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Re: [paho-dev] MQTT-SN talk at EclipseCon
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Stefano,
I think this is an interesting question. MQTT-SN, like MQTT is
publish-subscribe, which means messages are sent to topics rather than a
particular receiver. In MQTT, you have to connect to a server, so to
some extent that server becomes part of the destination of the message
along with the topic. The same thing happens in MQTT-SN when you
connect to a server.
But when you use QoS -1 in MQTT-SN, without a connection to a server,
then what does that mean? For a UDP implementation, you can send
messages to a particular multicast group, so you could say that that
group becomes part of the destination. Receivers of those messages can
forward them on, so that the message can reach a destination to which
the originator was not visible.
So, I think that MQTT-SN applications could take advantage of the
underlying transport's mesh networking capabilities. An application
could interpret a topic as containing a destination for instance, and
use the transport's capabilities to get it there.
Ian
On 16/03/15 16:08, Stefano Costa wrote:
Il 16/03/2015 16:46, Ian Craggs ha scritto:
Stefano,
I think that means MQTT-SN allows mesh networking (depending on the
capabilties of the underlying transport like ZigBee, UDP). Do you?
Ian,
well actually in the context of mesh networking as implemented in
Zigbee and others (DASH7, ZWave, BATMAN to name a few) it's common
understanding that "mesh" relates to the possibility that a message
going from A to B, where A and B are not mutually directly connected
because of topology, can pass through C (and so forth up to a
configured maximum number of intermediate nodes) and the protocol
integrates a transparent logic so that the best (or possible) route
from A to B is determined once / continuously / when needed.
This is not exactly what's given by MQTT-SN I think: retransmission is
there but not a proper routing protocol like AODV or any other.
Thanks S
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