TinyOS Time to ROLL Routing over Low power and Lossy Networks

1
TinyOS Time to ROLL(Routing over Low power and
Lossy Networks)

• David E. Culler
• 1st European TinyOS Technology Exchange
• TTX VI
• Feb 10, 2009

2
A decade ago
3
Traditional Systems

• Well established layers of abstractions
• Strict boundaries
• Ample resources
• Independent Applications at endpoints communicate
  pt-pt through routers
• Well attended

Application
Application
User
System
Network Stack
Transport
Threads
Network
Address Space
Data Link
Files
Physical Layer
Drivers
Routers
4
by comparison, WSNs ...

• Highly Constrained resources
• processing, storage, bandwidth, power
• Applications spread over many small nodes
• self-organizing Collectives
• highly integrated with changing environment and
  network
• communication is fundamental
• Concurrency intensive in bursts
• streams of sensor data and network traffic
• Robust
• inaccessible, critical operation
• Unclear where the boundaries belong
• even HW/SW will move

• gt Provide a framework for
• Resource-constrained concurrency
• Defining boundaries
• Appln-specific processing and power management
• allow abstractions to emerge

5
Internet Research Perspectivethen

• Resource constraints may cause us to give up the
  layered architecture.
• Sheer numbers of devices, and their unattended
  deployment, will preclude reliance on broadcast
  communication or the configuration currently
  needed to deploy and operate networked devices.
• There are significant robustness and scalability
  advantages to designing applications using
  localized algorithms.
• Unlike traditional networks, a sensor node may
  not need an identity (e.g. address).
• It is reasonable to assume that sensor networks
  can be tailored to the application at hand.

6
And Now Complete IPv6 in TinyOS
Production implementation on TI msp430/cc2420

• Footprint, power, packet size, bandwidth

7
and in Open Source
8
and Power and Reliability
Data Rate Sensitivity (Router)
Data Rate Sensitivity (Edge)
Deployment Duty Cycle
Deployment Reliability
9
Where Did We Go Wrong?
10
Internet Networks of Networks
vs

• Networks
• Ethernet
• WiFi
• Serial links
• connect hosts and devices and other networks
  together
• Horizontally integrated

• Peripheral Interconnects
• USB, Firewire
• IDE / SCSI
• RS232,RS485
• IRDA
• BlueTooth
• connect one or more devices to a host computer
• Vertically integrated
• Physical link to application

11
Which are real sensors nets like?
Trending Monitoring
Data Analytics
Management
Ethernet
WiFi
RS232 RS485
GPRS
Controllers
Operations
Field Units
12
A Network Starts with a Router
13
Mote/TinyOS let chaos reign
WINS(UCLA/ROckwell)
Intel rene
SmartDust WeC
Rene
00
01
03
02
04
06
05
07
97
99
98
LWIM
Expedition
NEST
Cyber-Physical
SENSIT
NETS/ NOSS
CENS STC
DARPA
8 kB rom ½ kB ram
48 kB rom 10 kB ram 802.15.4
NSF
14
And rain it did
Application
Transport
Network
Link
15
A Low-Power Standard Link

• Low Transmit power, Low SNR, modest BW, Little
  Frames
• Reined in the Phy Chaos, allowed MAC chaos to
  Reign

16
Key Developments

• Event Driven Execution closely tied to storage
  mgmt
• reliable concurrency, small footprint, and
  low-power usage
• Idle listening
• Radio power transmit receive just listening
• All the energy is consumed by listening for a
  packet to receive
• E PTime
• gt Turn radio on only when there is something to
  hear
• Reliable routing on Low-Power Lossy Links
• Power, Range, Obstructions gt multi-hop
• Always at edge of SNR gt loss happens
• gt monitoring, retransmission, and local
  rerouting
• Trickle dont flood (tx rate lt 1/density, and
  lt info change)
• Connectivity is determined by physical points of
  interest, not network designer. May have huge
  number of neighbors, so
• never naively respond to a broadcast,
  re-broadcast very very politely

17
Meanwhile Key IPv6 Contributions

• Large simple address
• Network ID Interface ID
• Plenty of addresses, easy to allocate and manage
• Autoconfiguration and Management
• ICMPv6
• Integrated bootstrap and discovery
• Neighbors, routers, DHCP
• Protocol options framework
• Plan for extensibility
• Simplify for speed
• MTU discovery with min
• 6-to-4 translation for compatibility

18
IPv6 over 802.15.4 Not an obvious fit
UDP datagram or TCP stream segment
, modbus, BacNET/IP, , HTML, XML, , ZCL
transport header
application payload
Network packet
cls
flow
len
hops
src IP
dst IP
net payload
NH
16 B
16 B
?
Link frame
link payload
src UID
len
ctrl
chk
dst UID
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6LoWPAN adaptation layer
Diverse Object and Data Models (HTML, XML, ,
BacNet, )
7 app
Application (Telnet, FTP, SMTP, SNMP, HTTP)
Transport (UDP/IP, TCP/IP)
4 xport
Network (IP)
3 net
6LoWPAN
Link
2 link
Serial Modem
X3T9.5 FDDI
802.3 Ethernet
802.5 Token Ring
802.11 WiFi
802.15.4 LoWPAN
802.11a WiFi
802.3a Ethernet 10b2
802.11b WiFi
802.3i Ethernet 10bT
802.11g WiFi
ISDN
Sonet
802.3y Ethernet 100bT
802.11n WiFi
DSL
802.3ab Ethernet 1000bT
GPRS
802.3an Ethernet 1G bT
1 phy
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IPv6 Header Compression
v6
zero
In 802.15.4 header
derive from 802.15.4 header
derive from 802.15.4 header

• http//www.visi.com/mjb/Drawings/IP_Header_v6.pdf

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6LoWPAN IP Header Optimization
Network packet
40 B
net payload
cls
flow
len
hops
src IP
dst IP
NH
Link frame
3 B
src UID
len
hops
ctrl
chk
dst UID
6LoWPAN adaptation header

• Eliminate all fields in the IPv6 header that can
  be derived from the 802.15.4 header in the common
  case
• Source address derived from link address
• Destination address derived from link address
• Length derived from link frame length
• Traffic Class Flow Label zero
• Next header UDP, TCP, or ICMP
• Additional IPv6 options follow as options

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Energy Consumption Analysis


Payload ?
Energy ? for fixed payload
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Multi-Hop Communication gt Routing
PAN

• Short-range radios Obstructions gt Multi-hop
  Communication is often required
• i.e. Routing and Forwarding
• That is what IP does!
• Mesh-under multi-hop communication at the link
  layer
• Still needs routing to other links or other PANs
• Route-over IP routing within the PAN gt ROLL

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Embedded IPv6 in Concept
IP Link ? Always On
IP Link ? Reliable
25
AutoconfigurationConfiguring Large Numbers of
Interfaces
New Options
Existing Options
MHop Info
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AutoconfigurationConfiguring Large Numbers of
Interfaces
Stateless RFC 4861 4862
DHCPv6 RFC 3315
Response
Response
Request
2001abcd23
Request
2001abcd92
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Routing Forwarding
Delivering datagrams over multiple hops with High
reliability and Low Energy usage
Net
Router
ICMPv6
Forwarder
Routing Protocol
Multicast
Unicast
Buffer
Queue
Forwarding Table
Send Manager
Routing Table
Send Manager
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Cross-Fertilization of WSN and IETF ideas
Discovering Links
ICMPv6 Hdr
Router Adv
MHop Info
Building a Connectivity Graph
Low Routing Cost
High Routing Cost
Selecting the Next Hop

• Default route
• Hop-by-hop retry
• Reroute on loss

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Complete Embedded IPv6 Stack
App
DHCPv6
HTTP
Telnet
SNMP
DNS

Tran
Net
Router
ICMPv6
Autoconf
Routing Protocol
Routing Table
Stateless Autoconf
6LoWPAN Adaptation
Link
Media Management Control
Data
Ack
Remote Media
Link Stats
Local Media
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Adding up the pieces
Production implementation on TI msp430/cc2420
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So whats Next?
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Rein in the Chaos by layers
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Y-A-MAC?

• Yet-Another-MAC layer?
• If it is REALLY going to be a standard
• Interoperability within the PAN requires
  compatible MACs.
• 802.15.4 left a big hole
• Beaconing doesnt work
• No low power defined for FFD
• Perhaps the research community should stop
  differentiating and step forward to make one
  MAC stick
• Frame formats are not up for debate
• Visibility _at_ Link / Net Interface

34
Routing - really

• At layer 3
• Not 2, not 7, 3!
• Implemented with routing table, forwarder, and
  well-defined protocols
• Packets, States, Actions
• ROLL working group in IETF
• Application requirements
• Excellent Protocol Survey
• Entering actual work phase

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ROLL Internet Drafts

• draft-ietf-roll-protocols-survey -052009-01-26  
• draft-ietf-roll-terminology -00 2008-10-27  
• draft-ietf-roll-building-routing-reqs -05
  2009-02-04  
• draft-ietf-roll-home-routing-reqs -062008-11-19  
• draft-ietf-roll-indus-routing-reqs
  -042009-01-22  
• draft-ietf-roll-urban-routing-reqs -032009-01-08 

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The Heart of ROLL
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Transport

• Crazy not to support UDP and TCP
• Do we enter a TCP for LLNs renaissance?
• Do we define a new transport?
• What is the embedded sockets API?

38
Issues in Communication Abstraction

• Names
• What are they?
• What do they mean? What is their scope?
• How are they allocated?
• How are they translated into useful properties
• Address? Physical Resource?
• Storage
• Transmit
• When can it be reused? How do you know? What do
  you do when it is full?
• Receive
• When is it allocated? Reclaimed? By whom? What
  happens when it overflows?
• Asynchronous event
• How do you know that something has arrived?

39
Answers Naming

• TinyOS Active Messages
• TOS_local_addr, 16 bits, only within a network,
  allocated at program download time
• Scope limited to TOS_group, within PAN, Channel,
  and physical extent.
• The standards that try to do it all with IEEE
  802.15.4 16 bit short address are not much better
• IP Architecture
• Link name IEEE 802.15.4 gt EUID64 SA16
• EUID64 globally unique, SA16 assigned to be
  unique over the PAN
• Net name IP address
• Prefix Interface Id
• Must be unique within routability extent
• Several IP address Link Local, Global,
  Multicast,
• Service name Port
• Hostname Translated to IP by DNS

40
Answers Storage

• TinyOS Active Messages
• Sender app allocates send buffer, OS owns it till
  sendDone event
• OS provides App with recv buffer, app must return
  it or a replacement
• BSD Sockets
• Sender app allocate buffer, copied to kernel on
  send
• Receiver allocates buffer and passes pointer to
  kernel, kernel copies
• Additional sets of buffer managed within the
  kernel
• TinyOS Sockets ???

41
Example UDP Interface
interface Udp command error_t bind( uint16_t
port ) command uint16_t getMaxPayloadLength(
const sockaddr_in6_t to ) command error_t
sendto( const void buf, uint16_t len,
const sockaddr_in6_t to )
event void recvfrom( void buf, uint16_t len,
sockaddr_in6_t from, link_metadata_t
metadata )

• Wiring to a UDP interface is enough for sendto
  no allocate
• Standard Unix sockaddr_in6_t
• Bind associates the component that uses the
  interface with the port
• Starts receiving whatever datagrams come in on it
• Sendto sends a datagram from a buf to an IP
  destination
• Neighbor, intra-PAN, inter-network (wherever it
  needs to go!)
• Linklocal address is 1-hop neighbor
• Pan-wide routable prefix
• Error when not in network or overrun transmit
  resources
• Recvfrom gets a buffer with a datagram and
  metadata about it
• Able to fill the 15.4 frame without knowing
  details of header compression

42
Example UDP echo service
configuration EchoUdpC implementation
components KernelC components EchoUdpP as
EchoP EchoP.Boot -gt KernelC.Boot EchoP.Udp
-gt KernelC.Udp0
module EchoUdpP uses interface Boot,
Udp implementation event void
Boot.booted() call Udp.bind( ECHO_PORT )
/ bind to port 7 / event void
Udp.recvfrom( void buf, uint16_t len,
sockaddr_in6_t from,
link_metadata_t linkmsg ) call
Udp.sendto( buf, len, from ) / echo msg back
/
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And what about TCP

• UDP is a datagram transport
• Essentially the same as AM
• Fits naturally in event-driven model
• Can use NesC platform independent data structure
  to have unambiguous packet formats without hton /
  ntoh error prone bit twiddling.
• But TCP is a stream protocol

44
TCP Interface
interface Tcp command error_t
bind(uint16_t port, uint8_t buf, uint16_t
bufsize) event bool accept(
sockaddr_in6_t to ) command error_t connect(
const sockaddr_in6_t to, uint8_t buf,
uint16_t bufsize ) event void connected()
command error_t send( const void buf, uint16_t
len ) event void acked() event uint16_t
recv( void buf, uint16_t len ) command
error_t close( bool force ) event void
closed()

• Transitions of the TCP protocol reflected as
  events
• Recv per segment
• Here, appln allocates send buffer but stack
  manages it.
• Send is not split-phase (!!!)

45
TCP echo server
module EchoTcpP uses interface Boot,
Tcp implementation uint8_t m_buf
BUF_SIZE / Transmit
buffer / event void Boot.booted()
call Tcp.bind( ECHO_PORT, m_buf, sizeof(m_buf)
) event bool Tcp.accept( sockaddr_in6_t
to ) return TRUE event void
Tcp.connected() event void Tcp.acked()
event uint16_t Tcp.recv( void buf,
uint16_t len ) return ( call Tcp.send(
buf, len ) SUCCESS ) len ? 0 event
void Tcp.closed() / setup socket for new
connection / call Tcp.bind( ECHO_PORT,
m_buf, sizeof(m_buf) )
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Event-Driven Execution of Services
Service request
Fire
recv
47
Split-Phase Data Acquisition
Sample
Read
48
Examples - Tasks
serviceReq
Sample
notify
fired
readDone
fired
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HTTP
event bool HttpTcp.accept( sockaddr_in6_t to )
serverState LISTENING return TRUE
event void HttpTcp.connected()
serverState CONNECTED init_pump()
event uint16_t HttpTcp.recv( void inbuf,
uint16_t len ) if (httppump(inbuf,len))
switch (http_method) case HTTP_GET
signal Http.GETservice (url, uindex) break
case HTTP_POST signal Http.POSTservice(url,
uindex) break default call
HttpTcp.close( FALSE ) return
len command error_t Http.serviceDone()
call HttpTcp.close( FALSE ) return
SUCCESS command error_t Http.send( const
void buf, uint16_t len ) return call
HttpTcp.send( buf, len ) event void
HttpTcp.acked() event void
HttpTcp.closed()call HttpTcp.bind(port, resp,
respLen)
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Resource Blueprint at the Top
configuration WebSense implementation
components KernelC components WebC as WebC
/ Web request service /
components HttpC as HttpC / TCP
HTTP (port 80) service / components new
TimerMilliC() as HttpTimer / Protocol deadman
/ components Msp430Adc12C /
Hardware ADC abstraction / components
Msp430PortsC / Hardware IO
Ports / WebC.Http -gt
HttpC.Http / Protocol interface / WebC.Boot
-gt KernelC.Boot WebC.IPv6Addresses
-gt KernelC.IPv6Addresses WebC.Time
-gt KernelC.GlobalTime HttpC.HttpTcp -gt
KernelC.Tcp0 HttpC.IPv6Addresses -gt
KernelC.IPv6Addresses HttpC.Timer -gt
HttpTimer / Digital inputs / components
new DigitalInC("Door") as Din0 WebC.Door -gt
Din0.DigitalIn Din0.Pin -gt
Msp430PortsC.Port12 Din0.PinInt -gt
Msp430PortsC.Port1Interrupt2 / Analog
inputs / components TempIntC WebC.Temp -gt
TempIntC.TempInt TempIntC.ADC -gt
Msp430Adc12C.Msp430Adc12INCH_10 / Internal
temp / components new AnalogInC(REFVCC, "Pot")
as TrimPot WebC.Pot -gt TrimPot.Sensor
TrimPot.ADC -gt Msp430Adc12C.Msp430Adc12INCH_4

51
or if you prefer Zigbee Profiles

• http//www.ietf.org/internet-drafts/draft-tolle-ca
  p-00.txt
• A UDP/IP Adaptation of the ZigBee Application
  Protocol

52
what it means for sensors

• Low-Power Wireless Embedded devices can finally
  be connected using familiar networking
  technology,
• like ethernet (but even where wiring is not
  viable)
• and like WiFi (but even where power is not
  plentiful)
• all of these can interoperate in real
  applications
• Interoperate with traditional computing
  infrastructure
• Utilize modern security techniques
• Application Requirements and Capacity Plan
  dictate how the network is organized,
• not artifacts of the underlying technology
• Gateways and Proxies may or may not be at the
  media boundary

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Making sensor nets make sense

• LoWPAN 802.15.4
• 1 of 802.11 power, easier to embed, as easy to
  use.
• 8-16 bit MCUs with KBs, not MBs.
• Off 99 of the time

Web Services
XML / RPC / REST / SOAP / OSGI
HTTP / FTP / SNMP
TCP / UDP
ROLL
IP
802.15.4,
802.11
Ethernet
Sonet
IETF 6lowpan
54

• Thanks

55
Technology Transformation - Bottom Line
Network
Microcontroller
Flash Storage
Radio

• Sensors have become physical information
  servers
• Treat them as information servers

56
Industrial Interconnects

• BACnet
• RS-232 RS-485 gt IEEE 802.3 via BACnet/IP
• LONworks
• Twisted Pair Power Line gt LonTalk/IP
• Common Industrial Protocol (CIP)
• CAN ControlNet gt EtherNet/IP
• SCADA
• Prop. RS-485 Leased Line Prop. Radios gt
  ModBUS gt Ethernet gt TCP/IP
• FieldBus
• Modbus, Profibus, Ind. Ethernet, Foundation HSE,
  H1, SP100.11a?

In 2000, ODVA and CI introduced another member of
the CIP family EtherNet/IP, where IP stands
for Industrial Protocol. In this network
adaptation, CIP runs over TCP/IP and therefore
can be deployed over any TCP/IP supported data
link and physical layers, the most popular of
which is IEEE 802.311, commonly known as
Ethernet. The universal principles of CIP easily
lend themselves to possible future
implementations on new physical/ data link
layers. The Common Industrial Protocol (CIP) and
the Family of CIP Networks (Pub 123 )
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A Decade Ago