CHoPAN is a Tridium proprietary protocol running over UDP/IP that enables Sedona Framework devices to share data with JACE stations and other Sedona Framework devices. CHoPAN can be used as an alternative to Sox Polling or Sox Eventing to allow a JACE station to read/write data in Sedona Framework devices.
It is also the only way for Sedona Framework devices to read/write data in other Sedona Framework devices, as there is no Sox client, only a Sox server.
Key comparison points between CHoPAN and Sox:
The Sox protocol is designed around an authenticated session between a client and server. CHoPAN is sessionless; each request is independent of the previous one. So the Sox session requires the server to maintain state information about the session, and effectively limits the maximum number of open sessions to whatever resources the server is able to allocate for session management.
Network bandwidth usage
As a consequence of point 1, each Sox connection requires multiple messages to set up and tear down and dedicated resources to maintain. There is continuous “keepalive” traffic to maintain the session. CHoPAN is not authenticated, requires no connection setup and no keepalive traffic. This makes CHoPAN a better choice on low-throughput networks like the wireless 802.14.5 Jennic.
Peer-to-peer communication
The Sedona Framework does not have a Sox client. So for a Sedona Framework device, the only client option for peer-to-peer communication is CHoPAN.
Communication from a Sedona Framework client to a Sedona Framework server via CHoPAN may not be directly peer-to-peer. Due
to the JenNet tree structure of a SedonaJen6lpNetwork, a client may need to send its request up one or more nodes in the tree
(possibly to the coordinator) to reach the server node.
Hibernation
Any server (Sox or CHoPAN) must be available continuously for client access. So for hibernating nodes, the only logical choice for sharing data is for them to be a CHoPAN client.
Currently, Sedona Framework support for hibernating devices (typically battery-powered devices) is not widely available. However,
related NiagaraAX support exists in the SedonaJen6lpNetwork driver and NiagaraAX Workbench, and is typically “noted” like
this.
When the Sedona Framework device contains a CHoPAN client, it can initiate reads and writes from other devices. The device can wake up, use CHoPAN to push and/or pull data from another device, then go back to sleep. Sedona Framework devices cannot use Sox to initiate reads or writes because only the Sox server code is implemented in the Sedona Framework.
Service Pin notification
The Sedona Framework device can generate a service pin notification to help user identify physical devices. This is not possible with Sox.
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