a while, having talked to
Lucent/Alcatel/Marconi heavily on this about 18 months ago. Maybe things
have changed since then, I've got out of that market...

They're great for home customers though that don't need triple-play or MPLS.
Maybe even where you need triple-play and can do it with basic IP QoS.

There are also huge cost implications for this - an ATM based DSLAM with
ATM/Ethernet backhaul is far far cheaper to deploy on a large scale than a
full-featured IP DSLAM. If you're looking small-scale or have deep pockets
you may be okay, but at least some of the vendors were looking at a factor
or 1.5 - 2x the price per unit with IP modules.

Cheers,
Chris.

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