1. Lecture (11-14) ---
On-Demand-Driven
Reactive Routing protocols
Chandra Prakash
Assistant Professor
LPU

2. Ad Hoc Routing Protocol
 Routing protocols category :
(a)Table-driven,
(b) Source-initiated on-demand-driven.
2

3. 3
Overview of Current Routing
Protocols

4. 4
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

5. 5
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

6. 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.
6

7. 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.
7

8. 8
Source-initiated on-demand
1. Dynamic Source Routing (DSR)
 D. B. Johnson and D.A. Maltz,“Dynamic Source Routing inAd-HocWireless 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 DistanceVector Routing,” Proc. 2nd
IEEEWksp. Mobile Comp. Sys. andApps., Feb. 1999, pp. 90–100.
3. Temporally ordered routing algorithm (TORA)
 V. D. Park and M. S. Corson,“A HighlyAdaptive Distributed RoutingAlgorithm for
MobileWireless Networks,” Proc. INFOCOM ’97,Apr. 1997.
4. Associativity-Based routing (ABR)
 C-K.Toh,“A Novel Distributed Routing ProtocolTo SupportAd-Hoc Mobile Computing,”
Proc. 1996 IEEE 15thAnnual Int’l. Phoenix Conf. Comp. and Commun., Mar. 1996, pp.
480–86.
5. Signal stability routing (SSR)
 R. Dube et al.,“Signal Stability basedAdaptive Routing (SSA) forAd-Hoc Mobile
Networks,” IEEE Pers. Commun., Feb. 1997, pp. 36–45.

9. 1. Dynamic Source Routing (DSR)
D. B. Johnson and D.A. Maltz,“Dynamic Source Routing inAd-HocWireless 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)
9

10. 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
10

11. 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.
11

12. 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.
12

13. Route Discovery in DSR
13
B
A
S E
F
H
J
D
C
G
I
K
Z
Y
Represents a node that has received RREQ for D from S
M
N
L

14. Route Discovery in DSR
B
A
S E
F
H
J
D
C
G
I
K
Represents transmission of RREQ
Z
Y
Broadcast transmission
M
N
L
[S]
[X,Y] Represents list of identifiers appended to RREQ14

15. 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
L
[S,E]
[S,C]
15

16. 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
Z
Y
M
N
L
[S,C,G]
[S,E,F]
16

17. Route Discovery in DSR
17
B
A
S E
F
H
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]

18. Route Discovery in DSR
18
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
M
N
L
[S,E,F,J,M]

19. 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
19

20. Route Reply in DSR
20
B
A
S E
F
H
J
D
C
G
I
K
Z
Y
M
N
L
RREP [S,E,F,J,D]
Represents RREP control message

21. 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

22. Data Delivery in DSR
22
B
A
S E
F
H
J
D
C
G
I
K
Z
Y
M
N
L
DATA [S,E,F,J,D]
Packet header size grows with route length

23. 23
Dynamic Source Routing (DSR)
Routing discovery routing reply

24. 24
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

25. destination
source
1
6
5
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
25

26. DSR Overview
Advantages
 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 problem
26

27. 2. Ad Hoc On-Demand Distance Vector
Routing Protocol (AODV)
C. E. Perkins and E. M. Royer,“Ad-hoc On-Demand DistanceVector Routing,” Proc. 2nd IEEE
Wksp. Mobile Comp. Sys. andApps., 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,
 InAODV, 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
27

28. 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.
28

29. 29
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 maintenance
 The 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

30. Route Requests in AODV
30
B
A
S E
F
H
J
D
C
G
I
K
Z
Y
Represents a node that has received RREQ for D from S
M
N
L

31. 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) andTime 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

32. Route Requests in AODV
32
B
A
S E
F
H
J
D
C
G
I
K
Represents transmission of RREQ
Z
Y
Broadcast transmission
M
N
L

33. Route Requests in AODV
33
B
A
S E
F
H
J
D
C
G
I
K
Represents links on Reverse Path
Z
Y
M
N
L

34. Reverse Path Setup in AODV
34
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
Z
Y
M
N
L

35. Reverse Path Setup in AODV
35
B
A
S E
F
H
J
D
C
G
I
K
Z
Y
M
N
L

36. Reverse Path Setup in AODV
36
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 RREQ
M
N
L

37. Forward Path Setup in AODV
37
B
A
S E
F
H
J
D
C
G
I
K
Z
Y
M
N
L
Forward links are setup when RREP travels along
the reverse path
Represents a link on the forward path

38. 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.
38

39. 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 packet
was 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 from
which it first received the RREQ and so on.
 As the RREP is routed back along the reverse path, nodes along this path set up
forward route entries in their route tables that point to the node from which
the RREP came.
 A route timer is associated with each route entry, which causes the deletion of
the entry if it is not used within a specified lifetime.
 Because an RREP is forwarded along the path established by an RREQ, AODV
only supports the use of symmetric links.
39

40. 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
40

41. 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

42. 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

43. 3. Temporally Ordered Routing
Algorithm (TORA)
V. D. Park and M. S. Corson,“A HighlyAdaptive Distributed RoutingAlgorithm 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.
43

44. 44
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
D
F
G
B

45. 45
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 NetworkTime Protocol.
 Timing is an important factor forTORA 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

46. 46
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

47. 47
TORA
 Route creation of TORA
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
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)

48. 48
TORA
 Creation of route
C
A B
E
G (DEST)
F
H
D
QRY
QRY
QRY
UPD
QRY
QRY
UPD
UPD
UP
D
UPD UPD
UPD

49. a
f
e
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)
49
QRY
QRY
QRY
QRY
QRY
QRY

50. 50
TORA
 Route maintenance
C
A B
E
G (DEST)
F
H
D
UPD
X
UPD
UPD

51. 51
TORA

52. 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.
52

53. 4. ABR: Associativity-Based routing
C-K.Toh,“A Novel Distributed Routing ProtocolTo SupportAd-Hoc Mobile Computing,” Proc. 1996
IEEE 15thAnnual 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.
53

54. 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

55. 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.
55

56. 56
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

57. 57
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.

58. Temporal and spatial representation of associativity of a
mobile node with its neighbors.
58

59. Rule and Property of Associativity
59
 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.

60. 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.
60

61. 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 .
61

62. 62
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

63. 63
SSR (cont.)

64. 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
64

65. 65
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

66. 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
66

67. S
D
Weak link
route search
route reply
67

68. 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 (unlikeAODV, DSR)
68

69. 6. Location-Aided Routing (LAR)
69

70.  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)
70

71. 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

72. Location-Aided Routing (LAR)
 Expected Zone in LAR  Request Zone in LAR
72

73. Operation of LAR
 Only nodes within the request zone forward route requests
 NodeA 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
73

74. 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.
74

75. 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

76. 7. Power –Aware Routing (PAR)
76

77. 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
77

78. 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
78

79. Power-Aware Routing
79

80. 8. Zone Routing Protocol (ZRP)
80

81. 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 neighbourhood
of a node and the reactive part is used for routing across the network.
This reduces latency in route discovery and reduces the number
of control messages as well.
81

82. 82
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.

83. 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.
83

84. Zone routing protocol
84

85. 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 information
85

86. ZRP
b) 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
86

87. 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.
87

88. 9. SourceTree Adaptive Routing (STAR)
88

89. 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.
89

90. 10. Reactive Distance Microdiversity Routing (RDMAR)
90

91.  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
91

92. 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.
92

93. 93
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

94. 94
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
SignalingTraffic 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

95. 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

96. Reference (cont.)
7. An Introduction to Mobile Ad Hoc Network, by MingYu Jiang,
http://kiki.ee.ntu.edu.tw/mmnet1/adhoc/
8. Scalable Routing Strategies for Ad hocWireless Network, by Atsushi Iwata , Ching-
Chuan Chiang etc.
9. A Performance Comparison of Multi-HopWireless 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 HocWireless Networks, by guangyu
Pei, Mario Gerla,Tsi-Wei Chen
11. A review of current Routing protocols for ad-hoc MobileWireless Networks, by
Elizabeth M. Royer and C-KToh
http://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
96