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Explicitly controlling channel allocation – Echelon LNS User Manual

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LNS Programmer's Guide

172

As of LNS Turbo Edition, LNS does not support defining or modifying a

router as a learning router. If an application defines a router as a
learning router, or changes a routers class to lcaLearningRouter, the

LNS Object Server will automatically change the class to
lcaConfiguredRouter. See the next paragraph for a description of

configured routers, and the advantages they provide.

• A configured router forwards packets based on internal routing tables.

Configured routers have their routing tables in non-volatile memory. The

LNS Object Server configures and manages the routing tables based on

its knowledge of the network topology. In addition, a configured router
can be configured to selectively forward group-addressed messages when

it is known that all members of the group are on one side or the other of

the router. LNS manages the subnet and group forwarding tables in
configured routers automatically. This is the most efficient router

type to use, as it also allows the LNS Object Server to

automatically determine the channel each device is attached to,
supports physical loops, and reduces unnecessary network

traffic. Configured routers also support the use of redundant routers (see
the Explicitly Controlling Subnet Allocation section below), which provide

for redundant message paths.

In addition, you can define repeaters and bridges as permanent routers, meaning that

their types cannot be changed after they are installed. When a repeater or bridge router

is defined as permanent, the LNS Object Server knows that it will never be changed into

a configured router later, and it will allow the same subnet to exist on both sides of the
router. This is permitted by the router, since bridges and repeaters do not perform

forwarding based on subnet address.

If a router is defined as a non-permanent bridge or repeater, LNS will enforce the rule

that no subnet can appear on both sides of the router or bridge, even though the router
itself does not enforce this rule. This allows the LNS application to change the router

class later, without creating subnet conflicts. See the Explicitly Controlling Subnet

Allocation section below for more information on the role of subnets and the rules
regarding their allocation.

With the exception of learning routers, you can use LNS to configure a L

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router

as any of the router types described in this section. The most efficient router type to use

is the configured router, as this allows the LNS Object Server to automatically determine
the channel to which each device is attached, supports physical loops, and reduces

unnecessary network traffic.

Explicitly Controlling Channel Allocation

Unless you are using the ad hoc or automatic installation scenario, you should explicitly

define the channels in your system, and specify those channels as devices and routers are

added to the system. When using the ad hoc installation scenario, you can omit the
channel definitions and allow LNS to create channels for you. When using an automated

installation scenario based on device discovery mechanism, LNS automatically creates
each AppDevice with the correct channel assignment. When explicitly defining a

channel, you must specify the channel’s media type, by transceiver ID. The LNS Object
Server includes the ConstTransceiverId constant, which includes enumerations for

each of the possible transceiver types you can use for this purpose.