Voice Over Internet Protocol (VoIP)

VoIP Implementation Guide

Reliability

Next, you need to look at the robustness of the networks you are using. Losing telephony services as well as access to data could be catastrophic. Ask yourself:

• If one or more of your servers fail, is the network able to recover in sub-second time? If not, do you need to build in redundancy and/or mirrored servers?
• The standard ('five 9s') benchmark for telecom network availability is 99.999%, which is equivalent to less than five minutes of downtime a year. How does this compare to the network your VoIP will be working on?
• If you intend to switch all phone calls over to VoIP, you could end up in a situation where you can't use the phones because there's a power cut. Make sure you have a backup solution.
• You need to ensure that you always have phone access to the emergency services, if your hardware or software fails. Landline and mobile phone service providers guarantee access to 999 services, but internet telephony providers are not currently bound by the same regulations.