BACnet Web Services (BACnet/WS) is the latest Internet communication method of the ASHRAE standard for building management systems. This paper provides theoretical and experimental studies on the message transmission performance of BACnet/WS access over the Internet. The average transmission times of the BACnet/WS "getValues" service for a large number of objects were measured from inter-continental locations. The theoretical calculation of a TCP/IP throughput equation accurately matched resulting data from field tests. This paper found that the average transmission time is roughly proportional to the average round trip time of IP network connectivity probing, "Ping". This paper concludes that transmission time takes up a significant portion of the total service time of a remote BACnet/WS system over the Internet.

Units: Dual