rpl telecom bretagne
TRANSCRIPT
RPL and wireless fringe
Telecom Bretagne, Mars 2013
Pascal Thubert
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Scaling to Pervasive IoE/T
1000*scale => No leak in the Internet
=> Opaque Fringe operations
Reachability => Radio
Addressing => IPv6
Density => spatial
reuse
=> Routing
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Agenda (part 1)
The Fringe of the Internet
Radios and LLNs
IEEE 802.15.4
Mesh-Under Fringe
Route-Over Fringe
Overlay Fringe
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Agenda (Part 2)
The RPL Fringe protocol
Going IP
Routing IP
Routing over Radio
RPL concepts
Applying RPL
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The Fringe of the Internet
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The routing Infrastructure today
The Internet
Fully engineeredHierarchical, Aggregations, ASs, Wire links
Fully distributed StatesShows limits (BGP tables, addr. depletion)
Þ Reached adult size, mature to agingÞ Conceptually unchanged by IPv6
IPv4 Intranets Same structure as the Internet Yet decoupled from the Internet
NAT, Socks, Proxies
Þ First model for Internet extension
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L2 mesh UnderMulti-hop Public Access Points, Proprietary mission specific productsAddress the scale issue at L2/ND
L3 Route OverMigration to IETF Protocols (RPL)Internet of Things (IOT, M2M)Different IPv6 (6LoWPAN, SDN)
Mobile OverlaysGlobal reachability Route ProjectionNetwork virtualization
Fixed wired Infrastructure
56
78
CB
1
32
A4
A’s Home
B’sHome
MANETMesh The Fringe DOES NOT LEAK
into the Routing Infrastructure
NEMO
The emerging Fringe of the Internet
Edge
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Radios and LLNs
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Wireless: the evolution trait
Cheap InstallDeploying wire is slow and costly
Global CoverageFrom Near Field to Satellite via 3/4G
Everywhere copper/fiber cannot reach
Cheap multipoint accessNew types of devices (Internet Of Things)
New usages (X-automation, Mobile Internet)
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Low Power Lossy Network (LLN)
LLNs comprise a large number of highly constrained devices (smart objects) interconnected by predominantly wireless links of unpredictable quality
LLNs cover a wide scope of applicationsIndustrial Monitoring, Building Automation, Connected Home, Healthcare, Environmental Monitoring, Urban Sensor Networks, Energy Management, Asset Tracking, Refrigeration
Several IETF working groups and Industry Alliance addressing LLNs
IETF - CoRE, 6Lowpan, ROLL
Alliances - IP for Smart Objects Alliance (IPSO)
World’s smallest web server
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Characteristics of LLNs
LLNs operate with a hard, very small bound on state
LLNs are optimised for saving energy in the majority of cases
Traffic patterns can be MP2P, P2P and P2MP flows
Typically LLNs deployed over link layers with restricted frame-sizes
Minimise the time a packet is enroute (in the air/on the wire) hence the small frame size
The routing protocol for LLNs should be adapted for such links
LLN routing protocols must consider efficiency versus generality
Many LLN nodes do not have resources to waste
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IETF LLN Related Workgroups
Reuse work done here where possible
Application
General
Internet
Ops and Mgmt
Routing
Security
Transport
Core
6LowPAN
ROLL
IETF LWIG
Constrained Restful Environments
Charter to provide a framework for resource-oriented applications intended to run on constrained IP networks.
IPv6 over Low power WPANCharter is to develop protocols to support IPv6 running over IEEE 802.15.4 low-power radio
networks.
Routing over Low Power Lossy Networks
Charter focusses on routing issues for low power lossy networks.
Lightweight Implementation GuidanceCharter is to provide guidance in building
minimal yet interoperable IP-capable devices for the most constrained environments. .
6TSCH
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IEEE 802.15.4
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802.15.4 Scope Initial activities focused on wearable
devices “Personal Area Networks”
Activities have proven to be much more diverse and varied
Data rates from Kb/s to Gb/s
Ranges from tens of metres up to a Kilometre
Frequencies from MHz to THz
Various applications not necessarily IP based
Focus is on “specialty”, typically short range, communications
If it is wireless and not a LAN, MAN, RAN, or WAN, it is likely to be 802.15 (PAN)
The only IEEE 802 Working Group with multiple MACs
“The IEEE 802.15 TG4 was chartered to investigate a low data rate solution with multi-month to multi-year battery life and very low complexity. It is operating in an unlicensed, international frequency band. Potential applications are sensors, interactive toys, smart badges, remote controls, and home automation.”
http://www.ieee802.org/15/pub/TG4.htmlIEEE 802.15 WPAN™ Task Group 4 (TG4) Charter
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IEEE Wireless Standards
802.11 Wireless LAN
802.15 Personal Area Network
802.16 Wireless Broadband Access
802.22 Wireless Regional Area Network
WiFi 802.11a/b/g/n/ah
IEEE 802 LAN/MAN
802.15.1Bluetooth
802.15.2Co-existence
802.15.3 High Rate WPAN
802.15.4 Low Rate WPAN
802.15.5 Mesh Networking
802.15.6 Body Area Networking
802.15.7 Visible Light
Communications
802.15.4eMAC Enhancements
802.15.4fPHY for RFID
802.15.4gSmart Utility Networks
TV White Space PHY 15.4 Study Group
802.15.4dPHY for Japan
802.15.4cPHY for China
• Industrial strength• Minimised listening costs• Improved security• Improved link reliability
802.15.4Amendments
• Support smart-grid networks• Up to 1 Km transmission• >100Kbps • Millions of fixed endpoints• Outdoor use• Larger frame size• PHY Amendment• Neighborhood Area Networks
TSCH
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IEEE 802.15.4 Features
Designed for low bandwidth, low transmit power, small frame size
More limited than other WPAN technologies such as Bluetooth
Basic packet size is 127 bytes (802.15.4g is up to 2047 bytes) (Smaller packets, less errors)
Transmission Range varies (802.15.4g is up to 1km)
Fully acknowledged protocol for transfer reliability
Data rates of 851, 250, 100, 40 and 20 kbps (IEEE 802.15.4-2011 05-Sep-2011)
Frequency and coding dependent
Two addressing modes; 16-bit short (local allocation) and 64-bit IEEE (unique global)
Several frequency bands (Different PHYs)
Europe 868-868.8 MHz – 3 chans , USA 902-928 MHz – 30 chans, World 2400-2483.5 MHz – 16 chans
China - 314–316 MHz, 430–434 MHz, and 779–787 MHz Japan - 920 MHz
Security Modes: None, ACL only, Secured Mode (using AES-CCM mode)
802.15.4e multiple modes including Time Synchronized Channel Hopping (TSCH)
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802.15.4 Protocol Stack
Specifies PHY and MAC only
Medium Access Control Sub-Layer (MAC)Responsible for reliable communication between two devices
Data framing and validation of RX frames
Device addressing
Channel access management
Device association/disassociation
Sending ACK frames
Physical Layer (PHY)Provides bit stream air transmission
Activation/Deactivation of radio transceiver
Frequency channel tuning
Carrier sensing
Received signal strength indication (RSSI)
Link Quality Indicator (LQI)
Data coding and modulation, Error correction
Physical Layer(PHY)
MAC Layer(MAC)
Upper Layers
(Network & App)
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IEEE 802.15.4e Amendment to the 802.15.4-2006 MAC needed for the applications
served by 802.15.4f PHY Amendment for Active RFID
802.15.4g PHY Amendment for Smart Utility Networks
initially for Industrial applications
(such as those addressed by wiHART and the ISA100.11a standards)
Security: support for secured ack
Low Energy MAC extensionCoordinated Sampled Listening (CSL)
Channel HoppingNot built-in, subject to vendor design. Open std work started with 6TSCH
New Frame TypesEnhanced (secure) Acknowledgement (EACK)
Enhanced Beacon and Beacon Request (EB and EBR)
Optional Information Elements (IE)
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IEEE 802.15.4 Node Types
Full Function Device (FFD)Can operate as a PAN co-ordinator (allocates local addresses, gateway to other PANs)
Can communicate with any other device (FFD or RFD)
Ability to relay messages (PAN co-ordinator)
Reduced Function Device (RFD)Very simple device, modest resource requirements
Can only communicate with FFD
Intended for extremely simple applications
P
R F
F
R
R
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• Star Topology • Cluster Tree• Mesh Topology
IEEE 802.15.4 Topologies
P
R F
F
R
R
P
F F
F
R
F
R
• All devices communicate to PAN co-ordinator which uses mains power
• Other devices can be battery/scavenger
Single PAN co-ordinator exists for all topologies
• Devices can communicate directly if within range
F F
F
F
P
R
R
F
R
Operates at Layer 2
R
R
RR
• Higher layer protocols like RPL may create their own topology that do not follow 802.15.4 topologies
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The Mesh-Under Fringe
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Wireless Industrial
• Better process optimization and more accurate predictive maintenance increase profit; 1% improvement in a refinery with a $1.5B annual profit leads to $40k/day ($15M/yr) more profit
• Thus more and different sensors can be justified economically, if they can be connected
• But wire buried in conduit has a high installation and maintenance cost, with long lead times to change, and is difficult to repair
• The solution: wireless sensors in non-critical applications, designed for the industrial environment: temperature, corrosion, intrinsic safety, lack of power sources (particularly when there is no wire)
• For critical control loops, use wireless control room links with controllers located in the field, possibly connected over local wiring
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ISA100: Wireless Systems for Industrial Automation
ISA100.11a industrial WSNWireless systems for industrial automation
Process control and related applications
Leverages 802.15.4(e) + IPv6Link Local Join process
Global Address runtime
6LoWPAN Header Compression
Yet specific routing and ND
Next: Backbone Router
ISA100.15 backhaul
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The Route-Over Fringe
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EmergencyHotSpot
(roadside)
SOS
!
Mobile Router
Mobile Router
IPv6
IPv6
IPv6
Swarming
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Sensor Dust
“Sensor dust” spread over a territory
Sensors assume a fixed arbitrary geographical distribution
Numerous sensors with limited capabilities (battery …)
A limited number of relays (MR)
MRs run an SGP (RPL)
2 to 3 uplinks (MR with backhaul capability)
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Fleet
Global motion plus relative mobility
Managed hierarchy over dynamic topology
Secured uplink to base
Dark Zone coverage and range extension (nesting)
TLMR
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Internet
MR1
CN
HA1
HA1: HA of MR1HA2: HA of MR2HA-VMN: HA of VMNCR: Correspondent Router
HA2
VMN
MR2
HA
CN2CN1
Nested NEMO Route optimization
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Mobile Internet of Everything
Couple LISP/MIP/NEMO with global mobility with local meshing/routing (typically RPL)
Locator is root, routing between device identifiers
e.g. Home Network
Clusterhead0
1
11
2
2
2
22
3
3
3
3
3
3
23
5
4
4
4
4
LISP /MIP /NEMO
Constrained routing
Potential link
Default routing
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RPL (pronounced ripple) TheFringeRouting Protocol
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Why IPv6 ?
Going IP
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Why IP ?
Open Standards vs. proprietaryCOTS* suppliers drive costs down but
Reliability, Availability and Security up
IP abstraction vs. per MAC/App
802.11, 802.15.4 (e), Sat, 3G, UWB
Keep L2 topology simple
To Infinity and Beyond… But End-to-End.No intermediate gateway, tunnel, middle boxes & other trick
* Commercial, off-the-shelf
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Tens of Billions Smart ObjectsThings
Which IP version ?
The current Internet comprises several billion devices
Smart Objects will add tens of billions of additional devices
IPv6 is the only viable way forward
1~2 Billions PCs & servers
Mobile
Fixed
2~4 Billions Phones & cars
IPv4 Unallocated pool exhausted March 2011 !APNIC: May 2011; RIPE NCC: Sept 2012 (last /8)
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Protocol Evolution
Little work on adapting IPv4 to radiosRather adapt radios to IPv4 e.g. WIFI infrastructure mode
« Classical » IPv6 Large, Scoped and Stateful addresses
Neighbor Discovery, RAs (L3 beacons)
SLAAC (quick and scalable)
Anycast Addresses
IPv6 evolution meets Wireless:
Mobile Routers (LISP, NEMO) (Proxy) MIPv6
6LoWPAN 6TSCH ROLL/RPL CoAP
ISA100.11a ZigBee/IP
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IPv6 still lacks
NBMA / ML subnetIPv6 only supports P2P and transit (ethernet)
By nature, a radio network is NBMA
L3 « VLAN »So far only available with MPLS
Early attempts (MTR, RPL instances)
L4/5 hintsFlow Label given away to fwd plane
Microflows / compound flowsIn WSN, a flow has multiple sources
Local and Global IP Mobility Unification(eg MANEMO, LISP+RPL)
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Routing IP
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Routing for Spatial Reuse
Hidden terminal
Interference domains grows faster that range
Density => low power => multihop => routing
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Proactive vs. Reactive
Aka
stateful
vs.
On-demand routing
Note: on-demand breaks control vs. Data plane separation
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Link State vs. Distance Vector
Aka SPF vs. Bellman-Ford
LS requires full state and convergence
LS can be very quiet on stable topologies
DV hides topolical complexities and changes
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0
Route stretch and fisheye
Optimized Routing Approach (ORA) spans advertisements for any change
Routing overhead can be reduced if stretch is allowed: Least Overhead Routing Approach (LORA)
For instance Fisheye and zone routing provide a precise routing when closeby and sense of direction when afar
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DAG, DODAG
In the context of routing, a Directed Acyclic Graph (DAG) is formed by a collection of vertices (nodes) and edges (links).
Each edge connecting one node to another (directed) in such a way that it is not possible to start at Node X and follow a directed path that cycles back to Node X (acyclic).
A Destination Oriented DAG (DODAG) is a DAG that comprises a single root node.
Here a DAG that is partitioned in 2 DODAG
Clusterhead
5
4
4
01
3
1 1
2
2
2
22
3
3
3
3
3
3
2
4
4
5
0
65
4
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SubDAG, and Fanout DAG
In Green: A’s subDAG. Impacted if A’s connectivity is broken
Domain for routing recovery
In Red: B’s fanout DAG (or reverse subDAG)
Potential SPAN on B’s DAO
Thus potential return paths
Fanout must be controlled to limit intermediate states
Clusterhead
5
4
4
01
3
1 1
2
2
2
22
3
3
3
3
3
3
2
4
4
5
0
65
4
A
B
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Routing over Radio
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Dynamic topologies
No preexisting physical topologyCan be computed by a mesh under protocol, but…
Else Routing must infer its topology
Movement natural and unescapable
Yet difficult to predict or detect
Topology Update
Routing Update
Fast => expensive
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Peer selection
Potentially Large Peer Set
Highly Variable Capabilities
Selection Per Objective{Metrics (e.g. RSSI, ETX…)
L3 Reachability (::/0, …)
Constraints (Power …)
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Constrained Objects
Smart object are usually Small & Numerous
« sensor Dust »
Battery is criticalDeep Sleep
Limited memory
Small CPU
Savings are REQUIREDÞ Control plane
Þ Data plane (Compression)
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Fuzzy links
Neither transit nor P2P
More like a changing NBMAa new paradigm for routing
Changing metrics(tons of them!)
(but no classical cost!)
Inefficient floodingSelf interfering
QoS and CAC
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Local Routing & Mobility
Stretch vs. ControlOptimize table sizes and updates
Optimized Routing Approach (ORA) vs
Least Overhead Routing Approach (LORA)
on-demand routes (reactive)
Forwarding and retriesSame vs. Different next hop
Validation of the Routing plane
Non Equal Cost multipath Directed Acyclic Graphs (DAG) a MUST
Maybe also, Sibling routing
Objective Routing Weighted Hop Count the wrong metric
Instances per constraints and metrics
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Global Mobility
Pervasive AccessSatellite
3/4G coverage
802.11, 802.15.4
Always Reachableat a same identifier
Preserving connections
Or not ? (CORE*, DTN**)
Fast roamingWithin technology (L2)
Between Technologies (L3)
* Constrained RESTful Environments
** Delay-Tolerant Networking
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What’s missing
A radio abstraction 802.21, L2 triggers, OmniRAN
Roaming within and between technologies
TSCH model
A subnet modelNBMA, interference awareness
Federation via backbone / backhaul
Broadcast and look up optimizationLarge scale
non-aggregatable
numbering and naming schemes
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RPL concepts
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Routing With RPL
Dynamic Topologies
Peer selection
Constrained Objects
Fuzzy Links
Routing, local Mobility
Global Mobility
Low Power Lossy Nets Addressed in RPL ?
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RPL key concepts
Minimum topological awareness
Data Path validation
Non-Equal Cost Multipath Fwd
Instantiation per constraints/metrics
Autonomic Subnet G/W Protocol
Optimized Diffusion over NBMA
RPL is an extensible proactive IPv6 DV protocol Supports MP2P, P2MP and P2P P2P reactive extension
RPL specifically designed for LLNsAgnostic to underlying link layer technologies (802.15.4, PLC, Low Power WiFi)
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Controlling the control … by design
Distance Vector as opposed to Link StateKnowledge of SubDAG addresses and children links
Lesser topology awareness => lesser sensitivity to change
No database Synchronization => Adapted to movement
Optimized for Edge operation
Optimized for P2MP / MP2P, stretch for arbitrary P2P
Least Overhead Routing Approach via common ancestor
Proactive as opposed to Reactive
Actually both with so-called P2P draft
Datapath validation
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Datapath Validation
Control Information in Data Packets:
Instance ID
Hop-By-Hop Header Sender Rank
Direction (UP/Down)
Errors detected if:
- No route further down for packet going down
- No route for packet going down
- Rank and direction do not match
{
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In the context of routing, a DAG is formed by a collection of vertices (nodes) and edges (links), each edge connecting one node to another (directed) in such a way that it is not possible to start at Node X and follow a directed path that cycles back to Node X (acyclic).
Directed Acyclic Graph for NECM
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Generic Rank-based Loop Avoidance
1) A root has a Rank of 1. A router has a Rank that is higher than that of its DAG parents.
2) A Router that is no more attached to a DAG MUST poison its routes, either by advertising an INFINITE_RANK or by forming a floating DAG.
3) A Router that is already part of a DAG MAY move at any time in order to get closer to the root of its current DAG in order to reduce its own Rank
4) But the Router MUST NOT move down its DAG – but under controlled limits whereby the router is allowed a limited excursion down
5) A Router MAY jump from its current DAG into any different DAG at any time and whatever the Rank it reaches there, unless it has been a member of the new DAG in which case rule 4) applies
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0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RPLInstanceID |Version Number | Rank | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |G|0| MOP | Prf | DTSN | Flags | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + DODAGID + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option(s)... +-+-+-+-+-+-+-+-+
DIO Base Object: forming the DODAG
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Global versus Local Repair
Global repair: : A new DODAG iterationRebuild the DAG … Then repaint the prefixes upon changes
A new Sequence number generated by the root
A router forwards to a parent or as a host over next iteration
Local Repair: find a “quick” local repair path Only requiring local changes !
May not be optimal according to the OF
Moving UP and Jumping are cool.
Moving Down is risky: Count to Infinity Control
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Objective Function
Extend the generic behaviorFor a specific need / use case
Used in parent selectionContraints
Policies Position in the DAG
Metrics
Computes the Rank incrementBased on hop metrics
Do NOT use OF0 for adhoc radios!
(OF 0 uses traditional weighted hop count)
{
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0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RPLInstanceID |Version Number | Rank | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |G|0| MOP | Prf | DTSN | Flags | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + DODAGID + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option(s)... +-+-+-+-+-+-+-+-+
DIO Base Object: route construction rules
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Mode of Operation
+-----+-----------------------------------------------------+
| MOP | Description |
+-----+-----------------------------------------------------+
| 0 | No Downward routes maintained by RPL |
| 1 | Non-Storing Mode of Operation |
| 2 | Storing Mode of Operation with no multicast support |
| 3 | Storing Mode of Operation with multicast support |
| | |
| | All other values are unassigned |
+-----+-----------------------------------------------------+
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DAO Base Object : route construction
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RPLInstanceID |K|D| Flags | Reserved | DAOSequence |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ DODAGID* +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option(s)...
+-+-+-+-+-+-+-+-+
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Owned prefix routing (storing mode)
A
B
C D
Parent is default GW, advertizes owned PIO (L bit on)
RPL Router autoconfigures Addr from parent PIO
RPL Router advertises Prefix via self to parent
RPL Router also advertises children Prefix
B:
::/0 via A::A
A:: connected
B:: connected
C:: via B::C
D:: via B::D
C:
::/0 via B::B
B:: connected
C:: connected
A:
A:: connected
B:: via A::B
C:: via A::B
D:: via A::BD:
::/0 via B::B
B:: connected
D:: connected
A::B
B::C B::D
B::B
A::A
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Subnet Routing (storing mode)
A
B
C D
Parent is default GW, propagates root PIO (L-bit off)
Parent Address in the PIO (with R bit)
RPL Router autoconfigures Address from parent PIO
RPL Router advertises Address via self to parent
RPL Router also advertises children Addresses
B:
::/0 via A::A
A::A connected
A::B self
A::C connected
A::D connected
A:: ~onlink
C:
::/0 via A::B
A::B connected
A::C self
A:: ~onlink
A:
A::A self
A::B connected
A::C via A::B
A::D via A::B
A:: ~onlink
D:
::/0 via A::B
A::B connected
A::D self
A:: ~onlink
A::B
A::C A::D
A::A
For YourReference
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Subnet Routing (non-storing mode)
A
B
C D
Parent is default GW, propagates root PIO (L-bit off)
Parent Address in the PIO (with R bit)
RPL Router autoconfigures Address from parent PIO
RPL Router advertises Address via Parent to Root
Root recursively builds a Routing Header back
B:
::/0 via A::A
A::A connected
A::B self
A:: ~onlink
C:
::/0 via A::B
A::B connected
A::C self
A:: ~onlink
D:
::/0 via A::B
A::B connected
A::D self
A:: ~onlink
Target A::C viaTransit A::BA::B
A::C A::D
A::A
A: (root)
A::A self
A::B connected
A::C via A::B
A::D via A::B
A:: ~onlink
A::D via A::B connectedRH4:
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Owned prefix routing (non-storing mode)
A
B
C D
Parent is default GW, advertizes owned PIO (L bit on)
RPL Router autoconfigures Address from parent PIO
RPL Router advertises Prefix via Address to Root
Root recursively builds a Routing Header back
B:
::/0 via A::A
A:: connected
B:: connected
C:
::/0 via B::B
B:: connected
C:: connected A: (root)
A:: connected
B:: via A::B
C:: via B::C
D:: via B::DD:
::/0 via B::B
B:: connected
D:: connected
Target C::/ viaTransit B::C
D::3 via B::D via A::B connected
A::B
B::C B::D
B::B
A::A
RH4:
For YourReference
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Multicast over radio NBMA
Flooding interferes with itself
B
C
D
A
Hidden node/terminal/station
1
2 ’’2’
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Trickle:An Optimized Diffusion
Suppression of redundant copies Do not send copy if K copies received
Jitter for Collision AvoidanceFirst half is mute, second half is jittered
Exponential backoffDouble I after period I, Reset I on inconsistency
I
2*I
K = 4
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Routing Metrics in LLNs
Node Metrics Link Metrics
Node State and Attributes ObjectPurpose is to reflects node workload (CPU,
Memory…)“O” flag signals overload of resource“A” flag signal node can act as traffic
aggregator
Throughput ObjectCurrently available throughput (Bytes per
second)Throughput range supported
Node Energy Object“T” flag: Node type: 0 = Mains, 1 = Battery, 2 =
Scavenger“I” bit: Use node type as a constraint
(include/exclude)“E” flag: Estimated energy remaining
LatencyCan be used as a metric or constraintConstraint - max latency allowable on pathMetric - additive metric updated along path
Hop Count ObjectCan be used as a metric or constraintConstraint - max number of hops that can be
traversedMetric - total number of hops traversed
Link ReliabilityLink Quality Level Reliability (LQL)
0=Unknown, 1=High, 2=Medium, 3=LowExpected Transmission Count (ETX)
(Average number of TX to deliver a packet)
Link ColourMetric or constraint, arbitrary admin value
For YourReference
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Applying RPL
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RPL Terminology
5
3
5
4
RPL Instance Consists of one or more DODAGs sharing SAME service type (Objective Function)Identified by RPL INSTANCE ID
UP
(DA
O M
essages)
DODAG RootIdentified by DODAG ID
(Node IPv6 address)
Direction Oriented DAG (DODAG)Comprises DAG with a single root
Rank
Towards
DO
DA
G
Root
Rank = n
Rank < n
Node(OF
configured)
2
1
5
4
3
3
Rank d
ecreases
DODAG parent to child “5”s
2
DODAG RootRank is always “1”(Typically an LBR - LLN Border Router)
1
3
2
Sub-DODAG
DODAG
DO
WN
(D
IO M
essa
ges)
Tow
ards
D
OD
AG
le
afs
Rank > n
Rank = n
Ran
k in
crea
ses
Non-LLN Network
(IPv6 Backbone)
Non-LLN Network
(IPv6 Backbone)
Siblings
44
DODAG
Sensor Node
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Example radio connecticity
At a given point of time connectivity is
(fuzzy)
Radio link
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Clusterhead
1st pass (DIO)Establishes a logical DAG topology
Trickle Subnet/config Info
Sets default route
Self forming / self healing
2nd pass (DAO) paints with addresses and prefixes
Any to any reachability
But forwarding over DAG only
saturates upper links of the DAG
And does not use the full mesh properly
Applying RPL
Link selected as parent link
Potential link
Clusterhead0
1
11
4
44
46
3
3
3
3
3
2
2
2
22
2
5
55
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Clusterhead
A’s link to root failsA loses connectivity
Either poisons or detaches a subdag
In black:
the potentially impacted zone
That is A’s subDAG
Local recovery (step 1)
Link selected as parent link
Potential link
Clusterhead0
1
11
4
44
46
3
3
3
3
3
2
2
2
22
2
5
55
A
1
11
3
3
3
3
3
2
2
2
22
2
5
55
4
44
4
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Clusterhead
B can reparent a same Rank so B’s subDAG is safe
The rest of A’s subDAG is isolated
Either poison ar build a floating DAG as illustrated
In the floating DAG A is root
The structure is preserved
Local recovery (step 2)
Link selected as parent link
Potential link
Clusterhead0
1
1
4
44
46
3
3
3
2
2
2
2
2
21
5
55
AB
0
1
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Clusterhead
Once poisined nodes are identified
It is possible for A to reparent safely
A’s descendants inherit from Rank shift
Note: a depth dependent timer can help order things
Local recovery (step 3)
Link selected as parent link
Potential link
Clusterhead0
1
12
4
44
46
3
3
3
4
4
2
2
2
23
3
5
55
A
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Clusterhead
A new DAG iterationIn Green, the new DAG progressing
Metrics have changed, the DAG may be different
Forwarding upwards traffic from old to new iteration is allowed but not the other way around
Global recovery
Link selected as parent link
Potential link
Clusterhead0
1
11
4
44
46
3
3
3
3
3
3
2
2
22
2
5
55
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Clusterhead
5
4
4
A second root is available(within the same instance)
The DAG is partitioned
1 root = 1 DODAG
1 Node belongs to 1 DODAG(at most, per instance)
Nodes may JUMP from one DODAG to the next
Nodes may MOVE up the DODAG
Going Down MAY cause loopsMay be done under CTI control
Multiple DODAGs within Instance
Link selected and oriented by DIO
Potential link
01
3
1 1
2
2
2
22
3
3
3
3
3
3
2
4
4
5
0
65
4
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Multiple Instances
Running as Ships-in-the-night
1 instance = 1 DAG
A DAG implements constraints
Serving different Objective Functions
For different optimizations
Forwarding along a DODAG (like a vlan)
Clusterhead0
1
11
2
2
2
22
3
3
3
3
3
3
23
5
4
4
4
4
Clusterhead
Constrained instance
Default instance
Potential link
A
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Simulation Results
Traffic Control
Traffic Holes – Global Repair only
Routing Table Sizes
For YourReference
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Summary
DV, ORA P2MP/MP2P, LORA P2P
Objective Functions, Metrics
Controlling the control
NECM Directed Acyclic Graphs Trickle and Datapath validation
Local and Global Recovery
N/A
Dynamic Topologies
Peer selection
Constrained Objects
Fuzzy Links
Routing, local Mobility
Global Mobility
New Radios issues: Addressed in RPL by:
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Next steps…
Reactive model (in IESG review, aka P2P RPL)
PCE (ala TSMP/ISA100.11a/WiHART)
DAG limitationsSibling routing, more resilient schemes (ARCs)
Stimulated updates (lookup)
Asymmetrical links
Multi-Topology routing and cascading
A model for 802.15.4e
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Conclusion
The Internet is going through its most considerable change since the first days
Made possible by IPv6 But not at the core and unbeknownst to the core
Stimulated by radio access Enabling new devices and usages
The change happens in the Fringe, which is in fact a collection of virtualized fringes
L2 divide vs. L3 and L4
Home, IOT, cars, datacenters, industrial…
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RPL – IETF suite RFC 6206: The Trickle Algorithm
RFC 6550: RPL: IPv6 Routing Protocol for LLNs
RFC 6551: Routing Metrics Used for Path Calculation in LLNs
RFC 6552: Objective Function Zero for the Routing Protocol for LLNs
RFC 6553: RPL Option for Carrying RPL Information in Data-Plane Datagrams
RFC 6554: An IPv6 Routing Header for Source Routes with RPL
RFC 6719: MRHOF Objective Function with hysteresis
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“We might be at the eve of pervasive networking, a vision for the Internet where every person and every device is connected to the network in the ultimate realization of Metcalf's Law.”
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Questions