SIP Trunking Will Displace PRI

Physical connections:

Each circuit requires physical connection and costly termination hardware.

Connections are virtual:

Number of available  trunks is a function of available bandwidth, not physical termination hardware or circuits.

Scaling up requires the installation of new circuits and additional termination hardware.

Scales up or down easily and quickly (a software configuration change) and can offer automatic and on-demand burst capabilities

Providing sufficient backup circuits to remote sites in an IPT-distributed architecture can negatively impact the ROI.

Automatic IP re-routing capabilities allow practical geographic distribution of PSTN connectivity to sites with limited or no network redundancy

Cost is usually per circuit per month

A variety of pricing models (i.e. usage based) are likely to emerge, including on-demand capacity.  Relative to PRI circuits and the associated supporting hardware, IP Trunking costs are likely to be significantly lower.

Capacity planning & engineering is critical:

Additional capacity must be planned well in advance since considerable lead time may be required for the ordering and installation of new circuits and termination hardware

While capacity planning is still important, adding additional capacity can be as simple as a software change. Additionally, providers are likely to offer burst capabilities.

Only way to accommodate loss of hardware or facility where PRI’s terminate is to build-in excess capacity with associated cost impact.

Can be designed to retain PSTN reachability and capacity in the event of the loss of terminating hardware (or even an entire office location) without the need to build in excess capacity

Including dispersed locations in most current IP Telephony deployments requires the addition of network redundancy or significant local PSTN connectivity (analogue or ISDN trunks) to ensure that individual locations can function autonomously in the event of a failure. These factors can add substantial Opex and Capex.

Dispersed locations can be connected to the PSTN via an IP connection. Should a network failure occur incoming calls can be automatically rerouted to the isolated location.

Diversity across service providers is usually cost prohibitive.

Can accommodate diversity across service providers much like is done today with Internet access via BGP.