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NGNs (21CN)

Next Generation Networks


What is a NGN?

What is 21CN?

What is the latest situation with the 21CN migrations?

Was the 21CN testing a waste of time?

How do I know if my equipment is at risk of failure on a 21CN?

What is happening with fibre connectivity?

BT fibre to the Cabinet update (FTTC)

BT fibre to the premises (FTTP)

Is the BSIA working with other Next Generation Network communication providers?

BSIA guidance documents

Commonly used terms and abbreviations


What is a Next Generation Network (NGN)?

A NGN is a broad term that describes the current evolution of communication infrastructure in the UK. The UK Government is actively supporting the need to provide “super fast” broadband access across the UK and has set targets for its roll out.

At the heart of this technology is an Internet Protocol (IP) based packet technology network. The use of this technology is enabling multiple services such as voice, Broadband, TV on demand and other value added services to the end-user.

NGNs are operated by communication providers (CPs), which include companies such as BT, Cable & Wireless, Talk Talk and Sky to name but a few. Whilst each of these CPs may operate their own network (or sometimes purchase services from each other) there is the need to interconnect to each other and equally important, have the ability to interface to the legacy network (the current TDM phone network used in the UK). The most well publicised NGN is  BT’s 21CN, which is explained below.


What is 21CN?

Back in 2006, BT announced it was to embark on a nationwide upgrade to its existing telephone network to turn it into a “next-generation network” (NGN). BT used the term “21CN” for this. Some of the key facts of 21CN are as follows:

  • The 21CN network is a "packet" based Internet Protocol (IP) network.
  • There will be some technical changes following migration to a NGN.
  • 21CN will provide a UK NGN platform for other communication providers to operate their services over the BT network.
  • The migration to 21CN will result in wide availability of high-speed broadband access, including a super fast ethernet service.

The 21CN “core” network has already been upgraded. This will enable the replacement of equipment in 5500 BT exchanges across the UK. Being a digital IP system, there will be some fundamental changes in the operation, which include delays in transmission of data and compatibility effects of interconnecting other NGN providers. Both of these can impact on security equipment as some transmitted alarm signals have a dependency on time between the communicating transmitter (the signaling device at the customer's premises) and the transceiver unit (the receiver at a monitoring centre).

Other communications providers are making similar changes to their networks so you may be affected even if you do not use BT.


What is the latest situation with the 21CN migrations?

The migration of voice & broadband lines to 21CN was planned to include circa 30 million PSTN / ISDN and 8 million broadband lines, however, following a strategic review of its NGN business, BT announced its intention to withdraw plans to mass migrate both PSTN and ISDN lines to 21CN. Migrations to 21CN will now only be based around customer demand and exchanges where equipment is reaching the end of its life.

Before abandoning the roll out, BT had completed its initial “Pathfinder” migration of approximately 65,000 PSTN lines in the Cardiff area to 21CN in Spring 2009. This remains the case today.

Whilst this change of strategy is relevant to the "voice" element of the migration (where the majority of communication devices operate), the broadband aspect has continued apace.

A statement from BT regarding the outcome of their strategic review can be downloaded by clicking here.


Was the 21CN testing a waste of time?

Absolutely not! It has paved the way for testing fibre connectivity and helped to model the characteristics of the evolving NGNs in the UK.

BSIA has worked closely with BT over the last few years, since the emergence of 21CN was made known to us. Through initial testing of security products on the “simulated” network, and then on a “live” 21CN network, we have been able to understand how the effects of this technology change can impact on equipment.

Through our manufacturers we produced a security equipment test plan, which provided a rigorous sequence of tests that covers the various signaling formats used in the Industry. The tests were conducted at the BT test facilities in Swansea, with specialist equipment provided by BT.

The BSIA 21CN test plan can be downloaded by clicking here.

Note: The BSIA Fast Format guide was reviewed as a result of the knowledge gained from testing 21CN. The updated version of this guide can be downloaded by clicking here.

All BSIA communications equipment manufacturers attended the BT facility in Swansea and tested their core products against the BSIA test plan. The results of these have been published on the BSIA website.

The 21CN test results can be downloaded by clicking here.

The test results focus on the main potential failure mode for 21CN, which is additional network delay. They also provide a 21CN compatibility test.

Through the testing we have conducted to date, and the knowledge we have gained through discussions with BT, Ofcom and other communication providers, we have been able to call on a wealth of experience and develop a risk based assessment of the impact of 21CN on security equipment. This assessment evaluates the likelihood of something happening and the consequence it delivers. The output of this assessment has enabled us to provide a clearer message to end-users, installers, monitoring centres and manufacturers. Various guides have been produced by the BSIA - click here for more information.

BSIA members have been briefed on the risk assessment outcome.


How do I know if my equipment is at risk of failure on a 21CN?

Reading the results on their own may not provide a straightforward answer to whether certain equipment is at risk, as there are two other factors that can affect the overall delay of alarm signals; these being the type of receiving equipment and the type of network on which it is transmitted. To assist with this, BSIA has also produced a web based “risk calculator” which allows you to enter the two fundamental values under consideration, those being the communicator delay and the receiver processing delay. Once these values are entered, a graphical representation is produced showing you the potential risk of failure on each of the known network routing configurations.

The web-based calculator is available by clicking here.

What is happening with fibre connectivity?

With the upgrading of the 21CN core network, BT is enabling fibre to the Cabinet (FTTC) and fibre to the premises (FTTP) through its exchanges. BT has accelerated its FTTC roll out (a service known as BT Infinity) which will enable faster broadband access to end-users, whilst maintaining the copper element of the voice network. A recent announcement(1) from BT suggests the company have exceeded their milestone to pass 10 million premises by the end of 2012 with wholesale fibre broadband. The coalition government also seeks to incentivise communications providers to deploy their networks to both rural and urban areas.

Fibre is not a new technology and its use is inevitable in today’s drive to provide faster communication access services and bandwidth hungry media services such as video streaming movies. Some of the larger communications providers are already deploying their fibre services across the UK, such as Virgin, Talk-Talk and Sky, now BT has also joined this race to offer its own fibre access solution to end-users.

A lot of terminology is used in the communications industry and buzz-words such as FTTC & FTTP are frequently used. Below is a simplistic view of the current fixed network environment in the UK:

Fig 1. Below: Simplistic overview of the fixed network environment in the UK

 Note: Fibre to the premises is also known as fibre to the home (FTTH)

There follows an explanation of these two key abbreviations to help explain how they “fit” with the fibre solutions being rolled out across the UK.

(1) BT Press release 10th May 2012 – DC12-137


BT fibre to the Cabinet update (FTTC)

BT Openreach has enabled over a fifth of its 5500 exchanges for Super-Fast Fibre Next Generation Access (NGA); this is on the back of their £2.5bn investment in upgrading its network. Further exchange upgrades are being planned.

Advice to installers remains as before, be vigilant; customers may change their phone provision without realizing the effect on their alarm system. Raising awareness to the customer of the potential failure that may occur if they choose an alternative network service is paramount to ensuring the alarm system continues to function correctly.

Compatibility testing carried out by BSIA on BT’s live FTTC network (tested at Muswell Hill in 2010) saw no issues for existing communications devices. However, be mindful that this was tested solely on BT’s network and does not take account of other communication providers network provision.


BT fibre to premises update (FTTP)

The enablement of FTTC includes access to Fibre to the premises (FTTP) services. BT has released details of housing developments (59 at the time of writing this update) that will currently benefit from this service. BTs “mixed economy” offering will also mean that in addition to greenfield sites, brownfield sites can also benefit from the fibre services; this “mixed” service would see both copper and fibre technologies in the same premise. The illustration below shows how the current access environment looks:

Fig 2. Below: Current fibre voice access environment architecture

BT retail has recently announced its intention to launch a voice over FTTP solution across the UK during 2012/13. Whilst not on the scale of 21CN, it provides an opportunity for BT to compete in this emerging market.

As with 21CN, BSIA had engaged with BT at an early stage of testing of their fibre access solution, and to that end, BSIA developed a FTTP test plan for use by manufacturers of communications equipment to test their products at a BT test facility in Milton Keynes. This testing, carried out over the Christmas period of 2011, was based around those of 21CN due to the similar technical characteristics of this type of network. The results of the tests from the various manufacturers are available to view on our web site

The BSIA FTTP test plan can be downloaded by clicking here.

The FTTP test results can be downloaded by clicking here.

NB. Whilst every effort has been made to ensure that the results are full and reliable, the BSIA cannot accept any liability for the accuracy of the results or responsibility for any reliance upon the results. The tests, which gave rise to the results were dependent upon British Telecoms technical equipment and were carried out by each contributing manufacturer themselves.


Is the BSIA working with other Next Generation Network communication providers?

BSIA continues to raise awareness of NGN and call-routing issues through its Regional and Technical meetings, along with seminars and events. We also offer a support service to our members who have or are now experiencing signalling failures of this nature.

We continue to develop our links with a communication industry forum called NGNuk, which has been established to provide communication providers and Ofcom with a central point of contact to address issues with NGN and NGA (Next Generation Access) across the UK. BSIA has contributed to this forum and is addressing the needs of our members, especially around fibre access, testing and network understanding. Members have received personalized presentations by NGNuk to raise awareness of the issues industry faces with the emergence of NGNs.

Following input to NGNuk, we were delighted to receive the NICC guidance document; NICC ND 1431: Guidance on CPE Compatibility on NGNs and NGAs. This long awaited document assists manufacturers in the design and operation of voice band detection & voice CPE and provides compatibility testing of such CPE against NGN and NGA networks.

BSIA is still seeking an answer to the maximum network delay expectations, which are not confirmed in the above document; a fundamental issue we have been campaigning to address over the past few years. 

BSIA had concluded some earlier testing with Sky on its Voice Broadband Network (SVBN), which is an IP technology based NGN. Whilst identifying an issue that affected digital communicators, testing revealed the problem and Sky reconfigured their software to resolve the issue. Whilst this is good news, it does highlight the problem with NGN providers changing their network designs, without consultation with industries like ours. On the positive side, Sky continue to involve BSIA in sample testing of communications equipment when they are about to launch new software upgrades to its SVBN.


BSIA guidance documents

The BSIA has produced guidance for ARCs, installers and manufacturers regarding 21CN and these are available to members of the BSIA on the BSIA members website.  We have also produced a "User Guide" which gives basic advice about the changes to the UK telephone system and how it may affect your burglar alarm.  This guide can be downloaded by clicking here.

Three further guides have been published for BSIA members

The basic advice for Installers BSIA form no. 272.

The basic advice to Manufacturers BSIA form no. 273.

The basic advice for Monitoring Centres BSIA form no. 274.

Members can download these by logging in via this link.


Commonly used terms and abbreviations

NGN - Next Generation Network – a term used to describe the evolving change in the UK’s telephone infrastructure. Principal concept is to ensure that all types of media such as voice, data, video etc can be transported on one platform. Such networks are built around IP (Internet Protocol) technology.

NGA – Next Generation Access – a term used to describe how services derived from a NGN will be accessed by the various communication providers such as BT, Sky etc. Access is based around optic fibre that gives a higher throughput compared to the services operated on the traditional copper network.

21CN – 21st Century Network – the name given to BTs upgrade programme for transforming their network infrastructure to a NGN based Internet Protocol platform.

Super-fast broadband – A service that will provide faster access speeds using fibre technology. Quoted speeds up to 100Mbps download and 30Mbps upload dependent on location and whether fibre is available to the premises.

Greenfield sites – Sites that have not been built on before. Often rural / Countryside.

Brownfield sites – Sites that have been built on before. Normally associated with urban areas.

CP – Communication Provider – A company or organization that transports information electronically such as voice, data and video etc. Examples are BT, Sky, Virgin, Talk-Talk.

TDM network – Time-Division Multiplexing network – A type of digital network traditionally used in the UK's telephone infrastructure. This is being replaced with the introduction of the NGN.

Mixed economy – Used in the context of telephone services being delivered across the UK. Mixed being the transport of services using either copper or fibre or both technologies at the same time.

OfCom – Office of Communications – The regulator of communication services for the UK appointed by the UK Government.

NICC guidance – National Interoperability Consultative Committee – A technical forum for the UK communications sector that develops interoperability standards for public communications networks and services in the UK.

PSTN – Public Switched Telephone Network – The telephone network currently used today connecting over 30 million customers in the UK. Using fixed line analogue technology.

ISDN – Integrated Services Digital Network – Means of carrying voice, data and other telephony services over the traditional telephone network.

FTTC – Fibre to the Cabinet – Extension of fibre technology direct to the street cabinets across the country to enable faster broadband service provision. BT Openreach is one of the major providers of this service.

FTTP – Fibre to the Premises – Extension of fibre direct to the premises to enable the highest access speeds.

FTTH – Fibre to the Home – Same as FTTP. The terminology “home” is used more commonly when talking to the residential market.


Last updated May 2012

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