A Protocol for carrying Authentication for Network Access (PANA) authentication system is provided. The system includes: a PANA client (PaC) which establishes, with a PANA authentication agent (PAA), a first PANA session and a second PANA session independent of the first PANA session, and transmits, to the PAA, a PANA update request packet requesting a binding of the first PANA session and the second PANA session; and a PAA which determines whether the first PANA session and the second PANA session are associated with an identical PaC in response to the PANA update request packet received from the PaC.