How does peer-to-peer work?
Peer-to-Peer
Peer-To-Peer (PTP) is the process of sharing point statuses directly to other controllers on a network without having to pass data through the head end PC. PTP Setup is accessed in Editor Mode only. In Real Mode, Peer to Peer testing is available.
Note: Only inputs (software or hardware) can be shared. Once designated as shared, the point will “broadcast” its status to other controllers as specified in the PTP setup screen. If a point used in a logic statement is shared, then that logic statement will be stored in the controller instead of the head end PC.
In what situations would you want to use Peer-to-Peer?
•Stand-alone systems: a few controllers without an Automation Server.
•Communication to the Automation Server is down. You can’t really determine when this going to happen, but if you set it up in advance, you have added redundancy to the system.
Limitations:
•Peer-to-Peer will work with the following controllers:
o8X
o16X
o32X
o64X
oVAV Controllers
oLC-ER32
•Only available on versions of CBAS from 1.5.21 forward (Feb 2003)
•Point types that can be PEER points:
oBinary Hardware or Software
oAnalog Hardware or Software
•Point types that cannot be PEER points:
oMulti-state
oMeter
oPanel
oChannel
oFire
•Peer-to-Peer will not work across a Router on TCP/IP networks
oMust be able to send/receive “broadcast” packets
•When writing Logic involving a PEER point, do not use the “is in alarm” phrase referring to that point. The packet sent by PEER points does not contain that information.
•Command-able points can be shared as PEER points, but the PEER version of Points are not command-able. (A PEER version of the original point resides on the controller(s) that it is shared with)
Programming PEER points is easy. First, go to System, and then Peer-to-Peer Setup and you will see the editor.
•Click the “Add Point to Shared List” button and choose the points you want to share from the list that appears.
•Once shared, highlight a point and you will see a list of controllers it is shared with in the list on the right.
•Click the “Add Controller to Destination List” button to choose controllers that will receive status updates from the shared point.
•Highlight a point in the shared list and use the buttons in the middle of the editor to change the minimum and maximum amount of time that statuses are sent.
•Click the “Generate Report” button to see a report that shows each point and the controllers it is shared with. With one page per shared point, the report can be quite lengthy.
•All CBAS reports can either be printed, or saved in one of many different formats. Click on
to save the report. Go to Hardware View. In each controller that a point is shared with, you will see that point listed with the word “PEER” after it’s name. This point will never show the correct status that is shown on the original point. However, the correct status will be displayed on a Handheld Terminal.
Routing is also shown on the PEER Editor screen and is configured automatically depending on whether the host controller has RS-485 channels programmed. Controllers with no RS-485 channels are assigned “No Routing”, meaning that the status is broadcast only by that controller. Controllers with RS-485 channels are assigned “Routing 1”, which means that status is broadcast on all channels. When another controller receives the status, it re-broadcasts on all channels except the one it was received on.
When writing a logic statement involving a PEER point, you will not see the local “PEER” point listed as a selectable point. You have to go to the “All Points” list and select the original point. CBAS knows that it is a PEER point and will take care of the rest for you.
Some good examples of points that might be shared between controllers include:
•Outside Air Temperature
•Outside Air Humidity
•Summer/Winter Mode
•Building Master Schedule
•AHU Master Schedule
Peer Testing: Previously, Peer-to-Peer could be edited in Editor Mode only. There is now a menu option for Peer Testing in Real Mode only. In this feature, you select a controller and click START. That controller sends out a blank Peer Broadcast message. All Peer panels receiving this message will in turn respond with a broadcast message. All of the panels that respond will be listed. This will tell you if a controller can talk to another controller via a broadcast message. (Note: Broadcast packets will not be forwarded through a Router, only a Switch) Firmware version 10.1 or later is required for this feature.
When configured properly, Peer-to-Peer can add sophistication and/or redundancy to a sequence of operation. It can turn a small group of stand-alone controllers (without server) into a real interactive system, similar to one with a server. Or it can add some redundancy in the case when a server is off-line.
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