The Case File for Reliable Phone Service

By June 28, 2018 July 10th, 2019 No Comments

Back-Up, Resiliency and Redundancy of our voice network is among the most discussed topics we have with our clients. It is also some of the most complex conversations with all the options and technologies available. It is of the upmost importance that users of premise-based phone systems understand the limitations, because users who have a hosted PBX don’t need to worry about redundancy in the same way.

Hosted PBX: In a Hosted PBX (private branch exchange) environment, the back-up and phone system is in the cloud. In the event of a power failure, building catastrophe, or other natural disaster, the calls continue uninterrupted to the cloud phone system. For instance: if fire damaged the company phone network, the system can be restored as soon as new phones are installed. Last winter one of our hosted PBX clients lost electrical power for almost a week after an accident outside the building. Business continued uninterrupted when the employees brought their hosted IP Phones home.

Premise-Based System: For those companies using a premise-based phone system there are many other considerations and costs involved. One of the deliberations is the type of lines that the organization is using. Given that the majority of mid to large firms are still using a Primary Rate Interface circuit or PRI, I will assume that the reader still has PRI lines terminating into their office. One of the problems with PRI is that it is not very graceful when it fails. Unlike a Session Initiation Protocol or SIP trunk, which can fail seamlessly between IP addresses, a PRI can’t tolerate breaks between networks or buildings. But in a PBX environment, the failure of one host will not affect the alternate host. This improves back-up and resiliency in the phone lines.

Today there are many different brands of PBX’s available on the market. Manufactures include NEC, Mitel, and Avaya. Assuming that an Avaya phone system is being used, redundancy can be achieved with the installation of a second Avaya IP cabinet. This is also true with the other manufactures. Let’s imagine a primary phone system at the head office, and a second phone system at a data center. The applications and programming of the primary are replicated to the second and remain idle until needed. Then when the primary IP phones fail, the second phone system at the data center will automatically re-authenticate and resume routing the calls. Voice mail service will also be transferred automatically from the primary phone system to the back up network. If the company has two sites, let’s say one in Toronto and the other in Montreal, for example, the two systems can act as back-ups to one another. The IP Phones in Toronto can service the phone network in Montreal, and vice versa. The one caveat to the above is that only IP phones will fail, digital phones will not.

Phone Lines: From a phone line perspective, we now need to address how to terminate the calls to the back-up system. Returning to the earlier example of Toronto and Montreal. If the company is using SIP trunks, it is quite easy to route calls between systems because the lines are addressable via IP address.

Unfortunately a PRI circuit isn’t quite as robust when it fails. It isn’t very practical for a carrier to route the circuit between Toronto and Montreal. Instead Session Initiation Protocol SIP trunk routes are used to direct the signal. Should any PRI circuit fail, the phone signal will be sent uninterrupted somewhere else in the SIP trunk.

I recall an event a number of months ago where Digitcom’s PRI circuit failed and practically no one noticed because the signal was redirected to our SIP trunks. All calls in and out continued to flow as normal. Now if the phone system itself has failed, the network in Montreal would re-authenticate the network and calls would be routed to an alternate receptionist, or auto attendant to answer calls in the interim. The key to the success of your firm is the combination of redundancy in our networks.

Hosted PBX Back-Up: The above scenario is somewhat expensive. However, we have solutions for clients who don’t want to invest in a second Hosted private branch. The alternative is a number of extensions enabled with mobile twinning. This can be done for as little as $100/month and the company can also have a full active back-up solution that is enabled, live, and ready to go 24 X 7 X 365. We can program all users onto the Hosted private branch platform and provide twinning to their cell phones. Then when the auto attendant is called, the extension is enabled, and the call is forwarded to the users cell phone.

Creating a back-up solution for your office phone system can be complex and expensive. It doesn’t necessarily need to be if you choose the Hosted private branch back-up. If you have 2 offices already running a premise based system you might be closer than you think.

Jeff Wiener is the President of Digitcom Canada. Digitcom has been in business selling and servicing business phone systems since 1991, and has offices throughout Canada. Digitcom has been on the CDN Top 100 solution providers list for 3 years, and Canadian Business Magazine’s list of fastest growing companies since 2013. You can get in touch with Jeff Wiener at: 1-866-667-8357 ext 201, or by email at jw@ You can visit Digitcom’s web site at: digitcom.ca

Jeff Wiener


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