Image Processing Reference
In-Depth Information
ISA 100.11a
Layer 7
application
Application—mapping
from legacy protocols
Layer 6
presentation
Layer 5
session
IETF RFC 4944 (6IoWPAN)
End-to-end delivery—UDP, security
(integrity and authentication)
Layer 4
transport
Layer 3
network
IETF RFC 4944 (6IoWPAN)
IPv6 packets
Redundant path mesh network.
time-synchronized, frequency
hopping protocol
Layer 2
data link
Layer 1
physical
IEEE 802.15.4-2006
FIGURE .
ISA.a protocol stack.
device can be connected either directly to the DLL subnet via a radio or through backbone routers,
in which case it is located somewhere on the backbone network. Routing in DLL subnets is handled
either through the use of graph routing (preallocated redundant paths) or source routing (ad hoc-
created nonredundant paths), but routing on the backbone network is not within the scope of the
standard.
.... Security
ISA.a provides a two layer security measure; single-hop and end-to-end security. The single-
hop security is handled in the MAC sublayer (DLL), and the end-to-end security is handled in the
transport layer.
Both security layers use shared-secret symmetric keys (it is optional to use asymmetric keys) and
AES- in order to provide encryption, authentication, and integrity checking. Payload encryption is
optional in ISA.a. he ISA.a specification is designed with future “upgrades” of the security
specification in mind.
27.5.3 Why Is ZigBee Not Enough?
Since any problems with the equipment translate to economical loss for an industrial user, reliability
is a primary concern for these users. Hence, parameters like network robustness, reliable message
delivery, authentication, and integrity are all important for industrial use. Moreover, the threat of
industrial espionage advances the requirement for encryption to hide information that can reveal
anything about the production in the plant to competitors.
One of the loudest arguments against ZigBee has been the lack of industrial-grade robustness. First
of all, there is no frequency diversity since the entire network shares the same static channel, making
it highly susceptible to both unintended and intended jamming. Moreover, the static channel will
