WAN performance is measured based on metrics like latency, jitter, packet loss, and average response time. IP SLA is the solution that assists in measuring these parameters to determine network performance, monitor IP services, and troubleshoot networks.


IP SLA simulates network traffic to collect performance information in real time by sending data across network paths. You can create multiple operations to cover multiple paths. It generates and analyzes traffic either between Cisco® devices or from a Cisco device to any other remote IP device. The values provided by the various IP SLA operations can be used for troubleshooting, problem analysis, and for designing network topologies. 


The primary uses of IP SLA are to measure end-to-end performance over WAN links and to collect details for WAN performance monitoring and troubleshooting for connectivity issues within the network or between locations.


WAN Performance Monitoring


Here’s an example of WAN performance monitoring. Let’s say you’re setting up a new link to connect your new branch to the data center. Before directing production traffic across this new connection, you would want to test the link to make sure it’s working properly. In this scenario you can create an IP SLA operation to check the performance of the link and determine if the Round-Trip-Time, packet loss, latency, etc., are under control and meets the expected values.


Troubleshooting Connectivity Issues


Poor application response for a user can be caused either by the network or by the application itself. IP SLA can help with the process of elimination by providing performance stats of the network. It offers reliable values that help immediately identify a problem and save troubleshooting time.


To take another example, say, one day you find that the helpdesk has logged tickets for VoIP call drops between the head office and a branch office. To determine the cause, you would need to check the link quality with IP SLA VoIP operation and ensure jitter, latency, packet loss, and MoS are all operating as expected. If they are not, fix the detected issue(s) and then recheck the link to make sure that VoIP performance meets expectations.


How Does IP SLA Work?


After IP SLA has been enabled on the edge devices, it measures the service quality of the path from one Cisco® device to another. Monitoring is configured based on the below IP SLA operations:

  • ICMP echo (ping)
  • UDP echo
  • UDP Jitter
  • TCP connect
  • VoIP UDP Jitter
  • DHCP
  • HTTP
  • DNS
  • FTP

IP SLA Processing.png

Once you configure IP SLA, the Source Router sends a generated packet over the network to the Destination Router. The Destination Router, after receiving the packet, sends a response based on the IP SLA operation. The Source Router then calculates the values for the metrics related to the IP SLA operation and reports on link quality.

 

An IP SLA monitor such as SolarWinds® VoIP and Network Quality Manager collects IP SLA data from devices, triggers alarms if certain thresholds are being crossed, visualizes the data in graphs and tables, and compares the readings to historic data.

 

Some highlights of VNQM in troubleshooting and monitoring WAN/application performance are:

 

  • Monitor WAN network performance using IP SLA technology that’s already built into your existing Cisco routers
  • Visualize site-to-site network performance on a clickable, drill-down map
  • Discover and automatically setup Cisco IP SLA-capable network devices with specific IP SLA operations
  • Quickly review WAN performance to determine the impact on key applications
  • View at-a-glance WAN performance with the Top 10 IP SLA dashboard
  • Monitor VoIP performance statistics, including MOS, jitter, network latency, and packet loss