Once unproven technology deployed by only the largest organizations, Voice over Internet Protocol (VoIP) is becoming an everyday responsibility of many IT and network administrators. Small and medium-sized businesses in particular can reduce their telecommunications costs and increase flexibility by converting an unwieldy TelCo/PBX problem into just another service on the network. The biggest remaining challenge for VoIP administrators regardless of the number of extensions is assuring high call quality.
While there has been significant progress made in improving the quality of service for VoIP calls, quality is still generally lower than that provided by Public Switched Telephone Network (PSTN) networks. Corporate IT and accounting are drawn to VoIP based on the economics, but to most users, a phone is a phone. They expect the quality of PSTN. As a result, network administrators looking for successful user adoption of a VoIP system must keep a close eye on the actual call quality users experience.
VoIP Metrics that Matter
There are many associated metrics, but the ones which most affect the perceived call quality are jitter, latency, packet loss and – most importantly – MOS score. MOS, or Mean Opinion Score, has been measured for decades by humans subjectively assessing the quality of PSTN calls. For VoIP calls, an analogue is calculated based on several measurements. The values are slightly different for each vendor because hardware, or even different codecs on the same hardware, affects perceived call quality differently. For this reason, all four elements should be measured, with MOS a great indicator of when admins will start seeing helpdesk tickets about quality, and the related jitter, latency, and packet loss used for troubleshooting. These are the best metrics for troubleshooting the most common source of VoIP issues: the underlying (often shared) network.
Of course, the best approach to assuring VoIP call quality is with a capable VoIP monitoring solution. They provide constant monitoring of all elements of the VoIP infrastructure, WAN link quality, historical tracking, alerting, call forensics, multivendor support and more. Most VoIP call managers already automatically log call metrics as part of the CDR (Call Detail Record), but they do not monitor all the intermediate network components involved in each call path. There are several great solutions available, including SolarWinds VoIP Network Quality Manager. Cost for these solutions has decreased over recent years and VoIP administrators should rely on them for any decently sized or mission-critical VoIP environment.
Measure VoIP Quality – Even on a Budget
As a scaled-back approach, administrators can use the call manager’s CDR records to monitor the quality of the swarm of VoIP calls on their networks and troubleshoot call issues. Most call managers record call data to a central database, and periodically dump completed call records to export files for analysis. The challenge is that these files can be tedious to acquire, and difficult to analyze. For illustration, here are just a few of the 90-plus elements included in a typical Cisco Call Manager CDR file:
globalCallID_callManagerId, callingPartyUnicodeLoginUserID, origPrecedenceLevel, origMediaCap_g723BitRate, destMediaCap_maxFramesPerPacket, callingPartyNumberPartition, joinOnBehalfOf, outpulsedCalledPartyNumber...
Additionally, the data is broken into many short timespan files which must be individually retrieved and joined together. Somewhere in the files are lists of calls and their quality and pertinent detail, but it’s a challenge to search, especially in the middle of a deluge of support tickets. An admin could develop a job to automate collection and a script to grep out useful information, but there are tools available to make this much easier.
One great free tool is SolarWinds Call Detail Record Tracker, which supports Cisco CallManager 7 and 8. It automatically downloads CDR data and provides an easy-to-use search tool to wrangle the CDR details into something useful. Here’s an overview of how to use it to access and analyze CDR data on a network.
After the brief install, SolarWinds CDR Tracker opens with a setup screen where an admin can enter the details for the call manager server. Generally, the CFR export files are hosted via SFTP on a root, CUCM or CUCM/vX path.
A test button is included to verify the settings before going on to the data load step. Once the connection to the CDR server tests successfully, click “Save” and SolarWinds CDR Tracker will begin to download the call record data. (If an admin has thousands of calls or his link is slow, this may take a couple of minutes). Once the calls are loaded, the call records list will appear, including all the calls recorded by the call manager:
In this view, an admin will receive a scrollable call list which includes all the important details of each call. Call origin and destination details, including phone number and IP, call duration details, call status, MOS score, and failure and redirect details are all included. Sort by column, and calls with issues are highlighted for easy identification.
From this screen, an admin can quickly search long lists of calls based on a number of elements. Search for all calls below a reported quality (MOS), by status to quickly find calls that failed, discover calls with a specific termination cause, and narrow further by date or time range. Quickly address legal or HR requests for call details to or from a specific number. Best of all, admins can combine the search elements together to zero in on the most pertinent data. For example, here’s a view of all recent calls with a critical MOS score:
The greatest challenge of managing a VoIP system is not its initial deployment, but the ongoing management of the network on which it operates. If the overall network is having performance problems, this will often be the cause of VoIP issues and is why VoIP management software is often used in conjunction with software for network monitoring and/or a bandwidth monitor.
Author Bio: Patrick Hubbard is a Senior Technical Product Marketing Manager and Head Geek at SolarWinds, an IT management software provider based in Austin, Texas. He joined SolarWinds in 2007 and combines 20 years of technical expertise with IT customer perspective to create geeky content that speaks to fellow networking and systems professionals. Patrick’s previous roles have included product management and strategy, technical evangelism, sales engineering and software development in Austin high-tech and Fortune 500 companies.
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