How to write a mathematical model for the Radius network authentication protocol?

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I understand that the question is possibly INCORRECT and WRONG, but still. I am writing my graduation thesis on the topic "remote authentication on network devices based on Astra Linux OS". For authentication, I decided to consider Radius: I threw freeradius + mysql + daloradius on Astra. The task is extremely trivial and simple. But now, when it came to compiling the Explanatory Note, the task arose to CREATE (DRAW FROM THE FINGER) a Mathematical Model or Analytical Model of my work (i.e., the work of the RADIUS protocol). Here I read Kerberos, very good mathematical description, but with Radius I'm still completely confused ..
Does anyone have any ideas ?? I will be grateful to you!