1. The Semantic IoT Amr El Mougy Slim Abdennadher Ghada Fakhry

2. Routing for Low Power and Lossy Networks

3. Low Power and Lossy Networks Nodes are typically small in size, operate on small batteries, and have restricted capabilities Networks are connected using wireless links (ZigBee, WiFi), which are lossy Network topology is dynamic. Links are unstable and nodes join and leave at any time Applications include industrial automation, home monitoring (HVAC), healthcare, environment monitoring, tracking, etc. Not all LLNs are WSNs, but all WSNs are LLNs Not all LLNs are wireless All LLNs will use IPv6. A big area for merging with 6LowPAN Existing Routing Protocols do not work for LLNs

4. Addressing Schemes in Sensor Networks Attribute-based: nodes do not have an identity but rather the data is labeled, often according to the application Geographic based: the identity of the nodes are their coordinates. Localization schemes are required (GPS or otherwise) Address-centric: each node is given an ID, such as IP addresses Spatial IP: the last two octets of each node’s IP address are its (x, y) coordinates Address-free: each transaction may have a different ID

5. Data Delivery Models Event-driven: data is generated in response to an event. Data from several sensors may be highly correlated. Fusion techniques often employed Query-driven: network is interactive. Only sends data on demand Continuous-based: real-time data. Network is always sending data Time-driven: data is collected periodically from the environment Transmitted data may be loss-tolerant or not

6. Survey of Existing Routing Protocols Open Shortest Path First (OSPF) IBR BR IBR ABR IBR: Internal Border Router ABR: Area Border Router BR: Backbone Router ASBR: Autonomous System Border Router Link state information is only maintained within a single area Area 0 Area 1 Area 2 Area 3 Area 4 ASBR Internet Periodic messages are exchanged to maintain topology information at the routers New version OSPF v3 supports IPv6

7. Survey of Existing Routing Protocols Routing Information Protocol (RIP) Distance-vector routing protocol Each node maintains the state of the routers directly connected to it Nodes periodically transmit their tables to their neighbors Neighbors aggregate routing information in their tables

8. Survey of Existing Routing Protocols Ad-hoc On Demand Distance Vector (AODV) Routing Distance-vector routing protocol Hello messages broadcast neighbor information To discover route, RREQ message is broadcasted across the network RREQ has a sequence number. Nodes receiving duplicates discard them When the RREQ reaches the destination, or a node that knows the destination it sends a RREP RREP is unicast, not broadcast, back to the destination

9. Survey of Existing Routing Protocols ProtocolStateLossControlLink CostNode Cost OSPFFail PassFail OLSRFail??Pass RIPPassFailPass?Fail AODVPassFailPassFail DSRFailPass Fail Routing State - limited memory resources of low-power nodes. Loss Response - what happens in response to link failures. Control cost - constraints on control traffic. Link & Node cost - link and node properties are considered when choosing routes.

10. Directed Acyclic Graph (DAG) - a directed graph with no cycles exist. Destination Oriented DAG (DODAG) - a DAG rooted at a single destination. RPL: Routing for LLNs

11. RPL Instances Defines the position of the node in the DODAG Traffic in LLNs is typically one-to-many or many-to-one RPL instance builds a DODAG rooted at one node to optimize routing Each RPL instance optimizes a particular routing metric towards a node This metric may be a combination of several cost metrics Metrics may be link properties (reliability, delay, bandwidth, etc.) or node properties (remaining battery power, buffer capacity, etc.) Networks may run several concurrent instances, with an ID for each

12. RPL Control Messages RPL denes a new ICMPv6 message with three possible types: DAG Information Object (DIO) - carries information that allows a node to discover an RPL Instance, learn its configuration parameters and select DODAG parents DAG Information Solicitation (DIS) - solicit a DODAG Information Object from a RPL node Destination Advertisement Object (DAO) - used to propagate destination information upwards along the DODAG.

13. Route Construction Up routes towards nodes of decreasing rank (parents) Down routes towards nodes of increasing rank Nodes inform parents of their presence and reachability to descendants Source route for nodes that cannot maintain down routes Forwarding Rules All routes go upwards and/or downwards along a DODAG When going up, always forward to lower rank when possible, may forward to sibling if no lower rank exists When going down, forward based on down routes Nodes periodically send link-local multicast DIO messages Stability or detection of routing inconsistencies influence the rate of DIO messages Nodes listen for DIOs and use their information to join a new DODAG, or to maintain an existing DODAG Nodes may use a DIS message to solicit a DIO Based on information in the DIOs the node chooses parents that minimize path cost to the DODAG root Instance Creation and Routing

14. RPL Example Nodes only know information about their parents, not their children Nodes have a set of parent nodes Link failures does not trigger global network re-optimization

15. DODAG Repair Link between G and C fails  choose parent with lower rank Multicast DRQ message on all connected edges and wait for DRP message Handling of DRQ message – If Rank => Rank_DRQ Record reverse route, Forward DRQ to a parent – If Rank < Rank_DRQ Generate a DRP message, Forward DRP to DRQ transmitter Handling of DRP message – Decrease rank if necessary – Update Rank_DRP field of DRP – Forward DRP to next hop DODAG is locally repaired when a DRP message reaches DRQ message generator

16. Nodes inform parents of their presence and reachability to descendants by sending a DAO message Node capable of maintaining routing state  Aggregate routes Node incapable of maintaining routing state  attach a next-hop address to the reverse route stack contained within the DAO message Downward Destinations and Destination Advertisement

17. H sends a DAO message to F indication the availability of H, F adds the next-hop and forwards the message to I G sends a DAO message to F indication the availability of G, F adds the next-hop and forwards the message to I F sends a DAO message to I indication the availability of F I aggregates the routes and sends a DAO advertising (F-I) Downward Destinations and Destination Advertisement

18. Up towards the DAG root for many-to-one Down away from the DAG root for one-to-many Point-to-point via up*down* Traffic Flows