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DTCAST: Delay Tolerant Multicast Routing On-Demand Hybrid Multicast Routing Guaranteed Data Delivery Short-Term Disconnection Tolerance Long-Term Disconnection Tolerance Zhenkai Zhu ([email protected]) Keith Mayaral ([email protected]) Alexander Afanasyev ([email protected]) Tutors: Soon Oh ([email protected]) Uichin Lee ([email protected]) UCLA Computer Science Department 1 Applications Broadcast nature of wireless should be exploited for multicast data delivery Mobile ad hoc networks with intermittent connectivity Critical information dissemination in emergency situations Ad hoc networks experienced short-term and long-term disconnectivity periods UCLA Computer Science Department 2 Assumptions All nodes are trusted Source knows list of destinations whom it should deliver data Destinations know multicast address of the dissemination data Data messages have long actuality period (e.g. from 1 hour to 1 day) Data rate is small (1-16 KiBytes/s) UCLA Computer Science Department 3 DTCAST relation to other protocols User Application Messaging Service … Message Payload DTCAST Transport Layer (Optional) IPv4 Data Link Layer 802.11 (LNK) Physical Layer 802.11 (PHY) Physical Medium UCLA Computer Science Department 4 DTCAST Features On-Demand Hybrid Multicast Routing and Data Delivery Multicast Group Based Routing Source Learning (RQ) Responsibility List Learning Delay and Disruption Tolerance Guaranteed delivery – Implicit / Explicit Acks Robustness to network topology changes Local recovery – Route Injection Epidemic recovery – Data Run After Nodes UCLA Computer Science Department 5 DTCAST: On-Demand Hybrid Multicast Routing Based on RouteRequest / RouteReply ODMRP scheme Includes Local Recovery of the E-ODMRP Each node learns for which the destinations it is on the path – responsibility list learning Adds forward path learning for explicit (passive) data acknowledgement Common features: ◦ ◦ ◦ ◦ Source path learning Underlaying protocol independence Soft states – forwarding tables pruned on timeout Shortest (fastest) path maintaining using Route Request caching or TTL field ◦ Robustness to node disconnections UCLA Computer Science Department 6 ODMRP: Routing Phase Forwarding Group S R F F F R Join Query Join Reply Forwarding Node Link Multicast Route F R R On-demand approach: A source initiates JOIN QUERY flooding only when it has data to send Using JOIN QUERY intermediate nodes set up route to sender (source path learning) Members send Join Reply messages using via source path Routes from sources to receivers build a mesh of nodes called “forwarding group”. UCLA Computer Science Department 7 DTCAST: Routing Phase On-Demanding: Flooding Route Request only if there is data to send Source path learning Destinations respond with Route Reply Forward path learning All nodes are virtually sources – real or temporary) Request Reply Request Reply Request Reply From=5 Mcast=X Dst=8 From=8 Mcast=X Dst=8 From=3 Mcast=X Dst=6,8 From=1 Mcast=X UCLA Computer Science Department 8 DTCAST: Routing Phase (cont.) Routing Tables Source Routing Table Source Node ID Next Node ID to Source <XX> <YY> <XX> SELF … … Responsibility List (Forwarding Table) DST ID FW_FLAG Source Node ID Multicast ID <A> TRUE <XX> <YY> <B> FALSE … … … … UCLA Computer Science Department 9 DTCAST: Routing Phase (cont.) Route Request and Route Reply Packets IP header DTCAST header Only NEXT ID node should process Reply packet For responsibility list learning UCLA Computer Science Department 10 DTCAST Features On-Demand Hybrid Multicast Routing and Data Delivery Multicast Group Based Routing Source Learning (RQ) Responsibility List Learning Delay and Disruption Tolerance Guaranteed delivery – Implicit / Explicit Acks Robustness to network topology changes Local recovery – Route Injection Epidemic recovery – Data Run After Nodes UCLA Computer Science Department 11 DTCAST:Delay tolerated guaranteed data delivery to multicast group nodes Each DTCAST data message has period of actuality (1 hour, 1 day, …) Each data message associated with multicast group ID and list of destinations On receiving data message, each node on forwarding path saves message in local queue and sends implicit or explicit ACK, containing list of the destinations node responsible for On receiving ACKs, node subtractsdestination list in queued packed and destinations list in ACK Message is deleted from local queue iff destination list in queued packed is empty UCLA Computer Science Department 12 DTCAST: Data Transfer Phase Full connectivity Node 4 queue MSG 1 •6 DATA SEQ: 1 DATA SEQ: 1 DATA SEQ: 1 Node 1 queue MSG 1 •6 •8 Node 3 queue MSG 1 •6 •8 Node 5 queue MSG 1 •8 Acknowledgement Message (Implicit or Explicit) UCLA Computer Science Department 13 DTCAST: Data Transfer Phase (cont.) Data and Acknowledgment Packet IP header DTCAST header Timestamp till which network would try to deliver data message To subtract IDs from responsibility list UCLA Computer Science Department 14 DTCAST Features On-Demand Hybrid Multicast Routing and Data Delivery Multicast Group Based Routing Source Learning (RQ) Responsibility List Learning Delay and Disruption Tolerance Guaranteed delivery – Implicit / Explicit Acks Robustness to network topology changes Local recovery – Route Injection Epidemic recovery – Data Run After Nodes UCLA Computer Science Department 15 DTCAST: Robustness to network topology changes Node mobility (new set of neighbors) New path discovery through RQ/RR after timeout Local path recovery – destination locally floods RouteReply packet with NextNode=All field Short-term disconnection (e.g. signal interference) Epidemic flooding if node disappeared from forwarding path Data rebroadcasting after timeout until ACK received Long-term disconnection (e.g. power failure) Continue delivery tries until message time actuality (TA) exceeded Message will not be deleted from source or intermediate node queues until it was delivered or TA exceeded UCLA Computer Science Department 16 DTCAST: Local Path Recovery Route Injection. Fast receiver mobility routing Triggering heuristics: timeout after last data message. Top process after second timeout In local path recovery node floods one-hop neighbors with RouteInject packets – force all neighbors to establish forwarding route if they have source path If data is available, it can be forwarded multiple times until route prune timeout 6 6 Route Inject packet UCLA Computer Science Department 17 DTCAST: Epidemic Flooding Fast node mobility. Data message runs after node 8 8 Triggering heuristics: if forwarding path exists and no ACK for two retransmission Set ER flag and flood data in two-hop range If node receive data with ER and it has forwarding path – it fourhop floods ACK with ER flag If no ACK before timeout, intermediate node become source for data packet -Route Request/Reply scheme until time of actuality reached Route will be rebuild after route prune timeout (RQ/RR) UCLA Computer Science Department 18 Implementation using Click Broadcast Medium Source Data Multiplexer Route Request Initiator Data Queue Epidemic Data Run Initiator Source Routing Table Forwarding List Table Broadcast Medium Data Demultiplexer Route Reply Generator Route Injection Generator UCLA Computer Science Department 19 Experimental Testbed Scheme Connectivity Node 1: Test Data Generation Node 5,7,6: Multicast Test Data Receivers Data transfer Data message size 1024 bytes Continuous data transfer 1 min Message actuality 20 min Node 3: Non-critical path forwarder Node 4: Critical path forwarder UCLA Computer Science Department 20 Performance Evaluation (TODO) Ratio of the received data using different generation speed Recovery delay after node connection lost/recovery for different disconnection periods Recovery delay (network stress period) if disconnected node is on non-critial and critical path UCLA Computer Science Department 21 Conclusion ODMRP-comparable performance in the case of full-connectivity Fast recovery from topology disruptions ◦ Short term disconnectivity ◦ Long term disconnectivity ◦ Node mobility Transport layer guarantee for data delivery within message period of actuality UCLA Computer Science Department 22