“There are two principal ways of achieving effective telecoms resilience, each with their own merits. You can either choose to send your phone calls over SIP trunks or alternatively you may decide that PSTN still offers the best quality and reliability by re-routing incoming calls at the local serving exchange. This method does not rely upon any ‘last mile’ circuits into your organisation’s building.
If SIP trunks are the best choice for your organisation then it would be wise to be aware of the following:
Be confident in the longevity of the SIP provider. Telco’s have been around a lot longer and therefore have a longer track record to reference and are likely to stick around.
You should ensure that your PBX supports SIP otherwise you will have to invest in a separate SIP gateway.
Ensure that your SIP provider has a resilient, fully distributed model and does not operate out of a single data centre.
Ensure that your SIP provider is able to use multiple carriers for added resilience and reliability.
At the present time SIP still offers lesser quality in comparison to PSTN with regards to packet loss, latency and jitter, though improvements are continuously being made.
Alternatively if you choose to re-route your incoming voice calls over the PSTN network you may wish to consider whether you want to re-route some, or all, of your incoming calls to alternative locations. Technology is available to offer full flexibility of re-routing individual DDI numbers to any number in any destination.
Would you want your incoming calls to be automatically re-routed to a default calling plan in the event that your ISDN circuits are severed? This ensures that you never lose an incoming call in the event that your circuits are cut or become faulty.
Finally I’d urge you to consider the advantages of including voice recording of your incoming, outgoing and re-routed calls to provide an audit trail of who said what during a business disruption and how you managed to continue providing great customer service.”