The Basics of Sip Trunking

A basic understanding of how Session Initiation Protocol (SIP) works.

SIP Trunking is a term applied to the services offered by LECs (Local Exchange Carriers), ILECs (Independent Local Exchange Carriers), CLECs (Competitive Local Exchange Carriers) and ITSPs (Internet Telephony Service Providers) to terminate Voice over IP (VoIP) calls to the Public Switched Telephone Network (PSTN).

SIP Trunking allows enterprises and small businesses to eliminate a PSTN gateway at their site and outsource that function to a carrier. It is typically a lower-cost alternative to Primary Rate Interfaces (PRIs) because SIP trunks can be purchased in single-trunk increments (as compared to 23 channel increments for a PRI).

Other ways in which SIP trunks decrease costs:

With SIP trunks, a single network can be maintained within the organization, rather than having both a voice and data network.
Internet bandwidth can be used more efficiently.
Moves, Adds and Changes can be completed without major wiring upgrades.

SIP Trunks are delivered in several ways:

Over the Public Internet – SIP Trunking Anywhere: Allows any enterprise, anywhere, to adopt SIP Trunking and assign some, possibly unused, bandwidth to voice at no extra charge for the connection, and providing the highest ROI.

Managed Services: Carriers supply a dedicated, fully managed connection from their Point of Presence to the enterprise site. This service offers quality of service guarantees, but is somewhat more expensive.

MPLS Delivery: The carrier, usually an LEC, ILEC or CLEC, will delivery a managed service using Multi-Protocol Label Switching to insure the highest voice quality and reliability.

The voice quality, even over an un-managed public Internet connection, is excellent. Typical savings over PRIs range from 40-60% with the payback period for the equipment required, which may include an upgrade to the IP-PBX and the installation of an Ingate SIParator or Firewall, has been shown to range from 4 to 12 months.

With these facts in mind, there is no question that SIP Trunking offers compelling advantages for businesses large and small.