IP telephony is particularly susceptible to problems such as poor sound quality and failures, said analyst group Gartner, since it is a real-time application that relies on a shared network infrastructure,
Gartner said that although Multiprotocol Label Switching networks can prioritise time-sensitive data such as voice traffic, the technical measurements used to derive quality of service - such as packet loss, jitter and delay - are not sufficient to determine whether the quality of a voice call is acceptable to a user.
Instead Nigel Chisnall, technology strategist at Abbey National, has used a technique known as Mean Opinion Score to measure the quality of voice calls on the bank's IP network.
This is a benchmark for measuring quality of telephone calls, based on surveying samples of users on the quality of recorded phone conversations.
To set a benchmark on which to assess the quality of calls on the IP network, Chisnall checked call quality on a five-mile copper link across landlines in Ipswich. This gave a Mos score of 4.6.
Using voice quality assessment technology from Psytechnics, which specialises in monitoring technology, Abbey's VoIP provider, BT, implemented and maintained the Mos-based service-level agreement for voice quality at the bank.
Abbey's SLA will require VoIP voice quality to be comparable to landline quality across the entire network of 750 offices - a total of 9,000 IP handsets.
At a Burton Group conference earlier this month, Chisnall said he chose a Mos score of 3.7 and tested the network in Durham, central London and the Isle of Wight to check call quality on the IP network.
He said Psytechnics' non-intrusive technology supports continuous monitoring. "We have 400,000 calls a week and needed to check all of them," he said. "Psytechnics provides us with early diagnosis of a problem." This is used by the bank to predict where likely problems will occur.