Echelon LNS - Manual (Page 182)

LNS Programmer's Guide 168
networks, so that each network can maintain its private media status while sharing a
physical TCP/IP connection.
When creating a system that uses private media, you should set the system’s
InstallOptions property to lcaPrivateMedia. When creating a system on a shared
media system, set the InstallOptions property to lcaSharedMedia. Since there will
be multiple networks sharing the media, you should also specify a unique domain ID for
your system. When the lcaSharedMedia option is selected and no domain ID is
specified, the LNS Object Server will select the 6-byte Neuron ID of its network interface
as the domain ID. This approach is recommended since it ensures that systems on shared
media will have unique domain IDs. Also, keep in mind the following:
• When using the engineered mode installation scenario, the Network
Service Device used to create the database may be different than the one
used to commission the system. You should either use the Neuron ID of
the network interface on the Network Service Device that commissioned
the system as the system’s domain ID, or set a unique 6-byte ID using
your own algorithm.
• In an installed system, if you replace a network interface (e.g. as part of a
repair operation), the new network interface will have a different Neuron
ID than the old one. As a result, you should not rely on the current
network interface’s Neuron ID to indicate the domain ID. Instead, you
should use the
DomainId
property of the System object to determine the
system’s domain ID.
• If your LNS application is used to install multiple networks, you should
not derive the domain ID from the network interface, as this would result
in domain ID duplication. Instead, you should use the Neuron ID of any
device that is to be installed into the respective network. Alternatively,
your application could choose a 6-byte random number to produce a
domain ID with a high probability of uniqueness.
In a system that uses shared media, the LNS Object Server disables background
discovery and device pinging. These activities are undesirable in a shared media system
for the following reasons:
• An LNS Object Server can discover devices that belong to a neighboring
system. Thus, discovery is not a reliable means of identifying devices to
install.
• If multiple LNS Object Servers are aware of the same device, their
communication with that device may create race conditions that result in
communication failures with the device, or improper configuration of the
device’s network image.
• The LNS Object Server background discovery and pinging tasks generate
periodic packets on the network. The traffic increases with the number of
LNS Object Servers issuing them. Since shared media also tend to be low-
speed media such as power line, this "extra" traffic can result in an
excessive load on the network.
These guidelines should be followed when installing devices on a system that uses
shared media:
• Do not use find and wink installation. Since you cannot be assured that
devices you discover "belong" to your system, you should not use this
method to identify devices. This means that you should disable