SIP trunking connects your site directly into the service providers’ network via an IP connection to carry and terminate your inbound and outbound voice calls across the public telephone network.
The service provides a highly flexible alternative to ISDN solutions and should work successfully with all the leading IP PBX brands in the UK market.
Compared to ISDN, SIP trunks are cheaper on a per channel basis, more flexible in terms of what telephone numbers you can have and where you can have them, is quicker to install and offers a very robust business continuity service.
The service can support connections ranging from two channels for businesses with small PBXs to no limit on the number of channels that can be supported for large enterprises and contact centres. All good suppliers will deliver this as an end-to-end service with an availability guar¬antee, voice channel and voice quality guarantees.
The flexibility with your phone numbers allows you to move office and keep your same geographic number without any ongoing call forwarding costs and costs associated with new company stationery.
If your office has to be temporarily relocated in an emergency, this can quickly and cost effectively be achieved with SIP trunking.
IP connectivity costs less than ISDN with free internal calls between extensions and offices (including international calls) and lower line rental costs for multi sites. Also, no expensive call-forwarding costs are required should you relocate or need to divert calls in the event of a disaster.
However there is a downside. A broadband failure would shut down all call traffic and a broadband slow down could impact call quality. Also with ISDN trunks you can switch your call traffic (LCR – Least Cost Routing) between networks or re-sellers at no cost to get the best call rates, with SIP trunks you can’t and have to accept the rates from the service provider.
Interestingly, a recent SIP article in the trade press had the top two key areas for resellers to consider as:
– Make more margin selling SIP rather than ISDN.
– Protect incomes by reducing churn of LCR.
There are definite advantages of SIP but not all companies will need them so careful analysis is needed before those old ISDN lines are ripped out.