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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.
2
3
Overview of Current Routing
Protocols
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
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.
6
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
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)
9
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
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
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
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
Route Discovery in DSR
B
A
S E
F
H
J
D
C
G
I
K
Represents transmission of RREQ
Z
YBroadcast transmission
M
N
L
[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
L
[S,E]
[S,C]
15
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
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]
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]
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
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
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
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
Dynamic Source Routing (DSR)
Routing discovery routing reply
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
destination
source1
65
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
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
27
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
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
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
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
32
B
A
S E
F
H
J
D
C
G
I
K
Represents transmission of RREQ
Z
YBroadcast transmission
M
N
L
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
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
Reverse Path Setup in AODV
35
B
A
S E
F
H
J
D
C
G
I
K
Z
Y
M
N
L
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
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
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
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.
39
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
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.
43
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
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
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
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
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)
49
QRY
QRY
QRY
QRY
QRY
QRY
50
TORA
Route maintenance
C
A B
E
G (DEST)
FH
D
UPD
X
UPD
UPD
51
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.
52
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.
53
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.
55
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
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.
58
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.
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
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
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
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
64
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
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
S
D
Weak link
route search
route reply
67
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)
68
6. Location-Aided Routing (LAR)
69
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
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
84
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)
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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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