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HSCN CoIN migration guidance: maintaining interconnectivity

A description of community of interest networks (CoINs) and who uses them, guidance on maintaining interconnectivity during a CoIN migration and advice for both customers and consumer network service providers (CNSPs) when migrating a Split CoIN.

Community of interest networks (CoINs) are a private network for collaboration between regional consumers that have frequent and commonly shared business practices, applications and services. They are used extensively by the NHS where organisations with similar networking requirements have formed CoINs for regional collaboration. Participants in a CoIN can include health organisations, such as trusts, GPs or pharmacies, and care providers, including local authorities.

CoINs can include a number of network technologies, such as virtual routing and forwarding (VRF), virtual private networks (VPNs), local quality of service (QoS) configurations and managed voice and/or video services that are dedicated to the local community. Where a CoIN connects to the Transition Network (TN, formerly N3) it effectively connects using a gateway architecture approach, shown below.

Example of an existing managed CoIN using gateway architecture to connect branch sites to the Transition Network via primary site gateways

Diagram 1 - example of an existing managed CoIN using gateway architecture to connect branch sites to the Transition Network via primary site gateways.

Description diagram 1

Diagram 1 consists of a private Community of Interest Network (CoIN) connecting to the NHS Transition Wide Area Network via two geographically dispersed gateway routers. One gateway router is located at a primary site and the second gateway router is located at a secondary site. The CoIN also consists of a number of branch sites, which are all connected to each other and the primary and secondary sites in fully meshed network format.

Migrating a CoIN to HSCN

Migrating from an existing CoIN connected to the TN to a replacement CoIN provided by a HSCN Consumer Network Service Provider (CNSP) is a complex process. It requires accurate planning and execution in order to protect and preserve business continuity ,and avoid clinical risk for CoIN participants.

However, there are sufficient similarities in CoIN migrations to justify a standardised approach that prevents every CoIN migration from being considered a bespoke exercise. BT, as the Transition Network service provider, have documented a process and an approach that can be used to support IP Address management during CoIN migration, in Template G, one of the Transitional Assistance for Continuing Orders (TACO) migration templates detailed in the BT CNSP Information Pack

Template G does not cover scenarios where consumers require temporary CoIN interconnectivity during their migration. In the case of an existing BT CoiN BT TACO will implement this proposed interconnectivity approach, in conjunction with Template G, to support the movement of both aggregated and de-aggregated IP address ranges. If the CoIN is managed by a third party other than BT then the supplier should ensure that, if required, an interconnect is included in their CoIN migration plan.

CoIN migration proposal: interconnection

When temporary interconnectivity is required during migration of a CoIN to HSCN, sites are nominated as the new CoIN connectivity bridgehead sites during the migration planning phase with the new supplier. We recommend that the nominated sites are the existing bridgehead locations. As each individual consumer organisation migrates to their replacement CoIN, their new default route for all HSCN traffic becomes the new HSCN CNSP CoIN. The existing CoIN and the new CoIN remain interconnected to allow for inter-CoIN traffic only, using temporary circuits via the CoiN’s bridgehead routers.

If following this approach the consumer and CNSP should be aware of the following considerations:

  1. Temporary connectivity will be required between the existing CoiN and the replacement CoIN, for the duration of the migration. 
  2. Wherever assets can be reused for the temporary connectivity they should be. However, it may mean the provision of dedicated hardware and network circuits, to provide temporary connectivity, depending upon the replacement CoIN architecture.  
  3. The incumbent CoIN supplier, the replacement CoIN supplier and the CoIN organisations (or their overall technical representatives) need to work closely together to ensure a seamless transition.
  4. The incumbent CoIN supplier will retain ultimate control over traffic that is routed from the existing CoIN to the Transition Network (and beyond).
  5. The CNSP, as the new CoIN provider, inherit the responsibility for ensuring traffic takes the appropriate path for the replacement CoIN and the consumers connected to it. Take, for example, data traffic versus inter-CoIN traffic; will inter-CoIN traffic be routed via the inter-CoIN link and all other traffic routed via HSCN? 

Diagram 2: CoIN migration approach using router interconnects to maintain connectivity during migration. The transition Network CoIN remains connected to the HSCN CNSP CoIN via the Peering Exchange and via Primary Site routers.

Diagram 2 - CoIN migration approach using router interconnects to maintain connectivity during migration. The transition Network CoIN remains connected to the HSCN CNSP CoIN via the Peering Exchange and via Primary Site routers.   

Description of diagram 2

Diagram 2 consists of:

A - a private Community of Interest Network (CoIN) connecting to the NHS Transition Wide Area Network via two geographically dispersed gateway routers. One gateway router is located at a primary site and the second gateway router is located at a secondary site. The CoIN also consists of a number of branch sites, which are all connected to each other and the primary and secondary sites in fully meshed network format.  

B - a newly formed CoIN, provided by an alternative network supplier. The new CoIN is architecturally comparable to the existing CoIN, however; it is connected to the HSCN Wide Area Network.

During site migration, the branch sites on the original CoIN A and the branch sites on the replacement CoIN B communicate with each other via direct Network to Network Interfaces, which span each CoINs primary and secondary sites’ egress routers. All other network traffic, including internet and national applications network traffic traverses the Transition Wide Area Network and the HSCN Wide Area Network respectively.

Considerations for customers when migrating a Split CoIN

This section provides guidance for consumers and Consumer Network Service Providers (CNSPs) to ensure important controls and considerations are undertaken where sites/customer organisations from a TN CoIN have opted to use different CNSPs for their HSCN services.

Where different CNSPs are involved in the migration of a TN CoIN, this is known as a Split CoIN.

In a Split CoIN scenario, the lead customer organisation must provide overarching governance. This overarching governance must ensure:

  • stakeholders from affected organisations, the replacement CoIN suppliers, and the incumbent CoIN supplier are informed where a CoIN will be split during the migration to HSCN
  • overarching review of the migration approaches to ensure coherence across solutions and delivery plans
  • clarity on requirements to implement Interconnects, and/or co-ordinated firewall changes
  • agreement of the overall order of CNSP migrations to minimise migration risks
  • co-ordination with the replacement CoIN suppliers and the incumbent CoIN supplier to agree when temporary interconnects may be ceased

When multiple organisations share a site and each organisation is to be migrated to different CNSPs:

  • every CNSP, except the last to migrate, would need to provide their customer with a new IP address range - all devices belonging to their customer would need to be "re-IP'd"
  • the last CNSP to migrate would need to submit a TACO migration request for the legacy Service Identification Number (SIN) and would assume custodianship of all subnets associated with that legacy SIN.

The BT TACO team will provide guidance and support to the CNSPs on request.

Last edited: 29 October 2019 4:51 pm