Comms Alliance - Architecture Whitepaper Response
Contents
Introduction 3
Meeting the future bandwidth demands of NBN 3
Re-Use of existing infrastructure is critical 5
Robustness of the Transport Network 6
Summary 6
Introduction
Nortel congratulate the Communications Alliance on the release of its NBN Reference Architecture whitepaper and believe the publication will facilitate extensive discussion around the NBN, providing a vision for the optimal NBN architecture.
Nortel aligns with the proposed architecture framework for NBN described in this whitepaper and agree with the functional and service domains put forward in Figure 1 – Broadband network Architecture Vision (page 3). However, we are of the opinion that to date there has not been enough debate or discussion of the Aggregation and Transport domain and as this is an area of particular strength and expertise for Nortel. This response will focus on this portion of the architecture.
Nortel agree with the function of the Aggregation and Transport Domain, described in Sections 3.1.3 (FTTP Access), 4.1.1.3 and 4.2.1.3 (Wireless/Satellite) and that the predominant Layer 2 technology for NBN will be Ethernet due to its ubiquity, simplicity and low cost per bit transport.
In addition to the aggregation of Ethernet based traffic, the function of this domain is to provide highly resilient transport of the aggregated traffic from local points-of-presence to larger, high density points-of-presence across metro, regional or national infrastructure. This resiliency and transport function needs to be performed in two layers:
- Layer 0, with DWDM and
- Layer 1, with OTN (Optical Transport Network) encapsulation
As the transport from the Access domain to the Service Edge & Core domain will be fibre-based, the above technologies will allow for high capacity, standards based multiplexing of traffic. DWDM will allow for multiple wavelengths to be multiplexed onto the same fibre, thereby increasing the capacity of the transport network while minimising the consumption of fibre. OTN provides a carrier-grade encapsulation of Ethernet-based services, allowing for the most efficient transport of services offered by NBN. The combination of DWDM and OTN switching and protection mechanisms ensures that the Aggregation and Transport domain will provide the required service performance with the highest availability, agility, lowest complexity and consistent network methodology across the NBN metro, regional and national network.
The below sections provide comments specifically around the Aggregation and Transport Domain.
Meeting the future bandwidth demands of NBN
The NBN has a unique opportunity to design and build the NBN network with best-of-breed technologies that will provide the most scalable and flexible solution in anticipation of massive growth in transport capacity demand. It is clear that only end-to-end fibre based technologies will provide the capacities likely to be required by the future digital economy.
The network must not only be able to cater for immediate bandwidth demands of the NBN but also for a suite of new services, most of which are not yet even envisaged. Thus it is important that the technologies deployed for the NBN on day 1 are capable of expanding to provide enough capacity to cater for the unpredictable requirements of the future ‘Digital Economy’. A wise choice for technology investment in the initial deployment will ensure that the network will scale for all likely future demands. In the access network only a PON based solution for FTTP access will provide this.
However, there has been little focus provided on the requirements of the transport domain for NBN. This is a crucial aspect of the NBN, especially when considering the scalability of the entire network and availability of services to end users.
The importance of the transport network cannot be overestimated. The transport architecture must be able to support the massive traffic flows to and from the Access domain, in orders of magnitude not experienced in Australia previously. To this end, Nortel has conducted a detailed bandwidth modelling exercise to determine the impact on the transport domain due to the services that are to be provided by NBN.
Figure 1 – Bandwidth modelling
The bandwidth study has shown that for the majority of metro and long haul links in Australia, when services with the attributes that have been stated publically are deployed, traffic in the order Terabits per second is expected. This unprecedented level of bandwidth cannot be met with the current DWDM technologies deployed in Australia.
In order to build a future-proof FTTP network, the capacities of the transport networks will have to be upgraded beyond the 10Gbps based systems deployed today. Without an increase in capacity, the transport domain becomes a critical bottleneck and an access network delivering 100Mbps to users (stated aim of NBN) will be not be possible, unless the transport domain is also upgraded.
Technologies do exist that can leverage the existing fibre and 10G based DWDM line systems to support 40Gbps and 100Gbps wavelengths. Nortel’s analysis suggests that 40/100Gbps based DWDM systems should be deployed, rather than 10G based systems, to ensure sufficient capacity is available in the future when the uptake of more bandwidth intensive applications increases.
A 100Gbps based system will provide up to 8.8Tbps of capacity (based on an 88 wavelength DWDM system) and based on Nortel’s bandwidth modelling, will be required to provide the predicted future bandwidth requirements for the NBN Aggregation and Transport domain.
Re-Use of existing infrastructure is critical
It is important to note the selection of technology used to deploy 40/100G systems plays a crucial role in determining the viability of high-speed transport networks for NBN. When selecting a 40/100G DWDM technology, of most importance is the ability for the NBN to utilise the fibre already in the ground today for 40/100G services, including all the very old fibre widely many believe to be unusable for NBN. This will eliminate the need to rollout thousands of kilometers of new fibre in backhaul networks providing huge capex/opex savings while also significantly reducing the time to bring the required backhaul capacity online.
It is also possible to use the DWDM line systems (upgraded with 40/100G wavelengths) that already exist along all major routes today. As technologies have been developed which allow a 40/100G wavelength to look like 10G wavelengths to the existing amplifiers line systems, the opportunity exists to extend the life of these assets into the foreseeable future for NBN.
This will not only provide significant capex savings in not having to duplicate these long haul systems over thousands of kilometers, but again will also provide significant time savings in not having to duplicate and expand the existing facilities along each route.
It must be noted that the real cost of these networks is in the provision and/or expansion of the amplifier enclosures at approximately every 75km from Cairns to Perth and everywhere in between. This would include the provision of new facilities, or at least the expansion of existing facilities, power and air-con upgrades, site acquisition, right of way access, etc at every site. Realistically this will introduce a multiple year delay to the project.
However, with careful selection of the technology selected it is possible to re-use most of the existing fibre and facilities infrastructure without the need to upgrade all the existing amplifier enclosure sites. This represents a massive saving to NBN in terms of capex, opex, project delay, resources and will allow the turn up of NBN backhaul capacities in a very short timeframe.
Robustness of the Transport Network
The Resiliency of the transport network, whether in Metro, Regional or National, will be a key factor in terms of the performance and user satisfaction of the NBN services.
The transport technology and architecture solution will improve robustness by eliminating components and simplifying networks, while supporting significantly increased network capacity (both line rates and nodal throughputs), and network optimisation through sub-wavelength grooming and packet transport functionality
To ensure robustness, the network architecture should support:
· Elimination of network components such as Dispersion Compensation Modules (DCMs) - Wavelength re-route via meshed optical ROADMs is significantly hampered by DCMs in the network, as not all possible wavelength routes are suitably “tuned” for each route.
· Minimised regeneration points in the network – The more regeneration in the network, the less reliable and more complex each service will be.
· Allow expansion of the optical network without major redesign – New sites added to the network should not impact on existing services, requiring flexibility such as multi-way branching ROADM at the network junction points without regeneration.
· Control Plane control for each layer: WDM & OTN - simplify network operation through automated network path and service provisioning. This makes trouble shooting problems more accurate and speedier. The network can be rapidly reconfigured providing agility for the introduction of new services. Just as importantly a Layer 0 and Layer 1 control plane will allow for automatic service restoration in the event of fibre breaks.
Summary
Nortel closely aligns with the vision outlined by the Communications Alliance and have conducted extensive analysis of the required backhaul NBN capacities that confirms the current generation of 10G technologies will not be able to cope with the future bandwidth requirements of the NBN enabled ‘Digital Economy’.
Nortel propose that not only will the next generation of 40/100G DWDM technologies be required to deliver the required backhaul bandwidth capacity but are commercially available in the timeframe suitable for NBN deployment.
Also, of the most critical nature to the NBN is the use of 40/100G technologies that will allow NBN to re-use the telecoms infrastructure already existing today (fibre, 10G based DWDM long haul line systems, facilities, etc). Technologies (DP-QPSK 40/100G DWDM, as endorsed by the Optical Interworking Forum) do exist today that will allow NBN to re-use this critical infrastructure and realise massive savings in terms of capex, opex, deployment resources as well reducing the time to market of essential NBN backhaul capacity by years.
This will allow rapid deployment of service to the end user in the most cost effective manner.
Commercial in Confidence