Network sizing and capacity guidance

Organisations that use digital services (consumers) should run an audit of their Digital Service estate and use it to inform their implementation planning. See consumer guidance for more details of this.

Network capacity is an important factor.

Consumers should:

1. understand current and planned network usage (as part of your audit and planning process)
2. review the model office class summaries provided in this guidance and determine which class your organisation will fit within, based on the size of the organisation and the type and volume of Digital Services you use
3. discuss the proposed requirements with your network service provider to make sure your network service has enough capacity and flexibility to meet current and future needs

The NHS currently uses the Health and Social Care Network (HSCN) as its centrally provided hybrid network.

The HSCN consists of:

• a private networking capability, through ethernet and broadband, which allows access to the national Digital Services via the NHS Spine
• an internet breakout capability, similar to business broadband

HSCN is the standard network that is expected to be used by the NHS and social care system, until critical applications on the NHS core infrastructure are ready for the internet.  

When national critical systems are available over the internet, consumers will be able to choose their own network connectivity provider. The private networking component of HSCN may no longer be needed to access national Digital Services, including NHS Spine based services.

As more Digital Services become available over the public internet, the use of private networks should gradually reduce. The need for internet breakout capability may increase.

Services such as NHSMail2, voice and video conferencing, PACS imaging and PAS systems use significant bandwidth. At the moment, most organisations run them across the HSCN. Bandwidth will need to increase for users to access these services over the internet.

Other variables that may have an impact on bandwidth requirements include:

• increase in the numbers of users
• accessibility methods
• changes to system functionality

We have developed these model office classes from experience of HSCN implementations against consumer requirements between 2018-20.

They can be used as a guide, but you should always discuss requirements with your provider to get an accurate estimate of current and future needs.

Class 1: small site

Example: Small GP surgery or ambulance base

Digital services use: not expected that high-bandwidth services will be used imminently

Recommended: 50 mbps Ethernet/FTTC/FTTP type connection

Class 2: medium site

Example: Large GP surgery, medium acute, CCG base or large ambulance base

Digital services use: significant requiring high bandwidth - medium scale PAS deployment, PACS imaging, x thousands of NHSmail2 users, many services connected to the NHS Spine, video conferencing widely used

Recommended: 100 mbps to 2 Gbps Broadband type connection

Class 3: large to very large site or multi-site across a trust

Example: Large to very large acute, large headquarters building

Example sizing:

• large - University Hospitals Plymouth, Royal Free Hospital
• very large - St George's University Hospital

Digital services use: significant requiring high bandwidth - large scale PAS deployment, PACS imaging, x thousands of NHSmail2 users, many services connected to the NHS Spine, video conferencing widely used

Recommended: 2 Gbps minimum broadband type connection for a large acute and up to 6 Gbps for a very large acute across multiple sites

Class 4: National data centre or large regional gateway capability

Example: data centres, community gateways, community of interest networks (CoINs) with multiple large sites

Example sizing:

• NHSmail and Spine data centres
• The Essex CoIN with more than 500 connections.

Digital services use: very high bandwidth required to support national systems or large numbers of connections

Recommended: up to 10 Gbps broadband type connection

NHSmail2 example

An NHSMail2 instance with *** users is currently accessed using the private network and uses *** bandwidth.

This Digital Service is currently being remediated to become fully Internet First.

Once the service is remediated, the organisation should be migrated off the legacy platforms.

Users will use their internet connection for all access to NHSmail. This will require **** of bandwidth.

Voice and video services

To estimate the bandwidth requirements of voice and video calling, multiply the figures below by the number of calls you estimate will take place at the same time.

Voice bandwidth

(Worst case) 83 Kbps per simultaneous call, a thirty-call trunk would require 2500 Kbps of good quality (low jitter) bandwidth to support.

Video bandwidth

These figures are based on MS Teams but will apply to most video calling:

• Person to person video calls of standard quality will use 500 Kbps, and of high quality will use 1.5 Mbps 
• Group/conference video calls of standard quality will use 500 Kbps up and 1 Mbps down, and of high quality will use 1 Mbps up and 2 Mbps down

Although CoINs are not Digital Services, they require significant bandwidth. Any consumers either managing, or being part of, a CoIN, need to consider the potentially changing bandwidth requirements.