Smart Policy Routing

What Is Smart Policy Routing?

Smart Policy Routing (SPR) is a dynamic route selection mechanism that assesses link quality in real-time and chooses the best path to forward service data based on service quality requirements. By implementing intelligent traffic steering, SPR ensures that user services remain unaffected by variations in network quality, thereby safeguarding and enhancing the user experience.

Why Do We Need Smart Policy Routing (SPR)?

As network services become increasingly diverse, ensuring link quality is crucial. Users now focus on service availability, such as response speed and quality, which traditional routing protocols can't guarantee. These protocols only ensure that a route is reachable, without considering the quality or ability of the link to forward packets. This can negatively impact or disrupt services. SPR addresses these challenges by proactively detecting link quality and selecting the optimal link for data forwarding, thereby minimizing the impact of network quality on user experience.

How Does SPR Work?

Smart Policy Routing (SPR) operates by utilizing a link quality detection function, where a device continuously monitors the delay, jitter, packet loss rate, and Composite Measure Indicator (CMI) of service links. Different services have varying requirements for these indicators, and thresholds are set for those that are critical. When any indicator exceeds its threshold, a link switchover is initiated.

If no optimal link is available, the device resorts to using a standard route for traffic forwarding.

Application of SPR

In the following scenario, an enterprise branch connects to a data center using two Internet Service Providers (ISP1 and ISP2) and a 3G emergency link. RouterA connects to ISP1 via link group "group1" and to ISP2 via "group2." ISP1 offers high-quality but expensive services, while ISP2 provides cost-effective but lower-quality services. The data center and the branch exchange voice, video, FTP, and HTTP services. Due to the high connection quality requirements of audio and video services, group 1 and group 2 serve as the primary and backup link groups, respectively. Since the criteria for connection quality are low for FTP and HTTP services, group 2 and group 1 serve as the primary and backup link groups, respectively.

An SPR-enabled device performs several operations to manage voice and video services:

• 1. Switching to Backup Link: If the link quality from group1 doesn't meet the requirements for voice and video services but group2 does, the device switches to group2 after the flapping suppression timer expires.

• Returning to Primary Link: If group1's quality improves, the device switches back to group1 after the timer and an additional switchover period.

• Comparing Link Quality: If both groups fail to meet requirements but group1 is better, the device switches back to group1 after the timer and switchover period.

• Continuing with Backup Link: If group2 is better, the device continues using it.

• 2. Selecting Optimal Link: If neither group1 nor group2 meets requirements but are still available, the device selects the link with the best CMI.

• 3. Using Emergency Link: If all links in group1 and group2 are unavailable, the device uses the 3G emergency link.