Protocol Versions

There are two versions of the protocol, loosely named version 3 and version 4 (the version numbers actually refer to points of major change in RPCManager).

Version 3 protocol is used in all RPCManagers from VTS version 7.1.21 through version 9.

Version 4 protocol is used from version 10 onwards.

Version 4 has a different structure enabling RPCs from multiple source GUIDs and to multiple destination GUIDs to be transported in the same RPC packet, reducing the number of RPC packets needed (and hence the turnaround latency). Version 4 protocol supports packet compression and does so by default. Finally, VTScada TCP/IP engine changes permit version 4 to get increased throughput (particularly on WANs) by properly utilizing TCP window scaling and a larger default window size.

RPCManager versions using version 4 protocol also support version 3 protocol to enable support of mixed versions of VTScada in the same SCADA system.