Mobile Ad-hoc Networks (MANET) Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Mobile Ad-hoc Networks (MANET) Ad-hoc network: A collection of wireless mobile hosts forming a temporary network without the aid of any established infrastructure or centralized administration. Significant differences to existing wired networks: Wireless Self-starting No administrator Cannot assume that every computer is within communication range of every other computer Possibly quite dynamic topology of interconnections Traffic types: unicast/multicast/anycast/geocast Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Routing in MANET Routing assumptions for unicast traffic Flat topology assumption Proactive: DSDV, TORA, WRP Reactive: AODV, DSR, STAR Hierarchical topology assumption Clustering: CBRP, PATM Geographic assumption Location aided routing: LAR, GeoCast Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Classification of Routing Protocols for MANETS Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Classification of Routing Protocols for MANETS Unicast-Routing Protocol for MANET (Topology-based) Table-Driven/ Proactive Hybrid On-Demand /Reactive Clusterbased/ Hierarchical Distance Vector Link- State ZRP DSR AODV TORA LANMAR CEDAR DSDV OLSR TBRPF FSR STAR MANET: Mobile Ad hoc Network (IETF working group) Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Desired Properties of Ad Hoc Routing Protocols Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Desired Properties of Ad Hoc Routing Protocols Distributed Bandwidth efficient Reduce control traffic/overhead Battery efficient Fast route convergence Correct: loop free Reduce overhead Unidirectional Link Support Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Performance Metrics of Ad Hoc Routing Protocols Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Performance Metrics of Ad Hoc Routing Protocols Maximize end-to-end throughput delivery ratio Minimize Congestion (load-balancing) end-to-end delay packet loss shortest path/minimum hop (route length) overhead (bandwidth) energy consumption Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Mobile Ad hoc Networks (MANET) vs. Sensor Networks Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Mobile Ad hoc Networks (MANET) vs. Sensor Networks MANET SensorNet applications meeting, group collaboration smart building, habitat monitoring comm. address-centric comm. data centric comm. topology peer-to-peer sensors  base & peer-to-peer traffic random periodic, synchronous platform laptops, PDAs motes: more resource constrained scale 10’s to 100’s >1000: larger scale and more redundancy mobility slow (meeting) ~ fast (cars): focus on mobility slow (habitat) ~ fast: less focus on mobility so far similarity No infrastructure, multi-hop, wireless networks Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Address Centric Routing (AC) Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Address Centric Routing (AC) Temperature Reading (source 2) Temperature Reading (source 1) source 1 source 2 Z B Give Me The Average Temperature? ( sink ) Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Data Centric Routing (DC) Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Data Centric Routing (DC) Temperature Reading (source 2) Temperature Reading (source 1) source 1 source 2 source 1 & 2 Z B Give Me The Average Temperature? ( sink ) Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Dynamic Source Routing (DSR) [Johnson96] Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Dynamic Source Routing (DSR) [Johnson96] When node S wants to send a packet to node D, but does not know a route to D, node S initiates a route discovery using Route Request (RREQ) Each node appends own identifier when forwarding RREQ Promiscuous mode Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Route Discovery in DSR Y Z S E F B C M L J A G H D K I N Represents a node that has received RREQ for D from S Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Route Discovery in DSR Y Broadcast transmission Z [S] S E F B C M L J A G H D K I N Represents transmission of RREQ [X,Y] Represents list of identifiers appended to RREQ Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Route Discovery in DSR Y Z S [S,E] E F B C M L J A G [S,C] H D K I N Node H receives packet RREQ from two neighbors: potential for collision Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Route Discovery in DSR Y Z S E F B [S,E,F] C M L J A G H D K [S,C,G] I N Node C receives RREQ from G and H, but does not forward it again, because node C has already forwarded RREQ once Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Route Discovery in DSR Y Z S E F [S,E,F,J] B C M L J A G H D K I N [S,C,G,K] Nodes J and K both broadcast RREQ to node D Caveat: Since nodes J and K are hidden from each other, their transmissions may collide Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Route Discovery in DSR Broadcast storm prevention Drop previously seen messages Loop prevention Host drops messages with its address in route record (like BGP) Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Route Discovery in DSR Destination D on receiving the first RREQ, sends a Route Reply (RREP) RREP is sent on a route obtained by reversing the route appended to received RREQ Not always the case, sometimes need new route request RREP includes the route from S to D on which RREQ was received by node D Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Route Reply in DSR Y Z S RREP [S,E,F,J,D] E F B C M L J A G H D K I N Represents RREP control message Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Dynamic Source Routing (DSR) Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Dynamic Source Routing (DSR) Node S on receiving RREP, caches the route included in the RREP When node S sends a data packet to D, the entire route is included in the packet header hence the name source routing Intermediate nodes use the source route included in a packet to determine to whom a packet should be forwarded Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Data Delivery in DSR Y Z DATA [S,E,F,J,D] S E F B C M L J A G H D K I N Packet header size grows with route length Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Data Delivery in DSR Send route error packet if next hop cannot be reached Delete route from the cache when receiving error packet Passive acknowledgement: When node overhears next hop forwarding message. Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

DSR Optimization: Route Caching Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 DSR Optimization: Route Caching Each node caches a new route it learns by any means Through Route Request (RREQ) When node K receives RREQ [S,C,G] destined for node D, node K learns route [K,G,C,S] to node S Through Route Reply (RREP) When node S finds RREP [S,E,F,J,D] to node D, node S also learns route [S,E,F] to node F When node F forwards RREP [S,E,F,J,D], node F learns route [F,J,D] to node D Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

DSR Optimization: Route Caching Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 DSR Optimization: Route Caching Through DATA packet’s source routes When node E forwards Data [S,E,F,J,D] it learns route [E,F,J,D] to node D A node may also learn a route when it overhears Data Problem: Stale caches may increase overheads Splicing of cached routes Example: know [A,H,I] overheard [I,G,F] Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

DSR Optimization: Piggybacking Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 DSR Optimization: Piggybacking Possible to piggyback route reply on new route requests Also small data TCP handshake Host must forward piggybacked data when replying to request with cached routes Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

DSR Optimization: Error Handling Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 DSR Optimization: Error Handling Disconnected network leads to repeated route requests Addressed through exponential backoff Eavesdropping on route error packets Temporarily mark invalid route Other nodes may reply with invalid cached routes Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Dynamic Source Routing: Advantages Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Dynamic Source Routing: Advantages Routes maintained only between nodes who need to communicate reduces overhead of route table maintenance Routing cache can further reduce route discovery overhead A single route discovery may yield many routes to the destination, due to intermediate nodes replying from local caches Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Dynamic Source Routing: Disadvantages Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Dynamic Source Routing: Disadvantages Packet header size grows with route length due to source routing Flooding of route requests may potentially reach all nodes in the network Stale caches will lead to increased overhead Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Distance-Vector routing Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Distance-Vector routing Each node maintains a routing table containing Number of hops to each destination Next hop to reach each destination list of all destinations The succession of next hops leads to a destination Each node periodically broadcasts its current estimate of the shortest distance to each available destination to all of its neighbors Typical representative: Distributed Bellman-Ford (DBF) Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

AODV (Ad Hoc On-Demand Distance Vector) Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 AODV (Ad Hoc On-Demand Distance Vector) AODV is based on the DSDV (Destination-Sequenced Distance Vector) algorithm Distance vector Different sequence numbers for each destination. Creation of routes on a demand basis – traffic reactive Nodes that are not on a selected path do not maintain routing information or participate in routing table exchanges! Goal: Minimize broadcast overhead and transmission latency Here sequence numbers are used to supersede stale cached routes Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Route Sequence Numbers Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Route Sequence Numbers Unique counter for each destination Symbolizes the “freshness” of a route Source specifies the most recently known route during route establishment Updated occasionally Link failure Destination moves Intermediate nodes move Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Route Requests from S to D in AODV Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Route Requests from S to D in AODV Y Z S E F B C M L J A G H D K I N Represents a node that has received RREQ for D from S Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Route Requests from S to D in AODV Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Route Requests from S to D in AODV Y Broadcast transmission Z S E F B C M L J A G H D K I N Represents transmission of RREQ Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Route Requests from S to D in AODV Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Route Requests from S to D in AODV Y Z S E F B C M L J A G H D K Reverse Path is essentially a “breadcrumb” back to source node I N Represents links on Reverse Path Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Reverse Path Setup from S to D in AODV Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Reverse Path Setup from S to D in AODV Y Z S E F B C M L J A G H D K RREQ has global id = (source_id, broadcast_id) pair I N Node C receives RREQ from G and H, but does not forward it again, because node C has already forwarded RREQ once Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Reverse Path Setup from S to D in AODV Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Reverse Path Setup from S to D in AODV Y Z S E F B C M L J A G H D K I N Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Reverse Path Setup in AODV Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Reverse Path Setup in AODV Y Node D does not forward RREQ, because node D is the intended target of the RREQ Z S E F B C M L J A G H D K I N Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Route Reply from D to S in AODV Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Route Reply from D to S in AODV Y Z S E F B C M L J A G H D K Nodes that do not receive a Route Reply will timeout, and clear their route table for node D. I N Represents links on path taken by RREP Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Route Reply in AODV Intermediate node may also send a Route Reply (RREP) provided that it knows a more recent path than the one previously known to sender S Recent path means higher sequence number The likelihood that an intermediate node will send a RREP not as high as DSR An intermediate node which knows a route, but with a smaller sequence number, cannot send Route Reply Recent path means higher sequence number Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Forward Path Setup in AODV Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Forward Path Setup in AODV Y Z S E F B C M L J A G H D K I N Forward links are setup when RREP travels along the reverse path Represents a link on the forward path Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Data Delivery in AODV Routing table entries used to forward data packet. Route is not included in packet header. Y DATA Z S E F B C M L J A G H D K Mention timeouts I N Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Local Link Maintenance Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 Local Link Maintenance Periodic “hello” messages broadcast to immediate neighbors Failing to receive hello messages indicates a link failure Link failure notifications sent to source nodes Sources rediscover new route to destination Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 AODV Key Advantages “Partial” routing tables are constructed reactively Entries are updated only when a node sends to an unreachable node No periodic global updates Node not on active paths maintain no routing entries  Reduce packet overhead Routing table No source routing needed  reduce bit overhead “Route caching”  reduce establishment latency Sequence number  override stale routes source based broadcast id loop freedom Push link failure to relevant nodes  Reduce establishment latency Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller

AODV and DSR : Disadvantages Universität Karlsruhe Institut für Telematik Mobilkommunikation SS 1998 AODV and DSR : Disadvantages Common problems for both AODV and DSR Potential collisions between route requests propagated by neighboring nodes Insertion of random delays before forwarding RREQ Increased contention if too many route replies come back due to nodes replying using their local cache - Route Reply Storm problem Random delays + carrier sensing Wireless Networking Prof. Dr. Dr. h.c. G. Krüger E. Dorner / Dr. J. Schiller