The following image illustrates the 6 principle factors effecting the quality of any VoIP telephony deployment. We have shown the factors associated with the part of the end-to-end network path from end-user/consumer on the left to employee/agent on the right. Essentially we can break this into four legs of the journey: First, the long leg,"1000s of miles", between the consumer and the last internet link to the contact center called "the last mile". Then "the last 100m" representing the internal office network of the contact center. Finally "the last metre" to the device of the employee/agent.
The quality and location of the application hosting that processes decisions made in IVR or based on call events will clearly have some impact on latency. As volumes and complexity increase, this can start to have a large impact, particularly for real-time actions like pushing data to an employee with a call.
Far more significant though is factor number two: the quality and location of the media channel and signalling hosting for telephony. If the employees are connected to SIP registrations on SIP proxies and RTP media channels that are far away in the global network, then this will inevitably have a marked impact on the quality of calls. Delays will occur and audio quality will be impacted. Employees and end-users will perceive calls as being bad experiences.
The quality of telecoms routes is also a major source of latency and quality issues. This applies equally well to inbound and outbound traffic even though the infrastructure and transport is quite different for the two cases. Looking at inbound first, if you purchase telephone numbers that are routed in a network that is far (in ping time and number of hops) from your consumers and your call processing platform, then you cannot avoid problems. Similarly, if you route outbound calls through termination networks that are not optimised then you will also have calls of poor quality. We monitor quality on over 40 carriers and 300 service providers and the differences are immense. There is a reason why cheap international dialing plans are cheap - they use such termination routes that are not very highly sought after. For a business, this is not an option. We route only on the top 4 to 10 carriers in each territory, i.e. for each telephony destination.
The last mile of the internet connection to your contact center or offices also has a big impact. In particular, if you are on a part of the internet network that does not offer high bandwidth symmetric connections, then this can effect call quality. It is vital to ensure that you have sufficient upload and download bandwidth that is actually available to you - calls are two-way, highly, real-time media streams with two-way IP signalling overhead: upload is just as important as download.
Finally the last 100 metres of your internal network combined with the choice of phone devices will also have a huge impact on call quality. Basically, the more dedicated and optimised the traffic across your network to phone devices, the better will be the voice quality. You can read more about the relative quality of device - network combination in this article: Comparing and selecting the right device and network deployment