wireless aodv protocol

Routing Protocols in MANET

Dr. Pradip M Jawandhiya,Professor & Head, Computer Engineering Department,

Jagadambha College of Engg. & Tech, Yavatmalpmjawandhiya@rediffmail.com (9763717428)

& Mangesh M Ghonge

Faculty, Department of Computer Science & Engineering,Jawaharlal Darda Institute of Engineering & Technology,

Yavatmal (Maharashtra)- 445001, India.mmghonge@gmail.com (9096449280)

Outline

AODV Protocol

DSR Protocol

DSDV Protocol

AODV Protocol for Mobile Ad Hoc

Networks

AODV Ad Hoc On Demand Distance Vector Routing

Protocol Reactive Protocol: discovers a route on demand. Nodes do not have to maintain routing

information. Route Discovery Route Maintenance Hello messages:

used to determine local connectivity. can reduce response time to routing requests. can trigger updates when necessary.

AODV – Route Discovery If a source needs a route to a destination for which it does

not already have a route in its cache: Source broadcasts Route Request (RREQ)

message for specified destination Intermediate node:

Returns a route reply packet (RREP) (if route information about destination in its cache), or

forwards the RREQ to its neighbors (if route information about destination not in its cache).

If cannot respond to RREQ, increments hop count, saves info to implement a reverse path set up, to use when sending reply (assumes bidirectional link…)

AODV – RREQ RREQ packet contains:

destination and source IP address, broadcast ID, source node’s sequence number and destination node’s sequence number.

Node 1 wants to send data packet to node 7. Node 6 knows a current route to node 7. Node 1 sends a RREQ packet to its neighbors.

Source_addr =1 dest_addr =7 broadcast_id = broadcast_id +1source_sequence_# =

source_sequence_# + 1dest_sequence_# = last

dest_sequence_# for node 7

Type Flag Resvd hopcnt

Broadcast_id

Dest_addr

Dest_sequence_#

Source_addr

Source_Sequence_#

AODV (RREQ)

Nodes 2 and 4 verify that this is a new RREQ (source_sequence_# is not stale) with respect to the reverse route to node 1.

Forward the RREQ, and increment hop_cnt in the RREQ packet. RREQ reaches node 6 from node 4, which knows a route to 7. Node 6 verify that the destination sequence number is less than or

equal to the destination sequence number it has recorded for node 7.

Nodes 3 and 5 will forward the RREQ packet to node 6, but it recognizes the packets as duplicates.

AODV (RREP) Node 6 has a route to destination. It sends a route reply

RREP to the neighbor that sent the RREQ packet. Intermediate nodes propagate RREP towards the source

using cached reverse route entries. Other RREP packets discarded unless, dest_seq_# is higher

than the pervious, or same but hop_cnt is smaller. Cached reverse routes timeout in nodes that do not see

RREP packet.

Type Flag prsz hopcnt

Dest_addr

Dest_sequence_#

Source_addr

lifetime

AODV (RREP)

Node 6 sends RREP to node 4 Source_addr=1, dest_addr=7, dest_sequence_# = maximum

(sequence no. stored for node 7, dest_sequence_# in RREQ), hop_cnt =1.

Node 4 finds out it is a new route reply and propagates the RREP packet to Node 1.

Dynamic Source Routing (DSR)

11

The Routing Problem

S

D

D´S´

The routing problem is to find a route from S to D when some or all of the nodes are mobile.

12

Dynamic Source Routing (DSR)

When node S wants to send a packet to node D, but does not know a route to D, node S initiates a route discovery

Source node S floods Route Request (RREQ)

Each node appends own identifier when forwarding RREQ

13

Route Discovery in DSR

B

A

E

F

H

J

D

C

G

IK

Z

Y

Represents a node that has received RREQ for D from S

M

N

L

S

14

Route Discovery in DSR

B

A

E

F

H

JC

G

IK

Represents transmission of RREQ

Z

YBroadcast transmission

M

N

L

[S]

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

S

D

15

Route Discovery in DSR

B

A

E

F

H

JC

G

IK

• Node H receives packet RREQ from two neighbors: potential for collision

Z

Y

M

N

L

[S,E]

[S,C]

S

D

16

Route Discovery in DSR

B

A

E

F

H

JC

G

IK

• 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]

S

D

17

Route Discovery in DSR

B

A

E

F

H

JC

G

IK

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]S

D

18

Route Discovery in DSR

B

A

E

F

H

JC

G

IK

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]S

D

19

Route Discovery in DSR

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

20

Route Reply in DSR

B

A

E

F

H

JC

G

IK

Z

Y

M

N

L

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

Represents RREP control message

S

D

21

Dynamic Source Routing (DSR)

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

When node S sends a data packet to D, the entire route is included in the packet header hence the name source routing

Intermediate nodes use the source route included in a packet to determine to whom a packet should be forwarded

22

Data Delivery in DSR

B

A

E

F

H

JC

G

IK

Z

Y

M

N

L

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

Packet header size grows with route length

S

D

Destination-Sequenced Distance-Vector (DSDV) Routing Proactive - based on Bellman – Ford

❒ Packets transmitted according to the routing table

❒ Each node maintains routing table with entry for

each node in the network

<dest_addr, dest_seqn#, next-hop, hop_count,

install_time>

❒ Each node maintains its own sequence number

❍ Updates at each change in neighborhood information

❍ Used for freedom from loops

❍ To distinguish stale routes from new ones

DSDV: Routing Update ❒ Each node periodically transmits updates to keep

table consistency

❍ Includes its own sequence number #, route table updates

<dest_addr, dest_seq#, hop-count>

❒ Nodes also send routing table updates for

important link changes (i.e. link breaks)

❒ When two routes to a destination received from

two different neighbors

❍ Choose the one with the greatest destination sequence

number

❍ If equal, choose the smallest hop-count

DSDV: Full Dump/IncrementalUpdates

❒ Routing table updates create lots of

control traffic

❒ DSDV addresses this problem by using two

types of routing update packets

1. Full Dumps

• Carry all routing table information (Several NPDUs)

• Transmitted relatively infrequently

2. Incremental Updates

• Carry only information changed since last full dump

• Fits within one network protocol data unit (NPDU)

• When updates can no longer fit in one NPDU, send

full dump

DSDV: Link Additions

DSDV: Link Breaks

DSDV: Link Breaks

DSDV: Link Additions

DSDV: Link Breaks

DSDV: Link Breaks

DSDV: Link Breaks