Active Passive Networks Monitoring

VoIP Network Monitoring Approaches: Which Way to Go?

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As voice networks evolve into all IP frameworks and with the understanding that the organization’s voice networks become dependent on many factors which are not directly correlated with the voice network itself, it becomes clear to any IT organization that proper monitoring tools are required to maintain the quality of experience of the end users. But what is the right approach for monitoring the voice network?

Active Monitoring

Active Passive Networks MonitoringIn the past, in order to properly conduct end-to-end quality monitoring, you had to incorporate testing equipment into your environment, inject VoIP traffic on top of the existing VoIP network, collect traffic statistics and then start troubleshooting the problem. This method was known as “Active Monitoring”. But this approach had some significant drawbacks. It could not, for example, track existing calls running in the network. If an end user complained about a problem, there was very little that could be done to manage this complaint effectively.  Another problem is that you had to install additional hardware in the locations in which you wanted to test the traffic. In large-scale deployments, this could render the costs of a monitoring solution unacceptable. Active call generators would have to be moved from one place to another which would clearly cause a delay in troubleshooting and resolving the problem. To illustrate, if there was a complaint in New Jersey but the call generator was currently placed in Boston, the call generator would need to be shipped to New Jersey before the troubleshooting process could begin. On top of that, the extra probe adds more traffic to the underlying network which tacks on another factor of uncertainty. Will the existing network traffic running the call generator be affected by this addition? Will it further worsen the existing problems?

Passive Monitoring

It was clear that an alternative means of monitoring was required and this led to the introduction of passive monitoring. “Passive Monitoring” is a method in which a network is configured to mirror ongoing traffic to a passive probe which then looks at the entire set of the packet stream and can provide statistics based on the collected information. This approach clearly solves the problem where there was a need to check a specific end user’s complaint. It also does not introduce additional traffic load to the network. However, there are still some problems with this approach. Hardware probes still have to be placed in each location that needs to be monitored. For large scale enterprises (and in the case of New Jersey vs. Boston example provided above) this remains a problem. Additionally, you still have to configure the IP elements in the network such as switches and routers to mirror the traffic to another location. What about a scenario in which the entire set of the physical ports on the switch is already exhausted. Another switch might be required just to do the monitoring!


Probeless Monitoring

In the last few years a new solution trend is catching on fast. The new solution is similar to the passive approach but takes it to the next step for better monitoring. The idea is that each of the active network elements provide statistics to a higher management layer which can then provide a service level view as well as statistics with very fast troubleshooting schemes. With this approach, there is no need to add additional hardware to the network. There is also no need to mirror the traffic from the existing switches and routers. You only need to be able to interface with existing provided interfaces of the network elements to receive an end-to-end view.


This would appear to be the ideal solution. But is this really the case? Well, it is no doubt a major improvement over past solutions but there are still some issues that remain. Firstly, there is the issue of how you can get a full end-to-end view with heterogeneous network components? Secondly, there are some situations where passive monitoring cannot help and Active Monitoring is preferable. For example, if no traffic exists on the network, how do you know if there is a problem? You want to be sure that once a call is placed on the network that it will work. By the time the end user complains, it is too late. Active Monitoring can validate that calls from specific locations will indeed work. Also, the active monitoring solution can validate capacity planning. The IT CIO planned for a certain network capacity, but how can he/she be sure that the traffic load will flow without problems? Here, Active Monitoring is a useful methodology.


The Combined Approach

What really is required here for an IT organization to effectively monitor the quality of the voice network is a combined approach of Active AND Passive monitoring. What is needed is a comprehensive quality monitoring tool (such as AudioCodes SEM) that passively integrates with all of the company’s voice network elements as well as with UC applications such as Microsoft Lync. Such a tool can provide a full end-to-end monitoring view of network elements (IP-Phones, gateways, SBCs, soft clients, etc). Additionally, active probes can be embedded in the network in order to generate synthetic VoIP traffic according to predefined capacity loads. In this way, administrators can make sure that the deployment meets the requirements of the planning. The comprehensive quality monitoring tool, which integrates with both the active network elements and the embedded probes, will be able to simultaneously capture both real time and synthetic traffic, allowing for quick root cause analyses of voice network problems and assuring that the voice network can manage the traffic for which it was designed.

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