Chapter 3: Adaptive Path Control

Overview

Unlike BGP, which bases routing decisions on network topology and a set of predefined tie-breaking rules, the Avaya CNA system combines actual observed data and your input about cost and performance to identify the best route between a server and a particular prefix.

Data is obtained from four sources:

• an accumulation of random, web-surfer-initiated single pixel GIF measurements (see Chapter 4: Server-Based Measurement of the CNA Basic Monitoring Guide)
• regularly scheduled active probes of a specific host in a specific prefix (see Chapter 4: Server-Based Measurement and Chapter 2: Collecting Endpoint Addresses of the CNA Basic Monitoring Guide)
• edge router SNMP agents, which are polled for information about BGP and interface status, and traffic loads
• your input, using CLI commands

You can choose to operate the CNA system in report-only mode, in which the device will monitor traffic and tell you what routes it would have chosen, but it will not actually assert its decisions to your network routers.

Initially, you may prefer to just review these reports, make your own decisions, and take your own action.

But in time, as you gain confidence in the CNA system, you can configure the device to allow the CNA decision-maker process to override BGP-determined routes and designate a specific ISP link as the best path for returning data to a prefix, thereby improving your network (e.g., less delay, jitter, and loss).