Makefile sr_main.c:
	 -I INTEGER -- ICMP query timeout interval in seconds (default to 60)
-E INTEGER -- TCP Established Idle Timeout in seconds (default to 7440)
-R INTEGER -- TCP Transitory Idle Timeout in seconds (default to 300)
-n integer -- enable the nat-I INTEGER -- ICMP query timeout interval in seconds (default to 60)
-E INTEGER -- TCP Established Idle Timeout in seconds (default to 7440)
-R INTEGER -- TCP Transitory Idle Timeout in seconds (default to 300)
-n integer -- enable the nat

sr_router.h sr_router.c:
	    add the initiation of the nat table.