User's Guide

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neo.
cortec
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A payload message can consist of up to 21 bytes of raw payload data. The raw payload
is allocated exclusively to application data. In addition to the raw payload, the data
which is being send, includes a header with the following information:
Field
Description
Destination Node ID The Node ID of the Sink Node to where the package is intended
Source Node ID The Node ID of the node which is the originator of the package
TTL Time To Live value – if the package is older than the TTL value, it
will be removed from the network
CRC Cyclic Redundancy Checksum value used to validate a package
locally
Age The accumulated age of the package, calculated from the time it
was enqueued in the source node
When calculating throughput, it does not make sense to use bytes/sec or similar, as the
data is not being streamed. In a real network with 100’s of nodes, and a Scheduled Data
Rate optimised for low average current consumption, the throughput from each node
may only be a few payload packages per minute.
3.3.5 Security
All communication, not only payload data, but the full Scheduled Data transmission as
well as the Beacon transmission, is encrypted using AES128. The key for the encryption
is the same as the Network ID (see section 3.4 Configurable Parameters). This means
that nodes which do not have the correct Network ID, will not be able to decode
transmissions from a network for which it is not approved.
In order to keep the network secure, the Network ID must be kept secret for a particular
installation.
Acknowledged Transmission is using a challenge/response authentication between the
originator and the destination. This means that each message exchange will be subject
to a unique challenge with a unique associated response. Since the challenge/response
messaging is included in the encrypted communication, the data exchanged will appear
completely random from transmission to transmission, even if it is the same payload that
is being exchanged. This prevents playback attacks
1
and improves the overall security
level of the communication system drastically.
NOTE: The synchronisation of the challenge/response mechanism between any source
and a particular sink happens at the first payload data exchange. This means that the
1
See http://encyclopedia2.thefreedictionary.com/Playback+attack for explanation