Overview of VoIP (part 1)

 At its simplest, Voice over IP is the transport of voice using the Internet Protocol (IP), however this broad term hides a multitude of deployments and functionality and it is useful to look in more detail at what VoIP is being used for today. Currently the following types of VoIP applications are in use: 

• Private users who are using voice over IP for end to end phone calls over the public internet. These users typically trade quality, features and reliability for the fact that the service is very low cost and are generally happy with the service. Although globally the numbers of users taking advantage of this technology is large the density of such users is very low and when compared with the PSTN the call volumes are negligible. 

• Business users on private networks provided by telecom and datacom providers. These services offer relatively high quality and reliability and are feature rich but come at a price. When compared with the PSTN the call volumes supported by these services are small, however such services are nonetheless commercially successful.
• IP trunking solutions used by long haul voice providers. Typically these offerings use private IP networks to connect islands of the PSTN together, e.g. a low cost way of calling the USA from the UK. Customers access these services using traditional black phones but the voice is carried over an IP network

Although these voice over IP deployments have been successful and each will continue to have its place in the future they have not yet faced the issue of how the wider PSTN could be migrated to an end-to-end voice over IP infrastructure. Providing a voice over IP solution that will scale to PSTN call volumes, offer PSTN call quality and equivalent services, as well as supporting new and innovative services is a significant challenge.  This white paper addresses the central question of how would a carrier deploy a voice over IP service that offered end to end VoIP whilst offering PSTN equivalence. It considers the issues faced by such a carrier and how the end to end VoIP service fits into the legacy PSTN infrastructure that will undoubtedly remain for a good many years.