Issue
What is the difference between "Enhanced MSTP" and "Standard MSTP" Token Passing in Continuum BACnet?
Environment
Continuum BACnet
Cause
It is important to note that Only Continuum BACnet controllers have this feature. Any third party BACnet MSTP controller connected to a Continuum BACnet system will only perform Standard MSTP token Passing. In a network where you have Continuum B3 controllers and third party MSTP controllers and you have enabled Enhanced MSTP, you will have a combination of the two methods. The Continuum B3's will always pass the token back to the BCX, and the 3rd party controllers will always pass the token to the next ID on the MSTP. If you wanted the benefit of Enhanced MSTP on this type of a system, you could intersperse the MSTP ID's of the B3's and the third party so that you would have a more even flow of the token back to the BCX.
Resolution
Continuum Bacnet Controllers default to "Enhanced MSTP". What this means is that the Ethernet level controller (BCX or B4920) that manages the MSTP network sends out a message to all Continuum B3 controllers which tells them that after they are done with the token on the network, that they should pass it back to the BCX or B4920 instead of sending it to the next B3 down the line. The purpose of this is so that any user interaction with the B3 network such as graphics, listviews, reports, etc.. will be much faster. This Token passing scheme is similar to how Infinet performs.
Standard BACnet MSTP token passing is done such that each controller on the MSTP network gets the token equally and this includes the BCX or B4920. So if you had 127 nodes on the network, the BCX controller would only get a chance to talk once after every MSTP controller had a chance to talk. The Continuum BACnet controllers can operate in either mode by setting this feature in the BCX or B4920 Web Configuration page.
Each token Passing scheme has some benefits. If there were a lot of user interface type access needed on a system, the Enhanced mode would be preferable for speedy response.
If there was very little or no user interaction but there was a lot of data sharing or alarm delivery from the MSTP controllers, the standard token passing would give all the devices on the MSTP network more opportunity to export their data.
