How to differentiate between initial Access-Request at RADIUS server

Question

How to differentiate between initial Access-Request and Access-Request in response to Access-Challenge for RADIUS ?

according to RFC 2138 section 4.4. Access-Challenge; It always sends new Access-Request for access-challenge.

Answer 1

State attribute can be used to check if its Access-Request to your challenge. While Challenging, State attribute must be set and as per protocol, Client should return same state.