It’s been quite an amusing afternoon at BT Central in Newgate Street. After the ITSPA council meeting I stayed to moderate the Technical Workshop which covered VONGA and Number Porting.

More on Number Porting anon but VONGA, or Voice over Next Generation Access, was an interesting session. BT is, as we all know, rolling out Fibre To The Cabinet and then Fibre To The Premises (anyone wanting the service please get in touch).

The FTTP product from Openreach is going to have an option to take voice services that will replicate WLR3 – the standard analogue line Plain Old Telephony Service or POTS.

There are I think several drivers for this within BT. Firstly BT either appears to be obligated to, or has decided to only provide fibre services to new Greenfield site builds rather than any copper based connectivity. They still however have an Universal Service Obligation to provide telephony services to anyone that want them.

Enter VONGA stage left. VONGA allows end users to plug an old fashioned telephone handset into an Analogue Telephone Adapter socket on their “broadband” router to make phone calls.

VONGA is also part of BT’s long term preparatory work before they turn off the old fashioned PSTN and move over to 21CN voice – 2020 at the earliest as reported here.

When I first heard of VONGA I kind of got excited. ITSPs around the country were asking all about it. In fact they were worried that BT might be trying to eat their still meagre lunch.

Don’t worry lads (and lasses). There is an alternative called CPCA that allows you to provide your own telephony services from the ATA sockets in the BT kit although it wasn’t totally clear to me whether anyone could do this completely independently of paying something to BT for the privilege. BT seems to think they are the only ones able to provide the PATS level service and point to a battery in the router that will keep the service alive for up to 4 hours in the event of a power cut (all subject to spec confirmation). Ofcom and most ITSPs would disagree here.

Despite what I’m sure are Openreach’s best efforts to corner the WLR3 futures market it will be possible for Communications Providers to sell users the FTTP connection and then sell their own services overlaid onto and through the Ethernet ports in the router – just like they do now. In fact this is effectively the naked DSL currently unavailable in the UK, albeit using turbo DSL.

VONGA does notionally provide Quality of Service for voice running over a separate VLAN tied to each ATA socket. However this QoS will also almost certainly be available to users just taking FTTP.

There are several disappointing facts associated with VONGA. Firstly trial dates stretch well into 2011 and then there is no firm date for production so this isn’t likely to happen before 2012.

Secondly VONGA, initially at least, strives only to replicate what is currently already there – so expect only boring old fashioned G711 voice services. This is a shame really considering that G711 will occupy only 100kbps or so out of the 100Mbps available over the fibre so could provide a higher quality product taking up just a little more bandwidth.

I think BT is boringly missing a trick by just trying to reinvent an old fashioned service but then again I realise that this is part of the long term goal to replicate and then remove the boring old 20CN network.

The third and final disappointing fact, which is more of an amusing one really, is the that VONGA uses SIP as a signalling protocol. SIP enables the internet’s version of old fashioned telephony but takes it on to another level by providing features such as Video. Presence and Instant Messaging.

SIP however doesn’t support all the legacy features of the PSTN – it’s moved on from there. You don’t need ringback for example if you can see when someone is off the phone.

The Alcatel Lucent SIP softswitch being used by BT (one of at least four different VoIP platforms being used across the BT empire) therefore doesn’t support all the features of the Plain Old Fashioned Telephone System.

This means that whilst you might expect a VoIP service to offer more than POTS in this case it actually offers less – POTS Lite if you like. Who’d have thought such a thing was possible!

Sorry about the continued abundance of acronyms!

PS we were sat in the pub after the meeting thinking up titles for this post. Kinda fonda VONGA didn’t sound true, VONGA Ponga was a bit childish so VONGA – POTS Lite got it.