Port forwarding error!!!!!

jester, if you do port forwarding correctly, it will allow you to access it both from internet and LAN. I've done this before as many others did, there is really no difficulty in it if you set it right. Here is the exact step by step instructions for your exact model "Billion Bipac-5200"

www.portforward.com/english/routers/port.../Bipac-5200/HTTP.htm

As it is shown, you have to setup a "Virtual Server", not DMZ. Just replace port 80 with port 8000 (as you said). Do as shown and tell us what happens. Again, the IP of the DVR should remain 192.168.2.2

DMZ? Do you have the device on a seperate subnet or vlan than the rest of the network?

Also, does your Billion router have an extra inside interface on it?

No, the device is on the same Subnet and it is not having a separate interface ,its just a isp provided modem cum router .
I will once again try to configure the virtual server as per s0lo.
I really thank every one for their response.

very thing went fine and i can now access the DVR ,but its throwing an error msg "device busy"

What is throwing "device busy"? The DVR? the router? And on what screen/GUI/CLI is it throwing it? Please elaborate.

I believe the error message is thrown from DVR ,i use the browser to connect to the device so its GUI screen.