industrial wireless book special edition - Networking ...

This happened in the early days of wired
fieldbus where technology and marketing were
synonymous. It is worth speculating how the
early fieldbus markets might have developed if
today’s Internet had been around at the time…
Well, the Internet is here and the virtually
inexhaustible IPv6 addressing, presently
without immediate value in Process or Factory
automation, promises the ‘Internet of Things’,
a connected web of smart objects. And it is a
reasonable bet that some of those Things will
find their way into both Factory and Plant.
Actually, the gateway vs router argument
loses some of its force when you start talking
about wireless mesh. Given that both WHART
and the new IPv6 stacks have highly robust
security layers, Internet gateways merely create
a potential system vulnerability accessible from
a single IP address; dumb(ish) wireless routers
and IPv6 have both good stacks and sheer
numbers to ward off attacks. A malware
malcontent might just be able to sidestep
firewalls and conventional security to find an
individual device to target, they will also have
to find the right number address and there are
an awful lot to choose from! 192.168.2.235
probably won’t hack it…
The problem clearly stated
While we are talking very early days in IPv6
wireless technology albeit backed with big
money, it seems important not to get too
carried away. The Problem Statement written by
Bormann and Sturek of the IETF 6LoWPAN
Working Group is essential reading for anyone
of serious disposition towards wireless development.
The introduction to the document
provides quite a good summary:
‘The 6LoWPAN and ROLL [Routing Over Low
power and Lossy networks] WGs are laying the
groundwork to make the Wireless Embedded
Internet a reality, but what application
protocols will we use with these networks?
6LoWPAN’s lowpower area networks
(LoWPANs) and, more generally, ROLL’s
lowpower lossy networks (LLNs) exhibit severe
constraints on the bit rates achievable and the
packet sizes that can be efficiently sent. Many
(but not always all) nodes in these networks
also are constrained in the energy they can
expend for computing and communication, the
memory available, and the code size that can
be accommodated in each node.
More generally speaking, there are many factors
that play together to limit the per-node capabilities
compared to today’s typical Internet nodes.
(Moreover in most cases links in LoWPANs and
LLNs are “lossy” by nature, thus experience high
bit error ratios, making the communication
sometimes challenging. The existing transport
protocols used for reliability such as TCP may be
too expensive to implement for LoWPAN nodes
and may not perform well in lossy environments.)
The established application protocols for
Internet applications may be a poor fit for
LoWPANs and LLNs. For instance, request
response protocols like HTTP may require
battery-operated, mostly sleeping nodes to be
listening for requests much more frequently
than their application processing requirements
alone would need them to wake up. In
addition, some of the applications may require
optimizations in terms of bandwidth usage; for
example, the usual data formats (both headers
and body) are perceived to be too chatty for
the 50 to 60 byte payloads possible in
LoWPANs. Their interpretation and generation
may require too much code for the 8-bit and
16-bit processors dominating LoWPAN nodes.
Still, it would be a mistake to start a new silo
of application protocols that do not benefit
from existing application area Internet
experience. A number of concepts well-established
in the IETF application protocols, such
as identifying resources by URIs, may transfer
very well to LoWPANs…’
Reality kicks in
It is the answering of such questions which
appears to be tying up ISA100 with inextricable
knots in the committee’s pursuit of a
wireless mesh Internet Protocol standard(s) for
everything Industrial and Process. Meanwhile,
the real world needs a more practical approach
to wireless application. IEEE802.11a/b/g/n is
fine and fast for cable network replacement
where the nodes can draw hand-warming
electrical power.
IEEE802.15.1 Bluetooth is much slower, less
power-hungry but more robust: an altogether
excellent all-round candidate for high reliability
sloth-like industrial wireless devices which do
not require direct network connection or selfforming
networks. Can work off batteries.
ZigBee. Great for opening garage doors and
other jobs around the house. It recently
declared an IP stack version for smart metering
which could (eventually) find industrial and
Process applications.
WirelessHART and other IEEE802.15.4 base
platforms. Great for SCADA-ing up oil refineries
and slothful, but physically spread applications
in need of low power wireless mesh that do not
require direct Internet device control.
ISA100 and variants. I’ll keep watching
because this is what I am paid to do, but the
signals are rather confusing.
6LoWPAN (IEEE802.15.4 PHY and datalink).
Far too early to make any serious statements
about future relationships with Process and
Factory Automation. However, the IPv6 network
mesh, a moniker which includes The Internet
of Things and software stacks with a size
inverse to those of the development dollars
make this the one to watch.
First published in the industrial ethernet book September
2009
sponsored by Advantech
industrial ethernet book