XO Communications, LLC, previously Nextlink Communications, Concentric Network Corporation and Allegiance Telecom, Inc., was an American telecommunications company.

XO provided managed and converged Internet Protocol (IP) network services for small and medium-sized enterprises.

[2] In a news release dated February 22, 2016, Verizon announced plans to acquire XO Communications' "fiber-optic network business.

"[3][4] In 2017, Verizon completed its $1.8 billion acquisition of XO Communications.

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