ad hoc study
Because of the general trend towards IP, SIP trunking will prevail in the long term and eventually replace ISDN as it offers a series of advantages: granularity, flexibility and centralisation, that is, cost savings. However, only large enterprises with several distributed offices can really benefit from these opportunities, aggregating the number of channels onto a few sites, instead of maintaining ISDN at all sites. As companies migrate to IP telephony, it makes sense to link an IP PBX to public networks via the same core protocol. In the coming years, carriers’ gradual switch-off of their ISDN networks will add to the current drivers.
These are just some of the key findings of a recent study that InfoCom carried out. The research analyses some of the main technical architectures, features and SLAs of the offers of a selection of SIP trunking providers active in Western Europe, including large international providers — targeting mainly large enterprises — as well as local providers targeting mainly SMEs.
The research also highlights the distinct advantage of SIP trunking in terms of granularity and flexibility towards the number of voice channels, as it allows any number of voice channels, unlike ISDN. An additional combined advantage of SIP trunking and IP PBX is also the possibility to centralise the voice channels. Through an underlying VoIP VPN, companies can choose to have IP PBX and SIP trunking only in one central site (or a few main sites). Therefore, as a result of granularity, flexibility and centralisation, companies may achieve significant cost savings.
Finally, a possible future advantage is the support of other SIP-based UC (Unified Communication) applications. Currently UC applications (unified messaging, presence, video conferencing) are confined mainly within a company’s own VPN sites. However, in the future, SIP trunking could enable some of these UC functions to work not only between all the sites of a company — even those not linked via a VPN — but also with third parties.