Industry group the Communications Alliance is inviting comment on an aspect of Australia's NBN that often gets second billing next to high-speed Internet connectivity - namely telephony services.
Modelled on CommsAlliance's NBN Reference Model, the industry group has released a document that sets out proposed definitions for wholesale telephony service for providers on the Australia's planned fibre to the premises (FTTP) network.
While the new FTTP network represents a shift from older, copper-based connectivity, NBN Co has stated that support for legacy telephony services is being considered for it during the transition to full voice over Internet Protocol (VoIP) services.
This will be achieved through the use of Analogue Telephone/Terminal Adapters (ATAs) that are integrated in the Optical Network Terminator (ONT) installed at customers' premises. ATAs allow customers to connect existing telephones to the VoIP service running over NBN, which itself will provide the capability mainly through the Session Initiation Protocol (SIP) standard, but also the H.248 Real Time Protocol (RTP) one.
Using ATAs can provide a greater range of services than is available today, depending on retail providers' commercial offerings, but the document recognises that they are limited compared to full VoIP SIP devices connected directly to the network via Ethernet.
For instance, existing phone handsets do not support wideband and full-band codecs for an expanded audio range, with stereo and multi-channel capabilities. Instead, they are limited to voice the frequency range of 300 to 3,400Hz.
Integrating ATAs into ONTs is seen by the NBN Co as migratory step towards full VoIP telephony service.
However some providers such as Optus and Symbio Networks oppose the inclusion of ATAs for legacy phone service support, as they expect it would bump up capital and operational and capital expenditure and more generally go against the minimalist approach publicised widely by NBN Co.
Dr Leith Campbell, principal consultant at analyst firm Ovum disagrees. Campbell says ATAs are necessary.
"If the NBN is to fully replace today's customer access network, then standard telephony must be supported, for all those people who just want to plug their phone into a new socket," Campbell told iTnews.
According to Campbell, this means that the NBN's optical termination unit must include an ATA and the NBN must provide the necessary protocols and management interfaces to support telephony.
He also says that a "bare-bones" telephony service will probably not be sufficient, as in addition to fax machines, there are many specialist terminal devices that make use of today's telephone network.
"There will be important choices to be made by the NBN of what features it will eventually support," Campbell said.
According to the CA document, other existing PSTN features that may live on with the NBN are faxing, payphones and ISDN - the latter through emulation, as well as dial-up modem service for EFTPOS, security alarms and SMS on Fixed.
The draft paper on the proposed NBN phone service is available at the Communications Alliance website [PDF] format and the public comment period closes at 5pm AEST, Friday June 25.