Echelon LNS - Manual (Page 184)

LNS Programmer's Guide 170
from traffic that has to span multiple channels, which allows more
effective use of available bandwidth.
• You want to provide for fault tolerance in the event of a physical-layer
fault, such as a short or open circuit. Only devices on the faulty channel
would be affected by such faults. Devices on other channels are isolated
from the fault by the routers or logical repeaters.
Overview of Router Types and Operation
A router connects two channels. Physically, a router contains two transceivers (one for
each channel it is connected to), and two processing modules. The transceivers and
processing modules receive packets from each channel, and decide whether or not to
forward the packet to the other channel. For more details on the functionality of
L
ON
W
ORKS
routers, see the L
ON
W
ORKS
Router User’s Guide.
A router counts as a device on each of its channels for the purposes of addressing and
physical layer design constraints, but not with respect to the LNS Device Credit limits
enforced by the LNS Object Server. For more information on LNS Device Credits, see
Chapter 13, LNS Licensing.
A network consisting of L ON W ORKS routers and channels must be completely connected,
i.e. it must provide a path for all devices to exchange messages with one another. With
the exception of redundant routers (see the Explicitly Controlling Subnet Allocation
section below), a network should have no logical loops created by routers. Physical loops
are allowed on a single channel when free topology transceiver channels are in use.
Physical loops between multiple channels may occur due to leakage on separate radio
frequency or power line channels. However, since no logical loops are allowed, two
messages having the same source and destination will always travel through the same
set of channels. Figure 8.1 displays an example topology with four channels that are
interconnected by three routers.