Following the adoption of the Multi-Technology Mix, the company responsible for building the network – nbn™, has released an updated version of the Network Design Rules document which dictates how the NBN is designed across all technologies.
In the document, dated 30th June and released today to the public, the company outlines changes to the network planning process for the MTM. Below are some highlights:
NBN removes protected fibre paths
With the implementation of the MTM, the company has done away with the original “ring topology” in the distribution fibre network, which was designed for fault tolerance allowing at least two paths for data to flow to and from the end user in the case of damage to the fibre network.
nbn™ states that a “star DFN topology” will be used instead, citing cost efficiencies in construction:
The Star DFN topology is the default for the Fixed Access build (post-Multi Technology Mix) to achieve cost efficiencies in construction.
In addition to the shift to the star topology, by default, only a 12-fibre core sheath will be used to connect an NBN node in a NBN Copper Access environment. This may limit the company’s ability to swap out copper nodes for a passive fibre rollout in the future.
FTTN and FTTB won’t have an NTD, HFC will
The company’s updated network design rules also provides insights into the CPE (Customer Premises Equipment) for the new technologies being introduced into the network.
For customers on the Fibre to the Node (FTTN) or Fibre to the Basement (FTTB) networks, nbn™ will not provide the VDSL2 modem required to connect to the network:
A VDSL2 modem (provided by the Access Seeker or end user). This is on the customer side of the nbn™ network boundary and is not discussed further in this document.
However, NBN Co will provide an NTD for customers in the HFC footprint.
The HFC NTD terminates the incoming physical coax cable at the end-user premises and provides one User to Network Interface (UNI). The HFC NTD will have the following:
- 1 x coax interface
- 1 x UNI-Data interfaces
The HFC NTD has not yet been finalised and will be the subject of an RFP.
Unlike the NBN Fibre, NBN Fixed Wireless and NBN Satellite footprints, the HFC NTD is expected to only feature one data port and no voice ports.
NBN copper nodes to include 48, 192 and 384 variants
nbn™ has listed that DSLAMs with 48, 192 and 384 ports will be used in the FTTN and FTTB network, with “further DSLAM sizes, are currently under investigation”.
The company says they will prioritise interconnecting their network with the existing copper plant “directly into the pillar” where possible, or alternatively, inject the VDSL2 signals into existing or new downstream and upstream joints.
Each DSLAM will also be served by 4 point-to-point fibres, with at least 2 spares for migration and expansion purposes. Each fibre is configured to aggregate 1GE of traffic back to the newly introduced Access Aggregation Switch located at the Fibre Access Node site, typically housed at an existing Telstra exchange.
NBN Co’s updated Network Design Document can be found here.