How Cisco Keeps Quality High For Voice Calls, Part 1: Availability

September 21, 2011 - 0 Comments

Measuring the quality of voice calls that are carried across a corporate network often comes down to just two key questions:

1. Availability: Will calls go through the first time and every time?

2. Quality Metrics: How do we know how well the call sounds to all of the connected parties?

In this two-part post, I’ll describe how Cisco answers these questions through the tools and processes we use for monitoring voice call quality.

Monitoring the Availability of Voice Services

We take a multi-layer approach to monitoring the availability of voice services. At the foundational layer, , Cisco IT uses pings (ICMP) to determine if the essential voice components—such as gateways, circuits, and Cisco Unified Communications Manager (UCM) systems—are online and operational

However, pings can only help to represent the network layer of voice components. They don’t show the status of voice applications. For this deeper level of monitoring, we use the Cisco Unified Operations Manager to check whether any voice services aren’t functioning as expected. .

Synthetic tests calls are an important part in our voice monitoring solution. These test calls are performed by virtual phones, distributed globally, that continually make test calls across our environment.. These phones behave just like any employee’s phone, but allow us to verify that call routing, specific voice services, and voice connectivity over the local Cisco network and to the PSTN are all working correctly.

This type of call testing is very flexible and can cover nearly every element in a calls path. For example, we utilize test calls to monitor availability of the global voicemail (Unity Connection) and Webex conferencing access numbers. But we avoid creating unnecessary complexity in our tests. For example, we don’t do synthetic call testing end-to-end across the corporate WAN because we have better methods for validating the WAN status.

The data collected by all of this availability monitoring becomes part of our quarterly SLA reports for the Cisco IT voice services.

In Part 2: Measuring Call Quality

In Part 2 of this post, I’ll cover the metrics we use to answer the second key question—about how a call actually sounds to the participants.

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