VoIP Glossary

What is SIP?

SIP: SIP (Session Initiation Protocol) is an internet communication standard (RFC 3261) that establishes, manages, and terminates real-time communication sessions — including voice calls, video calls, and messaging over IP networks. SIP is the signaling protocol underlying most modern VoIP systems.

How It Works

When you make a VoIP call, SIP handles the setup: it locates the recipient, negotiates call parameters (codec, bandwidth), and establishes the media session. Once connected, media travels via RTP (Real-time Transport Protocol). When the call ends, SIP sends a BYE message to terminate the session. SIP is used for phone-to-phone calls, softphone apps, SIP trunking, and video conferencing.

Business Use Cases

SIP trunking uses SIP to connect business PBX systems to the PSTN via the internet. SIP phones are IP desk phones that communicate using SIP protocol. SIP-based UCaaS platforms (like VestaCall) use SIP for all internal and external communications. Contact centers use SIP for agent softphones and skills-based routing.

How VestaCall Uses SIP

VestaCall is built on SIP standards. VestaCall supports SIP trunking for existing PBX systems, SIP-compatible desk phones, and the SIP-based VestaCall API for developers.

VestaCall SIP Trunking

Frequently Asked Questions

Is SIP the same as VoIP?
No. VoIP is the broad category of internet-based voice communication. SIP is one of several protocols used to implement VoIP. SIP is the most widely used signaling protocol for business VoIP.
What is a SIP address?
A SIP address (or SIP URI) looks like an email address: sip:[email protected]. It's used to identify VoIP endpoints like softphones and SIP trunks.
What SIP phones work with VestaCall?
VestaCall works with all major SIP-compatible IP phones including Yealink, Cisco (Webex Phones), Grandstream, Polycom, and SNOM.
What is SIP trunking?
SIP trunking uses SIP to connect your PBX or phone system to the public telephone network via the internet — replacing traditional ISDN/PRI phone lines.
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