When compared to traditional T1/PRI, SIP Trunking provides many additional benefits to companies. SIP trunk allows a company to replace traditional fixed Public Switched Telephone Network (PSTN) lines with PSTN connectivity via a SIP trunking service provider on the Internet. SIP trunks can offer significant cost-savings for enterprises, eliminating the need for local PSTN gateways, costly ISDN PRIs.
T1/PRI – Con’s:
● Connections are physical
● Each circuit requires physical connection and costly termination hardware.
● Scaling up requires the installation of new circuits and additional termination hardware in specific increments. In the case of PRI the increment is usually 23 voice channels.
● Providing sufficient backup circuits to remote sites in an IPT-distributed architecture can negatively impact the ROI. Only way to accommodate loss of hardware or facility where PRI’s terminate is to build-in excess capacity with associated cost impact.
● Cost is usually per circuit per month. If you require one, or a few, more voice channels than the fixed increment, the cost model for PRI is inefficient.
● 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.
● Diverting calls to alternate locations can be complex and expensive. Diversity across service providers is usually cost prohibitive.
SIP – Pro’s:
● Connections are virtual. Number of available trunks is a function of available
bandwidth, not physical termination hardware or circuits.
● Scales up or down easily and quickly (a software configuration change) and can offer
automatic and on-demand burst capabilities.
● Automatic IP re-routing capabilities allow practical geographic distribution of PSTN
connectivity to sites with limited or network redundancy. 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.
● Relative to PRI circuits and the associated supporting hardware, IP Trunking costs
are usually significantly lower.
● While capacity planning is still important, adding additional capacity can be as simple
as a software change. Some providers offer burst capabilities to accommodate brief
periods of higher than anticipated utilization.
● SIP technology allows for automatic call rerouting to pre-defined locations should the
location go offline (a huge business continuity benefit). Can accommodate diversity
across service providers much like is done today with Internet access via BGP.