SIP stands for Session Initiation Protocol and is a technology at the enterprise level for delivering multiple voice connections to a PBX or key system over an IP data connection. In order for a business to utilize SIP they must have a PBX with a SIP-enabled trunk side and their data provider must be able to deploy and switch SIP.
SIP Trunks at the enterprise level of the network replace PRIs between the central office and PBXs. A PRI is a dedicated T-1 transport circuit and can support 23 bearer paths for voice, but a SIP trunk connection typically rides an existing data circuit and can be used to carve out as many voice paths as are wanted within the limits of the bandwidth available.
Following are the reasons that businesses want SIP trunks, and thus for carriers to sell them. This list is discusses the advantages for the small and medium business customer.
Saves Money. SIP generally saves money. SIP trunks replace PRIs which are inefficient. It is not unusual for a customer with a PRI to be using only part of the capacity and yet they have to pay for it all since it is a linear product. SIP trunks are typically carved out of a company’s data or Internet connection and can be sized as needed within the constraints of the bandwidth. It is typical for a business to cut their costs at least in half using SIP trunks compared to PRIs due to the efficiency.
More Efficient Use of the Data Connection. Most businesses will already have an Internet connection and SIP trunks are carved from those connections. Most businesses use their data connections in a bursty fashion, meaning there are times of the day when they use a lot of their bandwidth, but also many times when they use very little. SIP trunking can take advantage of the unused capacity in most company data connections. Companies often do not need to increase the bandwidth they are buy SIP trunks and can fit them into their existing data product.
Enables Unified Communication. SIP enables all of the various features that comprise unified communications such as access to the phone system from cell phones or tablets, integrated voicemail and email, video chat, instant messaging and other features that make businesses more productive.
Enables Upgrade to an IP PBX. Businesses more and more want the kinds of features that are available with an IP PBX and IP handsets. Many businesses are choosing to buy an IP PBX to get these features rather than buy IP Centrex from their telco provider. The general advantage for a business to have their own IP PBX is the ability to customize their communications network, something that many service providers do not offer with IP Centrex.
Allows Multiple Locations to Act like One. With SIP trunks and an IP PBX a business with more than one location can have a unified telephone system that brings the data and voice together for all locations.
Any carrier that sells enterprise data service to businesses should offer SIP trunks. Even if you sell IP Centrex, customers who prefer to have their own phone system are going to want SIP trunks.