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Routing Routing in in wireless wireless networksnetworks
C. PhamUniversité de Pau et des Pays de l’AdourDépartement Informatiquehttp://www.univ-pau.fr/[email protected]
Routage 2Cours de C. Pham, Université de Pau et des Pays de l’Adour
Routing Routing in in wireless wireless networksnetworks
What’s a wireless network ?– Wireless terminals– Embedded– Mobility– With or without a fixed infrastructure– With or Without a centralized administration– Connected to the Internet or autonomous
Exemples– GSM– WiFi, WiMax– Bluetooth– Ad-Hoc, Manet– Wireless Sensor Networks– Vehicle network– …
Routage 3Cours de C. Pham, Université de Pau et des Pays de l’Adour
Ad-hoc Ad-hoc networksnetworks
Infrastructure-less networks MANET (Mobile Adhoc NETworks)
Routage 4Cours de C. Pham, Université de Pau et des Pays de l’Adour
Design Design choices choices (1)(1)
Single-hop or multi-hop ?
Single-path or multi-path?
Routage 5Cours de C. Pham, Université de Pau et des Pays de l’Adour
Design Design choices choices (2)(2)
Proactive?– Maintain & update routing table independently of communication
needs– Periodical updates– Same philosophy than in wired-networks (RIP, OSPF)– Low latency– « Waste » bandwidth and energy
Reactive, on-demand?– On-the-fly discovery of routes, when communication needs appear– Save bandwidth and energy– Higher latency– Generally efficient at low load
Hybrid?– Proactive or reactive depending on the distance
Routage 6Cours de C. Pham, Université de Pau et des Pays de l’Adour
Design Design choices choices (3)(3)
Flat routing?– Simple– Not scalable!
Hierarchical routing?– More efficient– « leaders » election overhead– Mobility cost– Multiple hierarchy levels are possible
Geographical routing?– GPS-aided for instance– Efficient routing towards the destinations– Geographical information are
propagated using flooding
Routage 7Cours de C. Pham, Université de Pau et des Pays de l’Adour
Structuration of Structuration of the the networknetwork
Desired properties– Hide topology changes (stability)– Structure the network (hierarchy)– Optimize information diffusion– Take into account the heterogeneity of nodes– Distributed
« backbone » approaches « clustering » approaches
Routage 8Cours de C. Pham, Université de Pau et des Pays de l’Adour
ClassificationClassification
Routage 9Cours de C. Pham, Université de Pau et des Pays de l’Adour
ExampleExample: AODV: AODV
Initiated when a communication need arises: reactive Source node initiates path discovery by broadcasting a
route request (RREQ) packet to its neighbors A neighbor either broadcasts the RREQ to its neighbors or
satisfies the RREQ by sending a RREP back to the source– Later copies of the same RREQ request are discarded
Node records the address of the sender of RREQ (indicatedin the RREQ)– Reverse path are automatically set-up– Entries are discarded after a time-out period
Eventually, a RREQ arrives at a node that possesses thecurrent route for the destination (Comparison of sequencenumbers)
The RREP travels along the path established in the reversepath set-up
Each node along the RREP journey sets up a forwardpointer, updates time-out entries, records the destinationsequence number of requested destination
AODV (Example)AODV (Example)
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RREQ
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ReversePath Setup
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ForwardPath Setup
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Routage 19Cours de C. Pham, Université de Pau et des Pays de l’Adour
ExampleExample: OLSR: OLSR
Proactive protocol, similar to Link State with HELLOpackets
Uses « multipoint relay » to reduce informationdiffusion costs– « multipoint relay » of node A are nodes N such that all 2-hop
neighbors of A are 1-hop neighbors of N.– Ex: C & E are multipoint relay of A
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Node with information from A
Routage 20Cours de C. Pham, Université de Pau et des Pays de l’Adour
OLSR (OLSR (concon’’tt))
Nodes C & E send information from A Nodes E & K are multipoint relays of H Node K send information from H
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Node with information from A
Routage 21Cours de C. Pham, Université de Pau et des Pays de l’Adour
Other protocolsOther protocols
Homework for next week– Find another proactive or reactive protocol (Internet search)– Understand it, explain it in front of class– Compare it to AODV and/or OLSR
