Measuring Performance to Remote Sites

To optimize WAN performance, the CNA system needs to actively probe each endpoint at regular (user-defined) intervals in order to measure packet transit times over all available links to that site. A variety of routing techniques can be used to direct this measurement traffic correctly:

• Loose Source Record Routing--or LSRR, may work in certain network configurations and requires the least amount of additional effort to correctly send probe traffic to remote sites; see the section “Measuring with LSRR.”
• Policy-based Routing--or PBR, requires additional configuration on the CNA system as well as the edge routers, but can adapt to the widest range of network configurations; see the section “Measuring with Policy Based Routing.”

Each of these three routing techniques complements the CNA system’s active probing mechanism. Active probing requires that a device at the other end of the connection (the VPN gateway or some other device) respond to either an ICMP echo request or a TCP connection request at regular intervals.

See Chapter 5: Configuring Agent-Based Measurement in the CNA Basic Monitoring Guide.