[LINK] FTTN architecture

David Lochrin dlochrin at d2.net.au
Thu Feb 4 11:52:32 AEDT 2016


This thread follows on from "NBN backup service"...

On 2016-02-02 12:14 Paul Brooks wrote:

> No - call routing and handling will be done by the ISP's softswitch, likely to be located in the nearest capital city - I doubt there will be any voice-handling infrastructure in a node or POI, just effectively an Ethernet tunnel between NTU analog port and softswitch through the backhaul-POI-NNI-CVC-AVC-NTU chain.

My understanding is that an ISP must have a connection to every POI which services an area containing their customers.  A POI services a "connectivity service area" or CSA and all communication within a CSA is done at OSI level-2, with ADSL / VDSL between the nodes & users.

So someone with existing ADSL & VoIP services doesn't need to change anything much when they migrate to an FTTN-based NBN service except that they'd have to configure a properly allocated VoIP telephone number for communication with other telephone users on the national network, and perhaps some other minor configuration changes.

But what do traditional POTS users do when the local NBN network is fully cutover and the exchange effectively closes down?  Will they each be issued with an NTU, or do the kerbside nodes contain analogue signal converters?

An ISP which doesn't connect to all 121 or so POIs must have a connection to a service provider which can route voice calls to / from users in those CSAs.  So how does an ISP decide how to route a call when the called number may be with them, with a user on a different ISP in the same CSA, or with a user in a different CSA to which the ISP has direct access, or another CSA altogether?

Is there some sort of online directory which maps telephone number, CSA, ISP, and level-2 address?  Who maintains it, NBNCo?

The more I think about this the more questions arise.  For example, the potential for maintenance problems and "finger pointing" seems quite high.  And it may be difficult to define enforceable service standards.

Or have I got the bull by the tail?

David L.



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