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Business Applications Guidance

N3 overlays replacement guidance


Historically, the N3 service provider (BT) delivered a small number of business application services also known as “overlays” as a set of catalogue options for consumers. These comprised:

  1. N3 Voice - Hosted Voice Services (HVS) and Local Gateway Services (LGS)
  2. N3 Video Conferencing (VC) services
  3. N3 Remote Access Solution Virtual Private Network (VPN) tokens
  4. N3 Other Overlays - including routers, cards, ports, managed firewalls, WiFi and LANs 
  5. N3 Site to Site VPNs (Tunnels)

As a customer migrates from the N3 network to the HSCN each N3 contracted overlay service will require individual actions, which are explained in the following guidance.

For details of suppliers offering voice, video and remote access services over HSCN, including a table of the HSCN business application services offered by each supplier, their contact details and links to further details of the services they offer see HSCN business applications suppliers.

N3 Voice - Hosted Voice Services (HVS)

Existing catalogue items:

N3-4-2 - Voice Service – Hosted
N3-4-4 - HVS Small Site Service
N3-4-5 - Auto Attendant
N3-4-7 - N3 Voice Contact Centre
N3-4-11 - HVS Micro Site Service ADSL2+ capped at 1M
N3-4-98 - HVS on wires-only service
N3-4-99 - HVS on managed services

Action required:

These overlay services cannot migrate to a replacement third party HSCN suppliers service. They need to cease prior to the migration to HSCN.

N3 Voice - Local Gateway Services (LGS)

Existing catalogue items:

N3-4-1 - Voice Service - Local Gateway (10-60)
N3-4-10 - LGS SIP
N3-4-21 - LGS DPNSS (10-60 channels)
N3-4-97 - LGS on a managed COIN Voice Service - (10-60 channels)

Action required:

These overlay services cannot migrate to a replacement third party HSCN suppliers service. They need to cease prior to the migration to HSCN.

Existing catalogue items:

N3-13-1 - N3SP Managed Video Service
N3-13-2 - N3SP Managed Video Service Pay As You Go (PAYG)

Action required:

These overlay services cannot migrate to a replacement third party HSCN suppliers service. They need to cease prior to the migration to HSCN.

Existing catalogue items:

N3-12-11 - Single User Remote Access VPN Service for Non NHS
N3-12-12 - Standard Remote Access for NHS Customers. Token and s/ware -  Windows only
N3-12-13 - N3 Mobile Remote Access for NHS customers. Token and s/ware. Win/iPad/Android supported


Migration is required. The remote access service will continue to function until the token expires on the closure of the Transition Network, in August 2020.

When ordering N3 tokens you should be aware that the underlying legacy VPN service which the tokens rely on will cease in line with the closure of the Transition Network. This may be earlier than the end date of your services/token, depending on the start date and term of your contract. At this point you will need to procure a replacement service. Your existing supplier will be able to confirm the expiry date of your VPN token(s).

As of 31 October 2019 you are no longer able to order N3 catalogue services, including remote access solution VPN tokens, from BT, the N3 Service Provider. 

Other Overlays group 1

N3-05-97 - Bespoke COIN Other
N3-94-30 - Etherflow Data Centre Access Port
N3-98-47 - Additional card
N3-98-48 - Additional port
N3-98-75 - Router Only
N3-99-00 - IPN Thin Wrap
N3-CV-04 - CV additional dual Cisco switches

Action required:

These overlay services cannot migrate to a replacement third party HSCN suppliers service. They need to cease prior to the migration to HSCN.

Other Overlays group 2

N3-97-70 - iNet Managed WiFi
N3-97-71 - iNet Managed LAN
N3-97-72 - iNet Managed Firewall

Action required:

These services will be subject to a “Bespoke HSCN Migration Request” (Template F) which will be assessed in each case by the Transition Network TACO programme.

Existing catalogue items:

N3-12-2 - VPN Main With Single Branch
N3-12-3 - VPN Main With Between 2 & 5 Branches
N3-12-4 - Extended IP VPN    
N3-12-7 - 1 to 1 Main and Branch VPN
N3-12-8 - VPN Main With Between 2 & 5 Branches
N3-12-9 - 1 to 1 Main and Branch VPN
N3-12-10 - VPN Main 2-5 Tunnel
N3-95-02 - Non COIN to COIN VPN link
N3-99-90 - COIN custom VPN overlay service

Action required:

These overlay services cannot migrate to a replacement third party HSCN CNSP service. Your chosen HSCN supplier needs to address these site to site VPNs prior to migration to HSCN.

Upon award of the contract your HSCN supplier must perform detailed due-diligence of the existing VPN configurations and establish a process and technique to migrate the VPNs without impact to the customer.

Next steps for customers

Based on the actions described above on the various N3 overlays, if your existing N3 contracted overlays need to cease prior to migration of the N3 network to HSCN, you will have to decide if these overlay services are still used and still required.

If you establish that any of the services are not in use and no longer required, these should be formally ceased. This can be done by contacting the incumbent supplier directly.

If you establish that the services are required, they must be replaced with newly contracted services and once these services are operational, the N3 contracted services should be ceased.

Successful replacement of overlay services lies in careful and accurate definition of the Statement of Requirement (SoR)

Firstly, you should research your existing N3 overlays so you have a good understanding of what has to be replaced.

It will be useful to obtain usage and cost statistics from your existing management information (MI), bills or by approaching your BT N3 account manager. It will also be useful to obtain system diagrams and other applicable documentation which may have been created during the original system installation or as part of maintaining and operating the system.

The next step is to analyse whether it is applicable to replace the overlay service on a like-for-like basis or whether it is beneficial to alter the specification to best meet current and future needs. As replacing any system is unlikely to be pain free, this may be a good opportunity to enhance a particular system, either in functionality or in quantities. This is particularly evident in the case of video services, which could move from simple room-based end-points towards unified communication systems (for example, Skype for Business). Conversely, the replacement system could also be down-sized to meet current needs.

A detailed SoR document for the replacement overlays (the new Business Application Services) should then be constructed. This document should also include service-level agreement (SLA) requirements, maintenance coverage requirements and any other requirements that are essential for the business.

Rather than house equipment on customer premises, you should request services which are cloud based and can be used seamlessly over both the HSCN and the internet. We recommend that services should have minimal reliance on the HSCN Peering Exchange. Ideally, services should be network agnostic, so you can avoid being locked into using you chosen HSCN connectivity service provider for these additional services.

Voice and video services need to be fully interoperable with each other and integrate with the legacy BT N3 voice and video services during the transition period. You should choose services that are easy to use, are intuitive and provide a good end user experience.

The main routes to market for replacement N3 overlay services are, in order of preference:

  1. Network Services 2 (RM3808) - an existing Crown Commercial Services (CCS) framework.
  2. G-Cloud 11 Framework ID: RM1557.11.
  3. Existing agreements within NHSmail ‘Additional Services’ catalogue - for Skype for Business services (unified communications including video services).
  4. Organisation self-serve procurements - OJEU.


Network Services Framework RM3808 provides access to specialist suppliers who can deliver the services under the 13 individual lots.

The majority of replacement N3 overlay services can be found within the following RM3808 Lots

Lot 3 - Traditional telephony services

Voice services enabling local traditional telephony equipment to be connected to the public switched telephone network (PSTN). Includes traditional voice connectivity, voice call packages, SIP trunks, DDI ranges and CPS services. The scope of this lot also includes the on-boarding and management and maintenance of existing legacy equipment estates with support for transitioning to new solutions at end of life.

Lot 3 services are a likely replacement for N3 Voice – Local Gateway Services. Twenty-five suppliers currently offer Lot 3 services within the RM3808 framework

Lot 4 - inbound telephony services

Inbound call management services for established local call centre functions including non-geographical numbers. For example, 03xx, 05xx, 08xx and 09xx numbers.

Lot 4 services are a likely replacement for N3 Voice – Local Gateway Services. Twenty-five suppliers currently offer Lot 4 services within the RM3808 framework

Lot  5 - IP telephony services

End-to-end IP telephony services with the ability to connect to the PSTN. The solutions under this lot are strictly IP based and include voice call packages, Direct Dialling In (DDI) ranges, messaging services, contact-centre functionality, speech recognition software, automated call distributions, intelligent voice response and specialist administrative and reporting tools.

Lot 5 services are a likely replacement for N3 Voice – Hosted Voice Services (HVS). Thirty-six suppliers currently offer Lot 5 services within the RM3808 framework 

Lot 8 - Video conferencing services

Traditional and IP based conferencing services and the provision of all elements of a complete solution. This lot includes consultancy and training services, software management tools, call recording, analysis tools, peripheral equipment and transcribing and translation services.

Lot 8 services are a likely replacement for N3 Video conferencing services. Twenty-five suppliers currently offer Lot 8 services within the RM3808 framework.

Lot 9 - Audio conferencing services

Includes call recording, playback, analysis tools, the ability to reserve and pre-book, coded access references, peripheral equipment, software, management tools, security access products, collaboration tools, transcribing and translation services.

Lot 9 services are a likely replacement for N3 Audio conferencing services. Twenty-four suppliers currently offer Lot 9 services within the RM3808 framework.

Lot 10 - Unified communications

The provision of integrated communications solutions to provide a consistent user interface across a range of end-user devices. This lot incorporates components from lots 5, 6, 8 and 9.

Lot 10 services are a likely replacement or enhancement for combined N3 Voice and Video conferencing services. Fourty-three suppliers currently offer Lot 10 services within the RM3808 framework.

A full list of lots, available suppliers and their contact details can be found in the 'Documents' section of the RM3808 webpage or downloaded here. This can be used to filter by the relevant lot(s) you require.

RM3808 Call-off procedures

Network Services 2 (RM3808) provides three options for call off procedures:

  1. Direct award
  2. Further competition
  3. Aggregation

Direct award

Direct award is generally used when buying standard catalogue items from the Government Government eMarketplace. Using this eMarketplace, customers can browse Service Offers (SOs) published by Suppliers across the 13 lots.

Direct award is available on all lots of the agreement. Service Offers can be found on the Government eMarketplace. Access to the Government eMarketplace involves pre-registration of individuals within an organisation. Please note, the organisation’s Data Universal Numbering System (DUNS) number - a nine-digit number unique to your company - is required for this registration process.

Once logged on to the Government eMarketplace site, the catalogue is available under ‘Shopping’, then the ‘Marketplace’ tab. Search for RM3808. All catalogue items are shown, so apply filters (Lot 3 for example) to narrow results down.

Call off contracts can be awarded with the Direct Award Order Form and guidance on Direct Award can be found in the CCS document Buyer guidance to direct award, both documents can be found in the 'Documents' section of the RM3808 webpage.

CCS have advised that it is possible to invite suppliers to add new catalogue items to the Direct Award Catalogue should a requirement exist which is not matched by existing catalogue items (for example, where a product is a good match to the requirement but the standard support service is inadequate).

In order to invite suppliers to add a new catalogue item to the Direct Award Catalogue, fully complete a Request for information (RFI) Template under the Network Services 2 Agreement (RM3808) and email this to all suppliers in the appropriate lot. Complete the template with as much information about your requirement as possible. In the event of your requirement spanning more than 1 lot, this could be managed as a cross lot process. Where using cross lot, remember to invite only those suppliers common to both lots to respond. This might be useful if you are seeking to procure connectivity and overlay services together which can be achieved through RM3808.

The end result could be a new catalogue item which exactly meets a customer’s needs, and which can be procured via direct award.

Direct award scoring templates, either a Direct Award Desktop Evaluation - Price and Non-price or Direct Award Desktop Evaluation - Price Only, should be completed and maintained as part of the procurement process.

Further competition

Further competition can be used where you need suppliers to develop proposals or solutions to meet your statement of requirements and where you therefore need to run a competition under the framework. 

Buyers are able to refine the Public Sector Contract Call-Off terms for a Further Competition, provided this is done in accordance with the Public Contract Regulations, thus giving more flexibility when defining the Statement of Requirements. 

Further Competition is also the only route that enables you, the Buyer, to add Call-Off Special Terms to the Call-Off Contract. Both the above flexing to the core RM3808 terms, should be approached with caution as adding further requirements can limit the likely responses to your competition. 

Completing a Further Competition also gives you the option to run an eAuction or a multi-stage competition to identify the most economically advantageous tender. This option is not available via direct award.

Before you start the Further Competition process, we recommend that you undertake pre-market engagement, ensuring you engage with ALL Suppliers on your chosen Lot (or suppliers common to both/all lots if running a cross-lot procurement). This will give you the opportunity to ask questions to help refine your requirements. All engagement activities must be fair, transparent and open.

For more detail please see the CCS documents Further Competition Order Form and Buyers guide to Further Competition, both documents can be found in the 'Documents' section of the RM3808 webpage.


CCS develops and runs aggregated competitions (including the use of e-Auctions) for Buyers on a regular basis throughout the year. By aggregating demand, standardising specifications and running eAuctions, CCS regularly achieves material savings on a variety of requirements. A case study is available on the NHS saving an average of 74% through a CCS-run HSCN aggregation.

CCS provides a managed Further Competition service for Buyers who have common purchasing needs for products and services. By aggregating demand, CCS runs the procurement process on behalf of Buyers. Benefits and results:

  • Buyers can achieve increased savings based on committed aggregated volumes;
  • Simplification of the process leads to reduced procurement costs for the Buyer and reduced bidding costs for the Supplier;
  • Aggregation reduces fragmented spend;
  • Potential for standardisation to leverage greater savings;
  • Adoption and consistent application of best practices including the use of standard documentation sets; mitigating risks and issues; and
  • Support and guidance to Buyers throughout the process, conducting Further Competitions at no cost to the Buyer.

Aggregation Activities and Timelines:

  • CCS can run both generic (products and/or services suitable for multiple Buyers across multiple sectors) and sector specific (products and/or services suitable for multiple Buyers in a specific sector) aggregated competitions where there is a demand for common products and/or services.
  • Contact CCS via to explore opportunities for aggregation under RM3808. To enable prompt consideration please mark your request “NS2 aggregation”.

Full details on all CCS current and future aggregation opportunities along with recent aggregation case studies can be found on the CCS website.

Public sector organisations can use the Digital Marketplace “Cloud hosting, software and support” section to find suppliers of replacement overlay technologies. This is one of three frameworks (agreements between government and suppliers) in the Digital Marketplace.

The G-Cloud buyers' guide describes how to identify and buy cloud services on the Digital Marketplace. We recommend that the on-line guide is studied in detail.

In summary the guide covers the following steps:

1. Write a list of your requirements and get approval to buy what you need

You can also talk to suppliers before you start to help you refine your requirements and use early market engagement to help you write clearer requirements.

Please see G-Cloud Guidance - Talking to suppliers before you buy Digital Marketplace services

2. Search for services and save your search

In the Digital Marketplace “Cloud hosting, software and support” section search for services using keywords and filters. Please note that you have to create an individual Digital Marketplace account in order to save searches and buy.

You can save your search at any time - sign in to your Digital Marketplace account to see a list of your saved searches.

There are various tips for searching, but typical words which describe N3 replacement overlay services are a good starting point (meaning: telephony, voice, SIP, video, remote access, token, secure remote access). Searches can also be made for known suppliers or known products.

3. Refine your saved search using the filters

4. End your search

5. Download your search results, review and compare services

6. Choose your service, award and sign the contract (or ‘call-off’)

Single supplier - If only one supplier meets your requirements, you can award the contract to them without any further steps.

Multiple suppliers - There will usually be a number of services on your shortlist. You must choose the service with the most economically advantageous tender (MEAT).

For a MEAT-based assessment, you must use the criteria in the following table, but you can decide what detailed characteristics you use and how you weight them.

Criteria number

Award criteria


Whole life cost: cost effectiveness, price and running costs


Technical merit and functional fit: coverage, network capacity and performance as specified in relevant service levels


After-sales service management: helpdesk, account management function and assurance of supply of a range of services


Non-functional characteristics

Your assessment of suppliers should always be as fair and as transparent as possible. The final choice should be based on best fit rather than ruling out suppliers that don’t meet either your current contract or an ideal set of terms. You shouldn’t unfairly exclude any services without referring back to your project requirements.

You can use the spreadsheet of your search results to help record your decisions.


The buyer and supplier must both sign a copy of the contract before the service can be used. The maximum length of a G-Cloud contract is normally 24 months. You can extend a contract by 1 year and then a further year but the digital and IT spend controls team will have to approve it first.

7. Publish the contract on Contracts Finder

You must publish details of all completed contracts on Contracts Finder. You’ll need to sign in to your account first. If you don’t have an account, you’ll need to register as a buyer on Contracts Finder.

8. Complete the Customer Benefits Record form

You must fill in the CCS G-Cloud Customer Benefits Record form every time you enter into a contract. Email a copy to

A replacement or enhancement for combined N3 Voice and Video Conferencing services could be a unified communications and collaboration (UC&C) product, such as Microsoft Teams. Whilst these services are widely available through both the RM1045 and G-Cloud frameworks they are also available from NHSmail.

Microsoft Teams provides secure collaboration capabilities to connect your users between groups, organisations and locations. The service is accessible via a mobile and desktop client. Teams Meetings can also be joined via web browsers.

Further information can be found under the "About NHSmail" section on the NHSmail website. There are also materials on using Microsoft Teams and the different capabilities.

Last edited: 23 November 2020 1:16 pm