When it comes to its service-level agreements, BT Americas differentiates itself by providing realistic performance targets that its customers can rely on for network availability and reliability.

"What our customers were asking for is to see an SLA that truly allowed them to set expectations about network performance," says Ian Bailey, senior product manager at BT responsible for SLAs. "What we did was to put together a program to analyze the risk by supplier and the risk by location so we could offer truly realistic targets. These targets are based on what they can get from the network in terms of availability and reliability."

BT calls this strategy, which it launched last spring, "target-based SLAs." BT's target-based SLAs apply to its Multi-protocol Label Switching (MPLS) network, which now features 19 nodes in the U.S. alone.

We're looking at BT's SLA strategy as part of an ongoing series on the SLAs offered by top-tier ISPs. In previous issues of the ISP News Report, we've analyzed the SLAs offered by AT&T, MCI, Infonet, Equant, Sprint and Internap. (You can view reports about the other SLAs in the ISP News Report archive: http://www.nwfusion.com/newsletters/isp/index.html .)

Some ISPs such as MCI claim to provide 100% availability on their IP backbones. BT instead offers what it says are more realistic performance guarantees for its IP network.

"We used to guarantee 100% availability at one point, but any customer who puts the tiniest bit of thought into it will realize that that's not possible," Bailey says. "For our best products, we offer better than five nines of availability [99.999%]. But to do that we have to have knowledge of the infrastructure and sometimes it comes down to the design of the network."

To achieve the highest possible network availability, corporate customers have to purchase their network infrastructure from BT on an end-to-end basis, says Kevin Moss, general manager, product management for BT Americas. 

"We don't have to be the underlying infrastructure end to end, but the customer has to be buying it from us so we have management and control over it," Moss says. "The network design makes the difference between three nines, four nines and five nines of availability."

As an example, BT executives describe a customer network that has 200 sites around the globe. Only 10 of those sites have data centers, so it's critical for communications to remain available to those 10 sites. These 10 sites have higher-end services, more redundant links and more stringent SLAs than the other 190 sites.