VoIP

     

    Cisco IPSLA monitor or VoIP monitor comes as an add-on feature in NetFlow Analyzer and requires license to run. NetFlow Analyzer continuously monitors the key performance metrics of the VoIP network to determine its health. The parameters measured include Jitter, Latency, Packet Loss etc.

    Jitter: Jitter indicates a variation in delay between the arriving packets (inter-packet delay variance). Users often experience uneven gaps in speech pattern of the person talking on the other end, and sometimes there are disturbing sounds over a conversation coupled with loss of synchronization etc.

    Latency: The delay measured is the time taken for a caller's voice at the source site to reach the other caller at the destination site is called as latency. Network latency contributes to delay in voice transmission, resulting in huge gaps between the conversation and interruptions.

    Packet Loss : Packet loss is a measure of the data lost during transmission from one resource to another in a network. Packets are discarded often due to network latency.


    MOS: The jitter codec determines the quality of VoIP traffic and each codec provides a certain quality of speech. The Mean Opinion Score is a standard for measuring voice codecs and is measured in the scale of 1 to 5 (poor quality to perfect quality). The quality of transmitted speech is a subjective response of the listener.

    How it Works

    NetFlow Analyzer primarily relies on Cisco's IP-SLA for monitoring the VoIP and the prerequisite therefore is, that the device should be a Cisco Router and must have IPSLA agent enabled  on it. From IOS Version 12.3(14)T all Cisco routers support monitoring of VoIP QoS metrics.

    Cisco's IPSLA, an active monitoring feature of Cisco IOS software, facilitates simulating and measuring the above mentioned parameters to ensure that your SLAs are met.

    Cisco IP SLA provides 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, the round-trip-time, packet loss and latency. This data is gathered for multiple tests over a specified period to identify how the network performs at different times in a day or over a few days. The VoIP monitor gathers useful data that helps determine the performance of your VoIP network, equipping you with the required information to perform network performance assessment, troubleshooting, and continuous health monitoring.

     

    How to set up a VoIP Monitor?

    Prerequisites

    When you want to test a link from your office to another location, you need  a Cisco router ( IOS version 12.4 or later )  at each end.

    Steps to set up the monitor

    Using NetFlow Analyzer, you can now monitor the voice and video quality of a 'call path'. Call path is the WAN link between the router in your main office and the one in the branch office that you want to monitor.

    Step 1 :  Export NetFlow from the router in your LAN to NetFlow Analyzer. And make sure the  snmp read and write community are configured properly, for that router.

    Step 2:   Enable SLA responder on the destination device you wish to monitor, Steps are detailed below.
      

    1. Open a CLI session on the destination router and enable the EXEC mode as follows: 
             
      Router>enable
       

    2. Start the global configuration mode:

      Router#configure terminal
       

    3. Enable the IP SLA responder:

      Router(config)#ip sla responder
       

    4. Repeat the above steps for all the destination routers on which you want to monitor VoIP performance.

    Step 3: Selecting the Call Path ( Source and Destination Router )  to be monitored:

    1. Click on the Add Icon   on the right top and enter a name for the monitor.

    2. Select the source router from the list of routers discovered in NetFlow Analyzer, and select the relevant interface.

    3. Specify the destination router either by using the 'Search' option to pick from the discovered routers, or use the 'Add'specify the IP address of the destination router and submit the details.

    4. 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 to see the new monitor. The data will be collected every hour, from the time you have configured.

    To edit any of the configuration details, go to the respective template, make the changes and save the details. When you create a new monitor, the updated values take effect. When the configuration is complete, the router starts collecting the data at the specified frequency 60 seconds ( default value). NetFlow Analyzer updates this statistics (collected data) every hour and the reports are generated after one hour of configuration.

     

    WAN Monitors:

    The WAN Round Trip Time monitoring feature in NetFlow Analyzer is an add-on module and requires license to run. The WAN RTT monitor is used to monitor WAN availability, Latency and Quality of Service. Alerts are triggered when the set thresholds are violated, enabling the administrators to attend to the fault in no time.

    The WAN RTT Monitor uses Cisco IOS IP Service Level Agreements(SLAs) to monitor latency between two locations, therefore either of the location, monitored using WAN RTT monitor, should have the Cisco router (IOS version 12.4 or later) with the IPSLA agent. The IPSLA agent enabled location will act as the source while the destination can be any IP in the other location.

     

    Getting Started

    The WAN Round Trip Time(RTT) Monitor of NetFlow Analyzer is an add-on tool that monitors latency between two locations. The WAN RTT monitor measures round trip time and helps resolve poor WAN performance. It is also helpful in monitoring Quality of Service(QoS) across WAN links provided by your Internet service provider(ISP) and alerts are generated when the set threshold limits are violated.

     

    Adding Monitors:

    1. Click on the Add Icon   on the right top and enter a name for the monitor.

    2. Select the source router from the list of routers discovered in NetFlow Analyzer, and select the relevant interface.

    3. Specify the destination IP address which an be any IP in the destination location and click on add icon   to add the destination.

    4. Once done click on Save to save the monitor.

     

    All Monitors:

    The WAN tab under IPSLA list all the WAN monitors by Default with there Status, Max Rtt, Average Rtt, Min Rtt, Voilation and Availability. You can Click on the monitors to get the details on each monitors.

    The "All Monitors" tab displays all the available paths that are being monitored. By clicking the path name you can view path, and threshhold details along with NetFlow Traffic reports of the routers. The graphs indicate threshold violation percentage, Error Percentage and Round Trip Time. You can also add, remove and view the history of monitors created so far using "All Monitors" tab.

    You can do the WAN monitor settings from the Settings -> Monitoring tab.

     

    Video Monitors

    About IPSLA Video Operations

    With video traffic becoming all pervasive in the network it becomes increasingly important to consider the impact of video on the network.

    Before going for new video end points, it is important to assess the video handling capabilities of the network. This can be done by means of simulation. This involves creating a situation which the network will be subject to conditions that are similar to having real-time video traffic. These results help in assessing the performance of video traffic and baselining performance-based requirements for deploying video.

    The networking landscape is changing quite dynamically. This makes constant assessment is a necessity in order to fulfill the ever-growing demands on the network.

    IP SLA - Video operations acts as a stress tester on the network. One can validate the effect of rich media applications on the performance of other applications on the network. This helps a great way in ensuring that the network can handle video traffic smoothly and effectively.


    Benefits:
    IP SLA video operations offers the following benefits:

    • Understand IP service levels - By monitoring some critical parameters, it is possible to understand the different IP service levels in the network.

    • Increase Productivity - A network that offers the best service levels has a direct impact on the productivity levels since the ultimate use for implementing voice and video applications is to improve productivity.

    • Lower Operational Costs - Applications with best-in-class service levels help in cutting costs involved in logistics thereby cutting operational costs and boosting operational efficiency.

    • Lower frequency of network outages - When troubleshooting is accelerated, the downtime can be controlled. Lower downtime means cost savings.

    • Network Readiness Assessment - Video operations for IP SLA acts as a tool to assess if the network is ready for deploying video.

    • Network troubleshooting - When the network performance takes a hit, there are disturbances that need to be identified and corrective action needs to be taken. IP SLA VO gives you critical metrics that help you achieve this objective.

     

    IPSLA -Video Operations Metrics

    Here are the broad and specific categories of data that NetFlow Analyzer is capable of displaying:

    Jitter:
    Under jitter, the following subtypes are displayed:

    • Maximum positive jitter

    • Maximum positive jitter

    • Minimum positive jitter

    • Average positive jitter

    • Maximum negative jitter

    • Minimum negative jitter

    • Average negative jitter

    • Average of positive and negative jitter

    • Inter arrival jitter at source and destination

    • Latency: Maximum, minimum and average

    • Packet information: Number of delayed packets, number of packets skipped, number of packets out of the sequence and the number of packets lost.

     

    Prerequisites for IP SLA video operations:

    • Both the source and responder devices for the IP SLAs video operation must be capable of providing platform-assisted video traffic generation and reflection.

    • Time synchronization, such as that provided by Network Time Protocol (NTP), is required between the source and the responder device in order to provide accurate one-way delay (latency) measurements.


    Restrictions for IP SLA video operations:

    • This feature is supported only on Cisco devices that are capable of generating platform-assisted video traffic and reflection, such as the Cisco Catalyst 3560, 3560-E, 3560-X, 3750, 3750-E, and 3750-X Series switches.

    • IP SLAs video operations do not support Round Trip Time (RTT) traffic.

    • Because IP SLAs video operations support only one-way traffic, an operation and a responder must be configured on both the source and responder and both devices must support SNMP access.

    • IP SLAs video operations are supported in IPv4 networks only.