whether i have to enable DMZ in order to access the device in the internet ????????
Typically no, on usual ISP routers, you don't have to configure DMZ, the DVR can be just a normal IP on your inside subnet. But I'm not sure about the specifics of the Billion router, it might need DMZ just because this is the way it works. So you might want to check the manual for it. By the way, what is the model number of your router ?
The router provided by my ISP is Billion Bipac-5200,
Breaking the issue and making it simple , need to access the DVR both in LAN and internet .
I have configured DVR in different work place with a different scenario ,need to access the device only in internet .But now the issue is little bit tough.