What makes SIP so popular is not only that it's deep and flexible, but also because it was purpose-built to engage in multimedia (meaning not just audio but also video and even text) communications over TCP/IP networks. For VoIP calls, SIP can set up calls using a number of IP-related protocols, including the Stream Control Transmission Protocol (SCTP), the Transmission Control Protocol (TCP), and the User Datagram Protocol (UDP), among others. But it can also handle other functions, including session setup (initiating a call at the target endpoint—the phone you're calling), presence management (giving an indicator of whether a user is "available," "away," etc.), location management (target registration), call monitoring, and more. Despite all that capability, SIP is simple compared to other VoIP protocols primarily because it's text-based and built on a simple request/response model that's similar in many ways to both HTTP and SMTP. Yet, it's still capable of handling the most complex operations of business-grade PBXes.  
However, you may also want features like on-hold music, call queues, voicemail to email translation, and automatic answering and forwarding of calls. If all of the employees are working out of the office, you can use the automatic attendant to determine which employee should receive the call. The attendant then can route the call to that employee’s mobile phone.

1. The Microsoft 365 Business Voice service components of Domestic Calling Plan and Audio Conferencing are sold inclusive of all required taxes and fees, including 911 fees and other transactional taxes that typically apply to communication services in the U.S. The price includes these taxes and fees until June 30th, 2021. The Phone System component is sold tax exclusive and any applicable sales tax will appear as a separate charge in the U.S.

Residential VoIP service providers are the most popular choice for home phone services in 2020. Millions of homeowners have switched to VoIP from a regular landline service and enjoy significant cost savings, unlimited calling plans, and amazing calling features (such as call forwarding, call blocking, voicemail to email and more). We will help you find the best VoIP service for your home:
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