Analogue Private Circuits
BT strongly believes that packet-based 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/SDH technology. BT's 21CN is being built on an infrastructure that supports both innovative packet-switched NGN products as well as more traditional SDH products.
However, BT also recognises that some customers have applications that rely on certain characteristics of current TDM data services. BT respects these requirements and intends 21CN to meet them as far as is technically and commercially practicable. 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.
For circuits at speeds of 2Mbps and greater, we currently plan to meet this commitment by providing TDM data services on the SDH infrastructure of 21CN and our legacy network platforms. However, technology advances and we're actively researching alternative technologies that offer the potential to deliver comparable performance at lower cost.
Our plan remains to review the state of progress with our customers in Spring 2008, 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'll continue to provide service on our existing network until at least 2011 for all TDM circuits, including those under 2Mbps.
Outcome of recent 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 recent 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 was the following:
1. 64k ‘own exchange’ circuits (copper) will continue to be offered for the foreseeable future.
2. 64k and n64k TDM services will continue to be supported until at least Q1/2014 subject to demand, three years longer than previously stated. The additional three years will allow customers a longer period of time to migrate these services to suitable 21CN solutions.
3. 64k and n64k TDM replacement services will be supported on 21CN. More detail of the technical options is contained in the industry consultation document.
4. Line powered* and aggregated** 64k and n64k services will continue to be supported until Q1/2014 subject to demand, three years longer than previously stated. However, it is our intention to withdraw these features from service at the end of Q1/2014.
5. Once 64k and n64k replacement products are launched on 21CN, all new supply will be delivered from 21CN products, where available. Where 21CN products are not available, new supply will be offered from the existing product set.
6. Service providers have until the end of 2011 to set a date for migration of their circuits on to 21CN. If they do not do this a BT-led migration process will commence from January 2012, until end of Q1, 2014.
With specific regard to Leased Line updates on 21CN, please contact your service provider for further information.
*Line powered - where the customer located network terminating unit is powered from the BT serving exchange over the access copper cable
**Aggregated - where a number of 64kbit/s or nx64kbit/s circuit ends are combined, in BT’s network, into a single 2Mbps interface.