ZigBee Network

Michael,

Thanks for your interest in ZigBee.  You are asking very good questions as what is feasible does not always line up with what is practical.  I want to start by saying yes, it is true that a ZigBee network could theoretically have over 64K devices as the addressing utilizes a 16 bit short address (64 bit long or IEEE addresses are used for unique identification throughout the world), but as you likely suspect it is not practical to have a network with this many devices.  Aside from managing the address space and trying to resolve conflicts using the conflict resolution algorithm utilized in ZigBee PRO, having 64K devices in a network is a problem with respect to bandwidth utilization, device discovery and network management, and routing as RAM limitations prevent you from keeping such a large number of addresses in memory.

What is more practical is to have ZigBee networks of 10's or 100's of nodes (again I'm not saying thousands are not possible, just not practical) with bridge or gateways to link potentially multiple co-existing networks.  By utilizing such a strategy you can have multiple networks co-located with each network operating on a different frequency and therefore not infringing on the overall communication bandwidth avaialble. 

Configuration of the max depth and max children is specific to the profile under consideration, and whether you are using the ZigBee or ZigBee PRO feature set.  What i woud first consider is what do you expect a typical system to look like, what sort of communication bandwidth requirements do you have, what kind of coverage do you need, etc... Taking all of these parameters into consideration you might then want to start looking at what existing infrastructure you have in place (e.g. Wifi) that could act as a bridging mechanism. 

Hopefully this begins to shed some light on your questions.  I hope that others will join in this conversation as well to provide some examples of how they made system level decisions when configuring and commissioning their ZigBee network, and what sort of challenges they faced when implementing their design.