NMS come in many flavours, from simple MibBrowsers (available free in the Net inversions from professional by iReasoning to wanabe Mama-Papa concoctions that crash on addresses outside 192...) to full blown custom jobs running a country!!!
Here a semi-custom NMS is described. The design is based upon a model first devised in the 80's and still valid today. Starting form the 7 layer OSI model we divide it into two parts, layer 4 down and layer 4 up. Downwards we have all transport mechanisms, RS232C, RS484, USB, LAN, last added Bluetooth etc.. and upwards the proprietry applications for controlling different pieces of equipment. The two parts share a common interface, so plug and mix.
The interface is an internal RS232C protocol. Why because in the 80's RS232C and IBM coax ruled the world. XEROXv2 and the new TCP/IP were disputing the rule of the LAN. In many cases the XEROX Lan was just used to transport the RS232C data frames from point to point (BayCommunications). Since, even today, clients demand RS232C (native or USB) to control equipment it is still a suitable interface to provide on the company applications. The Other (blow layer 4) part handles all the physical communications.
So this is our NMS, basically a customisable trap receiver (and handler) that pull's in the specific equipment applications to GET-SET usage of the device.