VoIP To PSTN/ISDN Automatic Failover
The Need For Telephone Call Redundancy
Exetel uses its own VoIP services and has done since November 2005. However, although we had every confidence in the solidity and reliability of the VoIP service we chose to implement after almost two years of investigation, our directors refused to take even the smallest risk of being without a toll quality telephone service for any length of time and insisted on a 100% certainty of never being in a position where customers couldn’t call for support or Exetel personnel couldn’t call customers with information.
In proposing VoIP services to commercial organisations this is the first concern that’s raised by senior management every time VoIP is seriously considered.
Exetel, like any other commercial enterprise, has had the occasional ‘telephone emergency’ when some contractor has been installing services for another tenant in our building has taken out the building’s MDF or some part of it for an hour or sometimes more and one memorable occasion when the DMR cut the main trunk running in to our building leaving half of North Sydney’s businesses without telephones for almost half a day.
While such instances are rare they do happen and while VoIP is highly reliable it isn’t based on a Tier One Carrier’s 100 years of experience and abundance of over capacity.
The Exetel/Mitel solution provides two different methods (using two different carriers) which means that there is a higher level of reliability in implementing a VoIP telephone service solution with Exetel than there is with implementing a standalone PSTN or ISDN telephony service.
Automatic Fail Over In Case Of VoIP “Failure” Or ISDN/PSTN “Failure”
The solution recommended by Exetel is based on the customer retaining their current telephone lines (and telephone numbers) and connecting those lines (and telephone numbers) to the Mitel PABX. The Mitel PABX is also connected to the Cisco router which terminates the SHDSL Internet service.
Each person’s handset is connected via the company’s internal Ethernet network to a central switch which is, in turn, connected to the Mitel PABX and also to the Cisco router.
To call another person within the company (whether they are located within the company’s office or are located at their home or another office) they simply dial the 4 digit extension number.
Each person within the company can select whether they wish to use either VoIP or PSTN/ISDN to make an ‘out side’ call by the method they select of obtaining an ‘outside line’. To use VoIP they dial 9 for an outside line and to use the PSTN or ISDN service they dial 0.
This means that in the event that either the VoIP or the PSTN/ISDN service becomes unavailable every person can still dial out without any disruption or ‘reconfiguration’.
The Best Of Both ‘Financial Worlds’
While VoIP call costs to almost any destination are lower than ISDN/Toll call costs there are exceptions.
At the moment the main exception is the costs of calls to mobiles. Currently, at least as far as Exetel’s services are concerned, it’s cheaper to make a call to any mobile telephone using ISDN than using VoIP.
An Exetel business user can either manually select calls to mobiles via ISDN by dialing ‘0’ instead of ’9’ before dialing the number or can ‘firm’ program the Mitel PBX to select ISDN for calls to mobiles.
