Our last blog discussed about the Cisco IPSLA and VoIP monitoring and how these statistics are helpful in monitoring VoIP networks.
VoIP monitoring using Cisco’s IPSLA is available as an Add-On feature to NetFlow Analyzer Professional and Professional Plus editions. NetFlow Analyzer monitors the key performance metrics like Jitter, Latency, Packet Loss, etc of the VoIP network using IPSLA to determine the VoIP network’s health thus ensuring uptime. The combined VoIP and NetFlow based statistics helps users by not just telling the VoIP network quality but also by pointing the reason for any quality depreciation.
How it works :
NetFlow Analyzer relies on Cisco’s IPSLA for monitoring VoIP. The prerequisite for VoIP monitoring is that the devices should be Cisco with IPSLA agent enabled at the source and the destination device with IPSLA responder enabled. All Cisco routers from IOS Version 12.3(14)T supports VoIP QoS metrics.
Cisco IPSLA simulates a UDP jitter operation where UDP packets are sent from the source device to a destination device. This simulated traffic is used to determine the jitter, packet loss and latency. This data is gathered in multiple tests over a specified period to identify how the network performed at different times. This information helps in network performance assessment, troubleshooting, and continuous health monitoring.
Adding a VoIP Monitor in NetFlow Analyzer:
Prerequisites:
A Cisco router with IOS version 12.4 or later at both the source and destination.
How to configure VoIP Monitoring in NetFlow Analyzer:
The NetFlow exporting routers should be detected and monitored in NetFlow Analyzer. Once this is done, make sure the SNMP read and write community are configured on the device. The next step is to enable SLA responder on all the destination routers for which you wish to monitor VoIP performance. Given below are the command which will enable SLA responder on the router:
Router(config)#ip sla responder
Now enabling VoIP monitors on the source routers from NetFlow Analyzer is next step. To add a VoIP Monitor, click on VoIP Monitors at the top right corner of GUI. Under Settings tab, enter the monitor name and select the Source Router with relevant interface. Specify the destination router IP address and submit the details. You will see the summary of the monitor you are about to configure. Now click ‘Apply to device’ to submit the details to the device. This will take few seconds to configure. Refresh the page after few seconds and you will see the new monitor.
In case if you want edit the parameters for VoIP Monitoring like (Call Settings and Threshold) before you add new monitor, click on Call Settings under Settings Tab in VoIP Module. The following things can be changed on Call Settings based your company SLA’s (Service Level Agreements):
Destination Port – Specify the VoIP UDP port to which VoIP Monitor sends simulated traffic to generate performance metrics. The default port number is set as 16384. You can specify a port in the range of 16384 – 32766.
Simulated VoIP Codec – The VoIP jitter codec decides the type of traffic that VoIP Monitor simulates over your network.
Operation Frequency – The operation frequency is the frequency with which QoS metrics are collected by the IPSLA agent on your network to determine performance.
Operation Timeout – The operation timeout is time to wait for the response from the responder / destination device in milli seconds.
Type of service – The Type of Service octet allows you to set precedence levels for VoIP traffic of the IPSLA operations.
MOS Advantage Factor – The advantage factor is a measure, on a scale of 0 to 20, of the willingness of your VoIP network users to trade call quality for convenience.
The threshold settings will allow you to specify different thresholds for various parameters like (Jitter, Latency, MOS, Packet Loss, RTT) which suit your company SLA’s (Service Level Agreements). Alerts are triggered based on the thresholds configured so that you can take corrective actions in time.
We will come back with information on the type of reports VoIP monitoring reports that you can generate in NetFlow Analyzer on our next blog.
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Regards,
Praveen Kumar
