DYMO: Dynamic MANET On-DYMO: Dynamic MANET On-DemandDemand IETF Draft submitted by

MANET WG Work in progress

Descendant of DSR and AODV A rewrite of AODV, using

different terminology and packet format, but having the same basic functionality

Table driven routing• Significantly smaller amount of

routing information than DSR Path accumulation (cf. DSR) is

optional No precursor list in routing table

entries Makes use of the generalized

MANET packet format Extensible through TLVs

Basic Internet connectivity AODV and DSR are not consider

Internet access DYMO maintains routing tables

with gateway and prefix information

DYMOcast Packet transmission to all

MANET routers within reception range

Broadcast in IPv4 or all node multicast in IPv6

Maintaining Local Connectivity may use any mechanisms Link layer feedback

• difficulty of obtaining IEEE 802.11 feedback in real networks

Hello messages• periodic one-hop L3 message• many ad hoc networks utilize

hello messages• depends on many factors such

as loss settings, message size, rate, ...

Neighbor discovery• relay highly on

broadcast/multicast capabilities of the underlying link layer

• need optimization Route timeout

• difficulty of determining the proper timeout because of dynamic mobility

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DYMO – Route DiscoveryDYMO – Route Discovery

Similar to the route discovery of the AODVDYMO uses only RE although AODV and

DSR use RREQ, RREPDYMOcast RE with A flag: Route RequestUnicast RE: Route Reply

RE packet format

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DYMO – Route discovery DYMO – Route discovery ComparisonComparison

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DSR AODV DYMO

Path way Bi-direction Optional bi-direction

Bi-direction

Seq. number X O O

Message type

RREQ, RREP RREQ, RREP RE

Message information

Path-accumulation

No path-accumulation

Optional path-accumulation

The other features

CachingMulti-path

Pre-cursor list Handling unsupportable message,Fixed control packet header

FloodingFlooding Advantages

Simplicity May be more efficient than

other protocols when rate of information transmission is low enough

Potentially higher reliability of data delivery

• Multiple path Disadvantages

Potentially, very high overhead

Potentially lower reliability of data delivery

• Flooding uses broadcasting -- hard to implement reliable broadcast delivery without significantly increasing overhead

– Broadcasting in IEEE 802.11 MAC is unreliable

nodes J and K may transmit to node D simultaneously, resulting in loss of the packet

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Flooding of Control PacketsFlooding of Control Packets

Used for route discoveryHow to reduce the scope of the route

request flood ?LARQuery localization

How to reduce redundant broadcasts ?The Broadcast Storm Problem

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Collision!

TORA: Temporally-Ordered Routing TORA: Temporally-Ordered Routing Algorithm [7-12]Algorithm [7-12] A source-initiated on-

demand routing protocol which use a link reversal algorithm

Provides loop-free multi-path routes to a destination node

Route establishment function is performed only when a source does not have any directed link Query/Update Height of node from the

destination

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TORA Route MaintenanceTORA Route Maintenance

When a partition is detected, all nodes in the partition are informed, and link reversals in that partition cease

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LAR: Location-Aided Routing [7-LAR: Location-Aided Routing [7-13]13] Utilizes the location

information (form GPS) to reduce the control packets overhead Flooding is restricted to a

small RequestZone

LAR1 algorithm

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LAR2 algorithm RREQ packet includes the

distance S between source and destination

When an intermediate node i receives RREQ, computed the distance DISTi to the destination

• If DISTi < S + δ, forward RREQ• Otherwise, discard

DREAM : Distance Routing Effect DREAM : Distance Routing Effect Algorithm for MobilityAlgorithm for Mobility

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ABR: Associativity-Based Routing ABR: Associativity-Based Routing [7-14][7-14] A beacon-based on-demand

routing protocol Selects routes based on the

stability of the wireless link Only links that have been

stable for some minimum duration are utilized

motivation: If a link has been stable beyond some minimum threshold, it is likely to be stable for a longer interval. If it has not been stable longer than the threshold, then it may soon break (could be a transient link)

Association stability determined for each link measures duration for which

the link has been stable Prefer paths with high

aggregate association stability

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SSA: Signal Stability Based SSA: Signal Stability Based Adaptive Routing [7-15]Adaptive Routing [7-15]Similar to DSRSignal strength is measure for determining

signal stabilityStrong/stable linkWeak/unstable link

A node X re-broadcasts a Route Request received from Y only if the (X,Y) link is deemed to have a strong signal stability

Signal stability is evaluated as a moving average of the signal strength of packets received on the link in recent past

An alternative approach would be to assign a cost as a function of signal stability

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Hybrid Routing ProtocolsHybrid Routing Protocols

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ZRP: Zone Routing Protocol [7-18]ZRP: Zone Routing Protocol [7-18] Routing zone of a given node: a subset of the

network, within which all nodes are reachable within less than or equal to zone radius hops

Intra-zone routing (IARP): employs proactive routing Inter-zone routing (IERP): uses reactive routing

Source S checks whether destination D is within its zone Source

• If D is within S’s zone, deliver the packet directly• Otherwise, bordercast the RREQ to its peripheral nodes

Peripheral nodes• If any peripheral node finds D to be its routing zone,

it sends RREP back to S• Otherwise, re-bordercast RREQ

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ZHLS: Zone-Based Hierachical Link ZHLS: Zone-Based Hierachical Link State Routing Protocol [7-19]State Routing Protocol [7-19] A hybrid routing protocol

Intra-zone routing:• Proactive routing• link state algorithm (SPF)

A hierarchical routing protocol Reactive routing Forms non-overlapping zones, using

the geographical location information of the nodes

Hierarchical address: (zone ID, node ID)

Zone-level connectivity • Zone LSP are propagated

by the gateway nodes

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Hierarchical Routing Hierarchical Routing ProtocolsProtocols

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HSR: Hierarchical State Routing HSR: Hierarchical State Routing [7-23][7-23] A distributed multi-level

hierarchical routing protocol

Employs clustering at different levels Clustering enhances

resource allocation and mgmt

• e.g) allocation of different frequency or spreading codes to different clusters

Physical clustering, logical clustering

Link state information is broadcast within the cluster at regular intervals

Cluster leader exchanges the topology and link state routing information with neighbor clusters

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FSR: Fisheye State Routing [7-23]FSR: Fisheye State Routing [7-23] To reduce information

to represent graphical data for reducing routing overheadKeep accurate

information about near nodes, but not-so-accurate information about far-away nodes

Hybrid approachLink-level information

exchange: use distance vector protocol

Network topology information : link state protocol

Frequency of exchange decreases with an increase in scope

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Power-Aware Routing Power-Aware Routing ProtocolsProtocols

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Power-Aware Routing MetricsPower-Aware Routing Metrics

Minimal energy consumption per packetMaximize network connectivityMinimum variance in node power levels

Distribute the load among all bodes

Minimum cost per packetRemaining battery charge cost factor for

routing

Minimize maximum node costMinimize the max cost per node for a packet

after routing a number of packets or after a specific period

This delays the failure of a node19

Power-Aware RoutingPower-Aware Routing [Singh98Mobicom,Chang00Infocom] Define optimization criteria as a function of energy

consumption. Examples: Minimize energy consumed per packet Minimize time to network partition due to energy depletion Maximize duration before a node fails due to energy depletion

Assign a weigh to each link Weight of a link may be a function of energy consumed

when transmitting a packet on that link, as well as the residual energy level low residual energy level may correspond to a high cost

Prefer a route with the smallest aggregate weight Possible modification to DSR to make it power aware (for

simplicity, assume no route caching): Route Requests aggregate the weights of all traversed links Destination responds with a Route Reply to a Route Request if

• it is the first RREQ with a given (“current”) sequence number, or• its weight is smaller than all other RREQs received with the current

sequence number

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