Enterprise communications have been rocked by two major developments over the past decade. On the network side, legacy network services like PRI and frame relay have given way to all-IP based alternatives. On the premises side, traditional circuit switched or TDM-based PBX systems have been overtaken by hybrid or full voice over IP (VoIP) solutions. Businesses are increasingly moving to SIP services to reduce cost and increase reliability while adding functionality. This paper explores the overall market for SIP, describe the major areas where they differ, and to provide a better understanding of the alternatives and how those elements should be factored into the buying decision.
