Remote Programming Dissemination Collection Network Management

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Remote ProgrammingDisseminationCollectionNetwor
k Management
Gilman Tolle (also speaking for Jonathan Hui)
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A Sensor Network Link?
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A Sensor Network Link!
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Why Over-The-Air Reprogramming?

• Embedded nature of sensor networks theyre
  small!
• Network scales reaching thousands of nodes
  theres a lot of them!
• A necessity in debugging and testing cycle we
  cant stop messing!
• Learn about the environment after deployment
  things change!
• sensing data, network characteristics, etc.

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What is Deluge?

• A reliable data dissemination protocol for
  program images over a multihop network.
• Combined with a bootloader (TOSBoot)
• ? Network Programming

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Deluge Data Representation

• Program divided into pages, each consisting of N
  packets.
• Reduced RAM requirements
• Allows for spatial multiplexing

Program
101 110
110 010
010 000
101 111
000 011
Packets
1
2
3
4
N
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How Does Deluge Work?

• Nodes periodically advertise
• Suppress similar advertisements

I only have version 1.
Version 2 here.
I only have version 1.
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How Does Deluge Work?

• Neighboring nodes request data
• Suppress similar requests

Send me page 1!
Send me page 1!
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How Does Deluge Work?

• Requested data is broadcast

Packet 12 of page 1!
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How Does Deluge Work?

• Dropped packets are NACKed

Repeat packet 4 of page 1!
Repeat packet 32 of page 1!
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How Does Deluge Work?

• Dropped packets are sent again

Packet 4 of page 1!
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How Does Deluge Work?

• Advertise for propagation to next hop

Version 2 here.
I only have version 1.
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Spatial Multiplexing

• Propagate in waves
• Exploit limited radio range for concurrent
  broadcasts.
• Reduced completion time
• o(d Sobj) vs. o(d Sobj)

Page 0
Page 1
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Epidemic Propagation

• Epidemic propagation from one source

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Deluge Features

• Epidemic propagation from one source or many
• Continuous propagation effort by all nodes
• Turn on/off radios at will
• Reach nodes with intermittent connectivity
• ?Will find a path if it exists
• Aggressive message suppression
• Scales with density
• Ultra low quiescent traffic

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Deluge Features

• Management
• Multiple program images
• Image metadata
• User confirmation on expensive operations
• Minimize operator error
• Robustness
• Redundant CRCs
• Golden Image with write protect
• Load Golden Image
• Watchdog trigger
• Golden gesture
• TOSBoot
• TOSBoot as isolated code
• Verify CRCs
• Verify system voltage

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Deluge Lessons

• Advantages
• Ease of reprogramming 100s-1000s of nodes
• Does not erase node IDs
• Golden Image is immensely useful
• Quickly switch between images
• More reliable than uisp or msp430-bsl
• Deluge over 802.15.4 more efficient that 802.11!
• Disadvantages
• Ease of reprogramming 100s-1000s of nodes )

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Routing

• Getting the packets through, across many hops
• Every node is a router too
• Gateway-centric
• Get data from the gateway to all the nodes
  dissemination
• Get data from all the nodes to the gateway
  collection
• Node-to-node?
• Message-based
• Transferring single packets, datagram-style
• A layer, with clients above and services below
• Attribute Queries and Changes
• Event Reporting
• RPC Command Layer
• IP is not the right solution
• Any-to-any is not useful enough to justify the
  state and complexity

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Drip Dissemination Layer

• Each sent message reaches all nodes in the
  network
• Good for sending commands and queries
• A generic single-message communication layer
• command sendtype(message) on the host
• event receivetype(message) on the node
• Lightweight header type and sequence number
• Higher layer can add destination addressing
• Uses Trickle epidemic algorithm (Phil Levis)
• Dynamic forwarder selection
• Periodic retransmissions
• Neighborhood suppression
• Caches latest message on each channel

Client
GW
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Drain Collection Layer

• Every node needs to send data to a gateway
• A generic single-message communication layer
• command sendtype(message) on the node
• event receivetype(message) on the host
• Very well-studied problem (Too many authors to
  list)
• Link estimation plus distributed execution of
  shortest-path algorithm
• Ours must support multiple gateways
• Each gateway builds a tree -- each node selects
  the cheapest next-hop
• Automatic subdivision of the network into pieces

Client
GW
GW
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Routing Goals

• No predefined geographic structure
• Routing decisions based only on connectivity and
  link estimators
• Makes it easier to deploy and move nodes
• Minimal state single next hop, update-in-place
• Robust to lossy networks
• Drip periodically retransmits cached data with
  exponential backoff
• Drain uses link-layer ACKs, retransmissions, and
  long retry window
• Experiment with simple duty cycle 1 second on, 1
  second off
• Looks just like a lossy network, but the
  protocols keep working
• Include rich metadata (source addresse, ttl,
  sequence numbers)
• How are those bad packets getting into the
  network?
• Impossible to answer without metadata
• Enables network management through packet
  sniffing
• Even without a specific management layer

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Network Management

• Sensor networks fail
• All networks fail sometimes!
• Management lets us detect and respond to
  problems
• Just as important for our networks
• Harder to do, thanks to highly dynamic networks!
• Passive Packet Sniffing
• Active Network-Layer Monitoring
• Management Queries
• Monitoring Policies and Statistics

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The Unbearable Lightness of Sniffing

• Just sniffing packets reveals a wealth of
  information
• Active nodes from routed Drain messages
• Network topology from Drain beacon messages
• Dissemination behavior from Drip messages
• Reprogramming status from Deluge advertisement
  messages
• Overall traffic rates and histograms by type
• Doesnt make any extra demands on the network
• If youre going to send the packet anyway
• Passive management information gathering
• Works when the network isnt running the
  management layer
• Sometimes, you really need that extra few kB of
  code space

GW
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The Story About Ping

• Characterizing the performance of a dynamic
  network is HARD
• The first tool of network management ping
• Best with a few nodes that you dont check very
  often
• The second tool of network management the ping
  daemon
• Can provide historical and current data on many
  nodes
• The third tool of network management the ping
  visualizer
• Scalable way to handle large complex networks
• Most networks dont have a natural spatial
  realization
• Our network is firmly embedded in space

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The 10,000-Foot View
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Management The Gathering

• Sometimes, you need to know more than ping can
  tell you
• How long has the node been running?
• Has the node been dropping any packets?
• and in our energy-constrained mote-land
• What is the nodes power source?
• Does the node have enough energy to run?
• Management can be seen as a database problem
• TinyOS application exports information
• Named attributes, variables in RAM
• Attribute schema generated at compile time
• Replace long names with short integers save
  bandwidth
• Store schema on mote using Deluge Supplement
• Nucleus component responds to queries
• Get attributes 2, 3, 6 and RAM variable at
  0x1a8c with length 2

System App Components
Attribute Dispatcher
Query Processor
Drip/Drain
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Nucleus Host Architecture
Pixels
Characters
Web Visualization
Other Mgmt Tools
XML-RPC
Monitoring Daemon
Command-Line Tools
XML-RPC
XML-RPC
Binary Data
Query Translator
Other Client Applications
Binary Data
Packet Forwarder
GW
GW