code: boolean checkReplay(int seqNo, long guessedIndex) {
  		// compute the index of previously received packet and its
  		// delta to the new received packet
  		long localIndex = (((long) this.roc) << 16) | this.seqNum;
  		long delta = guessedIndex - localIndex;
  
  		if (delta > 0) {
  			/* Packet not yet received */
  			return true;
  		} else {
  			if (-delta > REPLAY_WINDOW_SIZE) {
  				/* Packet too old */
  				return false;
  			} else {
  				if (((this.replayWindow >> (-delta)) & 0x1) != 0) {
  					/* Packet already received ! */
  					return false;
  				} else {
  					/* Packet not yet received */
  					return true;
  				}
  			}
  		}
  	}
docs: Checks if a packet is a replayed on based on its sequence number.
  
  This method supports a 64 packet history relative the the given sequence
  number.
  
  Sequence Number is guaranteed to be real (not faked) through
  authentication.
  
  @param seqNo
  sequence number of the packet
  @param guessedIndex
  guessed roc
  @return true if this sequence number indicates the packet is not a
  replayed one, false if not