User's Guide

- 14 of 42 –
neo.
cortec
.
This type of messaging is useful in applications where each message is important – for
instance in metering and sub-metering applications where the data contained in the
message is vital.
Note: If the originating node is a non-sink node (i.e. Node ID > 128), the protocol
cannot use Speed Routing to route the ACK message back to the originator. In this case,
the protocol will route the ACK message back along the same route as the payload
message was routed. Since this backward route is only valid while the topology stays
static, it is not recommended to use Acknowledged Transmissions in dynamic topology
networks with more than 128 nodes. Similarly, only sink node Node IDs shall be used
(Node ID < 128). In static networks, it is ok to use Acknowledged Transmission for any
number of nodes in the network.
3.3.4.3 Non-Acknowledged Transmissions
Non-Acknowledged Transmission corresponds to UDP transport known from IP
networks. Messages are routed from source to destination, and while travelling through
the network, the local package exchange between neighbouring nodes is done using a
local ack/nack handshaking. This means that even though an acknowledge message is
not routed back from the destination to the originator, the payload data is still being
transmitted in a reliable fashion while on route from originator to destination.
This type of transmission is useful in networks where data is exchanged frequently, or in
networks with a highly dynamic topology (because backward routes are not used). Since
the total number of messages routed in the network when using Non-Acknowledged
transmission is typically half of that when using Acknowledged transmission, the pace of
the network can typically be configured lower and thereby the average power
consumption can typically be lower.
3.3.4.3.1 Sending to non-Sink Nodes
As previously mentioned, Speed Routing maintains routing information for nodes with
Node Id < 128 (sink nodes), and as such not all nodes in a network are directly
addressable.
There is however a method for sending Non-Acknowledged messages to non-sink
nodes:
Non-Acknowledged messages are being routed in the same way as Acknowledged
messages, and when these messages travel through the network, a backward route is
being created. This means that once a non-sink node has transmitted either a
Acknowledged or a Non-Acknowledged message to a given sink node (for instance a
gateway node), it is possible to send a Non-Acknowledged message from the sink to
the non-sink.