13-6 Industrial Communication Systems
themselves and process the encapsulated trac as a node, not as a router. is eectively enables purely
IP-based
eldbus
nodes,
which
can
communicate
directly
to
legacy
(non
IP-based)
nodes
in
the
system.
e
tu
nneling
ap
proach
ha
s
be
en
ch
osen
fo
r
Lo
nWorks
or KN
X/IP.
Other
eldbus
systems
implement
a
dedicated
IP
data
link
layer
for
the
eldbus
protocol
natively.
Nodes
in
these
systems
can
be
connected
directly
onto
the
Ethernet
network
without
the
use
of
a
tunnel-
ing
technique.
Examples
are
BACnet/IP
or
Modbus
over
TCP.
To
access
other,
non
IP-based
CN
nodes,
routers
ar
e
us
ed.
Notwithstanding
the
ease
of
IP
everywhere,
a
separation
of
eld-level
and
oce-level
networks
is
still
recommended
for
performa