AT&T last week began touting new IP service-level agreements that constitute some of the strongest performance guarantees available.AT&T\u00a0last week began touting new IP service-level agreements that constitute some of the strongest performance guarantees available.The carrier's revised SLAs guarantee that its IP services, including standard dedicated Internet access and IP VPN services, will be available at least 99.999% of the time. It also is promises that packet delivery will be at least 99.9% and latency will not exceed 39 millisec on average, per month.Competitors will be forced to take notice, says Kate Gerwig, principal analyst for business network services at Current Analysis. "Especially for commodity services like dedicated IP. What else is there to differentiate on other than network performance and SLAs?" Gerwig asks.Business customers continue to look to SLAs as a means of comparing providers."SLAs are extremely important when purchasing IP services," says Jason Hittleman, IT director at RKA Petroleum in Romulus, Mich. "For RKA Petroleum Companies, service availability is the most important SLA, since redundant circuits are not always an option."RKA is not alone according to analysts."SLAs consistently rank high in provider selection criteria," says David Parks, a senior analyst at The Yankee Group.AT&T's previous SLA offered a minimum packet-delivery guarantee of 99.3% and stated that latency would not exceed 60 millisec."Our previous metrics did not match network performance," says Joe Faranetta, director of IP services at AT&T. "When performance and SLAs were mismatched like ours, you get raised eyebrows from customers."For more than two years, the carrier has been posting network performance on its customer Web portal, where customers could see that the carrier's average latency did not exceed 35 millisec, he says.While AT&T's new SLAs are solid, the carrier is not leading the market with its service availability guarantee. MCI has offered a 100% service availability guarantee since 1999. But AT&T's packet delivery and minimum latency SLAs are now the strongest of the major national providers.AT&T also has improved its SLAs for IP services throughout the world. The carrier now guarantees latency will not exceed 90 millisec in Asia Pacific. And it is guaranteeing packet delivery of at least 99.8% in Europe.The carrier also offers provisioning SLAs for all circuits in the U.S. The SLA says that T-1s will be provisioned within 30 calendar days. MCI guarantees T-1 provisioning within 45 business days.And for the first time AT&T is offering a meantime-to-repair guarantee that says T-1 outages will be fixed in three hours or less.It might be difficult to imagine how users make buying decisions based on SLAs when the differences are sometimes as small as .001%, but if you are a financial firm looking to roll out\u00a0grid-computing\u00a0applications that are based on real-time market changes, .001% could make a difference, Parks says.Current Analysis' Gerwig agrees. "As more and more users get into VoIP, the more important SLAs are, especially for sensitive applications," she says.Which isn't to say there aren't caveats. One carrier marketing manager, who asked that he nor his company be named, says he once told a customer, "SLAs are one part science, one part marketing and one part black magic." Considering that, users need to understand how SLAs apply to their specific IP services and when compensation kicks in if the service provider falls short.MCI's 100% service-availability guarantee has a caveat that only applies to its IP VPN customers. These users need to be sure their local loop does not exceed 50% utilization, or else MCI's SLA is null and void. If buying standard dedicated Internet access from MCI, this does not apply.\u00a0How they compareAT&T last week beefed up its service guarantees for IP services. Here\u2019s how the carriers\u2019 U.S. service-level agreements stack up.Carrier Round-trip latency Minimum packet delivery Service availability Jitter AT&T39 millisec or less99.9%99.999%n\/aMCI45 millisec or less99.5%100%1 millisec or lessSprint55 millisec or less99.8%99.9%2 millisec or lessUsers need to calculate when credits should kick in. After service is unavailable for at least 1 minute, AT&T will credit customers one day of service based on their monthly service charge if the carrier misses its 99.999% service availability SLA. But when you calculate the 99.999% guarantee, users should be credited after about 24 seconds.AT&T says it rounded up to 1 minute because it was a neater number.Users should ask for the SLAs they need, even if guarantees are not part of the standard offering.AT&T is not offering a jitter SLA with its standard IP services, but it does with its managed VoIP offerings. It's possible the carrier would include the metric if the SLA is important to a customer.Also if you're looking for a stronger service availability guarantee from\u00a0Sprint, which currently promises 99.9%, one is available. The carrier says it will guarantee 100% service availability if the customer buys a redundant local-loop connection that terminates at a different facility.