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N3 Network Overview

N3 is a Wide Area IP Network (WAN), connecting many different sites across the NHS within England & Scotland. It also connects to other networks via Gateways, notably to the Internet via the Internet Gateway.

Below is an overview diagram of the N3 network, the N3 users and the other networks that connect to it. It shows N3 conceptually rather than exact connections. For instance there are many PoPs (Points of Presence) and several gateways, some of which actually connect via PoPs.

Network Overview

N3 is based on 58 Access PoPs in England and 4 in Scotland. They are the local points where most end-user access ("Catalogue") services are connected to N3. They give the network its reach and also make it easier to use different local access service suppliers. There are also two dedicated DSL Access PoPs in England and 2 in Scotland, to aggregate DSL-based services.

In 2010 the core of the N3 network migrated from using Multi-Protocol Label Switching (MPLS) services to a core based on high-speed Ethernet services from Virgin Media and BT (Etherflow). This effectively doubled the England network core capacity and increased the core capacity several times in Scotland.

At the time of writing the GP Next Generation Access (NGA) project has just begun. Over several months this will significantly upgrade the speed of a large proportion of the N3 GP practice DSL connections - see below for more details.

Catalogue Services

N3 user access connections are known as Catalogue Services. There are a wide range of catalogue services for the different sizes and needs of NHS organisations.

There are three main categories:

  • ADSL Broadband Services - for small sites.
    • Historically up to 8Mbps. With GP NGA a large proportion will be upgraded to:
      • Up to 20 Mbps using ADSL2+ services
      • Up to 40Mbps using Fibre To The Cabinet (FTTC) services, where available
  • Private Circuit - for medium sites (2Mbps - 34Mbps "symmetrical").
    • Often now replaced by more cost-effective higher rate ADSL or low/medium rate Ethernet services.
  • Ethernet - for large sites (10Mbps - 100Mbps)
    • With ‘bespoke' (custom) service solutions are available for up to 1Gbps.

There are also a range of remote secure access services for mobile / remote workers or occasional N3 users.

Data Centre Services

Data Centre connections are a special type of catalogue service. Data Centres host applications and so serve many end-users, making them focal points for data traffic. Therefore they are connected directly into the N3 core, in the same way as an N3 Access PoP. They are typically 100Mbps - 1Gbps services.


N3 security protocols mean each catalogue service connection has a firewall between local networks and computers and the N3 network, to control what can go back and forth. For small site services - such as for GP practices - the firewall is provided within the router that terminates the N3 connection on site.

Although N3 is a private and secure network, data passing across N3 is not encrypted (unless using certain remote access or GP Main-Branch VPN services. The sender and receiver of sensitive data is responsible for the data's security.


Community of Interest Network (CoINs) are networks for local NHS communities. There are now over seventy CoINs connected to N3. Local data traffic stays within a CoIN, reducing the data traffic on the main N3 network. Multiple individual connections into the main N3 network are replaced by one or two CoIN gateways.

Some CoINs are fully-managed by N3SP. In other cases N3SP manages the CoIN gateways and the local NHS community manages its own CoIN infrastructure.


N3 has a number of gateways to other networks. The main gateways are summarised below.

The Internet Gateway is the biggest and most important gateway. It does two equally important tasks. It's the:

  • Single aggregation and access point for all Internet-bound traffic from N3 users.
  • Firewall that protects N3 from the Internet, making sure that whilst N3 users can get onto the Internet, no Internet user can get onto N3.

The Internet Gateway infrastructure was enhanced during 2011 resulting in:

  • Capacity/Bandwidth increase - by nearly three times
  • Web Traffic Categorisation and Prioritisation capability
  • Virtual (dedicated) Internet Gateway capability/capacity

Pharmacy Gateway(s) - in England a large number of pharmacy connections are aggregated and connected to N3 via a small number of gateways, to access for Electronic Prescribing.

JANET Gateway - allows doctors and healthcare professionals, particularly in teaching hospitals, to access the UK university private network from their N3 connected devices.

GCSX/F Gateway - this gateway allows limited and controlled access for nominated N3 users to access the Government's GSI private network.

NHS Wales Gateway - NHS Wales runs a separate private data network, but NHS Wales and N3 users can interconnect via this gateway.