Metasys N2:
Metasys N2 was developed by Johnson Controls as a network to interface their various devices and controllers. It is on the physical layer RS-485 set of data communications standards and supports 9600 baud, 8 data bits, and no parity and in half-duplex mode only. This network supports communications with a huge range of devices manufactured by Johnson Controls and some other companies. Metasys N2 by Johnson Controls is a master/slave protocol with one master only so it is not possible to have two devices performing this function on the same network.
BACnet IP
BACnet (Building Automation and Control Network) is a communications protocol that helps the communication between building automation end-devices and building management systems. The BACnet protocol specification like every other protocol specification defines both how data is represented on the network and the services that are used to move data from one BACnet node to another. The specification also tells us about messages that identify data and network nodes such as who-Has, I-Have, Who-Is, and I-Am.
To meet the requirement of the widest possible set of applications BACnet was designed to support several different physical and link layers.
The BACnet/IP allows users to transfer data to and from devices over Ethernet using BACnet/IP Protocol. It allows users to use different applications to discover devices, objects and properties of objects of any field device that supports BACnet IP.