Resilient BTnet: keeping your site online

Why one line is a single point of failure

BTnet is a dedicated, uncontended line with BT's service levels behind it. But BT's availability service level is a standard with service credits; it does not mean a fault cannot happen. If a cable is cut in the street, equipment fails or work at your building disturbs the line, a single connection leaves your site offline until the fault is fixed.

For many businesses an outage is an inconvenience. For others it stops trading. Think about what happens at your site if the internet goes:

• Phones on a cloud phone system such as BT Cloud Voice stop working at that site
• Cloud apps, Microsoft 365, booking and stock systems become unreachable
• Card payments, ordering and customer Wi-Fi go down
• Remote staff lose access to systems hosted at the site
• CCTV and building systems that report to the cloud go quiet

Service credits compensate you after the event. Resilience is about carrying on during it. The two work together: BT's terms say that where you have a resilience option and a qualifying incident occurs, BT applies the availability credit at the impacted site.

BT's three resilience options

BT's service schedule for BTnet sets out three resilience options, each using a secondary access line alongside your primary line. Depending on your configuration, the routing protocol, the speed of your network and which options are available at your site, BT provides one of them as set out in your order.

In each case, BT's terms ask you to connect the equipment for the secondary line to the same segment of your LAN as the equipment for the primary line, so your devices can reach either line. Each option is described in more detail on its own page.

What availability depends on

Resilience is a design, not a box to tick. Because availability depends on your configuration, routing, speed and location, the right answer is worked out site by site. These are the questions that shape it, and the ones we raise at quote and survey stage:

• Separate routes. Two lines that share the same duct into the building, or the same route down the street, can be cut by the same incident. Ask what route separation is possible at your site; the site survey is where this is confirmed.
• Separate entry points. Where a building allows it, a second entry point reduces the chance of one piece of work affecting both lines.
• Power. Where BT's equipment is on site, BT's terms make a secure, continuous power supply, with back-up power to the relevant British standards, your responsibility. Lines and routers on the same power circuit as everything else go down together.
• Your own equipment. If you run your own router or firewall on BTnet wires only, a second line does not help if that one device fails. Consider how your edge equipment is made resilient too.
• How much speed you need during a fault. This is the main difference between failover, load balancing and a back-up line, and the main driver of cost.

Your LAN is the other half of the picture. Resilient lines are of little use if a single switch or a single cable in the comms room carries everything.

Plan for the outage, not just the second line

A second access line is the foundation, but the sites that come through a fault well are the ones that have decided in advance what happens. A short written plan, agreed before you need it, covers:

1. Who reports the fault. BT's terms expect you to run your own helpdesk for staff and to report incidents to BT's service desk using BT's procedures, with a contact available to follow each incident through. Make sure that person, and a deputy, know how, and that staff know to go to them.
2. How you will know. Decide what alerts you, or which symptoms people should report, so a line running on its second path does not go unnoticed for days.
3. What pauses. Agree which activities stop while you run on one line, such as large uploads, backups and software updates, and who switches them off.
4. How you tell people. A simple message for staff, and for customers if they are affected, saves time when phones and email are under pressure.
5. What you record. Note when the fault started, when it was reported, the ticket number and what was affected. BT's SLA claims need the ticket and your reference, and have a 28-day deadline.
6. When you test. Schedule a test of the resilient design, and repeat it after changes to your network, so you know it works before a real fault.

We can help you put this plan together alongside the design and quote, so the line, the equipment and the people are ready together. See BT leased line support for how fault reporting works.

Resilience, the SLA and cost

A second line changes the commercial picture as well as the technical one. In plain words, under BT's terms:

• Charges apply per bearer. Where resilience uses dual access bearers, service introduction charges apply to each bearer, including the secondary line, and so do cancellation charges if the order is cancelled before the service goes live.
• The second line is part of the order. BT's terms say that once the primary line's bearer has been delivered, the secondary line cannot be cancelled on its own, so settle the resilience design before you order.
• Credits apply at the impacted site. If a qualifying incident hits a resilient service, BT applies the availability credit at the impacted site.
• Contract terms follow the order. The minimum period, termination charges and moves rules in BT's terms apply to the service as ordered; see BTnet contract terms.

We do not publish prices, because each design depends on the site. Our BT leased line cost guide explains the factors, and we set out the cost of each resilience option side by side in your quote so you can weigh it against the cost of downtime. Ask us for a quote.

Choosing the right option

There is no single best answer; it depends on what downtime costs you and how much speed you need while the main line is out.

• If the site must carry on as normal, a failover line of similar capacity is the natural fit.
• If you want to use both lines every day, load balancing puts the second line to work, as long as each line can carry the essentials alone.
• If essentials are enough during a fault, a lower-speed back-up line can cost less than matching the primary.
• If you have several sites, consider resilience for the ones that would hurt most, such as a head office or data centre link. See BTnet for multi-site organisations.

A useful exercise before you decide: list what must keep working, how many people rely on it, and how long you could manage without it. That turns a technical choice into a business one, and it gives us what we need to design and quote. Contact us to talk it through.