Leader: RingCentral  

Formerly a small-business UCaaS player, RingCentral now holds its own with midsize and enterprise customers. RingCentral offers its own telephony, mobility and workstream collaboration software and the company partners with video provider Zoom for meetings. RingCentral, Belmont, Calif., this year launched an integrated meetings/telephony/messaging client, as well as AI partnerships for sales productivity.

RingCentral in January said it was buying cloud contact center provider Connect First to combine its own inbound contact center technology with Connect First's technology for outbound and blended customer interactions. RingCentral's channel chief, Zane Long, told CRN in March that the company's channel program's revenue grew 80 percent year over year.

Strengths: RingCentral has grown its revenue by at least 30 percent year over year for the past several years. The company's technology can now support clients above 5,000 end users with increasingly stronger global support, and brand recognition is growing as well.

Weaknesses: The company is still leaning on technology partnerships for core parts of its UC portfolio, such as its videoconferencing functionality. Some customers have said RingCentral's UCaaS pricing is above market averages.