SPIN : Sensor Protocol for Information via Negotiation

SPIN stands for Sensor Protocol for Information via Negotiation. There is family of protocols called as SPIN; they come in different flavors and features. These protocols are designed to address the deficiency of flooding and gossiping.
SPIN uses three types of messages, ADV, REQ and DATA. The ADV message is broadcasted by a node which has some data. This message is broadcasted by the node. This message will say about type of data contained by the advertising node. Interested nodes which got the ADV message send REQ message requesting for the data. The node having the data sends the data to the interested nodes. The nodes after receiving data send ADV message, and the process continues. This can be seen in figure below.



SPIN protocol

Node 1 sends ADV message to all its neighbors, 2 and 3.Node 3 requests for the data using REQ message, for which node 1 send data using message DATA to node 3. After receiving the data Node 3 sends ADV message to its neighbors 4 and 5 and the process continues. It does not send to 1 because 3 knows that it received data from 1.
The data is described in the ADV packet using high level data descriptors, which are good enough to identify the data. These high level data descriptors are called meta-data. The meta-data of two different data’s should be different and meta-data of two similar data should be similar. The use of meta-data prevents, the actual data being flooded through out the network. The actual data can be given to only the nodes which need the data. This protocol also makes nodes more intelligent, every node will have a resource manager, which will inform each node about the amount various resources left in the node. Accordingly the node can make a decision regarding, whether it can as forwarding node or not.