When an MSP or IT service provider sells onsite support, the field service SLA is the promise the customer remembers. It decides how fast an engineer must be on site, and it shapes the cost of every visit behind it.
Most onsite work falls into three response types: 4-hour, next business day and scheduled. This guide explains each one, when to use it, and the small print that causes most disputes.
What a field service SLA actually measures
A field service SLA normally measures the time between a ticket being accepted and an engineer arriving on site. It does not usually promise a fix within that time, because the fix may depend on parts, vendor support or customer access.
Before comparing options, agree three definitions with your partner and your customer:
- Clock start: when the ticket is logged, or when it is accepted with a complete brief?
- Clock stop: engineer on site, or engineer on site with access granted?
- Service hours: business hours only, extended hours or 24/7?
Getting these right avoids most arguments about whether an SLA was met.
4-hour SLA
A 4-hour SLA means an engineer arrives on site within four hours of the ticket being accepted. It is used for faults that stop a business or a service: a core switch down, a failed server in a colocation hall, or a branch site with no connectivity.
When to use it
- Critical infrastructure where downtime has a direct revenue or safety impact.
- Data centre and colocation work where smart hands are needed quickly.
- Sites covered by a customer contract that already commits you to 4-hour response.
What to watch
4-hour response depends heavily on location. In central London, Frankfurt or New York it is routine. In smaller towns it may need an engineer to travel further, so ask for city-level confirmation. Our measured 4-hour attainment is 94%, and we are open about the locations where it is harder to achieve.
Next business day (NBD)
Next business day means an engineer attends on the working day after the ticket is accepted, usually provided the ticket arrives before a cut-off time. It is the workhorse of onsite support: most hardware swaps, desktop faults and non-critical network issues sit here.
When to use it
- Faults with a workaround in place, such as a failed access point in an area with overlap.
- Parts-led repairs where the replacement ships overnight.
- Routine IMAC and break-fix work across many sites.
What to watch
Check the cut-off time and how local public holidays are treated. A business day in Dubai or Riyadh does not follow the same week as one in Dublin. Our next business day attainment is 99.99%, and a 24-hour option sits between NBD and 4-hour, with 98% attainment.
Scheduled visits
Scheduled work is booked in advance for a specific date and time window. It covers installations, moves, surveys, decommissioning and planned maintenance.
When to use it
- Planned changes during a maintenance window.
- Multi-site rollouts where many locations need the same task.
- Surveys and audits that need customer staff present.
What to watch
The risk here is not speed but readiness. A scheduled visit fails when access is not arranged, kit has not arrived or the scope changed. Good partners confirm site readiness a day or two before and flag gaps early.
Choosing SLAs across the UK, Europe and the Middle East
Most providers end up with a mix. A typical pattern is 4-hour for data centres in London, Amsterdam and Frankfurt, next business day for offices in Manchester, Paris and Madrid, and scheduled for project work in Dubai or Riyadh. Match the SLA to the impact of the fault, not to a blanket policy, and you avoid paying for urgency you rarely use.
For more on reactive work, our guide to break-fix IT support covers how the repair process fits around the response window.
How a partner delivers your SLA
Behind every SLA is a dispatch process. At Simplify Networks jobs are coordinated from London, with a 24/7 service desk responding in under 30 minutes all year. We match each ticket to a suitable engineer from more than 2,000 worldwide, confirm the brief and track arrival. Our dispatch and SLAs page explains how this works in detail.
Where we cover
See the full list of 285 cities on our coverage map, or visit country pages for the UK, the Netherlands, Germany, the UAE and the USA.
Frequently asked questions
What does a 4-hour field service SLA mean?
An engineer arrives on site within four hours of the ticket being accepted. It measures arrival, not resolution, and is usually reserved for critical faults.
Is next business day the same as 24 hours?
No. Next business day depends on working days and a cut-off time, so a ticket logged on Friday afternoon may not be attended until Monday. A 24-hour SLA counts elapsed hours instead.
When should I use a scheduled visit instead?
Use scheduled visits for planned work such as installations, moves, surveys and maintenance windows, where readiness matters more than speed.
Does the SLA clock include travel time?
Yes. The response window normally covers the time it takes the engineer to reach the site, which is why city-level confirmation matters for 4-hour cover.
Match the right SLA to every site
Send us your site list and the response times you sell. We will confirm what we can cover in each city and share our partner rate card.