Embedded Rule-based Management for Content-based DTNs - Advances in Network-Embedded Management and Applications - page 89

We propose a mechanism that allows us to take conguration decisions in a
distributed fashion, responding to high level rules.
The structure of the paper is as follows. The overall description of our ON
protocol is presented in Section 2. Later, in Section 3, we shortly motivate the need
of including self-management capabilities to ON nodes. The overall design of the
system is presented in Section 4.1. The characteristics of our prototype and the main
hardware characteristics and constraints that drive the implementation is presented
in Section 5. Finally, in Section 6, the paper presents an evaluation of the DEMOS
system that shows how it is possible to perform self-optimization decisions with a
very reasonable overhead in terms of CPU and memory.
2 An Opportunistic Content-based Routing Protocol
The DEMOS architecture implies the existence of an opportunistic network between
the sensor devices and the data collection points. In an opportunistic network, the
existence of a connectivity path between any pair of nodes in a given moment is not
guaranteed. For a message to reach its target, it may be necessary that some node
or nodes keep the message in their own memory until they can deliver the message.
There are several methods and algorithms for Opportunistic Routing, but to
support DEMOS operations we created RON, a new content-based opportunistic
protocol. The reasons for creating a new protocol were:
{ Usually, opportunistic network algorithms are intended for destination-based
routing. On the other hand, Content-based routing provides us of several ad-
vantages: as specifying a data ow does not rely on having inventory on the
network devices, the deployment is simpler; multicast and broadcast messaging
is more naturally represented; the messages can be dynamically prioritized or
routed based on message properties such as the type of issuing sensor, danger
level, or geographical location. All this rich behavior can be changed at runtime
without changing the conguration of any node of the network, providing great
exibility.
{ Many gossip-based algorithms operate on a Peer-to-peer basis, where each link
is considered isolated from the rest. On the other hand, our target are wireless
networks, where when one node issues a message, all the nodes in its range
receive the message independently of their address in the network layer (the
\broadcast advantage"). Our routing algorithm uses this property to reduce
the network trac.
RON is a publish-subscribe protocol in which a node that is interested in some
type of messages, issues a subscription that species that interest using a logic lter.
This subscription is ooded through the network passing from one node to another
each time those nodes are within range of each other. When a node wants to publish
a notication, it broadcasts a message containing the notication to all the nodes
in the neighborhood. Each of these nodes matches the received message against
the subscriptions it is carrying, and decide whether to carry or ignore it according
to routing rules. Eventually, the message will reach all the subscriber nodes. The
algorithm is described in more detail below.