Analogue Private Circuits
BT strongly believes that next generation network (NGN) technology offers new and exciting solutions for the breadth of our portfolio, including data products that have traditionally been served by Time Division Multiplexing TDM/Synchronous Digital Hierarchy (SDH) technology.
BT recognises that some customers have applications that rely on certain characteristics of current TDM data services. BT respects these requirements and intends products that use 21CN, wholly or in part, to meet them as far as is technically and commercially practicable. Hence BT's 21CN is being built on an infrastructure that supports both innovative packet-switched NGN products as well as more traditional non-deterministic SDH based products. At a minimum, BT is committed to continuing to provide the appropriate set of products that meet all relevant international standards for TDM data transmission, most particularly ETSI G.703.
We currently plan to meet this commitment by providing TDM data services (including sub-2Mbps) on our existing legacy network platforms or the SDH infrastructure of 21CN where obsolescence in elements of the existing legacy networks necessitates it.
We will continue to review the state of progress with our customers, including the practicalities of migration, before any long-term network design decisions with respect to these products and services are finalised. In any event, we have decided to extend the provision of service on our existing network from 2011 until at least Q1 2014 for all TDM circuits, including those under 2Mbps, provided there is sufficient customer demand to do so.
2007 TDM consultation exercise
BT conducted a feasibility study in 2007 on the strategy to provide Analogue Private Circuits on their 21st Century Network that addressed the following three analogue service categories:.
Analogue service falls into three categories:
- Copper own exchange
- A and B end of circuit are fed from the same exchange.
- Copper different exchange
- The A end of circuit is on one exchange, the B end is on a different exchange and the connection between them is copper and could be amplified.
- Analogue over digital
- A and B ends are fed from different exchanges and the connection between the exchanges uses the Digital Private Circuit Network (DPCN).
Each of these products provides different challenges and will require different solutions on 21CN. The current view is that the “copper own exchange” service will remain unaffected but that the “copper different exchange” and “analogue over digital” circuits will require some additional planning to migrate to 21CN.
The analogue feasibility study focused on reviewing the options for replacing the functionality of the existing platforms, assessing the manpower required for continued maintenance and the future availability of the necessary hardware
The results of this feasibility study were fed into BT’s Consult21 industry consultation on the future of TDM products which closed on 31 January 2008. This consultation focused specifically on the future of Partial Private Circuits (PPCs) rather than retail Leased Lines – however, the two are interconnected as service providers typically build retail Leased Lines using PPCs. Service providers had the opportunity to meet with BT and discuss these proposals and a number provided their comments by the end of the consultation period on 30 November 2007. The Energy Networks Association (ENA) also provided BT with a combined set of comments from utility companies.
The outcome of the consultation and the subsequent studies that followed as a result of feedback from customers and industry, as well as the implications for products and services will be published in due course.