Doc.: IEEE 802.11-00/1047r0 Submission Month 2000August 2004 Avinash Joshi, Vann Hasty, Michael Bahr.Slide 1 Routing Protocols for MANET Avinash Joshi,

Month 2000August 2004

Avinash Joshi, Vann Hasty, Michael Bahr.Slide 1

doc.: IEEE 802.11-00/1047r0

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Routing Protocols for MANET

Avinash Joshi, Vann Hasty, MeshNetworks Inc.Michael Bahr, Siemens Corporate Technology



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Overview

• Introduction• Different Routing Protocols

– Reactive Routing Protocols– Proactive Routing Protocols– Hybrid Routing Protocols

• IETF MANET Group• Other Active work• 802.11s and MANET• Conclusion



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Introduction

Mobile Ad hoc Network (MANET)• Collection of wireless mobile nodes• Without using a pre-existing infrastructure• Routes between nodes may potentially

contain multiple hopsThis presentation• Considers only routing protocols discussed

in IETF MANET working group



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Typical Ad hoc Network

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TransmissionRange



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Different Routing Protocols

• Proactive Routing Protocols

• Reactive Routing Protocols

• Hybrid Routing Protocols



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Proactive Routing Protocols

• Main features:– Maintain routing information on all nodes in the network at all times.

This can be achieved by event driven routing information distribution and regular distribution of updated routing information.

• Advantages:– Lower route setup latency

• Disadvantages:– High routing overhead (periodic distribution of routing information)– Stale routing information in highly dynamic topologies.

• Protocol examples:– Optimized Link State Routing (OLSR)– Topology Dissemination Based on Reverse Path Forwarding (TBRPF)



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Reactive Routing Protocols

• Main features:– maintain routing information for the nodes which are needed and

only for the time when they are needed (Also called on-demand routing protocols.)

• Advantages:– Lower routing overhead

• Disadvantages:– Larger route set up latency– Route discovery packet flooding

• Protocol examples:– Dynamic Source Routing (DSR)– Ad hoc On-demand Distance Vector (AODV)



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Hybrid Routing Protocols

• Main features:– The routing is proactive for short distances and reactive for long

distances.• Advantages:

– Reduces impact of disadvantages of proactive and reactive routing protocols

– No route setup latency for short distance connections – Lower routing overhead due to reactive routing for further away

destinations• Disadvantages:

– More complex• Protocol examples:

– Zone Routing Protocol (ZRP)



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IETF MANET Working Group

Description:• To standardize IP routing protocol functionality suitable

for wireless routing application within both static and dynamic topoligies

• In the past, focused on exploring a broad range of MANET problems, performance issues, and related candidate protocols

• Promotion of a number of core routing protocol specifications to EXPERIMENTAL RFC status

• http://www.ietf.org/html.charters/manet-charter.html



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IETF MANET Working Group

Current Status:• Reached all milestones• 3 Experimental RFCs (AODV – RFC 3561, OLSR – RFC

3626, TBRPF – RFC 3684)• DSR submitted as Experimental RFC• Recharter in November

– decide on single reactive routing protocol and on single proactive routing protocol

– aspects of security and congestion control in the designed routing protocol/protocols.

• OSPF-MANET in OSPF working group



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Example of a Proactive Routing Protocol

• Optimized Link State Routing (OLSR)

• Experimental RFC 3626

• Authors: Thomas Clausen, Philippe Jacquet, et al, Project Hipercom, INRIA (France)



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OLSR

• Optimization of pure link state protocol– Reduced size of control packets (Only links to

multipoint relay selector nodes are advertised)– Minimized flooding (only multipoint relay

(MPR) nodes forward the packets)



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MPR Selection

Reference Node

One Hop Neighbors

Two Hop Neighbors



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MPR Selection

Selected MPRs



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MPR Selection

MPR can reach all the two hop neighborhood



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MPR Selection

MPR can reach all the two hop neighborhood



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OLSR Neighbor Sensing

• Periodic Hello messages detect the 2-hop neighborhood

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Multi Point Relay Selection

• MPR nodes are selected

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reference node1-hop neighborsMulti Point Relays2-hop neighbors



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Multi Point Relay Selection• Only Multi Point

Relays (MPRs) retransmit broadcast packets from their MPR selector

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Topology Info Dissemination• EVERY node MPR-

broadcasts its links between itself and neighbors that selected this node as MPR

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Topology Info Dissemination• EVERY node MPR-

broadcasts its links between itself and neighbors that selected this node as MPR

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Path Computation• iterative shortest path

algorithm using information from neighbor table and topology table

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Route Break

• compute new MPR set• broadcast TC message

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Route Break

• compute new MPR set• broadcast TC message• compute new path

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Example of a Reactive Routing Protocol

• Ad hoc On-Demand Distance Vector (AODV)

• Experimental RFC 3561

• Authors: Charles Perkins, Elizabeth Belding-Royer, Samir Das



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AODV

Main Functions

• Route Discovery

• Route Maintenance

• Uses Destination Sequence Number to avoid loops and “Counting to Infinity” problem



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AODV: Route Discovery

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A – Source

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‘A’ Broadcast a routerequest (RREQ) packet with Initial TTL =1

Broadcast RREQ



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Nodes receiving the RREQsets up Reverse Routes to the source

Broadcast RREQ

Reverse Route



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‘A’ times out and re-broadcast a Route Request (RREQ) packet with TTL = 2

Broadcast RREQ

Reverse Route



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Other Nodes Rebroadcasts the Route Request (RREQ) packet

Note: Nodes B, C and F receives RREQMultiple times but forward it only once



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‘A’ times out and re-broadcast a Route Request (RREQ) packet with TTL = 4

Broadcast RREQ

Reverse Route



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Route Request EventuallyReaches the Destination J

Broadcast RREQ

Reverse Route



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Destination send routeReply (RREP) back tosource using the reverseroute

RREP



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Node Receiving the RREPsets up a Forward Path tothe Destination

Route Reply

Forward Path



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Route Reply

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‘A’ now has a route to ‘J’



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A can now use the forward route created



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B – Source

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‘B’ Broadcast a routerequest (RREQ) packet



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‘A’ and ‘C’ replies

RREP

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‘B’ picks the minimum hop route (which is through C)



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AODV: Route Error

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AODV: Route Break

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Data is flowing between A and J



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AODV: Route Error

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LinkBreak

Link between E and J breaks due to

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AODV: Route Error

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All nodes maintain a precursor list of nodes who might use a link



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AODV: Route Error

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Route Error message is sent to the source



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AODV: Route Error

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LinkBreak

Route to J is removed and Route Discovery is reinitiated



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IRTF RRG Ad hoc Network Systems Research Subgroup

• Study of Ad hoc Network Systems (ANS)

• Inter-layer Protocol Interaction, Quality of Service Routing, Routing Scalability, Network Auto-Configuration, Interoperation with a wired infrastructure

• Currently not very active

• http://www.flarion.com/ans-research/



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Difference between IEEE 802.11s and IETF MANET

IETF MANET• Layer3

• Distributed Architecture

• Hop Based Metrics

• No QoS

• No Security Standard

• No Multicast Standard

• Mobility?

• Up to Large Scale

802.11s• Layer 2

• Presence of Gateways

• LQ/Hop Based Metrics

• QoS

• Security

• Multicast

• Mobility?

• Reduced Scale



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Current Research

• Link Quality (MIT)

• Integration of MANETs into existing Internet (several Internet drafts, EU project “Daidalos”)

• Security

• Energy-awareness



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Conclusion

• Many general insights into routing/path finding

• Many concepts available, each with its advantages and disadvantages

• Concepts and experiences from MANETs can be used for TGs



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References

• Ad Hoc Networking by Charles E. Perkins • http://moment.cs.ucsb.edu/AODV/aodv.html

• http://hipercom.inria.fr/olsr/

• http://w3.antd.nist.gov/wctg/manet/manet_bibliog.html

• Google

Documents

Doc.: IEEE 802.11-00/1047r0 Submission Month 2000August 2004 Avinash Joshi, Vann Hasty, Michael Bahr.Slide 1 Routing Protocols for MANET Avinash Joshi,