[cisco-bba] IP DSLAM ( Fully Distributed BRAS)

John Edwards isplist at adam.com.au
Fri Aug 5 19:12:01 EDT 2005

Vusi Ndebele wrote:

> Up to now, I can’t find many examples of large deployments of fully 
> distributed BRAS within the DSLAM. In an IP world, surely this is the 
> realisation of a network engineer’s dream but few seem to have 
> implemented it. The industry seems divided on this. Some vendors 
> believe the Metro POP is as far out as you should push the BRAS.


The problem is that when you accept an all-in-one solution, you're 
accepting someone else's vision of what an IP DSLAM should be. DSLAMs 
are a volume product, which means that the margins are thin and 
manufacturers have little incentive to provide software updates long 
term, especially once they release a new product that obsoletes the 
model you have installed. You may also find that the vendors who are 
doing state-of-the-art xDSL connectivity treat IP as a poorly 
implemented afterthought. Once you have 30,000 ports installed and a 
competitor introduces a new feature, how are you going to upgrade? What 
if the features you were promised by the vendor don't work as 
advertised, or even worse, can't be realised due to a hardware limitation?

There's no reason why you can't re-create what you'd like by putting a 
smaller BRAS with the DSLAM at each site anyway. Moore's law is going to 
make it much more cost effective to forklift-upgrade a BRAS in the 
future than to re-joint those 30K copper pairs to the connector type 
required for the equivalent IP DSLAM.

John Edwards
(Who's fingers are still aching from installing and cabling hundreds of 
dslam ports yesterday, and is happy that they won't need to be 
re-installed anytime soon!)

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