VoIP is the term used for making or receiving phone calls over the internet or internal networks. It stands for Voice over Internet Protocol.
SIP is an application layer protocol that is used for multimedia sessions including VoIP calls. It stands for Session Initiation Protocol.
The term SIP, or SIPs, is often used as a shortcut meaning SIP Trunks. The term ‘trunk’ in itself is misleading as it has no distinct physical form but relates to the ability for two end points to make and receive telephone calls over an IP connection. The use of SIP Trunks requires a dedicated end point, usually a telephone system, and for resilient services a dedicated data connection is recommended.
SaaS (Software as a Service) is being used as the next generation of telephone calls where the services are native cloud provided and telephone calls are made and received by an App using any internet connection, or through a telephone system. Telephone handsets working on SaaS are an App that is designed to work in a physical handset instead of a desktop or mobile. SaaS solutions often use SIP as a technology and are usually deployed on a network shared with data.
Hosted telephone systems usually use SIP to connect a dedicated handset to a network based telephone system, often requiring a dedicated data connection.
UC solutions (Unified Communications, voice / e-mail / instant messaging / chat), by their nature of being multimedia, are SaaS usually using SIP.
These are the newer technologies being used to replace traditional business telephone systems that use TDM – Time Division Multiplexing – which is the protocol used by ISND telephone lines.
Gateways are available to connect SIP and SaaS to existing telephone system.
We hope this helps.