remote programming dissemination collection network management gilman tolle (also speaking for...
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Remote ProgrammingDisseminationCollectionNetwork Management
Gilman Tolle(also speaking for Jonathan Hui)
A Sensor Network Link?
A Sensor Network Link!
Why Over-The-Air Reprogramming?
Embedded nature of sensor networks – they’re small! Network scales reaching thousands of nodes – there’s a lot of them! A necessity in debugging and testing cycle – we can’t stop messing! Learn about the environment after deployment – things change!
sensing data, network characteristics, etc.
What is Deluge?
A reliable data dissemination protocol for program images over a multihop network.
Combined with a bootloader (TOSBoot) Network Programming
0101010101010101011010101101010101010101
Program
Deluge Data Representation
Program divided into pages, each consisting of N packets.
Reduced RAM requirements Allows for spatial multiplexing
101110
110010
010000
101111
000011
Program
Packets
1234 N
How Does Deluge Work?
Nodes periodically advertise Suppress similar advertisements
Version 2 here.
I only have version 1.
I only have version 1.
How Does Deluge Work?
Neighboring nodes request data Suppress similar requests
Send me page 1!
Send me page 1!
How Does Deluge Work?
Requested data is broadcast
Packet 12of page 1!
How Does Deluge Work?
Dropped packets are NACKed
Repeat packet 4 of page 1!
Repeat packet 32 of page 1!
How Does Deluge Work?
Dropped packets are sent again
Packet 4 of page 1!
How Does Deluge Work?
Advertise for propagation to next hop
Version 2 here.
I only have version 1.
Spatial Multiplexing
Propagate in “waves”
Exploit limited radio range for concurrent broadcasts.
Reduced completion time o(d + Sobj) vs. o(d * Sobj)
Page 0Page 1
Epidemic Propagation
Epidemic propagation from one source
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
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
0101010101010101011010101101010101010101
0101010101010101011010101101010101010101
0101010101010101011010101101010101010101
ProgA ProgB ProgC
Program NameCompile TimeUserIDHostnamePlatform
CRASH!
CR
CC
RC
CR
CC
RC
CR
CC
RC
CR
CC
RC
CR
CC
RC
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CC
RC01010
10101010101011010101101010101010101
Deluge Lessons
Advantages Ease of reprogramming 100’s-1000’s 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 100’s-1000’s of nodes :)
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
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 send[type](message) on the host event receive[type](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
GW
Client
Drain Collection Layer
Every node needs to send data to a gateway A generic single-message communication layer
command send[type](message) on the node event receive[type](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
GWGW
Client
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
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
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
Doesn’t make any extra demands on the network “If you’re going to send the packet anyway…” Passive management information gathering
Works when the network isn’t running the management layer Sometimes, you really need that extra few kB of code space
GW
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 don’t 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 don’t have a natural spatial realization
Our network is firmly embedded in space
The 10,000-Foot View
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 node’s 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
Nucleus Host Architecture
GW
Query Translator
Monitoring Daemon
Web Visualization
Command-Line Tools
GW
Packet Forwarder
Other Client Applications
XML-RPC
XML-RPC
Binary Data
XML-RPC
Binary Data
Pixels
Characters
Other Mgmt Tools