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DYMO: Dynamic MANET On-Demand. 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 - PowerPoint PPT Presentation
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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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