SA Parameters
Sequence number counter:
- 32 bits in AH or ESP header for outbound packets
- incremented by 1 whenever SA is used
- used to detect replay attack
- SA renegotiated after this field overflows
Sequence number overflow: set when the sequence number overflows
Antireplay window: used for incoming packet processing
- sliding window size must be greater than 32
- received packet must be new and fall inside or right of window