Network recovery
Controlling edge routers
CNA maintains a BGP peering with every edge device it needs to control. It is configured as a route reflector to the edge devices, which allows it to (1) receive state of the routing table from the edge devices, and (2) send BGP control messages to the edge routers pertaining to destinations it needs to control. The edge routers need to be configured so that route updates from CNA are given priority over other route updates regarding the same destinations. This is accomplished by giving either a higher Weight or a higher LOCAL PREF to updates coming from CNA. If given higher Weights, the route updates’ high priority status will only apply on the edge routers themselves. If given higher LOCAL PREF, then the high priority status of these route updates will apply across the entire Autonomous System.
Some router vendors, such as Juniper don’t support weight. For routers from those vendors, LOCAL PREF is used to give high priority to routes updates sent by CNA.
In the scenario shown in Figure 94: Headquarters CNA deployment – Measurement plane on page 347,
Translating low level statistics to an Application Performance rating
See CNA Application Performance Rating on page 254 for a description of the CNA Application Performance rating (APR) based on application models.
Signaling traffic uses TCP and consists of short transactions. The CNA application model that best captures the characteristics of signaling traffic is the enterprise application model. The enterprise application model takes into account the impact of delay and loss on the TCP transport protocol. It also assumes short transactions and uses transaction delay as the measure of performance, which is translated into the
Configuration and deployment details
Appendix A: CNA configuration and deployment on page 359 provides detailed procedures for configuring CNA.
