Lecture (11-14) ---

On-Demand-Driven

Reactive Routing protocols Chandra Prakash

Assistant Professor

LPU

Ad Hoc Routing Protocol Routing protocols category :

(a) Table-driven,

(b) Source-initiated on-demand-driven.

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3

Overview of Current Routing

Protocols

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Table-driven vs. On-demand

Table-Driven Routing Protocol:

proactive

continuously evaluate the routes

attempt to maintain consistent, up-to-date routing information

when a route is needed, one may be ready immediately

when the network topology changes

the protocol responds by propagating updates throughout the network to

maintain a consistent view

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Table-driven vs. On-demand (cont.)

Source-Initiated On-Demand Routing Protocol: Reactive on-demand style: create routes only when it is desired by the source

node route discovery: invoke a route-determination procedure, the procedure is

terminated when a route has been found

no route is found after all route permutations are examined

route maintained by a route maintenance procedure until inaccessible along every path from the source

no longer desired

longer delay: sometimes a route may not be ready for use immediately when data packets come

On-Demand Driven/ Reactive protocols

In a reactive protocol, a route is discovered only when it is

necessary.

In other words, the protocol tries to discover a route only on-

demand, when it is necessary.

These protocols generate much less control traffic at the cost of

latency, but it usually takes more time to find a route

compared to a proactive protocol.

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Source-Initiated On-Demand Approaches

Creates routes only when desired by the source node.

finds a route on demand by flooding the network with Route Request packets.

When a node requires a route to a destination, it initiates a route discovery process within the network.

Completed when either a route is found or all possible route permutations have been examined.

Once a route has been discovered and established, it is maintained by some form of route maintenance procedure until either the destination becomes inaccessible along every path from the source or the route is no longer desired.

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Source-initiated on-demand

1. Dynamic Source Routing (DSR) D. B. Johnson and D. A. Maltz, “Dynamic Source Routing in Ad-Hoc Wireless Networks,”

Mobile Computing, T. Imielinski and H. Korth, Eds., Kluwer, 1996, pp. 153–81.

2. Ad-Hoc on-demand distance vector routing (AODV) C. E. Perkins and E. M. Royer, “Ad-hoc On-Demand Distance Vector Routing,” Proc. 2nd

IEEE Wksp. Mobile Comp. Sys. and Apps., Feb. 1999, pp. 90–100.

3. Temporally ordered routing algorithm (TORA) V. D. Park and M. S. Corson, “A Highly Adaptive Distributed Routing Algorithm for

Mobile Wireless Networks,” Proc. INFOCOM ’97, Apr. 1997.

4. Associativity-Based routing (ABR) C-K. Toh, “A Novel Distributed Routing Protocol To Support Ad-Hoc Mobile Computing,”

Proc. 1996 IEEE 15th Annual Int’l. Phoenix Conf. Comp. and Commun., Mar. 1996, pp. 480–86.

5. Signal stability routing (SSR) R. Dube et al., “Signal Stability based Adaptive Routing (SSA) for Ad-Hoc Mobile

Networks,” IEEE Pers. Commun., Feb. 1997, pp. 36–45.

1. Dynamic Source Routing (DSR)

D. B. Johnson and D. A. Maltz, “Dynamic Source Routing in Ad-Hoc Wireless Networks,”

Mobile Computing, T. Imielinski and H. Korth, Eds., Kluwer, 1996, pp. 153–81.

On-demand routing protocol

based on the concept of source routing

Designed to restrict the bandwidth consumed by control packets in table

driven approach

Eliminated the periodic table-update message (hello packet/

beacon)

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Dynamic Source Routing (DSR)

Each host maintains a route cache which contains all routes it

has learnt.

Source Routing:

routes are denoted with complete information (each hop is

registered)

Two major parts:

route discovery

route maintenance

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Dynamic Source Routing (DSR) When a host has a packet to send, it first consults its route cache. If there is an unexpired route, then it will use it. Otherwise, a route discovery will be performed

Route Discovery: Initiates by broadcasting a route request packet.

Source node S floods Route Request (RREQ)

Route request message contains

Address of the destination,

Source node's address and

Unique identification number.

Each node appends own identifier(Sequence number) when forwarding RREQ Entries in the

route cache are continually updated as new routes are learned.

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Dynamic Source Routing (DSR) There is a “route record” field in the packet. The source node will add its address to the record. On receipt of the packet, a host will add its address to the “route

record” and rebroadcast the packet.

Each node receiving the packet checks whether it knows of a route to the destination.

If it does not, it adds its own address to the route record of the packet and then forwards the packet along its outgoing links.

To limit the number of ROUTE_REQUEST packets: Each node only rebroadcasts the packet at most once. Each node will consult its route cache to see if a route is already

known.

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Route Discovery in DSR

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S E

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J

D

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Represents a node that has received RREQ for D from S

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Route Discovery in DSR

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S E

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J

D

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K

Represents transmission of RREQ

Z

YBroadcast transmission

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[S]

[X,Y] Represents list of identifiers appended to RREQ14

Route Discovery in DSR

B

A

S E

F

H

J

D

C

G

I

K

• Node H receives packet RREQ from two neighbors:

potential for collision

Z

Y

M

N

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[S,E]

[S,C]

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Route Discovery in DSR

B

A

S E

F

H

J

D

C

G

I

K

• Node C receives RREQ from G and H, but does not forward it again,

because node C has already forwarded RREQ once

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Y

M

N

L

[S,C,G]

[S,E,F]

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Route Discovery in DSR

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B

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S E

F

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J

D

C

G

I

K

Z

Y

M

• Nodes J and K both broadcast RREQ to node D

• Since nodes J and K are hidden from each other, their transmissions

may collide

N

L

[S,C,G,K]

[S,E,F,J]

Route Discovery in DSR

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B

A

S E

F

H

J

D

C

G

I

K

Z

Y

• Node D does not forward RREQ, because node D

is the intended target of the route discovery

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N

L

[S,E,F,J,M]

Route Discovery in DSR A ROUTE_REPLY packet is generated when the route request packet reaches the destination an intermediate host has an unexpired route to the destination

Destination D on receiving the first RREQ, sends a Route

Reply (RREP)

RREP is sent on a route obtained by reversing the route

appended to received RREQ

RREP includes the route from S to D on which RREQ was

received by node D

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Route Reply in DSR

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RREP [S,E,F,J,D]

Represents RREP control message

Dynamic Source Routing The ROUTE_REPLY packet will contain a route generated in

following manner: Use the route of destination route cache (if route cache has the route

information) the route that was traversed by the ROUTE_REQUEST packet (if

symmetric) route discovery and piggyback the route reply on the new request (if

asymmetric)

Node S on receiving RREP, caches the route included in the RREP

Source routing

When node S sends a data packet to D, the entire route is included in

the packet header

Intermediate nodes use the source route included in a packet to

determine to whom a packet should be forwarded21

Data Delivery in DSR

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DATA [S,E,F,J,D]

Packet header size grows with route length

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Dynamic Source Routing (DSR)

Routing discovery routing reply

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Dynamic Source Routing (DSR) Routing maintenance

Use acknowledgements or a layer-2 scheme to detect broken links.

Inform sender via route error packet.

Initiate route discovery.

All routes which contain the breakage hop have to be removed from

the route cache.

Route Error packet

destination

source1

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4

3

2

8

7

(1,4)

(1,2)

(1,3)

(1,3,5,6)(1,3,5)

(1,4,7)

source broadcasts a packet containing address of source and destination

The route looks up its route caches to look for a route to destination

If not find, appends its address into the packet

The destination sends a reply packet to source.

The node discards the packets having been seen

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DSR OverviewAdvantages Designed to restrict the bandwidth consumed by control packets in table driven approach

Eliminated the periodic table-update message (hello packet/ beacon)

Routes maintained only between nodes who need to communicate (on demand )thus

reduces overhead of route maintenance

Route caching can further reduce route discovery overhead

A single route discovery may yield many routes to the destination, due to intermediate nodes

replying from local caches

Disadvantage Packet header size grows with route length due to source routing degrade

performance- when data contents of a packet are small

Flood of route requests may potentially reach all nodes in the network

Potential collisions between route requests propagated by neighboring nodes

Increased contention if too many route replies come back due to nodes replying using their

local cache

Route Reply Storm problem26

2. Ad Hoc On-Demand Distance Vector

Routing Protocol (AODV)

C. E. Perkins and E. M. Royer, “Ad-hoc On-Demand Distance Vector Routing,” Proc. 2nd IEEE Wksp. Mobile Comp. Sys. and Apps., Feb. 1999, pp. 90–100.

DSR includes source routes in packet headers, resulting large headers.

AODV attempts to improve on DSR

by maintaining routing tables at the nodes, so that data packets do not have to contain routes,

In AODV, the source node and the intermediate nodes store the next hop information corresponding to each flow data packet transmission.

AODV relies on dynamically establishing route table entries at intermediate node.

AODV retains the desirable feature of DSR that routes are maintained only between nodes which need to communicate

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Ad Hoc On-Demand Distance

Vector Routing Protocol

AODV is an improvement on DSDV

minimizes the number of required broadcasts

by creating routes on an on-demand basis

AODV use the concept of destination sequence number from DSDV to determine an

up-to-date path to the destination.

It is a pure on-demand route acquisition system

AODV only supports the use of symmetric links.

Nodes which are not on a selected path do not maintain routing information or

participate in routing table exchanges.

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AODV Includes

Route discovery

Route maintenance.

Path discovery procedure using RREQ/RREP query cycles. Reverse Path setup

Forward path setup

Route table management AODV maintains routes as long as they are active.

Path maintenanceThe source moves: reinitiate the route discovery

Other node moves: a special RREP is sent to the affected source nodes

Local connectivity management Broadcasts used to update local connectivity information

Inactive nodes in an active path required to send “hello” messages

Route Requests in AODV

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B

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S E

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J

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I

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Z

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Represents a node that has received RREQ for D from S

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AODV Route Requests (RREQ) are forwarded in a manner similar to DSR

Route request message contains

Source identifier (SrcID)

Destination identifier (DestID)

Source sequence number (SrcSeqNum)

Destination sequence number (DestSeqNum)

Broadcast identifier (BcastID) and Time to live(TTL) field

When a node re-broadcasts a Route Request, it sets up a reverse path pointing towards the source

AODV assumes symmetric (bi-directional) links

When the intended destination receives a Route Request, it replies by sending a Route Reply (RREP)

Route Reply travels along the reverse path set-up when Route Request is forwarded31

Route Requests in AODV

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B

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J

D

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I

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Represents transmission of RREQ

Z

YBroadcast transmission

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Route Requests in AODV

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B

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D

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I

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Represents links on Reverse Path

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Y

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Reverse Path Setup in AODV

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B

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J

D

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I

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• Node C receives RREQ from G and H, but does not forward

it again, because node C has already forwarded RREQ once

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Y

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Reverse Path Setup in AODV

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Reverse Path Setup in AODV

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B

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J

D

C

G

I

K

Z

Y

• Node D does not forward RREQ, because node D

is the intended target of the RREQ

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N

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Forward Path Setup in AODV

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B

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Forward links are setup when RREP travels along

the reverse path

Represents a link on the forward path

Ad Hoc On-Demand Distance Vector Routing

(AODV)

AODV uses destination sequence numbers to ensure that all routes are loop-free and contain the most recent route information.

Each node maintains its own sequence number, as well as a broadcast ID.

The broadcast ID is incremented for every RREQ the node initiates, and together with the node's IP address, uniquely identifies an RREQ.

Source node includes in the RREQ the most recent sequence number it has for the destination.

Intermediate nodes can reply to the RREQ only if they have a route to the destination whose corresponding destination sequence number is greater than or equal to that contained in the RREQ.

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Ad Hoc On-Demand Distance Vector Routing

(AODV) At the time of forwarding the RREQ, intermediate nodes record the

address of neighbors from which the first copy of broadcast packetwas received, in their route tables, to establishing a reverse path.

Once the RREQ has reached the destination,

It responds by unicasting a route reply (RREP) packet back to the neighbor fromwhich it first received the RREQ and so on.

As the RREP is routed back along the reverse path, nodes along this path set upforward route entries in their route tables that point to the node from whichthe RREP came.

A route timer is associated with each route entry, which causes the deletion ofthe entry if it is not used within a specified lifetime.

Because an RREP is forwarded along the path established by an RREQ, AODVonly supports the use of symmetric links.

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Route Request and Route Reply Route Request (RREQ) includes the last known sequence number for

the destination

An intermediate node may also send a Route Reply (RREP)

provided that it knows a more recent path than the one

previously known to sender

Intermediate nodes that forward the RREP, also record the next hop to

destination

A routing table entry maintaining a reverse path is purged after a

timeout interval

A routing table entry maintaining a forward path is purged if not used for

a active_route_timeout interval

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Ad Hoc On-Demand Distance Vector Routing

(AODV)

Consideration for other better routes is absent in AODV.

This approached was first proposed in Associativity Based Routing (ABR) in 1994 and

protected by the ABR US patent.

In AODV, routes are maintained as follows:

If a source node moves, it reinitiate the route discovery protocol to find a new route.

If a node along the route moves, its upstream neighbor notices the move and

propagates a link failure notification message (an RREP with an infinite metric) to

each of its active upstream neighbors to inform them of the erasure of that part of the

route.

These nodes in turn propagate the link failure notification to their upstream

neighbors, and so on, until the source node is reached.

The source node may then choose to re-initiate route discovery for that destination if

a route is still desired.41

AODV: Summary

Advantages The authors claim scalability up to 10,000 nodes (performance suffers, simulation

results)

Routes are established on demand

Routes need not be included in packet headers

Nodes maintain routing tables containing entries only for routes that are in active use

Destination sequence no are used to find the latest route to the destination

Sequence numbers are used to avoid old/broken routes and formation of routing loops

Connection setup is less

Disadvantage Intermediate nodes can lead to inconsistent routes if the source

sequence no is very old and the intermediate node have a higher but

not the latest destination sequenced no.

Periodic beaconing leads to unnecessary bandwidth consumption.42

3. Temporally Ordered Routing

Algorithm (TORA)V. D. Park and M. S. Corson, “A Highly Adaptive Distributed Routing Algorithm for Mobile

Wireless Networks,” Proc. INFOCOM ’97, Apr. 1997.

TORA is proposed to operate in a highly dynamic mobile networking

environment.

Highly adaptive, loop-free, distributed routing algorithm based on the

concept of link reversal.

Key design concept ofTORA

localization of control messages to a very small set of nodes near the occurrence of a

topological change.

To accomplish this, nodes need to maintain routing information about adjacent (one-

hop) nodes.

The height metric is used to model the routing state of the network.

The protocol performs three basic functions:

(a) route creation, (b) route maintenance, and (c) route erasure.

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TORA: Temporally ordered routing During the route creation and maintenance phase, nodes establish a

directed acyclic graph(DAG).

A logical direction is imposed on the links towards the destination

Source-initiated and provides multiple routes for any desired source/destination pair.

Starting from any node in the graph, a destination can be reached by following the directed links

Highly adaptive, efficient, scalable, distributed algorithm

Multiple routes from source to destination

For highly dynamic mobile, multi-hop wireless network

A

C

E

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F

G

B

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TORA Assigns a reference level (height) to each node

A DAG is maintained for each destination

Synchronized clock is important, accomplished via GPS or algorithm such as Network Time Protocol.

Timing is an important factor for TORA because the “height” metric is dependent on the logical time of a link failure. metric: logical time of a link failure The unique ID of the node that defined the new reference level A reflection indicator bit A propagation ordering parameter The unique ID of the node

Adjust reference level to restore routes on link failure

Query, Update, Clear packets used for creating, maintaining and erasing routes

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TORA Three major tasks Route creation: QRY and UPD packets

Route maintenance

Route erasure: Clear packet (CLR) is broadcasted

Using Unique node ID and unique reference ID

Route Creation: demand driven “query/reply” Performed only when a node requires a path to a destination but does not have nay

directed link.

A query packet (QRY) is flooded through network

An update packet (UPD) propagates back if routes exist

Route Maintenance: “link-reversal” algorithm React only when necessary

Reaction to link failure is localized in scope

Route Erasure: A clear packet (CLR) is flooded through network to erase invalid routes

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TORA

Route creation of TORA

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1

2

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s s

d d

Propogation of QRY

(reference level, height)

Height of each node

updated by UPD

Route Creation in TORA

(-,-)

(-,-)

(-,-)

(-,-)

(-,-)

(-,-)

(0,0)

(-,-)

(0,3) (0,3)

(0,3)

(0,2)

(0,1)

(0,0)

(0,1)(0,2)

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TORA

Creation of route

C

A B

E

G (DEST)

FH

D

QRY

QRY

QRYUPD

QRY

QRY

UPD

UPD

UP

D

UPD UPD

UPD

a

fe

d

c

b

h

g

(-,-,-,-,d)

(-,-,-,-,b)

(-,-,-,-,c)

(-,-,-,-,f)(-,,-,-,-e)

Only the non-NULL node (destination) responds with a UPD packet.

(0,0,0,0,h)

(-,-,-,-,a)

The source broadcasts a QRY packet with height(D)=0, all others NULL

(0,0,0,4,b)

(0,0,0,4,c)

(0,0,0,3,e)(0,0,0,2,f)

(0,0,0,2,d)(0,0,0,3,a)

source

Dest.

A node receiving a UPD sets its height to one more than UPD

Source receives a UPD with less height

UPD

QRY

QRYQRY

(-,-,-,-,g)(0,0,0,1,g)

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QRY

QRY

QRY

QRY

QRY

QRY

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TORA

Route maintenance

C

A B

E

G (DEST)

FH

D

UPD

X

UPD

UPD

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TORA

TORA: Summary

Advantages Less control overload: by limiting the control packets for route reconfiguration

to a small region

Disadvantage The local reconfiguration of paths results in non-optimal routes

Concurrent deduction of partitions and subsequent deletion of routes could result

in temporary oscillations and transient loops.

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4. ABR: Associativity-Based routing C-K. Toh, “A Novel Distributed Routing Protocol To Support Ad-Hoc Mobile Computing,” Proc. 1996

IEEE 15th Annual Int’l. Phoenix Conf. Comp. and Commun., Mar. 1996, pp. 480–86.

First routing protocol that advocates the selection of stable links and routes for

ad hoc wireless networks.

Goal: Best route is selected based on stability and shortest path of wireless

link .

Associativity is related to the spatial, temporal, and connection stability of a mobile host

(MH).

The stability is measured using associativity ticks(initially set to zero)

Each node broadcasts beacons, the nodes increment associativity ticks when they receive beacons and sets zero if beacon is not received. High Associativity means high stability.

A node's association with its neighbors changes as it is migrating, and its transition period

can be identified by associativity ticks or counts.

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Associativity-Based routing Selects route based on the stability for the wireless links.

Beacon-based, on demand routing protocol

Link is classified as stable or unstable based on its temporal stability

Temporal stability is determined by counting the periodic beacons that a node

receive from its neighbors.

Each node maintains the count of its neighbors’ beacons and on the basis of

beacon count corresponding to the neighbor node concerned. classifies each

link as

stable link : link corresponding to a stable neighbor

unstable : link to an unstable neighbor

A source node floods RouteRequest packets in the network if a route is not

available in its route cache.

All intermediate node forward the RouteRequest packets.54

Associativity-Based routing RouteRequest packet carries the path it has traversed and the beacon

count for the corresponding nodes in the path.

When the first RouteRequest reaches the destination , the destination waits for

a period TrouteselceteTime to receive multiple RouteRequest through different

paths.

After this time , destination selects the path that has the max. no of

stable links.

If two paths have same proportion of stable links, shortest path is selected.

If more than one shortest path available, random path is selected.

ABR doesn't restrict any intermediate node from forwarding a RouteRequest

packet based on the stable or unstable link criterion.

It uses stability information only during the route selection process at the

destination node.

ABR give more priority to stable routes than to shorter routes.

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Associativity-Based routing

Source Initiated Routing, Query-Reply packets

Route is long-lived and free from loops, deadlock, and packet duplicates

ABR provides the method of reconstructing when link fails

The protocol contains 3 phases:

Route discovery: BQ-REPLY cycle

Route reconstruction (RRC):

Route deletion (RD): Source-initiated

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ABR

Route discovery: accomplished by a broadcast query and await-reply(BQ-REPLY) cycle.

A node desiring a route broadcasts a BQ message . In search of mobiles a route broadcasts a BQ(Broadcast query) message in search of mobiles that have a route to the destination

All nodes receiving the BQ append their address and their associativity ticks with their neighbors along with QoS information to query packet.

A successor node erases its upstream node neighbor’s associativity ticks entries and retains only the entry concerned with itself and its upstream node.

The destination computes the total of the associativity ticks The destination will know all the possible routes and their qualities. It then selects the

best route based on stability and associativity ticks.

If multiple paths have the same overall degree of association stability, the route with minimum number of hops is selected.

Temporal and spatial representation of associativity of a

mobile node with its neighbors.

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Rule and Property of Associativity

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Scenario:

cell size d = 10m

MH min migration speed v = 2m/s

Beacon transmission interval p = 1s

Athreshold = 2 r /(vp) = 5

Association stability results when no. of beacons recorded is >

Athreshold

Low associativity ticks high state of mobility

High associativity ticks stable state

Stability is also determined by signal strength and power life.

ABR Stability in ABR refers to more than just associativity ticks. It also

includes

signal strength:defines the quality of the signal propagation channel

power life:describes the current power life of the device

Advances in radio transceiver technology has enabled one to monitor

signal strength over time and store this information into memory.

Advances in smart battery technology has enabled us to monitor

remaining power life of battery-powered devices.

Such information, can be used to govern route stability.

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ABR: Summary

Advantages Stable routes have a higher preference compared to shorter routes.

Fewer path breaks

Reduce the extent of flooding due to reconfiguration of paths in the

network.

Disadvantage Chosen Path maybe longer than the shortest path between the source and

destination because of the preference given to stable paths.

Local query (LQ) broadcast may result in high delays during route repairs .

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5. Signal Stability Routing (SSR) Advance form of ABR

New metric: signal strength between nodes and a node’s location stability

Selects routes based on signal strength between nodes Prefers stronger connectivity.

Tables Signal Strength Table (SST)–

Periodic beacons from the link layer of the neighbouring nodes: fields [host, signal strength, last, clicks, set]

Signal strength recorded by SST-- Weak or Strong

Routing Table (RT)

field [destination, next host].

Two protocols

Dynamic Routing Protocol (DRP): manages SST & RT

Static Routing Protocol (SRP): forwards packets based on RT

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SSR (cont.)

Signal Stability Routing (SSR) SSR consists of 2 cooperative protocols: Dynamic Routing (DRP) Maintain signal stability table(SST) with and routing table(RT) After updating all appropriate table entries, the DRP passes a received packet to

the SRP

Static Routing (SRP) : Passing the packet up the stack if it is the intended receiver If no entry is found in the RT for the destination, initiate a route-search

process to find a route Else forwarding the packet Send a route reply message back to initiator

All transmission are received and processed by DRP

After processing and updating the table DRP passes the packets to SRP

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SSR (cont.)

Route discovery and route maintenance

By default, only route request packets from strong channels are forwarded

initiate a new route-search process; erase the old route

If there is no route-reply message received, the route changes to accept

weak channel.

A

B

C

D

E

F A

B

C

D

E

F

SSR ( route search) Passes the packets to the stack or look for destination in RT

If no entry is in RT for destination a new route search process is initiated.

Weak channels are accepted only if timed out occur for receiving a route

reply message.

In case of link failure intermediate nodes send error message to the source

indicating the broken channel and a new route search process is initialized

Assumptions:

Route search packets arrives at destination along the strongest signal

capability

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S

D

Weak link

route search

route reply

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SSR: Summary

Advantages To select strong connection leads to fewer route reconstruction

More stable route as compared to shortest path route selection

protocols such as AODV and DSR.

Disadvantage Long delay since intermediate nodes can’t answer the path (unlike AODV, DSR)

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6. Location-Aided Routing (LAR)

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Exploits location information to limit scope of flooding for route request

Limit the search for a new route to a smaller request zone.

Reduce the signalling traffic

Location information may be obtained using GPS

Two concept:

Expected zone

Request zone

Assumption:

Sender has advanced knowledge about location and velocity of the

destination

6. Location-Aided Routing (LAR)

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Location-Aided Routing (LAR) Expected zone:

determined as a region that is expected to hold the current

location of the destination node (D)

Determination is based on potentially old location information,

and knowledge of the destination’s speed

Request Zone :

Smallest rectangle that include the location of sender and

expected zone.

The sender explicitly defines the request zone ( co-ordinates of

the rectangular request zone)

The nodes can discard a route request packet if it is not under

the request zone.

Route requests limited to a Request Zone that contains

the Expected Zone and location of the sender node (S)71

Location-Aided Routing (LAR)

Expected Zone in LAR Request Zone in LAR

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Operation of LAR

Only nodes within the request zone forward route requests

Node A does not forward RREQ, but node B does

Request zone explicitly specified in the route request

Each node must know its physical location to determine whether it is within the

request zone

If route discovery using the smaller request zone fails to find a route, the

sender initiates another route discovery (after a timeout) using a larger

request zone

the larger request zone may be the entire network

Rest of route discovery protocol similar to DSR

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Operation of LAR When Destination node (D) receives the route request message, it

replies by sending a route reply message (as in the flooding

algorithm).

Node D includes its current location and current time in the route

reply message.

When node S receives this route reply message (ending its route discovery), it

records the location of node D.

Node S can use this information to determine the request zone for a future

route discovery.

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LAR: Summary

Advantages

Limit the search for a new route to a smaller request zone.

Reduces the scope of route request flood

Reduce the signaling traffic

Reduces overhead of route discovery

Disadvantage

Nodes need to know their physical locations

GPS is needed for pre-knowledge of the location of the destination

Positional error may affect routing

Does not take into account possible existence of obstructions for radio

transmissions75

7. Power –Aware Routing (PAR)

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Why POWER concerns ?

The lifetime of a network is defined as the time it takes for a fixed

percentage of the nodes in a network to die out.

Portability of wireless nodes being critical its almost mandatory to keep the

battery sizes to a bare necessary.

Since battery capacity is fixed, a wireless mobile node is

extremely energy constrained

Hence all network related transactions should be power aware to be able to

make efficient use of the overall energy resources of the network

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Metrics ( objectives)

Battery life is taken as routing metric

1. Minimize energy consumed / packet

2. Maximize time to Network Partition

3. Minimize variance in node power levels

4. Minimize cost / packet

5. Minimize maximum node cost

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Power-Aware Routing

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8. Zone Routing Protocol (ZRP)

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Hybrid protocol of reactive and proactive approach

Disadvantage of reactive:

reactive protocols have higher latency in discovering

routes.

Disadvantage of proactive:

proactive protocols generate a high volume of control

messages required for updating local routing tables.

ZRP:

The proactive part of the protocol is restricted to a small neighbourhoodof a node and the reactive part is used for routing across the network.

This reduces latency in route discovery and reduces the numberof control messages as well.

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ZRP: Zone routing protocol Hybrid of table-driven and on-demand!!

From each node, there is a concept of “zone”. Within each zone, the routing is performed in a table-driven manner

(proactive), similar to DSDV.

However, a node does not try to keep global routing information.

For inter-zone routing, on-demand routing is used. This is similar to DSR.

Zone routing protocol A routing zone :

Comprises a few mobile ad hoc nodes within one, two, or more hops

away from where the central node is formed.

Zones can overlap.

Each node specifies a zone radius in terms of radio hops.

Similar to a cluster with the exception that every node acts as a cluster

head and a member of other clusters.

Within this zone, a table-driven-based routing protocol is used.

Each node, therefore, has a route to all other nodes within the zone.

If the destination node resides outside the source zone, an on-

demand search-query routing method is used.

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Zone routing protocol

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ZRP

ZRP has three sub-protocols: the proactive (table-driven) Intrazone Routing Protocol

(IARP),

the reactive Interzone Routing Protocol (IERP), and

the Bordercast Resolution Protocol (BRP).

a) Intrazone Routing Protocol (IARP)

the proactive (table-driven) approach

IARP can be implemented using existing link-state or distance-vector

routing.

ZRP's IARP relies on an underlying neighbor discovery protocol to

detect the presence and absence of neighboring nodes

Ensure that each node within the zone has a consistent routing table to

reflect up-to-date information85

ZRPb) Reactive Interzone Routing Protocol (IERP), and Relies on border nodes to perform on-demand routing to search for routing

information to nodes residing outside its current zone.

IERP uses the bordercast resolution protocol.

c) the Bordercast Resolution Protocol (BRP). Instead of allowing the query broadcast to penetrate into nodes within other zones,

the border nodes in other zones that receive this message will not propagate it

further.

Relies on border nodes to perform on-demand routing to search for routing

information to nodes residing outside its current zone.

Without proper query control, ZRP can actually perform worse than

standard flooding-based protocols

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ZRP

ZRP's route discovery process is, route table lookup and/or

interzone route query search.

When a route is broken due to node mobility,

if the source of the mobility is within the zone

it will be treated like a link change event and an event-driven route

updates used in proactive routing will inform all other nodes in the zone.

If the source of mobility is a result of the border node or other

zone nodes,

then route repair in the form of a route query search is performed, or in

the worst case, the source node is informed of route failure.

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9. Source Tree Adaptive Routing (STAR)

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Proactive routing protocol

Does not need routing updates

Does not attempts to maintain optimum path

Examines updating strategies used table driven routing approaches

like ORA

Each node maintains a source tree

Source tree is the set of links used by an ad hoc host in its preferred

path to destination

Aggregation is done on host adjacent links and the source trees of the

neighbours. Aggregation creates a partial topology graph

Each node runs route selection algorithm on its own source node tree to

derive a routing table which can specifies the successor to each

destination

Uses sequence numbers to validate link state updates (LSU)

A host accepts a LSU if the sequence number is higher than the

previous or there is no entry till.

Only changes to the validity of the tree are propagated.

Dijkstra’s shortest path algorithm is used to select routes.

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10. Reactive Distance Microdiversity Routing (RDMAR)

90

Estimates the distance between two nodes using the relative distance

estimation algorithm in radio hops.

It is a source initiated routing protocol

It limits the range of route searching in order to save the cost of flooding a

route request message into the entire wireless area.

It is assumed in RDMAR that all ad hoc mobile hosts are migrating at the

same fixed speed.

Route Discovery

Transmission of route discovery packets

If a current relative estimate is present then search flood is limited to

this distance

Destination node returns reply message over reverse path.

Reply message moves backward while intermediate nodes establish the

forward route hop-by-hop

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Route maintenance

The node that notifies a link breakage invokes localized route

discovery to find partial path to destination.

If link breakage location is closer to the sender then the route

failure message is sent to the source.

The intermediate nodes which have the routing information

regarding this linkage , must have to remove their entries from

the routing tables.

It is assumed that all links are bidirectional

It uses the shortest route as the routing metric.

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Summary

On-demand AODV DSR TORA ABR SSA

Overall complexity Medium Medium High High High

Overhead Low Medium Medium High High

Routing philosophy Flat Flat Flat Flat Flat

Loop-free Yes Yes Yes Yes Yes

Multicast capability Yes No No No No

Beaconing requirements No No No Yes yes

Multiple route support No Yes Yes No No

Routes maintained in Route table Route cache Route table Route table Route

table

Route reconfiguration

methodlogy

Erase route;

notify source

Erase route;

notify

source

Link

reversal;

route repair

Localized

broadcast

query

Erase

route;

notify

source

Routing metric Freshest and

shortest path

Shortest

path

Shortest

path

Associativity

and shortest

path and

others

Associati

vity and

widest

Comparisons of the characteristics of source-initiated on demand routing protocol

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Overview

Parameters On Demand Table Driven

Availability of Routing

Information

Available when needed Always available regardless of need

Routing Philosophy Flat Mostly Flat except for CGSR

Periodic route updates Not Required Yes

Coping with Mobility Using Localized route discovery in

ABR

Inform other nodes to achieve

consistent routing tables

Signaling Traffic Generated Grows with increasing mobility of

active nodes as in ABR

Greater than that of On Demand

Routing

QoS Support Few Can Support QoS Mainly Shortest Path as QoS Metric

Reference

1. Routing Protocols for Ad Hoc Mobile Wireless Networt by Padmini Misra, ftp://ftp.netlab.ohio-state.edu/pub/jain/courses/cis788-99/adhoc_routing/index.html#CBRP

2. A Comparison of On-Demand and Table Driven Routing for Ad-Hoc Wireless Networks, by Jyoti Raju and J.J. Garcia-Luna-Aceves, http://www.soe.ucsc.edu/~jyoti/paper2/

3. A New Routing Protocol for the Reconfigurable Wireless Networks, Zygmunt J Hass

4. Caching strategies in on-demand routing protocols for wireless ad hoc networks, by Yih-chun hu and Divid B. Johnson, http://monarch.cs.cmu.edu

5. Highly Dynamic Destination-Sequenced Distance-Vector Routing for Mobile Computers, Pravin Bhagwat, Charles E. Perkins

6. Dynamic source routing in ad hoc wireless networks, by David B. Johnson and David A. Maltz, http://www1.ics.uci.edu/~atm/adhoc/paper-collection/johnson-dsr.pdf

7. A Performace Comparison of Multi-Hop Wireless Ad Hoc Network Routing Protocols, Josh Broch etc

8. An Efficient Routing Protocol for Wireless Netwrok, Shree Murthy etc

9. Temporally-Ordered Routing Algorithm (TORA) Version 1 Funtional Specification, by V. Park, S. Corson, http://www1.ics.uci.edu/~atm/adhoc/paper-collection/corson-draft-ietf-manet-tora-spec-00.txt

10. Ad Hoc On Demand Distance Vector (AODV) Routing, by Charles Perkins, http://www1.ics.uci.edu/~atm/adhoc/paper-collection/perkins-draft-ietf-manet-aodv-00.txt95

Reference (cont.)7. An Introduction to Mobile Ad Hoc Network, by Ming Yu Jiang,

http://kiki.ee.ntu.edu.tw/mmnet1/adhoc/

8. Scalable Routing Strategies for Ad hoc Wireless Network, by Atsushi Iwata , Ching-Chuan Chiang etc.

9. A Performance Comparison of Multi-Hop Wireless Ad Hoc Network Routing Protocols, by Josh Broch, David A. Maltz, David B. Johnson, Yih-Chun Hu, Jorjeta Jetcheva, http://www1.ics.uci.edu/~atm/adhoc/paper-collection/johnson-performance-comparison-mobicom98.pdf

10. Fisheye State Routing: A Routing Schema for Ad Hoc Wireless Networks, by guangyu Pei, Mario Gerla, Tsi-Wei Chen

11. A review of current Routing protocols for ad-hoc Mobile Wireless Networks, by Elizabeth M. Royer and C-K Tohhttp://www.cs.ucsb.edu/~vigna/courses/CS595_Fall01/royer99review.pdf

12. CEDAR: a Core-Extraction distributed Ad Hoc Routing Algorithm, Prasun Sinha, Vaduvur Nharghavan, etc

13. Mobile computing today & in the future, by M.J. Fahham and M.K. Hauge. http://www.doc.ic.ac.uk/~nd/surprise_95/journal/vol4/mjf/report.html

14. Performance Comparison of On-demand Routing Protocols in Ad Hoc Network by Sohela Kaniz http://fiddle.visc.vt.edu/courses/ecpe6504-wireless/projects_spring2000/pres_kaniz.pdf

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