Interfacing Embedded Sensor Networks to the Internet

(motes, in particular)

Philip LevisStanford University

Embedded Sensor Nets(motes: the bottom tier)

Untethered and wirelessEnergy is the limiting resource and constrains other resource, very low duty cycle

Very different interfaces (pools, not queues, cross-layer information, neighbor tables)

Aggregate, collaborative operationDesigned and deployed for a particular use

Mix of networking and systems concerns

Whole network tasking

ScenarioCommunicating with a mote network from an Internet host

Data-centric communicationCollecting data, specifying collection, actuation

Node-centric communicationManagement

Location-centric communicationEmbedded sensor network discovery

Where IP StopsMote networks are not IP-basedThey use a wide range of network protocols, due to differing usage models and requirements

End-to-end model does not always imply end-to-end communication (e.g., aggregation)

Gateways form a bridge between the two protocol worlds

IP MoteEmNetGateway

NamingData-centric communication can use layer 4+ protocols on top of IP (no need to name nodes)E.g., a directed diffusion query which then produces a stream of data items over TCP

But node-centric communication would greatly benefit from being able to name sensor nodes in the IP worldE.g., “where does mote 57 think it is?”

Node-centricThe scale and scope of mote networks will require a larger namespace.Need to be able to name every embedded node.

NATs/port assignment could expand the namespace a bit, but not enough.

Basic problem: IP namespace (too small)IPv6 would solve this

Location-centricLocation-centric communicationNeed to discover resources that are physically, not logically, local

Need a naming system infrastructure to support this form of discoveryTraditional ubiquitous computing problem

Or perhaps a local communication layer?Typically a responsibility of the data link layer

A Future Internet(involves the Internet very little)

Interconnects existing networksNetwork as an edge device, node as an edge device, collection management

Edges not internally held to “narrow waist”

The rise of the data link layerEmNet

EmNet

MobilePhones

CarTel

IP