It's a positive sign that Ethernet service options are emerging from carriers such as AT&T, which recently launched a 50M-to-1G bit\/sec local\/metro meshed transparent LAN service as part of its growing Ethernet service portfolio.Traditional carriers are participating in the nascent Ethernet services market. AT&T and MCI, for example, have widely deployed U.S. footprints. And in March, Sprint launched Ethernet service availability in Las Vegas, saying it would deploy service in the metro areas of 30 U.S. cities before mid-2004.Then there are less traditional carriers like Yipes, Neopolitan Networks, Level 3, Time Warner Telecom and others with Ethernet services.Ethernet shines for raw bandwidth, leveraging existing equipment and staff expertise, and scalability. However, the offerings are often lacking in the guarantees that accompany traditional T-carrier-based services.For example, AT&T boasts "industry-leading service-level agreements (SLA)" with its recently announced Ethernet Switched Service-Metropolitan Area Network service. While this might be true compared with other Ethernet services, AT&T Ethernet services director Franco Callocchia cites network availability SLAs as just three nines (99.9%) or possibly four nines (99.99%), depending on network configuration.The distinction is not quite clear. It likely has to do with which of the other four Ethernet service providers' networks AT&T must connect to in order to deliver service across its 90-city U.S. footprint (AT&T won't name its partners).Regardless, three nines is a step down from AT&T's longtime five-nines (99.999%) frame relay SLA. If the difference seems trivial, consider that 99.9% translates into eight hours and 46 minutes of downtime per year, while 99.999% translates into just five minutes. To illustrate, Meta Group estimates that in the energy industry, the eight-plus hours of downtime translates into $25 million in annual revenue losses, while five minutes translates into $235,000 in losses for that industry.Other considerations:* AT&T spins its newest service as ideal for multimedia applications, yet offers no quality-of-service (QoS) options with the service. The product manager says that AT&T customers are "looking for big fat pipes," implying that bandwidth is a good tradeoff for QoS. That's sometimes the case, but not always.\u00a0Just think Citrix and peer-to-peer applications if you believe you can skip bandwidth allocation and rate limiting, regardless of how much capacity you have. AT&T offers typical mean time to repair and installation guarantees and the mediocre uptime guarantees, but backs off from committing to specific performance metrics (latency, jitter, packet loss).* AT&T says its service is "competitively priced," but offers no ballpark numbers.* AT&T said it is currently in beta test with Ethernet access to its IP VPN and frame relay services. Those services should be commercially available in 2005.