A SIP trunk is an IP connection to a service provider that can route the Session Initiation Protocol.  Since SIP is still evolving, service providers and vendors realized the need to standardize on a SIP connection interface. The SIP Forum, an independent industry organization, defined a set of interconnection rules called SIPconnect™.  It is an interoperability guideline for linking a customer premise-based IP communications server with a service provider’s SIP-enabled network.

 

Avaya Communication Manager 4.0 (and above), as well as SIP Enablement Services 4.0 (and above), support SIP trunking, and have received SIPconnect™ certification. By working with SIPconnect™ certified service providers, Avaya Communication Manager customers can switch over from their existing TDM-based connection to a SIP-based trunk without risking technical or operational incompatibilities.

 

With SIP trunking, inter-office calls—for example, an extension in the corporate dial plan—are managed in a similar way to an intra-office call. In this case, the service provider takes on the responsibility of routing the session set-up message from Avaya Communication Manager to your remote location’s SIP-based communications server or SIP endpoint. As long as the call avoids the local carrier’s network and remains on the provider’s network—“on net” calling—no per-minute toll charges are involved, resulting in lower recurring telecom costs.

 

Additional  cost savings  comes from eliminating separate  voice connections to each office. SIP trunking requires only one SIP  connection per location to the provider’s network. This contrasts with traditional and more costly TDM voice networking where separate point-to-point circuits and gateways devices are associated with each connection to a remote office. 

 

Therefore, growing businesses that are adding new offices can achieve significant savings because per location network connection costs remain fixed —the cost of the single SIP connection covers complete network access.

 

For calls that are “off-net”—in other words, a call to the public network or PSTN—the service provider, through its VoIP gateways, terminates the outgoing call, translating between SIP and TDM. Long distance rates from a SIP service provider are generally very competitive. 

 

SIP service providers generally offer a bundled service arrangement involving inter-office data and voice networking as well as internet access. Because businesses now have a single SIP connection to a VoIP service provider that supports voice, video, and data, they have the opportunity to consolidate their networking and voice equipment for further costs savings.