Duplicate Accounting Records

[Farid]

Hello,   I have a question about session-id in accounting table (using mysql):             It is appear that this field could not be unique over the table, I supposed that NAS's reuse packet id's on defined period.             I found some duplicated records on the accounting table with same session id, and sessiontime on very close time for the same user.   This cause a problem in calculating the login hours for users, I use SQL counter named Total-Time-Limit to limit some users to a predefined connection hours.     Is there a way to force freeradius to eliminate duplication or configure NAS server to not send redundant packets?       Thanks, Farid Mohammed