Active Message Application: CONNECT

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Active Message ApplicationCONNECT

• Presented by
• Xiaozhou David Zhu
• Oommen Regi
• July 6, 2001

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What does CONNECT do?

• Ad-hoc Networking
• Uses the Active Message primitives to explore
  routing topology and than to propagate
  information towards a central collection node.
• Determines a minimal spanning tree and sends back
  sensor reading over that tree to the base station

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How does CONNECT do?

• Destination-Sequenced Distance Vector algorithm
  having all nodes transmit to a base station.
• This algorithm is implemented through the Java
  ConnectionManager module.

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How Does CONNECT do?

• The system starts out with zero knowledge of the
  identity or topology of sensors that are present.
  Each node knows only its own identity.
• The base station knows that it is directly
  connected to the host PC. The base station is
  the origin of all routing update messages.

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How does CONNECT do?

• The base station periodically broadcasts out its
  identity and that it has connectivity to the host
  PC.
• Devices in the range receives the message and
  update routing information.

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How does CONNECT do?

• The devices then rebroadcast the new routing
  update to devices within range that there is a
  path to the base station through them.
• Devices remember the first routing update that
  they here, which corresponds to the shortest path
  to the base station.

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How does CONNECT do?

• To prevent cycles in the routing topology, time
  is divided into eras and route updates are
  broadcast once per era.
• For information collection, each node
  periodically generates and transmits information

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How does CONNECT do?

• A devices transmissions are addressed to the
  device ID that was received in the last routing
  update. The recipient will repeat the same
  process until the packet reaches the base
  station.
• Each node simply knows the identity of the next
  hop that will bring the packet closer to the base
  station.

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How does CONNECT do?

• The identities of the intermediate hops are
  stored in the packet as it travels to the base
  station. This allows us to determine the overall
  routing topology that the network is using.

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ConnectionManager Module

• This module forwards messages between simulated
  motes. Each mote sents its packets to this
  module which forwards it to those motes that are
  in range.
• The connection graph is determined by what
  entries have been added to the connection
  managers list with the void add_conn() method,
  where a and b are the IDs of the motes

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ConnectionManager Module

• The Wired_link is the interface defined in
  Wired_link.java, which has a method
  send_packet().
• The Reliable_link.java defines the implements the
  interface and defines the send_packet() as
  writing data to the output stream.

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ConnectionManager Module

• The connectionManager.java manages the linkedlist
  of mote IDs. It has two major functions
  add_conn() and remove_conn().
• The two function adds/removes the motes to/from
  the graph if the mote is within/out of range.

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ConnectionManager Module

• The messages are sent/received through the
  sockets. A new thread will be started when a new
  mote is found by the MoteConnection.java, which
  simply add the new motes into the output list.
• When the a mote is added into the graph, all the
  motes are synchronized.

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ConnectionManager Module

• The Java code does not seems to have completed.
  The remove_conn() method is never called, which
  means that if any of the mobile motes moves out
  of the range, it will not be removed from the
  graph. Or, if a mote is defective, all the motes
  through this mote will not be able to connect to
  the base station.

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CONNECT Modules

• GENERIC_COMM communication
• MAIN initialization of sub components
• CONNECT establishing connection
• CLOCK timing
• LEDS visualization
• PHOTO accessing photo sensor

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CONNECT Components

• Two files .comp file which contains the
  interface specification for the component
• .c file that contains the implementation of the
  component

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Components Interface

• The interface description contains 3 parts
• List of commands it ACCEPTS (2)
• List of events it HANDLES (4)
• List of commands it USES (17)

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Component Graph
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Components Implementation

• The CONNECT.c explores routing topology and then
  broadcasts back light readings to the base
  station.