Voice over IP (VoIP), in its various guises, is currently a hot topic in the business world. Today, if you attend conferences and conventions about voice communications services, more often than not, the focus is on VoIP. Most of these conferences, however, still revolve around the connectivity to the end user. This article will focus on connectivity to the rest of the world, referred to as 'exchange lines' or 'trunks', and will discuss how traditional services fit into the new landscape.
Traditional telephony
Equipment vendors, service providers and systems integrators certainly appear to have moved away from traditional circuit-switched services (for example, analogue and ISDN), so you could be forgiven for asking, 'Is it the end of circuit-switched telephony?'
Circuit switched voice services have their place and serve a variety of purposes. The stark reality is that today well over 90% of PSTN (Public Switched Telephony Network) connectivity is still provided using ISDN or analogue lines. Customer equipment such as PBXs, key systems, telephones and fax machines rely on this type of connectivity and only the latest (or upgraded) equipment will be able to use IP connectivity to the PSTN. Such an installed base alone guarantees that ISDN and analogue exchange lines will continue to be around for many years to come.
Even organisations that have deployed IP devices still generally require some traditional telephony for local PSTN break-out or failover, and certain value-added services (such as alarm lines) are only provided across circuit-switched connections. Most DSL services, for example (which may be used for corporate data and Internet access), require a BT analogue line as a bearer circuit.
IP access to the PSTN
Over time though, circuit switched telephony will inevitably be replaced by IP-based services, as the benefits of VoIP technology become obvious. It's worth exploring what these VoIP options are, particularly as part of a migration from traditional to IP-enabled PBXs. Material advantages can arise from making the move towards IP-delivered trunk services. You may find, however, that the biggest surprise could be that 'lower cost calls' is not the main benefit.
Internet-based PSTN services
Trunk connectivity to the PSTN using IP can be done in two fundamentally different ways; via the public Internet or via a secure, private environment.
Internet Telephony Service Providers (ITSPs) offer exchange line services across the public Internet. As an Internet-based service, there is an immediate and obvious benefit: The service becomes location independent, being available wherever there is an appropriate connection to the Internet. There are, however some issues that need to be considered.
The overall performance of the service is highly dependent on the Internet connection. Contended ADSL services may offer intermittent service degradation and only support a limited number of concurrent telephone calls. While some efforts can be made to prioritise the voice traffic over other traffic, before it is sent across the Internet, the voice traffic is generally subject to the same performance issues of the Internet connection as any other traffic (for example, large email attachments, file downloads and general web browsing). In fact, on contended connections your voice traffic may well compete indiscriminately for bandwidth with other broadband users at the same exchange.
Another main consideration revolves around security; Internet-based services may be threatened by denial of service, hacking/theft of service and eavesdropping and need to be protected appropriately.
Businesses wishing to use Internet-based exchange line services need to consider if they are appropriate for their needs. A basic guideline is that this type of service would usually suit single users and very small sites. Where consistent quality is paramount, either a PSTN or private network service is recommended.
(Virtual) Private IP PSTN services
IP voice services for medium and larger sites need to be provided across a controlled environment to ensure consistent performance. THUS provides IP Exchange Lines (IP trunks to the PSTN) as an IP equivalent to ISDN30 across its MPLS IP VPN, National Ethernet and High Speed Internet over Ethernet services. They control and prioritise voice traffic for optimal performance and security is also 'built in', as the service does not touch the Internet.
Delivering IP trunks across a multi-service network helps to 'sweat' the network asset. IP delivery brings - in the case of the MPLS IP VPN service - the benefit of location independence, which makes multi-sited voice networks far more efficient, delivering calls directly to end users, even if they work from another office location.
Less hardware is generally required to connect to IP trunks (a single Ethernet connection on an IP PBX can deliver multiple ISDN30 equivalent services), leading to reduced CAPEX and OPEX.
In summary
Migration to IP-based voice services is inevitable, however, there is scope to control the 'when' and 'how'. As part of any business plan for migration, there should be an active consideration to augment or even replace ISDN services with IP trunk connectivity, as over time vendors will scale back and then cease manufacturing the hardware to support this legacy technology.
Voice over IP is an umbrella term that covers any service which uses IP packets to transport a telephone call. As discussed, there are different options to choose from, but for companies where consistent quality and security are two key requirements, then either a PSTN or private network service is recommended.