Ratio between Number of Radius Accouting Server and Number of Radiuis Authentication Server

Is there any recommendation on Ratio between number of radius accouting server and number of radius authentication server, if accouting and authentication are executed by different hardware platform ? Is there any way to estimate the burst rate of radius protocol packet in ISP network? thanks in advance. Joe ____________________________________________________ Yahoo! Singapore Answers Real people. Real questions. Real answers. Share what you know at http://answers.yahoo.com.sg