More than a year after filing for bankruptcy, MCI remains the largest backbone provider on the global Internet, according to a recent study by TeleGeography, a research division of PriMetrica.TeleGeography ranked international ISPs by the number of autonomous systems they operate. Autonomous systems are groups of routers that are able to exchange routing information externally with neighboring autonomous systems. Each autonomous system is a group of connected IP networks that follow a single and clearly defined routing policy. Among the entities that operate autonomous systems are ISPs, government agencies and multinational corporations.The TeleGeography study showed that MCI had the most autonomous system connections, followed by Sprint, AT&T, Level 3 and Cable & Wireless.MCI has ranked first in autonomous system connectivity since TeleGeography began its annual study in 2001.Alan Mauldin, a senior research analyst for TeleGeography, says the autonomous system ranking measures how well connected an IP network is to the rest of the public Internet. With more autonomous systems, a network can carry traffic to its destination with fewer hops, he says.\u00a0"This statistic shows which networks form the core of the Internet," Mauldin says.Mauldin says that between September of 2002 and June of 2003, the number of autonomous systems operated by MCI grew 11%. However, the number of autonomous systems operated by Sprint grew 77% and the number operated by AT&T grew 62% in the same timeframe."Although MCI is at the top, both Sprint and AT&T are getting really close," Mauldin says. "Both carriers have jumped way up in the past nine months."\u00a0The TeleGeography study also found that 600 companies operate international Internet backbone links, but that the top 50 operators - including MCI, Sprint and AT&T -control 95% of the capacity.Last year, the global IP transit business generated about $1.7 billion in revenues, according to TeleGeography.