Application Quality of Experience (AppQoE) Overview

Application Quality of Experience (AppQoE) aims to improve the user experience at the application level by constantly monitoring the class-of-service parameters and SLA compliance of application traffic, and ensuring that the application data is sent over the most SLA-compliant link available.

AppQoE is supported on both hub-and-spoke and full mesh topologies for real-time optimized SD-WAN mode. AppQoE is implemented as a book-ended solution, where both the ends have SRX series devices or vSRX instances that run the same version of Junos OS with the same configuration.

In the real time-optimized mode, CSO pushes the SLA parameters, path selection parameters and the related configuration. The device monitors the links for SLA violation. If there is a violation, the device switches the link and sends APPQOE_(APP)_SLA_METRIC_VIOLATION/APPQOE_BEST_PATH_SELECTED syslogs to CSO. The device also aggregates and averages the SLA metrics, and sends periodic APPQOE_APP_PASSIVE_SLA_METRIC_REPORT syslog to CSO.

To monitor the SLA compliance of the link on which the application traffic is sent, the CPE device sends inline probes, called as passive probes, along with the application traffic. To identify the best available link for an application if the active link fails to meet the SLA criteria, the CPE constantly monitors and collects the SLA compliance data for the other available links. The probes that the CPE sends over the other links to check the SLA compliance are called as active probes. The active probes are carried out based on the probe parameters that you configure.

NoteĀ AppQoE impacts the CPE performance because the passive probes piggyback over the application traffic packets.

Link switching is done at the application level by the CPE device. That is, only the traffic corresponding to the application that reported the SLA violation is moved to a link that meets the specified SLA. The remaining traffic remains on the same link until those applications report an SLA violation.

You can configure traffic type profiles to specify the class-of-service parameters and the probe parameters for each traffic type. When you create an application SLA profile, you can link that with a traffic type profile and specify the SLA parameters and SLA sampling criteria for the SLA profile. The Application SLA profile is then linked to an SD-WAN policy intent, which can be deployed to implement AppQoE. For more information on the AppQoE configuration and monitoring workflow, see Configure and Monitor AppQoE.

From the Monitor > Application SLA Performance page, you can view the application-level SLA performance information and whether AppQoE is enabled. You can also view applications-level SLA performance details such as packet loss, RTT, jitter, and the number of probes.