1. A computer-implemented method of real-time discovering and monitoring of a data communications network having a plurality of multi-vendor, multi-class, multi-layer network devices, comprising: receiving properties command information about attributes of network devices to be discovered, said properties command information comprising non-standard configuration attributes, vendor specific attributes, and credentials including user names and passwords for each of said network devices; sending a plurality of first discovery commands to ping a plurality of network addresses within a selected network address range, the first discovery commands being formed to query each of said plurality of network devices within said selected address range and cause each network device that responds to respond with its network IP address and a corresponding MAC address; receiving responses to said first discovery commands from responding network devices and determining from the responses a packet type for each responding network device; sending a second discovery command to the network address of each responding network device, said second discovery command comprising said credentials for said each responding network device and being formed to query said each responding network device about information stored in each such network device as to end-to-end Open System Interconnect Level 2 and Level 3 interconnections between the responding network device and other network devices, and formed to discover first characteristics including device identity, device type and information on an installed hardware and software operating system for said each responding network device; analyzing responses to said discovery commands from each of said plurality of network devices to discover said first device characteristics and to determine a first network configuration; repeating said sending said first and second discovery commands, said receiving responses to said discovery commands and said determining said packet type to discover second characteristics of each of said network devices and to identify second interconnections between each network device and other ones of said network devices to determine a second network configuration; and comparing the first and second characteristics of said network devices and the first and second network configurations to identify and track any changes in said network devices and network configuration.