The document discusses several routing algorithms for mobile ad-hoc networks: TORA is a reactive protocol that reacts to changes and link reversals in highly dynamic networks; CGSR is a hierarchical and proactive protocol where routing tables are pre-built so paths are immediately available; flat routing table based protocols pre-build routing tables showing all paths while optimized link state protocols only update required routing data to reduce overhead.

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Mobile Ad-hoc and Sensor Networks
Lesson 05
Mobile Ad-hoc Network (MANET)
Routing Algorithms─ Part 2

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Temporally ordered routing
algorithm (TORA)
• A reactive protocol
• Reacts to the changes and link reversals
• Employed for highly dynamic MANETs
and provides an improved partial link
reversal process

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TORA
• Discovers the network portions showing
the link reversal(s)
• Has a feature that it stops the non-
productive link reversals in a given portion
of the network

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TORA
• Assumes addresses of the routers in the
path and of source and destination for one
set of input route
• Each node provides only one set of
subsequent route addresses

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TORA
• Possesses network capacity such that
many nodes can send packets to a given
destination
• Guarantees loop-free routes and supports
multicasting (from one source to multiple
destinations)

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TORA
• Unlike AODV, but similar to DSR, TORA
supports unidirectional links and also
provides multiple routing paths
• It does not exchange hello messages
periodically to listen to disconnected links
as done by AODV

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TORA
• Phases 1, 2, and 3 in TORA are route
creation, route maintenance, and
productive (useful) link reversal(s) (vector
discarding)

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Cluster-head gateway switch routing
(CGSR)
• A hierarchical routing protocol
• proactive protocol
• When a source routes the packets to
destination, the routing tables are already
available at the nodes
• A cluster higher in hierarchy sends the
packets to the cluster lower in hierarchy
• Each cluster can have several daughters
and forms a tree-like structure in CGSR

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CGSR
• Forms a cluster structure
• The nodes aggregate into clusters using
an appropriate algorithm
• The different clusters can be assigned to
different band of frequencies in FDMA or
different spreading CDMA codes

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CGSR algorithm
• Defines a cluster-head, the node used for
connection to other clusters
• Also defines a gateway node which
provides switching (communication)
between two or more cluster-heads

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Three types of nodes in CGSR
1. Internal nodes in a cluster which transmit
and receive the messages and packets
through a cluster-head

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Three types of nodes in CGSR
2. Cluster-head in each cluster such that
there is a cluster-head which dynamically
schedules the route paths. It controls a
group of ad-hoc hosts, monitors
broadcasting within the cluster, and
forwards the messages to another
cluster-head

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Three types of nodes in CGSR
3. Gateway node to carry out transmission
and reception of messages and packets
between cluster-heads of two clusters

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Cluster structure
• A higher performance of the routing
protocol as compared to other protocols
because it provides gateway switch-type
traffic redirections and clusters provide an
effective membership of nodes for
connectivity

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Phases 1, 2, and 3 of CGSR
• Routing path discovery and caching,
maintaining update, and distribution,
respectively
• The basic processes of CGSR are cluster
definitions and selection of clusters for
routing
• Algorithms are used for both the
processes

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Flat Routing Table Driven Protocol
• Routing cache table used earlier was a
routing table which builds by caching the
RERP and RERR packets
• Flat routing table driven protocol is a
proactive protocol
• This means that routing table will be
available in advance at a node

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Flat Routing Table Driven Protocol
• In the proactive protocol, the routing table
is available at each node shows available
routes from itself to target destination
node, is dynamically modified to show
available routes, and has rows for all
destined targets irrespective of whether
they will eventually be needed or not

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Flat Routing Table Driven Protocol
• The packet does not specify route in the
header and the routes need not be
discovered after the demand is raised

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Optimized Link State Routing
Protocol (OLSR)
• Characteristics similar to those of link state
flat routing table driven protocol, but in this
case, only required updates are sent to the
routing database
• Reduces the overhead control packet size
and numbers
• Further, there are multi-point nodes for
relay of data

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Optimized Link State Routing
Protocol (OLSR)
• A node selects independently a multi-point
node which also relays the route tables
• The node provides bi-directional links such
that the routes provided by the multi-point
relay routing neighbouring node is also
taken into account

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Summary
• TORA─ A reactive protocol, Reacts to
the changes and link reversals,
Employed for highly dynamic MANETs
and provides an improved partial link
reversal process
…

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…Summary
• CGSR ─A hierarchical routing protocol,
proactive protocol, When a source routes
the packets to destination, the routing
tables are already available at the nodes
…

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…Summary
• Flat Routing table based protocol
• Optimized Link State Reversal

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End of Lesson 05
Mobile Ad-hoc Network (MANET) Routing
Algorithms─ Part 2