SIP trunks are connections that link a business IP-PBX to the PSTN (Public Switched Telephone Network). Through an (ISP) Internet VoIP connection signaling goes from the business phone system to the SIP (Session Internet Protocol) provider as a virtual phone line, who then connects and establishes voice calls. The trunk connects to the PTSN. SIP trunks are much more cost effective than traditional types of phone services. They can lower phone costs using "unlimited" plans, as well as pay by the minute plans with lower bulk minute rates. Some providers offer exceptionally low rates for particular regions or countries.
SIP trunk service is significantly less expensive than traditional business telephone lines. Sometimes as much as 60 to 75% lower.
The number of SIP
channels needed by a business will depend on the type of
business and their call activity. Additionally, it will depend on
the provider and how they construct their pricing. Typically each SIP
trunk can transmit a number of SIP channels. Each channel is capable of
transmitting one call. SIP providers typically offer customers options to
subscribe to a specified number of SIP channels.
Since one SIP trunk is capable of an unlimited number of channels, you would merely require one SIP trunk with a specific provider. However, incorporating several SIP trunks, each from a different provider offers increased benefits by setting up cost effective call rules.
Configuration of SIP trunks can be done by tech savvy people and providers often offer guidance.
A small office with three people would require one trunk per person if all three were on the phone at the same time. As an office size increases the ratio of trunks per person would likewise decrease to about sixty percent. Call centers and high call volume businesses would need a high ratio of trunks or active virtual phone lines to working employees.
For businesses that generate lots of International calls SIP providers can supply unlimited calling plans to many countries or incredibly low rates. The most cost effective approach to International calling is by incorporating SIP trunks. Some providers offer incredibly cost effective services to certain parts of the world. For instance a pharmaceutical supply company that does significant business with firms in India might pick a well established Indian SIP provider. SIP trunking empowers companies to gain access to these providers. Using SIP trunks between multiple offices on the same VoIP system become free Peer to Peer calls.
SIP trunks offer the most flexibility of any phone services. The precise nature of SIP allows for multiple trunks from numerous providers to be added or subtracted instantaneously. The instant flexibility provides concise control by scaling trunks as needed using the most cost effective providers.
Regular analog trunks (PSTN phone lines) can go down from bad weather or inferior circuits. These instances routinely require a few hours minimum to correct, especially for PRI circuits. SIP trunks offer immediate virtual failover lines where calls can instantaneously be routed. Once setup these Outbound Call Rules configured in the VoIP appliance do not require administration or time consuming maintenance.