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

[Neil J. McRae]

True IP DSLAMs still don't exist in my view. There is still
way too much ATM involved. What we are focused on are EFM based
DSLAMs that can deliver E.SHDSL [ethernet over DSL] and overlay
IP onto Ethernet frames. I call these EDSLAMS - Ethernet DSLAMS
We are testing in Belgium Actelis' solution which from a technology 
point of view is well ahead of the competition. We have also tested 
the Huawei device, ZTE - who are really pushing the IP DSLAM Concept
in the best way in my view, we use the ISAM already with ATM and 
Ethernet uplink and we looked at the Stinger [and another 20 odd
providers]. 

All of those boxes are still ATM devices in my view, and the EFM 
developments are a long way off, caused by standardisation issues.

I want to bin the ATM layer as soon as possible and run ethernet
but ATM does have some advantages, particularly around voice products
and wholesale products.

Regards,
Neil.


> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net 
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Vusi Ndebele
> Sent: 05 August 2005 21:03
> To: cisco-bba at puck.nether.net; cisco-nsp at puck.nether.net
> Subject: [c-nsp] IP DSLAM ( Fully Distributed BRAS)
> 
> 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. 
> 
> 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.
> 
>  
> 
> I'm looking for some real world telco/clec  views fro people 
> who have either evaluated or implemented this entirely 
> distributed BRAS architecture to support single, double or 
> triple play services. We are still running PPPoE on 
> subscriber CPE and though getting rid of PPP and L2TP 
> altogether in favor of a DHCP addressing mechanism is a sweet 
> dream, it's a few years away at best. 
> 
>  
> 
> In my scenario, I'd be looking for the 'BRAS Card' to be 
> terminating PPP sessions and performing L2TP LAC 
> functionality. Next stage would be to remove L2TP and 
> terminate PPP sessions at the DSLAM allowing local routing, 
> VPN's, Voice breakout etc., The final Phase would be to wave 
> goodbye to PPP and address all devices with DHCP using an IP 
> Helper on the BRAS card. (This PPP issue warrants a thread of its own)
> 
>  
> 
> I'd like to hear pro's and cons, a few of mine are listed below.
> 
>  
> 
> Pros:
> 
>  
> 
> 1.	IP Backhaul ( Easier to diagnose IP than PPPoE, Easier 
> and cheaper
> to create resilience and to load balance over multiple links)
> 2.	Better abilty to schedule based on IP CoS/ QoS 
> requirements at first
> congestion point (middle mile)
> 3.	Potentially better network availability vs huge 
> centralized BRAS at
> POP ( less customers affected by BRAS outage)
> 
> Cons: 
> 
>  
> 
> 1.                   Complex address management
> 
> 2.                   More devices in dynamic routing domain
> 
>  
> 
> Please let me know your views
> 
>  
> 
> Thanks
> 
>  
> 
> Vusi
> 
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