Who: XO Communications.
Vitals: Based in Reston, Va., the company has a network map for a competitive carrier that includes not only fiber and DSL access, but also fixed wireless and long-haul network reach. XO has about 4,800 employees.
Why you should care: The carrier has been mostly focused on small and medium-sized businesses, but just announced a move into the large enterprise market, where it will challenge the largest telcos for their existing accounts. Some say it was also among the carriers that led price declines in the market for high-capacity circuits.