The Difference Between SIP and PRI for Communications

Mitel's Unified Communication solution provides powerful and cost effective options to maximize the availability of dial tone for users. IP Phones (also known as VoIP phones) are controlled by modular voice switch appliances that are inherently super reliable.

This reliability can be augmented by provisioning two methods of backup voice switches:

Inter-Site

This solution is ideally suited for distributed systems comprised of a larger HQ location and any a number of branch locations. Dedicated spare IP phone resources can be provisioned at the HQ location to serve the entire system i.e. any voice switch failure at a branch location will result the branch IP phones switching over and receiving service from the HQ voice switches.

This is extremely cost effective and leverages the statistical likelihood that only one branch will have a local voice switch outage at a given time.

Intra-Site (aka: N+1)

IP failover within a site is a second option of course. This might be considered for the HQ location itself or for larger semi-autonomous branch locations. This option requires spare voice switch at the location itself. What distinguishes the ShoreTel solution again is the efficiency with which the spare capacity can be provisioned.

Let’s take an example of 180 IP phones at such a location. A nominal implementation might be to deploy two voice switches capable of supporting 90 phones each. However by deploying 3 voice switches with spare capacity a more optimal backup scenario can be created: the three voice switches each nominally serve 60 phones (i.e. they each have spare capacity of 30 phones).

A failure in any of one of the three voice switches will result in the affected phones seamlessly moving over to the spare capacity on the other two voice switches. So the cost of providing backup services is 50% or less over the nominal cost of the required resources compared to 100% for more conventional redundant solutions from other vendors.

It is even possible to combine these two options and this allows Mitel to deliver an extremely robust UC platform.