https://www.thestreet.com/investing/ringcentral-cfo-talks-about-competing-against-microsoft-cisco-and-others?puc=yahoo&cm_ven=YAHOO&yptr=yahoo
Interview with Ring Central CEO- they are a 20+ billion dollar company and in this article talk of their major competitors. One competitor is Avaya, they were grabbing many seats from Avaya (Mitel and Cisco also), so Avaya partnered with them. I guess that stops the bleeding for Avaya...for now