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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 Services

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.

N3 Video Conferencing Services

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.

N3 Remote Access Solution VPNs (Tokens)

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. 

N3 Other Overlays (routers, cards, ports, managed firewalls, WiFi and LANs)

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.

N3 Site to Site VPNs (Tunnels) 

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.

Main routes to market for overlay replacements

The main routes to market for replacement N3 overlay services are:

  1. Network Services Framework Contract ID: RM3808 (an existing Crown Commercial Services (CCS) procurement 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 Contract ID: RM3808

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 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 RM3808 ‘Products and Suppliers'.

RM3808 Call-off procedures

The Network Services Framework Contract ID: RM3808 provides three options for call off procedures:

  1. Direct award
  2. Short form further competition
  3. General further competition

Direct award

Direct award is generally used when buying standard catalogue items as described within the Government eMarketplace, with their Mandatory Service Offers (MSO) and Standard Service Offers (SSO) from the chosen supplier.

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.

Guidance on completing this form can be found in the CCS document How to complete a direct award order form and also, the CCS document Direct award and the short form further competition call off terms.

All CCS documents are also available to download directly from the ‘documents tab’ within the CCS RM3808 reference website and there may be more recent versions than extracted versions shown here.

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 services 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 Agreement (RM1045)  and email this to all suppliers in the lot of choice. Complete the template with as much information about your requirement as possible.

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 Scoring Template - Price and Non-price or Direct Award Scoring Template - Price Only, should be completed and maintained as part of the procurement process.

Short form further competition

Short form further competition is suitable where you do not want to amend call off terms and your requirement can be met through one lot of the agreement. This is generally for requirements which cannot be met by direct award, even after submitting an RFI to request a new catalogue item and you want to receive a quotation from a number of the approved suppliers in the framework.

Please see the CCS document Short Form Further Competition Order Form and for guidance How to complete a Short form further competition order form and the Direct Award and Short Form Further Competition Call Off Terms.

The Lot 3 SFFC Requirements Template must be completed to fully describe the Lot 3 requirement.

Should you need to request information in advance of submitting the Requirements Template, complete an RFI Template under the Network Services Agreement (RM3808) and email this to all suppliers in the lot of choice. Complete the template with as much information about your requirement as possible.

General further competition

General further competition offers maximum flexibility and the ability to run cross-lot competitions. The General Further Competition Order Form and ‘template call off terms’ should be used for this procurement route.

General further competition is generally used when your requirement may be from more than one lot, or is outside standard catalogue offer of direct award, and you want to receive a proposal from a number of the approved suppliers in the framework.

General further competition under RM1045 is a request for proposal (RFP) process.

For guidance please see the CCS document How to complete a ‘General further Competition form order form.

Should you require further information in advance of submitting the Order Form, complete an RFI Template under the Network Services Agreement (RM3808) and email this to all suppliers in the lot(s) of choice. Complete the template with as much information about your requirement as possible.

A useful comparison sheet for the three Network Services RM1045 procurement options is available - RM3808 Comparison of procurement options.

Some practical advice is that, once you have developed your detailed Statement of Requirement for your replacement overlay service(s), contact one or more of the suppliers who offer these services within the RM1045 framework to discuss your needs and how they could deliver your service(s) within the RM1045 framework. All suppliers will offer a free pre-sales service and would value obtaining a better understanding of your requirements.

G-Cloud - The government Digital Marketplace

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

Existing agreements within NHSmail ‘Additional Services’ catalogue - for Skype for Business services (unified communications including video services)

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

Skype for Business provides secure collaboration capabilities to connect your users between teams, organisations and locations. The service is accessible via the Skype for Business mobile and desktop applications. Skype for Business meetings can also be accessed via web browsers.

The NHSmail service offers core (free to NHS organisations) and top-up (funded by NHS organisations) features. The illustration below outlines the features:

Core and additional (top-up) services within NHSmail provided by Skype for Business

The feature set can be built up depending on the requirements of your users; for example, a user could be offered Instant Messaging and Presence only or with Instant Messaging and Presence plus Audio and Video Conferencing.

A full outline of the process is available in the NHSmail Skype for Business On-boarding Process guide.

Current NHSMail Skype for Business service pricing:

  1. Instant Messaging and Presence – no charge
  2. Peer-to-peer audio/video calling and web conferencing – £1.03 per user per month
  3. Skype for Business server access licensing – £0.55 per user per month
  4. Dial-in Conferencing (PSTN Conferencing) – £0.16 per connection per minute

The attached documents support the process for the organisation:

SFB1 - NHSmail SfB service description

SFB2 - NHSmail SfB Readiness Sign-Off

SFB3 - NHSmail top-up order form

Further information can be found on the About NHSmail page under Additional Services.

To call-off the services, such as audio/video conferencing and to get the process started, each organisation will need to have signed a Top-up Service Agreement. A Top-up Service Agreement does not commit the organisation to buy anything, but enables you to. After that, an organisation will need to raise the appropriate purchase order for the services.

A top-up Service Agreement can be sent to the organisation as soon as the following information is provided:

  1. Organisation contact, company name and address
  2. Invoicing contact and address
  3. VAT number

For more information on top-up and additional services, please contact

There are also materials on Skype for Business available on the NHSmail support site and the Skype for Business Learning Series page.

Please also see the demo and perspectives videos.

Organisation self-serve procurements - OJEU

Organisations may include overlay replacements as requirements in self-managed OJEU-based procurements.

Please follow the general advice above to generate a comprehensive Statement of Requirement before embarking on a self-managed OJEU-based procurement.

Last edited: 27 February 2020 12:39 pm